National Institute Of Materials Physics - Romania

ZnO crystallites were grown by electroless deposition on poly(methyl methacrylate) (PMMA) fiber mats prepared by an electrospinning technique. The electroless deposition involves three steps: sensitization, activation and deposition, which were performed by subsequently dipping the PMMA fiber mats in the appropriate solutions. After the deposition the PMMA fibers are uniformly coated with ZnO prisms which show hexagonal wurtzite structure and optical signatures (band-gap value and emission bands) typical for this semiconductor. By combining electroless deposition and electrospinning, different semiconductor coated polymer fibers can be obtained for a wide range of applications. Both methods are appropriate for large scale production, being scalable, cheap, efficient and suitable for large-area covering techniques. (C) 2014 Elsevier B.V. All rights reserved.

ZnO complex microstructures were deposited onto interdigitated metallic electrodes by electrospraying. Simple methods, such as wet chemical precipitation and optical lithography, were used for the synthesis of flower-like and snowflake-like ZnO structures and for the preparation of interdigitated metallic electrodes, respectively. The electrosprayed ZnO particles preserve the structural, optical and morphological properties of the chemically synthesized ZnO powders. During the electrospraying process, the ZnO microstructures form bridges between the interdigitated metallic electrodes leading to electrical contacting. Changes in the electron transport through the ZnO microstructures are evidenced by their exposure to ammonia or their passivation with poly(methyl methacrylate). Merging such easy-scalable and low-cost techniques, devices based on electrosprayed complex ZnO structures can be designed.

The main purpose of this study was to evaluate the inhibitory effect of glycerol- iron oxide thin films on Methicillin-Resistant Staphylococcus aureus (MRSA). Our results suggest that glycerol-iron oxide thin films could be used in the future for various biomedical and pharmaceutical applications. The glycerol-iron oxide thin films have been deposited by spin coating method on a silicon (111) substrate. The structural properties have been studied by X-ray diffraction (XRD) and scanning electron spectroscopy (SEM). The XRD investigations of the prepared thin films demonstrate that the crystal structure of glycerol-iron oxide nanoparticles was not changed after spin coating deposition. On the other hand, the SEM micrographs suggest that the size of the glycerol-iron oxide microspheres increased with the increase of glycerol exhibiting narrow size distributions. The qualitative depth profile of glycerol-iron oxide thin films was identified by glow discharge optical emission spectroscopy (GDOES). The GDOES spectra revealed the presence of the main elements: Fe, O, C, H, and Si. The antimicrobial activity of glycerol-iron oxide thin films was evaluated by measuring the zone of inhibition. After 18 hours of incubation at 37 degrees C, the diameters of the zones of complete inhibition have been measured obtaining values around 25 mm.

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.

The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag: HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag: HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells.

ZnO nanofibers were obtained by electrospinning a solution of zinc acetate dihydrate and polyvinylpyrrolidone in N, N-dimethylformamide, followed by calcination at 500, 650 or 800 degrees C for 1 h. X-ray diffraction, selected area electron diffraction, scanning electron microscopy, transmission electron microscopy, reflectance spectroscopy and photoluminescence spectroscopy were used for the characterization of the resulting fibers. The thermally treated samples exhibit ZnO single phase with polycrystalline hexagonal structure. The morphological investigation revealed an accentuated contraction process during calcination, as well as the increase of the crystallite size and the appearance of a breaking tendency with the calcination temperature enhancement. Both UV and Visible emissions under excitation at 350 nm were showed by the optical studies, which also led to band gap values slightly lower than those reported for similar one-dimensional nanostructures. In order to assess the photocatalytic activity of ZnO fibers, the photodegradation of methylene blue in aqueous medium (10(-3) M) under UV irradiation (368 nm) was analyzed.

Heterostructures with layers from small molecules organic compounds were deposited on ITO/glass substrate by thermal vacuum evaporation (TVE) technique. Structural, optical and morphological investigations were carried out on the realised layers (zinc phthalocyanine-ZnPc, fullerene-C60 and 1,4,5,8-naphthalene-tetracarboxylic dianhydride-NTCDA). The films are polycrystalline keeping the morphological features characteristic to these materials. The prepared heterostructures reveal a large absorption domain in the visible domain. The current-voltage (I-V) characteristics of the investigated structures, recorded in dark, present an improvement in the current value (similar to one order of magnitude) for the standard structure (ITO/PEDOT: PSS/ZnPc/C60/NTCDA/Al) with a supplimentary layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). For the inverted structure (Al/NTCDA/C60/ZnPc/ITO) was also noticed an increased curent value in comparasion with that observed for the standard structure.

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.

We investigate by different complementary methods the processes occurring when a polydimethylsiloxane film is used as interlayer for a silver doped hydroxyapatite coating. The X-ray diffraction and Fourier Transform Infrared Spectroscopy measurements show that the hydroxyapatite doped with silver is in a crystalline form and some SiO44- ions formation takes place at the surface and in the bulk of the new hydroxyapatite doped with silver/polydimethylsiloxane composite layer. The possibility of SiO44- ions incorporation in the structure of silver doped hydroxyapatite by the mechanism of SiO44-/PO43- ions substitution is analysed. The new formed silver doped hydroxyapatite/polydimethylsiloxane composite layer is compact, homogeneous, with no cracks as it was shown by Scanning Electron Microscopy and Glow Discharge Optical Emission Spectrometry.

Samarium doped hydroxyapatite (Sm:HAp), Ca10-xSmx(PO4)(6)(OH)(2) (HAp), bionanoparticles with different x(Sm) have been successfully synthesized by coprecipitation method. Detailed characterization of samarium doped hydroxyapatite nanoparticles (Sm: HAp-NPs) was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The biocompatibility of samarium doped hydroxyapatite was assessed by cell viability. The antibacterial activity of the Sm: HAp-NPs was tested against Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) andGram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus). A linear increase of antimicrobial activity of P. aeruginosa has been observed when concentrations of Sm: HAp-NPs in the samples with x(Sm) = 0.02 were higher than 0.125 mg/mL. For Sm: HAp-NPs with x(Sm) = 0.05 a significant increase of antibacterial activity on E. coli was observed in the range 0.5-1 mg/mL. For low concentrations of Sm: HAp-NPs (x(Sm) = 0.05) from 0.031 to 0.125 mg/mL a high antibacterial activity on Enterococcus faecalis has been noticed. A growth of the inhibitory effect on S. aureus was observed for all concentrations of Sm: HAp-NPs with x(Sm) = 0.02.