National Institute Of Materials Physics - Romania

This work presents a new synthesis and characterization of Kesterite Cu2ZnSnS4 films by one step electrodeposition with free sulfurization annealing treatment at different applied potentials. This study highlights the effect of applied potential and annealing treatment on the properties of CZTS deposited films. X-ray Diffraction and Raman spectroscopy were employed to assess the structure and composition of the films elaborated at -1V, -1.1V, and -1.2V vs Saturated Calomel Electrode (SCE). The morphological and optical properties were studied using Scanning Electron microscopy and photoluminescence spectroscopy (PL), respectively. The structural properties are improved by annealing treatment, while -1.1V vs SCE was found to be the optimum applied potential to prepare the Kesterite CZTS thin film with a bandgap around 1.5 eV. (C) 2020 Elsevier B.V. All rights reserved.

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.

Core-double shell nylon-ZnO/polypyrrole electrospun nanofibers were fabricated by combining three straightforward methods (electrospinning, sol-gel synthesis and electrodeposition). The hybrid fibrous organic-inorganic nanocomposite was obtained starting from freestanding nylon 6/6 nanofibers obtained through electrospinning. Nylon meshes were functionalized with a very thin, continuous ZnO film by a sol-gel process and thermally treated in order to increase its crystallinity. Further, the ZnO coated networks were used as a working electrode for the electrochemical deposition of a very thin, homogenous polypyrrole layer. X-ray diffraction measurements were employed for characterizing the ZnO structures while spectroscopic techniques such as FTIR and Raman were employed for describing the polypyrrole layer. An elemental analysis was performed through X-ray microanalysis, confirming the expected double shell structure. A detailed micromorphological characterization through FESEM and TEM assays evidenced the deposition of both organic and inorganic layers. Highly transparent, flexible due to the presence of the polymer core and embedding a semiconducting heterojunction, such materials can be easily tailored and integrated in functional platforms with a wide range of applications.

Post-implant infections are a major health problem, and it is well-known that treating them with conventional drugs is accompanied by many disadvantages. The development of new biomaterials with enhanced antimicrobial properties are of major interest for the scientific world. The aim of this study was to synthesize and characterize hydroxyapatite doped with Samarium (Ca10-xSmx(PO4)(6)(OH)(2), x(Sm) = 0.05, 5Sm-HAp) suspensions, pellets and coatings. The 5Sm-HAp coatings on Si substrates were obtained by rf magnetron sputtering technique. The different techniques such as ultrasound measurements, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Glow Discharge Optical Emission Spectroscopy (GDOES), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to examine the obtained coatings. The results showed that the doped Sm ions entered the structure of hydroxyapatite successfully and Sm ions was uniformly doped onto the surface of the support. The depth profile curves of Ca, P, O, H, Ce and Si elements exhibit their presence from a surface to substrate interface as function of sputtering time. XPS analysis indicated as calcium-phosphate structures enriched in Sm3+ ions. Furthermore, the antimicrobial properties of the 5Sm-HAp suspensions, targets and coatings were assessed against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231. The results of the antimicrobial assays highlighted that that the samples presented a strong antimicrobial activity against the tested microbial strains. The results showed that the coatings after 48 h of incubation inhibited the growth of all tested microbial strains under the value of 0.6 Log CFU/mL. This study shows that the 5Sm-HAp samples are good candidates for the development of new antimicrobial agents.

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.