Abstract: In this work, ZnO nanoparticles were prepared by an ultrasonic irradiation method in presence of tetrabutylammonium bromide (TBAB) as surfactant. The nanostructures were characterized by X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDAX) and Transmission Electron Microscopy (TEM). The measurements showed highly crystalline material with ZnO nanostructures size of about 25×100 nm. Their optical properties were also evaluated from UV-vis and photoluminescence (PL) spectra. UV-vis spectroscopy study revealed that as ultrasonic irradiation time increases, there is increase in amount of ZnO nanoparticles formed and also there is a red shift in the absorption edge. PL spectra depicted that the ZnO nanostructures display violet visible light emitting band. The formation of fluorescent nanostructures stable in aqueous media is highly desirable in many potential applications, including biological labels (has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications).

Abstract: In this study, oxidative stress in the bacterial culture of gram negative i.e., Escherichia coli (E. coli), and gram positive i.e., Staphyllococcous aureusS. aureusare studied using bare and glutathione (GSH, reduced) coated ZnO nanoparticles (NPs). ZnO-NPs were synthesized at pH 7.2 through non-aqueous sol-gel method using zinc acetate dihydrate precursors. Reduced glutathione (GSH) was coated on ZnO by physical mixing in a 1:1 ratio. Morphological observations revealed crystalline spherical particles of ∼ 15 nm in size with almost uniform shape and size distribution. The FTIR studies, confirmed GSH coating on ZnO surface evidenced by mixed vibrational bands. Both the bacteria were cultured in Luria-Bertani (LB) media at 37 � C and 160 RPM, with different concentrations of bare ZnO-NPs and GSH-coated ZnO-NPs separately. Minimum Inhibitory Con-centration (MIC) of the ZnO-NPs for E-coli is found as 6 mM and for GSH-coated ZnO-NPs it is 11 mM. However, MIC of ZnO-NP for S-aureus is found as 14 mM whereas that for GHS coated ZnO-NPs it is 26 mM. This means irrespective of the type of bacteria, MIC has increased by ∼ 1.8 times after GHS coating on the ZnO-NPs. This study reveals that ZnO nanoparticles were found to be more toxic due to comparatively high density of reactive oxygen species (ROS) on surface than GSH coated ZnO-NPs i.e., GSH functionalized ZnO-NPs which exhibits effectively lesser oxidative stress to the system. Hence, GSH coated ZnO-NPs exhibits better biocompatibility and reduce the degree of inhibition to the bacterial growth probably because of the presence of thiol group in GSH.