Plasmoelectronic properties of self-assembled gold nanoparticles: impedance spectroscopy experiments combined with numerical simulations

Plasmoelectronics is a fast developing field driven by the combination of charge transport and surface plasmons in metal nanostructures. In this paper, we report on theoretical and experimental investigations of the plasmoelectronic properties of self-assembled monolayers of colloidal gold nanoparticles (NPs). A local plasmonic-electronic nanojunction is introduced, as the fundamental building block of a mesoscale electrical network, and serves as the beginning point for the development of a multiscale modeling strategy. The interparticle charge tunneling and accumulation account for the dynamical charge transport; the plasmoelectronic properties are implemented at the nanoscale using electrodynamic calculations based on the discrete dipole approximation (DDA) method. The electric characteristics of the macroscopic NP network are calculated using a numerical resolution of the currentbias equations based on Kirchhoff's laws. Disorder effects due to size and position fluctuations of the NPs within the network as well as dislocations and point defects in their spatial arrangement are taken into account. The effects of light excitation intensity and wavelength on the nanojunction photoconductance and on the macroscopic photoresistance of the NP network are addressed. In particular, plasmoelectronic conduction paths are extracted from the coupled DDA-Kirchhoff numerical simulations, and their statistical distribution is investigated as well as their dependence on path length. The theoretical results are compared with impedance spectroscopy measurements performed under optical excitation. We found a good agreement between the predicted impedance Nyquist plots and resonance properties, and the measurements. In particular, we were able to estimate the surface plasmon-assisted photoelectric conversion efficiency involving first neighbor NPs. We found that the photoconductance of a single nanojunction formed by a dimer of nearly touching NPs is around 18 nS/W/cm2 under resonant plasmonic excitation. The presented work provides insight into the photoinduced charge transport in selfassembled NP networks and opens the route to novel applications in the field of plasmoelectronics. (c) 2023 Elsevier Ltd. All rights reserved.