Boosted sensitive optical thermometers utilizing synergistic effects of thermal enhancement and quenching in Er/Yb/Nd triply-doped Bi4Ti3O12 nanosheets

Rare earth-doped nanomaterials can achieve diverse upconversion luminescence by changing doping ions, presenting them as promising candidates for rapid temperature measurement. However, most upconversion luminescent phosphors have a thermal quenching effect, which greatly weakens the luminous intensity of the material and impairs thermometry performances. Here, we studied the synthesis of Bi4Ti3O12 nanosheets tridoped with Er3+, Yb3+, and Nd3+ ions using molten salt method. Notably, this luminescent material demonstrates both thermal quenching and thermal enhancement effects. The unusual phenomenon results in a high sensitivity of the optical temperature sensor based on the inter-ion energy level between Er3+ and Nd3+. At 523 K, this sensitivity reaches 5.94x10- 2 K-1, surpassing that of sensors relying on the thermal coupling of only Er3+ ions by nearly ninefold. Our findings suggest a promising strategy to augment the temperature sensing sensitivity of luminescent materials, paving the way for potential applications in precise temperature monitoring.