Nanoparticles such as gold and silver are becoming more and more used to print circuit or enhance electrical properties of another material. But I have not been able to find sources that clarify how current transport takes place between nanosized particles. In particular, what I am trying to learn is the following:
Suppose we have printed a layer of metallic (such as gold) nanoparticles on a substrate, the size of particles may range from 10-50 nm. What is the dominant form of electron transport at such scale? I know that for instance if the particles are suspended in an insulating medium, then electron tunneling becomes the relevant transport mechanism. But what if we just have the metallic nanoparticles? Are applied voltages linearly related to induced currents? (i.e. Ohm's law holds).
If there's no junction, how does current transport take place between metallic nanoparticles? Do two adjacent particles need to have their surfaces in contact for electron transfer to take place? Is contact resistance the relevant mechanism in this case?
For such nanoscopic systems, do we still expect Ohm's law to hold? that is, if we apply a voltage difference at two junctions of the system, is the measured current related linearly (with conductance being the proportionality constant)? Is there a clear breaking point, in terms of particle sizes, below which we know Ohm's (linearity) law not to hold anymore?