Controlled Synthesis And Self-Assembly Of Low-Dimensional Nanomaterials

The preparation of nano-materials is a great challenge in the fields of syntheticchemistry and materials science, because materials at the nano- and micro-scalelengths have unique structural, mechanical, electronic, and optical properties.Various nano- and micro devices were built up based on nanomaterials. To utilizeand optimize the chemical/physical properties of nano-scale materials, a number ofworkers have focused on the control of the size and/or shape of nanoparticles as wellas their self-assembly into ordered structures by developing effective synthetictechniques. We report an effective well-confined redox method to prepare high quality Agnanoparticles. Our strategy was based on a self-redox reaction which employedreductive [Na(H2O)2]0.25MoO3 bronze and oxidative ion-exchanged silver ions. Thisin situ redox, at certain temperatures, led to the formation of Ag nanoparticles withtunable size. A well-confined method for preparing high quality silver nanoparticleswas developed, in which the particle size was tunable from 3 to 10 nanometers. Inthis method, the Ag+ ions were first introduced into the layers of MoO3 byion-exchange, and then reduced to Ag metal at 330 oC in a nitrogen gas atmosphere. 106Jilin University Ph. D. Thesis AbstractThe aggregation of Ag atoms on the surface of the MoO3 substrate depended uponthe reaction time, the reaction temperature, as well as the well-confined redoxreaction. The product was characterized by XRD, XPS, TEM, TG-DTA and UV-visspectroscopy. On the other hand, high quality silver nanoparticles bounding on theMoO3 nanorod with a diameter of about 50 nm, and a length of ca. 1 μm on averagewere prepared under the hydrothermal conditions. The reaction principles are illustrated as follows: [Na(H2O)2]0.25MoO3 + Ag+ → [Ag(H2O)x]0.25MoO3 + Na+ [Ag(H2O)x]0.25MoO3 → Ag (nanoparticles)+ MoO3(substrate or nanorod) Silica nanotubes were synthesized from kaolin clay using surfactant intercalation,sulfuric acid and hydrothermal treatments. Tubular structures with open ends, aninner diameter of about 50 nm and an outer diameter of 80 nm, and a length of lessthan 1 μm on average. Followed this work, a gold nanoparticles was incorporated inand on the surface of the silica nanotubes to generate a nanotube templated by thesacrificial silica. Silica nanotubes were synthesized from kaolin clay using surfactantintercalation, sulfuric acid and hydrothermal treatments. Tubular structures with openends, an inner diameter of about 50 nm and an outer diameter of 80 nm, and a lengthof less than 1 μm on average. Directed self-assembly of nanoparticles into specific structures can providecontrolled fabrication of nanometer-sized building blocks with unique and usefulelectronic, optical, and magnetic properties. In general, ligand- or polymer-stabilizednanoparticles can self-assemble into two-dimensional arrays. On structured templates,two- or one-dimensional arrays of nanoparticles can be directed with particulararrangements. For example, hexagonal arrays of nanoparticles on a monolayer of 107Jilin University Ph. D. Thesis Abstractdiblock copolymer micelles and one-dimensional chains of nanoparticles onridgeand-valley structured carbon were demonstrated. Short-range self-assembledalloys of nanoparticles in two-dimensional arrays were also demonstrated. In thisthesis, we report a self-assembly of titania nanoparticles. The self-assemblepropensity of the controlled shape and size distribution titania nanoparticles makesthe particles oriented organization to ordered structures without substrate by ahydrolysis-hydrothermal route. The procedure offers the possibility of a generalizedapproach to the production of patterned organization of single and complex oxidenanoparticles with size and morphology tunable. Another topic is shape-controlled...