| In recent years, hierarchical nanostructure has become an important research focus in field of materials, chemistry, catalysis, biomedicine, and related interdisciplinary fields due to its unique physical and chemical properties, such as controllable hierarchical nanostructure, large specific surface, open porous structure, and outstanding surface property. Among many hierarchical nanostructure materials, hollow nanospheres and three-dimensionally ordered macroporous (3DOM) materials have been widely applied in the fields of catalysis, separation, adsorption, and drug delivery and release due to their adjustable size and morphology, unique hollow structure, large specific surface area and pore volume, abundant void space, superior permeability, good biocompatibility, and unique light absorption and scattering property.In this dissertation, based on the advantages of the above mentioned hierarchical nanostructures, we intended to relationally design and construct:(1) novel single-shell and multi-shell hierarchical hollow nanospheres,(2) multi-shell graphene-based hierarchical hollow nanospheres, and (3) three dimensionally order hierarchical nanostructures and systematically explore the availability of these hierarchical nanostructures for applications in drug release and energy conversion catalysis.The first part of this dissertation covers the second, third, fourth, fifth, sixth chapters and focuses on the construction of novel single-shell and multi-shell hierarchical hollow nanospheres and exploration of their uses for drug release and catalysis.In the first part of this dissertation, firstly, we synthesized a series of hierarchical hollow nanospheres [(single-shell@CeO2, double-shell mesoporous@TiO2@TiO2,@CeO2@TiO2and@m-TiO2@m-SiO2spheres, and magneto-optical bi-functional multi-shell mesoporous nanospheres (Fe@m-SiO2@Y2O3:RE@m-SiO2, Fe@m-SiO2@SiO2@Y2O3:RE@m-SiO2, Fe@m-SiO2@Y2O3:RE, RE=Eu/Tb or Yb/Er)]. We investigated the loading and release property of these hollow hierarchical nanospheres for doxorubicin hydrochloride (DOX) and gentamicin sulphate (GS) and evaluated the effects of pH value and temperature on the performance of drug loading and release. The magneto-optical bi-functional multi-shell hollow Fe@m-SiO2@Y2O3:RE@m-SiO2(RE=Eu, Tb or Yb/Er) nanospheres show outstanding drug loading and release property, which represents great prospect for their use in drug loading and release due to their superior magneto-optical bi-functional features and the excellent performance of drug loading and release.In the first part of this dissertation, secondly, we constructed, for the first time, hierarchical hollow@M/CeO2microspheres with uniform particle size, good monodispersibility, unique hierarchical structure, and noble metal loading on the inner wall of microspheres. The catalytic performance of hierarchical hollow@M/CeO2microspheres for the reduction of4-nitrophenol to4-aminophenol show that the hierarchical hollow nanospheres can enhance the confinement effect of reactants during the catalytic reaction, promote the synergistic effect between noble metal and CeO2support, and reduce the loss of active species, which make them display outstanding catalytic activity and stability.In the first part of this dissertation, thirdly, we reported the design and realization of a novel double-shell hierarchical hollow nanospheres (@CeO2/M@M/TiO2, M=Au or Pd). The hierarchical hollow nanospheres possess unique mesoporous walls and double independent cavities, which can enhance the synergistic effects between noble metal nanoparticles and metal oxide shells and effectively reduce the depletion of catalytic active species. In addition, the hollow and interlayer cavities in hierarchical hollow nanospheres can act as microreactors, providing the confinement effect for reactants and speeding up the catalytic reaction rate and increasing the catalytic stability. Therefore, the double-shell hierarchical hollow nanospheres with dual noble metal nanoparticles loaded display high catalytic activity and stability for the Suzuki-Miyaura coupling reaction, benzyl aerobic alcohol oxidation, and4-nitrophenol reduction reaction.In the first part of this dissertation, fourthly, we developed a universal method to synthesize three types of double-shell hierarchical hollow nanospheres. Owing to the variable synergistic effects between Pd nanoparticles and TiO2shells in hierarchical architectures, they exhibit remarkable variations in catalytic performance. In particular, the obtained yolk-double-shell Pd@TiO2/Pd@TiO2architecture creates two Pd-TiO2interfaces on the external and internal surfaces of the inner TiO2shell, leading to the strongest synergistic effect of Pd nanoparticles with TiO2shell. Meanwhile, the interlayer chamber between the double TiO2shells connecting with the central cavity of the hollow TiO2structure through the mesoporous TiO2wall forms a nanoreactor for enriching the reactants and preventing the deletion of Pd nanoparticles during the reaction, thus greatly accelerating the reaction speed. Owing to its structural features, yolk-double-shell Pd@TiO2/Pd@TiO2architecture exhibits extremely high catalytic performance on the Suzuki-Miyaura coupling reaction and the reduction of4-nitrophenol reaction.In the first part of this dissertation, finally, we designed a novel mesoporous ’shell-in-shell" hierarchical hollow nanospheres (@Pd/m-TiO2/Pd@m-SiO2). The "shell-in-shell" hierarchical hollow nanospheres is composed of mesoporous double TiO2and SiO2shells with the ultrafine Pd nanoparticles (PNPs) uniformly distributed on the external and internal surfaces of the meso-TiO2shell. Such a structural configuration endows the nanospheres with large surface area due to the mesoporous shells, enhanced synergy between PNPs and the TiO2shell, and independent chambers formed by two shells. Ultimately, the "shell-in-shell" hierarchical hollow nanospheres, which is used as an effective nanoreactor, exhibits improved catalytic activity and selectivity for Suzuki-Miyaura coupling reaction and high catalytic activity and stability for4-nitrophenol reduction reaction. Unexpectedly, depending on the restriction of mesopores of the outer m-SiO2shell on reactant molecules with specific structure and size, the catalytic selectivity for Suzuki-Miyaura coupling is successfully realized.The second part of this dissertation covers the seventh chapter and invovles the construction and catalytic performane of multi-shell graphene-based hierarchical hollow nanospheres.In the second part of this dissertation, we successfully constructed multi-shell graphene-based hierarchical hollow nanospheres (SiO2@SnO2@RGO/Pt@m-SiO2) for the first time. The unique architecture can form a well-defined double-point junction (SnO2-RGO-Pt), which can greatly enhance the ability of vectorial and irreversible electron transfer of SnO2â†'GOâ†'Pt and effectively prevent Pt nanocrystals from aggregation and leaching during the reaction. We unexpectedly achieved the photocatalytic water splitting to generate H2for the first time over this hierarchical SiO2@SnO2@RGO/Pt@m-SiO2nanosphere. Meanwhile, the hierarchical nanosphere displays the excellent catalytic activity and stability for the photocatalysis of H2evolution reaction and the reduction reaction of4-nitrophenol to4-aminophenol.The third part of this dissertation covers the eighth and ninth chapters and emphasized on the creation and catalytic performance of three-dimensionally ordered macroporous (3DOM) hierarchical nanomaterials.In the third part of this dissertation, firstly,3DOM hierarchical Pt/CeO2-Co3O4nanostructures with well-defined macroporous skeletons and mesoporous walls were fabricated. The obtained3DOM hierarchical nanostructures possess connected macropores, adjustable chemical compositions, and varied surface elemetal states, and homogenously distributed ultrafine Pt nanoparticles. Compared with traditional non-porous powder catalysts, the3DOM Pt/CeO2-Co3O4nanostructures show superior catalytic performance for CO preferential oxidation in H2-rich gases due to the strong interaction between different valence states of Pt,CeO2and Co3O4, which may enhance their redox ability. Meanwhile, the existence of macro-and mesoporous structure in Pt/CeO2-Co3O4nanostructures is conducive to the diffusion of reactants and products, which may promote the catalytic activity and stability in CO PROX reaction. The3DOM hierarchical Pt/CeO2-Co3O4nanostructures show great potentials for use in in polymer electrolyte membrane fuel cells.In the third part of this dissertation, secondly, noble metal nanoparticles supported hierarchical3DOM Pt/TiO2nanostructures were synthesized. The photocatalysis of water splitting to generate H2on hierarchical3DOM Pt/TiO2nanostructures was systematically studied. It is revealed that under simulated sunlight (AM1.5), hierarchical3DOM Pt/TiO2nanostructures show outstanding photocatalytic performance of water splitting to generate H2. Meanwhile, hierarchical3DOM Pt/TiO2nanostructures possess excellent catalytic stability, and no obvious reduce of catalytic activity can be observed even after long times catalytic running. Thus, hierarchical3DOM Pt/TiO2nanostructures possess great potentials for their application in photocatalytic water splitting to generate H2. |
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