Functionalized nanoparticle films with rectifying conduction properties

Gold and silver nanoparticles functionalized at their surfaces with electron acceptor (TCNQ) and donor (TMPD) molecules were spray-deposited as thin films on highly ordered pyrolytic graphite (HOPG) substrates. Pure films and bilayer structures were investigated by means of scanning tunneling spectroscopy (STS). The pure films show symmetric current-voltage dependences, whereas the bilayer structures are characterized by a diode-like behavior with rectification ratios of up to 66 at +/-75 mV for structures containing silver nanoparticles and 6.5 at +/-1 V for analogous structures based on gold nanoparticles. Such properties have been previously described for molecular rectifiers containing electron acceptor and donor groups. Our results suggest that electronic structures of this type might be assembled alternatively through appropriate nanoscale architectures using sequential deposition of functionalized nanoparticles.