Humidity-independent electronic nose of α-Fe₂O₃/ZnFe₂O₄ heterojunctions for trace detection of N-butanol exhalation in lung cancer screening

Magnetic metal oxide semiconductors (MOSs) are emerging gas-sensing materials. Most researches were devoted to monitoring large-scale gases in industrial emissions, but the trace detection of electronic noses applied in health diagnosis was always ignored. Herein, the humidity-independent α-Fe₂O₃/ZnFe₂O₄ (FZFO) heterojunctions with strong magnetism for N-butanol gas detection were prepared. They may potentially act as electronic noses in early lung cancer screening. This magnetism can endow FZFO to capture more oxygen for redox, and the n-n heterojunctions generated can significantly enhance gas sensitivity, improving the response even under 0.1 ppm at 160 ℃. Furthermore, the limit of detection of the FZFO-4 sample can reach 1 ppb, completely meeting the accuracy requirements. Notably, the humidity independence of FZFO-2 and FZFO-4 samples could maintain at relative humidity 91%, so they will hardly be influenced by water vapor exhaled from patients' mouths. This work first proposed the electronic nose of FZFO heterojunctions in lung cancer screening, which may initiate a wave of non-invasive diagnosis.