Preparation of Nickel Nanoparticles in Spherical Polyelectrolyte Brush Nanoreactor and Their Catalytic Activity

Nickel nanoparticles (Ni-NPs) with controlled size and narrow size distribution were successfully prepared in spherical poly (acrylic acid) (PAA) brushes (SPBs). The brushes act as nanoreactors for generating the Ni-NPs via adsorption of nickel ions in the brushes and subsequent reduction by addition of NaBH(4). The size of Ni-NPs can be well-controlled in several nanometers and with narrow size-distribution. Most interestingly, the size can be tuned by the reaction temperature: the average size increased from 3 to 7 nm upon increasing the reaction temperature from 273 to 303 K. The catalytic activity of these Ni-NPs trapped in SPBs were evaluated using a model reaction based on the reduction of 4-nitrophenol to 4-aminophenol by NaBH(4). The kinetic data were observed to follow the pseudofirst-order rate law, and the apparent rate constant was linearly dependent on the total surface area of the Ni-NPs and the reaction temperatures. This work opens a new way to prepare well-controlled Ni-NPs which should be ideal candidates for catalysts with high performance.