A versatile hydrogel template for metal nano particle preparation and their use in catalysis Sultan Butun a , Nurettin Sahiner a, b, * a Canakkale Onsekiz Mart University, Faculty of Sciences and Arts, Chemistry Department, Terzioglu Campus,17100 Canakkale, Turkey b Nanoscience and Technology Research and Application Center (NANORAC), Terzioglu Campus,17100 Canakkale, Turkey article info Article history: Received 9 June 2011 Received in revised form 11 August 2011 Accepted 13 August 2011 Available online 22 August 2011 Keywords: Hydrogel reactor Flexible nanonetwork In situ metal catalysts abstract We report the synthesis of a novel bulk hydrogel based on acrylamidoglycolic acid (AAGA) and its use as a template in the preparation of different metal nanoparticles. Furthermore, we demonstrate the efficient utilization of p(AAGA) composite hydrogel as a reactor vessel in the reduction of an organic contaminant, 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The swelling characteristics of the hydrogel at different pH and different concentrations of salts (NaNO 3, NaCI) were studied, and experimental molecular mass between crosslink (M c ) values was calculated. Experimental parameters that affect the 4-NP reduction rate such as temperature, amount of catalysis, co-catalysis, concentrations of 4-NP and of NaBH 4 were investigated. The kinetics of the reduction reaction under different reaction conditions was also evalu- ated to determine the activation parameters. Activation energy for the reduction of 4-NP was 33.783 kJ mol 1 and p(AAGA)eAg composites possessed 88% activity at the end of five repetitive uses. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Hydrophilic gels, called hydrogels, are crosslinked materials capable of absorbing a large amount of water without dissolving. When fully hydrated, they can contain over 95% water and there- fore, water load can be easily handled. They have tunable degrees of swelling in response to changes in ionic strength, pH, pressure, temperature, light, electric and magnetic fields in their environ- ment [1e8]. These soft, flexible and versatile materials are used in many applications; in water purification and separation [9e11], as active agent delivery vehicles (drugs, protein, and gene) [4,12,13], catheters [14], contact lenses [15], artificial organs [16], sensors [17] and actuators responding to various stimuli [18]. Hydrogels have also been used as a template for the preparation and protection of metal nanoparticles [19]. Metal nanoparticles have been exten- sively investigated due to their unique physical and chemical properties and wide range of potential applications. Silver nano- particles, in particular, can be used as catalyst, refrigeration dilution agent, immunity sensors and antimicrobial materials [20,21]. At present, there are lots of techniques available for the synthesis of metal nanoparticles [22e27]. However, the key issues with these techniques are the control of particle size and prevention of agglomeration, which is very important in application [28]. In this paper, a new method is put forward for the production of Ni, Cu, Co and Ag nanoparticles by using p(AAGA) as an active template. Moreover, this p(AAGA)eAg composite is used as a reaction medium in the reduction of 4-nitrophoenol (4-NP) to 4-aminophenol (4-AP). Nitrophenols, one of the derivatives of phenols, are present in high levels in the effluents from numerous industries including chemical, petrochemical, pharmaceutical, refineries, oil field activities, coal processing, olive oil production, etc [29e31]. Phenol is toxic to humans and causes headaches, fainting, vertigo and mental disturbance. Additionally, it can cause several severe ecological and environmental problems in receiving environments. In recent years much effort has been expended to develop methods to remove aromatic pollutants from wastewater. Nowadays there is a wide choice of techniques available, including activated carbon adsorption, electrochemical, ozonation, biological and chemical procedures, all of which should be economical, environmentally friendly, biodegradable and so on [29,32]. In the present work, we have synthesized a novel homopolymeric p(AAGA) hydrogel for the first time and studied their swelling characteristics at different pH and salt solutions. The experimental molecular masses between crosslink (M c ) values were calculated. Moreover, p(AAGA) hydrogels utilization as a reactor was demon- strated by employing in situ prepared Ag nanoparticles in the reduction of 4-nitrophenol in an aqueous sodium borohydride * Corresponding author. Canakkale Onsekiz Mart University, Faculty of Sciences and Arts, Chemistry Department, Terzioglu Campus, 17100 Canakkale, Turkey. Tel.: þ90 2862180018 2041; fax: þ90 2862181948. E-mail address: sahiner71@gmail.com (N. Sahiner). Contents lists available at SciVerse ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2011.08.021 Polymer 52 (2011) 4834e4840