Synthesis, spectroscopy, and photophysics of porphyrins attached to gold nanoparticles via one or two linkers

Abstract

Four new meso-tetraphenylporphyrin derivatives were prepared, singly and doubly substituted with thiocarbamate and thioacetate groups. These compounds were subsequently attached to gold nanoparticles suspended in chloroform. Very different kinetics of the attachment were revealed; the process was much faster for the thiocarbamate derivatives. Spectral, photophysical, and scanning electron microscopy studies revealed large differences in the morphology of the gold–porphyrin systems. The porphyrins with one linker attach to single nanoparticles, whereas the dual linker derivatives induce formation of aggregates, characterized by readily detectable Raman signals. A "hot-spot" type structure is proposed for the latter, with the porphyrin bridging two gold nanoparticles.