For nanoparticles with a diameter below 1 micrometer and down to about roughly 5 nm, it is not "simple" electronic conduction, it is a combination of electronic conduction (as usual in a metal), but limited to the volume of the nanoparticle, this combined with tunneling (hopping) from particle to particle.

You can find basic papers and explanations on the RG page of Prof. Gunther Nimtz, he and his team had discovered this phenomenon.

I had worked with him on the same topic for my organic nanometal, which shows the same mechanism:

https://www.researchgate.net/publication/13279646_Fully_protonated_polyaniline_Hopping_transport_on_a_mesoscopic_scale?ev=srch_pub&_sg=UuXYUqMor6D81HjrHyTgt4vxHC7%2F8Xt7nZsb1OTi0O5XOCT9mq%2Fh6OM4ICiNgDn3_9McGPOHdPGvzsEHSJDHWSSCb91ynLdcgtSPjpbKPvK69b7cbMoV5Lc1%2FXXeaiaBi

https://www.researchgate.net/publication/41707771_Mesoscale_charge_transport_in_polyaniline?ev=srch_pub&_sg=Hj%2BQ0%2Buq%2BpkH0ell0xTs50Y7RdEtt5CmB1%2B68vSIISnWG%2F7P4fowBFUxBvK6TL8i_%2FWPIFW0ADjEeMPOxO0NwZ4%2BCd8Ngv0HrawTUW78fLpEelVVXoiKYiUkZg8q3MUI0

Article Fully protonated polyaniline: Hopping transport on a mesoscopic scale

Article Mesoscale charge transport in polyaniline

I am not sure below which size a metal nanoparticle is not a metal any more, but some "cluster", should be somewhere around or below 1 nm

Nice and thanks for the information's.