Browsing by Author "Dong, Ji-Yao"

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Growth of ZnO Nanostructures with Controllable Morphology Using a Facile Green Antisolvent Method
(2010-05-20)
Dong, Ji-Yao
;
Hsu, Yung-Jung
;
Wong, David Shan-Hill
;
Lu, Shih-Yuan
;
材料科學與工程學系
An environmentally friendly antisolvent approach, which involves only biocompatible chemicals and mild processing conditions, was developed to prepare various ZnO nanostructures including twin-cones and nanorods with controllable dimensions, The method was based on the dissolution of ZnO powders in a deep eutectic solvent (DES), followed by precipitation of ZnO nanostructures from the DES upon introduction of an antisolvent. It is the first example of the room temperature ionic liquid based antisolvent process for preparation of nanomaterials. Through suitably modulating the processing conditions, such as the ethanol content of the antisolvent and the injection time of the ZnO-containing DES, the morphology of the resulting ZnO nanostructures can be readily controlled. Anisotropic crystal growth was achieved without severe reaction conditions, such as high temperatures and high vacuums, or use of environmentally harmful chemicals, such as long carbon chain surfactants and capping reagents. The present method can be readily extended to produce versatile nanostructures of other functional materials.
Single-crystalline mesoporous ZnO nanosheets prepared with a green antisolvent method exhibiting excellent photocatalytic efficiencies
(2012)
Dong, Ji-Yao
;
Lin, Cheng-Hsien
;
Hsu, Yung-Jung
;
Lu, Shih-Yuan
;
Wong, David Shan-Hill
Single-crystalline mesoporous ZnO nanosheets were prepared with a green, deep eutectic solvent based antisolvent process followed by calcination at 300 degrees C. The antisolvent procedure led to formation of nanosheets of a mixed composition of zinc carbonate hydroxide and ZnO, calcination of which generated the product. The product nanosheets were ultrathin with a thickness of around 10 nm and pore sizes increasing from less than 10 nm to several tens nanometers with increasing calcination time and temperature. These nanosheets exhibited excellent photocatalytic efficiencies as good as that of a commercial photocatalyst, P-25 TiO2 in terms of photocatalytic degradation of a model pollutant, methylene blue. The success is attributable to the structural advantages of the nanosheets of being ultrathin, mesoporous, and single-crystalline.
Ultrafast formation of ZnO mesocrystals with excellent photocatalytic activities by a facile Tris-assisted antisolvent process
(2011)
Dong, Ji-Yao
;
Lin, Wei-Hao
;
Hsu, Yung-Jung
;
Wong, David Shan-Hill
;
Lu, Shih-Yuan
Ultrafast formation of ZnO mesocrystals was achieved with a facile, green, Tris-assisted, room temperature ionic liquid based antisolvent process. A deep eutectic solvent, formed by simply mixing and heating urea and choline chloride at 70 degrees C, served as the solvent for ZnO, whereas Tris-containing de-ionized water acted as the anti-solvent to trigger the ultrafast formation of ZnO mesocrystals at 70 degrees C. The product mesocrystals were mesoporous and near-single-crystalline with high specific surface areas, showing excellent photocatalytic activities toward photodegradation of methylene blue, comparable to that of a commercial photocatalyst, P-25 TiO(2), which is rarely achieved for pristine ZnO. The present approach is a general one and can be readily extended to production of mesocrystals of other functional metal oxides.