Colloids and Surfaces A: Physicochem. Eng. Aspects 377 (2011) 356–360 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journal homepage: www.elsevier.com/locate/colsurfa Microwave-assisted synthesis of silver nanoparticles using poly-N-isopropylacrylamide/acrylic acid microgel particles Aslam Khan ∗ , Ahmed Mohamed El-Toni, Salman Alrokayan, Mohamad Alsalhi, Mansour Alhoshan, Abdullah S. Aldwayyan King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia article info Article history: Received 28 November 2010 Received in revised form 12 January 2011 Accepted 13 January 2011 Available online 1 February 2011 Keywords: Microwave Silver nanoparticles Copolymer Microgel abstract Microgel particles based on poly(N-isopropylacrylamide-co-acrylic acid) were prepared by emulsion polymerization in the presence of N,N ′ -methylenebisacrylamide. The microwave technique was adopted for the preparation of highly stable and monodisperse silver nanoparticles (Ag NPs) using these microgels as a template via in situ reduction of silver nitrate in the presence of glucose as a reducing agent. The prepared NPs were characterized by UV–vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform IR, and X-ray diffraction. The formation of Ag NPs was confirmed by the appearance of a surface plasmon absorption maximum at 429 nm. TEM showed that the spherical particles had an average diameter of 8.5 nm. The as-prepared Ag NPs were stable for more than 8 months at room temperature. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Ag NPs, as a significant number of noble metal nanoparticles, have been demonstrated to be promising candidates because of their unique optical applications [1]. Many strategies have been developed for the preparation of silver colloids, such as radia- tion chemical reduction [2], microwave-assisted synthesis [3,4], chemical or photoreduction [5], and thermal decomposition in organic solvents [6]. These methods allow control of the size and concentration of the dispersed particles. However, the suc- cessful integration of Ag NPs into useful devices has been very limited. This lack of success is due to the fact that Ag is sensitive to surrounding chemicals, resulting in oxidization and significant degradation of Ag’s plasmonic properties. Moreover, in solution, Ag NPs aggregate due to van der Waals forces and the high surface energy [7]. To address some of these problems, a number of homopolymers [8] and functionalized block copolymers [9] have been used for the preparation of functional nanoparticles in an aqueous medium. Polymer-assisted synthesis of metal nanoparticles has received considerable attention. In general, water-soluble polymers such as gum arabic [10] and poly(acrylic acid) [11] are well known for their ability to coordinate with metal particles. Ag NPs can eas- ily form polymer-Ag nanocomposites with these polymers. Dong et al. [12] successfully fabricated poly(N-isopropylacrylamide- ∗ Corresponding author. Tel.: +966 1 467 8369; fax: +966 1 467 0662. E-mail address: aslamkhan@ksu.edu.sa (A. Khan). co-acrylic acid) (poly(NIPAAm-co-AAc))-stabilized Ag NPs within microgel particles using NaBH 4 as a reducing agent. Mohn et al. [13] reported the fabrication of Ag NPs in semi-interpenetrating network hydrogels made of poly(NIPAAm-co-sodium acrylate). Poly(N-isopropylacrylamide) (pNIPAAm) is a biologically friendly polymer because it is water soluble and has extremely low cyto- toxicity [14]. These properties allow a wide range of potential biomedical applications. Recent studies have revealed that poly- mers play an important role in the synthesis and long-term incorporation of metal NPs [15,16]. Polymers are excellent host systems for metal NPs, and polymers can stabilize NPs via the elec- trostatic interactions between the polymer’s functional groups and the NPs. Even though there is a well-established technique for the prepa- ration of metal NPs, it is necessary to develop more efficient methods of synthesis involving simplified preparation procedures with short reaction times. The use of microwave-assisted syn- thesis is especially important in this regard. It has been reported that microwave heating can effectively control the size distribu- tion in a narrower range within a shorter reaction time than the conventional heating due to homogeneous and rapid heating in the preparation of nanoparticles [17–19]. Furthermore, microwave heating provides direct heating independent of heat conduction and convection. The exact nature of microwave interaction with reactants during the synthesis of materials is somewhat unclear and speculative [17]. However, energy transfer from the microwaves to the materials is achieved through the interaction of microwave radiation with water or other solvents with high dielectric constant or solvents molecules with large dipole moments [20]. 0927-7757/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2011.01.042