Mechanistic and kinetic study of the formation of silver nanoparticles by reduction of silver(I) in the presence of surfactants and macromolecules Iqbal M. Ismail 1,2 • Hassan A. Ewais 1 Received: 18 January 2015 / Accepted: 2 March 2015 Ó Springer International Publishing Switzerland 2015 Abstract The kinetics of formation of silver nanoparticles by reduction of silver(I) with galactose were studied spec- trophotometrically in the presence of surfactants and chi- tosan as stabilizing agents. The reaction was carried out under pseudo-first-order conditions by using a tenfold excess of [galactose] over [Ag ? ]. The effects of cetyltrimethylammonium bromide (cationic surfactant) and sodium dodecyl sulfate (anionic surfactant) on the reaction rate have been studied. Chitosan inhibits the rate of reaction by up to 70 %. TEM imaging shows that there is no aggre- gation of silver nanoparticles in the presence of chitosan. The rate of reaction increases with increasing [OH - ]. A mechanism for the reaction is proposed, and the rate equa- tion derived from this mechanism was consistent with the experimental behaviors. Thermodynamic activation pa- rameters were calculated. Introduction Natural polymers and biomolecules have been used for the preparation of nanosilver particles because they are nontoxic and biocompatible [1, 2]. Chitosan is a polysaccharide copolymer of N-acetyl-D-glucosamine and D-glucosamine, obtained by the alkaline deacetylation of chitin [3] obtained from crustaceans, such as shrimps, squids and crabs [4, 5]. It has been used as a nontoxic, biodegradable, biocompatible and environmental-friendly material with many superior properties [6]. Chitosan has many industrial applications in areas such as wastewater treatment, medicine, food and cosmetics [7–9]. It is also being studied for food packaging films, bone substitutes, artificial skin, biomedical applica- tions and pH-sensitive drug delivery [10]. Chitosan has also been used as a stabilizer for the preparation of metal nanoparticles [1]. Other stabilizing agents, such as cetyltrimethylammonium bromide (CTAB), sodium dode- cyl sulfate (SDS), Triton X-100 and poly(vinyl alcohol), are used as capping agents to control the shape and size of silver nanocrystals [11, 12]. Silver nanoparticles can be formed and stabilized by chemical and physical methods; chemical methods, such as electrochemical techniques, chemical reduction and pho- tochemical reduction, are most widely used [5, 13]. Che- mical reduction is the most used method for the formation of silver nanoparticles as stable, colloidal dispersions in aqueous or nonaqueous media [11]. The reduction in silver ion leads to the formation of silver atoms (Ag o ), which is followed by agglomeration into oligomeric clusters [14]. These clusters eventually form yellow colloidal silver nanoparticles in solution [14]. Silver nanoparticles have many applications in biotech- nology [15], medicine [16], catalysis and biochemistry [17]. There are many industrial applications of silver nanoparti- cles such as microelectronics, cosmetics, adhesives, catalysis and enhanced solar cells [17–19]. The formation of nanoparticles using biological entities has great importance in biotechnology due to their shape-dependent optical, electrical and chemical properties [15]. In this paper, the kinetics of formation of silver nanoparticles by reduction of silver ions with galactose in & Hassan A. Ewais hshalby2002@yahoo.com 1 Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia 2 Center of Excellence in Environmental Studies, King Abdulaziz University, P.O. Box 80216, Jeddah 21589, Saudi Arabia 123 Transition Met Chem DOI 10.1007/s11243-015-9926-1