Ratiometric fluorescent sensing of copper (II) by a new covalent organic framework-based platform.

Although copper is essential for various functions in the human body, excessive intake can damage the nervous and immune systems. In this study, a new fluorescent covalent organic framework probe (DP-TFPB COF) was first reported. Relying on the rational design, the synthesized DP-TFPB COF demonstrates a distinctive fluorescence enhancement effect upon different solvent induction, achieving a quantum yield of up to 20.5 %. Then, a covalent organic framework-based ratiometric fluorescent system was developed, incorporating blue-emitting carbon dots to leverage the fluorescence energy transfer effect. Blue-emitting carbon dots served as the reference signal, while the DP-TFPB COF acted as the response unit, enabling successful quantitative detection of Cu. The mechanism study demonstrated that fluorescence quenching occurs through an electron transfer process, wherein the covalent organic framework serves as the electron donor and Cu functions as the electron acceptor. The developed method demonstrated excellent linearity for Cu within the concentration range of 0.5 to 200 μM, accompanied by a detection limit of 0.38 μM. The robust recognition capabilities exhibited significant effectiveness in the Cu analysis within herbal plants. The results correspond closely with those obtained using inductively coupled plasma mass spectrometry, thereby emphasizing its potential applicability in real samples with complex matrix.