Fluorescent molecular rotors (MRs) are compounds whose emission is modulated by segmental mobility; photoexcitation generates a locally excited (LE), planar state that can relax either by radiative decay (emission of a photon) or by formation of a twisted intramolecular charge transfer (TICT) state that can relax nonradiatively due to internal rotation. If the local environment around the probe allows for rapid internal rotation in the excited state, fast non-radiative decay can either effectively quench the fluorescence or generate a second, red-shifted emission band. Conversely, any environmental restriction to twisting in the excited state due to free volume, crowding or viscosity, slows rotational relaxation and promotes fluorescence emission from the LE state. The environmental sensitivity of MRs has been exploited extensively in biological applications to sense microviscosity in biofluids, the stability and physical state of biomembranes, and conformational changes in macromolecules. The application of MRs in food research, however, has been only marginally explored. In this review, we summarize the main characteristics of fluorescent MRs, their current applications in biological research and their current and potential applications as sensors of physical properties in food science and engineering.

中文翻译：

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发光分子转子在食品科学与工程中的潜在应用

荧光分子转子（MRs）是化合物，其发射受分段迁移率调节；光激发产生局部激发（LE）的平面状态，该状态可以通过辐射衰减（光子的发射）或通过形成扭曲的分子内电荷转移（TICT）状态而松弛，该状态由于内部旋转而可以无辐射地松弛。如果探针周围的局部环境允许在激发状态下快速内部旋转，则快速的非辐射衰减可以有效地猝灭荧光或生成第二个红移的发射带。相反，由于自由体积，拥挤或粘性导致的在激发态下扭曲的任何环境限制都会减慢旋转弛豫并促进LE态的荧光发射。在生物应用中已广泛开发了MR的环境敏感性，以感测生物流体中的微粘度，生物膜的稳定性和物理状态以及大分子的构象变化。但是，仅对MRs在食品研究中的应用进行了探索。在这篇综述中，我们总结了荧光MR的主要特征，它们在生物学研究中的当前应用以及它们在食品科学和工程中作为物理性质传感器的当前和潜在应用。