Development of Apparatus for Simultaneous Measurements of Raman Spectroscopy and High-Sensitivity Calorimetry

TLDR: In this paper, the use of thermoelectric modules as heat flux sensor and as a heat pump in a hand-made calorimeter enables the authors to measure thermal phenomena with high sensitivity and high thermal stability at very slow heating and cooling rates.

Abstract: We constructed an apparatus that enables us to simultaneously detect structural changes of molecules and the accompanying thermal phenomena by combining a commercially available Raman spectrometer and a hand-made calorimeter. The use of thermoelectric modules as a heat flux sensor and as a heat pump in our calorimeter enables us to measure thermal phenomena with high sensitivity and high thermal stability at very slow heating and cooling rates. Efficiency is important to treat a small amount of sample and also to make the experimental conditions nearly quasi-static by balancing the heating effect of laser beam irradiation. As a performance test, we measured a prototype ionic liquid (IL), 1-buthyl-3-methylimidazolium bromide ([bmim]Br), which has some characteristic thermal properties. It was confirmed that the melting links to the cooperative conformational change of the butyl group in the [bmim]+ ion.