Optical Properties of Gold−Silver Iodide Nanoparticle Pair Structures

Abstract

Nanoparticle pair structures composed of metal (Au) and semiconductor (AgI) segments with radii ca. 16 nm have been prepared in porous anodic aluminum oxide via electrochemical template synthesis. The metal and semiconductor members can be prepared such that they are in contact or separated in the porous host. UV/visible spectra of composites in which the Au and AgI segments are in contact show a red-shifted and broadened Au particle plasmon resonance band and the absence of the AgI exciton peak normally observed at λ = 425 nm. A blue shift in the Au particle plasmon band and the reappearance of the AgI exciton peak occur as the average interparticle spacing is increased. The changes in plasmon resonance peak position are consistent with an increased probability of Au and AgI intermixing as the spacing parameter d12 is decreased. The absence of the AgI exciton peak in the case of contacting Au and AgI particles is consistent with a large increase in the effective static dielectric constant upon phase inte...