NIMP| Irina ZGURA, Author at NIMP

Expertize

· Measurements of transition temperature, density, and surface tension measurements.

· Studies on multifunctional textile materials.

· Modifications of photocatalytic properties by tuning the synthesis parameters of the oxide semiconductors thin films.

· Interactions of some simple molecules with the surface of oxide or metallic materials by in situ IR spectroscopy, UV-vis spectroscopy.

· Composite obtaining and their characterization by XRD.

· Investigation of the watering properties of coatings applicable in the medical field (Ti implants, Ag doped C-structures, thin Ti nitride films, textiles coated with ZnO thin films and nanoparticles.) and determination of the free energy of the deposited layers based on the Owens-Wendt method for two test fluids .

· Wet synthesis of ZnO and Ag composites obtained by ecological methods.

Honours and awards

Romanian Academy Prize in 2004: Prize "Stefan Procopiu” for the article: "Nematic-isotropic interfacial tension anisotropy of a calamitic lyotropic liquid cristal" published in Liquid Crystals 31, 325-332 (2004)

1st Prize at the VIth International Congress of Dental Medicine for Physicians and Young Mitrofan I.L., Mateiaş C.G., Pătraşcu I., Pîrvu D., Zgură I., Beica T. Students "STOMis” Iassy, 9 – 12 December 2010 for presenting the poster „The assessment of quality of impression materials through the investigation of hyrophilicity (an in vitro study)”

1st Prize at Preclinical Section – Posters , 8th European Dental Students Association Congress, Bucharest, 10 – 14 March 2010 for presenting the poster „The assessment of quality of impression materials through the investigation of hyrophilicity”Mitrofan I.L., Mateiaş C.G., Pătraşcu I., Pîrvu D., Beica T., Zgură I.

The Best poster for young people EMRS 2014 spring meeting-Comparative study on the deposition of polymeric coatings based on PCL/PLGA blends, G. Popescu-Pelin, E. Axente, F. Sima, I. Iordache, C. Nita, A. Visan, I. Zgura, O.L. Rasoaga, C.S. Breazu, A. Stanculescu, G. Socol, I.N. Mihailescu

Silver Medal at EUROINVENT 2014 for “Device and method for detection of the viral antigen - specific antibody interactions by determining the contact angle”, S. Frunza, T. Beica, I. Zgura, L. Frunza, A. Nuta, A. Sorescu, C. N. Zaharia, I. Bunea

Excellence Awards at EUROINVENT 2014 for “Device and method for detection of the viral antigen - specific antibody interactions by determining the contact angle”, S. Frunza, T. Beica, I. Zgura, L. Frunza, A. Nuta, A. Sorescu, C. N. Zaharia, I. Bunea

Training stage

September – October 2004 Training stage at the Institute for Advanced Chemistry (ACA) in Berlin. The training stage was made under the European project CONCORDE, on the subject: Infrared spectroscopy measurements and TGA / DSC.

Books

1. L. Frunza, I Zgura, V. F. Cotorobai, C. P. Ganea, S. Frunza, Laser Optofluidics in Fighting Multiple Drug Resistance /Microdroplets of laser irradiated drug solutions: surface tension and contact angle, Benthamscience, Edited By Mihail Lucian Pascu, pp. 227-256, 2017, ISBN:978-1-68108-499-2

2. L. Duta, A. C. Popescu, I. Zgura, N. Preda, I. N. Mihailescu, Chapter 8: Wettability of nanostructured surfaces in Wetting and Wettability, InTech – Rijeka, 2015, ISBN 978-953-51-2215-9

3. L. Duta, A. C. Popescu, I. Zgura, N. Preda, I. N. Mihailescu, Chapter 8: Wettability of nanostructured surfaces in Wetting and Wettability, InTech – Rijeka, 2015, ISBN 978-953-51-2215-9

4. N. Preda, M. Enculescu, I. Zgura, M. Socol, C. Florica, A. Evanghelidis, E. Matei, I. Enculescu, Chapter 5: Zinc Oxide and Polysaccharides: Promising Candidates for Functional Nanomaterials in Size Effects in Nanostructures – Basics and Applications, Springer - Verlag Berlin Heidelberg, 2014, ISBN 978-3-662-44478-8

Patents

T. Beica, S. Frunza, I. Zgura, R. Moldovan, A. Dinescu, Method, measurement cell and experimental setup for the determination of temperature dependence of optical birefringence of liquid crystals, Brevet RO 122061B1/28.11.2008

S. Frunza, T. Beica, I. Zgura, L. Frunza, A. Nuta, A. Sorescu, C.N. Zaharia, I. Bunea, Device and method for detection of the viral antigen - specific antibody interactions by determining the contact angle, Brevet RO 126242 B1/30.10.2013

Projects

1. Investigations of biocomposite materials with bio-medical applications by means of neutron scattering and complementary methods

Project Type: Dubna, Start Date: 2019-06-10 End Date: 2020-12-31

2. Obtaining and investigations of the new biocomposite materials with bio-medical applications by means of neutron scattering and complementary methods

Project Type: Dubna, Start Date: 2020-05-20 End Date: 2020-12-10

Publications

1. Surface species of the nematic mixture E7 obtained by electrochemical insertion of Li+ ions

Authors: Baibarac, M; Zgura, I; Ganea, CP; Frunza, L

Published: APR 2023, EUROPEAN PHYSICAL JOURNAL E, 46, 26, DOI: 10.1140/epje/s10189-023-00280-z

We studied here the influence of Li+ ions on the benzene rings of nematic mixture E7, which is electrochemically adsorbed onto gold electrode surface, to highlight the ability of this mixture for the applications in the field of the rechargeable Li+-ion batteries. Raman spectra support the changes observed in electrochemical analyses while contact angle measurements show that wetting properties of E7 layer were modified after deposition of this mixture onto gold support and the doping with Li+ ions.

2. Burdock-Derived Composites Based on Biogenic Gold, Silver Chloride and Zinc Oxide Particles as Green Multifunctional Platforms for Biomedical Applications and Environmental Protection

Authors: Zgura, I; Badea, N; Enculescu, M; Maraloiu, VA; Ungureanu, C; Barbinta-Patrascu, ME

Published: FEB 2023, MATERIALS, 16, 1153, DOI: 10.3390/ma16031153

Green nanotechnology is a rapidly growing field linked to using the principles of green chemistry to design novel nanomaterials with great potential in environmental and health protection. In this work, metal and semiconducting particles (AuNPs, AgClNPs, ZnO, AuZnO, AgClZnO, and AuAgClZnO) were phytosynthesized through a "green" bottom-up approach, using burdock (Arctium lappa L.) aqueous extract. The morphological (SEM/TEM), structural (XRD, SAED), compositional (EDS), optical (UV-Vis absorption and FTIR spectroscopy), photocatalytic, and bio-properties of the prepared composites were analyzed. The particle size was determined by SEM/TEM and by DLS measurements. The phytoparticles presented high and moderate physical stability, evaluated by zeta potential measurements. The investigation of photocatalytic activity of these composites, using Rhodamine B solutions' degradation under solar light irradiation in the presence of prepared powders, showed different degradation efficiencies. Bioevaluation of the obtained composites revealed the antioxidant and antibacterial properties. The tricomponent system AuAgClZnO showed the best antioxidant activity for capturing ROS and ABTS center dot(+) radicals, and the best biocidal action against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The "green" developed composites can be considered potential adjuvants in biomedical (antioxidant or biocidal agents) or environmental (as antimicrobial agents and catalysts for degradation of water pollutants) applications.

3. Surface species of nematic mixture E7 in hard confinement: spectroscopic investigations cannot distinguish among the E7 components interacting with the support surface

Authors: Frunza, L; Zgura, I; Ganea, CP; Loiko, VA; Manaila-Maximean, D

Published: MAR 2023, LIQUID CRYSTALS, DOI: 10.1080/02678292.2023.2182379

Properties of surface species of the nematic mixture E7 in contact with inorganic oxides (especially those containing more or less aluminium ions) are in detail investigated by infrared spectroscopy and thermogravimetry. The absorption infrared peaks were decomposed into Gaussian components, the procedure allowing an easier comparison with the behaviour of related composites. We worked at enough small concentrations of the E7 relatively to support this ratio permitting the (partial) elimination of the species belonging to the bulk. Species put here in evidence are species that are hydrogen bonded to the surface of OH groups, molecules randomly oriented on the surface, some species bonded by involvement of pi electrons of the CN group to the aluminium ions, thus implying a strong interaction to the support. Supramolecular assemblies of E7 molecules are thus followed up.

4. Molecular dynamics of alkyl benzoate liquid crystals in the bulk state and in the surface layer of their composites with oxide nanopowders

Authors: Frunza, L; Zgura, I; Ganea, CP; Schonhals, A

Published: AUG 1 2022, JOURNAL OF MOLECULAR LIQUIDS, 359, 119374, DOI: 10.1016/j.molliq.2022.119374

This paper presents the results concerning monotropic nematic liquid crystals 4-pentylphenyl 40-alkyl benzoate (5PnB) (n = 3 or 5 carbon atoms in the alkyl chain). Their mesophase properties were supported by images of the polarized optical microscopy. Molecular dynamics in the bulk samples or in the composites prepared with aerosil A380 was investigated by broadband dielectric spectroscopy in a large temperature range, appropriately chosen. Thermo gravimetric and infrared investigations were additionally performed. The data were compared with those of structurally related nematics like cyanophenyl pentyl benzoates, which have a cyan group instead of the pentyl chain. The dielectric spectra of the bulk 3P5B and 5P5B demonstrate a dielectric behavior with several relaxation processes as expected for nematic liquid crystals. The temperature dependence of the relaxation rates (and of the dielectric strength) seems to have two distinguished regimes. Thus, in the isotropic state, at higher temperatures the data obey the Vogel-Fulcher-Tammann law, whereas an Arrhenius law is fitted at lower temperature, in a close similarity to the behavior of a constrained dynamic glass transition. Samples with a high density of silica (larger than 7 g aerosil/1 g of 5PnB) were prepared to observe a thin layer adsorbed on the particle surface; it was estimated that almost each guest 5PnB molecule interacts with the aerosil surface. For the composites only one main relaxation process is observed at frequencies much lower than those for the corresponding bulk, which was assigned to the dynamics of the molecules in the surface layer. Infrared spectroscopy shows that these molecules interact with the surface by the ester carbonyl group leading to the monolayer self-assembly at liquid-solid interface. We note once more the importance of the functional unit(s) for the interaction with the hydroxyl groups on the aerosil surface. (c) 2022 Elsevier B.V. All rights reserved.

5. New solutions for combatting implant bacterial infection based on silver nano-dispersed and gallium incorporated phosphate bioactive glass sputtered films: A preliminary study

Authors: Stuart, BW; Stan, GE; Popa, AC; Carrington, MJ; Zgura, I; Necsulescu, M; Grant, DM

Published: FEB 2022, BIOACTIVE MATERIALS, 8, DOI: 10.1016/j.bioactmat.2021.05.055

Ag/Ga were incorporated into resorbable orthopaedic phosphate bioactive glasses (PBG, containing P, Ca, Mg, Na, and Fe) thin films to demonstrate their potential to limit growth of Staphylococcus aureus and Escherichia coli in post-operative prosthetic implantation. Dual target consecutive co-sputtering was uniquely employed to produce a 46 nm Ag:PBG composite observed by high resolution TEM to consist of uniformly dispersed similar to 5 nm metallic Ag nano-particles in a glass matrix. Ga3+ was integrated into a phosphate glass preform target which was magnetron sputtered to film thicknesses of similar to 400 or 1400 nm. All coatings exhibited high surface energy of 75.4-77.3 mN/m, attributed to the presence of hydrolytic P-O-P structural surface bonds. Degradation profiles obtained in deionized water, nutrient broth and cell culture medium showed varying ion release profiles, whereby Ga release was measured in 1400 nm coating by ICP-MS to be similar to 6, 27, and 4 ppm respectively, fully dissolving by 24 h. Solubility of Ag nanoparticles was only observed in nutrient broth (similar to 9 ppm by 24 h). Quantification of colony forming units after 24 h showed encouraging antibacterial efficacy towards both S. aureus (4-log reduction for Ag:PBG and 6-log reduction for Ga-PBG approximate to 1400 nm) and E. coli (5-log reduction for all physical vapour deposited layers) strains. Human Hs27 fibroblast and mesenchymal stem cell line in vitro tests indicated good cytocompatibility for all sputtered layers, with a marginal cell proliferation inertia in the case of the Ag:PBG composite thin film. The study therefore highlights the (i) significant manufacturing development via the controlled inclusion of metallic nanoparticles into a PBG glass matrix by dual consecutive target co-sputtering and (ii) potential of PBG resorbable thin-film structures to incorporate and release cytocompatible/antibacterial oxides. Both architectures showed prospective bio-functional performance for a future generation of endo-osseous implant-type coatings.

6. Novel Green Nanotechnologies Applied in Environmental Protection and Health

Authors: Barbinta-Patrascu, ME; Badea, N; Zgura, I

Published: AUG 2022, MATERIALS, 15, 5297, DOI: 10.3390/ma15155297

7. Composite Drug Delivery System Based on Amorphous Calcium Phosphate-Chitosan: An Efficient Antimicrobial Platform for Extended Release of Tetracycline

Authors: Visan, AI; Ristoscu, C; Popescu-Pelin, G; Sopronyi, M; Matei, CE; Socol, G; Chifiriuc, MC; Bleotu, C; Grossin, D; Brouillet, F; Le Grill, S; Bertrand, G; Zgura, I; Cristescu, R; Mihailescu, IN

Published: OCT 2021, PHARMACEUTICS, 13, DOI: 10.3390/pharmaceutics13101659

One major warning emerging during the first worldwide combat against healthcare-associated infections concerns the key role of the surface in the storage and transfer of the virus. Our study is based on the laser coating of surfaces with an inorganic/organic composite mixture of amorphous calcium phosphate-chitosan-tetracycline that is able to fight against infectious agents, but also capable of preserving its activity for a prolonged time, up to several days. The extended release in simulated fluids of the composite mixture containing the drug (tetracycline) was demonstrated by mass loss and UV-VIS investigations. The drug release profile from our composite coatings proceeds via two stages: an initial burst release (during the first hours), followed by a slower evolution active for the next 72 h, and probably more. Optimized coatings strongly inhibit the growth of tested bacteria (Enterococcus faecalis and Escherichia coli), while the drug incorporation has no impact on the in vitro composite's cytotoxicity, the coatings proving an excellent biocompatibility sustaining the normal development of MG63 bone-like cells. One may, therefore, consider that the proposed coatings' composition can open the prospective of a new generation of antimicrobial coatings for implants, but also for nosocomial and other large area contamination prevention.

8. Valorization of Gleditsia triacanthos Invasive Plant Cellulose Microfibers and Phenolic Compounds for Obtaining Multi-Functional Wound Dressings with Antimicrobial and Antioxidant Properties

Authors: Marinas, IC; Oprea, E; Geana, EI; Tutunaru, O; Pircalabioru, GG; Zgura, I; Chifiriuc, MC

Published: JAN 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, DOI: 10.3390/ijms22010033

Gleditsia triacanthos is an aggressive invasive species in Eastern Europe, producing a significant number of pods that could represent an inexhaustible resource of raw material for various applications. The aim of this study was to extract cellulose from the Gleditsia triacanthos pods, characterize it by spectrophotometric and UHPLC-DAD-ESI/MS analysis, and use it to fabricate a wound dressing that is multi-functionalized with phenolic compounds extracted from the leaves of the same species. The obtained cellulose microfibers (CM) were functionalized, lyophilized, and characterized by ATR-FTIR and SEM. The water absorption and retention capacity as well as the controlled release of phenolic compounds with antioxidant properties evaluated in temporal dynamics were also determined. The antimicrobial activity against reference and clinical multi-drug-resistant Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Candida albicans, and Candida parapsilosis strains occurred immediately after the contact with the tested materials and was maintained for 24 h for all tested microbial strains. In conclusion, the multi-functionalized cellulose microfibers (MFCM) obtained from the reproductive organs of an invasive species can represent a promising alternative for the development of functional wound dressings with antioxidant and antimicrobial activity, as well as being a scalable example for designing cost-effective, circular bio-economy approaches to combat the accelerated spread of invasive species.

9. BIOPHYSICAL ASPECTS OF BIO-NANOSILVER GENERATED FROM URTICA DIOICA LEAVES AND VITIS VINIFERA FRUITS' EXTRACTS

Authors: Barbinta-Patrascu, ME; Nichita, C; Badea, N; Ungureanu, C; Bacalum, M; Zgura, I; Iosif, L; Antohe, S

Published: 2021, ROMANIAN REPORTS IN PHYSICS, 73, DOI:

Green chemistry principles were used to phytosynthesis of three types of silver nanoparticles (AgNPs) from aqueous extracts of: nettle (Urtica dioica) leaves, black grapes (Vitis vinifera fruits), and their mixture. The combination of these extracts proved to be the most potent bioreductant for Ag+, as compared to each extract alone. UV-Vis absorption and FT-IR spectroscopy proved the formation of silver nanoparticles. Total polyphenols' quantification of vegetal extracts and "green" AgNPs was carried out by Folin-Ciocalteu analysis. Structural (XRD) analysis revealed crystalline nature of bio-developed AgNPs. Morphological studies (AFM) showed spherical shape and the nano-scale dimensions of the obtained metallic nanoparticles. Physical stability of "green" developed nanoparticles was estimated by zeta potential measurements, and their biological activity was checked by evaluating the antimicrobial and the antioxidant potency. AgNPs phyto-generated from a combination of two extracts (nettle and grapes) proved to be the most bio-active, combining in a synergistic manner, the properties of nettle and grapes. These nanoparticles exhibited high antioxidant activity (AA = 89.4%) evaluated through chemiluminescence method, and strong antibacterial effect (showing an inhibition zone diameter of 20 mm) against Escherichia coli.

10. The Influence of the Ceramic Nanoparticles on the Thermoplastic Polymers Matrix: Their Structural, Optical, and Conductive Properties

Authors: Smaranda, I; Nila, A; Ganea, P; Daescu, M; Zgura, I; Ciobanu, RC; Trandabat, A; Baibarac, M

Published: AUG 2021, POLYMERS, 13, DOI: 10.3390/polym13162773

This paper prepared composites under the free membranes form that are based on thermoplastic polymers of the type of polyurethane (TPU) and polyolefin (TPO), which are blended in the weight ratio of 2:1, and ceramic nanoparticles (CNs) such as BaSrTiO3 and SrTiO3. The structural, optical, and conductive properties of these new composite materials are reported. The X-ray diffraction studies highlight a cubic crystalline structure of these CNs. The main variations in the vibrational properties of the TPU:TPO blend induced by CNs consist of the following: (i) the increase in the intensity of the Raman line of 1616 cm(-1); (ii) the down-shift of the IR band from 800 to 791 cm(-1); (iii) the change of the ratio between the absorbance of IR bands localized in the spectral range 950-1200 cm(-1); and (iv) the decrease in the absorbance of the IR band from 1221 cm(-1). All these variations were correlated with a preferential adsorption of thermoplastic polymers on the CNs surface. A photoluminescence (PL) quenching process of thermoplastic polymers is demonstrated to occur in the presence of CNs. The anisotropic PL measurements have highlighted a change in the angle of the binding of the TPU:TPO blend, which varies from 23.7 degrees to approximate to 49.3 degrees and approximate to 53.4 degrees, when the concentration of BaSrTiO3 and SrTiO3 CNs, respectively, is changed from 0 to 25 wt. %. Using dielectric spectroscopy, two mechanisms are invoked to take place in the case of the composites based on TPU:TPO blends and CNs, i.e., one regarding the type of the electrical conduction and another specifying the dielectric-dipolar relaxation processes.

11. Mixture of Graphene Oxide/Phosphoric Acid/Melamine as Coating for Improved Fire Protective Performance and Enhancement of Surface Electrical Properties on Wood Chipboard

Authors: Cotet, LC; Cadar, C; Mihis, A; Magyari, K; Muresan-Pop, M; Pop, LC; Mihaila, A; Szekely, I; Dragan, S; Dudescu, M; Zgura, I; Matei, E; Baia, M; Baibarac, M; Anghel, I; Baia, L

Published: APR 2021, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 21, DOI: 10.1166/jnn.2021.18959

Looking for multifunctional materials, an assessment of the performances both as fire retardant and generator of electrically conductive surfaces for a three component mixture of graphene oxide, phosphoric acid and melamine applied on wood chipboard was performed. A simple approach was used to investigate the intumescent char formation and quantify the loss mass during vertical burning tests, in which the prepared samples were exposed for a certain time interval to a flame generated by an ethanol lamp in ambient conditions. Moreover, mass loss evolution and structural changes that occur during the burning process were more comprehensive investigated by differential thermal and thermogravimetric (DTA/TGA) techniques. By comparing the performances between the wood chipboard samples without any coverage and those covered with one or multiple component mixture, an increase of protection against the fire action was noticed when the three component mixture was used. Also, an improvement of the electrical properties was observed, after flame exposure of the samples covered with multiple layers (i.e., two and three), when the three component mixture was used. Morphological and structural investigations by microscopy (optical and electronic-SEMEDX), X-ray diffraction (XRD) and spectral (Raman, FTIR) methods are described. An assessment of market potential is also discussed.

12. Alternative lignopolymer-based composites useful as enhanced functionalized support for enzymes immobilization

Authors: Lite, C; Ion, S; Tudorache, M; Zgura, I; Galca, AC; Enache, M; Maria, GM; Parvulescu, VI

Published: NOV 1 2021, CATALYSIS TODAY, 379, 229, DOI: 10.1016/j.cattod.2020.05.060

Amino-derivatized lignocomposite (ADL-composite) has been designed as an artificial lignin polymer (P1) of monolignol (coniferyl alcohol, CA) enhanced by aniline insertion (P2). The derivatized lignopolymeric (P2) layer covered the surface of a methacrylate particles (SC2/SC6) functionalized previously with amino phenolic crosslinker (p-phenylenediamine (p-Ph-2-NH2) or p-amino-2-hydroxybenzoic acid (p-NH2-SalA)). One-pot biocatalytic approach allowed to combine the preparation of the polymeric materials and also its attachment on the particles surface. Thus, the monolignol (CA) will be oxi-copolymerized together with aniline on the amino prefunctionalized support surface. The oxidation process was performed using H2O2 reagent and catalyzed by peroxidase enzyme (horseradish peroxidase, HRP). The biocatalytic process was evaluated in term of aromatic monomers (CA and aniline) conversion. The chemical structure and properties of the resulted ADL-composites were investigated using specific techniques (e.g. FTIR, TPD, TGA, static contact angle, elemental analysis, and gel permeation chromatography). Attachment of P1/P2 polymer on the particles improved the hydrophobicity and also the basicity of the composite surface. Lipase enzyme was immobilized on the ADL-composites for testing the applicability of ADL-composites for biocatalyst preparation. SEM analysis allowed to notice the modification of ADL-composites surface after enzyme immobilization. Immobilized lipase exhibited better activity compared with free lipase demonstrating the efficiency of ADL-composite as support for enzyme immobilization.

13. Cytotoxicity, Antioxidant, Antibacterial, and Photocatalytic Activities of ZnO-CdS Powders (vol 13, 182, 2020)

Authors: Zgura, I; Preda, N; Enculescu, M; Diamandescu, L; Negrila, C; Bacalum, M; Ungureanu, C; Barbinta-Patrascu, ME

Published: DEC 2021, MATERIALS, 14, DOI: 10.3390/ma14247713

14. Cytotoxicity, Antioxidant, Antibacterial, and Photocatalytic Activities of ZnO-CdS Powders

Authors: Zgura, I; Preda, N; Enculescu, M; Diamandescu, L; Negrila, C; Bacalum, M; Ungureanu, C; Barbinta-Patrascu, ME

Published: JAN 1 2020, MATERIALS, 13, DOI: 10.3390/ma13010182

In this work, ZnO-CdS composite powders synthesized by a simple chemical precipitation method were thoroughly characterized. The morphological, structural, compositional, photocatalytical, and biological properties of the prepared composites were investigated in comparison with those of the pristine components and correlated with the CdS concentration. ZnO-CdS composites contain flower-like structures, their size being tuned by the CdS amount added during the chemical synthesis. The photocatalytic activity of the composites was analyzed under UV irradiation using powders impregnated with methylene blue; the tests confirming that the presence of CdS along the ZnO in composites can improve the dye discoloration. The biological properties such as antioxidant capacity, antibacterial activity, and cytotoxicity of the ZnO, CdS, and ZnO-CdS composites were evaluated. Thus, the obtained composites presented medium antioxidant effect, biocidal activity against Escherichia coli, and no toxicity (at concentrations less than 0.05 mg/mL for composites with a low CdS amount) for human fibroblast cells. Based on these results, such composites can be used as photocatalytic and/or biocidal additives for photoactive coatings, paints, or epoxy floors, which in their turn can provide a cleaner and healthier environment.

15. Simple and clean method for obtaining Sn nanoparticles for hydrophobic coatings

Authors: Buruiana, AT; Sava, F; Matei, E; Zgura, I; Burdusel, M; Mihai, C; Velea, A

Published: NOV 1 2020, MATERIALS LETTERS, 278, DOI: 10.1016/j.matlet.2020.128419

Sn nanoparticles (NPs) are usually obtained by difficult chemical routes in several steps followed by thermal treatments. Here, a simple and clean method, to obtain Sn NPs directly on the substrate, is developed based on a vapor transport technique. The method is versatile, thus can be easily adjusted to obtain Sn NPs of different size, areal density and morphology, by controlling the deposition conditions. NPs are grown on Si/SiO2 substrate and characterized. Water contact angle measurements show that Sn nanoparticles increase the surface hydrophobicity by 20%. Thus, NPs cleanly obtained from a low-cost, earth-abundant, and environmentally friendly material, can be used to modulate the wettability of surfaces. (C) 2020 Elsevier B.V. All rights reserved.

16. Adsorption, wicking behavior and photodegradation tests of Rhodamine B solution upon wool substrates

Authors: Frunza, L; Cotorobai, VF; Enculescu, M; Zgura, I; Ganea, CP; Birzu, M; Manaila-Maximean, D

Published: 2020, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS AND NANOTECHNOLOGIES X, 11718, DOI: 10.1117/12.2572130

Behavior of some wool fabrics as such or functionalized with semiconductor nanoparticles against the photodegradation of Rhodamine B was investigated. The wool samples were commercially purchased, they were chosen to differ by the chemical nature of the yarns, by the size of the 2D texture elements and by the applied pretreatment. The samples were routinely characterized both in the original form and in the form coated with the oxide particles as well to consider the structure, the surface morphology and their changes due to dye deposition. Several techniques were routinely applied: optical microscopy, XRD, SEM, TGA, UV-Vis spectroscopy and FTIR-ATR. Data have shown that TiO2 layer has either an amorphous structure or is highly dispersed. Drops of Rhodamine B solution were deposited by sessile drop method. We have obtained optical images of the wet/colored spot during the radial wicking, collected with a usual camera. Image comparison was made by direct visualisation. The optical images of the spot on fabrics were taken immediately after the dye was applied, after the fabric was dried and afterwards, after the system illumination by UV-vis light as function of the time. The obtained final spots speak about the dye photodegradation in the studied cases.

17. Performant Composite Materials Based on Oxide Semiconductors and Metallic Nanoparticles Generated from Cloves and Mandarin Peel Extracts

Authors: Zgura, I; Enculescu, M; Istrate, C; Negrea, R; Bacalum, M; Nedelcu, L; Barbinta-Patrascu, ME

Published: NOV 2020, NANOMATERIALS, 10, DOI: 10.3390/nano10112146

In this work, the metal and semiconducting nanoparticles (AgNPs, ZnONPs and AgZnONPs) were phyto-synthesized using aqueous vegetal extracts from: Caryophyllus aromaticus L. (cloves) and Citrus reticulata L. (mandarin) peels. The morphological, structural, compositional, optical and biological properties (antibacterial activity, and cytotoxicity) of the prepared composites were investigated. The most effective sample proved to be AgZnONPs, derived from cloves, with a minimum inhibitory concentration (MIC) value of 0.11 mg/mL and a minimum bactericidal concentration (MBC) value of 2.68 mg/mL. All the other three composites inhibited bacterial growth at a concentration between 0.25 mg/mL and 0.37 mg/mL, with a bactericidal concentration between 3 mg/mL and 4 mg/mL. The obtained composites presented biocidal activity against Staphylococcus aureus, and biocompatibility (on human fibroblast BJ cells) and did not damage the human red blood cells. Additionally, an important result is that the presence of silver in composite materials improved the bactericidal action of these nanomaterials against the most common nosocomial pathogen, Staphylococcus aureus.

18. Novel Ecogenic Plasmonic Biohybrids as Multifunctional Bioactive Coatings

Authors: Barbinta-Patrascu, ME; Ungureanu, C; Badea, N; Bacalum, M; Lazea-Stoyanova, A; Zgura, I; Negrila, C; Enculescu, M; Burnei, C

Published: JUL 2020, COATINGS, 10, DOI: 10.3390/coatings10070659

The objective of the present study is the valorization of natural resources and the recycling of vegetal wastes by converting them into novel plasmonic bio-active hybrids. Thus, a "green" approach was used to design pectin-coated bio-nanosilver. Silver nanoparticles were generated from two common garden herbs (Mentha piperitaandAmaranthus retroflexus), and pectin was extracted from lemon peels. The samples were characterized by the following methods: Ultraviolet-visible (UV-Vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), dynamic light scattering (DLS), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM)-Energy-dispersive X-ray Spectroscopy (EDX), and zeta potential measurements. Microscopic investigations revealed the spherical shape and the nano-scale size of the prepared biohybrids. Their bioperformances were checked in terms of antioxidant and antibacterial activity. The developed plasmonic materials exhibited a strong ability to scavenge short-life (96.1% divided by 98.7%) and long-life (39.1% divided by 91%) free radicals. Microbiological analyses demonstrated an impressive antibacterial effectiveness of pectin-based hybrids againstEscherichia coli. The results are promising, and the obtained biomaterials could be used in many bio-applications, especially as antioxidant and antimicrobial biocoatings.

19. Molecular dynamics in bulk and surface species of cyanophenyl alkyl benzoates with 2, 3 and 7 carbon atoms in the alkyl chain: comparison in the whole homologous series

Authors: Frunza, S; Ganea, CP; Zgura, I; Frunza, L; Schonhals, A

Published: MAY 2 2020, LIQUID CRYSTALS, 47, 917, DOI: 10.1080/02678292.2019.1687768

Molecular mobility of cyanophenyl alkylbenzoates (CPnBs) (n = 2, 3, 7 - number of carbon atoms in the alkyl chain) in the bulk and in composites with aerosil A380 is investigated by broadband dielectric spectroscopy, while thermal analysis and infrared spectroscopy were applied to characterise the molecular species. The work completes preliminary results obtained for the members with n = 4 ... 6. An interaction by hydrogen bonding, between aerosil surface - OH groups and - CN or ester groups of the CPnB molecules takes place. It slows down the relaxation process as observed for related composites in comparison to the pure materials. The existence of two types of bonding might be the reason that Vogel temperature for the relaxation process in the surface layer does not show the odd-even effect. Temperature dependence of the relaxation rates for composites shows a crossover behaviour from a high to a low temperature regime. Moreover, the temperature dependence of the dielectric strength is unusual. As the loading degree is similar, comparison of the dielectric, spectroscopic and thermal data obtained here and with the results obtained for the composites with n = 4 ... 6 can be directly done. Increasing the number of the members of the homologous series confirms and hardens the preliminary conclusions.

20. Long-Term Evaluation of Dip-Coated PCL-Blend-PEG Coatings in Simulated Conditions

Authors: Visan, AI; Popescu-Pelin, G; Gherasim, O; Mihailescu, A; Socol, M; Zgura, I; Chiritoiu, M; Sima, LE; Antohe, F; Ivan, L; Vranceanu, DM; Cotrut, CM; Cristescu, R; Socol, G

Published: MAR 2020, POLYMERS, 12, DOI: 10.3390/polym12030717

Our study focused on the long-term degradation under simulated conditions of coatings based on different compositions of polycaprolactone-polyethylene glycol blends (PCL-blend-PEG), fabricated for titanium implants by a dip-coating technique. The degradation behavior of polymeric coatings was evaluated by polymer mass loss measurements of the PCL-blend-PEG during immersion in SBF up to 16 weeks and correlated with those yielded from electrochemical experiments. The results are thoroughly supported by extensive compositional and surface analyses (FTIR, GIXRD, SEM, and wettability investigations). We found that the degradation behavior of PCL-blend-PEG coatings is governed by the properties of the main polymer constituents: the PEG solubilizes fast, immediately after the immersion, while the PCL degrades slowly over the whole period of time. Furthermore, the results evidence that the alteration of blend coatings is strongly enhanced by the increase in PEG content. The biological assessment unveiled the beneficial influence of PCL-blend-PEG coatings for the adhesion and spreading of both human-derived mesenchymal stem cells and endothelial cells.

21. The Beneficial Mechanical and Biological Outcomes of Thin Copper-Gallium Doped Silica-Rich Bio-Active Glass Implant-Type Coatings

Authors: Stan, GE; Tite, T; Popa, AC; Chirica, IM; Negrila, CC; Besleaga, C; Zgura, I; Sergentu, AC; Popescu-Pelin, G; Cristea, D; Ionescu, LE; Necsulescu, M; Fernandes, HR; Ferreira, JMF

Published: NOV 2020, COATINGS, 10, DOI: 10.3390/coatings10111119

Silica-based bioactive glasses (SBG) hold great promise as bio-functional coatings of metallic endo-osseous implants, due to their osteoproductive potential, and, in the case of designed formulations, suitable mechanical properties and antibacterial efficacy. In the framework of this study, the FastOs(R)BG alkali-free SBG system (mol%: SiO2-38.49, CaO-36.07, P2O5-5.61, MgO-19.24, CaF2-0.59), with CuO (2 mol%) and Ga2O3 (3 mol%) antimicrobial agents, partially substituting in the parent system CaO and MgO, respectively, was used as source material for the fabrication of intentionally silica-enriched implant-type thin coatings (similar to 600 nm) onto titanium (Ti) substrates by radio-frequency magnetron sputtering. The physico-chemical and mechanical characteristics, as well as the in vitro preliminary cytocompatibility and antibacterial performance of an alkali-free silica-rich bio-active glass coating designs was further explored. The films were smooth (R-RMS < 1 nm) and hydrophilic (water contact angle of similar to 65 degrees). The SBG coatings deposited from alkali-free copper-gallium co-doped FastOs(R)BG-derived exhibited improved wear performance, with the coatings eliciting a bonding strength value of similar to 53 MPa, Lc3 critical load value of similar to 4.9 N, hardness of similar to 6.1 GPa and an elastic modulus of similar to 127 GPa. The Cu and Ga co-doped SBG layers had excellent cytocompatibility, while reducing after 24 h the Staphylococcus aureus bacterial development with 4 orders of magnitude with respect to the control situations (i.e., nutritive broth and Ti substrate). Thereby, such SBG constructs could pave the road towards high-performance bio-functional coatings with excellent mechanical properties and enhanced biological features (e.g., by coupling cytocompatibility with antimicrobial properties), which are in great demand nowadays.

22. Laser Processed Antimicrobial Nanocomposite Based on Polyaniline Grafted Lignin Loaded with Gentamicin-Functionalized Magnetite

Authors: Visan, AI; Popescu-Pelin, G; Gherasim, O; Grumezescu, V; Socol, M; Zgura, I; Florica, C; Popescu, RC; Savu, D; Holban, AM; Cristescu, R; Matei, CE; Socol, G

Published: FEB 2019, POLYMERS, 11, DOI: 10.3390/polym11020283

Composite thin coatings of conductive polymer (polyaniline grafted lignin, PANI-LIG) embedded with aminoglycoside Gentamicin sulfate (GS) or magnetite nanoparticles loaded with GS (Fe3O4@GS) were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. The aim was to obtain such nanostructured coatings for titanium-based biomedical surfaces, which would induce multi-functional properties to implantable devices, such as the controlled release of the therapeutically active substance under the action of a magnetic and/or electric field. Thus, the unaltered laser transfer of the initial biomaterials was reported, and the deposited thin coatings exhibited an appropriate nanostructured surface, suitable for bone-related applications. The laser processing of PANI-LIG materials had a meaningful impact on the composites' wettability, since the contact angle values corresponding to the composite laser processed materials decreased in comparison with pristine conductive polymer coatings, indicating more hydrophilic surfaces. The corrosion resistant structures exhibited significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans strains. In vitro cytotoxicity studies demonstrated that the PANI-LIG-modified titanium substrates can allow growth of bone-like cells. These results encourage further assessment of this type of biomaterial for their application in controlled drug release at implantation sites by external activation.

23. Pd-Cu catalysts supported on anion exchange resin for the simultaneous catalytic reduction of nitrate ions and reductive dehalogenation of organochlorinated pollutants from water

Authors: Bradu, C; Capat, C; Papa, F; Frunza, L; Olaru, EA; Crini, G; Morin-Crini, N; Euvrard, E; Balint, I; Zgura, I; Munteanu, C

Published: JAN 25 2019, APPLIED CATALYSIS A-GENERAL, 570, 129, DOI: 10.1016/j.apcata.2018.11.002

The present work proposes the simultaneous removal of these classes of pollutants by a catalytic hydrotreatment processes. For this purpose, bimetallic Pd-Cu catalysts (with mass ratio Pd:Cu of 4:1) supported on macroporous strong base anion resin were prepared by different methods. The catalysts were characterized (by XRD, SEMEDX, XPS, AAS and H-2 chemisorption) and tested in a continuous flow system. The selected catalyst preparation protocol consists in a two-step method, which implies the deposition of palladium by ion exchange and the subsequent deposition of copper by controlled reaction on the surface of the pre-reduced palladium. The effectiveness of the catalyst in the simultaneous reduction of nitrate and hydrodechlorination of 4-chlorophenol was demonstrated. By adjusting the initial pH and the flow rate of the aqueous solution, nearly complete hydrodechlorination of 4-chlorophenol can occur together with selective nitrate reduction at a conversion of 95% and a selectivity to N-2 of 92% (this value contains the contribution of all gaseous products, including the eventually formed NOx). The bimetallic catalyst was found to remains relatively stable after 100 h of test time.

24. DENSITY OF ADSORBED SURFACE SPECIES FOR CYANOPHENYL ALKYL BENZOATES CONFINED TO AEROSIL A380: DEVELOPMENT OF THE EVALUATING ALGORITHM FOR ATTACHMENT BY TWO TYPES OF BONDS

Authors: Frunza, S; Frunza, L; Ganea, CP; Zgura, I; Schonhals, A

Published: 2019, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 81, 236, DOI:

We found previously how to estimate the density of the adsorbed surface species in the case of the molecules interacting to the oxide support surface by one type of bond. Here this algorithm is developed for the case of the molecules which can be bonded to the support surface by two types of bonds. The adsorption assumptions are similar to those considered in the case of only one type of bond. The calculation is exemplified for some composites of cyanophenyl alkylbenzoates (CPnBs) (n is the number of carbon atoms in the alkyl chain) interacting with Aerosil A380. The interaction takes place by hydrogen bonding between the -OH groups or the support and the functional groups of the CPnB molecules. The estimated values of the total surface density of CPnBs agree well with those found for the composites containing related but simpler molecules.

25. 3D hybrid structures based on biomimetic membranes and Caryophyllus aromaticus - "green" synthesized nano-silver with improved bioperformances

Authors: Barbinta-Patrascu, ME; Badea, N; Bacalum, M; Ungureanu, C; Suica-Bunghez, IR; Lordache, SM; Pirvu, C; Zgura, I; Maraloiu, VA

Published: AUG 2019, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 101, 137, DOI: 10.1016/j.msec.2019.03.069

The paper describes an innovative bio-design of some hybrid nanoarchitectures containing bioartificial membranes and silver nanoparticles phytogenerated by using a natural extract Caryophyllus aromaticus (cloves) that contains many bioactive compounds. Two kinds of liposomes with and without chlorophyll a (Chla) obtained through thin film hydration method were used to achieve bio-green-generated hybrids by a simple, cost effective bottom-up approach. The characteristic peaks of CE-nAg monitored by UV-Vis absorption have firstly demonstrated the biohybrids formation. The slightly blue shift and fluorescence quenching observed by fluorescence emission spectra highlighted the formation of hybrid systems by biointeraction between lipid vesicles and silver nanoparticles. The incorporation of silver nanoparticles in lipid vesicles resulted in significant changes of FT-IR spectra of liposomes, indicating a reorganization of biomimetic membranes. All the microscopic methods (SEM, AFM and TEM) confirmed the biosynthesis of "green" AgNPs together with associated biohybrids, their spherical and quasi-spherical shapes with nano-scaled size. By TEM assay it was shown that CE-nAg are surrounded by petal like cloud structures that consist of biopolymers like proteins or polysaccharides and other phytochemicals arising from clove extract. EDS spectra confirmed the formation of phyto-nanoAg and also the presence of silver in the biohybrids. In addition, Selected Area Electron Diffraction showed characteristic polycrystalline ring patterns for a cubic structure of the clove-generated AgNPs. The hybrid materials showed efficient physical stability, ie. xi value of - 28.0 mV (for biohybrids without Chla, BH) and of - 31.7 mV (for biohybrids labelled with Chla, Chla-BH), assured by strong electrostatic repulsive forces between particles. The "green" nano-silver particles (CE-nAg) showed remarkable antioxidant activity (AA = 90.2%). The biohybrids loaded with clove-AgNPs proved to be more effective, scavenging about 98.8% of free radicals (in case of ChlaBH), and of 92.6% (in case of BH). The antibacterial effectiveness showed that green AgNPs combine in a synergistic manner the antibacterial properties of clove extract with those of silver, resulting in an enhancement of inhibition diameter, by 20%. Chla-BH proved to be more potent against Escherichia coli, than BH, exhibiting an inhibition diameter of 42 mm. Regarding the in vitro cytotoxicity against tumour cells, the CE-nAg concentration significantly influenced the cell viability, ie. IC50 was 3.6% (v/v) for HT-29 cells. Chla-BH was more effective against HT-29 cancer cells at the concentrations ranging from 0 to 18% (v/v), when the normal cells were not affected. Clove-generated AgNPs exhibited haemolytic activity against hRBCs, while the biohybrids were haemocompatible. The action mechanism on the two cell lines (mouse fibroblast L929 cells and human colorectal adenocarcinoma HT-29 cells) investigated by fluorescence microscopy demonstrated that CE-nAg killed almost all the cells (94%) through necrosis at a concentration of 33.4% (v/v). The treatment of HT-29 cells with BH resulted in: 71.5% viable cells, 19.5% apoptotic and only 9% necrotic cells, while in the case of Chla-BH treatment, only 77.5% cells were viable, 16% cells were apoptotic and 6.5% were necrotic. In this way, the developed silver-based nanoparticles can represent viable promoters to develop new biohybrids with improved features, e.g. antioxidant and antibacterial effectiveness, haemolytic activity and greater specificity towards tumour cells.

26. Hierarchical functionalization of electrospun fibers by electrodeposition of zinc oxide nanostructures

Authors: Matei, E; Busuioc, C; Evanghelidis, A; Zgura, I; Enculescu, M; Beregoi, M; Enculescu, I

Published: NOV 15 2018, APPLIED SURFACE SCIENCE, 458, 563, DOI: 10.1016/j.apsusc.2018.06.143

Electrospun sub-micrometer polymer fiber mats represent an interesting substrate which can be employed as a transparent conducting electrode. Functionalization by using nanostructures represents a convenient way of increasing the range of applications. The present paper describes an electrodeposition process which can be applied for preparing ZnO nanostructures covered fibers in a straightforward manner. Poly(methyl methacrylate) fiber mats were obtained by electrospinning using metal frame collectors. Subsequent metallization by DC sputtering was used, these microstructured electrodes being thermally transferred onto glass substrates and further employed as working electrodes for the electrochemical deposition of ZnO. The transparency of the metal covered webs, a function of fiber density, is comparable to that of conventional transparent conductive oxides electrodes such as ITO. The same enhanced control of the ZnO electrodeposition process was observed for the case of the web electrodes as for the classic case of deposition on transparent conducting oxides or on metallic substrates. Structural, optical, morphological and wetting properties were investigated and correlated with the electrodeposition conditions. The photocatalytic properties of ZnO covered fibers were tested through the decomposition of methylene blue thin films under UV irradiation.

27. One-Pot Enzymatic Production of Lignin-Composites

Authors: Ion, S; Opris, C; Cojocaru, B; Tudorache, M; Zgura, I; Galca, AC; Bodescu, AM; Enache, M; Maria, GM; Parvulescu, VI

Published: APR 20 2018, FRONTIERS IN CHEMISTRY, 6, DOI: 10.3389/fchem.2018.00124

A novel and efficient one-pot system for green production of artificial lignin bio-composites has been developed. Monolignols such as sinapyl (SA) and coniferyl (CA) alcohols were linked together with caffeic acid (CafAc) affording a polymeric network similar with natural lignin. The interaction of the dissolved SA/CA with CafAc already bound on a solid support (S-C2/S-C6 CafAc) allowed the attachment of the polymeric product direct on the support surface (S-C2/S-C6-CafAc-L-1 and S-C2/S-C6-CafAc-L-2, from CA and SA, respectively). Accordingly, this procedure offers the advantage of a simultaneous polymer production and deposition. Chemically, oxi-copolymerization of phenolic derivatives (SA/CA and CAfAc) was performed with H2O2 as oxidation reagent using peroxidase enzyme (2-1B mutant of versatile peroxidase from Pleurotus eryngii) as catalyst. The system performance reached a maximum of conversion for SA and CA of 71.1 and 49.8%, respectively. The conversion is affected by the system polarity as resulted from the addition of a co-solvent (e.g., MeOH, EtOH, or THF). The chemical structure, morphology, and properties of the bio-composites surface were investigated using different techniques, e.g., FTIR, TPD-NH3, TGA, contact angle, and SEM. Thus, it was demonstrated that the SA monolignol favored bio-composites with a dense polymeric surface, high acidity, and low hydrophobicity, while CA allowed the production of thinner polymeric layers with high hydrophobicity.

28. Performant silver-based biohybrids generated from orange and grapefruit wastes

Authors: Barbinta-Patrascu, ME; Ungureanu, C; Suica-Bunghez, IR; Iordache, AM; Petrovic, SM; Ispas, A; Zgura, I

Published: SEP-OCT 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 557, DOI:

Clean technologies using the principles of green chemistry have attracted the attention of scientists in the last decade. Our work was focused on building advanced silver-based materials using an eco-friendly and convenient method. Two types of silver nanoparticles were synthesized using aqueous extracts of orange (Citrus sinensis) and grapefruit (Citrus paradisi) peels. Hybrid entities consisting of these bionanosilver particles and biomimetic membranes were "green" prepared and studied by spectral methods (UV-Vis absorption and emission, and FTIR-ATR spectroscopy). The morphology of silver-containing materials was analyzed by AFM images and their physical stability was checked by zeta potential measurements. Also, their antioxidant and antimicrobial properties were evaluated.

29. Wet chemical synthesis of ZnO-CdS composites and their photocatalytic activity

Authors: Zgura, I; Preda, N; Socol, G; Ghica, C; Ghica, D; Enculescu, M; Negut, I; Nedelcu, L; Frunza, L; Ganea, CP; Frunza, S

Published: MAR 2018, MATERIALS RESEARCH BULLETIN, 99, 181, DOI: 10.1016/j.materresbull.2017.11.013

The present study is focused on the wet chemical synthesis and the characterization of ZnO-CdS composites. The X-ray diffraction shows that the composites contain ZnO in hexagonal wurtzite structure and CdS in cubic phase. The scanning/transmission electron microscopy images reveal flower-like structures with different sizes depending on the CdS content. The optical investigations on composites reveal that the reflectance spectra disclose two thresholds of similar to 370 nm and similar to 460 nm associated with the ZnO and CdS, respectively. The photocatalytic activity measurements evidenced that the degradation efficiency of RhB in the presence of composites is higher comparatively with pristine ZnO, depending on the catalyst morphology, which varies with CdS content and the pH value of RhB solution. The electron paramagnetic resonance revealed the presence of the paramagnetic point defects in the samples. Thus, the wet chemical approaches are suitable for a large scale production of such ZnO-CdS composites having enhanced photocatalytic activity.

30. Physical-chemical characterization and biological assessment of simple and lithium-doped biological-derived hydroxyapatite thin films for a new generation of metallic implants

Authors: Popescu, AC; Florian, PE; Stan, GE; Popescu-Pelin, G; Zgura, I; Enculescu, M; Oktar, FN; Trusca, R; Sima, LE; Roseanu, A; Duta, L

Published: MAY 1 2018, APPLIED SURFACE SCIENCE, 439, 735, DOI: 10.1016/j.apsusc.2018.01.008

We report on the synthesis by PLD of simple and lithium-doped biological-origin hydroxyapatite (HA) films. The role of doping reagents (Li2CO3, Li3PO4) on the morphology, structure, chemical composition, bonding strength and cytocompatibility of the films was investigated. SEM investigations of the films evidenced a surface morphology consisting of particles with mean diameters of (5-7) mu m. GIXRD analyses demonstrated that the synthesized structures consisted of HA phase only, with different degrees of crystallinity, mainly influenced by the doping reagent type. After only three days of immersion in simulated body fluid, FTIR spectra showed a remarkable growth of a biomimetic apatitic film, indicative of a high biomineralization capacity of the coatings. EDS analyses revealed a quasi-stoichiometric target-to-substrate transfer, the values inferred for the Ca/P ratio corresponding to a biological apatite. All synthesized structures displayed a hydrophilic behavior, suitable for attachment of osteoblast cells. In vitro cell viability tests showed that the presence of Li2CO3 and Li3PO4 as doping reagents promoted the hMSC growth on film surfaces. Taking into consideration these enhanced characteristics, corroborated with a low fabrication cost generated by sustainable resources, one should consider the lithium-doped biological-derived materials as promising prospective solutions for a next generation of coated implants with rapid osteointegration. (C) 2018 Elsevier B.V. All rights reserved.

31. Photocatalytic activity of wool fabrics deposited at low temperature with ZnO or TiO2 nanoparticles: Methylene blue degradation as a test reaction

Authors: Frunza, L; Diamandescu, L; Zgura, I; Frunza, S; Ganea, CP; Negrila, CC; Enculescu, M; Birzu, M

Published: MAY 15 2018, CATALYSIS TODAY, 306, 259, DOI: 10.1016/j.cattod.2017.02.044

Different amounts of TiO2 and ZnO particles were deposited upon wool fabrics, which are among the less studied textiles. The materials were get from industry or were home made. Model samples for these oxide deposition and properties were also considered. Either sputtering or chemical sol-gel/electro less technique was respectively applied. The coated samples were then characterized structurally and morphologically, by XRD, SEM and XPS and were checked for photocatalytic properties. Both UV and vis light beams were used for irradiation. The photocatalytic experiments were performed by photodegradation of methylene blue in the PCC2 checker apparatus. The fabrics were firstly impregnated with the dye solution and then dried: self cleaning of the wool fabric samples took in fact place. Reflectance data in the visible spectral range of highest absorption band served for direct analysis of MB degradation. The photocatalytic properties of the coated fabrics increased much in comparison with the raw materials. The photocatalytic decolorization of methylene blue follows up a simple apparently first order kinetic equation in many studied cases. Thus it was demonstrated that MB decolorization can serve as a test reaction at least for self cleaning of fabrics. (C) 2017 Elsevier B.V. All rights reserved.

32. Lincomycin-embedded PANI-based coatings for biomedical applications

Authors: Popescu-Pelin, G; Fufa, O; Popescu, RC; Savu, D; Socol, M; Zgura, I; Holban, AM; Vasile, BS; Grumezescu, V; Socol, G

Published: OCT 15 2018, APPLIED SURFACE SCIENCE, 455, 666, DOI: 10.1016/j.apsusc.2018.06.016

We report on the successful laser transfer of biocompatible composite coatings based on polyaniline (PANI) embedded with magnetite (PANI-Fe3O4) and Lincomycin hydrochloride (PANI-Lincomycin) or Lincomycin-functionalized magnetite (PANI-Fe3O4@Lincomycin) by matrix assisted pulsed laser evaporation (MAPLE) technique. The physico-chemical investigations revealed relevant data regarding the stoichiometric deposition, morphology and topography of the as-deposited coatings. Regarding the MAPLE coatings, the FTIR studies evidenced the vibrational bands characteristic to pristine PANI material, while the SEM investigations unveiled a preferential particulate morphology (with aggregates shape and size depending on the deposited material). Additionally, the AFM measurements indicated variations of RMS value, following the Lincomycin and magnetite incorporation. The wettability measurements displayed a hydrophilic behavior of the synthesized coatings, while the electrochemical studies emphasized an enhanced resistance against corrosion in simulated body fluid when compared with bare Ti. Cellular viability, immunofluorescence and SEM results proved that the MAPLE coatings were suitable materials for beneficial adhesion, spreading and proliferation of osteoblast-like cells (MG-63). Moreover, an increased efficiency was evidenced against Staphylococcus aureus biofilm development. The multifunctional properties of the laser processed composite coatings - confirmed by cumulative biocompatible, antimicrobial and anticorrosive behaviors - recommend them as promising solutions for biomedical applications.

33. Biocomposite coatings based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/calcium phosphates obtained by MAPLE for bone tissue engineering

Authors: Rasoga, O; Sima, L; Chiritoiu, M; Popescu-Pelin, G; Fufa, O; Grumezescu, V; Socol, M; Stanculescu, A; Zgura, I; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 212, DOI: 10.1016/j.apsusc.2017.01.205

The aim of our research was to synthesize and investigate the physico-chemical and biological features of composite coatings based on poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and commercial calcium phosphates (CaPs), hydroxyapatite and beta-tricalcium phosphate, obtained by means of matrix assisted pulsed laser evaporation (MAPLE) technique. In this respect, laser fluence and dropcast studies were performed for pristine polymer and PHBV-CaPs composites. The microstructure of the synthesized coatings was investigated by scanning electron microscopy, while for the chemical structure and functional integrity we performed Fourier transform infrared spectroscopy comparative analysis. By using the X-ray diffraction measurements we experimentally evaluated the crystalline nature of the obtained composite materials, while relevant data regarding the hydrophilic/hydrophobic behavior of the synthesized coatings were obtained by performing static CA measurements. The biocompatibility of PHBV/CaPs coatings was evaluated by performing cellular adhesion and differentiation in vitro assays on mesenchymal stem cells. (C) 2017 Elsevier B.V. All rights reserved.

34. Optimized silicon reinforcement of carbon coatings by pulsed laser technique for superior functional biomedical surfaces fabrication

Authors: Mihailescu, IN; Bociaga, D; Popescu-Pelin, G; Stan, GE; Duta, L; Socol, G; Chifiriuc, MC; Bleotu, C; Lazar, V; Husanu, MA; Zgura, I; Miculescu, F; Negut, I; Hapenciuc, C

Published: JUN 1 2017, BIOFABRICATION, 9, DOI: 10.1088/1758-5090/aa7076

We report on the fabrication of silicon-reinforced carbon (C: Si) structures by combinatorial pulsed laser deposition to search for the best design for a new generation of multi-functional coated implants. The synthesized films were characterized from the morphological, structural, compositional, mechanical and microbiological points of view. Scanning electron microscopy revealed the presence, on top of the deposited layers, of spheroid particulates with sizes in the micron range. No microcracks or delaminations were observed. Energy dispersive x-ray spectroscopy and grazing incidence x-ray diffraction pointed to the existence of aC to Si compositional gradient from one end of the film to the other. Raman investigation revealed a relatively high sp(3) hybridization of up to 80% at 40-48 mm a part from the edge with higher Ccontent. Si addition was demonstrated to significantly increase C: Si film bonding to the substrate, with values above the ISO threshold for coatings to be used in high-loading biomedical applications. Surface energy studies pointed to an increase in the hydrophilic character of the deposited structures along with Si content up to 52 m Nm(-1'). In certain cases, the Si-reinforced Ccoatings elicited an antimicrobial biofilm action. The presence of Si was proven to be benign to HEp-2 cells of human origin, without interfering with their cellular cycle. On this basis, reliable C: Si structures with good adherence to the substrate and high efficiency against microbial biofilms can be developed for implant coatings and other advanced medical devices.

35. Antimicrobial polycaprolactone/polyethylene glycol embedded lysozyme coatings of Ti implants for osteoblast functional properties in tissue engineering

Authors: Visan, A; Cristescu, R; Stefan, N; Miroiu, M; Nita, C; Socol, M; Florica, C; Rasoga, O; Zgura, I; Sima, LE; Chiritoiu, M; Chifiriuc, MC; Holban, AM; Mihailescu, IN; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 243, DOI: 10.1016/j.apsusc.2016.11.129

In this study, coatings based on lysozyme embedded into a matrix of polyethylene glycol (PEG) and polycaprolactone (PCL) were fabricated by two different methods (Matrix Assisted Pulsed Laser Evaporation -MAPLE and Dip Coating) for obtaining antimicrobial coatings envisaged for long term medical applications. Coatings with different PEG: PCL compositions (3: 1; 1: 1; 1: 3) were synthesized in order to evaluate the antimicrobial activity of lysozyme embedded into the polymeric matrix. The main surface features, such as roughness and wettability, with impact on the microbial adhesion as well as on the eukaryote cell function were measured. The obtained composite coatings exhibited a significant antibacterial activity against Escherichia coli, Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus strains. As well, specific blended coatings showed appropriate viability, good spreading and normal cell morphology of SaOs2 human osteoblasts and mesenchymal stem cells (MSCs). These investigations highlight the suitability of biodegradable composites as implant coatings for decreasing the risk of bacterial contamination associated with prosthetic procedures. (C) 2016 Elsevier B.V. All rights reserved.

36. WETTABILITY BY WATER CONTACT ANGLE UPON THE SURFACE OF WOOL FABRICS COVERED WITH OXIDE NANOPARTICLES

Authors: Birzu, M; Frunza, L; Zgura, I; Cotorobai, VF; Ganea, CP; Preda, N; Enculescu, M

Published: JUL-SEP 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 931, DOI:

Wetting properties of wool textiles were studied either for the raw samples or for those functionalized via covering them at low temperature with nanoparticles of titanium dioxide or zinc oxide. Oxygen plasma pretreatment was performed before deposition. Characterization used optical examination, scanning electron microscopy, infrared spectroscopy, thermogravimetry, X-ray diffraction. Wetting properties were tested under static conditions by estimating the water contact angle. The sessile drop method was applied. The deposited matter represents 3 to 8 wt%, covering rather uniformly the fiber surface. Treated samples show mostly lower values of contact angle than the pristine ones. Cassie-Baxter model is discussed in relation to the equilibrium contact angle of the support.

37. Rod-like cyanophenyl probe molecules nanoconfined to oxide particles: Density of adsorbed surface species

Authors: Frunza, S; Frunza, L; Ganea, CP; Zgura, I; Bras, AR; Schonhals, A

Published: FEB 2 2016, EUROPEAN PHYSICAL JOURNAL PLUS, 131, DOI: 10.1140/epjp/i2016-16027-5

Surface layers have already been observed by broadband dielectric spectroscopy for composite systems formed by adsorption of rod-like cyanophenyl derivates as probe molecules on the surface of oxide particles. In this work, features of the surface layer are reported; samples with different amounts of the probe molecules adsorbed onto oxide (nano) particles were prepared in order to study their interactions with the surface. Thermogravimetric analysis (TGA) was applied to analyze the amount of loaded probe molecules. The density of the surface species n(s) was introduced and its values were estimated from quantitative Fourier transform infrared spectroscopy (FTIR) coupled with TGA. This parameter allows discriminating the composites into several groups assuming a similar interaction of the probe molecules with the hosts of a given group. An influence factor H is further proposed as the ratio of the number of molecules in the surface layer showing a glassy dynamics and the number of molecules adsorbed tightly on the surface of the support: It was found for aerosil composites and used for calculating the maximum filling degree of partially filled silica MCM-41 composites showing only one dielectric process characteristic for glass-forming liquids and a bulk behavior for higher filling degrees.

38. ZnO nanowires grown directly on zinc foils by thermal oxidation in air: Wetting and water adhesion properties

Authors: Florica, C; Preda, N; Costas, A; Zgura, I; Enculescu, I

Published: MAY 1 2016, MATERIALS LETTERS, 170, 159, DOI: 10.1016/j.matlet.2016.02.035

Large scale ZnO nanowire arrays were grown directly on zinc foils using the thermal oxidation in air method. The X-ray diffraction and reflectance investigations confirm that the as-grown nanowires properties are typical for ZnO having a hexagonal wurtzite crystalline structure and band-gap values between 3.2 and 3.3 eV. The scanning electron microscopy images prove that the density and the dimensions (diameter and length) of the ZnO nanowires can be tuned by controlling the oxidation temperature. Wettability studies reveal in the case of Zn foils a hydrophilic behavior with high water droplet adhesion which is transformed into a superhydrophobic one with low water droplet adhesion after the foils' surfaces are covered with ZnO nanowires. Obtaining functional surfaces with such interesting wetting properties using a simple, inexpensive and highly reproducible thermal oxidation in air technique is very attractive for anticorrosion coatings and self-cleaning applications. (C) 2016 Elsevier B.V. All rights reserved.

39. Fabrication of periodical surface structures by picosecond laser irradiation of carbon thin films: transformation of amorphous carbon in nanographite

Authors: Popescu, C; Dorcioman, G; Bita, B; Besleaga, C; Zgura, I; Himcinschi, C; Popescu, AC

Published: DEC 30 2016, APPLIED SURFACE SCIENCE, 390, 243, DOI: 10.1016/j.apsusc.2016.08.029

Thin films of carbon were synthesized by ns pulsed laser deposition in vacuum on silicon substrates, starting from graphite targets. Further on, the films were irradiated with a picosecond laser source emitting in visible at 532 nm. After tuning of laser parameters, we obtained a film surface covered by laser induced periodical surface structures (LIPSS). They were investigated by optical, scanning electron and atomic force microscopy. It was observed that changing the irradiation angle influences the LIPSS covered area. At high magnification it was revealed that the LIPSS pattern was quite complex, being composed of other small LIPSS islands, interconnected by bridges of nanoparticles. Raman spectra for the non-irradiated carbon films were typical for a-C type of diamond-like carbon, while the LIPSS spectra were characteristic to nano-graphite. The pristine carbon film was hydrophilic, while the LIPSS covered film surface was hydrophobic. (C) 2016 Elsevier B.V. All rights reserved.

40. Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition

Authors: Duta, L; Stan, GE; Popa, AC; Husanu, MA; Moga, S; Socol, M; Zgura, I; Miculescu, F; Urzica, I; Popescu, AC; Mihailescu, IN

Published: JAN 2016, MATERIALS, 9, DOI: 10.3390/ma9010038

We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility.

41. Fabrication of antimicrobial silver-doped carbon structures by combinatorial pulsed laser deposition

Authors: Mihailescu, IN; Bociaga, D; Socol, G; Stan, GE; Chifiriuc, MC; Bleotu, C; Husanu, MA; Popescu-Pelin, G; Duta, L; Luculescu, CR; Negut, I; Hapenciuc, C; Besleaga, C; Zgura, I; Miculescu, F

Published: DEC 30 2016, INTERNATIONAL JOURNAL OF PHARMACEUTICS, 515, 606, DOI: 10.1016/j.ijpharm.2016.10.041

We report on the selection by combinatorial pulsed laser deposition of Silver-doped Carbon structures with reliable physical-chemical characteristics and high efficiency against microbial biofilms. The investigation of the films was performed by scanning electron microscopy, high resolution atomic force microscopy, energy dispersive X-Ray Spectroscopy, X-ray diffraction, Raman spectroscopy, bonding strength "pull-out" tests, and surface energy measurements. In vitro biological assays were carried out using a large spectrum of bacterial and fungal strains, i.e., Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Enterococcus faecalis and Candida albicans. The biocompatibility of the films obtained was evaluated on MG63 mammalian cell cultures. The optimal combination with reasonable physical-chemical properties, efficient protection against microbial colonization and beneficial effects on human cells was found for Silver-doped Carbon films containing 2 to 7 at.% silver. These mixtures can be used to fabricate safe and efficient coatings of metallic implants, with the goal to decrease the risk of implant associated biofilm infections which are difficult to treat and often responsible for implant failure. (C) 2016 Elsevier B.V. All rights reserved.

42. POLYESTER FABRICS COVERED WITH AMORPHOUS TITANIUM DIOXIDE LAYERS: COMBINING WETTABILITY MEASUREMENTS AND PHOTOINDUCED HYDROPHILICITY TO ASSESS THEIR SURFACE PROPERTIES

Authors: Zgura, I; Frunza, S; Frunza, L; Enculescu, M; Florica, C; Cotorobai, VF; Ganea, CP

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 269, DOI:

Wettability properties of thin TiO2 amorphous layers obtained by sputtering or sol-gel onto polyester textile materials were investigated. Contact angle (CA) measurements by the sessile drop method were used to evaluate these properties. Comparison was performed with coated samples of related poly(lactic acid) material. The samples coated by sol gel have CAs a few degrees higher than those coated by sputtering. Wetting properties were conversely changed under alternate darkness/illumination conditions. Photoinduced hydrophilicity was observed even for these amorphous coating particles, being higher for sputtered samples than for sol gel ones.

43. Wicking behavior of fabrics described by simultaneous acquiring the images of the wet region and monitoring the liquid weight

Authors: Cotorobai, VF; Zgura, I; Birzu, M; Frunza, S; Frunza, L

Published: MAY 20 2016, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 497, 153, DOI: 10.1016/j.colsurfa.2016.02.040

An experimental study on the radial spreading of the liquid from a virtually infinite reservoir onto a horizontal fabric sample was performed using a simple setup which is presented in two variants: One variant (the simplest) collects the images of the wet spot during the radial outward wicking and the other variant collects the images simultaneously with the monitoring of the weight decrease of the liquid reservoir. We notice that recording with a webcam gives advantages in the subsequent data processing. Afterward, the resulting image series were processed with routines developed in LabVIEW to determine the area of the wet spot. The programs are better adapted to the inhomogeneous and anisotropic structure specific to textiles than the existent edge-finding algorithms. The time dependence of the wet area provides information about the wicking kinetics and further, by modeling the data, to the possible mechanism. The experiments were performed using solutions of red (rhodamin 6B) or blue (brilliant blue E133) dyes in linen and polyester samples differing besides the chemical structure in the roughness of their surfaces as well. The data allow an easy comparison between the textile behavior. Determination of the mass loss of the test liquid might be useful especially for the colored fabrics. The infinite reservoir case is compared with that of the finite reservoir. (C) 2016 Elsevier B.V. All rights reserved.

44. Dielectric Properties of LDH-Type Layered Materials Containing Zn or Mg Ions : On the Non Monotonous Temperature Dependence of Relaxation Times

Authors: Frunza, L; Frunza, S; Ganea, CP; Zgura, I; Neatu, F; Parvulescu, VI

Published: 2015, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 18, 328, DOI:

The electrical behavior of layered double hydroxides containing Al or Ga as the trivalent ions and Mg or Zn as bivalent ions was evaluated using broadband dielectric spectroscopy in a wide temperature range. Besides conduction effects a relaxation peak is observable at high frequencies which is assigned to the reorientational fluctuations of water molecules adsorbed on the oxide surface or in the interlayer voids. The Maxwell-Wagner-Sillars peak, superimposed to the conductivity phenomenon is observable at low frequencies. A non-monotonous temperature dependence of the relaxation rates of the relaxation process has been found. A quantitative description of this dependence was possible based on a model assuming two competing processes: rotational fluctuation of water molecules and formation of additional defects. Reasonable values for the characteristic parameters were obtained. Thus the water behavior in the studied layered oxides is similar to that observed for water in other porous materials. However, the activation energy of the rotational fluctuation, the pre exponential factor and the number of defects are higher whereas the value of the energy of defect formation is lower in the layered oxide materials than for water confined to nanoporous molecular sieves, porous glasses or in bulk ice.

45. Layered materials of LDH-type containing Zn ions: dielectric measurements show rotational fluctuations of water molecules

Authors: Frunza, L; Ganea, P; Zgura, I; Frunza, S; Neatu, F; Parvulescu, VI

Published: 2015, 2015 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 70, DOI:

Layered double hydroxide (LDH) materials containing Zn ions were studied by broadband dielectric spectroscopy to follow up rotational molecular dynamics of confined water. One main relaxation process was observed in the experimental window; it was assigned to fluctuations of water molecules forming a strongly adsorbed thin layer upon the oxide surface. The temperature dependence of the relaxation rates has an unusual shape characterized by the presence of a maximum. Despite the characteristic parameters, this non-monotonous dependence is shown to be a rather general feature for water confined to LDHs.

46. Titanium dioxide layer deposited at low temperature upon polyester fabrics

Authors: Zgura, I; Frunza, S; Frunza, L; Enculescu, M; Florica, C; Ganea, CP; Negrila, CC; Diamandescu, L

Published: JUL-AUG 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1063, DOI:

TiO2 deposition by sputtering or sol-gel techniques was applied onto less thermal stable polyester textiles and onto a related poly(lactic acid) material. The temperature of deposition and of the further treatment was low enough as allowed by the support nature. Structural and spectroscopic characterization of the raw and coated samples has been performed. TiO2 coated particles are amorphous as indicated by X-ray diffraction and scanning electron microscopy. Sputtered layers consist in aggregates randomly distributed on the substrate while the sol gel layers show a uniform coverage of nanoparticles having a mosaic-like structure. The morphology of the sputtered layers depends on the deposition pressure as well. The loading degree estimated on the basis of the thermogravimetric data is rather low (ca. 2%), but the fabric properties are much influenced by the deposition. Photocatalytic activity also present on the coated surfaces was evaluated in the methylene blue degradation. TiO2 layer is quite adherent as checked by an ultra-sonication method.

47. DEPOSITION OF TITANIUM DIOXIDE LAYERS UPON POLYESTER TEXTILE MATERIALS: CHECKING THE ADHERENCE BY ULTRA-SONICATION

Authors: Zgura, I; Frunza, S; Enculescu, M; Florica, C; Cotorobai, F

Published: 2015, ROMANIAN JOURNAL OF PHYSICS, 60, 494, DOI:

An important parameter of deposited thin films is their adhesion to the substrate materials, we focused on the adhesion of TiO2 layer by sol-gel or sputtering onto textile substrate as checked by an ultra-sonication method. The characterization-made prior and after the tests have shown a good adherence of the nanoparticles, despite the low deposition temperature.

48. Composite biodegradable biopolymer coatings of silk fibroin - Poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) for biomedical applications

Authors: Miroiu, FM; Stefan, N; Visan, AI; Nita, C; Luculescu, CR; Rasoga, O; Socol, M; Zgura, I; Cristescu, R; Craciun, D; Socol, G

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1131, DOI: 10.1016/j.apsusc.2015.07.120

Composite silk fibroin-poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) (SF-PHBV) biodegradable coatings were grown by Matrix Assisted Pulsed Laser Evaporation on titanium substrates. Their physicochemical properties and particularly the degradation behavior in simulated body fluid at 37 degrees C were studied as first step of applicability in local controlled release for tissue regeneration applications. SF and PHBV, natural biopolymers with excellent biocompatibility, but different biodegradability and tensile strength properties, were combined in a composite to improve their properties as coatings for biomedical uses. FTIR analyses showed the stoichiometric transfer from targets to coatings by the presence in the spectra of the main absorption maxima characteristic of both polymers. XRD investigations confirmed the FTIR results showing differences in crystallization behavior with respect to the SF and PHBV content. Contact angle values obtained through wettability measurements indicated the MAPLE deposited coatings were highly hydrophilic; surfaces turning hydrophobic with the increase of the PHBV component. Degradation assays proved that higher PHBV contents resulted in enhanced resistance and a slower degradation rate of composite coatings in SBF. Distinct drug-release schemes could be obtained by adjusting the SF:PHBV ratio to controllably tuning the coatings degradation rate, from rapid-release formulas, where SF predominates, to prolonged sustained ones, for larger PHBV content. (C) 2015 Elsevier B.V. All rights reserved.

49. COVERING OBLIQUELY DEPOSITED SiOx WITH POLYVINYL CARBAZOLE CHANGES THE ORIENTATION PROPERTIES

Authors: Frunza, S; Zgura, I; Frunza, L; Rasoga, O; Gheorghe, P; Petris, A; Vlad, VI

Published: 2014, ROMANIAN JOURNAL OF PHYSICS, 59, 744, DOI:

Alignment layers of polyvinylcarbazole (PVK) were obtained by withdrawing from different solutions in toluene onto glass plates having SiOx layers obliquely evaporated in vacuum at 82 degrees. The alignment direction of nematic liquid crystal molecules with cyan-end group imposed by bare SiOx layers is changed when these layers are coated with PVK; the same happens with over layers of polyvinylimidazole or of polyvinylcinnamate. The effect is inhibited by doping PVK with fullerene C60 (0.1%), when the liquid crystal orientation specific for bare SiOx obliquely evaporated substrates is obtained. Other nematic (with methoxy-end group) does not show change of the orientation properties by covering the SiOx obliquely deposited layers with the mentioned polymer over layers.

50. Supported Pd-Cu Nanoparticles for Water Phase Reduction of Nitrates. Influence of the Support and of the pH Conditions

Authors: Papa, F; Balint, I; Negrila, C; Olaru, EA; Zgura, I; Bradu, C

Published: DEC 10 2014, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 53, 19103, DOI: 10.1021/ie503070f

PdCu nanoparticles were synthesized by the alkaline polyol method and further supported on alumina or titania. The nanoparticles show a crystalline Pd core and a shell rich in amorphous copper as was put in evidence by complex characterization methods (X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and CO chemisorption). The performances of as-prepared catalysts in the water phase reduction of nitrate were assessed in comparison with catalysts obtained by impregnation. Supported nanoparticle catalysts show a high activity in the reduction of nitrates, better than the impregnated catalysts. The importance of the support choice was discussed. The catalyst based on PdCu nanoparticles supported on titania (PCT-np) is the most active, selective, and stable among those investigated. Also, the influence of pH conditions on the PCT-np catalyst performances was emphasized.

51. POLYESTER FABRICS COVERED WITH ZNO PARTICLES: PARTICLE INTERACTION WITH THE SURFACE SHOWN BY DIELECTRIC PROPERTIES

Authors: Ganea, CP; Frunza, L; Zgura, I; Preda, N; Matei, E; Frunza, S

Published: OCT-DEC 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 1503, DOI:

Polyester fabrics modified with ZnO particles by electroless deposition were investigated by broadband dielectric spectroscopy in a parallel capacitor between 10(-2) and 10(7) Hz in a temperature interval from ca. 123 to 473 K. Textile samples were routinely characterized for the structure and interaction of the ZnO particles with the fiber surface. Since a textile fabric material is a mixture of air and fibers, the parameters taken into consideration should be called as effective ones. The deposition of ZnO particles lead to complex dielectric spectra and to the temperature dependence of the decomposed peaks following Arrhenius law.

52. Superhydrophobic ZnO networks with high water adhesion

Authors: Florica, C; Preda, N; Enculescu, M; Zgura, I; Socol, M; Enculescu, I

Published: AUG 8 2014, NANOSCALE RESEARCH LETTERS, 9, DOI: 10.1186/1556-276X-9-385

ZnO structures were deposited using a simple chemical bath deposition technique onto interdigitated electrodes fabricated by a conventional photolithography method on SiO2/Si substrates. The X-ray diffraction studies show that the ZnO samples have a hexagonal wurtzite crystalline structure. The scanning electron microscopy observations prove that the substrates are uniformly covered by ZnO networks formed by monodisperse rods. The ZnO rod average diameter and length were tuned by controlling reactants' concentration and reaction time. Optical spectroscopy measurements demonstrate that all the samples display bandgap values and emission bands typical for ZnO. The electrical measurements reveal percolating networks which are highly sensitive when the samples are exposed to ammonia vapors, a variation in their resistance with the exposure time being evidenced. Other important characteristics are that the ZnO rod networks exhibit superhydrophobicity, with water contact angles exceeding 150 degrees and a high water droplet adhesion. Reproducible, easily scalable, and low-cost chemical bath deposition and photolithography techniques could provide a facile approach to fabricate such ZnO networks and devices based on them for a wide range of applications where multifunctionality, i.e., sensing and superhydrophobicity, properties are required.

53. Zinc Oxide and Polysaccharides: Promising Candidates for Functional Nanomaterials

Authors: Preda, N; Enculescu, M; Zgura, I; Socol, M; Florica, C; Evanghelidis, A; Matei, E; Enculescu, I

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 136, DOI: 10.1007/978-3-662-44479-5_5

Recently, ZnO and natural polysaccharides have received more and more attention as interesting components for designing complex functional nanomaterials, key elements being their high occurrence and low-cost. In this chapter are presented possibilities for tailoring the ZnO properties by using polysaccharides in the synthesis process as well as reports on the functionalization of cellulose-based natural fabrics with ZnO. In both cases, in the preparation step were used only simple and scalable wet chemical methods. The resulting materials with suitable characteristics, e.g. dependence of the ZnO nanostructures optical properties on their morphology or high-UV blocking and superhydrophobicity for ZnO-functionalized fabrics, can find applications in domains where such qualities are required.

54. Polyester fabrics coated with SiOx nanoparticles by vacuum deposition at small angle. Structural characterization and wetting properties

Authors: Frunza, L; Zgura, I; Enculescu, M; Frunza, S; Ganea, CP; Rasoga, O; Cotorobai, F; Dorogan, A

Published: JAN-FEB 2014, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 16, 181, DOI:

Vacuum deposition at small angle was successfully applied in deposition of SiOx particles onto polyester textile materials; this deposition is here presented in comparison with that upon other materials made from poly(lactic acid), polyamide or hemp. Structural and spectroscopic characterization of deposited samples has been performed and compared with that of the raw materials. The deposited particles are amorphous. Contact angle measurement by the sessile drop method, was used to study the wettability behavior of the investigated composite systems. The hierarchical roughness structure generates hydrophylic properties onto polyester fabrics and the other functionalized samples after deposition. The deposition technique was proven to be highly reproducible, easy scalable and cheap, allowing a wide range of applications.

55. Superhydrophobic properties of cotton fabrics functionalized with ZnO by electroless deposition

Authors: Preda, N; Enculescu, M; Zgura, I; Socol, M; Matei, E; Vasilache, V; Enculescu, I

Published: FEB 15 2013, MATERIALS CHEMISTRY AND PHYSICS, 138, 261, DOI: 10.1016/j.matchemphys.2012.11.054

Cotton fabrics were coated with arrays of ZnO hexagonal prisms using an electroless (catalytic/auto-catalytic) deposition process. A typical three step method, similar to those used for electroless deposition of metals on insulating substrates, consisting of pre-activation, activation and deposition steps was employed. The low-dimensional ZnO particles were grown from an aqueous solution containing zinc nitrate as source of zinc ions and dimethylamineborane as reducing agent. The as-obtained ZnO-coated cotton fabrics were characterized from the point of view of structure by X-ray diffraction (XRD) and morphology by scanning electron microscopy (SEM). The XRD studies demonstrate that the ZnO particles have a hexagonal wurtzite crystalline structure. The SEM observations prove that the cotton fibers are homogeneously covered by hexagonal prisms which have uniform base size of approximately 500 nm and height of 1 mu m. Optical spectroscopy measurements show that the functionalization with ZnO strongly decreases the transmittance in the UV vis region of the cotton fabrics. An important characteristic is that the ZnO-functionalized cotton fabrics exhibit superhydrophobicity, with water contact angles exceeding 150 degrees. The technique described is highly reproducible, easy scalable and cheap, allowing a wide range of applications. (C) 2012 Elsevier B.V. All rights reserved.

56. Surface free energy of smooth and dehydroxylated fused quartz from contact angle measurements using some particular organics as probe liquids

Authors: Zgura, I; Moldovan, R; Negrila, CC; Frunza, S; Cotorobai, VF; Frunza, L

Published: JUL-AUG 2013, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 15, 634, DOI:

The dispersion and the polar independent contributions to the surface free energy in the case of fused quartz plates were evaluated by contact angle measurements against a series of liquids like water, glycerol, ethylene glycol, dimethyl sulfoxide and a nematic mixture NP5 of azoxybenzene type compounds. The smooth fused quartz plates were thermally pretreated at 240 degrees C and 1000 degrees C to decrease the number of surface hydroxyl groups; their surface was characterized by X-ray photoelectron spectroscopy. The contact angle data were further processed applying either the approach of Owens-Wendt with geometric mean or the Wu's approach of harmonic mean of nonpolar and polar interactions. The liquids were chosen thus to fulfill Della Volpe and Siboni's criterion namely that these have the condition number of system matrix low enough. The values obtained for the components of surface free energy were discussed in comparison with the results obtained in literature for crystalline quartz or for other silica forms as bulk or films. The study has shown a decrease of the polar component of the surface tension by increase of the pretreatment temperature.

57. ZnO Thin Films Deposited on Textile Material Substrates for Biomedical Applications ZnO Thin Films Deposited on Textiles

Authors: Duta, L; Popescu, AC; Dorcioman, G; Mihailescu, IN; Stan, GE; Zgura, I; Enculescu, I; Dumitrescu, I

Published: 2012, TECHNOLOGICAL INNOVATIONS IN SENSING AND DETECTION OF CHEMICAL, BIOLOGICAL, RADIOLOGICAL, NUCLEAR THREATS AND ECOLOGICAL TERRORISM, 210, DOI: 10.1007/978-94-007-2488-4_20

We report on the coating with ZnO adherent thin films of cotton woven fabrics by Pulsed laser deposition technique in order to obtain innovative textile materials, presenting protective effects against UV radiations and antifungal action.

58. Radical modification of the wetting behavior of textiles coated with ZnO thin films and nanoparticles when changing the ambient pressure in the pulsed laser deposition process

Authors: Popescu, AC; Duta, L; Dorcioman, G; Mihailescu, IN; Stan, GE; Pasuk, I; Zgura, I; Beica, T; Enculescu, I; Ianculescu, A; Dumitrescu, I

Published: SEP 15 2011, JOURNAL OF APPLIED PHYSICS, 110, DOI: 10.1063/1.3639297

Cotton/polyester woven fabrics were functionalized with ZnO thin films or nanoparticles by pulsed laser deposition, using a KrF* excimer laser source. Depending on the number of applied laser pulses, well-separated nanoparticles (for 10 pulses) or compact thin films (for 100 pulses) were deposited. The synthesized nanostructures were evaluated morphologically by scanning electron microscopy and atomic force microscopy, physico-chemically by x-ray diffraction and functionally by the contact angle method. By modifying the ambient gas nature and pressure in the deposition chamber, hydrophilic or hydrophobic surfaces were obtained. When using an oxygen flux, both the deposited thin films and nanoparticles were hydrophilic. After deposition in vacuum, the nanoparticles were hydrophobic, but the thin films were super-hydrophobic. This radical modification of wetting behavior was assigned to the differences in microstructure features and surface electrical charging in the two cases. (C) 2011 American Institute of Physics. [doi:10.1063/1.3639297]

59. OPTICALLY INDUCED BIREFRINGENCE OF A p-AMINOAZOBENZENE-EPDXY RESIN DERIVATIVE

Authors: Beica, T; Zgura, I; Frunza, L; Ganea, P; Frunza, S; Dumitrache, L; Raditoiu, V; Wagner, L

Published: 2011, ROMANIAN REPORTS IN PHYSICS, 63, 752, DOI:

A derivative of p-aminoazobenzene-epoxy resin was studied. Visually examination between crossed polarizers does not show birefringence but it can be optically induced. Changing the polarization direction of the irradiating light leads to the changing of the privileged direction of the induced birefringence. The birefringence value was evaluated and compared with liquid crystals as anisotropic compounds.

60. Involvement of cyan and ester groups in surface interactions of aerosil-cyanophenyl alkyl benzoate systems with high silica density: Infrared investigations

Authors: Frunza, L; Frunza, S; Zgura, I; Beica, T; Gheorghe, N; Ganea, P; Stoenescu, D; Dinescu, A; Schonhals, A

Published: APR 2010, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 75, 1235, DOI: 10.1016/j.saa.2009.12.029

Composites prepared from aerosil A380 and liquid crystals (LCs) of 4-n-alkyl-4'-cyanophenyl benzoate type, with four to six carbon atoms in the alkyl chain were investigated by infrared spectroscopy. Their high silica content (of 2-7 g aerosil/1 g of LC) was given by thermogravimetric investigations and allows the observation of a rather thin LC layer on the silica particles. Several surface species onto the external surface of the grains were demonstrated. Arguments are given that monomer and dimer species are present in the bulk cyanophenyl benzoate materials while bulk-like species along with hydrogen-bonded ones coexist in the so-called surface layer of the composites. The main interaction of LC molecules with the aerosil surface is by hydrogen bonding taking place with the involvement of the cyan group. There is a contribution of ester carbonyl group to these surface interactions but this cannot be well quantified. (C) 2009 Elsevier B.V. All rights reserved.

61. Nanostructured gold layers. I. Deposition by Vacuum evaporation at small angles of incidence

Authors: Beica, T; Frunza, S; Zgura, I; Frunza, L; Cotarlan, C; Negrila, C; Vlaicu, AM; Zaharia, CN

Published: FEB 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 353, DOI:

Gold layers were deposited at oblique incidence onto glass plates. A B30.2 Hochvakuum Bedampfungsanlage equipment was used in this aim. The deposition conditions were chosen in order to obtain nanostructured layers. Correlations were found among these conditions and the corresponding nomograms were then obtained. Examples of such depositions were given and the layers structure was characterized and additionally supported by observing the molecular alignment given in the liquid crystal cells obtained with these gold layers.

62. ASSESSMENT OF THE IMPRESSION MATERIALS BY INVESTIGATION OF THE HYDROPHILICITY

Authors: Zgura, I; Beica, T; Mitrofan, IL; Mateias, CG; Pirvu, D; Patrascu, I

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 755, DOI:

The wettability of 18 dental impression materials, commercially available, during their working time was investigated using the contact angle method, as a good wettability is desired to obtain a high fidelity impression. Polyetheric materials, A-silicones with added surfactants and C-silicones were found to have a good wettability. Alginate was found to be the most hydrophilic material, but this quality decreases in time. In the paper an explanation for the time dependence of the contact angle is advanced.

63. Nanostructured gold layers. II. Gold deposition onto polystyrene substrate

Authors: Zgura, I; Beica, T; Frunza, S; Rasoga, O; Galca, A; Frunza, L; Moldovan, A; Dinescu, M; Zaharia, C

Published: FEB 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 359, DOI:

In the aim to improve the adherence of the nanostructured gold layers onto glass substrate, gold deposition has been first time performed onto a polystyrene (PS) layer. The PS layer of ca. 50nm was spin-coated onto glass plates from a toluene solution. Gold layers of 10-20nm were vacuum deposited at small incidence angle. We found that at variance from the plates with gold deposited directly on the glass, the plates with an intermediate PS layer do not peel under overnight treatment in ethanol solution. The layers were characterized by several methods. X-ray diffraction (XRD) measurements showed that gold peaks have the position corresponding to the face-centered cubic structure: However, the crystallites on the sample with PS layer seem to be a little bit smaller than those with gold deposited directly onto the glass. XR reflectometry measurements have given the thickness of the gold layer in good agreement with the value estimated from quartz monitor readings and with the ellipsometric data as well, Liquid crystal cells were obtained to observe the molecular alignment imposed by the nanostructured gold layer deposited onto PS film. A rather strong interaction of gold atoms with the substrate molecules can be considered on the basis of the XRD and ellipsometry measurements.

64. Dynamics of cyanophenyl alkylbenzoate molecules in the bulk and in a surface layer adsorbed onto aerosil. Variation of the lengths of the alkyl chain

Authors: Frunza, S; Schonhals, A; Frunza, L; Beica, T; Zgura, I; Ganea, P; Stoenescu, D

Published: JUN 16 2010, CHEMICAL PHYSICS, 372, 60, DOI: 10.1016/j.chemphys.2010.04.031

The molecular mobility of 4-butyl- and 4-pentyl-4'-cyanophenyl benzoate (CP4B, CP5B) and their composites prepared from aerosil A380 was investigated by broadband dielectric spectroscopy in a large temperature range. Thermogravimetric and infrared investigations were additionally performed. High silica density (larger than 7 g aerosil/1 g of liquid crystal) was selected to observe a thin layer adsorbed on the surface of the silica particles. The data were compared with those of the member of the series with six carbon atoms in the alkyl tail. Bulk CP4B and CP5B show the dielectric behaviour expected for liquid crystals. For the composites one relaxation process is observed at frequencies much lower than those for the corresponding bulk, which was assigned to the dynamics of the molecules in a surface layer. The temperature dependence of the relaxation rates (and of the dielectric strength) shows a crossover behaviour with two distinguished regimes. At higher temperatures the data obey the Vogel-Fulcher-Tammann law, whereas an Arrhenius law is observed at lower temperature, in a close similarity to the behaviour of a constrained dynamic glass transition. The estimated Vogel and crossover temperature is independent on the tail length, while the activation energy for the low temperature branch increases weakly with increasing the alkyl tail. (C) 2010 Elsevier B. V. All rights reserved.

65. LOW POWER LASER INDUCED OPTICAL NONLINEARITIES IN ORGANIC MOLECULES

Authors: Dancus, I; Vlad, VI; Petris, A; Frunza, S; Beica, T; Zgura, I; Nicolescu, FA; Jerca, VV; Vuluga, DM

Published: 2010, ROMANIAN REPORTS IN PHYSICS, 62, 580, DOI:

Experimental demonstration of low power laser induced optical nonlinearities in two different types of specially designed materials: dye doped liquid crystals and copolymers with new pendant azobenzene moieties, is presented. Saturation of the nonlinear refractive index change is observed for some of the samples. The origin of the huge nonlinearity and its saturation in the continuous wave laser regime and at low power levels are analyzed.

66. STUDIES ON MULTIFUNCTIONAL TEXTILE MATERIALS. IMAGE BASED ANALYSIS AND CLASSIC SPECTROSCOPY

Authors: Beica, T; Frunza, L; Nistor, LC; Zgura, I; Dorogan, A; Carpus, E

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 400, DOI:

Measurements by optical microscopy and spectroscopy were performed on different textile materials (yarn, woven, knitted materials) in order to get their characterization. Thus, using non-specialized classical equipment, the value of the yarn diameter can be estimated. The yarn behavior during the stretching can be directly observed. The observation of the water imbibition by following the shape and stability of a water droplet placed onto the textile material was also developed; in this way the wetting kinetics of different textile materials was obtained. In addition, the spectral properties of woven materials allowed for the study of the modifications induced by different treatments of the woven materials.

67. Temperature dependence of the density of some liquid crystals in the alkyl cyanobiphenyl series

Authors: Zgura, I; Moldovan, R; Beica, T; Frunza, S

Published: AUG 2009, CRYSTAL RESEARCH AND TECHNOLOGY, 44, 888, DOI: 10.1002/crat.200900162

Experimental results for the temperature dependence of the density of propyl - cyanobiphenyl (3CB), butyl - cyanobiphenyl (4CB) and hexyl - cyanobiphenyl (6CB) are presented. The results arc compared with previous results for temperature dependence of other members of the alkyl cyanobiphenyl series (nCB). The deviation of the density from linear temperature dependence is discussed in terms of the recently discovered corresponding rule for nematic liquid crystals. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

68. Study of Ester-Type Liquid Crystals by TSDC and Optical Investigations

Authors: Manaila-Maximean, D; Rosu, C; Zgura, I; Frunza, L; Stoenescu, D

Published: 2009, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 512, 2012, DOI: 10.1080/15421400903050830

We study ester-type liquid crystal, 4'-cyanophenyl 4-n-hexyl benzoate and its homologue 4'-cyanophenyl 4-n-pentyl benzoate. We used the Thermally Stimulated Depolarization Currents method and found information about phase transition temperature, and activation energies. The temperatures of phase transitions were compared to those obtained by classical DSC/DTA measurements. Simultaneously with the TSDC, we measured the optical transmission; we found a decrease of the optical transmission when it was measured after a greater pre-applied polarizing electric field.

69. Studies on multifunctional textile materials. Plasma deposition onto textile materials and onto reference plates

Authors: Beica, T; Nistor, LC; Morosanu, C; Frunza, L; Stan, GE; Zgura, I; Marcov, D; Dorogan, A; Carpus, E

Published: OCT 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2817, DOI:

The magnetron sputtering method was used to obtain layers of indium tin oxide or hydroxyapatite on glass fiber woven and on reference glass plates. The layers were characterized by scanning microscopy, UV-vis spectroscopy and conductivity measurements. Hydrophilic properties of the woven samples were investigated by optical microscopy following the behavior of a water droplet upon the each of the samples. The change of the drop profile in time due to wetting of the fabric leads to the wetting kinetics. The most efficient treatments to improve the hydrophilic/wetting properties of the glass fiber woven were found.

70. On the optical thickness dependence of the electro-optical properties of an in-plane switching LC cell

Authors: Beica, T; Frunza, S; Zgura, I; Moldovan, R; Dinescu, A

Published: MAR 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 563, DOI:

The optical transmission of a liquid crystal cell with in-plane switching (IPS) mode is studied as function of the thickness for different rubbing angles and anchoring energy. It was found that the light transmission has a maximum at the value of similar to 0.66 for the ratio of the optical path difference (introduced by the undisturbed cell) to X and that this value does not depend on lambda, in the case of a very strong anchoring energy and of a rubbing angle of 13 degrees. These experimental results agree very well with simulations using a simplified model. Moreover, the simulations have shown that the thickness corresponding to such a maximum optical path difference depends non-monotonously on the anchoring strength for five values of the rubbing angles (in the range 0 to 40 degrees). For a given anchoring energy this thickness decreases with increasing rubbing angle.

71. Study of non catalytic oxidehydrogenation of isobutane in an integral reactor

Authors: Grecu, MN; Burducea, G; Grecu, V; Moldovan, R; Beica, T; Zgura, I

Published: MAR 2007, REVUE ROUMAINE DE CHIMIE, 52, 281, DOI:

X-band ESR spectra of the calamitic and discotic lyotropic nematic phases in sodium dodecyl sulphate (SDS)/decanol/water system, doped with paramagnetic nitroxide free radicals are analyzed in this paper. The studied temperature range was chosen to include phase transitions of the lyotropic systems. The variation of the surfactant hydrocarbon chains ordering versus temperature is determined by the hyperfine splitting tensor (,4) and the spectroscopic splitting tensor ((g) under bar) anisotropies. The temperature dependence of the molecular order parameters for both lyotropic systems and the corresponding angular fluctuations are presented and discussed.

72. Interfacial tension of some liquid crystals in the cyanobiphenyl series at the interface with glycerol

Authors: Beica, T; Moldovan, R; Zgura, I; Frunza, S

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3627, DOI:

The temperature dependence of the interfacial tension for three compounds from the homologous series of alkylcyanobiphenyl (nCB), 5CB, 7CB and 8CB, at the interface with glycerol was measured in a temperature range from mesomorphic to isotropic phase. The drop shape method of measure was used. The interfacial tension of all the studied liquid crystals presents an anomalous behaviour with maximum and small upward jumps at the phase transitions, in rising temperature.

73. Mechanism of homeotropic alignment of a doped liquid crystal

Authors: Beica, T; Moldovan, R; Zgura, I; Frunza, S; Poterasu, M

Published: AUG 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1515, DOI:

In the paper, the physico-chemical orientation mechanism on solid surfaces for a liquid crystal (NP5 from Merck) doped for homeotropic alignment, is tested. For that, the dispersion and polar parts of surface tension of the liquid crystal are determined. Using substrates with and without adsorbed surfactant, the dispersion and polar parts of the surface tension of the substrates were also measured. Comparison of liquid and solid surface tensions, involved in the physico-chemical mechanism, failed to explain the difference of the molecular alignment for the two substrates. In the presence of the surfactant adsorbed on the surface, the steric model probably gives the explanation for the homeotropic alignment.

74. Embedding Jacobsen manganese(III) salen complex into nanoporous molecular sieves: Spectroscopic characterisation of host-guest interactions

Authors: Frunza, L; Zgura, I; Nicolaie, I; Dittmar, A; Kosslick, H; Fricke, R

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2148, DOI:

We report some spectroscopic arguments showing the guest-host interactions in the case of the composites containing Jacobsen salen complex and nanoporous molecular sieves of different types: SBA-15, MCM-48, MCM-41. The complex was embedded by impregnation, but care was given for washing out the weakly anchored part. Siliceous nanoporous materials lead to a weaker interaction than A1 containing forms. Thermal analysis has shown that at least in the case of the composite containing MCM-41 the embedded complex still contain chloride ions, therefore the bonding to the surface was apical. In situ experiments indicate that the thermal stability of the embedded complex is higher than in the free state. The differences among the composites coming from the structure of the molecular sieves are discussed.

75. Peculiar orientation of nematic liquid crystals on rubbed polyvinylimidazole

Authors: Frunza, S; Beica, T; Moldovan, R; Zgura, I; Frunza, L

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2157, DOI:

Alignment properties of rubbed films of polyvinyl imidazole were studied by observing with the polarizing microscope the features of the nematic liquid crystal (LC) droplets onto these layers. It was found that the observing of the droplets can reveal the direction of easy axis on the alignment substrate not only in the case of LC having the director normal to the LC/air interface but also in the case of the director tangent to this interface, when no disclination line could be seen. We observed that some of the LCs are oriented parallel to the rubbing direction, but the other LCs are perpendicularly oriented. This peculiar behavior is at variance to that found on rubbed layers of polyvinyl alcohol. The role of the end-groups in the structure of the LCs on the alignment properties is discussed.

76. BIOPHYSICAL ASPECTS OF BIO-NANOSILVER GENERATED FROM URTICA DIOICA LEAVES AND VITIS VINIFERA FRUITS' EXTRACTS