The Optimization of the Luminescence Intensity Ratio in the YVO ₄ :Er ³⁺ ,Nd ³⁺ Phosphors within the First and Second Biological Windows

The optimization of the host materials is one of the methods that could be used to improve the relative sensitivity of luminescent thermometers. Here, we show the host optimization emission of Er³⁺ and Nd³⁺ ions in the YVO₄ phosphors produced by a modified sol-gel route using glucose as a polymerizing agent. X-ray diffraction (XRD) was realized to analyze the formation of the crystalline phase. We found that the emission ratio depends on the size of the YVO₄ particle. Here, we show that YVO₄:Er³⁺,Nd³⁺ phosphors exhibit particle size-dependent relative sensitivity values, varying from 1.32 ± 0.02 to 1.80 ± 0.02% K^-1 at 293 K, and temperature uncertainties below 0.7 K within the physiological range 293-233 K, operating entirely in the first and second biological windows. These sensitivity and temperature uncertainty values were achieved by defining two thermometric parameters as the luminescence intensity ratios, exploiting a combination of emissions from both ion species.