In situ synthesis of Ag nanoparticles in polyelectrolyte multilayers

• Published in: Nanotechnology Vol. 18; no. 32; pp. 325601 - 325601 (7)
• Main Authors: Logar, Manca, Jancar, Boštjan, Suvorov, Danilo, Kostanjšek, Rok
• Format: Journal Article
• Language: English
• Published: IOP Publishing 15.08.2007
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/18/32/325601

Self-assembled multilayer thin films, fabricated by the sequential adsorption of appositively charged polyelectrolytes, were used as a template for the in situ nucleation and growth of silver (Ag) nanoparticles. Since weak polyelectrolytes have a pH-dependent degree of dissociation, the multilayer film formed of polyallylamine (PAH) and polyacryllic acid (PAA) at low pH values contains free carboxylic acid groups that do not electrostatically bind to the positive groups of PAH chains during the film assembly. These free acid groups in the polyelectrolyte multilayer film were used to bind the silver ions, which were subsequently reduced with a NaBH4 solution to form Ag nanoparticles. Electron-microscopy examination of the films and UV-vis spectroscopy showed that the concentration and size of the Ag nanoparticles are determined by the processing conditions of the multilayer assembly. Furthermore, due to the regeneration of the acid groups upon reduction, the synthesis process can be repeatedly cycled to increase the volume fraction of Ag in the polyelectrolyte multilayer films. After three reaction cycles, Ag nanoparticles with an average diameter of 7 nm at a volume fraction of 65% were obtained in the polyelectrolyte multilayers (PEMs).