Joule Heating and Laser Flash Tip-enhanced Raman Spectroscopy Method for Characterizing Specific Heat of a Single Nanoparticle
Nanoparticles are widely used in composite materials and nanoscale devices. Characterization of the thermophysical properties of a single nanoparticle is of great importance for both nanotechnology and nanoscience. Limited by the spatial resolution of conventional measurement methods, previous studies were focused on the overall thermophysical properties of the aggregated nanoparticles. The thermophysical properties of a single nanoparticle have been predicted by theoretical calculations. This paper presents a new method for measuring the specific heat of a single nanoparticle, which combines Joule heating method and laser flash tip-enhanced Raman spectroscopy method. Using a conductive probe to heat a single nanoparticle, comparing the heat power of the probe when it contacts or doesn't contact the nanoparticle, the effective coefficient of heat transfer can be characterized. A series of cycled square laser pulses are applied to heat the same sample, and the corresponding temperatures are measured by their Raman band shifts, which matches a lumped parameter model. The high spatial resolution of tip-enhanced Raman spectroscopy method ensures the measurement feasibility. The laser absorption coefficients of the nanoparticle can be eliminated by comparing the temperature rises measured with different laser pulse widths. The specific heat of the nanoparticle can be extracted by fitting the normalized temperature rise curves. Case studies showed that this method is sensitive for measuring the specific heat of single nanoparticle with about 100 nm diameters using ~1 ns pulse width.