Surfactant-Free, One-Step Synthesis of Lead-Free Perovskite Hollow Nanospheres for Trace CO Detection.

Owing to their special photoelectric properties, halide perovskites have always attracted research attention. Hollow-structured halide perovskites have many practical applications but are challenging to prepare as most template methods violate their poor chemical and thermal stability. In this study, novel halide perovskite Cs2 PdBr6 hollow nanospheres are prepared using a template-free method; specifically, large quantities of highly pure lead-free halide perovskite Cs2 PdBr6 hollow nanospheres are produced at 30 °C without a surfactant. These ultrapure nanospheres exhibit superiority in chemresistive detection of CO with a detection limit of 50 ppb, which is the lowest among all the reported CO sensing materials. Moreover, in situ sum-frequency-generation spectra and density functional theory calculations reveal that the high sensitivity is attributable to the large specific surface area and surfactant-free surface of rich Br- vacancies that favor CO binding. Overall, this work provides insight on regulation of the halide perovskite structure and the use of hollow spheres in gas-sensing applications.