Liu Ting, Huang Jianwei, Ding He, Zhan Chengsen, Wang Shouyu
College of Mechanical Engineering and Automation, Huaqiao University, Xiamen, Fujian 361021, China.
College of Mechanical Engineering and Automation, Huaqiao University, Xiamen, Fujian 361021, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Jul 5;275:121166. doi: 10.1016/j.saa.2022.121166. Epub 2022 Mar 16.
As one of the most commonly used organic fluorescent dyes, recently rhodamines have been successfully employed in temperature sensing. However, few works have been reported on their temperature-sensitive properties, which inevitably limiting their further applications. In order to solve such problem, we investigated temperature-sensitive properties of rhodamine 110, 123, 19, 6G, B and 3B focusing on their fluorescence emission spectra; and analyzed them in the molecular structure perspective. It is demonstrated that the fluorescence emission intensities of all studied rhodamines decreased with higher temperature, which inevitably enhances the probability of collisions among molecules, thus definitely leads to energy loss in fluorescence emission. While these rhodamines still have various temperature sensitivities mainly due to the substitutes: the substitute on the benzene carboxylate has little effect; the amino substituents of the three-ring xanthene enhance the temperature sensitivity due to their rotation weakening the rigidity of the three-ring xanthene; and the methyl substituents on the three-ring xanthene reduce the temperature sensitivity by enhancing the rigidity and stability of the three-ring xanthene as well as hindering the rotation of ethylamino. These findings can also be extended to other organic fluorescent dyes proved by coumarins comparable to rhodamines. The results provided by this work can be useful reference and guidance to further develop organic fluorescent dyes especially for temperature sensing.
作为最常用的有机荧光染料之一，近年来罗丹明已成功应用于温度传感。然而，关于它们的温度敏感特性的报道却很少，这不可避免地限制了它们的进一步应用。为了解决这个问题，我们研究了罗丹明110、123、19、6G、B和3B的温度敏感特性，重点关注它们的荧光发射光谱，并从分子结构角度对其进行了分析。结果表明，所有研究的罗丹明的荧光发射强度都随着温度的升高而降低，这不可避免地增加了分子间碰撞的概率，从而肯定导致荧光发射中的能量损失。而这些罗丹明仍具有各种温度敏感性，主要是由于取代基的影响：苯甲酸盐上的取代基影响较小；三环呫吨的氨基取代基由于其旋转削弱了三环呫吨的刚性而增强了温度敏感性；三环呫吨上的甲基取代基通过增强三环呫吨的刚性和稳定性以及阻碍乙氨基的旋转而降低了温度敏感性。与罗丹明类似的香豆素证明，这些发现也可以扩展到其他有机荧光染料。这项工作提供的结果可为进一步开发有机荧光染料尤其是用于温度传感的染料提供有用的参考和指导。
