Preparation and Characterization of a Porphyrin Self-Assembled Monolayer with a Controlled Orientation on Gold

A porphyrin-incorporated self-assembled monolayer (SAM) on gold, in which the macroplane of the porphyrin molecule assumes a nearly flat orientation with respect to the surface of the Au substrate, was prepared by formation of a 4-pyridinethiol SAM on gold followed by axial ligation of metalloporphyrin (CoTPP) to it. The porphyrin SAM was characterized by surface-enhanced Raman scattering (SERS) and electrochemical techniques.