Abstract The present study reports the use of ultraviolet-visible absorption, steady-state fluorescence, and time-resolved fluorescence to determine the water content in ethanol by using Rhodamine B as an optical probe. The experiments were performed by preparing water/ethanol blends with different percentages of water in the presence of the optical probe. The absorbance, fluorescence intensity, and fluorescence lifetime values were linearly dependent on the water content in the blends in the range between 0 and 10% (w/w). The results also revealed that the three techniques have a limit of detection for water ≤ 1.4 % (w/w). Besides, molecular dynamics simulations were carried out to evaluate the interaction of RhB with water and ethanol molecules when subjected to different water content in the blends. The simulations revealed that water molecules perform well-oriented dipole-dipole interactions (hydrogen bonding) with chromophores/fluorophores groups of Rhodamine B, affecting its absorption and emission characteristics, and altering the microenvironment density and viscosity. The present findings point out that common optical techniques can be used to develop a simple, rapid, portable, and precise approach to monitor water in ethanol as far as RhB be used as a probe.

中文翻译：

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使用罗丹明 B 作为有效的分子光学探针定量生物乙醇中的水

摘要 本研究报告了以罗丹明 B 作为光学探针，利用紫外-可见吸收、稳态荧光和时间分辨荧光测定乙醇中的水含量。通过在光学探针的存在下制备具有不同水百分比的水/乙醇混合物来进行实验。吸光度、荧光强度和荧光寿命值在 0 到 10% (w/w) 的范围内与混合物中的水含量呈线性关系。结果还表明，这三种技术对水的检测限≤ 1.4 % (w/w)。此外，进行了分子动力学模拟以评估当混合物中的水含量不同时，RhB 与水和乙醇分子的相互作用。模拟表明，水分子与罗丹明 B 的发色团/荧光团发生定向良好的偶极-偶极相互作用（氢键），影响其吸收和发射特性，并改变微环境密度和粘度。目前的研究结果指出，只要使用 RhB 作为探针，就可以使用常见的光学技术开发一种简单、快速、便携和精确的方法来监测乙醇中的水。