Design Principles for Tailoring Heat Transport via Iris-Gated Core-Double-Shell Nanoparticles in the Context of Photothermal Therapies

Abstract

The rational design of Janus nanostructures that combine efficient optical absorption with controlled thermal transport is essential for advancing plasmonic photothermal therapies and related applications. Here, we introduce a theoretical and computational framework to investigate core-double-shell nanoparticles and their asymmetric version, the iris-gated core-double-shell architecture. The optical response of the structures is first evaluated using generalized Mie theory and subsequently validated through FEM and FDTD simulations, ensuring a consistent description of their electromagnetic and thermal behavior. To systematically map the space of variables, we defined a multi-objective figure of merit that integrates absorption efficiency, absorption cross section, and polymer-layer thickness. Furthermore, we define a thermal gain parameter that quantifies energy densification and complements the analysis of thermal directionality. Our results reveal a near-optimal configuration with parameters ($r_c$, $δ_{Au}$, $δ_p$, $θ$)=(36 nm, 5 nm, 40 nm, 70$°$), capable of producing a temperature rise of 20-23 $°$C, with 67% of the thermal fluz directed toward the upper hemispace and yielding 50% focusing enhancement relative to the symmetric case. This design preserves geometric simplicity and high symmetry while delivering robust thermal asymmetry, thereby facilitating experimental implementation. Beyond photothermal therapies, the proposed methodology constitutes a versatile platform for the rapid screening and optimization of layered nanostructures, adaptable to diverse materials, excitation wavelengths, and functional objectives in nanophotonics.