Preparation And Characterization Of Soluble TiO₂ Nanocrystals And TiO₂/Graphene Composites

Titanium dioxide (TiO₂) is one of the most studied semiconductor materials due toits unique optoelectronic and photochemical properties, chemical inertness,nontoxicity and extensive resources. It has been demonstrated to have promisingapplications in many fields, including photocatalysis, photovoltaic cells, sensors, andelectronic devices, etc. In this paper, we have focused our attention on synthesis ofwater-soluble TiO₂ nanocrystals with high photocatalytic properties and research ofthe method to prepare TiO₂/Graphene composites.The main contents are as follows:1) Preparation and characterization of water-soluble TiO₂: recently, monodispersedTiO₂ nanoparticles (NPs) have been synthesized by using hydrophobic fattyacid (oleic acid) as a surfactant, which is not proper for the use of TiO₂ asphotocatalyst in many applications that carried out in aqueous solution. In this work,we prepare PEG 400 caped TiO₂ nanocrystals by using tetrabutyl titanate as thetitanium source and hydrophilic PEG 400 molecules as surfactant and solvent. Theprepared nanocrystals can be well dispersed in water, and the crystalline form of theproducts can be controlled by the addition of HCl in the system. Besides, wediscussed the formation mechanism of the water-soluble TiO₂ nanocrystals and theinfluence of reaction temperature and time to the nano-TiO₂ products.2) Photocatalytic property of the prepared water-soluble TiO₂ nanocrystals: wechose methyl orange as the pollutant to be degraded, and evaluated the photocatalyticproperties of the prepared water-soluble TiO₂ products with different crystal phases.The results indicate that the fresh PEG-capped anatase TiO₂ NPs show the bestphotocatalytic activity, even better than commercial P25, which may result from thehigh crystallinity, the pure anatase phase, small size and enhanced surfaceabsorbability and solubility associated with the existence of PEG 400 on the NPsurface.3) Preparation and characterization of TiO₂/Graphene composites: Graphene hasbeen considered as one of the most promising support for nanocomposites because of its excellent properties and unique structure. Herein, we developed an effective routefor preparing the TiO₂/Graphene composites based on the solvothermal hydrolysis oraminolysis process in organic media. The morphologies of the TiO₂ NPs loaded on theGraphene surface can be well controlled from nanorods to nanodots. The resultinghybrids are dispersible in apolar media, which provides possibilities of manipulatingthe hybrids in apolar solvents for various applications. To prove it's a universalapproach, by changing Graphene to Graphene oxide (GO), we successfully preparedTiO₂/GO composite. We also used the method to prepare water-solubleTiO₂/Graphene composite, and it worked, too.