Ultrasensitive\nIn<sub>2</sub>O<sub>3</sub>‑Based\nNanoflakes for Lung Cancer Diagnosis and the Sensing Mechanism Investigated\nby <i>Operando</i> Spectroscopy

Rapid gas sensing with high sensitivity and selectivity\nis pivotal\nin advanced production, in smart living, and increasingly in medical\nhealth applications. This study presents a novel Pt@InNiO<sub><i>x</i></sub> nanoflake isoprene sensor that achieves an exceptionally\nlow limit of detection (LOD) at 2 ppb, the lowest reported for isoprene\nsensors to date. Notably, it exhibits high selectivity and remarkable\nantihumidity capacity, thus meeting the stringent requirements for\nlung cancer screening. To unravel the sensing mechanism, we fabricate\nan <i>operando</i> DRIFTS-Raman cell coupled to online electrical\nmeasurements. It reveals that the ultrasensitive performance of Pt@InNiO<sub><i>x</i></sub> nanoflakes stems from the activated conjugated\nstructure of isoprene by Pt nanoclusters and from the enhanced isoprene\nadsorption and electron interaction due to the nanoflake morphology.\nThe <i>p-n</i> junction constructed by doping Ni maintains\nFermi level equilibrium, shielding it from humidity interference.\nPractically, we integrate these ultrasensitive Pt@InNiO<sub><i>x</i></sub> nanoflakes into a miniaturized portable electronic\ndevice that successfully distinguishes lung cancer patients with expiratory\nisoprene below 40 ppb, from the healthy population with isoprene above\n60 ppb, enabling an accurate diagnosis in clinics. Our work not only\nprovides a breakthrough in low-cost, noninvasive cancer screening\nthrough breath analysis but also advances the rational design of cutting-edge\ngas sensing materials.