Nanomaterials With Multi-Dimensional Morphologies And Structures: Synthesis, Characterization And Bioanalysis Applications

Recently, nanostructured materials have attracted much attention because of their novel optical, electrical, magnetic and catalytic properties, and their technical applications in diverse areas such as the magnetic storage, devices, sensors, medicine images and catalysis. In the present dissertation, several novel functional composite nanostructures were designed and constructed, and the structures and properties of these nanostructures were detailed studied. By means of the developed-hydrothermal/solvothermal method and polyol-mediated process, we have succeeded in developing new structured nanomaterials with the delicate control of their morphologies, structures and properties, and consequently bridging the gap between the functional nanostructures and the nanodevices.The developed-hydrothermal/solvothermal method and polyol-mediated process to achieve several semiconductor oxides with multi-morphologies and structures, and properties and their applications of these nanostructures were detailed studied. The main point of this dissertation is as followed:1. A 3D ZnO nanostructure with sisal-like morphology has been synthesized in the temperature range 120–220℃by a rapid hydrothermal route (30 min) via the assembly of CTA⁺ and Zn(OH)₄^2-. The obtained samples are hexagonal wurtzite structures and they exhibit special optical properties with a red-shift of about 20 nm compared to the corresponding nanorods and nanowires. The sisal, constructed of many nanorods, possesses typical tapering features with tip size 80–100 nm. The effects of CTAB, NaOH, reaction time and temperature were investigated. Results show that the concentration of CTAB and Zn²⁺/OH^- molar ratio play important roles in the fabrication of uniform and pure ZnO samples. On the basis of structural information provided by XRD, SEM, TEM, and HRTEM, a growth mechanism is proposed for the formation of sisal-like 3D ZnO nanostructures.2. One-dimensional (1D) hierarchical nanostructures of ultralong layered K_xMnO₂ (x < 0.3) bundles with diameters 50-100 nm and lengths up to 50-100μm have been successfully prepared by a PEG-assisted hydrothermal method based on the reaction of KMnO4 with 2-ethylhexanol. The obtained samples ascribe to the monoclinic phase and exhibit ferromagnetic behaviors below 32 K and paramagnetic behaviors above 32 K, which may make this system a promising base material for magnetic devices. A series of contrastive experiments have illustrated that 2-ethylhexanol, PEG 400, KOH, and reaction time play an important role in the synthesis of the nanobundles. A possible growth mechanism has been proposed.3. A redox in polyol process was developed to synthesize CeO₂ with controllable superstructures. At the different stages of the reaction, the prepared CeO₂ were readily regulated in its morphologies, which could vary from (2D) nanodisks to (0D) hierarchically nanoporpous nanoparticles (HNPNPs), and finally to 3D spherical arrays. The growth kinetics of such a process was also studied. The synthesized CeO₂ HNPNPs exhibited high surface area and high catalytic activity as a catalysis for CO oxidation.4. In the present work, we just make use of the novel properties of CeO₂ HNPNPs as peroxidase mimetics to detect H₂O₂ and glucose. The CeO₂ HNPNPs were prepared via a polyol-mediated process. The as-prepared CeO₂ HNPNPs were then used to catalyze the oxidation of a peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by H2O₂ to the oxidized colored product which provides a colorimetric detection of H2O₂. A slow as5x10-9 mol/L H₂O₂ could be detected via our method. More importantly, a sensitive and selective analytical platform for glucose detection was fabricated using glucose oxidase (GOx) and the as-prepared CeO₂ HNPNPs. The analytical platform developed exhibited sensitive and selective detection of glucose with a linear range from 1×10^-6 to 1×10^-4 mol/L.5. One-dimensional Single-Crystalline Magnetite (Fe3O4) Nanobelts with diameters 50 nm and lengths up to 3-5μm have been successfully prepared by a PVP-assisted hydrothermal/solovthermal method. The obtained samples exhibit ferromagnetic behaviors at 300 K, which may make this system a promising base material for magnetic devices. A series of contrastive experiments have illustrated that carbon chain length, PVP K30, and reaction time play an important role in the synthesis of the nanobelts. A possible growth mechanism has been proposed. Furthermore, we just make use of the novel properties of Fe3O4 nanobelts as peroxidase mimetics reported by Yan et al. to detect H2O2 and glucose. The as-prepared Fe3O4 nanobelts were then used to catalyze the oxidation of a peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 to the oxidized colored product which provides a colorimetric detection of H2O2. As low as 2x10^-7 mol/L H₂O₂ could be detected with a linear range from 5x 10^-7 to 1x 10^-5 mol/L via our method. More importantly, a sensitive and selective analytical platform for glucose detection was fabricated using glucose oxidase (GOx) and the as-prepared Fe3O4 nanobelts. The analytical platform developed exhibited sensitive and selective detection of glucose with a linear range from 1×10^-5 to 1×10^-3 mol/L.6. We have used FeSO₄·2H₂O, Sodium borohydride. ,two nontoxic and inexpensive reagents, to synthesize Fe₃O₄ single-crystalline nanobelts bundles with uniform, self-assembled, bundlelike nanostructures by a PVP-assisted hydrothermal/solvthermal method.γ-Fe₂O₃,α-Fe₂O₃, could be obtained from Fe₃O₄ without changing their morphologies by a simple calcination procedure. The reaction mechanism and the self-assembly evolution process were studied. The addition of isononanol played a critical role in the synthesis of Fe₃O₄ single-crystalline nanobelts bundles. The as-prepared iron oxide nanomaterials showed an excellent ability to remove pollutants in water treatment and are expected to be useful in many other applications.