Electrostatic Repulsion-Controlled Formation of Polydopamine–Gold Janus Particles

Haolan Xu *†, Xiaokong Liu †, Ge Su †, Bin Zhang ‡, and Dayang Wang *†

^† Ian Wark Research Institute, University of South Australia, SA 5095, Australia

^‡ Department of Chemistry, Tianjin University, Tianjin, 300072, P. R. China

Langmuir, Article ASAP

DOI: 10.1021/la302394e

Publication Date (Web): August 20, 2012

Copyright © 2012 American Chemical Society

*Tel: +61 8 83023596. Fax: +61 83023683. E-mail:haolan.xu@unisa.edu.au; dayang.wang@unisa.edu.au.

Polydopamine (PDA)–Au Janus particles were obtained by simply adding HAuCl₄ to a PDA particle suspension, prepared via self-polymerization of dopamine in basic solution at room temperature. The structures of the PDA–Au particles are readily controlled by electrostatic repulsion between the constituent particles, which can be realized simply via adjusting the environmental pH. PDA–Au Janus particles are formed only in a narrow pH range of 2.5–3.0 due to the properly enhanced electrostatic repulsion between the Au particles growing on as-prepared PDA particles and between the Au and PDA particles. The obtained PDA–Au Janus particles can become interfacially active and self-assemble at oil/water interfaces as a result of spatially well-separated hydrophilic (PDA) and hydrophobic (Au) domains on the surfaces, reminiscent of amphiphilic molecules