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

Abstract

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.

Inquiring the mechanism of formation, encapsulation, and stabilization of gold nanoparticles by poly(vinyl pyrrolidone) molecules in 1-butanol

“…Synthesis of therapeutic agent like gold nanoparticles (GNPs) of various architectures continues to be of immense academic and technical interest owing to possession of inimitable opto-electronic, magnetic, physical, chemical, and medicinal properties (Alexandridis 2011;Daniel and Astruc 2004;Hoppe et al 2006). However, all these properties strongly depend on the type of reducing and/or stabilizing agent used in the reaction medium, synthetic route, and reaction conditions (Alexandridis 2011;Daniel and Astruc 2004).…”

“…Out of various fundamental strategies, the two methods tested widely so far: (1) bottom-up and (2) top-down approach, the in situ synthesis of NPs by chemical reduction of gold ions in presence of a polymer matrix-a bottom-up technique, is an extensively used synthetic route to obtain stable GNPs in both aqueous and non-aqueous medium (Alexandridis 2011;Goy-López et al 2010;Xian et al 2012;Zhou et al 2009). Soon after the pioneer work of Helcher (1718) on the synthesis of GNPs in presence of a polysaccharide, scientists and academia felt that polymers could be used as efficient stabilizing/reducing agent in the development of inorganic-organic nanostructure materials of various morphologies and sizes of ones interest (Hoppe et al 2006;Goy-López et al 2010;Xian et al 2012;Zhou et al 2009). In the synthesis of metal NPs, the most commonly used polymers include poly(vinyl alcohol), poly(vinyl pyrrolidone) PVP, and poly (ethylene glycol) (Hoppe et al 2006;Goy-López et al 2010;Tripathy et al 2009;Xian et al 2012;Zhou et al 2009).…”

“…Soon after the pioneer work of Helcher (1718) on the synthesis of GNPs in presence of a polysaccharide, scientists and academia felt that polymers could be used as efficient stabilizing/reducing agent in the development of inorganic-organic nanostructure materials of various morphologies and sizes of ones interest (Hoppe et al 2006;Goy-López et al 2010;Xian et al 2012;Zhou et al 2009). In the synthesis of metal NPs, the most commonly used polymers include poly(vinyl alcohol), poly(vinyl pyrrolidone) PVP, and poly (ethylene glycol) (Hoppe et al 2006;Goy-López et al 2010;Tripathy et al 2009;Xian et al 2012;Zhou et al 2009). On the other hand, the increased interest on the use of PVP as capping/reducing/nucleating agent has been increased a lot owing to its non-toxicity, good biodegradability, excellent film forming ability and easy processability, superb stabilizing ability, mild reducing ability, and outstanding solubility in various polar solvents (Alexandridis 2011;Hoppe et al 2006;Xian et al 2012;Zhou et al 2009).…”

“…In the synthesis of metal NPs, the most commonly used polymers include poly(vinyl alcohol), poly(vinyl pyrrolidone) PVP, and poly (ethylene glycol) (Hoppe et al 2006;Goy-López et al 2010;Tripathy et al 2009;Xian et al 2012;Zhou et al 2009). On the other hand, the increased interest on the use of PVP as capping/reducing/nucleating agent has been increased a lot owing to its non-toxicity, good biodegradability, excellent film forming ability and easy processability, superb stabilizing ability, mild reducing ability, and outstanding solubility in various polar solvents (Alexandridis 2011;Hoppe et al 2006;Xian et al 2012;Zhou et al 2009). It was reported that PVP reduce gold ions to Au atom and subsequently encapsulate those metal NPs via O-atom of pyrrolidone ring (Hoppe et al 2006;Xian et al 2012;Zhou et al 2009).…”

“…On the other hand, the increased interest on the use of PVP as capping/reducing/nucleating agent has been increased a lot owing to its non-toxicity, good biodegradability, excellent film forming ability and easy processability, superb stabilizing ability, mild reducing ability, and outstanding solubility in various polar solvents (Alexandridis 2011;Hoppe et al 2006;Xian et al 2012;Zhou et al 2009). It was reported that PVP reduce gold ions to Au atom and subsequently encapsulate those metal NPs via O-atom of pyrrolidone ring (Hoppe et al 2006;Xian et al 2012;Zhou et al 2009). PVP forms a charge transfer (CT) complex with Pt NPs via nonbonding electron transfer from the O-atom to the electron-deficient NP (Borodko et al 2006).…”