Silica-Metal Core-Shells and Metal Shells Synthesized by Porphyrin-Assisted Photocatalysis

Uniform silica beads modified with a positively charged tin porphyrin (SnT(NMe4Py)P) adsorbed onto their surface are used as photocatalytically active templates to synthesize platinum and palladium shell and core-shell nanostructures. The cationic porphyrin SnT(NMe4Py)P serves a dual function, acting as both a photocatalyst to reduce metal ions and nucleate growth sites and as a surface modifier that promotes binding of platinum metal to the surface of the nanospheres. Hollow platinum nanoshells can then be produced by removing the silica cores using hydrofluoric acid. Magnetic silica-platinum core-shell spheres can also be prepared starting from silica spheres containing magnetite nanoparticles. The silica-porphyrin-platinum nanocomposites contain all the components necessary to produce hydrogen gas via a tin porphyrin-mediated reductive photocatalytic process using a sacrificial electron donor. However,. due to instability of the SnT(NMe4Py)P, hydrogen production can only be realized when a degradation-resistant water-soluble tin porphyrin photocatalyst (SnTPPS) is added to a solution containing the nanocomposites and an electron donor.