Lignosulfonate supported CeO₂/Co₃O₄ nanocomposites with dual enzyme activity for colorimetric detection of catechol...

Catechol poses significant environmental and health risks, colorimetric sensing is an effective method for catechol detection. Constructing nanozyme with enhanced activity is necessary in colorimetric sensing. In our work, sodium lignosulfonate (SL) supported CeO₂/Co₃O₄ heterojunctions (SL/CeO₂/Co₃O₄) have been prepared, compared to CeO₂/Co₃O₄, the catalytic performance of SL/CeO₂/Co₃O₄ is much enhanced. The improved nanozyme activity is ascribed to the increased specific surface area and more exposed active sites, which made the catalyst more effective in adsorption and activation of reactants. Besides, the oxygen vacancies induced by SL and the sulfur/carbon-containing groups due to the low-temperature calcination also exert a synergistic effect on the enhanced activity. Surprisingly, the SL/CeO₂/Co₃O₄ exhibit dual enzyme activities (peroxidase/oxidase), mechanistic studies revealed that the oxidase activity was derived from the oxygen vacancy and O₂^•-, while the peroxidase activity originated from ¹O₂ and O₂^•- generated during H₂O₂ catalysis. Leveraging the excellent peroxidase activity, a colorimetric detection platform for catechol was developed, demonstrating high selectivity, strong anti-interference capability, and a good linear relationship in the range of 0.05-1.0 μM, with a detection limit as low as 10 nM. In addition, a smartphone-assisted visual ratiometric biosensor was designed using Image J software, enabling portable and quantitative determination of catechol in water samples. This research not only developed a novel lignin-based nanozyme with high catalytic activity, but also established a smartphone-enabled ratiometric colorimetric sensor, providing a promising solution for the detection of hazardous substances.