Abstract: The present invention is a chemiresistor for qualitative and quantitative analysis of chemical species that consists of a very thin film of particles, nanoclusters, deposited on an insulating substrate and contacted by electrodes. The particles have a metallic core, preferably spheroidal, that is less than 5 nm in diameter and surrounded by an monolayer ligand shell ranging in thickness from 0.4 nm to 2 nm. The Coulomb blockade effects upon which the invention operates result in nonlinear current-voltage characteristics which dramatically improves sensitivity with much lower power dissipation. One property of the ligand shell is that its chemical composition can be chosen to be especially receptive to a particular chemical vapor.