Thermoplasmonics Effect of Au and Ag Multi-nanoparticles: Influence of Polarized Light Direction, Particle Spacing, and Substrates

The growing interest in the thermoplasmonics effect has begun to penetrate into multi-nanoparticle systems and their mechanisms. In this study, Au and Ag nanoparticle arrays and Au/Ag–substrate composite structures were constructed, and the effects of particle spacing, polarized light direction, and substrate on their thermoplasmonics properties were studied by the finite element method combined with optical and heat-transfer theory. Taking the particle size of Au and Ag as 20 nm in multi-particle systems, it is found that the variation of particle spacing and polarization direction can cause significant changes on light-absorbing and heat production properties based on the plasmon coupling and collective thermal mechanism, and the light absorption and heat production properties of Ag are better than Au. Following study is focused on Au/Ag multi-particles embedded in the substrates of ITO and TiO2 with different refractive indices, the changes in the absorption spectrum, light absorption intensity, heat production capacity of multi-particles caused by substrate materials, and the embedding depth under longitudinal and transverse polarization are discussed. Moreover, it is revealed that Fano resonance is generated when the number of Au particles is increased to 16 and above in the system with or without substrates, resulting in Fano linear in the absorption curve. This study will provide some important insights into the exploration and application of the thermoplasmonics effect of multi-particles.