Selective dual detection of hydrogen sulfide and methyl mercaptan using CuO/CuFe₂O₄ nanopattern chemiresistors

Volatile sulfur compounds (VSCs), such as H₂S and methyl mercaptan (MM), are malodorous and harmful gases. H₂S and MM share analogical origins. However, they should be discriminated because of their different odor thresholds and health impacts. Herein, a nanopattern chemiresistor composed of aligned CuO-loaded CuFe₂O₄ nanofibers was prepared via direct-write near-field electrospinning. The CuO/CuFe₂O₄ sensor with the atomic ratio of [Cu]:[Fe] = 3:4 exhibited extremely high responses to ppm-level H₂S and MM compared with other nanopattern sensors with different compositions ([Cu]/[Fe] = 2:4, 4:4, and 0:1). This can be attributed to the gas-accessible morphology of the nanopattern sensor, the formation of a nanoscale p(CuO)-n(CuFe₂O₄) junction, and the intimate reaction between the discretely loaded CuO nanoparticles and the VSCs. Furthermore, the CuO/CuFe₂O₄ sensor exhibited high selectivities to H₂S and MM at 200 ℃ and 400 ℃, respectively. The selective dual detection of H₂S and MM using a single CuO/CuFe₂O₄ sensor via the simple modulation of the sensing temperature opens a new route for indoor air quality monitoring, ventilation control, halitosis diagnosis, and wine quality monitoring.