Fabrication of electrospun Co₃O₄/CuO p-p heterojunctions nanotubes functionalized with HFIP for detecting chemical nerve agent under visible light irradiation

Organic functionalized composite metal oxide nanomaterials are promising for reliable selective and high sensitive gas sensors based on their chemical bonding with the targeted molecules and rapid transport pathways of charges. The selectivity of semiconducting metal oxides (SMOs) still insufficient and its mechanism is not clearly demonstrated, which restricts their application. Herein, hexafluoroisopropanol (HFIP) groups were grafted on the composite Co₃O₄/CuO nanotubes as a hybrid sensing material for detecting dimethyl methylphosphonate (DMMP), sarin nerve agent simulant. Porous composite Co₃O₄/CuO nanotubes were fabricated via electrospun of a polymeric blend as a sacrificial template to construct nanotubes (NTs) based on the phase separation property. The designed hybrid HFIP-Co₃O₄/CuO NTs showed high response (8.8 Rg/Ra at 90 °C), rapid response (7.3 s)-recovery (5.2 s) times and excellent selectivity to 0.5 ppm DMMP under light irradiation compared to un-functionalized sample and the response in dark, indicating to the specific bonding between HFIP and DMMP via hydrogen bonds and photo-generation of charge carriers. The hybrid sample showed high reversibility and humidity independence under light, approving the repeatability of the chemisorption processes and the hydrophobic behavior of HFIP groups. The enhanced DMMP detection is attributed to the photoactivation of p-p heterojunctions Co₃O₄/CuO NTs and HFIP functionalization.