Biomimetic Preparation And Morphology Control Of Inorganic Particle Materials

In recent years, the controlled synthesis of inorganic particle materials with specific size and morphology has attracted more and more attraction due to their wide potential applications in many fields such as advanced materials, chemistry, electronics etc. Compared with size control, morphology control is more difficult to achieve by means of the classical procedures of colloid chemistry. Biological systems, however, use biomacromolecules as nucleators, cooperative modifiers, and matrices or molds to exert exquisite control over the processes of biomineralization, resulting in unique inorganic-organic composites with various special morphologies and functions. The strategy of using organic additives and/or templates to control the nucleation, growth, and alignment of inorganic particles has been universally applied for the controllable synthesis of various inorganic materials with unusual and complex forms and phase structures. This dissertation reports the controllable synthesis of several inorganic particle materials with special morphologies and phase structures using inorganic polymer as additives. The main contents of our work are summarized as follows:Firstly, micron-sized barium sulfate particles and BaCO₃ whiskers of various morphologies were prepared via a simple precipitation reaction using poly-(styrene-alt-maleic acid) (PSMA) as a crystal modifier at ambient temperature. The results showed that various morphologies of barite particles, such as flowerlike aggregates, spheres, rod-like superstructures etc. could be synthesized by changing the concentration of PSMA, pH value of solution, and molar ratio of Ba²⁺ to SO₄^2- (R). It was found that the as-prepared BaCO₃ whiskers are single crystals with a diameter range of 100 to 300 nm, and grow along the crystallographic a-axis or [100] direction. With increasing PSMA concentration, the diameter of BaCO₃ whiskers slightly decreases due to capping effect.Secondly, monodispersed peanut-shaped mesoporous SrSO₄ particles were synthesized using PSMA as an additive at ambient temperature. The as-obtained SrSO₄ particles in the presence of 2 g L^-1 PSMA appear monodisperse and peanut -shaped. The average length and aspect ratio of the particles are about 2μm and 2, respectively. The as-prepared SrSO₄ particles have a relatively large BET specific surface area and mesoporous structure with an average pore size of about 2.9 nm. A preliminary evolution and formation mechanism has been proposed to account for the formation of monodispersed peanut-shaped mesoporous celestine particles.Thirdly, flower-shaped BaCrO₄ crystals have been synthesized via a facile polymer-mediated crystallization process at ambient temperature. A possible formation process have been proposed accounting for the formation of BaCrO₄ flowerFourthly, monoclinic PbCrO₄ nanorods, with a rectangular cross section, a typical length of 6 to 7μm, a width of 80-150 nm, and a width-to-thickness ratio of 2-5, have been successfully synthesized via a simple precipitation reaction, followed by a hydrothermal treatment without using any templates and additives. It was found that the length of as-obtained PbCrO₄ nanorods relies on the pH value and the aging temperature, and the optical properties of PbCrO₄ nanorods depend on their length. The intensities of UV- visible absorbance of PbCrO₄ nanorods slightly decrease with increasing the length of nanorods. On the contrary, the intensities of room-temperature photoluminescence of PbCrO₄ nanorods increase with increasing the length of nanorods.Fifthly, Calcium carbonate microspheres with different surface structures were successfully prepared by the precipitation reaction of sodium carbonate with calcium chloride in the presence of deoxyribonnucleic acid (DNA) at room temperature. The surface morphology or texture of CaCO₃ microspheres can easily be adjusted by varying the concentration of DNA or the wt ratio of DNA to CaCO₃. A critical implication was that DNA molecules could mediate the nucleation and growth of the inorganic phase and probably induce biomineralization in the biological system. This research may provide new insight into the control of morphologies of calcium carbonate and the biomimetic synthesis of novel inorganic materials.Sixtly, monodispersed cubic calcium carbonate composite particles were prepared by the precipitation reaction using polyacrylic acid (PAA) as an additive at 60-80℃. It was found that variations in the concentration of PAA and CaCO₃, molar ratio of PAA to CaCO₃, and pH and temperature of solution drastically changed the morphology of the as-produced CaCO₃ particles, but all the products obtained consisted of calcite crystals. The optimal experimental conditions for the production of cubic calcite particles were determined. The amount of PAA in the cubic calcite composite particles was about 1.4%.Finally, pure calcite crystal with different morphologies such as wood-block and spherical aggregates were prepared by a precipitation reaction in the presence of citric acid. The results showed that citric acid obviously influenced the formation of precipitates and the morphology of final products. The formation mechanism of wood-block-like particles was proposed according to theoretical deduction and the proposed growth mode.