In Situ Monitoring Charge Transfer on Topotactic Epitaxial Heterointerface for Tetracycline Degradation at the Single-Particle Level

Selectively constructing heterojunctions on specific crystal facets enable directional electron–hole migration and favorable charge separation. Meanwhile, in-depth monitoring and investigating charge-transfer process on specific crystal facets of individual single crystal are particularly important. Herein, we report a strategy for synthesizing SrTiO3/TiO2 epitaxial heterojunctions (ST/T), in which highly ordered SrTiO3 mesocrystals are selectively topologically grown on the TiO2 {001} facet. It exhibits good photocatalytic activity for tetracycline (TC) degradation. Notably, single-particle spectroscopy was employed to accurately monitor the transfer and recombination of carriers at the specific nanoregions of individual particle. The weaker photoluminescence (PL) intensity and longer lifetime at the epitaxial central site of ST/T particle indicate that the epitaxial heterointerface promotes the separation of charge carriers. Moreover, in situ monitoring of TC degradation on single ST/T particle confirms that the epitaxial heterojunction suppressed the PL lifetime decay, further demonstrating the pivotal role of site-selective topotactic epitaxy. This study presents a strategy for rational designing heterojunction photocatalysts and is beneficial for in-depth monitoring and understanding the structure–activity relationship at the single-particle level.