Highly selective detection of dimethyl methylphosphonate (DMMP) using CuO nanoparticles /ZnO flowers heterojunction

Here we report the fabrication of high surface area CuO nanoparticles (NPs) on micron-scale ZnO (CuO/ZnO) “flowers” with dimethyl methylphosphonate (DMMP) gas sensing capabilities. The formation of CuO NPs/ZnO heterojunction structures was confirmed by PXRD and TEM analyses. The gas sensing properties of the CuO NPs/ZnO structures showed a faster response time (26.2 s) compared to the exclusively ZnO-based sensor (330 s). The heterojunction sensors demonstrated the highest selectivity in 10 ppm DMMP, reaching the high value of 626.21 at 350 °C. This CuO NPs/ZnO heterojunction structure provides an extension of the depletion layer and an increase of the resistance (R_a) in air, leading to a reduction of the depletion layer and resistance (R_g) when exposed to reducing DMMP gas. The higher surface area (6.0 m²/g) of the CuO/ZnO heterojunction structure with a 0.5 h synthesis time of the ZnO flowers further promoted the adsorption kinetics for the reaction between C₃H₉O₃P and O²⁻ when exposed to DMMP, thus enhancing its sensing properties.