A field-deployable multimodal device integrated with paper strips and LIG platforms for rapid optical and electrochemical detection of organophosphate nerve-agent simulants

Abstract

Organophosphorus (OP) nerve agents, including diethylchlorophosphate (DCP) and diethylcyanophosphate (DCNP), present persistent threats to both human health and environmental safety. The sustainable detection and detoxification of these highly toxic compounds remain a critical global challenge. In this study, we introduce a triphenylamine-bis(indolyl)methane (TPA-BIM, referred to as probe 1)-based probe capable of detecting and differentiating two structurally similar nerve-agent mimics, diethylchlorophosphate (DCP) and diethylcyanophosphate (DCNP), in semi-aqueous media. The probe self-assembles into nanoscopic aggregates in aqueous environments, yielding emission from monomeric and aggregated species. Upon exposure to DCP, rapid hydrogen-bond-assisted aggregation induces a ∼21.5-fold fluorescence ‘turn-on’ response, a distinct pink-to-purple colorimetric change, with a low detection limit of 0.14 µM. In contrast, DCNP elicits only weak aggregation and minimal fluorescence modulation, permitting unambiguous differentiation. Additionally, the probe also promotes hydrolytic conversion of DCP to diethyl phosphoric acid, an environmentally benign product, thereby providing sustainable remediation of toxic nerve-agent simulants. Beyond optical sensing, the analytical scope of the probe was expanded to electrochemical detection by immobilising it on laser-induced graphene (LIG) electrodes, which provided sensitive and interference-resistant electrochemical sensing. Additionally, pre-coated paper strips and dipstick assays allowed rapid, portable, colorimetric and vapour-phase detection of DCP. Collectively, this multimodal sustainable platform provides a scalable, water-compatible approach for real-time monitoring and detoxification of organophosphorus contaminants in environmental and defence applications.