Surface‐Defect Engineering of ZnO Nanoparticles via Nonthermal Plasma for Efficient Photocatalysis

ABSTRACT Zinc oxide (ZnO) nanoparticles were synthesized via a sol–gel route and subsequently modified by nonthermal plasma (NTP) for controlled durations (2, 6, and 10 min) to investigate the influence of plasma exposure on their structural and photocatalytic behavior. X‐ray diffraction confirmed the preservation of the hexagonal wurtzite phase, while moderate plasma treatment enhanced crystallinity and reduced lattice strain. Raman analyses evidenced the formation of oxygen vacancies and surface hydroxyl groups, facilitating improved light absorption and charge‐carrier separation. UV–vis diffuse reflectance spectra showed a redshift in the absorption edge with a slight band‐gap narrowing from 3.15 eV (pure) to 3.08 eV (6 min), accompanied by an increase in BET surface area from 7.35 to 11.09 m 2 /g. The plasma‐treated ZnO samples exhibited significantly enhanced photocatalytic degradation of methylene blue (MB) under UV light, achieving up to 74% efficiency compared to 54% for pristine ZnO. The 6‐min plasma exposure offered the most balanced improvement in crystallinity, surface area, and lattice stability, defining the optimal plasma modification condition. This study provides valuable insight into the defect‐controlled design of ZnO nanoparticles via NTP modified surface engineering.

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