Synthesis of silver particle supported on polysiloxane: Characterization and catalytic application in reduction of para nitrophenol

Noble metallic nanoparticles (Au, Ag, Pt, etc.) have attracted extensive attention due to their optical and electronic properties and potential utility in catalysis. Among these noble metallic nanoparticles, Ag is particularly attractive because of its much lower cost. In particular, its application in catalysis is most important since it often combines the characteristics of high reactivity and selectivity. There are many reactions catalyzed by Ag, such as oxidative conversion of methanol into formaldehyde, 4 selective butadiene epoxidation5 and oxidation of D-glucose. Especially, the 4-nitrophenol (4-NP) reduction by borohydride in the presence of Ag catalysts has been accepted as an alternative effective and eco-friendly route to produce 4- aminophenol (4-AP) in industry [1]. Catalytic reduction of 4-nitrophenol: In order to study the catalytic activity of the as synthesized particles 25 mL of 4-NP (0.12 mmol/L) aqueous solution were stirred with freshly prepared NaBH4 solution (25 ml, 60 mmol/L). Then 5 mg, 10 mg, 15 mg of micron-SiO2 nano-Ag particles were added into the flask, respectively. As the reaction proceeded, the color of the solution changed gradually from yellow to colorless at room temperature. UV–vis absorption spectra were recorded with a time interval of 45 min, 10 min, 7 min, respectively, to monitor the change of the reaction mixture at room temperature. In comparison with free Ag NPs the Ag-SiO2 NCs exhibited a better catalytic activity for the reduction of 4-nitrophenol at room temperature. The final products were thoroughly characterized by Fourier Transform Infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) along with Energy Dispersive X-ray (EDX) Spectroscopy, thermo gravimetric and differential thermal analysis (TG/DTA) and X-ray photoelectron spectroscopy (XPS) [2].