Photochemical and electrochemical oxidation reactions of surface-bound polycyclic aromatic hydrocarbons

We have studied the oxidation reactions of two polycyclic aromatic hydrocarbons (PAHs), pyrene and anthracene, attached covalently to silica, indium-doped tin oxide (ITO), and gold surfaces. Attachment of the PAHs to the substrates was accomplished by established covalent coupling methods. For both pyrene and anthracene, we find that electrochemical and photochemical oxidation produces first a monohydroxy-PAH followed by the formation of dihydroxy/dione derivatives. We have used cyclic voltammetry and steady-state excitation and emission spectroscopy to identify the products of the surface reactions. The uniformity of our results for two chromophores and three different types of substrates demonstrates the generality of our findings and rules out the involvement of surface enhancement phenomena in these processes.