ZnO nanorods produced sonochemically prevented microbial growth, biofilm formation and were nontoxic to mammalian cells. E. coli B. subtilis 0 5 90 92 94 96 98 100Inactive bacteria (%) 2h 5h control 2h 5h control
Sonochemical production of ZnO nanorodsIn this study, we present a simple, fast and cost-effective sonochemical growth method for the synthesis of zinc oxide (ZnO) nanorods. ZnO nanorods were grown on glass substrates at room temperature without the addition of surfactants. The successful coating of substrates with ZnO nanorods were demonstrated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and 10 energy dispersive X-ray spectroscopy (EDS). Antimicrobial properties of ZnO nanorods against the planktonic Bacillus subtilis and Escherichia coli and their respective biofilms were investigated. The cytotoxicity of ZnO nanorods were evaluated using the NIH 3T3 mammalian fibroblast cell line. Moreover, to understand the possible mechanisms of ZnO nanorod toxicity, glutathione oxidation, superoxide production, and release of Zn 2+ ions by the ZnO nanorods were determined, and the 15 LIVE/DEAD assay was employed to investigate cell membrane damage. The results showed that sonochemically grown ZnO nanorods exhibited significant antimicrobial effects to both bacteria and prevented biofilm formation. ZnO nanorods did not present any significant toxicity to fibroblast cells. The main anti-microbial mechanisms of ZnO nanorods were determined to be H 2 O 2 production and cell membrane disruption. 20
The optical properties of InN layers grown by high-pressure chemical vapor deposition have been studied. Raman, infrared reflection, and transmission spectroscopy studies have been carried out to investigate the structural and optical properties of InN films grown on sapphire and GaN/sapphire templates. Results obtained from Raman and IR reflectance measurements are used to estimate the free carrier concentrations, which were found to be varying from mid 1018 to low 1020cm−3. The values for free carrier concentrations are compared to optical absorption edge estimates obtained from optical transmission spectra analysis. The analysis shows that optical absorption edge for InN shifts below 1.1eV as the free carrier concentration decreases to low 1018cm−3.
The influence of substrate polarity on the properties of InN layers grown by high-pressure chemical vapor deposition has been studied. The 2Θ-ω x-ray diffraction scans on InN layers deposited on polar GaN epilayers revealed single-phase InN(0002) with a full width at half maximum (FWHM) of around 200arcsec. InN layers grown on N-polar GaN exhibit larger FWHMs. Rocking curve analysis confirmed single-phase InN for both growth polarities, with FWHM values for ω-RC(002) at 2080arcsec for InN grown on Ga-polar templates. The A1(LO) Raman mode analysis shows higher free carrier concentrations in InN grown on N-polar templates, indicating that polarity affects the incorporation of impurities.
The influence of the growth temperature on the phase stability and composition of singlephase In 1-x Ga x N epilayers has been studied. The In 1-x Ga x N epilayers were grown by high-pressure Chemical Vapor Deposition with nominally composition of x = 0.6 at a reactor pressure of 15 bar at various growth temperatures. The layers were analyzed by x-ray diffraction, optical transmission spectroscopy, atomic force microscopy, and Raman spectroscopy. The results showed that a growth temperature of 925 °C led to the best single phase InGaN layers with the smoothest surface and smallest grain areas.
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