Conductance Fluctuations in Chains of Particles Arising from Conformational Changes of Stabilizer Molecules

We have bridged a pair of gold electrodes with various arrangements of gold nanoparticles stabilized with citrate molecules. The resulting devices exhibited current fluctuations at a constant bias voltage and fluctuations of the differential conductance as a function of the bias voltage. These fluctuations were attributed to the interplay of molecular conformation, charge switching, and breaking of the links at the interface molecules–electrode. We found that, for all investigated samples, the contact resistance at the interface molecules–electrode was by about one order of magnitude larger than that between nanoparticles coupled by citrate molecules. We conclude that the mechanism of charge transport can be viewed as a series of discrete steps involving initial hopping (injection) of the charge from the left-hand-side gold electrode to the molecules, tunnelling of the charge through the molecules–nanoparticle–molecules (MNM) unit, hopping to the next MNM unit, etc., and finally hopping (extraction) of the charge to the right-hand-side gold electrode.