Infrared thermography studies on the photothermal effect of gold nanoparticles in water

Abstract

Infrared (IR) thermography has been utilized in the last decades for the detection of many diseases. With the growth of nanotechnology as also grown the investigation of the interactions between electromagnetic radiation and metallic nanoparticles and its heat transfer property. Such property is often used in medicine as a hyperthermia treatment for cancer. Due the importance of the heated nanoparticle applications it is a need to have a system that can monitor, recollect, process, and analyze data information coming from heated bodies. Being so, the general objective of this work is the development of an IR thermography based method to study thermal effects on surfaces. This works presents a new improved method of monitoring surface temperature changes by dynamic IR thermography. The method is based on the careful analysis of IR image sequences that allows one to select areas with significant temperature variation and evaluate temporal behavior of the surface temperature. A set of codes was written in MATLAB software to analyze the superficial changes in temperature for systems that present a volumetric or superficial heating process. To test the method, the experimental study on the photothermal effect in a gold hydrosol containing 0.3 mg/mL hollow GNPs was performed. A simple set up was designed to heat the hydrosol by laser light and monitor the hydrosol surface temperature by IR camera. It was shown that the surface temperature under the laser beam gradually increases and reaches a saturation level. The surface temperature distribution exhibit the concentric structure with the maximal temperature in the beam center. After the laser was turned off, the temperature returned to equilibrium with the area outside of the beam in about ten seconds. Numerical simulations of the experiment with the COMSOL Multiphysics Heat Transfer module were used to reproduce the measured surface temperatures and estimate the heat transfer coefficient at the hydrosol surface and photothermal conversion efficiency, the parameters that would be difficult to find byother methods. In conclusion, this work presents a new improved method for the data acquisition and data analysis based on dynamic IR thermography. This method is not limited to colloids with nanoparticles, but it can be applied for any system whose superficial temperature is change under an external stimulation. Despite the IR thermography measures only a surface temperature, it is possible, combining the precise surface temperature detection and results of numerical simulations with an adequate model, to estimate the volumetric temperature and determine 3D heat delivery during the hyperthermia procedure.