Nanocrystalline Porous silicon for sensitive toxin detection

In this paper, a high-performance nanocrystalline silicon-based impedance sensor has been reported for the sensitive detection of Aflatoxin Bl (AFB1). Nanoporous silicon with pore thickness of about 100 nm and pore diameter of about 250 nm has been fabricated on a 10-20 Ωcm wafer using hydrofluoric acid (HF) and dimethyl sulfoxide (DMSO) using a constant current source of 2.35 rnA for 30 minutes. The samples were then thermally oxidized for partial oxidation of the silicon crystallites to obtain two different oxide thickness of 0.15 μm and 0.05 μm, Next simple screen printed silver electrodes have been fabricated followed by optimized silanization and antibody immobilization. Toxin detection was based on the change in the double layer impedance at the electrode-electrolyte interface caused by specific antigen-antibody binding. The developed sensor has been observed to be highly sensitive, detecting AFB1 of concentration as low as 100 fg/ml with a significant sensitivity of around 40%. Since the proposed method is simple and highly sensitive, it has the potential to detect toxin molecule down to 10 fg/ml.