Blue-light pumped NIR emission of LaOF:Pr3+ nanorods for highly sensitive nanothermometry

Remote thermal sensing is a much-needed technology in today's world; therefore, developing highly sensitive optical thermometer probes has become a necessity. In this study, the luminescence thermometers based on Pr3+ emissions in the red and near-infrared (NIR) regions were used. LaOF:Pr3+ nanorods were synthesized via a microwave-assisted hydrothermal route. The prepared nanorods exhibited excellent photoluminescence (PL) emission in the red and NIR regions under blue laser excitation. Their PL emissions were found to be influenced by temperature, which was exploited to study the thermal sensing ability of the nanorods. Fluorescence intensity ratios (FIRs) of the red and NIR emissions were evaluated for both the thermally coupled levels and the nonthermally coupled levels. The maximum absolute and relative thermal sensitivities were 5% K-1 at 573 K and 0.8% K(-1 )at 303 K, respectively. The temperature resolution of 0.17 K was achieved for the FIR calculated from the NIR emissions. The nanorods passed the repeatability test, and the FIR maintained a similar pattern for repeated heating and cooling cycles. The results suggest that the prepared nanorods are promising materials for nanothermometry applications.