Dual-Function Carbon Nanotube–Nanoflower Platform for Integrated Phenol Removal and Detection

Phenol is a toxic pollutant in industrial effluents, requiring treatment strategies that are efficient, low-cost, and adaptable to practical applications. Here, we report a dual-function platform that combines carbon nanotube (CNT) filtration for phenol removal with enzyme nanoflowers (NFs) for subsequent detection. Vertically aligned CNTs were synthesized by chemical vapor deposition (CVD), acid-functionalized to introduce carboxyl groups, and assembled into porous filter structures. The filters achieved over 96% phenol removal at neutral pH (pH 7.0), with similar performance under acidic conditions (pH 3.5, 96.3%). Removal decreased moderately at basic pH (pH 10.5, ∼91%) due to electrostatic repulsion between carboxylated CNTs and phenolate anions. To quantify residual phenol, a colorimetric assay was established using laccase (Lac) NFs, horseradish peroxidase (HRP) NFs, a cosynthesized HRP@Lac hybrid NF, and a physical mixture of Lac + HRP NFs. All enzyme systems produced quinone-imine with comparable efficiencies, yielding absorbance maxima between 0.333 and 0.379 at 505 nm for 1 mM phenol. The hybrid HRP@Lac NFs exhibited the highest colorimetric detection sensitivity toward residual phenol, confirming the superior catalytic performance of the hybrid nanozyme in the dual-function CNT–NF platform. The integration of CNT-based adsorption with NF-mediated colorimetric detection provides a robust route for simultaneous remediation and monitoring of phenol in water. This combined approach holds promise for scalable, low-energy wastewater treatment technologies with built-in sensing capability.