Excitation-dependent multicolor luminescence with tunable afterglow from Te4+-doped (CytH)2SnCl6 for dynamic anticounterfeiting

Abstract

The development of luminescent materials with excitation-dependent emission is essential for the applications of anti-counterfeiting and information security. However, this unique property has not yet been achieved due to the ubiquitously accepted Kasha's rule. Herein, cytosine (Cyt) is protonated as a countercation to construct a zero-dimensional (CytH)₂SnCl₆ that emits a green afterglow for up to 1.0 s at room temperature. Upon doping with Te⁴⁺, (CytH)₂SnCl₆:x%Te exhibits excitation-dependent emission because of the different optimal excitation wavelengths for the dual emissive centers CytH⁺ (approximately 350 nm) and Te⁴⁺ (approximately 330 and 390 nm). Moreover, the overlapping between the emission of CytH⁺ and absorption of Te⁴⁺ induces efficient resonant triplet energy transfer from CytH⁺ to Te⁴⁺, resulting in a tunable persistence time for the green afterglow produced by CytH⁺. Using excitation-dependent emission and tunable afterglow persistence time, the potential of (CytH)₂SnCl₆:x%Te was demonstrated in the application of anti-counterfeiting and information encryption. This study provides an effective strategy for endowing metal halide hybrids with multicolor luminescence.