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1.
The microstructure (composition, size and shape etc.) of semiconductor nanocrystals determine the electronic density of states of semiconductor nanomaterials and ultimately determine their optical and electrical properties. Semiconductor nanocrystal advanced structures, such as hybrid nanostructures and nanocrystal superlattices, not only integrate the function of individual nanocrystals, but also brings the materials collective and synchronic properties. How to control the monodispersity, composition and structure of as-prepared semiconductor nanocrystals during their syntheses, as well as their furthermore assembly, has been a hot research area in this decade. This critical review focuses on the development of synthetic and assembly methods (techniques) of semiconductor nanocrystals processed in the liquid phase. Emphasis is on the synthesis methodology, microstructure related properties of semiconductor nanocrystals, and their applications (243 references). 相似文献
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晶核作为晶体生长过程中新相形成的开始,理解它们的性质和行为特点对纳米材料的控制合成有重要指导意义,尤其对形貌和尺寸的调控。可控合成的超小尺寸纳米晶(<5 nm)为研究晶核的性质提供了一个理想模型。本文基于纳米晶核在纳米材料控制合成中的研究进展,论述了晶核的尺寸与表面结构对纳米材料生长与组装模式的影响,尤其是基于纳米晶核预组装途径的晶体生长模式。 相似文献
3.
Assembly of nanoparticles is a promising route to fabricate devices from nanomaterials. Colloidal crystals are well-defined three-dimensional assemblies of nanoparticles with long-range ordered structures and crystalline symmetries. Here, we use a solvent evaporation induced assembly method to obtain colloidal crystals composed of polyhedral sodium rare earth fluoride nanoparticles. The building blocks exhibit the same crystalline orientation in each colloidal crystal as indicated in electron diffraction patterns. The driving force of the oriented assembly is ascribed to the facet-selected capping of oleic acid molecules on {110} facets of the nanoparticles, and the favorable coordination behavior of OA molecules is explained by the steric hindrance determined adsorption based on the studies of the surface atomic structure of nanocrystals and molecular mechanics simulation of OA molecules. The capping ligands also provide hydrophobic interactions between nanoparticles and further direct the oriented assembly process to construct a face-centered cubic structure. These results not only provide a new type of building block for colloidal crystals, but also clarify the important role of surface ligands, which determine the packed structure and orientations of nanoparticles in the assemblies. 相似文献
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A homogeneous and disordered assembly of densely packed nanocrystals 2-3 nm in size was synthesized at room temperature in an aqueous solution without the assistance of any organic molecules. The assembled nanocrystals of titanium oxides, such as anatase titanium dioxide, sodium titanate, and a solid solution with rutile tin dioxide, formed macroscopic transparent objects 2-5 mm in size. In general, it is not easy to obtain homogeneous and disordered assembly of nanocrystals without assistance of any organic molecules for the inhibition of inhomogeneous and disordered aggregation. In the present work, the formation of the hydrated layer on the surface of nanocrystals facilitated the homogeneous and disordered assembly. The crystal phases and the compositions of the nanocrystals were controlled by the tuning of the synthetic conditions, such as the initial pH and metal source concentration. Based on the formation processes and mechanisms, this approach for the coupled synthesis and assembly can be applied to a variety of nanomaterials for preparation of homogeneous but disordered assembly. 相似文献
6.
The properties of nanomaterials for use in catalytic and energy storage applications strongly depends on the nature of their surfaces. Nanocrystals with high surface energy have an open surface structure and possess a high density of low-coordinated step and kink atoms. Possession of such features can lead to exceptional catalytic properties. The current barrier for widespread industrial use is found in the difficulty to synthesise nanocrystals with high-energy surfaces. In this critical review we present a review of the progress made for producing shape-controlled synthesis of nanomaterials of high surface energy using electrochemical and wet chemistry techniques. Important nanomaterials such as nanocrystal catalysts based on Pt, Pd, Au and Fe, metal oxides TiO(2) and SnO(2), as well as lithium Mn-rich metal oxides are covered. Emphasis of current applications in electrocatalysis, photocatalysis, gas sensor and lithium ion batteries are extensively discussed. Finally, a future synopsis about emerging applications is given (139 references). 相似文献
7.
Ceria (CeO(2)) is a technologically important rare earth material because of its unique properties and various engineering and biological applications. A facile and rapid method has been developed to prepare ceria nanoparticles using microwave with the average size 7 nm in the presence of a set of ionic liquids based on the bis (trifluoromethylsulfonyl) imide anion and different cations of 1-alkyl-3-methyl-imidazolium. The structural features and optical properties of the nanoparticles were determined in depth with X-ray powder diffraction, transmission electron microscope, N(2) adsorption-desorption technique, dynamic light scattering (DLS) analysis, FTIR spectroscopy, Raman spectroscopy, UV-vis absorption spectroscopy, and Diffuse reflectance spectroscopy. The energy band gap measurements of nanoparticles of ceria have been carried out by UV-visible absorption spectroscopy and diffuse reflectance spectroscopy. The surface charge properties of colloidal ceria dispersions in ethylene glycol have been also studied. To the best of our knowledge, this is the first report on using this type of ionic liquids in ceria nanoparticle synthesis. 相似文献
8.
Junchao Chen Xin-Ping Wu Michael A. Hope Zhiye Lin Lei Zhu Yujie Wen Yixiao Zhang Tian Qin Jia Wang Tao Liu Xifeng Xia Di Wu Xue-Qing Gong Weiping Tang Weiping Ding Xi Liu Liwei Chen Clare P. Grey Luming Peng 《Chemical science》2022,13(37):11083
Determining the different surfaces of oxide nanocrystals is key in developing structure–property relations. In many cases, only surface geometry is considered while ignoring the influence of surroundings, such as ubiquitous water on the surface. Here we apply 17O solid-state NMR spectroscopy to explore the facet differences of morphology-controlled ceria nanocrystals considering both geometry and water adsorption. Tri-coordinated oxygen ions at the 1st layer of ceria (111), (110), and (100) facets exhibit distinct 17O NMR shifts at dry surfaces while these 17O NMR parameters vary in the presence of water, indicating its non-negligible effects on the oxide surface. Thus, the interaction between water and oxide surfaces and its impact on the chemical environment should be considered in future studies, and solid-state NMR spectroscopy is a sensitive approach for obtaining such information. The work provides new insights into elucidating the surface chemistry of oxide nanomaterials.Both atomic geometry and the influence of surroundings (e.g., exogenously coordinated water) are key issues for determining the chemical environment of oxide surfaces, whereas the latter is usually ignored and should be considered in future studies. 相似文献
9.
Baghbanzadeh M Carbone L Cozzoli PD Kappe CO 《Angewandte Chemie (International ed. in English)》2011,50(48):11312-11359
Colloidal inorganic nanocrystals stand out as an important class of advanced nanomaterials owing to the flexibility with which their physical-chemical properties can be controlled through size, shape, and compositional engineering in the synthesis stage and the versatility with which they can be implemented into technological applications in fields as diverse as optoelectronics, energy conversion/production, catalysis, and biomedicine. The use of microwave irradiation as a non-classical energy source has become increasingly popular in the preparation of nanocrystals (which generally involves complex and time-consuming processing of molecular precursors in the presence of solvents, ligands and/or surfactants at elevated temperatures). Similar to its now widespread use in organic chemistry, the efficiency of "microwave flash heating" in dramatically reducing overall processing times is one of the main advantages associated with this technique. This Review illustrates microwave-assisted methods that have been developed to synthesize colloidal inorganic nanocrystals and critically evaluates the specific roles that microwave irradiation may play in the formation of these nanomaterials. 相似文献
10.
Peter W. Roesky 《无机化学与普通化学杂志》2003,629(11):1881-1894
The amido metal chemistry of the rare earth elements is a rapid developing area in coordination chemistry. Especially bulky mono and bidentate amido and amidinates have been introduced as ligands in rare earth chemistry. Due to these sterically demanding ligands, the coordination numbers of the rare earth elements are significantly reduced. This article focuses on two of these bulky ligand systems: bis(trimethylsilyl)amide and aminotroponiminates. The homoleptic bis(trimethylsilyl)amides of rare earth elements, [Ln{N(SiMe3)2}3], are well established compounds in synthetic chemistry. Therefore, this article reviews recent progress in the catalytic application of these compounds. In the second part of this research report, it is shown that N, N′‐disubstituted aminotroponiminates and mono bridged bisaminotroponiminates can be used as cyclopentadienyl alternatives. Achiral and chiral aminotroponiminates have been used. The structural properties, reactivities as well as the catalytic and synthetic applications of the aminotroponiminates complexes will be outlined in this article. 相似文献
11.
Tiseanu C Parvulescu VI Boutonnet M Cojocaru B Primus PA Teodorescu CM Solans C Sanchez Dominguez M 《Physical chemistry chemical physics : PCCP》2011,13(38):17135-17145
Pure and europium (Eu(3+)) doped cerium dioxide (CeO(2)) nanocrystals have been synthesized by a novel oil-in-water microemulsion reaction method under soft conditions. In-situ X-ray diffraction and RAMAN spectroscopy, high-resolution transmission electron microscopy, UV/Vis diffuse-reflectance and Fourier transform infrared spectroscopy as well as time-resolved photoluminescence spectroscopy were used to characterize the nanaocrystals. The as-synthesized powders are nanocrystalline and have a narrow size distribution centered on 3 nm and high surface area of ~250 m(2) g(-1). Only a small fraction of the europium ions substitutes for the bulk, cubic Ce(4+) sites in the europium-doped ceria nanocrystals. Upon calcination up to 1000 °C, a remarkable high surface area of ~120 m(2) g(-1) is preserved whereas an enrichment of the surface Ce(4+) relative to Ce(3+) ions and relative strong europium emission with a lifetime of ~1.8 ms and FWHM as narrow as 10 cm(-1) are measured. Under excitation into the UV and visible spectral range, the europium doped ceria nanocrystals display a variable emission spanning the orange-red wavelengths. The tunable emission is explained by the heterogeneous distribution of the europium dopants within the ceria nanocrystals coupled with the progressive diffusion of the europium ions from the surface to the inner ceria sites and the selective participation of the ceria host to the emission sensitization. Effects of the bulk-doping and impregnation with europium on the ceria host structure and optical properties are also discussed. 相似文献
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Rao CN Vivekchand SR Biswas K Govindaraj A 《Dalton transactions (Cambridge, England : 2003)》2007,(34):3728-3749
Synthesis forms a vital aspect of the science of nanomaterials. In this context, chemical methods have proved to be more effective and versatile than physical methods and have therefore, been employed widely to synthesize a variety of nanomaterials, including zero-dimensional nanocrystals, one-dimensional nanowires and nanotubes as well as two-dimensional nanofilms and nanowalls. Chemical synthesis of inorganic nanomaterials has been pursued vigorously in the last few years and in this article we provide a perspective on the present status of the subject. The article includes a discussion of nanocrystals and nanowires of metals, oxides, chalcogenides and pnictides. In addition, inorganic nanotubes and nanowalls have been reviewed. Some aspects of core-shell particles, oriented attachment and the use of liquid-liquid interfaces are also presented. 相似文献
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Mengyuan Li Congli Wang Zhenghan Di Hui Li Jingfang Zhang Wenting Xue Meiping Zhao Ke Zhang Yuliang Zhao Lele Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1364-1368
Developing simple and general approaches for the synthesis of nanometer‐sized DNA materials with specific morphologies and functionalities is important for various applications. Herein, a novel approach for the synthesis of a new set of DNA‐based nanoarchitectures through coordination‐driven self‐assembly of FeII ions and DNA molecules is reported. By fine‐tuning the assembly, Fe–DNA nanospheres of precise sizes and controlled compositions can be produced. The hybrid nanoparticles can be tailored for delivery of functional DNA to cells in vitro and in vivo with enhanced biological function. This highlights the potential of metal ion coordination as a tool for directing the assembly of DNA architectures, which conceptualizes a new pathway to expand the repertoire of DNA‐based nanomaterials. This methodology will advance both the fields of DNA nanobiotechnology and metal–ligand coordination chemistry. 相似文献
15.
Borchert H Borchert Y Kaichev VV Prosvirin IP Alikina GM Lukashevich AI Zaikovskii VI Moroz EM Paukshtis EA Bukhtiyarov VI Sadykov VA 《The journal of physical chemistry. B》2005,109(43):20077-20086
Nanostructured ceria doped with other rare earth elements is a good oxygen ion conductor, which gives rise to various catalytic applications such as the construction of membranes for syngas production by partial oxidation of methane. This article focuses on the Gd-doped cerium dioxides, which can be modified with Pt or Pd to enhance the reactivity of the lattice oxygen in interaction with methane. The aim of the work is the elucidation of correlations between the structural, electronic, and chemical properties of these nanomaterials. Detailed studies were performed for a series of samples with and without surface modification by noble metals using a complex combination of physicochemical methods: XRD, TEM, CH(4) TPR, XPS, SIMS, and FTIR spectroscopy of adsorbed CO. XPS and TPR data revealed that surface modification with noble metals enhances the reducibility of the doped ceria support, where the effect is more pronounced for Pd than for Pt. The formation of highly cationic Pd species due to strong metal support interactions provides a possible explanation for this behavior. Furthermore, the results obtained in the present work for the Gd-doped ceria system are compared to those obtained previously for the Pr-doped ceria system. 相似文献
16.
Dr. Geoffroy Ferru Dr. Benjamin Reinhart Dr. Mrinal K. Bera Prof. Monica Olvera de la Cruz Dr. Baofu Qiao Dr. Ross J. Ellis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6899-6904
The lanthanide contraction is conceptualized traditionally through coordination chemistry. Here we break this mold in a structural study of lanthanide ions dissolved in an amphiphilic liquid. The lanthanide contraction perturbs the weak interactions between molecular aggregates that drive mesoscale assembly and emergent behavior. The weak interactions correlate with lanthanide ion transport properties, suggesting new strategies for rare‐earth separation that exploit forces outside of the coordination sphere. 相似文献
17.
Philip G. Harrison Adam Kelsall John V. Wood 《Journal of Sol-Gel Science and Technology》1998,13(1-3):1049-1055
The effect of the incorporation of rare earth cations and fluoride anions into the ceria fluorite lattice has been studied. Ternary Ln-Ce-O (Ln = La, Pr, Nd) oxide gels of target Ln : Ce ratios of 1 : 4, 1 : 1.86 and 1 : 1, with and without added fluoride ion, have been prepared, and the oxide materials obtained after calcination at 1223 K examined. Incorporation of Ln results in the formation of Ln/CeO2 solid solutions at low Ln levels, but a microscopic mixture of two cubic phases, pure ceria and a Ln-Ce-O phase of composition Ce0.35La0.65O1.67, is obtained when a 1 : 1 ratio is employed. With fluoride pure CeO2 and LaF3 are the only phases present and no mixed Ln-Ce-O phase is formed. TEM shows that the microstructure of this material is complex. The nature of analogous Pr- and Nd-substituted ceria materials is also described. 相似文献
18.
Surfactant-free nonaqueous (and/or nonhydrolytic) sol-gel routes constitute one of the most versatile and powerful synthesis methodologies for nanocrystalline metal oxides with high compositional homogeneity and purity. Although the synthesis protocols are particularly simple, involving only metal oxide precursors and common organic solvents, the obtained uniform nanocrystals exhibit an immense variety of sizes and shapes. The small number of reactants in these routes enables the study of the chemical mechanisms involved in metal oxide formation. Nonhydrolytic routes to inorganic nanomaterials that used surfactants as size- and shape-controlling agents have been discussed recently. This Minireview supplements this topic by discussing surfactant-free processes, which have become a valuable alternative to surfactant-assisted as well as to traditional aqueous sol-gel chemistry routes. 相似文献
19.
Interface-controlled synthesis of CeO2(111) and CeO2(100) and their structural transition on Pt(111)
Ceria-based catalytic materials are known for their crystal-face-dependent catalytic properties. To obtain a molecular-level understanding of their surface chemistry, controlled synthesis of ceria with well-defined surface structures is required. We have thus studied the growth of CeOx nanostructures (NSs) and thin films on Pt(111). The strong metal-oxide interaction has often been invoked to explain catalytic processes over the Pt/CeOx catalysts. However, the Pt-CeOx interaction has not been understood at the atomic level. We show here that the interfacial interaction between Pt and ceria could indeed affect the surface structures of ceria, which could subsequently determine their catalytic chemistry. While ceria on Pt(111) typically exposes the CeO2(111) surface, we found that the structures of ceria layers with a thickness of three layers or less are highly dynamic and dependent on the annealing temperatures, owing to the electronic interaction between Pt and CeOx. A two-step kinetically limited growth procedure was used to prepare the ceria film that fully covers the Pt(111) substrate. For a ceria film of ~3–4 monolayer (ML) thickness on Pt(111), annealing in ultrahigh vacuum (UHV) at 1000 K results in a surface of CeO2 (100), stabilized by a c-Ce2O3(100) buffer layer. Further oxidation at 900 K transforms the surface of the CeO2(100) thin film into a hexagonal CeO2(111) surface. 相似文献
20.
Kuntaiah Kuncham Sajitha Nair Smeer Durani Roopa Bose 《Journal of Radioanalytical and Nuclear Chemistry》2017,313(1):101-112
Ceria nanocrystals were synthesized by template free and cost effective method for highly efficient adsorption of U(VI) from aqueous solutions. In this study we investigated the factors influencing the adsorption behavior of U(VI) onto the ceria nanocrystals like pH, dosage, time of contact and initial metal ion concentration. The mechanism of adsorption was elucidated based on the isothermal and kinetic studies. A monolayer surface adsorption of uranyl ions onto the ceria nanocrystals with an adsorption capacity of 270 mg/g involving adsorptive pore filling and electrostatic interactions was indicated. The ceria nanocrystals could be regenerated and reused without significant reduction of adsorption capacities. 相似文献