With Different Morphologies Of Nanomaterials Synthesis And Study Of The Nature Of The Optical, Magnetic,

Nanomaterials have become the focus of considerable interest because they canshow novel properties which are superior to or different from the corresponding bulkmaterials. Research shows that the properties of nanomaterials depend on theirmorphology. So the development of reproducible and reliable methods to produceuniform and stable nanomaterials with different morphology is of significance forexploring their novel physical and chemical properties as well as the potentialapplications. In this thesis, the hydrothermal technique was developed. A series ofnanomaterials with different morphology were synthesized with simple new methods.Compared to conventional organic dyes, sufficiently passivated QDs appear to beless susceptible to photobleaching with much narrower emission spectra, which havebeen successfully used as fluorescent probes in imaging of biological samples andcells. Nanostructured semiconductor materials with unique optical properties havegenerated great research interest in the past two decades. Most attention has been paidto quantum dots (QDs). Owing to the quite different quantum confinement energies,one-dimensional (1D) nanostructures present some novel optical properties differentfrom zero-dimensional nanostructures. However, exploration of water soluble 1Dsemiconductor materials as fluorescent sensors for biological samples and cellsremains at a very early stage. This is partially due to the difficulties with thedispersion of these nanomaterials in water.There are five charpters in this dissertation:Charpter one: A review on the property and application of nanomaterials withdifferent morphology. The hydrothermal technology was described . Additionally, thesynthesis, property and application of one-dimensional semiconductor nanomaterialswere briefly discussed.Charpter two: Ddandelion-like three-dimensional β-MnO2 microstructures weresynthesized through the direct hydrothermal reaction between manganese nitrate andhydrogen peroxide. The formation mechanism of the dandelion-like microstructureswas investigated and discussed based on the experimental results. Magneticmeasurements showed that the Néel temperature of the as-obtained product was 100K,which was about 6K higher than that of the corresponding bulk β-MnO2 crystals.Charpter three: β-MnO2 single crystalline nanorods were synthesized employinga simple in-situ redox precipitation hydrothermal process. This was a good method forthe selected-control synthesis of β-MnO2. The effects of various experimentalconditions on the morphology of the products were investigated. The formationmechanism of the nanorods was investigated and discussed based on the experimentalresults. The magnetic measurement of the nanorods indicated that the Néel magnetictransition temperature was about 4K higher than that of the bulk β-MnO2 crystal.Charpter four: α-FeOOH nanorods were synthesized via a low-temperaturehydrothermal method. Transmission electron microscopy images taken at differenthydrothermal reaction times showed that the formation of the nanorods follows the"rolling-broken-growth" process. After calcined the as-synthesized α-FeOOH at250oC for 2h, α-Fe2O3 nanorods could be obtained. Very interestingly, the as-obtainedα-Fe2O3 nanorods exhibited interesting magnetic properties which were anomalouscompared to the corresponding bulk α-Fe2O3 material.Charpter five: The synthesis of water-soluble one-dimensional CdSenanomaterials was tentatively explored by using L-cystein and polyphosphate sodiumas capping agents.