Cu-THQ metal-organic frameworks: A kind of new inner reference for the reliable detection of dopamine base on ratiometric electrochemical sensing

Ratiometric electrochemical sensing provides a new perspective for the accurate and reliable detection of different analytes since inner reference signal can effectively eliminate the internal and external interferences. There is still a challenge to explore new inner references for the development of ratiometric electrochemical sensing. Herein, a kind of redox-active metal-organic frameworks (Cu-THQ MOFs) was synthesized and characterized by scanning electron microscope, transmission electron microscope, X-ray powder diffractometer, and X-ray photoelectron spectroscopy techniques. Cu-THQ MOFs were composited with carboxylic group functionalized multi-walled carbon nantubes (MWCNTs-COOH) to construct a sensitive electrochemical sensor. The modified Cu-THQ MOFs not only showed good catalytic active to dopamine (DA), but also displayed the constant peak current with the increase of concentration of DA. And a separated oxidation peak potential of about 270 mV between DA and Cu-THQ MOFs can be observed. Accordingly, a current ratio (iDA/iMOFs) was employed as readout signal for DA detection with a linear range and limit of detection of 3.0 × 10−7– 4.0 × 10−5 mol/L and 2.6 × 10−8 mol/L, respectively. Compared with single signal of iDA, ratiometric strategy exhibited high accuracy and reliability for DA determination. The present ratiometric sensing strategy using MOFs as the inner reference may provide a new choice for future development of electrochemical sensors for other analytes reliable determination.