Template-assisted synthesis of nanomaterials

Fabricating nanostructures and tailoring their properties on the nanometer scales by conventional lithographic approaches are challenging. In particular, the creation of nanostructures with good alignment and uniform size, to enable and enhance desirable collective behaviors, is even more difficult. Such difficulties have compelled us to seek alternative approaches such as utilization of template methods to produce uniform nanostructures on the nanometer scale, and to form self-organized highly ordered arrays. Anodic aluminum oxide (AAO) template has a hexagonal array of pores which diameter can be readily controlled in the range of 25-200 nm with pore spacing from 50 to 400 nm. The surface structure, anodizing voltage, anodizing time all have significant impact on the structure of AAO and these influential factors were carefully discussed. An AAO template typically has a thick barrier layer at the bottom of its pores. If we electrodeposit nanostructures into the pores of AAO, high potentials are required for the tunneling of the electrons through the barrier layer. Several techniques were developed to solve this barrier layer problem including chemical etching methods and adjusting the anodizing voltage to reduce the barrier thickness. Utilizing an AC electrodeposition technique, metal, such as gold, nanoparticle arrays with diameters of 25 nm and 50 nm have been directly electrodeposited into the AAO templates. Frequency of the current was found to have strong influences on the pore-filled ratio. Metal nanowires have been electrodeposited into the AAO channels by a DC electrodepostion technique. Gold patterned AAO templates have been used to prepare ZnS nanowires via a hydrogen-assisted thermal evaporation approach. The nanowires grow aligned perpendicularly to the template, and their diameters resemble the pore size of the AAO template. Photoluminescence results show that these ZnS nanowires are able to support lasing action…


Chapter 1. Introduction
Chapter 2. Fabrication of anodic aluminum oxide (AAO) template
2.1 Formation mechanism of AAO
2.2 Experimental details of AAO fabrication
2.3 Influential factors for AAO formation
Chapter 3. Electrodeposition of nanostructures using AAO template
3.1 Barrier layer problems
3.2 DC electrodeposition of metal nanowires into AAO template
3.3 AC electrodeposition of gold particles into AAO template
Chapter 4. Thermal evaporation of nanowires onto AAO template
4.1 Background 4.2 Size controlled fabrication of aligned ZnS nanowires on AAO template
4.3 Characterization of ZnS nanowire arrays
4.4 Summery
Chapter 5. Other works
5.1 ZnS nanowires doped with Ag and their photoluminescent properties
5.2 Synthesis of CdSe quantum dots
5.3 Exploratory work for nanodevice

Author: Wang, Danbin

Source: City University of Hong Kong

Download URL 2: Visit Now

Leave a Comment