Orange/cyan emissive sensors of Sb3+ for probing water via reversible phase transformation in rare-earth-based perovskite crystals

Abstract

A facile strategy for water probing with visible perception is particularly important for water transport, ecosystem sustainability, and the ocean industry. Here, we have developed a simple technology to probe water content by using the response of the orange/cyan luminescence color of Sb³⁺ emitted from the two novel rare-earth-based perovskite crystals Rb₂ScCl₅·H₂O and Rb₃ScCl₆. The reversible transformation between Rb₂ScCl₅·H₂O and Rb₃ScCl₆ accompanied by the significant visible perception of the change of the luminescence color can be realized through the dehydration/hydration process in air. In addition to the favorable sensitivity to water, an in-depth study shows that the highly efficient photoluminescence (PL) of Sb³⁺ in both Rb₂ScCl₅·H₂O and Rb₃ScCl₆ host matrixes arises from the self-trapped excitons (STEs) rather than the 5s²–5s¹5p¹ transition of Sb³⁺ according to the density functional theory (DFT) calculation. It can be anticipated that this study will provide new insights into the luminescence mechanism of Sb³⁺ in perovskite crystals and a potential application in a sensitive sensor for probing water content.