Upconverting PAAm/PNIPAM/NaYF4:Yb:Er hydrogel with enhanced luminescence temperature sensitivity

We present a one-step approach to combine the functional features of upconverting NaYF4:Yb:Er nanoparticles and thermosensitive poly(N-isopropylacrylamide) (PNIPAM) for luminescence thermometry. Dual-functional hydrogel that simultaneously possesses strong upconversion luminescence (UL) and temperature responsibility was fabricated based on the crosslinking of poly(acrylamide) in the presence of PNIPAM and NaYF4:Yb:Er nanoparticles. The obtained hydrogel exhibited reversibly temperature-dependent UL and highly enhanced sensibility. The luminescence temperature sensitivity reached 1.9% per °C and 0.7% per °C in the range of 27-33 °C and 35-45 °C, respectively. The maximum sensitivity could even reach 26.5% per °C in the range of 33-35 °C. Considering the facile fabrication process and fine luminescence thermometry performance, this study thus opens up new opportunities for preparing highly sensitive temperature sensors.