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 Cs 2 PdBr 6 hollow nanospheres are prepared using a template-free method; specifically, large quantities of highly pure lead-free halide perovskite Cs 2 PdBr 6 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.