Photoreduction at a distance: facile, nonlocal photoreduction of Ag ions in solution by plasmon-mediated photoemitted electrons.

Surface-immobilized, densely packed gold nanoparticles in contact with aqueous silver ions and exposed to red light rapidly photoreduce silver ions in solution producing radially symmetric metal deposits with diameters many times larger than the diameter of the illuminating laser beam. The average particle sizes in the deposit increase with radial distance from the center of the deposit. This reduction-at-a-distance effect arises from surface-plasmon-mediated photoemission, with the photoemitted electrons conducting along percolating silver pathways, reducing silver ions along these conducting channels and especially at their periphery, thereby propagating the effect of the illuminating laser outward.