Bi3+ and Tb3+ Co-doped Cs2AgInCl6 Lead-free double perovskite nanocrystals for detection of temperature and copper ions

The content of Cu 2+ in lubricating oil and lubricant temperature are important indicators predicting mechanical failure. Therefore, developing a nontoxic fluorescence probe is necessary to detect Cu 2+ and temperature in lubricating oil. The lead-free inorganic double perovskite nanocrystals (NCs) Cs 2 AgInCl 6 are potential candidates. However, the low fluorescence intensity and the high excitation energy required of Cs 2 AgInCl 6 NCs limit their practical applications. In this study, Bi 3+ and Tb 3+ were successfully co-doped into Cs 2 AgInCl 6 NCs via the hot-injection method. The doping of Bi 3+ produces a broad emission originating from self-trapped excitons and reduces the excitation energy, allowing commercial LEDs as excitation sources. Tb 3+ ions doping offers characteristic emission peaks ( 5 D 0 - 7 F J ) of Tb 3+ ions and improves the fluorescence intensity of Cs 2 AgInCl 6 NCs. Furthermore, the Cs 2 AgInCl 6 : Bi 3+ /Tb 3+ NCs have been employed as optical thermometry, which provide a temperature calibration curve with the maximum absolute and relative sensitivities of 2.15% K −1 at 350 K and 2.25% K −1 at 303 K in the temperature range of 303–423 K, respectively. Finally, the nanocrystals have been applied to detect Cu 2+ in lubricating oil. The fluorescent probe shows a good detection sensitivity of 8.94 × 10 -4 nM −1 and a low detection limit of 14.3 nM in the range of 10–300 nM. This work not merely offers a novel way for improving the luminescence performances of double perovskite NCs Cs 2 AgInCl 6 , but broadens their potential for detection of Cu 2+ and temperature.