Single-Band Upconverted Near-Infrared Emissions Achieved through Energy Migration Control for Multimodal...

Modification of photoluminescence spectra through doping is a crucial strategy for enhancing optical performance, thereby expanding the applicability of luminescent materials across diverse fields. In particular, single-band upconverted near-infrared (NIR) emissions, though challenging to be achieved, are highly desirable for applications in data encryption, anticounterfeiting, and bioimaging. Herein, we present an effective approach to manipulate the energy distribution across the different excitation states of Tm³⁺ by constructing Mn²⁺-mediated energy transfer (ET) bridges. The incorporation of Mn²⁺ significantly enhances the upconversion (UC) NIR emissions of Tm³⁺, while simultaneously suppressing the competing visible transitions. This engineered redistribution directs the excited-state energy from the higher to lower energy levels in Tm³⁺, culminating in exclusive single-band NIR output. The underlying UC ET mechanisms have been systematically investigated through steady-state and transient luminescence analyses, revealing two distinct ET bridges that regulate the electron population probabilities across the excitation states of Tm³⁺. Furthermore, the detailed ET pathways have been elucidated and identified using quantum-cutting-based cross-relaxation models. As a result, the optimized UC excitation-emission system, driven solely by NIR light, demonstrates promising potential for information encryption and multimode anticounterfeiting. This study demonstrates a practical strategy for finely tuning luminescence spectra, thereby facilitating the development of multifunctional luminescent materials.