Study On Fabrication Of Low-Dimensional Inorganic Nanomaterials By Templating Method

Low-dimensional (LD) semiconductor nanostructured materials have extremely important potential applications in nano-electronics, nano-optics and light integrated circuit in the future. Therefore, considerable attentions have been devoted to the fabrication of LD semiconductor nanostructured materials. Among strategies for the fabrication of LD semiconductor nanostructured materials, template-mediated techniques have been demonstrated to be very effective. For example, anodic aluminum oxide (AAO) is an important "hard" template. Various size nanotubles/nanowires have been fabricated through AAO templates with different pore diameter. Self-assemblies of surfactant are another kinds of important "soft" template, in particular, in the fabrication of mesoporous nanoparticles and mesoporous film materials, various nanostructured materials with different pore framework and pore size can be synthesized by varying electric charge and length of organic molecule as well as reaction conditions.This thesis was focused on the fabrication of LD semiconductor nanostructured materials via templating process. The main results are summarized as follows:1. The bamboo-shaped TiO₂ nanotubes with diameters of ca. 100 nm have been fabricated in nanochannels of AAO membranes by uprightly dipping the AAO membranes into sol of titanium isopropoxide (TIPO). TiO₂ layers compart the bamboo-shaped nanotubes, transect the hollow regions at intervals ranged from 80 to 300 nm. The bamboo-shaped TiO₂ nanotubes is anatase. The formation of bamboo-shaped morphologies appears to be independent of the precursor kinds, but to be closely connected with the dipping manner.2. CdS has extensive applications in the nonlinear optical materials, light-emitting diodes, solar cells, electronic and optoelectronic devices due to its typical wide band gap (2.42 eV) II-VI semiconductor property. CdS nanotubes with 60 urn in length and 100 nm in outer diameter were fabricated in AAO membrane by using N-(2-aminoethyl)-3-aminopropyltri- methoxysilane (AEAPTMOS) as 'molecular anchor' and cadmium chloride (2CdCl₂.5H₂O) as precursor.3. Mesoporous titania nanoparticles with high specific surface area and thermal stable anatase wall were synthesized from surfactant laurylamine hydrochloride (LAHC) and inorganic precursor Ti(SO₄)₂. The obtained mesoporous TiO₂ nanoparticles have mean diameter of 25.5 nm.The obtained anatase mesoporous TiO₂ nanoparticles showrelative high thermal stability. What is more, the phase transformation temperature of rutile is enhanced about 300 °C. The specific surface area of the mesoporous nanosized Ti(>2 calcined at 400 °C exceeded 189 m2/g, and that of the samples after calcinations at 500 °C still have 151 m2/g. The pore size distribution determined from BJH desorption isotherm for the sample calcined at 400 °C show a bimodal pore size distributions consist of smaller fine (2.0-5.5 nm) intra-particle pores and larger (8-20 nm) inter-particle pores. The 2.0-5.5 nm intra-particle pore size distribution centered 3.3 nm. The sample calcined at 500°C still maintains relatively narrow intra-particle pore size distribution (2.0-7.5 nm) centered 3.7 nm.4. Recently, the synthesis of AI2O3 nanoparticles has been widely investigated. However, there are a few reports on the fabrication of AI2O3 micro/nanotubes. In this thesis, we report the preliminary results on the preparation of AI2O3 gel microtubes using ammonium tartrate crystal as template in sol-gel process. The microtubules have ca.60⁶00 urn in lengths, 2-16 urn in outer diameter with most frequent ones around 4-8 urn and 0.2-3 urn in wall thickness. The vast majorities of the tubules have morphology of cylindrical structures and open-ended structure. The gel was partially transformed to Y-AI2O3 around 600 °C, further calcinations at 1100 °C, resulting in total phase transformation of CI-AI2O3. Upon calcinations at 800 °C for 5 h, the samples show a similar behavior in isotherm and pore size distribution, and still have relative high surface area of 188 m /g and pore volume of 0.61 cm3/g, implying the mesoporous structures have relatively high thermal stability.