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Issue 95, 2015
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A soft-template mediated approach for Au(0) formation on a heterosilica surface and synergism in the catalytic reduction of 4-nitrophenol

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Abstract

Under suitably controlled conditions a cationic surfactant e.g. cetyltrimethylammonium bromide (CTAB) forms bilayers on a silica surface, which has the unique property of solubilizing organic molecules through ‘adsolubilization’. This property is judiciously exploited to adsorb AuCl4 ions on the modified silica surface at much higher loading (compared to normal silica) through the formation of a CTA+ AuCl4 complex on the silica support. Next, gold nanoparticles supported on the surfactant-modified silica (SMS) are prepared using two methods: (1) UV illumination and (2) borohydride reduction, and the materials are designated as SMSG-1 and SMSG-2. Characterization of the particles confirms the formation of Au(0) nanoparticles on the SMS surface. The particles have a spherical shape with an average size of 37 ± 11 and 54 ± 14 nm for SMSG-1 and SMSG-2, respectively. They exhibit much higher catalytic activity when compared to Au(0) supported on normal silica for 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) reduction in a borohydride medium. Such synergism is presumed to be due to the surfactant bilayer, which provides a high concentration of 4-nitrophenolate ions near the Au(0) nanoparticles embedded on the SMS leading to highly efficient contact between them. The reductions under different conditions are studied and compared. SMSG-1 shows better performance when compared to SMSG-2. While the reaction followed a pseudo-first order for SMSG-1 for all experimentally studied conditions, a clear change over in order from first to second was noticed for SMSG-2 under certain conditions. The reaction rates, recyclability and turn over frequency (TOF) with a growing micro-electrode (GME) and a fully grown micro-electrode (FGME) are compared. The GME shows ∼9 times higher catalytic activity as compared to the FGME.

Graphical abstract: A soft-template mediated approach for Au(0) formation on a heterosilica surface and synergism in the catalytic reduction of 4-nitrophenol

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Supplementary files

Article information


Submitted
18 Aug 2015
Accepted
01 Sep 2015
First published
03 Sep 2015

RSC Adv., 2015,5, 78006-78016
Article type
Paper
Author version available

A soft-template mediated approach for Au(0) formation on a heterosilica surface and synergism in the catalytic reduction of 4-nitrophenol

P. Mahamallik and A. Pal, RSC Adv., 2015, 5, 78006
DOI: 10.1039/C5RA16655A

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