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 µm, and their surface is modified by introducing sulfonic acid groups (SO 3−) to give an ion exchange capacity of up to 2.25 mequiv. · g−1, which provides 1.289 × 1010 SO 3− 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 PS surface. Assuming that approximately three SO 3− 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.