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Descriptions of the research plan
Title: Synthesis, Formation Mechanism, and Properties of Different Metal/Metal Nanostructures
Keywords: Multi-Shell Nanostructures, Ionic Liquids, Electrochemistry, Multi-Functionality,
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Porous Metal Materials, Low-Dimensionality, Green Chemistry Objectives: This program is to develop a novel method for fabricating heterogeneous or alloyed different metal/metal low-dimensional nanostructures, for example, multi-shell or porous Ag-Au nanowires, nanorods, and nanocubes using an ionic liquid as both the solvent and shape-inducing template. Synthesis of ionic liquids (ILs) with different alkyl chains and functional groups, as well as the formation of different metal/metal nanostructures with new properties are involved in this research plan. Alloyed or heterogeneous multi-shell nanostructures are generated by utilizing electrochemical (electroless) deposition or a simple galvanic replace
ment reaction in ILs. By controlling the size, shape, composition, crystal structure and surface properties of these structures, it enables us not only to uncover their intrinsic properties, but exploit their formation mechanism in ILs media, as well as their applications in catalysis, surface-enhanced Raman scattering (SERS), sensors, porous electrodes, etc. This green chemistry process also may be extended to synthesize other organic and inorganic nanostructures with novel properties, morphology and complex form. State-of-the-art
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Metal nanostructures have numerous applications as nanoscale building blocks, templates, and components in chemical and biological sensors, as well as electronic/optical devices, due to their interesting optical, catalytic and electrical properties that depend strongly on both size and shape. Over the past decade, impressive progress has been made towards the fairly good shape and size control of metal nanostructures [1][2]. For noble metals, more emphasis is placed on tuning the novel shape-dependent properties of these nanostructures in contrast to the size-dependency. A variety of metallic building blocks with unique properties have been synthe原神和光遇哪个好玩
sized including cubes [3][4], prisms [5], disks [6], and hollow nanostructures [7]. Currently the interests migrate to the synthesis and application of more complex structures with different metals, such as multi-shell and heterogeneous nanostructures having new properties[8][9], coupling a conception for optimizing preparative strategies in an environmentally benign system[10]. Therefore, besides creating novel nanostructures with unique properties, a problem arising from the utilization of volatile or poisonous organic solvents and additives is of much concern in view of cleaner technology throughout both industry and academia.
Most of the current shape selective synthesis of metal nanostructures that their optical properties are markedly affected by their shape and aspect ratio are centered either on a solid substrate by physical methods or in aqueous or organic media through chemical procedures [2]. For instance, complex and highly regular crystalline silver inukshuk architectures can be produced directly on a germanium surface through a simple galvanic displacement reaction that only three ingredients were required: silver nitrate, water, and germanium [11]. Despite these advancements, however, limited reports have been report
ed on how the particle morphology and dimensionality could be
regulated by the utilization of ILs[12].
Recently, environmentally benign room-temperature ionic liquids (RTILs) have received increasing attention worldwide due to their favorable properties including excellent thermal and chemical stability, good solubility characteristics, high ionic conductivity, negligible vapor pressure, nonflammability, relatively low viscosity, and a wide electrochemical window. This class of fluid materials contains complicated molecular interactions such as ionic interactions, hydrogen bonding, л-л interactions, and amphiphilic polarization, rendering various molecular structures from merely local orderness up to macroscopic thermo tropic or lyotropic liquid crystalline phases [13]. These advantages make them actively being employed as green solvents for organic chemical reactions, extraction and separation technologies, catalysis, solar cells, and electrochemical applications[14][15].
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In contrast to tremendous growth in R&D on application of ionic liquids to chemical proce
ssing, the use of RTILs in inorganic synthesis is still in its infancy. There have been only a few reports on the shape-and-dimension controlled formation, by using RTILs, of hollow TiO2 microspheres [16] and nanowires of palladium [17], gold nanosheets [12], tellurium nanowires [18], flower-like ZnO nanostructures [19], and CuCl nanoplatelets [20]. So far, alloyed metal structures, either spherical nanoparticles or nanocomposite films, have been generated in RTILs using electrochemical deposition of nanocrystalline metals such as Al-Fe, and Al-Mn alloys on different substrates [21]. However, formation of multi-shell or hollow nanostructures by controlling both the shape and dimension in RTILs has not yet appeared in literature, especially using an electrochemical approach. It is therefore proposed in this program that a new route to optically or catalytically tune the properties of complex metal/metal nanostructures through the control of shape anisotropy and surface morphology is established in RTILs using a green chemistry approach. The reasons we choose RTILs as reaction media are not only in the view of environment protection, but in the consideration of their diversiform molecular structures, which could be used as shape-inducing templates for the synthesis of new nanostructures. It is very u
热带雨林探险记作文nlikely that ILs will entirely replace organic solvents or aqueous systems or gas phase processes for the fabrication of inorganic matter. Nevertheless, ionic liquids with different functional groups may provide a means to fabricate nanostructures that are not otherwise available. The applicant has accumulated good backgrounds in shape-controlled synthesis and characterization of metal and semiconductor low-dimensional nanostructures with unique optical properties. A series of approaches have been used to fabricate Ag-SiO2, and Ag-TiO2 core-shell nanostructures and Ag-SiO2-TiO2 nanocomposite films. During the Ph.D program, novel soft sol and polymer-assisted methods have been developed to form metal and semiconductor nanorods and wires, such as silver and gold nanowires, CdS and ZnS nanowires and rods, as well as anisotropic metal nanocrystals, for example, silver nanoprisms, gold nanocubes, nanodisks, and so on [22][23]. At the same time, tuning the optical properties through the interaction of nanostructures with femtosecond laser pulses to control the size, shape or dimension in nanometer regime has also been investigated [24]. As for the institution to which the applicant is applying and the group of Professor XXXXXXX, equipments includi
ng TEM, SEM, UV-Vis-NIR absorption spectrometer and other emission spectrometer (static, time-resolved and temperature dependent), as well as the group    's excellent research experience in semiconductor
and metal nanomaterials [25][26] provide a sound foundation for the implementation of this
research plan, probably resulting in not only a better understanding of the utilization of RTILs in nanochemistry and electrochemistry, but creating new nanostructures, such as microporous Ag/Au multi-shell nanowires with promising applications in SERS, catalysis, etc.
A multidisciplinary approach and the planned activities
A multidisciplinary approach is designed in this proposal through integrating organic synthesis, electrochemistry, materials science and optoelectronics, aiming to fabricate different metal/metal multi-shell heterogeneous nanostructures including nanocubes, nan
orings, nanoplates, nanowires and nanotubes. This research plan covers three aspects: The first one is to create novel structures through the reduction of different metal precursors in RTILs using reducing agents or electrosynthetic processes. The second is to produce porous low dimensional metal nanostructures by etching with specific solutions (e.g. concentrated ammonia or hydrochloric acid) or using galvanic displacement reaction and electrochemical anodization. The third is to investigate the formation mechanism and properties of these nanomaterials.