Low-Temperature Operable Nitric Oxide Sensor Based on Solution-Processed Cs2PdBr6 Perovskite Nanoparticles (Supporting Information)

Nitric oxide (NO) detection is vital for environmental monitoring and medical diagnostics, yet conventional metal oxide gas sensors generally require high operating temperatures. Here, we report a low-temperature NO sensor based on inorganic halide perovskite Cs2PdBr6 nanoparticles synthesized via a mild, solution-based wet-chemical route followed by antisolvent crystallization. The antisolvent process effectively reduced the particle size to several tens of nanometers, enabling a distinct and reversible sensing response to NO even at 100 °C. The sensor exhibited good linearity in the concentration range of 10–150 ppm, a detection limit of 9.25 ppm, and excellent selectivity over interfering gases such as CO and ethanol. Density functional theory calculations indicate that NO preferentially adsorbs onto Pd sites on the Cs2PdBr6 surface and behaves as an electron donor, leading to a decrease in the resistance of n-type Cs2PdBr6. These results demonstrate that antisolvent-processed Cs2PdBr6 is a promising material for energy-efficient and selective NO sensing.