Absolute Phosphorescence Quantum Yields of Singlet Molecular Oxygen in Solution Determined Using an Integrating Sphere Instrument

Abstract

In this paper, we present an integrating sphere instrument for absolute luminescence quantum yield measurements from the visible to near-infrared (NIR) spectral region (λ = 350-1650 nm). The integrating sphere is equipped with a Xe light source and two spectrally corrected multichannel analyzers using a back-thinned charge-coupled device (CCD) and InGaAs detector, one for measurements in the visible to NIR wavelength region (λ = 350-1100 nm) and the other for the NIR wavelength region (λ = 900-1650 nm). The combination of the two optical multichannel analyzers allows measurement of the absolute quantum yield of NIR emissions with good sensitivity. Using this new instrument and platinum(II) meso-tetra(pentafluorophenyl)porphine (PtTFPP) as a sensitizer, we performed the first absolute measurements of quantum yield (Φ(p)(¹Δ)) of the a¹Δ(g) (v′ = 0) → X³Σ(g)⁻ (v″ = 0) emission at 1270 nm from molecular oxygen in different solvents. The quantum yields Φ(p)(¹Δ) in CCl₄ and CS₂ under infinite dilution of sensitizer were determined to be 2.2 × 10⁻² and 6.4 × 10⁻², respectively. Using the Φ(p)(¹Δ) value in CCl₄, the quantum yields in other solvents were determined based on the relative method. From the phosphorescence quantum yields and the lifetimes of O₂(a¹Δ(g)) taken under identical experimental conditions, we evaluated the radiative and nonradiative rate constants of O₂(a¹Δ(g)), which are key parameters to understand the photophysical properties of singlet oxygen in solution. The quantum yields and radiative and nonradiative rate constants obtained in the present study were compared with the literature values determined based on the relative method.

Effect of Solvent on the O2(a1Δg) → O2(b1Σg+) Absorption Coefficient

“…To our knowledge, there have been only two attempts to quantify absolute values of O 2 (a 1 Δ g ) phosphorescence quantum yields in the pertinent solvents to yield data that can then be used to obtain an absolute value of k aX . 41,44 Although different approaches were used in these two studies, the results obtained are equivalent within the margin of error for such a difficult experiment. For our present work, we opted to use k aX = 1.5 ± 0.5 s −1 obtained by Schmidt for experiments performed in benzene.…”

Anthracene-based fluorescent nanoprobes for singlet oxygen detection in biological media

“…This drawback is specially critical in biological media, where the 1 O 2 lifetime (τ ∆ ) is very short due to the presence of 1 O 2 quenchers. [1,11,15] An alternative to circumvent these shortcomings is to trap 1 O 2 with suitable chemical acceptors where the precursor and/or oxidation products can be conveniently monitored through absorption, [16] fluorescence, [17,18] or ESR. [19] Polycyclic aromatic hydrocarbons such as anthracenes or rubrene are commonly used as 1 O 2 traps.…”

Synthesis of Iridium(III) Complex Bearing 1-Thio-β-D-glucose Tetraacetate Moieties and its Photogeneration of Singlet Oxygen

“…To observe the remarkable emission of 1 O 2 at 1,270 nm, C 6 D 6 is the preferred solvent [14,15]. However, the reported sugar-containing Ir(III) complex (1) is hardly soluble in benzene; thus, we synthesized a novel Ir(III) complex coordinated with bipyridyl ligands bearing acetyl-protected glucose by following a modified version of our reported method (Scheme 4) [9][10][11].…”