Facile and controllable preparation of mesoporous TiO2 using poly（ethylene glycol） as structure-directing agent and peroxotitanic acid as precursor

This work demonstrated that mesoporous TiO= （meso-TiO2） with con- trollable mesoporous and crystalline structures can be facilely prepared by using poly （ethylene glycol） （PEG） as structure-directing （SD） agent and peroxotitanic acid （PTA） as precursor. Meso-TiO2 with high specific surface area （157 m2.g-1）, pore volume （0.45 cm3.g-1） and large mesopore size of 13.9 nm can be obtained after calcination at 450℃. Such meso-TiO2 also shows relatively high thermal stability. BET surface area still reaches 114 m2-g-1 after calcination at 550℃. In the synthesis and calcination process, PEG that plays multiple and important roles in delivering thermally stable and tunable mesoporous and crystalline structures shows to be a suitable low-cost SD agent for the controllable preparation of nanocrystalline meso-TiO2. The photocataiytic activity tests show that both high surface area and bi-crystallinity of obtained meso-TiO2 are important in enhancing the performance in photo-decomposing Rhodamine B in water.

Synthesis, characterization and photoactivity of bi-crystalline mesoporous TiO2

Mesoporous titania （meso-TiO2） has received extensive attention owing to its versatile potential applications. This paper reports a low-temperature templating approach for the fabrication of meso-TiO2 using the peroxo titanic acid （PTA） sol as precursor and Pluronic P123 as nonionic template. The TGA, XRD, N2 sorption, FE-SEM and HRTEM were used to characterize the obtained samples. The results showed that meso-TiO2 with high surface area up to 163 m2.g^-1 and large pore volume of 0.65 cm3.^-1 can be obtained. The mesopore sizes can be varied between 13 and 20 nm via this synthesis approach. The amount of P123 and the calcination conditions were found to have great influence on the mesoporous and crystalline structures of meso-TiO2. The photocatalytic activity testing clearly shows that the high surface area and bi-crystallinity phases of meso-TiO2 play important roles in enhancing photocatalytic properties of meso-TiO2 in photo-decomposing Rhodamine B in water.

Preparation and Characterisation of Sr2CeO_4:Eu^(3+) Rare Earth Luminescent Material by High Temperature Mechano-Chemical Method

A novel, high-temperature, mechano-chemical（HTMC） method was developed to synthesise singlephase Sr_2CeO_4：Eu^（3＋）phosphor. Phosphors were characterised by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and luminescence spectra. Compared with phosphors prepared by the traditional hightemperature solid state method and citric acid gel method, single-phase Sr_2CeO_4：Eu^（3＋）powders by using the HTMC method, with small average particle sizes of about 5 μm, a narrow size distribution range and uniform dispersion, were prepared at 800 ℃, and reached their maximum luminescent intensity at 900 ℃.Under ultraviolet excitation at 298 nm, the sample showed good luminescence with the strongest red light of 616 nm. However, Sr_2CeO_4：Eu^（3＋）was prepared at the higher temperature of 1100 ℃ by solid state method and citric acid gel method. The particle size was too large and uneven with phosphor agglomeration by high-temperature solid state method. The luminescent intensity reached a maximum for Sr_2CeO_4：Eu^（3＋）phosphor at a synthesis temperature of 1100 ℃ by using the high-temperature solid state method, and at 1200 ℃ by both citric acid gel and chemical precipitation methods. Furthermore, the advantages of the Sr_2CeO_4：Eu^（3＋）powder prepared by HTMC method were discussed compared with that prepared using traditional high-temperature solid state and citric acid gel methods.