Fabrication of a novel reusable nanozyme by immobilizing Co-doped carbon dots on nanocellulose aerogels for efficient dyes degradation.

Abstract

Carbon dot-based nanozymes have gained significant attention, but their application in dye degradation remains limited due to low activity and challenges in recovery and reuse. To overcome these limitations, high peroxidase-active Co-doped carbon dots (CoCDs) with surface amines were synthesized via hydrothermal method and immobilized onto TEMPO-oxidized cellulose nanofibrils (TOCNF) aerogels using EDC/NHS coupling. For the first time, this study investigates the dye degradation efficiency of CDs nanozyme. CoCDs with 1.456 % Co content exhibited excellent peroxidase-like activity with favorable kinetics (K_m = 1.746 mM, V_max = 22.05 × 10^-8 Ms^-1 for TMB and K_m = 1.542 mM, V_max = 23.54 × 10^-8 Ms^-1 for H₂O₂). The immobilized CoCDs enhanced the structural stability, and shape recovery of aerogels, even after multiple compressions. CoCDs/TOCNF aerogel with maximum CoCDs (114.7 mg/g) exhibited superior degradation efficiency for various dyes, including methyl orange (MO), methylene blue (MB), and rhodamine B (RhB), with rate constants of 12.7 × 10^-3, 17.4 × 10^-3, and 12.2 × 10^-3 min^-1, respectively. Mechanistic studies revealed the major role of hydroxyl radicals in dye degradation. The aerogels exhibited exceptional recyclability with all dyes. This stable and recyclable nanozyme with high catalytic activity presents a promising avenue for environmental remediation.