Quantitative Etching Of The Anodic Aluminum Oxide Template And In The Preparation Of Metal Nanowire Arrays

One-dimension nanostructural materials including nanowires, nanotubes haveattracted considerable interest in recent years due to their unique optical, magnetic,electronic and chemical properties. In this thesis, based on lots of searching and analyzingliterature, several kinds of metal nanowires with different aspect ratios are attained viaelectrochemical deposition technique using Anodic Aluminum Oxide (AAO) membrane(diameter 200 nm) as template. Well ordered nanowire arrays with controllable length are madefrom quantificational etching of AAO template. Polymer nanotubes with small porediameter (80 nm) are fabricated by simple physical techniques with polymer solution. Themain results of this thesis are described as follows:1. Quantificational etching of AAO templateThe synthesis of nanomaterials with controllable compositions, structures anddimensionalities is very important for the application of nanomaterials. This problem canbe well resolved by combining electrodeposition and quantificational etching of AAOtemplate. Ni nanowires are prepared by electrodepositing Ni into porous anodizedaluminum oxide (AAO) template with nanosized pores. And then well ordered Ninanowire arrays with controllable length are made from partial removal of AAO inmixture of phosphoric acid and chromic acid (6 wt% H₃PO₄:1.8 wt% H₃CrO₄). Theimages of Ni nanowire arrays are obtained by scanning electron microscope (SEM) andtransmission electron microscope (TEM), respectively. Selected area electron diffraction(SAED) are employed to study the crystalline morphology ofNi nanowire arrays. Also,the relations between the etching time and the mass reduction of AAO template, thelength of Ni nanowire arrays are discussed. The results indicate that mixture ofphosphoric acid and chromic acid is a more mild and effective etchant compared withNaOH aqueous solution. When using mixture of phosphoric acid and chromic acid asetchant, the length of nanowires exposed from template can be accurately controlledthrough controlling etching time. This etching method is generally applicable for manyone-dimensional nanoarrays prepared from AAO template-assisted synthesis.2. Metal nanowiresCu, Ag, Ru nanowires have been prepared by electrodepositing method. Their images andcrystalline morphology are obtained by SEM, TEM and SAED. The results show that electrochemicaltemplate method is very feasible and general to fabricate metal nanowires.(1) Cu and Ru nanowires have been prepared by electrochemical template method in AAO template from a composite electrolyte solution. The columnar structure of thenanowires corresponds to the structure of the nano-scale pores of the templates, whichhave uniform diameter of approximate 200 nm. SAED reveals that Cu and Ru nanowireshave polycrystalline structure.(2) Direct current electrodeposition has been applied to fabricate Ag nanowireswithin the pores of AAO templates. The images of Ag nanowire arrays are obtained by SEMand TEM. The relationship between the nanowires length and electrodeposition time is discussed.Their growth speed is about 5μm/h. These nanowires have uniform diameter of approximate 200 nm.SAED pattern reveals that the Ag nanowire has a potycrystatline structure.(3) The theory of fabricating metal nanowires using electrochemical templatesynthesis has been elementarily studied. The diffusion pattern to the porous nanoelectrodearray during the growth of nanowires and reaction rates of electrode has been discussed.3. Polymer nanotubePS nanotubes have been prepared by depositing a solution of polymer with generalmolecular weight into AAO template with smaller pore about 80 nm and their morphologywere characterized by SEM. The test results indicate that only polymer nanowires can beprepared and nanotubes cannot be gained when using 80 nm pore diameter AAO template,which is conflict with our former research. Meanwhile polymer nanowire arrays areprepared by wetting technique. We speculate that there is a critical template pore diameterwhen polymer solution in the AAO template is proper and invariant.