Plasmonic nanofluids based on Janus nanosheets and sandwich-structured nanosheets for solar energy harvest

Direct absorption solar thermal collectors (DASC) explore the photo-thermal conversion characteristics of fluids to convert solar radiation into thermal energy. Plasmonic nanofluids have been used to improve the efficiency of DASC as working fluids, because of the localized surface plasmon resonance (LSPR) effect excited on the surface of metallic nanoparticles. Recently, Janus materials have witnessed fast development due to their diversified promising performances and practical applications. Compared with their spherical counterparts, Janus nanosheets have gained more concerns for their highly anisotropic shape. Herein, the discrete dipole approximation (DDA) is employed to calculate the extinction characteristics of Janus triangular nanosheets and sandwich-structured triangular nanosheets with different sizes. The results show that the LSPR of Janus nanosheets and sandwich-structured nanosheets can be improved by tuning the size. For Janus nanosheets, the thickness plays an important role on the resonance strength, whereas it has little effect on resonance frequency. On the contrary, the resonance strength and resonance frequency of sandwich-structured nanosheets can be influenced by the thickness evidently. Effective control of extinction characteristics can be achieved by varying the relative thickness of each layer of nanosheets, to adjust the extinction peak to the desired band. Optimizing the thickness of the Janus nanosheets and sandwich-structured nanosheets, or combining different sizes of nanosheets, will broaden the effective absorption band, thereby improve the photo-thermal conversion efficiency and the efficiency of direct absorption solar thermal collectors.