Thermoplasmonic Nanorings via Sputter Deposition.

The fabrication of plasmonic nanostructures with precise geometries and scalable production remains a critical challenge for advancing light-matter interaction technologies in applications such as sensing, photonics, and thermal management. Here, we present a versatile, self-assembly-based strategy for metallic nanoring fabrication. We extend Hole-mask Colloidal Lithography (HCL) by employing ring-shaped holes to produce nanorings via direct current (DC) magnetron sputtering. The process relies entirely on industry-standard thin-film techniques, enabling wafer-scale integration. Using this approach, we fabricate copper (Cu) nanorings with tunable near-infrared (NIR) resonances suitable for thermoplasmonic applications. The thermoplasmonic performance of these nanorings is evaluated under direct sunlight, revealing efficient photon-to-heat conversion. Nanorings displayed enhanced heating, outperforming nanodisks of equivalent size, with maximum surface temperatures reaching approximately 37 °C, an increase of over 13 °C above ambient, in contrast to the 6 °C increase shown by disks that reached a temperature of 30 °C. This superior performance is attributed to the nanoring geometry, which promotes stronger light absorption and localized heating. Overall, our results demonstrate that Cu nanorings represent a robust and scalable plasmonic platform with significant potential for solar-driven technologies and thermal management applications.