Trapping and release of citrate-capped gold nanoparticles

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.

► 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.