Optical oxygen-sensing properties of porphyrin derivatives anchored on ordered porous aluminium oxide plates.

An optical oxygen-sensing activity of anchored porphyrin derivatives on ordered porous aluminium oxide plates was studied in relevance to development of new oxygen-sensing systems. Porphyrin derivatives, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrin, 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrin, 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrin, and their platinum complexes, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrinatoplatinum(II), 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrinatoplatinum(II), 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrinatoplatinum(II), were synthesized and anchored by an equilibrium adsorption method on aluminium oxide plates, which were prepared by an anodic oxidation. The excitation spectra of the porphyrin-anchored layers showed a broadened and blue-shifted Soret band compared with the corresponding porphyrins in DMSO. The luminescence intensity decreased with increasing oxygen concentrations. The oxygen-sensing ability estimated from I(0)/I(100) (I(0) and I(100) denote the luminescence intensity in 0 and 100% oxygen) was 9.08, 6.78, 8.71, 81.9, 35.5, and 39.1, which are greater than those of corresponding porphyrin derivatives in DMSO under the measured conditions, and indicates the remarkable enhancement effect of platinum(II). Non-linear Stern-Volmer plots were well fitted by the two component system to give the oxygen-sensitive constant (K(SV1)/%(-1)), the oxygen-insensitive constant (K(SV2)/%(-1)), and the former contribution (f(1)): 0.232, 3.32 x 10(-2), and 0.642; 0.141, 2.05 x 10(-2), and 0.687; 0.143, 1.05 x 10(-2), and 0.882; 17.3, 7.04 x 10(-3), and 0.980; 10.2, 1.43 x 10(-2), and 0.935; 16.3, 8.35 x 10(-3), and 0.954. The response time for the change of the atmospheric gas from argon to oxygen was 9.4 s, 12.5 s, 9.6 s, 5.0 s, 8.9 s, and 4.6 s, indicating the shortening effect of platinum. The reverse effect of platinum was observed in the change from oxygen to argon: 15.5 s, 17.0 s, 20.8 s, 667.4 s, 590.1 s, and 580.4 s, indicating the specific interaction of oxygen to the platinum(II) center.