Electrophoretic analysis of gold nanoparticles: size-dependent electrophoretic mobility of nanoparticles.

Efforts were made to realise a two-dimensional, on-line-coupled isotachophoresis-capillary zone electrophoresis system. The electrophoretic behaviour of gold nanoparticles was investigated with the idea that they could be used to improve the control of this electrophoretic set-up. The well-known citrate-ligated gold nanoparticles were not suitable for this application, because the ligand was desorbed, and the nanoparticle solutions were degraded. Therefore mercaptocarboxylic acids were used, because the chemisorption of thiols on the gold surface was improved. Isotachophoretic measurements were carried out with these nanoparticles. A size-dependent electrophoretic mobility was found according to theoretical predictions, and the surface and zeta-potential were discussed for the small particle range. A new method for concentration measurements of nanoparticles is presented by means of isotachophoresis.