Amorphous silica

Rice milling generates a by product know as husk which surrounds the paddy grain. During milling of paddy about 22 % of the weight of paddy is received as husk . This husk is generally used as fuel in the rice mills to generate steam for the parboiling process .This husk contains about 75 % organic volatile matter and the balance 25 % of the weight of this husk can be converted into ash during the firing process. This is known as rice husk ash containing around 85 to 90 % amorphous silica.

Fusarium oxysporum, also referred to as Agent Green, is a fungus. Macroscopic morphology of Fusarium oxysporum may vary significantly on different media. Based upon growth on potato flakes agar at 25°C with on/off fluorescent light cycles of approximately 12 hours each, rapid growth of this is possible. Colonies are initially white and becomes tinged with salmon and lavender at maturity.

Crystalline silica nanoparticles can be obtained by reacting the rice husk with the fungus Fusarium oxysporum which biotransforms the amorphous silica present in rice husk to crystalline silica nanoparticles at room temperature. This leads to an exciting possibility of an energy-conserving and economically viable green approach towards the large-scale synthesis of nanomaterials.