Homogeneous electroanalysis coupled with colorimetry dual-mode sensing of silver ion in water based on target-inhibited peroxidase activity of Pt@ZIF-8 nanozyme

Electrochemical sensing is the commonly used method for the detection of heavy metal silver ion (Ag+), while the conventional electrochemical sensors generally require the existence of electrode modifications and even electrodeposition step coupled with a single-mode readout. Herein, by preparing ZIF-8 organometallic frame load with platinum nanoparticles (Pt@ZIF-8) as nanozyme and o-phenylenediamine (OPD) as colorless substance, taking advantage of the superior peroxidase activity of Pt@ZIF-8 that can catalyze the oxidation of OPD to product electroactive/yellow 2,3-diaminophenazinc and the target-inhibited effect towards nanozyme activity from Ag+, a homogeneous electroanalysis coupled with colorimetry (HEA-CM) dual-mode sensing platform was designed for the first time to detect Ag+. Furthermore, the colorimetric images were converted on a smartphone to digital signals for the quantitative analysis. The designed strategy could offer multiple advantages such as electrodeposition-free, modification-free and dual channel readout. After investigating the sensing mechanism and experimental parameters, the analytical performance of the designed strategy was evaluated, obtaining extremely low detection limit (0.034 nM), reliable recovery rate (99.61 %-101.6 %) and wide linearity. This work offered an effective method for the simple, sensitive, rapid, accurate and multiplexed determination of Ag+, and also opened a new pathway for the detection of other heavy metals based on HEA-CM dual-mode strategy.