Research Of FeOOH Crystallization Behaviour In The Constrained Nanopores

The crystallization behavior of crystals in the confined microspace is different from that in the solution phase environment.It is of great significance to study the crystallization rules of crystals in the limited space for the synthesis of materials with specific morphologies,structures and functions.In vivo,biological minerals are usually formed in matrix networks,narrow channels or compartmentalized microenvironments,where solute diffusion rate and crystal growth,orientation or assembly are affected to some extent.Controlled by specific physical and chemical environment,crystals will grow according to biological functional requirements,which endow biological materials with exquisite structures and unique functions.Iron-containing biological minerals are a kind of very special biological hard tissue materials,which play the functions of supporting,cutting or magnetic navigation in the biological body.The wear resistance and corrosion resistance of such materials are dozens of times higher than that of human teeth.However,few studies have been conducted to simulate the organic matrix microenvironment in vivo and to explore the crystallization behavior of iron-bearing minerals in the restricted microenvironment.In this study,we were inspired by the principles of biomineralization and used the columnar nanopore diameter as a model limited micro-space to explore the growth and crystallization behavior of FeOOH in its interior,paying specially attention to its morphology,structure,orientation and crystallization state.The results were compared with solution phase to explore the specific growth rule of iron minerals in restricted microenvironment.The specific research conclusions are as follows:1)At room temperature,a variety of one-dimensional FeOOH nano-materials,including nanorods,nanowires and nanotubes,were synthesized in the nanopore diameter of the track etching film by means of gas phase diffusion.The results show that the pore size has an important effect on the morphology and structure of the synthesized crystal.FeOOH nanowires with high aspect ratio can be synthesized by reducing the pore size?¹25?.Due to the influence of crystallization kinetics,the smaller size of the nano-pore can well isolate the solution phase and stabilize the metastable?-FeOOH,and the content of?-FeOOH can reach 99%within the pore diameter of 50 nm.Solute diffusion in nano-channels is restricted and the crystallization process is obviously slower than that in solution phase.The crystallization state of crystals in different nano-spaces is also different.The synthesis of monocrystalline?-FeOOH is beneficial in small size nanopore?50 or 100 nm?,while the synthesis of?-FeOOH polycrystal is mainly in large size?200 nm?.The pore diameter of nanometer also has an important influence on the orientation of crystals.The orientation of crystals in different pore sizes is different,and the orientation of crystal growth in solution phase is obviously different.The characteristics of pore surface also affect the crystallization of internal crystals.Polycrystalline FeOOH is formed in the pore diameter?100 nm?of 4 multilayer films modified with?PAA/PAH?₄ while?PAH/PAA?₄ channels produce FeOOH monocrystals with a certain orientation.2)The valence state and anion type of iron have important influence on the morphology,structure and phase composition of the synthesized FeOOH nano-materials.If FeSO₄ is selected as the primary reactant,the crystals synthesized in the nano-pore diameter are mainly?-FeOOH nanowires or nanorods,within a small amount of?-FeOOH.Under FeCl₃ conditions,the synthesized samples were mainly polycrystalline?-FeOOH,and most of them were nanotubes in 100 and 200 nm channels,and some particle aggregates and nanorods in 50 nm pore diameter.Other reaction reagents,such as Fe₂?SO₄?₃,were selected,and the synthesized products were mostly amorphous nanorods within the limited pore diameter.The main reason for the formation of different phases of FeOOH is that during the mineralization process,crystal growth is affected by various iron sources and anions and goes through different crystallization processes.