Dielectric properties of gold nanoparticles cross-linked with dithiol spacers

Abstract

Solid materials based on gold nanoparticles cross-linked with a dithiol spacer molecule were prepared and their dielectric properties examined. The gold nanoparticles were synthesised via a standard toluene/water two phase system using sodium borohydride as the reducing agent. Two different sized nanoparticle colloids were produced, 4.8 and 1.2 nm diameter. These were cross-linked with two dithiol compounds, 1,5-pentanedithiol and 1,9-nonanedithiol. The combination of two different size colloids and two different spacer molecules led to four final materials. The dielectric properties of the four materials were investigated using a broadband dielectric spectrometer in the frequency range of 1 Hz to 10 MHz and the temperature range 123-373 K. The imaginary component of the dielectric loss factor is presented for each material over the frequency and temperature range quoted. The 1 Hz room temperature conductivity for each material was between 0.1 and 7.2 μS cm^-1. The temperature dependence of the conductivity followed that predicted for a non-metallic activated electron hopping mechanism with the electrostatic activation energy for each material being between 0.034 and 0.120 eV. These were calculated by applying the simple Arrhenius based equation first described by Neugebauer.