Photothermal conversion characteristics of gold nanoparticle dispersions

• Propose and validate for the first time to use plasmonic nanoparticles to improve solar thermal efficiency.
• Gold nanoparticles (GNPs) improve remarkably the photothermal conversion efficiency.
• The efficiency enhancement reaches 65% comparing to the base fluid at 6 ppm GNP.
• The specific absorption rate (SAR) of GNPs reach 10 kW/gram at 0.15 ppm GNP.
• The comparison with other materials shows that GNP has the highest SAR.

This work proposes and validates a novel idea of using plasmonic nanoparticles (PNP) to improve the solar thermal conversion efficiency. Gold nanoparticle (GNP) is synthesized from an improved citrate-reduction method, and used as an example to illustrate the photothermal conversion characteristics of PNPs under a solar simulator. The experimental results show that GNP has the best photo-thermal conversion capability comparing to other reported materials. At the lowest particle concentration examined (i.e., 0.15 ppm), GNP increases the photo-thermal conversion efficiency of the base fluid by 20% and reaches a specific absorption rate (SAR) of ∼10 kW/g. The photo-thermal conversion efficiency increases with increasing particle concentrations, but the SAR shows a reverse trend, which is unexpected as all GNPs should be still in the independent scattering regime.