Energy transfer in Bi3+-Sm3+ co-doped phosphors for temperature sensing and imaging

Fluorescence thermometry has the distinct superiority of non-invasive, non-contact, and high spatial resolution. However, the simultaneous improvement of temperature sensitivity and resolution remains challenging. Herein, the La3Ta0.8Sb0.2O7 matrix was co-doped by Bi3+ and Sm3+ with energy transfer for tunable emission color, which was further applied for fluorescence temperature sensing and imaging. With the partial substitution of Sb5+ with Ta5+, the emission peak of La3SbO7:0.04Bi3+ shifted from 530 nm to 460 nm, together with a 2.1-fold enhancement of emission intensity. The emission could be shifted from bright blue to purple under 365 nm excitation based on the energy transfer. The energy transfer efficiency from Bi3+ to Sm3+ can reach 41.6% via dipole–dipole interaction. The La3Ta0.8Sb0.2O7:(0.04Bi3+,0.005Sm3+) phosphors exhibit maximum relative sensitivity (Sr) of 1.32%K-1 (@498 K) and absolute sensitivity (Sa) of 0.059K-1 (@417 K), which have excellent temperature resolution and repeatability. Thus, the energy transfer in co-coped phosphors can simultaneously improve the temperature sensitivity and resolution for fluorescence temperature sensing. Besides, the phosphor/PDMS films can exhibit obvious thermochromic imaging.