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

Abstract

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 (1_H), 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrin (2_H), 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrin (3_H), and their platinum complexes, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrinatoplatinum(II) (1_Pt), 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrinatoplatinum(II) (2_Pt), 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrinatoplatinum(II) (3_Pt), 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 I₀/I₁₀₀ (I₀ and I₁₀₀ denote the luminescence intensity in 0 and 100% oxygen) was (1_H) 9.08, (2_H) 6.78, (3_H) 8.71, (1_Pt) 81.9, (2_Pt) 35.5, and (3_Pt) 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 (f₁): (1_H) 0.232, 3.32 × 10⁻², and 0.642; (2_H) 0.141, 2.05 × 10⁻², and 0.687; (3_H) 0.143, 1.05 × 10⁻², and 0.882; (1_Pt) 17.3, 7.04 × 10⁻³, and 0.980; (2_Pt) 10.2, 1.43 × 10⁻², and 0.935; (3_Pt) 16.3, 8.35 × 10⁻³, and 0.954. The response time for the change of the atmospheric gas from argon to oxygen was (1_H) 9.4 s, (2_H) 12.5 s, (3_H) 9.6 s, (1_Pt) 5.0 s, (2_Pt) 8.9 s, and (3_Pt) 4.6 s, indicating the shortening effect of platinum. The reverse effect of platinum was observed in the change from oxygen to argon: (1_H) 15.5 s, (2_H) 17.0 s, (3_H) 20.8 s, (1_Pt) 667.4 s, (2_Pt) 590.1 s, and (3_Pt) 580.4 s, indicating the specific interaction of oxygen to the platinum(II) center.