National Institute Of Materials Physics - Romania

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.

CuO-ZnO core-shell radial heterojunction nanowire arrays were obtained by a simple route which implies two cost-effective methods: thermal oxidation in air for preparing CuO nanowire arrays, acting as a p-type core and RF magnetron sputtering for coating the surface of the CuO nanowires with a ZnO thin film, acting as a n-type shell. The morphological, structural, optical and compositional properties of the CuO-ZnO core-shell nanowire arrays were investigated. In order to analyse the electrical and photoelectrical properties of the metal oxide nanowires, single CuO and CuO-ZnO core-shell nanowires were contacted by employing electron beam lithography (EBL) and focused ion beam induced deposition (FIBID). The photoelectrical properties emphasize that the p-n radial heterojunction diodes based on single CuO-ZnO core-shell nanowires behave as photodetectors, evidencing a time-depending photoresponse under illumination at 520 nm and 405 nm wavelengths. The performance of the photodetector device was evaluated by assessing its key parameters: responsivity, external quantum efficiency and detectivity. The results highlighted that the obtained CuO-ZnO core-shell nanowires are emerging as potential building blocks for a next generation of photodetector devices.

Organic bulk heterojunctions (BHJ) based on zinc phthalocyanine (ZnPc), fullerene compounds (C60 fullerene and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM)), and 5,6,11,12-tetraphenylnaphthacene (rubrene) were fabricated through the matrix-assisted pulsed-laser evaporation (MAPLE) technique. Thus, ZnPc:C60 and ZnPc:PC70BM binary BHJ and ZnPc:rubrene:PC70BM ternary BHJ were deposited as thin films on various substrates. The preservation of the chemical structure of the organic compounds during the MAPLE deposition was confirmed by infrared spectroscopy. The structural, optical, and morphological properties of the deposited layers were investigated by X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence (PL), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM), respectively. Further, the electrical properties of the developed structures based on ZnPc:C60, ZnPc:PC70BM, and ZnPc:rubrene:PC70BM were evaluated. The J-V characteristics of the organic structures, recorded under illumination, show that an increase in the open-circuit voltage (V-OC) is achieved in the case of the ternary blend in comparison with that obtained for the binary blends. The results evidenced that MAPLE-deposited thin films containing binary and ternary organic bulk heterojunctions can find applications in the field of photovoltaic devices.

Cu2ZnSnS4 (CZTS) is an economically and environmentally friendly alternative to other toxic and expensive materials used for photovoltaics, however, the variation in the composition during synthesis is often followed by the occurrence of the secondary binary and ternary crystalline phases. These phases produce changes in the optical absorption edge important in cell efficiency. We explore here the secondary phases that emerge in a combinatorial Cu2S-ZnS-SnS2 thin films library. Thin films with a composition gradient were prepared by simultaneous magnetron sputtering from three binary chalcogenide targets (Cu2S, SnS2 and ZnS). Then, the samples were crystallized by sulfurization annealing at 450 degrees C under argon flow. Their composition was measured by energy dispersive X-ray spectroscopy (EDX), whereas the structural and optical properties were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and optical transmission measurements. As already known, we found that annealing in a sulfur environment is beneficial, increasing the crystallinity of the samples. Raman spectroscopy revealed the presence of CZTS in all the samples from the library. Secondary crystalline phases such as SnS2, ZnS and Cu-S are also formed in the samples depending on their proximity to the binary chalcogenide targets. The formation of ZnS or Cu-S strongly correlates with the Zn/Sn and Cu/Zn ratio of the total sample composition. The presence of these phases produces a variation in the bandgap between 1.41 eV and 1.68 eV. This study reveals that as we go further away from CZTS in the composition space, in the quasi-ternary Cu2S-ZnS-SnS2 diagram, secondary crystalline phases arise and increase in number, whereas the bandgap takes values outside the optimum range for photovoltaic applications.

Hydroxyapatite (HAp) and samarium doped hydroxyapatite, Ca10-xSmx(PO4)(6)(OH)(2),x(Sm)= 0.05, (5SmHAp), coatings were prepared by sol-gel process using the dip coating method. The stability of 5SmHAp suspension was evaluated by ultrasound measurements. Fourier transform infrared spectroscopy (FTIR) was used to examine the optical characteristics of HAp and 5SmHAp nanoparticles in suspension and coatings. The FTIR analysis revealed the presence of the functional groups specific to the structure of hydroxyapatite in the 5SmHAp suspensions and coatings. The morphology of 5SmHAp nanoparticles in suspension was evaluated by transmission electron microscopy (TEM). Moreover, scanning electron microscope (SEM) was used to evaluate the morphology of nanoparticle in suspension and the morphology of the surface on the coating. The SEM and TEM studies on 5SmHAp nanoparticles in suspension showed that our samples consist of nanometric particles with elongated morphology. The SEM micrographs of HAp and 5SmHAp coatings pointed out that the coatings are continuous and homogeneous. The surface morphology of the 5SmHAp coatings was also assessed by Atomic Force Microscopy (AFM) studies. The AFM results emphasized that the coatings presented the morphology of a uniformly deposited layer with no cracks and fissures. The crystal structure of 5SmHAp coating was characterized by X-ray diffraction (XRD). The surface composition of 5SmHAp coating was analyzed by X-ray photoelectron spectroscopy (XPS). The XRD and XPS analysis shown that the Sm(3+)ions have been incorporated into the 5SmHAp synthesized material. The antifungal properties of the 5SmHAp suspensions and coatings were studied usingCandida albicansATCC 10231 (C. albicans) fungal strains. The quantitative results of the antifungal assay showed that colony forming unity development was inhibited from the early phase of adherence in the case of both suspensions and coatings. Furthermore, the adhesion, cell proliferation and biofilm formation of theC. albicanswere also investigated by AFM, SEM and Confocal Laser Scanning Microscopy (CLSM) techniques. The results highlighted that theC. albicansadhesion and cell development was inhibited by the 5SmHAp coatings. Moreover, the data also revealed that the 5SmHAp coatings were effective in stopping the biofilm formation on their surface. The toxicity of the 5SmHap was also investigated in vitro using HeLa cell line.

This study develops, for the first time, composite coatings based on silver and zinc doped hydroxyapatite in chitosan matrix (AgZnHApCs). The AgZnHApCs composite coatings were prepared by dip coating method. The hydroxyapatite (HAp), biocompatible material for regenerating and strengthening damaged bones were doped with silver and zinc ions and coated with chitosan in order to produce a uniform and homogenous coating with biocompatibility and antimicrobial properties. The stability of AgZnHApCs suspensions was evaluated by ultrasound measurements. The value of stability parameters of AgZnHApCs suspension is in good agreement with the value of bidistilled water used as reference fluid. Homogeneously dispersed solutions of AgZnHApCs were synthesized to endeavor to optimize the physico-chemical and biological characteristics of the coatings obtained at room temperature. The AgZnHApCs composite suspension and coatings were analyzed using various investigation techniques, such as X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenylte-2H-tetrazolium bromide) assay and antimicrobial studies. The optical spectroscopy, atomic force microscopy (AFM), metallographic examination and X-ray photoelectron spectroscopy (XPS) on AgZnHApCs composite coatings were also conducted. Cell culture and MTT assays demonstrate that AgZnHApCs composite suspension and coatings have no negative effect on the cell viability and proliferation. The cell morphology was not affected in presence of AgZnHApCs composite suspension and coatings. The antimicrobial assays conducted againstStaphylococcus aureusATCC 25923,Escherichia coliATCC 25922, andCandida albicansATCC 90029 microbial strains revealed that both the AgZnHApCs composite suspension and coatings exhibited great antimicrobial properties.

The first electrochemical immunosensor for the determination of the 20S proteasome (P20S) was developed, entailing the immobilization of an antibody on an aminophenylboronic/poly-indole-6-carboxylic acid-modified electrode. The proposed electrochemical bioplatform is a simple and feasible analytical tool applicable for the determination of P20S in human plasma, considering its high clinical and biological relevance. Cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry (SWV) were used to determine the optimal step-by-step process to obtain the electrochemical immunosensor. The interaction of P20S with the recognition layer of the immobilized antibody on the nanostructured surface took place by incubating the electrode in a P20S solution at 20 degrees C for 2 h. Using SWV as an electro-analytical technique, this immunosensor can quantify P20S. The current was linear with the P20S concentration within two dynamic concentration ranges from 20.0 to 80.0 and 80.0 to 200.0 ng.mL(-1) (r(2) = 0.992 and 0.98, respectively) with a limit of detection and quantification of 6 and 18 ng.mL(-1), respectively. Moreover, the immunosensor showed considerable repeatability and reproducibility, when the determination was done in human serum, which confirms that it is a promising alternative for direct detection of P20S in biological fluids with minimal interference.

Iron oxides such as magnetite and maghemite coated with cetyltrimethylammonium bromide (CTAB) are very promising materials for wastewater treatment because iron oxide can be easily separated from solutions using the magnetic separation procedure Iron oxide (IO) coated CTAB was synthesized by an adapted co-precipitation method. In the present study, the IO-CTAB was used for removing arsenic from water for the first time. In the present study, the performance of iron oxide coated CTAB biocomposites as an adsorbent for arsenic removal from aqueous solutions was examined. X-ray diffraction (XRD) analysis and the results revealed a cubic phase Fd-3 m of Fe(3)O(4)with lattice a = 8.40 angstrom and average crystal size equal to 17.26 +/- 3 nm. The mean particle size calculated from transmission electron microscopy (TEM) was 19.86 +/- 1.7 nm. The results of the adsorption batch experiments and the data determined using the Langmuir and Freundlich models emphasized that IO-CTAB nanoparticles were favorable for the adsorption of As(III) ions from aqueous solutions. Ultrasound measurements have shown that IO-CTAB is a cost-effective biocomposite for removing arsenic from contaminated solutions. Moreover, x-ray photoelectron spectroscopy (XPS) has shown that during the process of arsenic absorption, there is oxidation from As(III) to As(V), which leads to a decrease in toxicity during this process. The results of the cytotoxic assays confirmed that the IO-CTAB nanoparticles did not induce any morphological changes in the HeLa cells and did not affect their proliferation after 24 h of incubation.

Polymer-based nanocomposites have recently received considerable attention due to their unique properties, which makes them feasible for applications in optics, sensors, energy, life sciences, etc. The present work focuses on the synthesis of nanocomposites consisting of a polytetrafluorethylene-like matrix in which metallic nano-silver are embedded, by using multiple magnetron plasmas. By successively exposing the substrate to separate RF magnetrons using as combination of target materials polytetrafluorethylene (PTFE) and silver, individual control of each deposition process is insured, allowing obtaining of structures in which silver nanoparticles are entrapped in-between two PTFE layers with given thicknesses. The topographical and morphological characteristics investigated by means of Scanning Electron Microscopy and Atomic Force Microscopy techniques evidenced the very presence of Ag nanoparticles with typical dimension 7 nm. The chemical composition at various depositing steps was evaluated through X-ray Photoelectron Spectroscopy. We show that the presence of the top PTFE layer prevents silver oxidation, while its thickness allows the tailoring of optical properties, as evidenced by spectroellipsometry. The appearance of chemical bonds between silver atoms and PTFE atoms at interfaces is observed, pointing out that despite of pure physical deposition processes, a chemical interaction between the polymeric matrix and metal is promoted by plasma.