Thermally stable Li+ co-doped ZnMoO4:Eu3+ phosphors for white LEDs, nitroaromatic sensing and low temperature non-contact optical thermometry applications

Abstract

The development of multifunctional luminescent materials with high thermal stability and sensitivity is crucial for advanced lighting, chemical sensing, and temperature monitoring applications. However, many existing red-emitting phosphors are limited by poor thermal stability, weak chemical selectivity, and narrow functional temperature windows. In this work, we present a Li⁺ co-doped ZnMoO₄:Eu³⁺ phosphor (Zn_0.88Eu_0.09Li_0.03MoO₄, ZELMO) that overcomes these limitations through Li⁺ incorporation, which enhances crystallinity, facilitates charge compensation, and modifies the local crystal field around Eu³⁺ ions. ZELMO exhibits a two-fold increase in photoluminescence intensity, excellent color purity (93.6%), and thermal stability with 83% intensity retention at 423 K. It also demonstrates selective and ultra-sensitive detection of 4-nitrophenol, with a low detection limit of 12 nM. Moreover, ZELMO enables non-contact optical thermometry in the 15–295 K range, achieving a maximum relative sensitivity of 0.61% K⁻¹. These results position ZELMO as a promising red-emitting phosphor for multifunctional use in solid-state lighting, environmental sensing, and low-temperature optical thermometry.