Preparation of Ni nanoparticles by liquid-phase reduction to fabricate metal nanoparticle–polyimide composite films

Nickel-nanoparticle-containing polyimide composite films were prepared by liquid-phase reduction of Ni(2+) ions with potassium borohydride (KBH(4)). The nanoparticles were amorphous with diameters of approximately 10–20 nm, depending on the KBH(4) concentration and reduction temperature. At high KBH(4) concentrations, the nanoparticles appeared to contain various nickel boride species. The number of nanoparticles and Ni content both increased upon repeated adsorption/reduction of Ni(2+) ions, where the particle growth was inhibited by the rigid polymer chain and the formation of smaller particles was favored.