Bifunctional MOFs-based Ratiometric Electrochemical Sensor for Multiplex Heavy Metal Ions.

In this study, a ratiometric electrochemical sensor based on metal-organic frameworks (MOFs) was developed for sensing of multiplex metal ions. The bifunctional MOFs were prepared in a way to integrate two signal tags and detection probe. In presence of target metal ions, the target metal ions can replace the framework metal ions center in original MOFs through ion exchange reaction, leading to ratiometric electrochemical signals under different applied potentials. One consisted of Cu2+ signal generated from electroactive MOFs selected as internal reference signals. The other consisted of signal induced by other target metal ions. Using Imetal ions/ICu2+ signal as output, the prepared ratiometric probe was able to eliminate disturbance caused by the sensing environment. Moreover, the large surface area and abundant active sites in MOFs produced multiplex ratiometric electrochemical sensor with improved characteristics in terms of reproducibility, stability, and sensitivity. The sensor was also simple without sophisticated instrumentations, amplification processes or acid dissolution/preconcentration procedure, hence promising for practical applications.