Pd Nanoparticles in Assembled Silica Microcapsules

Significance

Encapsulated Pd nanoparticles were prepared in microcapsules which were formed by self-assembly of silica nanoparticles and polyamines. Thus, treatment of poly-l-lysine with trisodium citrate solution led to polymer aggregates via the polyamine-mediated self-assembly. These positively charged aggregates facilitated the assembly of negatively charged silica nanoparticles to form microcapsule 1. Addition of Na₂PdCl₄ to 1 gave the ionic salt of [PdCl₄]^²- and the positively charged polyamines in the microcapsule 2. The entrapped Pd ions were reduced with NaBH₄ to give Pd encapsulated microcapsule 3. The catalytic activity of 3 was evaluated in hydrogenation of nitroarenes under H₂ atmosphere at room temperature, giving the corresponding anilines in 60-99% conversion (4 examples).