Single Metal of Silver Nanoparticles in the Microemulsion for Recyclable Catalysis of 4-Nitrophenol Reduction

Abstract

Abstract. Size control of silver nanoparticles (Ag NPs) to improve monodispersity and recyclability is crucial for application in nanocatalysts. Hence, a novel and effective protocol for in-situ synthesis of Ag NPs in the microemulsion was proposed. The surfactant-stabilized microcavity in microemulsion can provide a nanoscale reactor that limits nucleation, growth, and agglomeration of the particles. Ag NPs of 540-640 nm were successfully grown and exhibited excellent catalytic activity with the apparent rate constant (k) of 0.59 min -1 and the activation energy (Ea) of 23.03 kJ mol -1 toward the reduction of 4-nitrophenol. Moreover, the catalyst could be easily recycled and showed excellent reusability after 6 cycles. So, the silver nanoparticles can be extended to an important metalcatalyzed reduction in chemical industry, which is of great significance for the sustainable development.Keywords: Silver nanoparticles, microemulsion, 4-NP, catalytic [22]. Especially, microemulsion synthesis has been demonstrated to be a very promising method due to its precise control on morphology and dimension of nanoparticles [22]. From the viewpoints of colloid and interface chemistry, there are two types of microemulsions, reversed (water/oil) and direct (oil/water) microemulsion [23][24][25]. These systems are transparent, isotropic liquid media composed of discrete, thermodynamically stable [20]. The surfactant-stabilized microcavity in microemulsion can provide a nanoscale reactor that limits nucleation, growth, and agglomeration of the particles [22]. Accordingly, we could use this method to get Ag NPs with a controlled dimension. IntroductionAs we all know that 4-nitrophenol (4-NP) shows one of the most notorious toxic pollutants in the industrial effluents [26]. 4-aminophenol (4-AP) is very useful and important in many applications including analgesic and antipyretic drugs, photographic development, corrosion inhibition, anticorrosion lubrication, hair-dyeing agent etc [27]. Therefore enormous current interests have arisen in the development of catalysts for reduction of the 4-NP to 4-AP [28][29][30]. Traditional methods for this process usually involve reduction/catalytic hydrogenation [31][32][33][34][35]. Considering these aspects, sizecontrolled synthesis of Ag NPs for 4-NP transformations in a simple, cost-effective, and selective manner is highly demanding [26].We herein report our new efforts to synthesize Ag nanoparticles by the microemulsion method. Through our research, most of catalysts were alloy or compound of silver nanoparticles traditionally. A single metal of Ag NPs were manufactured in our work through a simple and fast method. In this system, o-phenylenediamine (oPD) was used as a weak reductive agent, who has been employed to produce silver

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Rapid Catalytic Reduction of 4-Nitrophenol and Clock Reaction of Methylene Blue using Copper Nanowires

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