Zinc oxide (ZnO) is a versatile photocatalyst with promising applications in environmental remediation1. Its performance is strongly influenced by morphology, crystallinity, and the nature of exposed crystal facets. In this study, we investigated the role of different complexing agents in shaping ZnO nanostructures during hydrothermal synthesis. Among the ligands tested—urea, HMTA, sucrose, and spermidine—only spermidine, a bio-inspired triamine2, promoted the formation of highly anisotropic nanowires with dominant polar {0001} facets. This coordination-driven anisotropic growth is attributed to the ability of spermidine's amine groups to bind Zn²⁺ ions and adsorb selectively on lateral facets, thereby suppressing radial expansion and promoting axial elongation3. The resulting structures exhibited markedly improved photocatalytic performance for methylene blue degradation under UV irradiation (k = 0.0739 min⁻¹), comparable to commercial ZnO nanorods. These results confirm that morphology-driven strategies can offer a scalable alternative to doping or hybridization for enhancing photocatalytic efficiency. They also highlight the potential of underexplored ligands like spermidine as sustainable agents for green nanomaterial synthesis. Altogether, this work provides new insights into the control of anisotropic oxide growth via ligand coordination, with broader implications for the design of functional materials in photocatalysis and beyond.
(1) Rasheed, H. M.; Aroosh, K.; Meng, D.; Ruan, X.; Akhter, M.; Cui, X. A Review on Modified ZnO to Address Environmental Challenges through Photocatalysis: Photodegradation of Organic Pollutants. Materials Today Energy 2025, 48, 101774. https://doi.org/10.1016/j.mtener.2024.101774.
(2) Della Rosa, G.; Di Corato, R.; Carpi, S.; Polini, B.; Taurino, A.; Tedeschi, L.; Nieri, P.; Rinaldi, R.; Aloisi, A. Tailoring of Silica-Based Nanoporous Pod by Spermidine Multi-Activity. Sci Rep 2020, 10 (1), 21142. https://doi.org/10.1038/s41598-020-77957-4.
(3) Parize, R.; Garnier, J.; Chaix-Pluchery, O.; Verrier, C.; Appert, E.; Consonni, V. Effects of Hexamethylenetetramine on the Nucleation and Radial Growth of ZnO Nanowires by Chemical Bath Deposition. J. Phys. Chem. C 2016, 120 (9), 5242–5250. https://doi.org/10.1021/acs.jpcc.6b00479.
