Ultrasensitive Detection of Dimethylamine Gas for\nEarly Diagnosis of Parkinson’s Disease Using CeO<sub>2</sub>‑Coated Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene/Carbon Nanofibers

Parkinson’s\ndisease is a prevalent neurological disorder,\nwith dimethylamine (DMA) recognized as a crucial breath biomarker,\nparticularly at the parts per billion (ppb) level. Detecting DMA gas\nat this level, especially at room temperature and high humidity, remains\na formidable challenge. This study presents an ultrasensitive chemiresistor\nDMA gas sensor, leveraging the CeO<sub>2</sub>-coated Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene/carbon nanofiber\n(CeO<sub>2</sub>/MXene/C NFs) heterostructure to enhance dimethylamine\nsensing. The high conductivity of MXene, combined with C–Ti–O\nbonds and a sp<sup>2</sup> hybridized hexagonal carbon structure,\nincreases surface active sites. The presence of Ce<sup>3+</sup> promotes\nthe formation of surface-active oxygen species, while the MXene-CeO<sub>2</sub> heterojunction broadens the electron depletion layer. Theoretical\ncalculations reveal that the highest adsorption energy for DMA gas\nis at the Ce top site, explaining the sensor’s satisfactory\nsensitivity, rapid response and recovery process, low detection limit\n(5 ppb), and high selectivity at room temperature. The Ce<sup>3+</sup>/Ce<sup>4+</sup> dynamic self-refresh mechanism, involving surface\nhydroxyl elimination, enhances the sensor’s performance under\nhigh-humid conditions. Clinical breath tests demonstrate the sensor’s\nability to distinguish between healthy individuals and Parkinson’s\ndisease patients, paving the way for developing next-generation sensors\nfor early diagnosis of neurological disorders.