Temperature-Driven Strategy for Engineering of Al-Doped ZnO Mesocrystals’ Hierarchical Architecture

Nanomaterial functionality is influenced by particle size, morphology, and composition. This study introduces a novel temperature-controlled sol–gel method to tailor hierarchical nanostructures, utilizing Al-doped ZnO (AZO) nanoparticles as a case study. AZOs’ electrical and optical properties are critical for photovoltaics applications, where controlling crystal properties to optimize conductivity and transparency is key. AZO nanoparticles were synthesized from zinc acetylacetonate hydrate, aluminum isopropoxide, and benzylamine in a closed batch reactor. By adjusting temperature profiles, controlling synthesis temperature and ramp-up duration under an exponential (PT1) heating scheme, the method enabled the formation of a three-level hierarchical architecture, in which primary AZO nanocrystals assembled into mesocrystals that subsequently aggregated into larger structures. Characterization via electron microscopy, X-ray scattering, and dynamic light scattering reveals that minor temperature variations (105 to 125 °C) affect particle morphologies, exhibiting tunable size, ranging from 18 to 41 nm, with higher temperatures promoting aggregation despite existing structure shrinkage. This highlights the strong dependency of nucleation and structural formation on temperature profiles, offering a versatile method for tuning nanomaterials for advanced applications.