Porous graphene oxide-metal ion composite for selective sensing of gaseous organophosphates

Organophosphates are used as agricultural pesticides, and also encountered as toxic nerve agents in chemical warfare. Accordingly, the development of sensors for detection and monitoring organophosphate vapors has been highly sought. We present a new capacitive gas sensor exhibiting remarkable specificity and sensitivity towards organophosphates. The capacitive platform comprises a composite matrix of cobalt or nickel ions intercalated within porous graphene oxide, prepared through a simple procedure. We demonstrate that the porous graphene oxide metal ion composite undergoes fast capacitance changes only upon exposure to organophosphate vapors. Moreover, the sensor exhibits extraordinary sensitivity – displaying up to 34,000 % capacitance change upon interactions with triethyl-phosphate, a common pesticide constituent. Detailed mechanistic analyses, carried out also utilizing porous graphene oxide coupled to other metal ions, revealed that the significant sensing performance of Co²⁺ or Ni²⁺ / porous graphene oxide systems likely arises from the distinct modes of ion incorporation within the porous matrix, and ready substitution of complexed water ligands with organophosphate molecules. The new metal ion / porous graphene oxide capacitive sensor may be employed for practical applications including alerting and monitoring organophosphate gases in different environments.