Synthesis and Characterization of Bimetallic Pd-Co Nano Magnetic Materials in Mesoporous Silica
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Synthesis and Characterization of Bimetallic Pd-Co Nano Magnetic Materials in Mesoporous Silica Balaji Tatineni1, Dhananjay Kumar2 , Joslyn Perkins1, Sergey Yarmolenko2 and Debasish Kuila1* 1 Department of Chemistry, North Carolina A & T State University, Greensboro, NC 27411 2 Center for Advanced Materials and Smart Structures (CAMSS), North Carolina A & T State University, Greensboro, NC 27411 *[email protected]; ph: 336-285-2243 ABSTRACT An one-pot procedure was developed for the synthesis of mesoporous silica containing bimetallic PdCo using Pd(NO3)2 and CoCl2, and cetyl trimethyl ammonium bromide (CTAB) as the templating agent, and tetramethoxy silane (TMOS) as the precursor. The materials were characterized using high resolution scanning transmission electron microscopy (HRSTEM), elemental analysis, X-ray diffraction (XRD), and magnetic measurements. The data indicate that the bimetallic Pd-Co nanoparticles are uniformly distributed on the inner pore walls of silica. The magnetic measurements of reduced Pd-Co nanoparticles (4-5 nm) in mesoporous silica reveal a typical ferromagnetic behavior up to 20 K and exhibit superparamagnetic properties above 30 K. INTRODUCTION Highly ordered mesoporous silica materials are considered to be promising host materials for the incorporation of different doping agents such as organic dyes, metallic nano structures, polymers and quantum dots. They exhibit properties towards potential applications in optics, catalysis, sensors, magnetic and electronics [1, 2]. Among all the doping agents, the materials containing metallic nanostructures are of wide interest due to its unique size-dependent magnetic, optical, and electrical properties. These materials exhibit better catalytic properties than their metallic counterparts [3-6]; among the noble and on-noble metals palladium and cobalt are most important - in view of their sovereign applications for many catalytic reactions. Although Pd and Co catalysts have shown promising results, the serious draw back in current synthesis conditions leads to deactivation of the catalyst and an increase in CO production. The inclusion of nanocrystals in to the mesoporous materials has been carried out previously in several ways. The precursors can be incorporated into the channels of mesoporous silica by sorption, phase transition, wetness impregnation, ion exchange, complexation and covalent grafting [7-15]. However, these procedures have serious drawbacks such as: adsorption of precursor on the external surface of silica that leads to growing the particles largely outside the mesopore, and weaken the properties of the material. Zhang et al [16] developed a method to deactivate the adsorption sites by grafting the external surface of the mesoporous silica with organic functional groups; but, the ability to control the doping quantity of the nanoparticles into mesostructures is very difficult. Thus, these problems suggest that better synthetic procedures of materials can play an important role to improve the properties of the nanostruct
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