Sunlight-Driven Photocatalysis in Hydrothermally Coupled ZnO/Fe₃O₄ Heterostructures from Bioengineered Nanoparticles

Area of Science:

• Materials Science
• Environmental Science
• Nanotechnology

Background:

• Developing sustainable and efficient photocatalysts is crucial for environmental remediation.
• Biogenic synthesis routes offer eco-friendly alternatives to traditional chemical methods.
• Heterostructures can enhance photocatalytic activity through improved charge separation.

Purpose of the Study:

• To develop a fully biogenic synthesis route for ZnO, Fe3O4, and ZnO/Fe3O4 heterostructures.
• To establish a link between synthesis, structure, and photocatalytic function.
• To evaluate the efficiency of ZnO/Fe3O4 heterostructures for sunlight-driven wastewater remediation.

Main Methods:

• Biogenic synthesis of ZnO and Fe3O4 nanoparticles.
• Hydrothermal coupling to form ZnO/Fe3O4 heterostructures.
• Characterization using optical, photoluminescence, and magnetic analyses.
• Photocatalytic degradation of methylene blue under natural sunlight.
• Reusability and scavenger tests to elucidate degradation mechanisms.

Main Results:

• Phase-pure ZnO and Fe3O4 nanoparticles formed a biphasic ZnO/Fe3O4 heterostructure.
• Optical analysis revealed distinct band gaps (Eg = 2.36 eV for ZnO, 1.46 eV for Fe3O4).
• ZnO/Fe3O4 exhibited soft-ferrimagnetic properties enabling magnetic recovery.
• Under sunlight, ZnO/Fe3O4 showed significant methylene blue degradation (65%) with good reusability.
• Scavenger tests indicated OH• and O2-• radicals played key roles in degradation.

Conclusions:

• The ZnO/Fe3O4 heterostructure functions as a defect-rich S/Z-scheme-like material.
• The biogenic synthesis provides a green, sunlight-operable, and recyclable platform.
• This material shows promise for affordable and sustainable wastewater remediation.