Size Adjustment of Zinc Oxide Nanostructures by Ultrasmall TiO ₂ Nanoparticles

The interaction of positively charged ZnO nanorods (<i>nr</i>-ZnO) with negatively charged ultrasmall amorphous titanium dioxide (<i>am</i>-TiO₂) nanoparticles (NPs) induced a decrease in the <i>nr</i>-ZnO particle size while forming nanostructured core@shell <i>x</i>ZT materials (Zn/Ti molar ratios of 16, 8, 4, 2, and 1). Such an unexpected outcome was assigned to the high affinity and Zn-(II) ion adsorption capacity of <i>am</i>-TiO₂ NP, as confirmed by the amount of Zn-(II) ion in equilibrium in solution with <i>am</i>-TiO₂ determined by ICP-OES and the respective adsorption isotherm profile. The changes in size, morphology, and crystallinity compared to pure <i>nr</i>-ZnO were monitored by FTIR and UV-vis spectroscopy, dynamic light scattering (DLS), and X-ray diffractometry (XRD) and confirmed by transmission electron microscopy (TEM), suggesting a promising strategy to explore size-dependent nanoscale phenomena in ZnO-based nanomaterials.