Plasmonic photocapacitance of self-assembled gold colloidal nanoparticle monolayers

We report on the plasmo-electronic properties of self-assembled monolayers of gold colloidal nanoparticles (NPs) formed on a polyimide flexible substrate. The dependence of both resistance and capacitance of these NP assemblies on temperature, bias voltage, optical excitation, and strain is investigated both experimentally and theoretically. Resistance and capacitance appear to bring complementary information on the charge transport properties of the NP assemblies as they exhibit opposite behaviors. Based on a nanocircuit junction model combined with numerical simulations, we were able to account for both the resistance and capacitance and their photo-induced modifications. The dependence of the capacitance on laser irradiation intensity and wavelength was measured, and the role of the surface plasmon resonance was pointed out. We show that the plasmonic-induced photocapacitance can reach 43% for a moderate irradiation intensity of 3.5W/cm(2). Moreover, the NP assemblies, deposited on flexible substrate, were submitted to a uniaxial strain which allows for controlling the interparticle distances and hence for probing the plasmo-electro-mechanical properties of the assembly. We found that, under plasmonic pumping of charges, the photo-capacitance gauge factor is three times larger than the one measured under dark conditions, in agreement with the calculations. The presented work thus paves the way to the emergence of a new class of plasmonic-enhanced capacitance strain sensors. (C) 2018 Elsevier Ltd. All rights reserved.