Porous Graphene Oxide-Metal Ion Composite for Selective Sensing of Organophosphate Gases.

: Organophosphates are used as agricultural pesticides, and also encountered as toxic nerve agents in chemical warfare. Accordingly, development of sensors for detection and monitoring organophosphate vapors is highly sought. We present a new capacitive gas sensor exhibiting remarkable specificity and sensitivity towards the organophosphate nerve gas simulants triethyl-phosphate (TEP), dimethyl methyl phosphate (DMMP), and the pesticide dichlorvos (DDVP). Specifically, the capacitive sensor comprises a composite porous graphene oxide matrix intercalating cobalt or nickel ions, prepared through a simple freeze-drying procedure. We demonstrate that the porous graphene oxide/metal ion electrode undergoes fast capacitance changes only upon exposure to organophosphate vapors. Moreover, the sensor exhibits extraordinary sensitivity upon interactions with triethyl-phosphate. Detailed mechanistic analyses, carried out in comparison to porous graphene oxide coupled to other transition metal ions, reveals that the remarkable sensing properties of the Co2+ or Ni2+ / porous graphene oxide systems likely arise from the distinct mode of metal ion incorporation within the graphene oxide host matrix, and substitution of metal-complexed water ligands with organophosphate molecules. The new metal ion / porous graphene oxide capacitive sensor may be employed for alerting and monitoring organophosphate gases in different environments.