Pulsed Plasma-Chemical Modification of SiO2 Nanopowder by ZnxOy Nanoparticles

This work presents the results of pulsed plasma-chemical modification of silicon dioxide nanopowder with zinc oxide nanoparticles (ZnO@SiO2). The obtained ZnO@SiO2 powders were characterized by transmission electron microscopy (TEM) and X-ray phase analysis. The size of the synthesized particles was in the range of 20–100[Formula: see text]nm. The photocatalytic characteristics of ZnO@SiO2 were studied. When exposed to ultraviolet radiation, the methylene blue (MB) decomposes efficiently. Two samples characterized by the content of silicon tetrachloride in the initial mixture were synthesized. The band gap estimated from the absorption spectra calculated from the diffuse reflectance spectra for these samples was 2.4[Formula: see text]eV and 2.95[Formula: see text]eV for indirect transitions and 3.03[Formula: see text]eV and 3.24[Formula: see text]eV for direct allowed transitions.

Bacterial Compatibility/Toxicity of Biogenic Silica (b-SiO2) Nanoparticles Synthesized from Biomass Rice Husk Ash

Biogenic silica (b-SiO2) nanopowders from rice husk ash (RHA) were prepared by chemical method and their bacterial compatibility/toxicity was analyzed. The X-ray diffractometry (XRD) patterns of the b-SiO2 nanopowders indicated an amorphous feature due to the absence of any sharp peaks. Micrographs of the b-SiO2 revealed that sticky RHA synthesized SiO2 nanopowder (S1) had clustered spherical nanoparticles (70 nm diameter), while b-SiO2 nanopowder synthesized from red RHA (S2) and b-SiO2 nanopowder synthesized from brown RHA (S3) were purely spherical (20 nm and 10 nm diameter, respectively). Compared to the S1 (11.36 m2g−1) and S2 (234.93 m2g−1) nanopowders, the S3 nanopowders showed the highest surface area (280.16 m2g−1) due to the small particle size and high porosity. The core level of the X-ray photoelectron spectroscopy (XPS) spectra showed that Si was constituted by two components, Si 2p (102.2 eV) and Si 2s (153.8 eV), while Oxygen 1s was observed at 531.8 eV, confirming the formation of SiO2. The anti-bacterial activity of the b-SiO2 nanopowders was investigated using both gram-positive (Escherichia coli) and gram-negative (Staphylococcus aureus) microorganisms. Compared to S2 and S3 silica nanopowders, S1 demonstrated enhanced antibacterial activity. This study signifies the medical, biomedical, clinical, and biological importance and application of RHA-mediated synthesized b-SiO2.