Preparation And Characterization Of Inorganic Functional Materials Based On Biomimetic Mineralization

Biomimetic synthesis inspired from biomineralization has recently been attracting more and more attention as a green and environment-friendly method, and developing to be a multi-disciplinary hot spot. In the usual research of biomimetic mineralization, the regulation of organic Langmuir monolayer on the nucleation and growth of inorganic materials was considered and researched as the important foundation of biomimetic synthesis. However, as an equally important factor for the special structural features of the biogenic minerals, the kinetic control of inorganic crystals growth has not gotten enough attention. If a kinetic control can be introduced into the biomimetic growth system on the basis of regulation effect of organic template through designing novel and suitable interface system, one hand, the biomimetic synthesis can be much closer to a real biomineralization environment, providing a perfect model for biomineralization research; on the other hand, more opportunities to get inorganic materials with special structural features can also be obtained through introducing more conditions of controlling on the basis of a usual organic template system, providing an effective experimental method for controllable fabrication of functional materials. So it is meaningful for both understanding biomineralization phenomena and instructing biomimetic synthesis of inorganic functional materials.In the present doctoral dissertation, the vapor-liquid interface generated by the vapor-diffusion of catalyst served as the other nucleation template providing kinetic control was introduced to a usual biomimetic synthesis system using Langmuir monolayer as organic template, and a novel gas-liquid interface was constructed and used as a biomimetic interface. The regulation effect of Langmuir monolayer on the crystal growth was realized in the novel interface system, meanwhile, the kinetic control of materials was also realized through the pH value gradient, concentration gradient of reactants, and surface tension gradients generated from the vapor-diffusion. The system was a novel method for regulation of inorganic materials growth, and it was named dual-template approach. A series of inorganic materials with special structural features were fabricated through adjusting the organic template and kinetic control conditions, and the function of each template on the crystal growth was also discussed in detail. The experiments showed that the novel interface system unambiguously influenced the growth mode and habit of inorganic crystals, being a promise method for realizing structural controllable fabrication of inorganic functional materials.The research work is composed of following four parts:1. Fabrication and characterization of pure or doped metal hydroxide nitrates thin films by a dual-template approachCompact large area Zn5(OH)8(NO3)2·2H2O, Co5(OH)8(NO3)2-2H2O and Co-doped Zn5(OH)8(NO3)2-2H2O thin films with uniform surface morphology and good orientation were synthesized by an unusual dual-template biomimetic approach. In such a biomimetic system, bovine serum albumin Langmuir monolayer was used as one organic matrix template, whereas the vapor-liquid interface generated by the vapor-diffusion of catalyst (ammonia) served as the other nucleation template providing a kinetic control. The function of dual-template on the formation of thin films was discussed in detail. Such a dual-template approach captures the advantages of both the vapor-liquid interface generated by the vapor-diffusion of catalyst (ammonia) served as the other nucleation template providing a kinetic control and the crystal growth regulated by the organic matrix template providing control of crystal structures and morphologies. The synergetic effect of the dual-template is much different from the regualtion mode of only organic matrix template, changing the morphologies and structure of the inorganic materials. The dual-template system is closer to a real biomineralization environment than the usual Langmuir monolayer system, and it provides a good method for fabricating special structural materials.2. Fractal growth and structure evolution of Zn5(OH)8(NO3)2·2H2OFractal Zn5(OH)8(NO3)2·2H2O materials were fabricated under a BA Langmuir monolayer in the presence of amonia diffusion from a low concentration dilued ammonia solution. The structural evolution from fractal materials to thin films were observed through adjusting the strength of kinetic control. The pH value gradient and concentration gradient of reactants generated from the ammonia diffusion was the main reason for the formation of fractal structure, and it also decided the relation of the three growth rates and the final morphology and structure.3. Fractal aggregation of Ba(NO3)2 crystals under a BA Langmuir monolayer in the presence of ammonia diffusionIn order to research the driving force for the fractal growth, Zn(NO3)2 solution which reacted with NH3 was replaced by Ba(NO3)2 solution which did not react with NH3 as subphase to research the influence of ammonia diffusion on the growth of inorganic crystals. It was found that surface tension gradient could be established and adjusted though the response of surface pressure on the pH value at the Langmuir interface, and fractal Ba(NO3)2 crystals were obtained at the interface. By regulating the concentration of ammonia in the system, the aggregation status of inorganic crystals could be controlled and special aggregation structures could be obtained.4. Morphological and structural regulations of PbS and CdS crystals by kinetic controlThe kinetic control thought in dual-template system was transferred to sulfide materials. PbS and CdS nanomaterials with different structural features were fabricated by changing the kinetic factor of crystal growth through slow catalysis and regulating the properties of the interface. The synergetic effect of the dual-template and the function and control methods of each template on crystal growth was discussed. It was found that the similarity between the 2-D packing of organic molecules and the arrangement of ions in the lattice was an important factor for oriented growth of inorganic crystals, and the matching between the growth rate of crystals and structural template was an important premise for the regulation effect of the template, however, the kinetic control played a key role for such a matching.