Water-dispersible tryptophan-protected gold nanoparticles prepared by the spontaneous reduction of aqueous chloroaurate ions by the amino acid

P. R. Selvakannan, Saikat Mandal, Sumant Phadtare, Anand Gole, Renu Pasricha, S. D. Adyanthaya, Murali Sastry

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The synthesis of water-dispersible amino-acid-protected gold nanoparticles by the spontaneous reduction of aqueous chloroaurate ions by tryptophan is described. Water-dispersible gold nanoparticles may also be obtained by the sequential synthesis of the gold nanoparticles by borohydride reduction of chloroauric acid followed by capping with tryptophan. Comparison of the proton NMR spectroscopic signatures from the tryptophan-protected gold nanoparticles obtained by the two processes indicated that the indole group in tryptophan is responsible for reduction of the aqueous chloroaurate ions. The reduction of the metal ions is accompanied by oxidative polymerization of the indole group of the tryptophan molecules and, consequently, some degree of cross-linking of the gold nanoparticles.

Original languageEnglish
Pages (from-to)97-102
Number of pages6
JournalJournal of Colloid and Interface Science
Issue number1
Publication statusPublished - 1 Jan 2004
Externally publishedYes


  • Amino acids
  • Electrostatic stabilization
  • Nanoparticles
  • NMR
  • Surface modification

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