Trapping and release of citrate-capped gold nanoparticles

► Gold nanoparticles are attracted to the surface of aminoalkanethiolated gold electrodes and electrostatic interactions hold them in place. ► Impedance spectroscopy, cyclic voltammetry and UV–Vis spectroscopy measurements confirm the presence on the surface of the electrodes. ► Release of the surface-bound gold nanoparticles is exerted when a negative bias is applied. ► Partial release of gold nanoparticles is attained and monitored using cyclic voltammetry in situ, UV–Vis spectroscopy and atomic force microscopy. An electrical method to trap and release charged gold nanoparticles onto and from the surface of gold electrodes modified by an alkanethiol self-assembled monolayer (SAM) is presented. To form electrodes coated with gold nanoparticles (GNPs), amine-terminated SAMs on gold electrodes were immersed in a solution of negatively charged citrate-capped GNPs. Accumulation of GNPs on the electrode surface was monitored by a decrease in the impedance of the SAM-modified electrode and by an increase in the electrochemical activity at the electrode as shown through cyclic voltammetry (CV). Electrostatic interactions between the GNPs and the amine-terminated SAM trap the GNPs on the electrode surface. Application of a subsequent negative bias to the electrode initiated a partial release of the GNPs from the electrode surface. Impedance spectroscopy, cyclic voltammetry, ultraviolet–visible (UV–Vis) spectroscopy and atomic force microscopy (AFM) were used to monitor and confirm the attraction of GNPs to and release from the aminealkanethiolated gold electrodes. This work describes a method of trapping and release for citrate-capped GNPs that could be used for on-demand nanoparticle delivery applications such as in assessing and modeling nanoparticle toxicology, as well as for monitoring the functionalization of gold nanoparticles.