One-Step Synthesis of Gold and Silver Hydrosols Using Poly(N-vinyl-2-pyrrolidone) as a Reducing Agent

• Published in: Langmuir Vol. 22; no. 16; pp. 7027 - 7034
• Main Authors: Hoppe, Cristina E, Lazzari, Massimo, Pardiñas-Blanco, Iván, López-Quintela, M. Arturo
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2006
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Water; Gold; Shape; Hydrosol; Nanoparticle; Metal ion; Polymer; Transition metal; Decomposition; Mechanism; Degradation; Particle; Chemical reduction; Silver; Hydrogen abstraction; Synthesis; Optical properties; Peroxides; Aqueous solution; Colloidal sol; Low temperature
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la060885d

Synthesis of gold and silver hydrosols was carried out in a one-step process by reduction of aqueous solutions of metal salts using poly(N-vinyl-2-pyrrolidone) (PVP). Both kinds of metal nanoparticles were obtained without the addition of any other reducing agent, at low temperatures and using water as the synthesis solvent. Shape, size, and optical properties of the particles could be tuned by changing the employed PVP/metal salt ratio. It is proposed that PVP acts as the reducing agent suffering a partial degradation during the nanoparticles synthesis. Two possible mechanisms are proposed to explain the reduction step:  direct hydrogen abstraction induced by the metal ion and/or reducing action of macroradicals formed during degradation of the polymer. Initial formation of the macroradicals might be associated with the metal-accelerated decomposition of low amounts of peroxides present in the commercial polymer.