Photochemical and Electrochemical Oxidation Reactions of Surface-Bound Polycyclic Aromatic Hydrocarbons

Abstract

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.

Electrochemical and photocatalytic reactions of polycyclic aromatic hydrocarbons investigated by raman spectroscopy

“…At 1.1 V, the characteristic vibrational modes of pyrene are no longer observed. The observed oxidation potential agrees with the work of Marzur and Banchard, 11 where the voltammetric curves of aminopyrene covalently attached to gold were examined. Electrochemical data revealed that surface bonded aminopyrene undergoes oxidation at ca.…”

“…The most stable anthraquinones are those with two carbonyl groups in the same ring. 11 Characteristic photoproduct vibrational modes (i.e., 1031, 1600 and 1665 cm -1 ) can be assigned to 9,10-anthraquinone. 12 This intermediate product has also been observed in the photocatalytic degradation of saturated anthracene aqueous solutions over thin films of porous TiO 2 .…”

“…These radicals can follow a variety of reaction pathways, including the introduction of hydroxyl and carbonyl groups into the ring system. 11,18 Several compounds, such as 1,6-pyrene-dione and 1,8-pyrene-dione, have been suggested as initial pyrene photochemical products. 18 These molecules are potential intermediate products for the reaction studied here and may give rise to the spectral pattern observed in Figure 6.…”

Spectroscopic and electrochemical characterization of interfacial biomimetic assemblies on electrochemically generated gold oxide surfaces

“…Therefore, the electrochemical surface coverage may represent a lower limit for the amount of adipoyl chloride on the gold oxide surface. Similar or even smaller coverage reported in our earlier work on gold and on ITO [23,44] enabled us to form hybrid bilayers with an external leaflet made out of phospholipids, proving the feasibility of such systems in biomimetics. Further studies are under way to determine other factors that can affect the adlayer density and organization.…”

Electrochemical and Optical Behavior of 8‐Hydroxypyrene‐1,3,6‐trisulfonic Acid at Optically Transparent Electrodes

“…Due to the resemblance of the CVs of thin layers of HPTS to that shown for thin layers of 1-OHP [39,40], the sulfonate groups of HPTS do not appear to substantially affect HPTS electrolysis. Therefore, the products of HPTS electrolysis in acidic aqueous solutions should be of similar structure to the oxidation products of 1-OHP.…”