Lifetime of Singlet Oxygen and Quenching by NaN₃ in Mixed Solvents

Abstract

<jats:p>Singlet oxygen was generated by the photosensitization of erythrosine. The lifetime of singlet oxygen and the quenching rate constant for singlet oxygen by NaN<jats:sub>3</jats:sub> were measured by a thermal lensing method in MeOH-H<jats:sub>2</jats:sub>O mixed solvents. The reciprocal of the lifetime increased linearly with the increase of the H<jats:sub>2</jats:sub>O mole fraction. Semi-log plot of the quenching constant against the reciprocal of the solvent polarity exhibited a linear relation. The quenching of the singlet oxygen by NaN<jats:sub>3</jats:sub> may proceed through a partial charge-transfer intermediate. The activation energy for the quenching reaction of N<jats:sub>3</jats:sub><jats:sup>-</jats:sup> + <jats:sup>1</jats:sup>O<jats:sub>2</jats:sub> →[N<jats:sub>3</jats:sub>·<jats:sup>1</jats:sup>O<jats:sub>2</jats:sub><jats:sup>-</jats:sup>] increased with the increase of the solvent polarity. The lifetime was also measured in MeOH-ethyleneglycol mixed solvents, and its relation with viscosity was obtained</jats:p>

Quenching of Singlet Molecular Oxygen (1O2) by Azide Anion in Solvent Mixtures¶

“…Although higher temperatures decrease to some extent the dielectric constant of water, this should not affect the ionic dissociation of sodium azide. The activation energy for the 1 O 2 quenching by azide was reported to be 7.2 kJ mol Ϫ1 in methanol (26). The value measured by us in D 2 O is 11.3 kJ mol Ϫ1 (Fig.…”

Investigating the reactive oxygen species production of Rose Bengal and Merocyanine 540-loaded radioluminescent nanoparticles

“…To determine if singlet oxygen was being produced, the experiments were repeated with the same concentrations of PSloaded nanoparticles, and DPBF, but with 20 mM NaN 3 included in the solution. Sodium azide is a well-known singlet oxygen scavenger; 5,35 if singlet oxygen is produced by the nanoparticles, the rate of DPBF quenching should decrease and subsequently the absorbance should decrease to a lesser extent. No signicant change in the rate or percentage of DPBF absorbance decrease was observed with and without NaN 3 for both PS-RLNP systems, as shown in Fig.…”

Synergistic interactions of cadmium-free quantum dots embedded in a photosensitised polymer surface: efficient killing of multidrug-resistant strains at low ambient light levels

“…1 O 2 photo-generated via FRET can be quenched by both Cy and DCM and in a mixed system of these 2 solvents, the decay rate constant of 1 O 2 ( k d ) may be expressed as follows: k d = x 1 k 1 + x 2 k 2 where x 1 and x 2 are the mole fractions of Cy and DCM in the systems respectively and k 1 and k 2 are the 1 O 2 decay rate constants from the reported 1 O 2 lifetimes in each solvent. 67 In 1 : 1 Cy/DCM, x 1 = x 2 = 0.5. The literature reported 1 O 2 lifetimes as 2.3 × 10 –5 s in Cy and 9.9 × 10 –5 s in DCM, yielding values of 4.3 × 10 4 s –1 and 1.0 × 10 4 s –1 for the 1 O 2 decay constant in Cy and DCM respectively.…”

“…where x 1 and x 2 are the mole fractions of Cy and DCM in the systems respectively and k 1 and k 2 are the 1 O 2 decay rate constants from the reported 1 O 2 lifetimes in each solvent. 67 (Fig. 4B).…”