It is shown that the weak IR absorption bands corresponding to the forbidden triplet-singlet transitions in oxygen molecules can be reliably studied in air-saturated solvents under ambient conditions using measurements of the photooxygenation rates of singlet oxygen traps (1,3-diphenylisobenzofuran or uric acid) upon direct excitation of oxygen molecules by IR diode lasers. The best results were obtained from comparison of the oxygenation rates upon direct and photosensitized singlet oxygen excitation. In the present paper, this method was applied to estimation of the absorbance (A(ox)) and molar absorption coefficients (ε(ox)) corresponding to the oxygen absorption bands at 765 and 1273 nm in carbon tetrachloride, acetone, alcohols and water. In carbon tetrachloride, the band at 1073 nm was also investigated. Correlation of the obtained data with the luminescence spectra and radiative rate constants of singlet oxygen, contribution of oxygen dimols and biological significance of the studied effects are discussed.

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New heterogeneous photosensitizers were synthesized, in which phthalocyanines of zinc and aluminum, tetrasubstituted at non-peripheral positions with modified thiophenyl groups, were grafted to aminopropyl silica gel. The absorption and fluorescence spectra, and the quantum yields of fluorescence and photosensitized singlet oxygen generation were estimated for aqueous suspensions of these sensitizers. It is shown that upon photoexcitation, silica gel-bound phthalocyanines produce singlet oxygen and display photobactericidal activity against bacteria E. coli.