Texaphyrin sensitized near-IR-to-visible photon upconversion
Texaphyrin sensitized near-IR-to-visible photon upconversion
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DOI：
10.1039/c4pp00037d
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发表时间：
2014-01-01
影响因子：
3.1
通讯作者：
Castellano, Felix N.
中科院分区：
文献类型：
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作者：
Deng, Fan;Sun, Wenfang;Castellano, Felix N.
在真空脱气的二氯甲烷中，Cd（II）texaphyrin（TXP）的近红外吸收与红荧烯三重态受体/零化子偶联，通过敏化三重态-三重态湮灭将近红外（670-800 nm）入射光子上转换为黄色荧光。利用瞬态吸收光谱对红荧烯对TXP的动态能量转移猝灭进行了Stern-Volmer分析，结果表明，三重态-三重态能量转移过程的Stern-Volmer猝灭常数和双分子猝灭常数分别为21 000 M-1和5.7 × 10（8）M-1 s（-1）。相对于在750 nm处的入射激发功率密度的上转换的发射强度被示出为在二次和线性之间变化，示出了在连续波照明下的光产生光化学的预期动力学极限。此外，随着TXP敏化剂浓度的增加，特征二次到线性交叉点向较低的入射光子功率密度移动。这与敏化剂中较强的光子捕获导致在较温和的激发条件下促进上转换的实验条件的概念一致。在连续波激发条件下，相对于[Os（phen）（3）]（PF 6）（2），在稀释条件下测定的TXP敏化的红荧烯上转换荧光的最大量子产率为1.54 +/- 0.04%。当入射光功率依赖性达到二次到线性交叉点时，实现了这种饱和量子效率，并且在组合物显示对入射光功率密度的线性响应的区域上是恒定的。在较高敏化剂浓度下的脉冲激光实验中，三重态-三重态湮灭量子产率被确定为在约13%处饱和，对应于类似于10%的上转换产率，这表明二氯甲烷溶剂降低了红荧烯受体的T-2态，或者以某种方式减弱了激发的红荧烯三重态之间的湮灭反应。
Near-IR (NIR) absorption from a Cd(II) texaphyrin (TXP) has been successfully coupled with rubrene triplet acceptors/annihilators in vacuum degassed dichloromethane to upconvert NIR (670-800 nm) incident photons into yellow fluorescence through sensitized triplet-triplet annihilation. Stern-Volmer analysis of dynamic energy transfer quenching of TXP by rubrene using transient absorption spectroscopy revealed Stern-Volmer and bimolecular quenching constants of 21 000 M-1 and 5.7 x 10(8) M-1 s(-1) respectively, for the triplet-triplet energy transfer process. The upconverted emission intensity with respect to the incident excitation power density at 750 nm was shown to vary between quadratic and linear, illustrating the expected kinetic limits for the light producing photochemistry under continuous wave illumination. Furthermore, with increasing TXP sensitizer concentration, the characteristic quadratic-to-linear crossover point shifted to lower incident photon power density. This is consistent with the notion that stronger photon capture in the sensitizer leads to experimental conditions promoting upconversion under milder excitation conditions. The maximum quantum yield of the TXP-sensitized rubrene upconverted fluorescence was 1.54 +/- 0.04% under dilute conditions determined relative to [Os(phen)(3)](PF6)(2) under continuous wave excitation conditions. This saturating quantum efficiency was realized when the incident light power dependence reached the quadratic-to-linear crossover point and was constant over the region where the composition displayed linear response to incident light power density. In pulsed laser experiments at higher sensitizer concentrations, the triplet-triplet annihilation quantum yield was determined to saturate at approximately 13%, corresponding to an upconversion yield of similar to 10%, suggesting that the dichloromethane solvent either lowers the T-2 state of the rubrene acceptor or is somehow attenuating the annihilation reaction between excited rubrene triplets.