Deniz Chodari-Gharehpapagh, Saeed Zakavi
Hexaprotonated meso-tetra(aryl)porphyrins (aryl = 2-pyridyl, 3-pyridyl and 4-pyridyl) anchored to nanostructured Amberlyst 15, nanoAmbSO3H or the sodium salt (NanoAmbSO3Na) with an exceptionally high stability against oxidative degradation and a singlet oxygen quantum yield (ϕ Δ) of almost unity are reported as new porphyrin photosensitizers. UV-vis-NIR diffuse reflectance spectroscopy (DRS), FESEM/EDX/mapping, thermal gravimetric analysis (TGA) and nitrogen adsorption-desorption porosimetry analysis were used to characterize the nanocomposites. FESEM analysis showed an average particle size of less than 90 nm for the nanocomposites formed from the agglomeration of very small nanoparticles. The results of BET analysis were in agreement with the occupation of the smaller mesopores of the polymer by the nonplanar hexaprotonated porphyrins. The aerobic photooxidation of some environmental organic pollutants including Rhodamine B, Brilliant green and methyl phenyl sulfide was studied under aqueous conditions in the presence of the photosensitizers and their corresponding water soluble counterparts. The water-soluble hexaprotonated porphyrins showed much higher photocatalytic activity in short-term photooxidation of the organic dyes under homogeneous conditions. However, complete degradation of the porphyrins occurred in a short time interval (5 min). The polymer supported hexaprotonated porphyrins were much more efficient and stable than the non-immobilized counterparts towards oxidative degradation with singlet oxygen in both short- and long-term oxidation of the organic compounds. 1,3-Diphenylisobenzofuran as a specific chemical quencher of 1O2 (1Δg) was used to determine the singlet oxygen quantum yield (ϕΔ) of the photosensitizers. Interestingly, the hexaprotonated porphyrins immobilized on the neutralized polymer (nanoAmbSO3Na) showed approximately unity ϕ Δ and higher efficiencies than those supported on nanoAmbSO3H (0.20-0.46).