Spherical Polyelectrolyte Brush Nanoreactor: Preparation of Hollow TiO₂ Nanospheres and Characterization by Small Angle X-Ray Scattering

Titanium dioxide (TiO₂) hollow nanoparticles present significant potential for photocatalytic applications while their straightforward preparation with precise structure control is still challenging. This work reports the approach to preparing tunable hollow TiO₂ nanospheres by utilization of spherical polyelectrolyte brushes (SPB) as nanoreactors and templates. During the preparation, the evolution of the structure was characterized by small angle X-ray scattering (SAXS), and in combination with dynamic light scattering and transmission electron microscopy. The formation of TiO₂ shell within the brush (SPB@TiO₂) is confirmed by the significant increase of the electron density, and its internal structure has been analyzed by fitting SAXS data, which can be influenced by Titanium precursors and ammonia concentration. After calcining SPB@TiO₂ in a muffle furnace, hollow TiO₂ nanospheres are produced, and their transition to the anatase crystal form is triggered, as confirmed by X-ray diffraction analysis. Utilizing the advantages of their hollow structure, these TiO₂ nanospheres exhibit exceptional catalytic degradation efficiency of methylene blue (MB), tetracycline (TC), and 2,4-dichlorophenoxyacetic acid (2,4-D), and also demonstrate excellent recyclability.