Rapid Cationization of Gold Nanoparticles by Two-Step Phase Transfer.

Cationic gold nanoparticles offer intriguing opportunities as drug carriers and building blocks for self-assembled systems. Despite major progress on gold nanoparticle research in general, the synthesis of cationic gold particles larger than 5 nm remains a major challenge, although these species would give a significantly larger plasmonic response compared to smaller cationic gold nanoparticles. Herein we present the first reported synthesis of cationic gold nanoparticles with tunable sizes between 8-20 nm, prepared by a rapid two-step phase-transfer protocol starting from simple citrate-capped particles. These cationic particles form ordered self-assembled structures with negatively charged biological components through electrostatic interactions.