A rationale on the role of intermediate Au(III)–vitamin C complexation in the production of gold nanoparticles
Preparation of gold nanoparticles, particularly gold nanorods, by wet chemistry processes involves gold seeds, an Au(III) salt, structure directing surfactants, and metal ion additives in the growth solution into which a weak reducing agent is added. The most commonly employed weak reducing agent is l-ascorbic acid (vitamin C) which is known to reduce many metal ions in the solution phase and form complexes with relatively low stability constants. A purple-gray gold–ascorbate compound, obtained from the reaction of sodium tetrachloroaurate(III) with sodium ascorbate, is now reported. The compound possesses the expected structural features of vitamin C–metal complexes as verified by its 13C CP-MAS NMR spectrum. A discussion is also presented on the possibility of gold–ascorbate complexation operating in gold nanoparticle formation.
KeywordsGold nanoparticles Gold colloids Vitamin C Ascorbate complexes Nanoparticle synthesis
The author is grateful to Dr. Laura Linati (University of Pavia) for the record of the NMR spectrum.
- Bauernfeind JC (1982) Ascorbic acid technology in agricultural, pharmaceutical, food and industrial applications. In: Seib PA, Tolbert BM (eds) Ascorbic acid: chemistry, metabolism and uses, Advances in Chemistry Series No. 200. American Chemical Society, Washington, DC, pp 418–423Google Scholar
- Bielski BHJ (1982) Chemistry of ascorbic acid radicals. In: Seib PA, Tolbert BM (eds) Ascorbic acid: chemistry, metabolism and uses, Advances in Chemistry Series No. 200. American Chemical Society, Washington, DC, pp 81–100Google Scholar
- Casas JS, Castano MV, Garcia-Tasende MS, Perez-Alvarez T, Sanchez A, Sordo J (1996) Compounds of l(+)-ascorbic acid with dimethylthallium(III), dimethyltin(IV) and dibutyltin(IV). Synthesis, solid-state spectroscopy (CP/MAS 13C NMR and IR), and multi-NMR behavior in aqueous solution. J Inorg Biochem 61:97–108. doi: 10.1016/0162-0134(95)00034-8 CrossRefGoogle Scholar
- Herbert RW, Hirst EL, Percival EDV, Reynolds RJW, Smith F (1933) The constitution of ascorbic acid. J Chem Soc 1270–1290. doi: 10.1039/jr9330001270
- Martell AE (1982) Chelates of ascorbic acid. Formation and catalytic properties. In: Seib PA, Tolbert BM (eds) Ascorbic acid: chemistry, metabolism and uses, Advances in Chemistry Series No. 200. American Chemical Society, Washington, DC, pp 152–156Google Scholar
- Miranda OR, Dollahon NR, Ahmadi TS (2006) Critical concentrations and role of ascorbic acid (vitamin C) in the crystallization of gold nanorods within hexadecyltrimethyl ammonium bromide (CTAB)/tetraoctyl ammonium bromide (TOAB) micelles. Crystallogr Growth Des 6:2747–2753. doi: 10.1021/cg060455l CrossRefGoogle Scholar
- Niidome Y, Nishioha K, Hawasaki H, Yamada S (2003) Rapid synthesis of gold nanorods by the combination of chemical reduction and photoirradiation processes; morphological changes depending on the growing processes. Chem Commun (Camb) 2376–2378. doi: 10.1039/b307836a
- Pudephatt RJ, Vittal JJ (1994) Gold: inorganic & coordination chemistry. In: King RB (ed) Encyclopedia of inorganic chemistry, vol 3. Wiley, Chichester, pp 1320–1331Google Scholar