Chromogenic Chemosensors Based on Phenolic Imines for the Detection of Alkylamines and Lidocaine in Water and in the Vapor Phase

Three imines comprised of 5-nitrothiophen-2-yl as electron-accepting and phenols as electron-donating groups were synthesized and used as chromogenic chemosensors to detect alkylamines. The compounds are colorless in water, but their deprotonation by the alkylamines generates the corresponding colored phenolates, which can be used to detect those analytes. The addition of cetyltrimethylammonium bromide (CTAB) causes bathochromic shift of the perichromic band of the phenolates, indicating that the compounds are transferred into the micelles. In addition, CTAB lowers the pKa of phenols and increases the stability of the phenolates, improving their performance as chemosensors. Applications were prospected with the chromogenic chemosensors adsorbed on strip papers to detect alkylamines in water and in the vapor phase. The compounds were also used in solution for the quantification of lidocaine in water. Thus, the versatility of the compounds studied allows to think about applications in industrial, environmental, and pharmaceutical areas.

本研究合成了三种以5-硝基噻吩-2-基为吸电子基团、苯酚为给电子基团的亚胺类化合物，并将其作为显色化学传感器（chromogenic chemosensors）用于烷基胺的检测。该类化合物在水溶液中呈无色状态，经烷基胺去质子化后可生成相应的有色酚盐，借此实现对目标分析物的检测。加入十六烷基三甲基溴化铵（cetyltrimethylammonium bromide, CTAB）后，酚盐的显色吸收带会发生红移，表明化合物已转移至胶束体系中。此外，CTAB可降低苯酚类底物的酸度系数（pKa），并提升酚盐的稳定性，从而优化其作为化学传感器的传感性能。研究还探索了吸附于试纸条的该类显色化学传感器的应用场景，可用于检测水溶液及气相中的烷基胺。上述化合物还可应用于溶液体系，实现水溶液中利多卡因的定量检测。综上，本研究所涉化合物具备优异的多功能性，有望在工业、环境与医药等领域实现相关应用。