Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Methods Appl Fluoresc. 2022 Jun 23;10(3). doi: 10.1088/2050-6120/ac784d.
3-Aminoquinoline (3AQ) has been used as a fluorescent probe for preferential solvation in hexane-ethanol solvent mixtures. Results of the present experiment have been put into context by comparison with prior observations with 5-aminoquinoline (5AQ) as the probe. 3AQ exhibits a relatively small change of dipole moment (Δ= 2.2 D) upon photoexcitation, compared to 5AQ (Δ= 6.1D), which might appear to be a hindrance in the way of its use as a solvation probe. Indeed, the values of parameters like spectral shifts are smaller for the present experiment with 3AQ. At the smallest concentration of alcohol used, its local mole fraction around the probe is significantly lower than in the previous experiments with 5AQ. However, these apparent disadvantages are outweighed by the significant increase in fluorescence intensity and lifetime observed with increasing concentration of ethanol in the solvent mixture, as opposed to the drastic fluorescence quenching that occurs for 5AQ. This is a marked advantage in the use of 3AQ in studies like the present one. The local mole fraction of ethanol and preferential solvation index experienced by 3AQ are in line with those reported for 5AQ. The disadvantage of the smaller magnitude of Δpersists in the time resolved fluorescence experiments, for solvent mixtures with very low ethanol content. Negligible wavelength dependence of fluorescence transients of 3AQ is observed for= 0.002,. However, this effect is outweighed at higher alcohol concentrations, for which nanosecond dynamics of preferential solvation is observed.
3-氨基喹啉（3AQ）已被用作正己烷-乙醇溶剂混合物中优先溶剂化的荧光探针。通过与 5-氨基喹啉（5AQ）作为探针的先前观察结果进行比较，对本实验的结果进行了阐述。与 5AQ（Δ=6.1D）相比，3AQ 光激发时的偶极矩变化相对较小（Δ=2.2D），这似乎对其作为溶剂化探针的使用造成了阻碍。事实上，与本实验中使用 3AQ 相比，目前实验中参数如光谱位移的值较小。在所使用的最小酒精浓度下，探针周围的局部摩尔分数明显低于以前使用 5AQ 的实验。然而，与 5AQ 发生的剧烈荧光猝灭相反，随着溶剂混合物中乙醇浓度的增加，观察到荧光强度和寿命显著增加，这弥补了这些明显的缺点。这是在本研究等研究中使用 3AQ 的一个显著优势。3AQ 经历的乙醇局部摩尔分数和优先溶剂化指数与报告的 5AQ 相符。在乙醇含量非常低的溶剂混合物中，Δ 值较小的劣势在时间分辨荧光实验中仍然存在。对于=0.002，观察到 3AQ 的荧光瞬变的可忽略的波长依赖性。然而，在更高的酒精浓度下，优先溶剂化的纳秒动力学被观察到，这超过了这种效应。
