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Bio-inspired Mineralization Process of TiO2 and CaCO3 in Agarose Gel Medium

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Tutor: YangDong
School: Tianjin University
Course: Biochemical Engineering
Keywords: bio-inspired mineralization,agarose gel,TiO2,CaCO3,PAA
CLC: O611.3
Type: Master's thesis
Year:  2011
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Bio-inspired mineralization is the leading edge and hotspot of the research in the fields including chemistry, biology and materials science at present. More and more efforts prove that the biomolecules usually form the gelatinous reticular matrix in the organism, which can influence the biomineralization process. Therefore, the research of bio-inspired mineralization processes in the gel medium is important to understand the biomineralization mechanism, and guide the design and synthesis of advanced functional materials. However, the biomineralization about oxides and the actual application of the samples were seldom studied. There are also rarely research about the synergy between gel medium and soluble organic polymeric and/or hard dissolved organic matrix. This article focuses on the bio-inspired mineralization of TiO2 in gel medium and the photocatalytic activity of the samples, and also investigates the bio-inspired mineralization of CaCO3 in the presence of PAA. A proposed mineralization mechanism of inorganic crystals formed in the gel medium has been elucidated.The chemical composition and structural properties of these samples were investigated by SEM¡¢TEM¡¢XRD¡¢TGA-DSC¡¢BET¡¢FTIR and UV-Vis spectroscopy, and photocatalytic activity of TiO2 were studied though degradation of methyl orange solution.Firstly, the agarose gel with protamine was immersed into Ti-BALDH precursor solution. An anatase microcrystal titania hollow nanospheres were obtained as a result. The samples which had protamine and agarose gel within it exhibited two typical porous structure and large surface area. A mechanism is postulated to tentatively elucidate the formation of titania hollow nanospheres mineralized in agarose gel medium. First of all, the protamine and the agarose gel were tend to aggregate together to form micelles. Then TiO2 particles hydrolyzed from Ti-BALDH were coated on the surface of the micells and finally formed the core-shell structure. Finally, the titania hollow nanospheres with mesoporous on the shell were obtained after removed the protamine and the agarose gel by hot water. The samples possessed high photocatalytic activity as they had high efficiency for degradation of methyl orange solution.Secondly, the CaCO3 samples were mineralized through the diffusion of CO2 into the agarose gel which contained CaCl2 and PAA at 30¡æ. The addition orders of agarose, PAA and CaCl2 resulted in the different size and shape of the samples. The spheres were obtained at a high proportion of PAA and Ca2+ while the rhombohedron appeared at a low proportion. The possible reason is that the spherical colloidal particles were formed due to the complexation of PAA with calcium ions. The spherulitic character of crystallization is preserved by the high viscosity of gel in the presence of PAA. A spherulitic template was formed duing to the interaction between PAA and agarose.
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