Catalytic reduction of 4-nitrophenol over biostabilized gold nanoparticles supported onto thioctic acid functionalized silica-coated magnetite nanoparticles and optimization using response surface methodology

Abstract

An environmentally benign magnetic gold nanoparticles (AuNPs) catalyst supported onto thioctic acid functionalized silica-coated magnetite nanoparticles, Au–RS–SR–NH–SiO₂–Fe₃O_4,without employing any toxic reductant or capping agent was successfully synthesized. The Phaleria macrocarpa (Scheff.) Boerl (P. macrocarpa) fruit aqueous extract was used as the reducing and stabilizing agents for the biosynthesis of AuNPs. The catalytic performance of the magnetic AuNPs catalyst was evaluated for the reduction of 4-nitrophenol into 4-aminophenol in the presence of NaBH₄. A three-factor Box–Behnken design coupled with response surface methodology was applied to evaluate the effects of several operating parameters, namely, volume of NaBH₄, 4-nitrophenol concentration, and weight of Au–RS–SR–NH–SiO₂–Fe₃O₄ on the conversion of 4-nitrophenol. The reduction of 4-nitrophenol using Au–RS–SR–NH–SiO₂–Fe₃O₄ was welldescribed by a quadratic polynomial model. A significant quadratic model with p value ˂.0001 and R ² = 0.9958 was achieved using the analysis of variance (ANOVA). The conversion of 4-nitrophenol to 4-aminophenol was maintained at 90% after five cycles.

Keywords:

• Biosynthesis
• gold nanoparticles
• magnetic catalysts
• 4-nitrophenol
• response surface methodology

Additional information

Funding

The authors gratefully acknowledged for the financial support from the Ministry of Higher Education (MOHE) Malaysia and Universiti Teknologi Malaysia (UTM) through research funding Vot Number 07H16 and 12H53. N. F. Abd Razak is thankful to MOHE for a studentship received through the MyPhD program.