Development of a Temperature Sensor Using Spin-Crossover Fe(pyrazine)[Pt(CN)4I] Nanoparticles

Device miniaturization requires temperature sensors with high resolution and precise calibration for measurements at reduced scale. We developed an optical temperature sensor using Fe
²⁺
spin-crossover (SCO) material that has low and high spin states depending on temperature. We adjusted the operating range of the SCO (295–365 K) with an appropriate concentration of iodine. The color induced by temperature change was observed with a microscope and was converted to the color intensity represented in grayscale. To test the material, we covered the surface of a gold microheater with a layer of Fe(pyrazine)[Pt(CN)
₄
I] SCO nanoparticles and compared optically measured temperatures with those from a conventional temperature sensor. We conclude that the thermochromic temperature sensor is suitable for measuring temperature changes in microdevices, even in ambient light.