Design, Synthesis And Application Of The Near-Infrared Fluorescent Sensor For Cu²⁺

Recent years, as the development of standard of living and the further cognition to food safety, toxic heavy metal pollution has always been a serious global problem. Therefore, the detection of heavy metal ions in the environment has become a research point. Among various detection techniques, the fluorescence method, due to their high sensitivity, simplicity and real-time monitoring with fast response time, has aroused widespread interest in biological processes. However, these sensors that applied in food detection have been rare. Besides, compared to UV or visible dyes, the near-infrared fluorophores can reduce or avoid the interferences of background absorption, fluorescence, and light scattering. There is also less autofluorescence in the near-infrared region (650-900nm). This project aimed to provide more support for detecting heavy ions by fluorescence technology.In this paper, two novel near-infrared fluorescent and colorimetric Cu2+chemosensors which comprised two tricarbocyaine dyes with a ether-rich receptor have been designed and exploited for recognizing Cu2+with high sensitivity and selectivity. The two derivatives chemosensors from the parent cyanine dyes were obtained by nucleophilic substitution reaction in which the primary amines were employed as the nucleophilic reagent. We have characterized the structure of the two sensors by different methods.We have applied AC-1in the detection of Cu2+, and we can get the obvious visualization change of color (from blue to colorless) and the ratio fluorescent signal through the reaction between the chemosensor and Cu2+. Upon the addition of Cu2+, the AC-1solution displayed an over40-fold of fluorescence quenching monitored by using a fluorescence spectrometer. Under the optimum experimental conditions, the linear relationship between the fluorescence intensity and Cu2+amount conformed to the formula of Stern-Volmer. Moreover, AC-1featured high binding affinity with a low limit of detection of9.3x10-8mol L-1and excellent specificity that enabled AC-1eliminate the interference of food-relevant cations, especially for food-relevant cations of Ca2+, Zn2+, Fe2+and some typical heavy metal ions of Hg2+, Pb2+, Cd2+. The recovery test would prove that AC-1was a valuable and practical method for Cu2+detection in food samples with satisfied recoveries. The comparison between AC-1with ICP-MS with good consistence would further explain the feasibility of AC-1.