Production Rate and Reactivity of Singlet Oxygen 1O2(1Δg) Directly Photoactivated at 1270 nm in Lipid Nanocapsules Dispersed in Water

Abstract

Singlet oxygen is produced through the O2 [3∑g–] → O2 [1Δg] transition of molecular oxygen upon direct 1270 nm laser irradiation in water. The non water-soluble 1,3-diphenylisobenzofuran (DPIBF) is encapsulated in lipid nanocapsules (LNCs) in D2O and used to monitor the formation of singlet oxygen in these microheterogeneous systems. A two-pseudophase kinetic model for 1O2 distribution is applied to LNCs dispersions in D2O. From a simple analytical expression of the trap disappearance rate, both the σ1270 absorption cross section of the O2 [3∑g–] → O2 [1Δg] transition and the reactivity of singlet oxygen toward DPIBF can be evaluated simultaneously and independently in LNCs dispersions in D2O, and σ1270 can be extrapolated to pure deuterated water. The water-soluble chemical trap tetrapotassium rubrene-2,3,8,9-tetracarboxylate (RTC) is used to monitor the formation of singlet oxygen in water and D2O, and σ1270 is also determined in these solvents. Absorption spectrum for the transition O2 [3∑g–] → O2 [1Δg] of molecular oxygen is measured in D2O.