Novel electroless gold nano-architectures to enhance photon-plasmon coupling

Understanding and enhancing electromagnetic (EM) coupling in noble metal nano-structures is important in opto-electronics, bio-photonics, and spectroscopic sensors. In this study, light-to-heat transduction in novel gold (Au) nanoparticle (NP) architectures is quantitatively determined for the first time by applying a linearized energy balance. In particular, dense solid-state Au NP arrays coated on internal walls of silica capillaries using a 'bottom-up' electroless (EL) plating method dissipate >10-fold more heat from incident photons (96.9 vs. 9.9%) with a >10-fold faster heat transfer response time (8.4 vs. 86.3 s) by preventing aggregation between NPs that typically occurs in colloidal Au NP suspensions when irradiated with light.;These photothermally-stable solid-state Au nano-architectures are created using an inexpensive EL plating process by reduction of Au ions on tin-sensitized and silver-activated silica surfaces at ambient conditions without requiring conductive substrates or expensive, sophisticated top-down metal deposition equipment. Heat-induced changes in morphology from Au island thin films to random arrays of spherical Au NPs result in tunable optical properties such as photoluminescence (PL) and LSPR. Especially, the ability to tune the LSPR properties by varying NP size and inter-particle spacing is a key factor in improving and optimizing plasmonic devices.;Finally, to control NP size and inter-particle spacing, the application of bottom-up EL plating is expanded herein to create regular arrays of Au nanospheres on silica surfaces patterned by (i) electron beam lithography (EBL), and (ii) nanosphere lithography (NSL). Regular arrays of Au nanospheres created by successive thermal treatments of EBL-patterned EL Au island films exhibit dramatically improved NP sphericity, when compared to NP arrays prepared using top-down Au sputtering. Moreover, selective EL plating on the NSL-patterned silane masks produces multiple samples of regular NP arrays with a millimeter-to-centimeter size without using million-dollar lithography equipment. This technique enables cost-effective fabrication of large-area NP arrays.;The present work suggests that these novel EL Au nano-architectures can significantly increase the performance of the future plasmonic devices based on the well-characterized tunablity of structural, optical, and thermal properties. The application of the versatile EL plating can be further expanded to create novel plasmonic designs for optoelectronic, spectroscopic, biomedical, and sensing systems.