Green Synthesis and Characterization of a ZnO-ZrO2 Heterojunction for Environmental and Biological Applications

The zinc oxide–zirconium dioxide (ZnO-ZrO2) heterojunction was prepared by a green method using rubber leaves as reducing and capping agents. Various physicochemical techniques were used to study the chemical composition and the structural and optical properties of the synthesized nanocomposite. The nature of the heterojunction was confirmed through X-ray diffraction and the average sizes of ZnO and ZrO2 crystallites were found to be 70 and 24 nm, respectively. The photocatalytic potential of the ZnO-ZrO2 heterojunction was examined against rhodamine 6G (Rh-6G), and 97.30 percent of the dye was degraded due to the synergistic effect of the light and the catalyst. The commercial ZnO nanopowder was used as a reference catalyst and 86.32 percent degradation was noted under the same reaction conditions. The in vitro antioxidant activity was also performed to scavenge the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals, where the activity of the ZnO-ZrO2 heterojunction was found to be higher than the ascorbic acid.

Enhancement of the Photocatalytic Activity of ZnO Nanoparticles and the Relationship With Thermal Annealing Temperature

The present study describes the synthesis, characterization, and photocatalytic activity (PCA) evaluation of ZnO nanoparticles (NPs) prepared via the polymeric precursor method in a first step, following annealing in the range of 500 to 900 oC in a second step. The formation of the wurtzite crystal structure is confirmed via x-ray diffraction data analysis. Thermal annealing treatments in atmospheric air are carried out to control the crystallite mean size and physical properties. The UV-Vis spectroscopy measurements show a decreasing trend of the optical band gap of the as-fabricated ZnO NPs, from ~3.4 eV to ~3.1 eV, as the annealing temperature increases. The PCA of the ZnO NPs against methylene blue dye revealed an increase in efficiency as the annealing temperature increases, reaching with a maximum performance for the sample annealed at ~700 °C. Our findings suggest that the PCA of the ZnO NPs does not show a straightforward dependence on the NPs’ size, but it seems to be correlated with the density of defects, such as oxygen vacancies, which are modulated by the annealing temperature. In addition, thermoluminescence glow curves exhibit a well-defined peak located at ~622 K for the as-prepared ZnO nanopowder. The peak intensity shows a decreasing trend with the annealing temperature up to ~700 °C. This result is correlated with the modulation of traps as the annealing temperature increases, which seems to be directly related to the amount of trapped charges (electrons and holes), leading to a marked reduction of the PCA.

Structural, Linear and Nonlinear Optical Properties of Some Al-free and Al-doped ZnO Nanopowder Samples

This research work aims to prepare and characterization some Al-doped ZnO nanoparticles. The co-precipitation method was used for preparing the desired samples, where ZnO replaced by AlCl3. Then the resulted materials were characterized and their structural phases identified using the XRD technique, where eight crystalline phases were identified and then assigned to some of the interatomic planes, (100), (002), (101), (102), (110), (103), (112), and (201). Both the average crystalline size and the micro-strain were calculated for each sample, where it was found that both of them increase when Ai-content increases. UV-vis spectra showed an absorption peak centered at 3.34 eV which represents the optical bandgap of ZnO. Al-Impurities acted to improve and increase the value of the optical transmittance, especially in the visible light region. The increase of Al-content influenced, where their values increase when AL-content increases. the value of the calculated nonlinear refractive index may be considered promising for different optoelectronic applications.

Synthesis, characterization and application of a bio-derived ZnO nano-powder from spinacia oleracea leaf extract for the removal of BOD and COD from tannery wastewater

Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) as biological and chemical pollutants of wastewater are renowned environmental problems. A study of the performance of BOD and COD degradation via adsorption was undertaken using Bio-derived ZnO nanopowder (ZnO-NP), synthesized using leaf extract of Spinacia oleracea, and Zn (NO3)2 at 500 0C, following a simple and green approach. XRD, SEM, FTIR, EDS and BET analysis were used to characterize the nano-adsorbent. EDS spectrum recorded elemental weight compositions of 67.33% and 32.67% for Zn and O, while the FTIR absorption peaks revealed the presence of Zn-O–H and Zn-O. Surface area analysis revealed the mesoporous structure of the ZnO-NPs. The reduction efficiency of the ZnO-NPs was evaluated in the presence of raw tannery wastewater by application of treatment time and adsorbent dosage as parametric factors; results obtained were compared to environmental regulatory limits (WHO and NESREA). Contact times reported removal efficiencies of 81.5-90.8 % and 12.8-50 % for BOD and COD, while adsorbent dosage-influenced BOD and COD removal at an optimum contact time of 30 minutes was found to be 79.2 - 97.5 % and 27.8 to 55.6 % respectively. This study reveals that ZnO nanopowder is better applied as BOD reductants over COD for spent tan liquor.

Wettability, Thermal Stability, and Antibacterial Properties of Polycaprolactone /ZnO Nanocomposites in Packaging

Polycaprolactone is one of the natural biodegradable polymers mainly used in bioplastics production for packaging, usually composed of non-toxic compounds and biodegradable. The aim was to examine the role of zinc oxide (ZnO) nanopowder on the,wettability , thermal and anti-bacterial effect nanocomposites. Pure PCL and PCL-based bio- nanocomposites doped with various ratios of ZnO nanoparticles from 0% to 5wt% were prepared through the arrangement of throwing procedure. The results show that wettability properties in relation to ideal PCL and that they were increasingly hydrophobic from 57º.8 to 69º.53 because add ZnO nanocomposites,the thermal stability between 300 and 400 ° C makes them perfect for the application of food packaging application. Also, anti-bacterial screening against Gram-positive and Gram-negative microorganisms, which was highly variable and evident in comrades, was compared with PCL.

Utilization of Zinc Oxide Nanopowder for Photocatalytic Removal of Pb++ Ions from Aqueous Wastewater

Nanometer-sized zinc oxide powders were prepared with a “solution-combustion method (SCM).” This method used zinc oxide nanopowder as a semiconductor oxide catalyst to initiate light-induced redox reactivity in the presence of 150 ppm aqueous lead-ethylenediaminetetraacetic acid solution (Pb-EDTA) for photocatalysis under UV illumination. Removal rates of lead ions in the aqueous Pb-EDTA solution using SCM ZnO powder were compared with those of two other titanium dioxide photocatalysts, P-25 TiO2-powder (Degussa) and rutile TiO2 powder, prepared via a homogeneous precipitation process at low temperature (HPPLT). Using SCM ZnO nanopowder, complete removal of lead ions from the aqueous Pb-EDTA solution was observed within 25 min after UV irradiation. However, HPPLT TiO2 powder and P25 TiO2 powder took almost 45 and 65 minutes to completely remove the lead ions, respectively. Thus, lead ions removal efficiency of SCM ZnO nanopowder is at least twice higher than the efficiency of the other two titanium dioxide photocatalysts investigated.