Jinting Jiu

Morphology Control of Anatase TiO2 by Surfactant-assisted Hydrothermal Method*

By hydrolysing titanium isopropoxide in a long hydrocarbon chain surfactant-containing solution, TiO2 fine particles with a diversity of well-defined morphologies was synthesized in this study by a hydrothermal route. The structural change during the formation process was monitored by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. TiO2 with various morphologies such as particle, sheet, rod, tube and flower-like shape was obtained by carefully controlling the preparation conditions. The experimental results show that the pH value is crucial for shape control of the produced TiO2 because it can change the charge state of the surfactant in the solution and the adsorption potential of the surfactant on the TiO2 surface. The shape evolvement of anatase TiO2 was elucidated by quenching the reaction at different stage and the formation mechanism of different shaped TiO2 was suggested.

Preparation of nanoporous MgO using gel as structure-direct template

MgO with various nanoscaled pore diameters were formed from magnesium nitrate adsorbed into the gel templates that are synthesized from hydroxyl ethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) where the EGDMA worked as the cross-linker. The effects of molar ratio [HEMA]/[EGDMA] in the gel template on the porous structure of MgO formed in the template were investigated. The results indicated that the pore diameter of MgO could be varied by the [HEMA]/[EGDMA] molar ratio which directly affects the templating structure of gel. The smaller pore size and distribution were obtained with the increased molar ratio. The mechanism of the reaction was simply speculated.

Preparation of nanoporous ZnO using copolymer gel template

Mesoporous ZnO were prepared using copolymer gel template of hydroxyl ethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) where the latter worked as the cross-linker. The effects of molar ratio [HEMA]/[EGDMA] in copolymer on the porous structure of ZnO formed in the template gel were investigated. The results indicated that the pore size and its distribution of the mesoporous ZnO could be drastically varied by [HEMA]/[EGDMA] molar ratio which directly affects the templating gel structure. Smaller pores and narrow pore size distribution were obtained with the molar ratio increased. The formation mechanism of mesoporous structure was discussed based on these experimental results.

Preparation of nanoporous silica using copolymer template

Silica solids with different nanoscaled pore diameters were formed from tertraethoxysiliane (TEOS) and copolymer gel of hydroxyl ethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) where the latter worked as the cross-linker. The effects of molar ratio [HEMA]/[EGDMA] of copolymers on the porous structure of silica formed in the template gel were discussed. The properties and structure of gel and porous silica were characterized by Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results indicated that the pore diameter of silica could be varied by the [HEMA]/[EGDMA] molar ratio which directly affects the templated structure of copolymer gel. The larger pore diameter was obtained with the increased molar ratio, which corresponds to the decrease in the cross-link density. FT-IR and TGA suggested that the silica moiety is bonded to the network of the copolymer gel due to the gel/silica affinity based on the hydrogen bonding.

Preparation of oxide with nano-scaled pore diameters using gel template

Silica, MgO and ZnO with various nano-scaled pore diameters were prepared with template gel synthesized from hydroxyl ethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA), where the latter worked as the cross-linker. The effects of the molar ratio [HEMA]/[EGDMA] in the gel were discussed in relation to the resultant porous structure. The pore diameter of the oxide was shown to be varied by the molar ratio [HEMA]/[EGDMA] which directly affects the structure of gel, particularly the mesh size. From the different trend in the variation of the pore size in the oxide, a contrasting trend depending on the molar ratio [HEMA]/[EGDMA] has been found for silica, MgO and ZnO. The mesh-filling and hydrogen bonding mechanism has been considered to explain the formation process of gel templated nanoporous silica and ZnO or MgO, respectively.