Janus-Nanojet as an efficient asymmetric photothermal source

Abstract

The combination of materials with radically diferent physical properties in the same nanostructure gives rise to the so-called Janus efects, allowing phenomena of a contrasting nature to occur in the same architecture. Interesting advantages can be taken from a thermal Janus efect for photoinduced hyperthermia cancer therapies. Such therapies have limitations associated to the heating control in terms of temperature stability and energy management. Single-material plasmonic nanoheaters have been widely used for cancer therapies, however, they are highly homogeneous sources that heat the surrounding biological medium isotropically, thus equally afecting cancerous and healthy cells. Here, we propose a prototype of a Janus-Nanojet heating unit based on toroidal shaped plasmonic nanoparticles able to efciently generate and release local heat directionally under typical unpolarized illumination. Based on thermoplasmonic numerical calculations, we demonstrate that these Janus-based nanoheaters possess superior photothermal conversion features (up to ¬T ≈ 35 K) and unique directional heating capacity, being able to channel up over 90% of the total thermal energy onto a target. We discuss the relevance of these innovative nanoheaters in thermoplasmonics, and hyperthermia cancer therapies, which motivate the development of fabrication techniques for nanomaterials.