Enhanced photocatalytic activity of Ag-coated ZnO nanorods for the degradation of methylene blue

Worldwide water pollution is a serious issue, which needs special attention. Among these pollutants, methylene blue (MB) is dangerous for aquatic life as well as for human beings. Researchers are trying their best to degrade the various pollutants found in water. In the present work, we synthesized ZnO nanorods (NRDs) by one-step hydrothermal method. The synthesized samples were then characterized with the help of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). ZnO nanostructures were composed of rod-shaped NRDs with flat edges and were highly crystalline with hexagonal shaped morphology. UV/Visible spectroscopy was carried out to investigate the optical properties, which shows the absorption in UV range and highly transmittance in the visible range. Finally, the photocatalytic activity was performed for the degradation of MB. The results show that MB was not fully degraded by bare ZnO NRDs. After all, we coated Ag NPs on the surfaces of ZnO NRDs through the simple solution-based method. The UV/Visible data reveal absorption in the UV as well as in the visible range due to the surface plasmonic effect of Ag NPs. Hybrid Ag-coated ZnO NRDs successfully degraded MB within 60 min. Therefore, we found that Ag-coated ZnO NRDs show good photocatalytic properties as compared to uncoated ZnO NRDs.

PbS Quantum Dots Decorating TiO2 Nanocrystals: Synthesis, Topology, and Optical Properties of the Colloidal Hybrid Architecture

Fabrication of heterostructures by merging two or more materials in a single object. The domains at the nanoscale represent a viable strategy to purposely address materials’ properties for applications in several fields such as catalysis, biomedicine, and energy conversion. In this case, solution-phase seeded growth and the hot-injection method are ingeniously combined to fabricate TiO₂/PbS heterostructures. The interest in such hybrid nanostructures arises from their absorption properties that make them advantageous candidates as solar cell materials for more efficient solar light harvesting and improved light conversion. Due to the strong lattice mismatch between TiO₂ and PbS, the yield of the hybrid structure and the control over its properties are challenging. In this study, a systematic investigation of the heterostructure synthesis as a function of the experimental conditions (such as seeds’ surface chemistry, reaction temperature, and precursor concentration), its topology, structural properties, and optical properties are carried out. The morphological and chemical characterizations confirm the formation of small dots of PbS by decorating the oleylamine surface capped TiO₂ nanocrystals under temperature control. Remarkably, structural characterization points out that the formation of heterostructures is accompanied by modification of the crystallinity of the TiO₂ domain, which is mainly ascribed to lattice distortion. This result is also confirmed by photoluminescence spectroscopy, which shows intense emission in the visible range. This originated from self-trapped excitons, defects, and trap emissive states.

New insights into electronic and geometric effects in the enhanced photoelectrooxidation of ethanol Using ZnO nanorod/ultrathin Au nanowire hybrids

Oxidation of small organic molecules in a fuel cell is a viable method for energy production. However, the key issue is the development of suitable catalysts that exhibit high efficiencies and remain stable during operation. Here, we demonstrate that amine-modified ZnO nanorods on which ultrathin Au nanowires are grown act as an excellent catalyst for the oxidation of ethanol. We show that the modification of the ZnO nanorods with oleylamine not only modifies the electronic structure favorably but also serves to anchor the Au nanowires on the nanorods. The adsorption of OH(-) species on the Au nanowires that is essential for ethanol oxidation is facilitated at much lower potentials as compared to bare Au nanowires leading to high activity. While ZnO shows negligible electrocatalytic activity under normal conditions, there is significant enhancement in the activity under light irradiation. We demonstrate a synergistic enhancement in the photoelectrocatalytic activity of the ZnO/Au nanowire hybrid and provide mechanistic explanation for this enhancement based on both electronic as well as geometric effects. The principles developed are applicable for tuning the properties of other metal/semiconductor hybrids with potentially interesting applications beyond the fuel cell application demonstrated here.