Donut-like Cu-Zn-MOF/CuNPs composite for sensitive and selective electrochemical detection of silver ions

Donut-like Cu-Zn-MOF@CuNPs were synthesized via facile two-step approaches. • Cl − amplifies Cu signal via formation of highly electroactive CuCl. • Ag + inhibits the signal by competitive binding with Cl − to form AgCl. • The sensor detects Ag + with a low LOD of 1.4 nM and wide linear range. • It shows good selectivity, stability, and real water sample recovery. Silver ions (Ag + ) are highly toxic heavy metal pollutants. Conventional electrochemical methods for Ag + detection typically involve complex ionophore preparation, long preconcentration/stripping steps, or costly biorecognition agent. Here, we report a Cu-Zn-MOF supported CuNPs composite (Cu-Zn-MOF/CuNPs) for Ag + detection. The composite is prepared via a two-step room temperature mixing process. The nest-like Cu-Zn-MOF, composed of stacked two-dimensional nanosheets, provides a high specific surface area and accessible active sites for CuNPs deposition, which improves conductivity and generates a detectable redox signal. The presence of Cl − enhances the Cu redox signal due to the formation of electroactive CuCl. In the presence of Ag + , this signal enhancement is suppressed due to the competitive binding that forms AgCl precipitates. Leveraging this “amplification-inhibition” response, the Cu-Zn-MOF/CuNPs modified electrode allows for Ag + detection with two linear ranges (5 nM–100 nM and 100 nM–1100 nM), a detection limit of 1.4 nM, and recoveries ranging from 96.5% to 104.5% in spiked real water samples. The preparation procedure and detection protocol are relatively straightforward, and the sensing mechanism offers an alternative pathway for heavy metal ion detection. A donut-like Cu-Zn-MOF/CuNPs composite enables sensitive and selective electrochemical detection of Ag + via a novel amplification-inhibition mechanism: Cl − enhances the Cu redox signal through CuCl formation, while Ag + competitively binds Cl − to suppress the signal. The sensor achieves a low detection limit of 1.4 nM and good performance in real water samples. Download: Download high-res image (121KB) Download: Download full-size image