A novel color-tunable emission material Sc2Mo3O12: Eu3+/g-C3N4 for optical thermometry and anti-counterfeiting

To develop novel luminescent materials with optical thermometry and anti-counterfeiting functionalities, this work designed, prepared, and characterized a series of Sc 2 Mo 3 O 12 : Eu 3+ (SMOE) phosphors and SMOE/g-C 3 N 4 composites. Structural and optical analyses reveal that SMOE exhibits two-dimensional negative thermal expansion (NTE) behavior and high resistance to luminescence concentration quenching. Via vapor deposition, g-C 3 N 4 was deposited onto SMOE particles, slightly enhancing their NTE performance. Upon UV excitation, SMOE/g-C 3 N 4 shows dual-emission characteristics featuring blue luminescence from g-C 3 N 4 and red-orange emissions from Eu 3+ , with different dependencies on excitation wavelength. Additionally, the g-C 3 N 4 emission band undergoes spectral narrowing and fast thermal quenching with increasing temperature, in contrast to the relatively stable Eu 3+ emissions. These divergent thermal responses enable five independent thermometric parameters (luminescence intensity ratios, spectral bandwidth, and individual emission intensities) to exhibit linear temperature dependence. A multi-parameter sensing strategy based on a multiple linear regression model yields a maximal relative sensitivity of an exceptional 30%/K, surpassing single-parameter approaches and outperforming most previously reported optical thermometers. Moreover, SMOE/g-C 3 N 4 is proved to be highly suitable for anti-counterfeiting labels, as its luminescence color can be switched by controlling the excitation conditions. Overall, SMOE/g-C 3 N 4 is a highly promising dual-functional material coupled with excellent thermal sensing and anti-counterfeiting capabilities.