Ulugbek Shaislamov

Facile fabrication and photoelectrochemical properties of a CuO nanorod photocathode with a ZnO nanobranch protective layer

In this study, the photoelectrochemical properties of CuO/ZnO photoelectrodes fabricated with nanorod and film structures were investigated and compared, and the effect of surface morphology on their photoelectrochemical performance was discussed in detail. The experimental results demonstrated that the CuO/ZnO photoelectrode with nanorod structures showed superior photoelectrochemical properties compared to that of the photoelectrode with the film structure. The electrochemical impedance analysis and UV-vis spectroscopy results confirmed that the hierarchical nanorod-like structure of the CuO/ZnO photoelectrode was advantageous for effective light absorption, and reduced charge transfer resistance at the electrode/electrolyte interface. At the same time, the ZnO layer effectively contributed to the suppression of photocorrosion in the CuO, and the photoelectrodes with a ZnO layer demonstrated 82.13% better stability in photoelectrochemical conditions.

High-frequency underwater plasma discharge application in antibacterial activity

Plasma discharge is a novel disinfection and effectual inactivation approach to treat microorganisms in aqueous systems. Inactivation of Gram-negative Escherichia coli (E. coli) by generating high-frequency, high-voltage, oxygen (O2) injected and hydrogen peroxide (H2O2) added discharge in water was achieved. The effect of H2O2 dose and oxygen injection rate on electrical characteristics of discharge and E. coli disinfection has been reported. Microbial log reduction dependent on H2O2 addition with O2 injection was observed. The time variation of the inactivation efficiency quantified by the log reduction of the initial E. coli population on the basis of optical density measurement was reported. The analysis of emission spectrum recorded after discharge occurrence illustrated the formation of oxidant species (OH•, H, and O). Interestingly, the results demonstrated that O2 injected and H2O2 added, underwater plasma discharge had fabulous impact on the E. coli sterilization. The oxygen injection notably reduced the voltage needed for generating breakdown in flowing water and escalated the power of discharge pulses. No impact of hydrogen peroxide addition on breakdown voltage was observed. A significant role of oxidant species in bacterial inactivation also has been identified. Furthermore the E. coli survivability in plasma treated water with oxygen injection and hydrogen peroxide addition drastically reduced to zero. The time course study also showed that the retardant effect on E. coli colony multiplication in plasma treated water was favorable, observed after long time. High-frequency underwater plasma discharge based biological applications is technically relevant and would act as baseline data for the development of novel antibacterial processing strategies.

Effective control over near band-edge emission in ZnO/CuO multilayered films

We report on a study of the microstructural and photoluminescent properties of ZnO/CuO multilayered films. Multilayered ZnO/CuO thin films were deposited on amorphous SiO2/Si substrates by a pulsed laser technique and their microstructural and optical properties were characterized by transmission electron microscopy (TEM) and photoluminescence spectroscopy. TEM and XRD analyses of annealed ZnO/CuO films reveal the formation of multiple crystallographic defects and modification of the dominant growth plane, indicating effective doping of Cu atoms into the ZnO lattice. Consequently, near-band-edge emission in ZnO can be controlled through the number of CuO layers. Redshift of the near-band-edge emission peak from 385 nm up to 422 nm is achieved by increasing the number of CuO layers up to a certain number, above which a downward shift is observed. The results demonstrate that the emission properties of ZnO can be modified and precisely controlled by incorporation of CuO thin layers as a Cu-doping source.