Improved method for preparation of anhydrous silica by microwave irradiation with spectroscopic characterization and toxicity assay

Amorphous anhydrous silica SiO2 (mw) (99.99%) is successfully synthesized through microwave irradiation technique and time of reaction is reduced up to 1 h. The dehydration phase study of Si–water, Si–OH, Si–O–Si networking, elemental analysis and surface morphology was carried out by FTIR, FTNIR, SEM and EDAX spectroscopic techniques. The broad absorption stretching and bending of Si–OH and H2O at 3695.38–2832.96 cm− 1, 1638 cm− 1 and 1191.20–1017.14 cm− 1 completely disappeared and appearance of new bands at 946.93 and 797.63 cm− 1 confirmed the amorphous anhydrous silica with Si–O–Si networking. The SEM images of SiO2 (mwc) described the smooth and fine particle texture and confirmed 99.99% Si–O–Si networking of anhydrous silica. The 99.99% purity was verified by EDAX spectra which exhibited sharp signals only for oxygen and silicon. Toxicity against Monomorium minimum and Tribolium castaneum with 100% mortality and LT50 91 min and 7.5 h respectively is being reported. It can be used for long storage of grains in the future.

► Amorphous anhydrous silica is synthesized in 1 h by microwave technique.
► The spectroscopic data verified Si–O–Si networking with 99.99% purity.
► FTIR absorption of Si–OH and H2O at 3695.38–2832.96 cm− 1 completely disappeared.
► SEM/EDAX spectra exhibited sharp signals only for oxygen and silicon elements.
► The % mortality of insects and LT50 is also being reported.