Experimental and Theoretical Validation of Plasmonic Nanoparticle Heat Generation by Using Lock-In Thermography

The use of plasmonic nanoparticles for biological applications has been gaining momentum in the last two decades. The ability of these particles to generate heat when exposed to light with a given wavelength is one of their prominent features. Quantifying the heat emission and relating it to the shape, size, and concentration of particles is of great importance. In this work, we show how lock-in thermography, a technique where temperature changes are obtained by means of an infrared camera, can be used to measure efficiently and non-invasively the heat generated by plasmonic nanoparticle solutions exposed to a modulated light source. We developed a mathematical model based on energy balance, where the heat generated by particles is computed from the absorption cross section of particles using Mie theory. The model, free of adjustable parameters, can quantitatively predict the heat generated by gold nanoparticles in suspensions in a broad range of concentrations and for two different wavelengths, which were experimentally investigated. The model and experimental data show how the amplitude of the temperature response increases linearly with the gold concentration, and is almost independent of the investigated particle size.

Automated summary

The use of plasmonic nanoparticles in biological applications has increased over the past two decades due to their ability to generate heat when exposed to light. Lock-in thermography can efficiently measure the heat produced by these nanoparticles, and a mathematical model based on energy balance using Mie theory can quantitatively predict the heat generation by gold nanoparticles in different concentrations and wavelengths. The model shows a linear increase in temperature response with gold concentration and independence from particle size.