Journal of Luminescence 2014 Volume 149() pp:267-271
Publication Date(Web):May 2014
DOI:10.1016/j.jlumin.2014.01.025
•A systematic study on O2(a1Δ) luminescence properties from C60 solutions.•Evidences for the formation of photoinduced O2(a1Δ) quenchers.•The photoinduced O2(a1Δ) quencher is found to be C60O.•Kinetic analysis for the variation of O2(a1Δ) PL intensity with pump energy.A systematic investigation on singlet oxygen (O2(a1Δ)) photoluminescence (PL) from fullerene (C60) solutions by using a pulsed Nd: YAG laser at 532 nm was reported. The results show that the O2(a1Δ) PL intensity first increases linearly, then declines fast, and eventually tends to level off with the increase of pump energy, while decreases monotonically with increasing irradiation time. The latter can evidently be attributed to the formation of photoinduced O2(a1Δ) quenchers, which was directly confirmed by the remarkable decrease of O2(a1Δ) lifetime with increasing irradiation time. Also, we further demonstrated that the O2(a1Δ) quencher should be C60O via electrospray ionization-mass spectrometry (ESI-MS) and a kinetic analysis on the formation rate of the O2(a1Δ) quenchers in irradiated C60 solutions. On this basis, the above pump-energy dependence of O2(a1Δ) PL was also rationalized kinetically. With the increase of pump energy, the initial linear increase is exactly attributable to the linear increase of O2(a1Δ) concentration, while the following drop should result from the fast formation of photoinduced O2(a1Δ) quenchers and the eventual smooth variation is evidently related to the inverse saturated absorption effect of C60.
Chemical Physics Letters 2013 Volume 583() pp:14-17
Publication Date(Web):17 September 2013
DOI:10.1016/j.cplett.2013.07.064
Highlights•The deactivation rate constants (kΔ) of O2(a1Δ) by gaseous alcohols are measured.•An abnormal phenomenon of O2(a1Δ) deactivation is for the first time reported.•Gaseous kΔ values for deuterated alcohols are larger than their liquid-phase data.•The mechanism for this abnormal phenomenon is discussed.The deactivation rate constants (kΔ) of O2(a1Δ) by several gaseous alcohols were measured using a quasi-static method. The results indicate that the gaseous kΔ values for normal alcohols are smaller than their corresponding liquid-phase data, well consistent with Schmidt’s model. However, for deuterated alcohols, an abnormal phenomenon that their gaseous kΔ values are evidently larger than their corresponding liquid-phase data was first observed. It is likely related to the O–D bonds in their molecules which can form more stable liquid-phase clusters via intermolecular hydrogen bonds and exhibit different vibrational constants in gas and liquid phase.
The photoexcited aqueous fullerene (C60) suspension was shown to exhibit an asymmetric photoluminescence (PL) spectrum, which, different from the symmetric spectrum observed previously in C60 solutions or suspensions, still stems from the characteristic phosphorescence of singlet oxygen (O2(a1Δ)) owing to its dependence on oxygen concentration. In contrast to the microsecond-level lifetime of O2(a1Δ) in water solutions, that in our C60 suspensions was measured at room temperature to be relatively long, about 2–3 ms, which is ∼1000 times longer than the value reported by Bilski et al. The physical mechanism for the asymmetric O2(a1Δ) PL from C60 suspensions was studied in depth, indicating that it in fact originates from O2 molecules trapped in the C60 lattice within the suspended C60 aggregates (nC60). This mechanism, which can explain well our above results, was further validated by the nC60’s high-resolution transmission electron microscopy (HRTEM) images with lattice fringes and the experimental temperature dependence of O2(a1Δ) lifetimes in nC60 suspensions. Our findings suggest that the bulk-phase O2(a1Δ) in aqueous nC60 suspensions results from the diffusion of the O2(a1Δ) generated within the interior of nC60 aggregates.
Chemical Physics Letters 2011 Volume 504(4–6) pp:241-244
Publication Date(Web):10 March 2011
DOI:10.1016/j.cplett.2011.01.078
Abstract
A quasi-static method is developed for measuring the deactivation rate constants of O2(a1Δg) in gas phase by monitoring its IR radiation decay via a flow-stop technique. This method has taken into account the energy-pooling reaction of O2(a1Δ) and thus suits fairly high O2(a1Δ) concentration without identifying its absolute value, leading to simpler operation and higher signal/noise ratio. Utilizing this method, the O2(a1Δ) deactivation rate by D2O is for the first time measured to be 2.10 ± 0.18 × 10−18 cm3 s−1, while those for O2(), H2O, H2 and D2 are found to agree well with the data in literature.
The deactivation rate constants of O2(1Δg) by H2 and D2 are respectively measured to be 3.91 ± 0.12 × 10−18 cm3 s−1 and 1.1 ± 0.3 × 10−19 cm3 s−1, which agree well with the quantum mechanical calculation by Kustrev. Their deactivation mechanisms by H2 and D2 are analyzed according to the E–V energy transfer model developed by Schmidt, indicating that the main deactivation channel for H2 is and H2 (Δv = 2), while that for D2 is and D2 (Δv = 2), which entirely matches the calculation by Kustrev.
