如动脉粥样硬化、高血压、糖尿病、阿尔茨海默病和细胞恶性肿瘤等许多生物功能紊乱和疾病与胞内黏度密切相关。生物医学界迫切需要一种安全有效的胞内黏度检测方法。最近，研发了一种新型的近红外荧光探针NI-VIS，其中包含一种扭转分子内电荷转移机制。通过实验证明该探针能够可视化肝硬化组织中的黏度变化并在体内绘制微黏度。本文详细研究了量子力学方法下探针NI-VIS的扭转分子内电荷转移机制和荧光特性。探针不同构象之间的低能障表明在低黏度环境中，探针分子中的芳基团旋转导致了扭转分子内电荷转移的发生。对不同探针构象的电子结构分析揭示了探针在光激发下的电子转移过程。这些理论结果能够深入了解原理，并构建高效的荧光探针以监测生物样品中的黏度。

So many biological functional disorders and diseases, such as atherosclerosis, hypertension, diabetes, Alzheimer's disease, as well as cell malignancy are closely related with the intracellular viscosity. A safe and effective intracellular viscosity detecting method is desired by the biomedical community. Recently, a novel near-infrared fluorescent probe NI-VIS with a twisting intramolecular charge transfer mechanism was developed. The capability of this probe to visualize the viscosity variation in cirrhotic liver tissues and map the micro viscosity in vivo were testified using an experiment. In this work, the twisting intramolecular charge transfer mechanism and fluorescent properties of the probe NI-VIS were studied in detail under quantum mechanical method. The low energy barrier among the different conformations of the probe indicated the occurrence of twisting intramolecular charge transfer due to the rotation of the aryl group in the probe molecule while within the low viscosity environment. The electronic structure analysis on different probe conformations revealed the electron transfer process of the probe under optical excitation. All these theoretical results could provide insights into understand in greater depth the principles and build highly effective fluorescent probe to monitor the viscosity in biological samples.