(263d) Nanoparticle Films Exhibiting Electronic Memory

Thin films of Au nanoparticles (NPs), stabilized with self-assembled monolayers of N,N,N-trimethyl(11-mercaptoundecyl)ammonium chloride (TMA), exhibit electronic ?memory? of previously applied potentials. Here, we deposit the films by drop coating aqueous NP solutions onto glass slides, then evaporate two Au electrodes on top of the film. A ±4 V potential is applied between the electrodes two ?write? data into the film, then application of a lower, +0.5 V, potential allows the written data to be read by measuring the conductivity of the film. Specifically, if a ?4 V potential is used to write into the film, then, when the +0.5 V potential is applied, the conductivity of the film is greater than and decreasing to its equilibrium value. Likewise, if a +4 V potential is written into the film, then the conductivity of the film after application of a +0.5 V potential is initially lower than and increasing to its equilibrium value. Thus, the film's previous state may be determined by observing the change in the conductivity of the film after application of the +0.5 V potential.

The presence of this ?memory? effect may be attributed to motion of the Cl- counterions within the film. When a ±4 V potential is used to write into the film, the Cl¬- anions concentrate at the more positive electrode. Then, when the +0.5 V potential is applied, the redistribution of Cl- anions produces a transitory current that is responsible for the observed change in film conductivity.