Synthesis and solar photo-thermal conversion of Au, Ag, and Au-Ag blended plasmonic nanoparticles

An experimental investigation was performed on the solar photo-thermal conversion performance of Au, Ag and Au-Ag blended Nanoparticles (NPs). The experimental results showed that both the temperature and photo-thermal conversion efficiency increased as the Au NP volume fraction increased. However, nanofluids with lower NP volume fractions showed a higher Specific Absorption Rate (SAR) since the photon-absorption of each NP was limited. Plasmonic Au and Ag nanofluids showed a better photo-thermal conversion performance than semiconductor ZnO and TiO2 nanofluids. The photo-thermal conversion efficiency of Au-Ag blended NPs (1.75-0.15 ppm) was 30.97%. This is almost equal to the arithmetic sum (30.91%) of the photo-thermal conversion efficiencies of Au NPs (1.75 ppm) and Ag NPs (0.15 ppm) separately because of the separate absorption of different wavebands by the Au and Ag NPs. Our work provides a promising method for preparing working fluids for solar photo-thermal conversion by mixing different NPs to match the solar spectral intensity instead of increasing the volume fraction of the same NP.