Thermometry based on phonon confinement effect in nanoparticles

Raman spectra of TiO2 nanoparticles (NPs) have a very strong finite-size dependency due to the phonon confinement effect. This provides a convenient way to characterize NPs size by simply using Raman spectroscopy. Together with fast grain growth kinetics and high stability under high temperature and pressure, these NPs have the potential to forensically retain the complete thermal history (temperature and time) of an event that they went through. Here, we demonstrate that both temperature and time can be determined simultaneously by using these thermosensors in the range of 400-700 degrees C and 5-60 s, assuming that the temperature is constant (a step-function approximation to a thermal spike) during a thermal event. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3565250]