Janus三角纳米片和"三明治"三角纳米片消光特性的数值研究

基于离散偶极近似法(DDA)计算了不同组分的Janus三角纳米片和“三明治”三角纳米片的消光特性，两种纳米片在紫外-可见光波段均出现了明显的吸收峰。当纳米片较小时，消光特性主要以吸收为主，当纳米片逐渐增大，散射作用开始明显。当纳米片增大时，吸收峰向长波方向移动并且峰会变宽。二氧化硅与银的组合能在较宽的波段内激发表面等离激元效应，因此波峰比金银组合纳米片的波峰宽，但是吸收峰值较后者低。增加纳米片的层数，或者添加纳米片的组分，可以在一定范围内对纳米片的消光特性进行调节，从而提高太阳能光热转换效率。

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.