Mechanism of Au(III) reduction by chitosan: Comprehensive study with 13C and 1H NMR analysis of chitosan degradation products. (6th March 2015)

• Record Type: Journal Article
• Authors: Pestov, Alexander; Nazirov, Alexander; Modin, Evgeny; Mironenko, Alexander; Bratskaya, Svetlana
• Is Part Of: Carbohydrate polymers. Volume 117(2015)
• Page Start: 70
• Page End: 77
• Publication Date: 2015-03-06
• Subjects: Chitosan -- Gold nanoparticles -- Metal/polymer ratio -- Decarboxylation -- Depolymerization -- Formate; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2014.09.030
• Languages: English
• ISSNs: 0144-8617

Abstract

Highlights: Mechanism of Au(III) reduction by chitosan without external stimuli is proposed. Reducing species in chitosan/Au(III) solutions are chitosan hydrolysis products. Chitosan degrades to formate, chitooligosaccharides and glucosamine acids. Oxidative degradation of chitosan reduces its efficiency as stabilizer. Size of gold particle increases with increase of Au(III)/chitosan ratio. Abstract: The mechanism of Au(III) reduction by chitosan has been proposed on the basis of comprehensive study of kinetics of Au(III) reduction and chitosan chain degradation using UV–vis spectroscopy and viscosimetry, and identification of reaction products using colloid titration and 13 C, 1 H NMR spectroscopy. We have shown that formation of gold nanoparticles in H[AuCl4 ]/chitosan solutions starts with hydrolysis of chitosan catalyzed by Au(III). The products of chitosan hydrolysis rather than chitosan itself act as the main reducing species. According to 13 C and 1 H NMR spectroscopy data, chitosan/Au(0) composites contain chitosan with reduced molecular weight and acetylation degree, whereas water-soluble by-products consist of chitosan oligomers with higher acetylation degree, derivatives of glucosamine acids, and formate ion. Chitosan degradation has significantly contributed to the decrease of its efficiency as a gold nanoparticles stabilizer. The gold particle size increased from 6.9 nm to 16.2 nm, when Au(III)/chitosan molar ratio changed from 1:80 to 1:10.