Improved relative temperature sensitivity of over 10% K -1 in fluoride nanocrystals via engineering the interfacial layer.

Real-time in situ temperature sensing is of significance in the bio-medical field; however, the low relative temperature sensitivity S r is one of the major obstacles in the development of nanothermometers. Herein, we provide an effective route that engineers the interfacial layer in a core/shell/shell nanostructure to enlarge the temperature-dependent luminescence intensity ratio (LIR) variations followed by an improved S r . The CaF 2 interlayer is employed to inhibit the interaction between the core and outer shell, and increase the interfacial phonon energy to enhance the negative thermal quenching effect (TQE) of Nd 3+ ions in the outer shell and positive TQE of Er 3+ ions in the core layer. Based on the temperature-dependent LIR variations of Er (650 nm) to Nd (800 nm), the maximum S r of 10.01% K -1 and minimum S r of % 2.56% K -1 are achieved.