Abstract:

The development of highly selective and sensitive sensors for Cu²⁺ ions is of paramount significance in the realms of chemistry, biology and environmental science. In this paper, a colorimetric and ratiometric fluorescent sensor for Cu²⁺ based on intra molecular charge transfer (ICT) mechanism was developed using naphthalimide-phenanthroimidazole (NP), and well characterized by ¹H NMR, ¹³C NMR and HR-MS. NP showed the fluorescence color change from "bright yellow" to "blue" as well as naked-eye color alter from "bright yellow" to "colorless" after the Cu²⁺ adding. UV-vis and fluorescence spectroscopy results revealed that the sensor NP exhibited remarkable colorimetric and ratiometric fluorescence behavior towards Cu²⁺ with high selectivity and sensitivity, and the response time was short. Based on emission titration data, the binding constant between the NP and Cu²⁺ was 3.04×10⁴L/mol and the limit of detection (LOD) was 5.35×10^-8mol/L (53.5nmol/L). The response mechanism was revealed by Job plot analysis, ¹H NMR spectroscopy and mass spectrometry data. The results showed that the coordination of the sensor's N atoms of phenanthroimidazole and imide with Cu²⁺ ions, and the binding stoichiometry between NP and Cu²⁺ was 1∶1. DFT calculation results showed that the lower bandgap of the HOMO-LUMO after coordination indicated that the coordination between PZ and Cu²⁺ was stable. NP was successfully applied for the quantitative recognition of Cu²⁺ in real water samples. In addition, the sensor NP was loaded on filter paper to make test strips and combined with a smartphone to achieve rapid visual quantitative detection of Cu²⁺.

Key words: copper(Ⅱ) ion, naphthalimide-phenanthroimidazole, ratiometric fluorescent probe, intra molecular charge transfer (ICT), colorimetric

摘要：

开发高选择性、高灵敏度的Cu²⁺传感器在化学、生物和环境等领域具有重要意义。本研究利用ICT机制设计并合成了一种基于萘酰亚胺-菲并咪唑的新型Cu²⁺比色和荧光比率探针NP，并通过¹H NMR、¹³C NMR和HR-MS进行了表征。在Cu²⁺加入后，探针NP由“亮黄色”荧光变为“蓝色”荧光，肉眼可观察到颜色由“亮黄色”变为“无色”。UV-vis和荧光光谱研究表明，探针NP对Cu²⁺具有较高的选择性和灵敏度，并且响应时间短。根据荧光滴定实验，计算得到探针NP与Cu²⁺的结合常数为3.04×10⁴L/mol，NP对Cu²⁺的检出限为5.35×10^-8mol/L（53.5nmol/L）。Job曲线、¹H NMR和质谱数据分析显示，探针NP是通过菲并咪唑N原子、亚胺上的N原子与Cu²⁺结合的，二者结合的化学计量比为1∶1，DFT计算显示NP-Cu²⁺的HOMO-LUMO能带能隙差低于NP的能隙差，表明NP与Cu²⁺的配位是有利的。NP已成功应用于实际水样中Cu²⁺的定量识别；此外，制备了基于NP的试纸条，与智能手机结合，可实现Cu²⁺的快速视觉半定量检测。

关键词: 铜离子, 萘酰亚胺-菲并咪唑, 荧光比率探针, 分子内电荷转移, 比色识别