| After billion's of years evolution and optimization, natural plants exhibit hierarchical anatomies and morphologies with multi-scale, dimension and component, which provides a lot of suggestion for the design and synthesis of materials from macro- to micro-scale. Thus, the concept of biomorphic materials, with the natural biological structures as templates, retaining their hierarchical anatomies while introducing new components and endowing the new materials new functions, was given rise.In the present work, different kinds of woods, cotton fiber and leaves of green plants are employed as the templates for the synthesis of Wood-biomorphic Cr2O3, Wood-biomorphic Mn2O3, Wood-biomorphic Ag/Al2O3, Cotton-biomorphic Ag/SiO2, Cotton-biomorphic Au/N-TiO2 and Leaf-biomorphic TiO2 through controlled synthesizing processes. A series of methods such as XRD, FESEM, TEM, OM, Digital-OM, LCSM, Nitrogen adsorption, SXAS, XPS, FTIR, UV-Vis and EPR are employed for the study and characterization of the components, morphologies, microstructures, nanopore structures, percentage composition and state of elements, light-absorbing properties and activity of photocatalysis. The conclusions are summarized as follows:1. Biomorphic Cr2O3, Mn2O3 and Al2O3 templated with different kinds of woods were synthesized with hierarchical porous structures. On the millimeter scale, biomorphic oxides templated with coniferous woods retain their pore structure of well-arranged square tracheids with uniformly distributed diameters while biomorphic oxides templated with deciduous woods retain their pore structure of randomly-arranged and shaped tracheids with widely distributed diameters. The calcination temperature plays the important role on the pore structures on nanoscale. With the elevation of the temperature, the surface area and pore volume decrease while the average pore diameter and connectivity increase. The biomorphic Ag/Al2O3 is also synthesized with Ag nanoparticles well controlled in the nanopores of the oxides whose size distribution match well with each other. The infrared transmission curves of biomorphic Cr2O3 and Mn2O3 undergo an overall collapse with the rise of calcination temperature. Biomorphic Ag/Al2O3 sees great enhancement of light absorption within visible range and SPR peaks whose intensity and position are influenced by size distributions of Ag nanoparticles and their interaction with oxide matrix.2. Biomorphic SiO2 and N-TiO2 templated with cotton fibers are synthesized through sol-gel process. The oxides are fibrous and hollow on micro-scale. The addition of surfactant increases the surface area of biomorphic SiO2 while the introduction of Et3N with controlled hydrolysis by acetylacetone realizes one-step doping of N into TiO2 templated with plants. The simple component (cellulose) of cotton fibers give rise to uniformly distributed nanopores on biomorphic oxides after calcination, 2-3nm for SiO2 and 4-5nm for N-TiO2. Biomorphic Ag/SiO2 and Au/N-TiO2 are synthesized with Ag and Au nanoparticles well controlled in the nanopores of the oxides whose size distribution match well with each other. The nanoparticles keep stable under high temperatures. Biomorphic Ag/Al2O3 and Au/N-TiO2 see great enhancement of light absorption within visible range and SPR effect. The dopant N stays in the interstitial position of TiO2 lattice, forming localized state and making the band gap absorption onset redshift from 380nm to 550nm.3. Five kinds of green leaves are employed for the synthesis of leaf-biomorphic TiO2. The resulting oxide retains well the hierarchical structure of original leaves from veins to nano-layered structure of thylakoids through the combination of ion exchange and sol-gel coating processes. During the synthesizing process, the biomorphic TiO2 is self-doped with N from the templates. The synergy of doping and structure enhance the light absorption within visible range by 8% to 20% compared with TiO2 without template, and make the band gap absorption onset redshift by 25nm to 100nm.
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