A review of sensing technologies for nerve agents, through the use of agent mimics in the gas phase: Future needs

Abstract

Portable gas sensing has become an important technology in preventive and protective measures for users working with the disposal of nerve agents. The use of powerful benchtop instruments is not adequate for those situations where a single individual or a group needs to be informed of the presence of toxic substances and need to implement protection measures. Portable sensors are the right technology that can be used as an early warning system in military operations and for public health. The aim of the work presented in this review is to present a detailed summary of the current sensing technology available within the scientific literature for the detection of nerve agent simulants in the gas phase, focussing on the recognised sarin surrogate: dimethyl methylphonate (DMMP). The use of real chemical warfare agents for testing is highly restricted to government agencies and much of the work is kept secret. The use of simulants for the development of sensing technology has been widely established for nerve agents to reduce the potential risk to personnel and to offer a realistic, simple molecule to try and test the technology. The present review compiles a comparison of different sensors and their respective sensing mechanisms based on different chemical, spectroscopic, or electrochemical and biological properties. These sensing technologies are then compared to the U.S environmental protection agencies standard for concentration of Sarin at 15 ppb (known lethal dose). Surface acoustic wave, quartz crystal microbalance, semiconductor, chemicapacitor and colorimetric sensors have proven to show potential with desirable properties for fast response times and high sensitivity. However, only some work developed using semiconductor detectors present a reliable system able to detect DMMP with low limit of detection (0.05 ppb), fast response time (0.02 min) and good recovery times (0.5 min) and adequate portability that makes them suitable to be integrated in drone systems, wearables, and low-weight devices.