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 a detection probe. In the presence of target metal ions,
the target metal ions can replace the framework metal-ion center in
the original MOFs through an ion-exchange reaction, leading to ratiometric
electrochemical signals under different applied potentials. One consisted
of the Cu2+ signal generated from electroactive MOFs selected
as internal reference signals. The other consisted of the signal induced
by other target metal ions. Using the I
metal ions/I
Cu2+
signal as the 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 a multiplex ratiometric electrochemical
sensor with improved characteristics in terms of reproducibility,
stability, and sensitivity. The sensor was also simple without sophisticated
instrumentation, amplification processes, or an acid dissolution/preconcentration
procedure, hence promising for practical applications.
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