Bio-waste derived reduced graphene oxide (rGO) decorated Cr (III) doped α-Fe2O3 nanocomposite for selective ppm-level acetone sensing at room temperature: Potential approach towards non-invasive diagnosis of diabetic biomarker

Reduced graphene oxide (rGO) was synthesized via reduction of graphitized household tea-waste utilizing neem leaves extract. The synergistic effect of rGO decoration and Cr³⁺ doping within pristine Fe₂O₃ enhanced surface adsorption property, defect density, and oxygen vacancies, facilitating the detection of ppm-levels (1 to 10 ppm) acetone at room temperature. Noticeably, the formation of ‘inversion space-charge-layer’ on sensing material surface at lower operating temperature resulted p-type sensing response using n-type nanomaterial that was transformed to n-type response when the operating temperature was elevated. The maximum sensing response (R_g/R_a) ~ 6.8 towards ~ 10 ppm acetone was obtained from optimized rGO decorated Cr³⁺ doped Fe₂O₃ sensor (FC3R3) at ambient condition. This sensor also revealed a rapid response/recovery time (~ 10 s/ ~ 10 s) and was able to detect as low as ~ 1 ppm acetone. The sensor exhibited improved selectivity towards acetone over other interfering VOCs, attributed to significant dipole moment, low bond dissociation energy, and strong affinity of acetone towards surface-adsorbed oxygenated ions. Notably, the sensor showed negligible deterioration in sensing performance even after ~ 150 days. Furthermore, this sensor was capable to differentiate between acetone concentration in breath sample of healthy and diabetic person for non-invasive diabetes detection.