Design and optimization of plasmonic metal nanoantennas on a glass substrate for efficient solar-driven evaporation of seawater: an optical and numerical simulation approach

In this study, we present optical and numerical analysis methods to enhance the absorbed power of metallic nanoantenna arrays on a glass substrate under solar irradiance. A comprehensive exploration of various materials (Au, Pt, core-shell Ag-Pt, and Al-Al2O3), morphologies (rectangular prism, cylindrical, triangular prism, and hexagram prism with the same volume of metal), and arrangements (periodic, disorder, and amorphous) was conducted to optimize absorbed power and heat production for maximizing the photothermal effect. In periodic arrangements, the absorbed power increased 1.5 to 3 times (minimum to maximum) by optimizing the period across different nanoantenna configurations. Morphologies characterized by sharp angles (triangular, hexagram) exhibited 1.3 to 1.7 times higher absorbed power. Despite Pt’s shorter absorption decay length, it demonstrated broader absorption across the solar spectrum, resulting in 1.15 to 1.3 times more absorbed power than Au. Incorporating an Ag core with a Pt shell enhanced the absorbed power by 1.2 to 1.35 times compared to Au. The hexagram Ag-Pt nanoantenna displayed the highest absorbed power in periodic and disordered arrangements, while the triangular Pt excelled in amorphous configurations. The triangular Al-Al2O3 nanoantenna exhibited 1.14 times higher absorbed power compared to the rectangular Au, presenting a cost-effective manufacturing option. The behavior of plasmon fields and destructive interference was investigated for the nanoantenna array. Three absorption regions were observed: near-distance with minimum absorption due to plasma turbulence, middle-distance (resonance period) with maximum absorption due to plasmon fields enhanced each other, and far-distance with constant absorption due to interference happening between the nanoantenna and incident light without other effects.