Graphene Based Sensors for the Detection of DMMP

Abstract

Chemical warfare agents (CWA) pose a severe threat worldwide due to their fatal effects and unstoppable proliferation and manipulation . They come in a large variety among which nerve agents are the most lethal. Therefore, they require strict monitoring in order to seek protection from a potential terrorist attack. Hence, development of a sensor for strict monitoring of these dangerous chemicals is essential but owing to their high toxicity a simulant is used which in our case is DMMP, an organophosphorus compound. In our research I have synthesized various graphene based sensors where graphite was used as a starting material. Two types of graphene based sensing substrates were synthesized, graphene oxide (GO) by Hummers’ method and reduced graphene oxide by reduction of GO. Graphite, GO and RGO were functionalized non-covalently by the attachment of zinc phthalocyanine on the surface of these materials. Resulting materials were characterized using SEM, IR, UV/VIS, XRD, TGA and NMR for surface information, functional groups, crystal structure, stability, topology and chemical structure respectively. Sensing electrodes were fabricated by drop casting method and all the samples were investigated in repeated cycles to check response behavior and other features of the materials. The non covalent hybrid of partially exfoliated graphite and zinc phthalocyanine (PGr/ ZnPc) showed the best result with 42.16 % and worst response was exhibited by mere graphene oxide without any functionalization with 4.6 % efficiency. Not only this but PGr/ ZnPc showed supremacy in the field including recovery, repeatability, drift and response time. The reason behind this lies in the extensively conjugated and defect free structure of the graphite which provided continuous electron transfer in comparison with others. In case of GO the oxygen functionalities are not only insulating on their own but also deprive the sp² character of graphite sheets which interrupts the mobile channels of electrons and decreases sensitivity. Selectivity analysis showed that attachment of phthalocyanine greatly increases sensitivity of DMMP and decrease response towards interfering species.