Temperature controlled O-PTIR measurements and photothermal signal increase at lower temperatures

The photothermal expansion in photothermal infrared microspectroscopy has traditionally been studied at room temperature. To enable measurements in a different temperature range, a temperature-controlled stage was fitted into the O-PTIR microscope to evaluate the O-PTIR signal of tristearin and polymers during temperature reduction from room temperature down to -100 °C. Therefore, we report the first successful temperature-controlled spectroscopic measurements and imaging of samples using O-PTIR in co-propagating mode. Moreover, for the first time we observed an up to 3- times increase in O-PTIR signal with decreasing temperature, with a maximum at -20 Co.