Optimized plasmonic metasurface for efficient ablating of cancer and tumor cells

Photothermal therapy (PTT) offers a promising approach to cancer treatment by elevating tumor tissue temperature, however, it requires efficient light-to-heat conversion at the target site. Qualified nanostructures with optimized absorption for effective PTT remain a key challenge. Then, we propose and numerically investigate plasmonic perfect absorber (PPA) metasurfaces, specifically gold nanodisc arrays (NDAs) and multi-hole arrays (MHAs), designed for enhanced light absorption, which is consistent with cancer cell ablation. Using the Finite-Difference Time-Domain (FDTD) method implemented in Ansys-Lumerical FDTD Solutions, we systematically analyzed the impact of geometric parameters (circular vs. elliptical shapes, varying diameters from 600 nm to 900 nm for NDAs and 400 nm to 800 nm for MHAs, maintaining a 1:2 diameter-to-period ratio) and dielectric spacer materials (SiO₂ and Si) on the reflection and absorption spectra in the near-infrared range. The findings indicate that Au-SiO₂-Au NDA structures with a diameter of 600 nm exhibit significantly reduced reflection (approx. 28 %) and thus high absorption (approx. 72 %) at a resonance wavelength of 3.8 µm. Furthermore, oval NDAs with a small diameter of 600 nm and a SiO₂ spacer layer of 60 nm show superior performance where the absorption cross-section exceeds the scattering cross-section. According to Kirchhoff's law of thermal radiation (A=E), the high absorption efficiency translates to a strong potential for thermal emission, highlighting the suitability of these optimized PPAs as efficient transducers for localized heat generation in photothermal therapy applications.