Defect Engineered Bi₂Te₃ Nanosheets with Enhanced Haloperoxidase Activity for Marine Antibiofouling

Defective bismuth telluride (Bi₂Te₃) nanosheets, an artificial nanozyme mimicking haloperoxidase activity (hPOD), show promise as eco-friendly, bactericidal, and antimicrofouling materials by enhancing cytotoxic hypohalous acid production from halides and H₂O₂. Microscopic and spectroscopic characterization reveals that controlled NaOH (upto X = 250 µL) etching of the nearly inactive non-transition metal chalcogenide Bi₂Te₃ nanosheets creates controlled defects (d), such as Bi³⁺species, in d-Bi₂Te₃-X that induces enhanced hPOD activity. d-Bi₂Te₃-250 exhibits approximately eight-fold improved hPOD than the as-grown Bi₂Te₃ nanosheets. The antibacterial activity of d-Bi₂Te₃-250 nanozymes, studied by bacterial viability, show 1, and 45% viability for Staphylococcus aureus and Pseudomonas aeruginosa, respectively, prevalent in marine environments. The hPOD mechanism is confirmed using scavengers, implicating HOBr and singlet oxygen for the effect. The antimicrofouling property of the d-Bi₂Te₃-250 nanozyme has been studied on Pseudomonas aeruginosa biofilm in a lab setting by multiple assays, and also on titanium (Ti) plates coated with the nanozyme mixed commercial paint, exposed to seawater in a real setting. All studies, including direct microscopic evidence, exhibit inhibition of microfouling, up to ≈73%, in the presence of nanozymes. This approach showcases that defect engineering can induce antibacterial, and antimicrofouling activity in non-transition metal chalcogenides, offering an inexpensive alternative to noble metals.