In-situ growth of laccase-copper phosphate hybrid nanoflowers on carbon cloth for dual-mode electrochemical and colorimetric sensing of phenolic pollutants.

In this work, an electrochemical/colorimetric dual-mode biosensor based on the in-situ growth of laccase-copper phosphate hybrid nanoflowers on carbon cloth (Lac-Cu3(PO4)2 HNFs@CC) was successfully constructed for the efficient detection of phenolic pollutants. The as-prepared Lac-Cu3(PO4)2 HNFs@CC are flower-like microspheres formed by the self-assembly of nanosheets, and their unique three-dimensional hierarchical flower-like structure effectively promotes substrate diffusion and electron transfer. The as-developed dual-mode biosensor exhibits excellent sensing performance for phenol. In the electrochemical mode, it exhibits a wide linear detection range from 50 nM to 100 μM, a low detection limit of 16.2 nM, a high sensitivity of 2.4 μA μM-1 cm-2, and an apparent Michaelis constant of 0.27 μM. In the colorimetric mode, the absorbance at 505 nm shows a linear dependence on phenol concentration over the range of 5 to 140 μM. Mechanistic studies reveal that the copper active sites serve as the catalytic centers enabling dual-function detection via both electrochemical and colorimetric pathways, wherein the in situ-generated phenoxy radicals function as critical intermediates that effectively bridge the two detection modalities. Furthermore, this biosensor displays broad applicability to various phenolic compounds, including m-cresol, 2,6-dichlorophenol, and hydroquinone, allowing for their precise discrimination based on distinct electrochemical potentials and colorimetric responses. It also possesses outstanding interference immunity, stability, and high reproducibility. When applied to the analysis of semi-coke wastewater, the as-developed dual-mode biosensor shows excellent accuracy and reliability, thereby providing an effective analytical platform for monitoring phenolic contaminants.