Modeling and analysis of the role of the dielectric environment in plasmon-induced hot carrier transfer in Ag/Graphene/SiO 2 hybrid nanostructure

We theoretically investigate the impact of dielectric environment on plasmon-induced hot carrier transfer from silver nanoparticles (Ag NPs) to a graphene layer on silica substrate (Ag/G/SiO 2 ). Utilizing a comprehensive analytical framework, based on Mie theory combined with Drude-Lorentz permittivity model, we examine the interplay between the size-dependent localized surface plasmon resonance (LSPR) of Ag/G/SiO 2 hybrid nanostructure and the surrounding media. Following the rigorous formalism of Uskov et al (Nanoscale, 6, 4716, 2014) to incorporate effective mass discontinuities and permittivity mismatches at the Ag/G interface, hot electron harvesting accounting for both surface and bulk photoemissions are investigated. The results demonstrate that the dielectric environment plays a decisive role in controlling the characteristic size-dependent LSPR response and hot electron generation and harvesting. Absorption spectra show size-dependent LSPR peaks, with non-monotonic redshift upon increasing radius and higher refractive index of the embedding medium, enabling ∼150 nm tunability. The quantum efficiency was found to decrease monotonically with increasing particle size for both surface- and bulk-photoemission due to the reduced surface—to—volume ratio and multipolar modes. The total hot-electron current exhibits maximum at intermediate particle sizes, which reaches 1.7 pA for Ag NPs embedded in air and decreases with shift toward smaller radii with increasing the medium refractive. These results highlight dielectric environment engineering as an effective route for optimizing hot carrier harvesting, guiding designs for plasmonic devices like sub-bandgap photodetectors and sensors. Optimal configurations favor moderate NP sizes in low—index media for peak currents, while high—index surroundings enhance field confinement for surface mechanisms.