Green Synthesis of Deep Ultraviolet Response Nanophosphors with Tunable Full-visible-spectra Emission for Luminescent Temperature Sensing

Abstract

Background: Recently, the CaMoO4 nanocrystal has been viewed as one of the most promising substrates for rare-earth-doped nanophosphors due to its high density, stable chemical properties, and good deep-ultraviolet (DUV) responding characteristics. Aim: In this work, a green synthesis approach is proposed to obtain rare-earth-doped CaMoO4 nanodispersion with full-visible-spectra emission by using an ethanol-water mixed solvent in a rotating packed bed (RPB) reactor. Method: The obtained nanophosphors exhibited bright luminescent emission with tunable color in the range of full-visible-spectra via doping of Eu3+, Tb3+, and Dy3+, when they were excited by deepultraviolet (DUV) light. The RPB promoted the uniform distribution of rare-earth ions and the crystallinity of CaMoO4 particles, and the use of ethanol-water as solvents with no toxicity and less environmental pollution was beneficial for large-scale production. Result: The quantum yields for nanophosphors of CaMoO4: Na+, Eu3+, CaMoO4: Na+, Tb3+, and Ca- MoO4: Na+, Dy3+ were measured to be 46.96 %, 28.05 %, and 10.27 %, respectively, which were among the highest values ever reported for rare-earth-doped CaMoO4-based nanophosphors with similar morphology. The temperature-dependent luminescence of CaMoO4: Eu3+, Na+ nanophosphors was investigated in the range of 298 K - 498 K. Conclusion: The clear correlation between luminescence intensity and temperature indicates the potential novel application areas for CaMoO4: Na+, Eu3+ nanophosphor as a non-invasive thermometer. Upon regulating different nanophosphor material ratios, the obtained product shows a flexible fluorescence towards full-visible-spectra emission.