Electrical bistability is demonstrated in a polymer memory device using polystyrene containing an organic conjugated compound (8-hydroxyquinoline) and gold nanoparticles (An NPs) capped with different alkanethiols of carbon chain lengths as the active layer between two metal electrodes. An NPs capped with three different alkanethiols [1-octanethiol (C8), 1-dodecanethiol (C12), and 1-octadecanethiol (C18)] are investigated for the correlation with the memory performance. Above a threshold voltage, the as-fabricated device can transit from low conductivity state to high conductivity state. By applying a certain positive voltage, the high conductivity state can return to the low conductivity state. The switch-on voltages of thiol-derivatized Au NPs based organic memory devices are almost the same. Current fluctuations appeared in the static current-voltage characteristic of An NPs capped with a 1-octadecanethiol (C18) based memory device. This feature is related to quantized charging and discharging of Au NPs because of the Coulomb repulsion between electrons confined in nanocrystals. (C) 2008 American Vacuum Society.