Foxtail millet husk as an innovative biomass in the preparation of silica-silver composite with antimicrobial and free radicle scavenging activities

The crop, Foxtail millet is rich in dietary fibres and proteins with low glycaemic index. Hence it qualifies as a regular food in the Indian diet. This has raised the importance of the millet in increased agricultural production. The husk is a waste that can be effectively utilised. Opaline silica is present as phytoliths in the spikelet of the husk. This can be solubilized and precipitated out. In this work, opaline silica was converted to sodium silicate and the composite was precipitated at a pH of 4 using the sol–gel technique. The amount of silica was first quantified using XRF. The results obtained from XRF correlated well with those obtained from thermogravimetric analysis (TGA). The chemical groups are identified using IR spectroscopy. The phase identification of opaline silica and silver was done by powder X-ray diffractometry. The morphological characterization of the composite revealed an irregular structure with particle dimensions of 1.880 μm to 10.82 μm. EDX analysis showed the existence of silver and silicon. Prepared composite was tested for anti-microbial action against five pathogens and was found to be comparable with antibiotics ciprofloxacin and ampicillin. The composite also presented outstanding scavenging action against 5 radicals with BHT as a standard.