Direct metallization of gold nanoparticles on a polystyrene bead surface using cationic gold ligands

Gold nanoparticles are formed to cover the surface of sulfonated-polystyrene (PS) beads by the in-situ ion-exchange and chemical reduction of a stable cationic gold ligand, which makes it different from the physical adsorption or multiple electroless metallization methods. PS beads are synthesized by dispersion polymerization with a diameter of 2.7 mu m, and their surface is modified by introducing sulfonic acid groups (SO3-) to give an ion exchange capacity of up to 2.25 mequiv. . g(-1), which provides 1.289 x 10(10) SO3- per bead. Subsequently, the anionic surface of the PS beads is incorporated with a cationic gold ligand, dichlorophenanthrolinegold(III) chloride ([AuCl2(phen)]Cl), through an electrostatic interaction in the liquid phase to give gold nanoparticles (ca. 1-4 nm in diameter) formed on the PSo surface. Assuming that approximately three SO3- groups interact with one [AuCl2(phen)](+) ion in the ion-exchange process, the gold coverage on a PS bead is estimated as 12.0 wt.-%, which compares well with the 16.8 wt.-% of gold loading measured by inductively coupled plasma-mass spectrometry. Because of the adjustable IEC values of the polymer surface and the in-situ metallization of Au in the presence of S atoms, both of which are of a soft nature, the developed methodology could provide a simple and controllable route to synthesize a robust metal coating on the polymer bead surface.