Temperature sensing of a plasmonic nanocylinder array by a polymer film containing chameleon complex

Chameleon complex, a coordination polymer containing Eu3+ and Tb3+ as emitting centers, is a temperature sensor whose photoluminescence (PL) intensity ratio between Eu3+ and Tb3+ varies with the temperature. Although the performance of this complex has been verified in a form of powders, it has not been used as a film, which is a commonly used form for various applications. In this study, we fabricate a temperature-sensing thin film by dissolving a chameleon complex powder in poly(methyl methacrylate) (PMMA). The chameleon complex retains the responsivity to temperature after the dispersion in PMMA. The PL intensity ratio changes almost linearly with the temperature in the experimental range of 20°C–40°C. In order to further demonstrate the temperature sensing ability of the film, we deposit the film on a plasmonic periodic array of Al nanocylinders. We simultaneously use two laser lines to excite both localized surface plasmon resonances (LSPRs) hybridized with in-plane diffraction in the array and the chameleon complex in the film. The LSPRs decay into heat increasing the temperature, which is then detected through the PL intensity ratio between Eu3+ and Tb3+. The temperature increase is in agreement with numerical calculations. The results show that the film is applicable for temperature sensing in a local area defined by the excitation spot.