Fibrous nano-silica containing immobilized Ni@Au core-shell nanoparticles: A highly active and reusable catalyst for the reduction of 4-nitrophenol and 2-nitroaniline

A novel, dandelion-like fibrous nano-silica catalyst (Ni@Au/KCC-1) has been synthesized by modifying fibrous nano-silica (KCC-1) with Ni@Au core-shell nanoparticles (NPs). KCC-1 was prepared using a hydrothermal method and has a dandelion-like shape, high surface area, and easy accessibility; KCC-1 can also be functionalized with 3-mercaptopropyltriethoxysilane. The mercaptopropyl groups on the fibers act as robust anchors for the immobilization of Ni@Au NPs, thus preventing the aggregation of the Ni@Au NPs. We investigated the catalytic performance of the Ni@Au/KCC-1 nanocatalyst by reducing 4-nitrophenol to 4-aminophenol in the presence of NaBH4 as a probe reaction. The resulting Ni@Au/KCC1 nanocatalyst exhibited superior catalytic activity to Ni@Au NPs, which may be attributed to the high accessibility of the KCC-1 support material. To some extent, it also may be due to the poor aggregation of Ni@Au NPs on the KCC-1 nano-silica support. The Ni@Au/KCC-1 nanocatalyst also showed high catalytic activity when used to reduce 2-nitroaniline. It is noteworthy that using Ni cores to fabricate the active sites Ni@Au NPs resulted in a lower amount of Au needed than is typical, because most of the Au-NPs catalyzed reactions occur on the surfaces of the NPs. In addition, the Ni cores give the Ni@Au/KCC-1 nanocatalyst superparamagnetic properties that increase its ease of recovery by a powerful magnet, allowing for it to be reused. The abovementioned approach based on fibrous KCC-1 and Ni@Au NPs provided a useful platform for the fabrication of noble-metal-based nanocatalysts with easy accessibility and a low cost, which may allow for an efficient green alternative for various catalytic reductions. (C) 2014 Elsevier B.V. All rights reserved.