Fast responding and highly selective chemoresistive humidity sensor based on hydrated V2O5 nanobelts for real-time breath monitoring

Chemoresistive humidity sensors have gained massive attraction owing to the high potential for application in real-time breath monitoring. Herein, we introduce a chemoresistive humidity sensor based on ultrathin V2O5 & sdot;nH2O nanobelts (NBs) prepared by liquid-phase exfoliation. Due to the layered structure, water molecules were embedded between layers, increasing the active surface area. Moreover, the multivalent vanadium states and oxygen vacancies are highly beneficial to increasing the adsorption sites in gas sensing reactions. V2O5 & sdot;nH2O NBs exhibited promising humidity sensing properties examined by exposure to 50% relative humidity (RH). The response and recovery time to 50% RH was 21 s and 356 s, respectively, with stable and reliable sensing behaviors to repetitive exposure to humid air. The response to 50% RH was 27 times higher than the response to interference gas, indicating the outstanding selectivity to humidity. The theoretical detection limit was 0.55% RH, showing linear response increase with humidity concentration. The response degradation was marginal even after 3 weeks of relaxation, showing high stability. The breath monitoring experiment reveals extremely rapid response and recovery to exhaled breath, enlarging the suitability for a real-time breath monitoring platform.