An innovative homogeneous electrochemistry coupled with colorimetry dual-model sensing strategy for perfluorooctane sulfonate based on Cu@CuO aerogel nanozyme

By preparing Cu@CuO aerogel as a nanozyme which exhibits prominent peroxidase-like (POD) activity, an innovative homogeneous electrochemistry (HEC) coupled with the colorimetry dual-model sensing strategy is proposed to detect perfluorooctane sulfonate (PFOS) for the first time. Cu@CuO aerogel accelerates the oxidation process of colorless o-phenylenediamine to form yellow 2,3-diaminophenazinc (DAP), and meanwhile, DAP as an electroactive substance creates a reduction peak current upon the electrochemical measurements. Interestingly, in the presence of PFOS, the POD activity of Cu@CuO aerogel is inhibited since the specific coordination between PFOS and Cu(II) can cover the active sites, resulting in the color of the sensing system becoming light and the peak current of DAP decreasing. This innovative dual-mode detection method showed excellent electrochemical detection of PFOS in the concentration range 10.0 ~ 1125.0 nM with a limit of detection (LOD) as low as 3.3 nM and a LOD of 20.8 nM in the colorimetric detection in the range 62.3 ~ 875 nM. Furthermore, the sensor was successfully used for the analysis of real samples with an RSD value  ≤ 6.5%. The successful application of this two-mode sensing method for the determination of PFOS holds promise for the detection of other contaminants in the future. Graphical Abstract