The optical properties of dumbbell-type nanorods for solar photothermal conversion

Due to localized surface plasmon resonance (LSPR), plasmonic nanoparticles have exciting potential for improving solar photothermal conversion performance and have been extensively studied. However, in addition to enhanced solar absorption, scattering is also enhanced with the occurrence of LSPR, which is detrimental to the direct absorption of solar energy. The nanoparticles that can excite magnetic resonance can alleviate the above problem but have rarely been studied. In this work, we propose a dumbbell-type nanorod that can excite both electrical resonance and magnetic resonance. The analysis of its optical properties reveals that the dumbbell-type nanorod can excite multiple absorption peaks to enhance absorption while reducing scattering. The mechanism is the coupling between electrical resonance and magnetic resonance. Furthermore, the analysis with the slotted position of the dumbbell-type nanorod shows that the slotting should not occur at the two ends of the nanorod. It is also shown that the optical properties of the dumbbell-type nanorod can be effectively tuned by adjusting the geometric parameters of the slot. The dumbbell-type nanorods are promising for solar photothermal conversion and can be a candidate material for direct absorption solar collectors (DASCs).