Design, Synthesis And Applications Of Noble Metal Nanoparticles/1-dimensional Structure Nanocomposites

Nanocomposites have the excellent properties that conventional materials do not possess, such as special surface structures, magnetism, optics properties and stability. Because of the various kinds of nanocomposites and the unusual properties that composite nanoparticles own, the fabrication and functionalization of nanocomposites have become the focus of nanochemistry. In this thesis, we have creatively designed a series of novel, facile and "green" strategies toward architectures composited of noble metal nanoparticles and one-dimensional nanomaterials. Furthermore, according to the requirements of different application areas, as well as making well use of the properties of every composition, we have designed a series of original noble metal nanoparticles/one-dimensional material nanostructures. Also we have investigated the performances and potential applications of as-synthesized nanocompositions. The main contents and results of the work are as follows:1. Motivated by the urgent requirement of environment field and the significant function of ZnO in water disposal, we hope to fabricate a kind of nanocomposites based on one-dimensional ZnO and noble metal nanoparticles. If this nanocomposite possesses both properties of noble metal and one-dimensional nanomaterials, it can make full use of the function of ZnO in wastewater disposal, as well as offset its shortcomings, and increase the applied value of this nanocomposite. In light of this, we have designed a novel room temperature approach to grow gold nanoparticles onto ZnO nanorods in an aqueous solution. This method is aimed to achieve a facile synthesis of ZnO/noble metal heterostructure, featuring the capability to tailor both the spatial distribution and the loading of metal nanocrystals. Our investigations of its photocatalytic performance and the application in environment field show that, such ZnO nanorods/Au nanostructure exhibits a strong structure-induced enhancement of photocatalytic performance, such as complete catalysis-degradation Rhodamine B within 15 min, and removal about 91% of environmental persistent 4-chlorophenol from water after 300 min irradiation, which has significant applied values.2. Nanomaterials based on noble metallic nanoparticles and carbon nanotubes widely used as cathode electrocatalysts in fuel cell applications. However, how to deposit size- and loading-controlled noble metallic nanoparticles with special morphologies onto CNTs remains a challenge and is of primary importance to maximize and utilization efficiency of these materials. Based on the successful fabrication of Au/ZnO nanocomposite, we extend this synthesis strategy to fabricate the heterostructure with monodisperse, high-loading, single-crystal platinum and gold nanocubes and CNTs. The as-synthesized CNT-supported Pt nanocubes displayed excellent electrocatalytic activities towards the oxygen reduction reaction (ORR), such as positive potential of up to 0.5 V and high reduction current. In addition, we also demonstrate that the synthesis method we designed is versatile.3. As a result of the high electrocatalytic activities of the as-synthesized CNT-supported Pt nanocubes towards the oxygen reduction reaction (ORR), we intend to fabricate other CNT-supported noble metal particles that have special morphologies to further enhance electrocatalytic performance. We have directly grown ultrafine platinum nanorods on MWCNTs surfaces by designing a straightforward one-step approach at room temperature. This preparation approach does not require the use of seeds, templates, or undesirable surfactants which could block the active sites on the Pt nanoparticles surface. After testing their suitability as catalysts in PEMFCs, we find that the Pt nanorods/CNTs nanocomposite has an active surface area of about two orders in magnitude higher than the commercial Pt/C catalyst (0.5 mgPi cm"", E-TEK). And the Pt utilization of Pt nanorods/CNTs catalyst is 2371 mW mgpt-1, based upon the Pt loading (0.35 mgPt cm-2), which is substantially higher than commercial Pt/C catalyst (800 mW mgpt-1). Therefore, the Pt nanorods/CNTs catalyst exhibited a better performance than that of the commercial Pt/C catalyst.4. Iron oxide nanotube is a kind of representative one-dimensional magnetic nanomaterials. There are lots of reports about the synthetic methods of iron oxide nanotubes, while those means have high requirements on experimental conditions and instruments, such as hydrothermal and spattering methods. Furthermore, those methods don't have the capability to control the morphologies, sizes and yields of products. Those limitations will result in the difficulties to use the as-synthesized iron oxide nanotubes in the next researches of composition and application. We design to utilize the Kirkendall-type mass transport, coupled with interfacial reactions, to synthesize iron hydroxide and iron oxide nanotubes. Furthermore, the as-synthesized magnetite nanotubes are successfully used in contrast enhancement in magnetic resonance imaging. The MRJ experimental results show that the magnetite nanotubes afford better T2 negative contrasts for MRl than 20 nm magnetite nanoparticles both before and after incubating with -10 SKBR-3 cells. The next steps of loading noble metal nanoparticles and related applications are under investigation.