Near-infrared light heating of a slab by embedded nanoparticles

Exposed to spectral and uniform light, the heating of a one-dimensional, conducting and radiatively participating medium due to embedded absorbing and scattering nanoparticles is solved. Spherical harmonics approximation is used to solve the radiative transfer equation and the finite difference explicit method is used to find the temperature distribution in a generic slab having both boundaries subjected to convection. The host medium is transparent to spectral radiation and the temperature distribution is obtained when the temperature of the irradiated boundary reaches a desired point specified to ensure that any temperature in the medium does not exceed its melting temperature. It is found that the variation of the concentration and configuration of the embedded nanoparticles, particularly gold nanoshells, changes the radiative transfer spectrum, which leads to an alteration in the local heat generation spectrum and the resulting temperature distribution in the medium. It is shown that a gold nanoshell configuration with a great amount of scattering increases the internal diffuse radiation, which creates a more even radiative distribution, while a configuration with a great amount of absorption promotes a high amount of absorption in the entry region and very little in the rear region, leading to the formation of a large temperature gradient between the two boundaries. The present study provides a framework from which the photothermal heating of nanoparticle mixtures in non-transparent host media may be applied.