Synthesis Of Hierarchical Core-shell Anatase TiO₂and Study On Its Formation Mechanism

Nano material has been synthesized and used widely in the field of biology,photoelectricity, and medical science for its excellent chemicophysical properties.Nanomaterial shows us a completely different “world” from the world we live with itsunique size, structure and morphology. However, nano material shows totallydifferent properties for different size, structure and morphology. How to synthesisnanomaterials with specific shape and structure became the hotspot of research. TiO₂nanomaterials with specific core-shell structure were synthesized in different systemsin this work. The formation mechanism of the core-shell structure were developed andthe effects of synthesis conditions on the morphology of the final product wereillustrated.TBOT was used as Ti source and TBOT/CO（NH2）2/N（CH₂CH₂OH）₃/C₂H₅OHand TBOT/H₂O/Na₂EDTA/H₂O were used as basic reaction systems, X-raydiffraction （XRD）, scanning electron microscopy （SEM） and transmission electronmicroscopy （TEM） were used to, characterize the structure and morphology of theproduct. The effects of synthesis conditions such as reaction time, adding sequence,initial temperature, adding kinds, material concentrations, components andposttreatments on the structure of the product were investigated. The results show thatthe synthesis conditions have important effects on the morphology of the final product.Through the analysis of various morphologies under different conditions, theformation mechanisms of different structure were discussed. From the SEM and TEMimages, the core-shell structure was rather weak. After2hours calcination at500℃,the core-shell structure became clear while the hierarchical structure almostdisappeared, which may due to the thin plate structure on the surface. In the lattersystem, the structure of the final product was greatly affected by the strong baseenvironment and the solubility of the surfactant in the system. The amount of water inthe system controls activation of the precursor and crystal growth. Most products inthis system present as two-dimensional structure samples formed which are fardifferent from the system in the former.