National Institute for Research and Development of Isotopic and Molecular Technologies, Donat Street, No. 67-103, 400293 Cluj-Napoca, Romania.
Nanobiophotonics and Laser Microspectroscopy Center, Interdisciplinary Research Institute in Bio-Nano-Sciences, Babes-Bolyai University, 42 T. Laurian Str., 400271 Cluj-Napoca, Romania.
Int J Mol Sci. 2022 May 13;23(10):5483. doi: 10.3390/ijms23105483.
To understand the photochemical behaviour of the polydopamine polymer in detail, one would also need to know the behaviour of its building blocks. The electronic absorption, as well as the fluorescence emission and excitation spectra of the dopamine were experimentally and theoretically investigated considering time-resolved fluorescence spectroscopy and first-principles quantum theory methods. The shape of the experimental absorption spectra obtained for different dopamine species with standard, zwitterionic, protonated, and deprotonated geometries was interpreted by considering the advanced equation-of-motion coupled-cluster theory of DLPNO-STEOM. Dynamical properties such as fluorescence lifetimes or quantum yield were also experimentally investigated and compared with theoretically predicted transition rates based on Fermi's Golden Rule-like equation. The results show that the photochemical behaviour of dopamine is strongly dependent on the concentration of dopamine, whereas in the case of a high concentration, the zwitterionic form significantly affects the shape of the spectrum. On the other hand, the solvent pH is also a determining factor for the absorption, but especially for the fluorescence spectrum, where at lower pH (5.5), the protonated and, at higher pH (8.0), the deprotonated forms influence the shape of the spectra. Quantum yield measurements showed that, besides the radiative deactivation mechanism characterized by a relatively small value, non-radiative deactivation channels are very important in the relaxation process of the electronic excited states of different dopamine species.
为了详细了解聚多巴胺聚合物的光化学反应行为，还需要了解其构建块的行为。通过实验和理论研究考虑时间分辨荧光光谱和第一性原理量子理论方法，研究了多巴胺的电子吸收、荧光发射和激发光谱。通过考虑 DLPNO-STEOM 的先进运动方程耦合簇理论，解释了不同多巴胺物种（标准、两性离子、质子化和去质子化几何形状）获得的实验吸收光谱的形状。还通过实验研究了荧光寿命或量子产率等动力学特性，并根据费米黄金定则类似的方程与理论预测的跃迁速率进行了比较。结果表明，多巴胺的光化学行为强烈依赖于多巴胺的浓度，而在高浓度的情况下，两性离子形式显著影响光谱的形状。另一方面，溶剂 pH 值也是吸收的决定因素，但特别是对于荧光光谱，在较低的 pH 值（5.5）下，质子化形式，在较高的 pH 值（8.0）下，去质子化形式影响光谱的形状。量子产率测量表明，除了由相对较小的 值特征化的辐射去激活机制之外，非辐射去激活通道在不同多巴胺物种的电子激发态的弛豫过程中非常重要。
