Detection of TNT in sulfuric acid solution by SiNWs-FET based sensor

Since the preparation of TNT is always proceeded in acid solution, it is very difficult to accurately detect it at the production stage. Developing a TNT sensor which can work in sulfuric acid solution will be very helpful. This paper presents a TNT sensor based on SiNWs-FET which can quickly detect TNT in sulfuric acid. The detection mechanism is based on the fact that TNT molecules can selectively bond to the amino group of nanowires, which act as grid elements and modulate the conductance of the silicon nanowires, leading to the variation of SiNWs-FET drain-source current. The SiNWs-FET devices were fabricated on a (111) silicon-on-insulator wafer using controllable silicon anisotropy etching and self-limiting oxidation. The silicon nanowires were treated with oxygen plasma and 3-aminopropyltriethoxysilane (APTES) to form hydroxyl and amino groups on the surface of the nanowires, respectively. The SiNWs-FET sensor demonstrated highly sensitive detection to TNT molecule in aqueous solution with 0.1% dimethyl sulfoxide (DMSO) and sulfuric acid solutions. These experimental results show that the SiNWs-FET sensor can work stably and reliably in some harsh environment, even in high concentration of sulfuric acid. The rapid response time also reflected the advantages of SiNWs-FET sensors in TNT fast detection. In addition, the SiNWs-FET sensor showed selectivity to TNT, due to the specific bind between amino groups and nitro groups.