Crystallographic facet engineering of ZnO nanoparticles for photocatalytic organic pollutant degradation and antibacterial activity

Abstract

Utilizing crystallographic engineering, dual-functional zinc oxide nanoparticles (ZnO-NPs) are revealed to have superior antimicrobial and photocatalytic properties. They surpass traditional ZnO (20–40% degradation, <25 mm zones) by achieving 34 mm inhibition zones against Staphylococcus aureus and 50% Congo red degradation under visible light. Four distinct synthesis methods were used to create the facet-tuned NPs: PEG-assisted co-precipitation (Z1), oleic acid-modified hydrothermal (Z2), conventional hydrothermal (Z3), and Canna indica-mediated green synthesis (Z4). XRD analysis revealed that Z1/Z3 (crystallite size: 34.40–36.69 nm, microstrain: 0.1334–0.1394) and Z2/Z4 (84.51–97.20 nm, microstrain: 0.0611–0.0816) grew preferentially in the (101)/(103) and (112)/(110) planes, respectively. FESEM showed that the performance of nanodiscs (Z1), cubic rods (Z2), plate-needle hybrids (Z3), and nanorods (Z4) depended on their morphology. While FTIR found residual CO/C–O groups impacting surface contacts, EDX verified high Zn purity (>86%). Defect-rich E2 (high) phonon modes (439 cm⁻¹) were validated by Raman spectroscopy, confirming defect-mediated charge separation, which is essential for photocatalytic effectiveness. The effectiveness of Z2/Z4 was demonstrated by antibacterial tests (34–26 mm against S. aureus and 18–10 mm against E. coli), using nanorod-driven membrane penetration and Zn²⁺ release. The dual function of the (112) plane, which connects the production of ROS and the inhibition of bacteria, creates a model for ZnO-NPs of the future in the fight against healthcare infections and water pollution.