| In recent years, ordered nanostructure materials such as TiO2，ZnO，SnO，Al2O3，MnO2，V2O5etc., have drawn intensive research attention by specialists and scholars in many fields,owing to their excellent physical and chemical properties, and potential applications indye-sensitized solar cell, photocatalysis, photoelectric, optical sensing, photoinduction,biological medicine, high-density data storage, spintronic devices and so on. Therefore, thehigh efficiency, low cost and controllable synthesis strategies and routes of thesenanostructure materials will be the focus to the researchers. Meanwhile, improvement of theirphysical and chemical properties will be helpful for further applications in certain areas,which will promote the development of nanotechnology industrialization. On this occasion, akind of brand-new TiO2nanotube (TiNT) films with gradient pore diameter and ultrathin tubewall have been fabricated by simple and facile chemical and physical methods. Meanwhile,the morphology, structure, and growth mechanism of TiNT films have been investigated inthis paper. Furthermore, in situ hydrothermal synthesis of three-dimensional SrTiO3microscale superstructures (STOMSs) via temeplate-based methods have been studied. Theseas-synthesized STOMSs show substantial applications in photonic crystal due to their controllable morphology and size. Further study of STOMSs suggests that rare-earth elementsdoped3D STOMSs can be widely used in solar-driven photocatalytic water splitting afterbeing loaded with noble metal. Meanwhile, in situ hydrothermal synthesis of other orderednano-or microstructure materials have been synthesized, such as CaCO3，BaCO3etc. Thispaper focus on the following parts:(1) Fabrication and properties study of TiNT films with gradient pore diameter andultrathin tube wall. TiO2is one kinds of excellent N-type wide band semiconductor materialwith a typical band structure, including valence band (VB) and conduction band (CB), and theband gap of the anatase crystalline phase is3.2eV. TiO2shows relatively high reactivity andchemical stability under ultraviolet light, which means that photons with the wavelengthshorter than387.5nm (λ <387.5nm) can be absorbed on the surface of TiO2, and results inphotogenerated holes caused by electron transfer from VB to CB. Hence, these TiO2filmscould involve in a series of photochemical reactions due to their high oxidizability ofphotogenerated holes, and widely used in many fields such as heterogenous photocatalyticreactions and photocatalytic water-splitting for hydrogen production. In addition，the photovoltaic efficiency of TiO2films have promoted to12%due to their advantageous photoelectricconversion properties. Especially, the TiO2films are low in the manufacturing costs, which isonly amount to10%~20%of typical silicon solar cell. All the merits of TiO2films suggestthat this new material can rival the traditional solar cell materials. Even more, if the TiO2films are composed of nanotubes (TiNTs), more efficient dye-sensitized solar cell can beassembled while the tubes are filled with low-cost dye. Further study suggests that the thinnertube wall and the larger pore diameter are, the more molecules of the dye can be adsorbed,which will result in stronger photovoltaic current and higher photo voltaic efficiency. Basedon the synthetic process of TiO2films, especially the study of TiNT films, we have given out afast preparation technology by investigating different kinds of electrolyte systems undervariation of solution composition. In fast technology, highly ordered TiO2nanotubular array films have been prepared by two-step anodization under high field. The high anodizingcurrent densities lead to a high-speed film growth rate (0.40–1.00μmmin1), which is nearly16times faster than traditional fabrication of TiO2at low field. The thickness of tube wall andpore diameter can be adjusted by external electric field changes, varies of growth time andchanging the concentration of the solution. It was found that an annealing process of Ti foil isan effective approach to get a monodisperse and double-pass TiO2nanotubular film with agradient pore diameter and ultrathin tube wall (nearly10nm). A higher anodic voltage andlonger anodization time are beneficial to the formation of ultrathin tube walls. This newmethods can be used to fabricated many other kinds of nanostructure materials, whichenriches the growth process of nanofabrication.(2) In situ hydrothermal synthesis of three-dimensional SrTiO3microscale superstructures(STOMSs) and the study of their photonic crystal properties. TiNT films not only are used asprecursors to provide titanium ions but also act as skeletons and growing points. By adjustingthe composition of mother liquors, STOMSs with controllable dimension have beensynthesized under inducing impact of TiNT films, and multiple (five times) crystallizationprocess are necessary during the fabrication, which is thought to be the key procedure duringthis process. Further study indicates that the branches and trunks on these STOMSs showperfect corn-like structures, and each side of the trunks can be considered asgrating-analogous nanostructures. The well-ordered trunks along with gratings constitute3dimensional hybrid microstructures that contribute to light diffraction, and the colorfulphotonic effects originated from light diffraction are thought to be due to refractive indexmodulations in three dimensions. The colors of these STOMSs can be tuned from yellow tocyan by changing their growth cycle. This special optical performance can broaden theapplication scope of SrTiO3nano-or microstructure materials. Furthermore, SrTiO3, serves asa typical transition-metal oxides with perovskite structure, has a band gap of3.2eV, whichwill be used widely as high-activity semiconductor photocatalysis materials beyond TiO2. This method offers an easy way in fabricating other perovskite structure and carbonatematerials, which enriches the hydrothermal synthesis technology of nanofabrication.(3) Fabrication and properties study of other nanostructure materials, such as BaTiO3，CaTiO3，CaCO3，SrCO3. Metal oxides MTiO3(M=Ba，Sr，Ca) with perovskite structure,serves as one kinds of important materials in modern scientific study, are widely used in manybasic industry fields, owing to their superior performance in the area of optics, electricity,magnetism, biological and ceramic materials. In this chapter, fabrication of other perovskitematerials of BaTiO3, CaTiO3via hydrothermal synthesis are the focus of our researches. Themorphology of the preparation of micro/nanostructure MTiO3material under differentexperiment conditions have been studied, typical SEM images and Energy dispersive X-rayspectroscopy have been systematically researched on the as-obtained nanostructure MTiO3.SrCO3is widely used in magnetic materials, coatings, ceramic materials as one kind ofimportant chemical materials, while its applications are restricted by the morphology. Forexample, SrCO3powders are mainly used in solid reaction, SrCO3wires have strongreinforcement effect, and the sheets have higher ion active, which is easy reacted with TiO2toget SrTiO3with good dispersity. Hence, we can synthesize the products that best meet ourneeds by adjusting the synthetic route according to the demand of experiment and production.CaCO3serves as an excellent inorganic filler has also drawn much attention and been usedwidely in the modernization of industry such as coating, paper industry, rubber and plastic etc. |
PDF Full Text Request