Journal of Fluorescence ( IF 2.6 ) Pub Date : 2021-05-06 , DOI: 10.1007/s10895-021-02736-x Muhammad Mubeen 1 , Muhammad Adnan Khalid 1 , Maria Mukhtar 1 , Saba Shahrum 1 , Shanila Zahra 1 , Saima Shabbir 2 , Azhar Iqbal 1
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Employing natural or artificial sunscreens is essential to protect the skin from ultraviolet radiations that cause premature aging and develop melanoma and other forms of skin cancer. The 2-Phenylbenzimidazole-5-sulfonic acid, commonly known as ensulizole is a water-soluble artificial sunscreen that absorb UV-B (280 nm − 315 nm) radiations and protects the skin against the harmful effects of these radiations. We have measured steady-state photoluminescence (SSPL) spectra and photoluminescence (PL) kinetics of this compound in various conditions. Steady-state absorption indicates a strong absorption feature at 303 nm and a weak one at 316 nm that have been identified as π → π* and n → π* transitions, respectively. The spectra of PL induced by these absorptions indicate that the PL of ensulizole is less Stokes-shifted in polar solvents and more Stokes-shifted in non-polar solvents. The average PL lifetime of ensulizole is longer in non-polar solvents than in polar solvents and it exhibits the shortest PL lifetime in aqueous medium that maximize its transition efficiency in water. This suggests in non-polar solvents intersystem crossing is the dominant mode of relaxation of the excited ππ* state. Furthermore, an increase of pH of ensulizole solution decreases the PL intensity and the lifetime. Stern-Volmer equation is employed to evaluate bimolecular quenching rate constant kq. The evaluation result suggests the diffusional dynamic mode of PL quenching is operative.
Graphical Abstract
中文翻译：
阐明 Ensulizole 中的光致发光猝灭：一种人造水溶性防晒霜
使用天然或人造防晒霜对于保护皮肤免受紫外线辐射至关重要，紫外线辐射会导致过早衰老并发展为黑色素瘤和其他形式的皮肤癌。 2-苯基苯并咪唑-5-磺酸，通常称为 ensuizole，是一种水溶性人造防晒霜，可吸收 UV-B（280 nm – 315 nm）辐射并保护皮肤免受这些辐射的有害影响。我们测量了该化合物在各种条件下的稳态光致发光（SSPL）光谱和光致发光（PL）动力学。稳态吸收表明在 303 nm 处有强吸收特征，在 316 nm 处有弱吸收特征，分别被识别为 π → π* 和 n → π* 跃迁。由这些吸收引起的PL光谱表明，恩苏唑的PL在极性溶剂中斯托克斯位移较小，而在非极性溶剂中斯托克斯位移较大。恩苏利唑在非极性溶剂中的平均 PL 寿命比在极性溶剂中更长，并且在水性介质中表现出最短的 PL 寿命，从而最大限度地提高了其在水中的转换效率。这表明在非极性溶剂中，系间窜越是激发 ππ* 态弛豫的主要模式。此外，恩苏利唑溶液 pH 值的增加会降低 PL 强度和寿命。采用Stern-Volmer方程计算双分子猝灭速率常数k q 。评估结果表明PL猝灭的扩散动态模式是有效的。
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