Dendrimer Precursors for Nanomolar and Picomolar Real‐Time Surface Plasmon Resonance/Potentiometric Chemical Nerve Agent Sensing Using Electrochemically Crosslinked Ultrathin Films

Abstract

Abstract Nanomolar detection and specific recognition of pinacolyl methylphosphonate (PMP), a hydrolysis product and an analog of a relatively persistent class of toxic nerve agents, has been achieved. In addition, picomolar sensitivity is observed with methylphosphonic acid (MPA), an end‐hydrolysis product for all organophosphate‐based nerve agents. This is achieved using a combined surface plasmon resonance (SPR) and potentiometry setup. A modified polyamidoamine (PAMAM) carbazole/Cu 2+ dendrimer, which is electrochemically crosslinked on a self‐assembled monolayer (SAM) modified Au substrate, is used as an active sensing element for trapping the nerve‐agent analogs. The ultrathin films have been used to study the anchoring of nerve agents via non‐covalent interactions. The carbazole to amine ratio is optimized to ensure free primary amines are available to interact with the analyte and the Cu 2+ ions present in the system, which further enhances the selectivity. The carbazole group on the periphery serves a dual purpose: crosslinking the dendrimers to form a conjugated network film, and generating the potentiometric response. The adsorption kinetics are monitored by using an in situ SPR/potentiometric setup. This technique not only offers a real‐time dual detection of highly toxic nerve‐agent analogs, but also shows viability for future sensor‐device applications.