Fabrication of Hollow Anatase Structure by Using Sea Wool Sponges
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1094-DD07-17
Fabrication of Hollow Anatase Structure by Using Sea Wool Sponges Fung-luen Kwong, and Dickon H. L. Ng Department of Physics, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong ABSTRACT Highly porous carbon-doped anatase was produced by a simple and time-saving method. The product was prepared by using sea wool sponges and a titanium-contained organic solution. The intermediate product was pyrolyzed sponges coated with amorphous anatase. When further annealed, the final product was an entirely carbon – anatase product with the original structure of sea wool sponges. The struts in the carbon – anatase product were hollow with wall thickness less than 300 nm. Cathodoluminescence measurement showed that this C-TiO2 product was sensitive to visible light.
INTRODUCTION Anatase is one of the polymorphic phases of TiO2. It is commonly used in photo-catalysis for decomposing organic pollutants, such as CCl4 [1], formamide [2], and dichlorovos [3], into non-toxic compounds. Its photo-catalytic ability is higher than that of rutile and brookite. However, its wide band gap (~3.2eV) limits its application, because it requires ultra violet radiation to activate the photo-catalytic effect. Doping elements such as nitrogen [4] and carbon [5] into anatase structure or embedding functional group into anatase matrix [6] can make it perform similar duties under visible light. Traditionally, making anatase into thin film is one of the ways to improve the effectiveness of its photo-catalysis [7]. The sea wool sponges survive in the sea water, and have porous texture with large surface areas. If their structures are to be converted to biomorphic materials, they could be very useful as functional materials with huge absorbance. Our work is to convert sea wool sponges into porous carbon-doped anatase products. Since the sponges are organic materials, the carbon doping into the anatase structure could happen spontaneously during fabrication. In making anatase, low temperature (below 500oC) is often used in order to avoid the irreversible transformation of anatase to rutile [8,9]. As a result,
the fabrication time is usually prolonged over 24 hours. In this work, highly porous carbondoped anatase was produced by a simple and time-saving method.
EXPERIMENTAL SECTION The commercially available sea wool sponges (from Crabtree and Evelyn) were cut into 15 cm3 cube. They were etched by diluted nitric acid before being washed and dried. The sponges cubes were then soaked into a 4M titanium(IV) bis(ammonium lactato) dihydroxide solution (TALH, Sigma-Aldrich). The infiltrated sponges were dried at 80oC in an oven with continuous horizontal rotation. They were then annealed at different temperatures below 600oC in flowing air for 1 hour. The morphology and the chemical composition of the annealed sample was studied by electron scanning microscopy (SEM, Leo 1450VP) equipped with energy dispersive x-ray spectroscopy (EDS). The crystalline phase was determined by x-ray diffractometry (XRD) using a Huber diffractometer with a
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