Nanosized Building Blocks Research Articles

Bio-Inspired Fabrication of Hierarchical FeOOH Nanostructure Array Films at the Air–Water Interface, Their Hydrophobicity and Application for Water Treatment

Hierarchical FeOOH nanostructure array films constructed by different nanosized building blocks can be synthesized at the air-water interface via a bio-inspired gas-liquid diffusion method. In this approach, poly(acrylic acid) (PAA) as a crystal growth modifier plays a crucial role in mediating the morphology and polymorph of FeOOH crystals. With the increase of PAA concentration, the shape of the building blocks assembling into FeOOH films can be tailored from nanosheets, to rice spikes, then to branched fibers, and finally to nanowires. What is more, a low concentration of PAA will induce the formation of α-FeOOH, while a high one could stabilize FeOOH in the form of the γ-FeOOH phase. After being modified with a thin layer of polydimethylsiloxane (PDMS), the as-prepared FeOOH films exhibited strong hydrophobicity with water contact angles (CA) from 134° to 148° or even superhydrophobicity with a CA of 164° in the sample constructed by nanosheets. When the FeOOH nanostructures were dispersed in water by ultrasound, they displayed quite promising adsorption performance of heavy metal ions for water treatment, where the highest adsorption capacity can reach 77.2 mg·g⁻¹ in the sample constructed by nanowires. This bio-inspired approach may open up the possibilities for the fabrication of other functional nanostructure thin films with unique properties.

Co-assembled thin films of Ag nanowires and functional nanoparticles at the liquid–liquid interface by shaking

In this paper, we report the fabrication of co-assembled thin films composed of silver nanowires (NWs) and Au nanoparticles (NPs) at the liquid-liquid interface (water-chloroform) by vigorous shaking. The composition of co-assembled thin films can be controlled by adjusting the concentration of the nanosized building blocks. As a versatile interfacial assembly method, other nanoparticles such as Ag2S and Fe3O4 NPs can also be co-assembled with Ag NWs using the same procedure. Meanwhile, the co-assembly state of the obtained Au NPs and Ag NWs makes a significant contribution to the high sensitivity of surface-enhanced Raman scattering (SERS) to model the molecule 3,3'-diethylthiatricarbocyanine iodide (DTTCI). The SERS intensities show high dependence on the molar ratio of Au NPs and Ag NWs and the layer number of the co-assembled thin films. This shaking-assisted liquid-liquid assembly system has been proved to be a facile way for co-assembling nanowires and nanoparticles, and will pave a way for further applications of the macroscopic co-assemblies with novel functionalities.

Rational synthesis of hierarchically porous NiO hollow spheres and their supercapacitor application

Hierarchically porous-structured hollow spheres with the shell composed of nanosized building blocks are of great importance to the next-generation of electrochemical devices. We present a powerful chemical bath deposition method for the fabrication of hierarchically porous NiO hollow spheres composed of nanoflakes with thicknesses of ∼10nm. A plausible mechanism is proposed to explain the formation of the NiO hollow spheres. Supercapacitor electrodes based on the NiO hollow spheres are characterized. The NiO hollow spheres exhibit a specific capacitance of 346Fg−1 at 1Ag−1after 2000 cycles and an excellent cycling stability, owing to the unique hollow-sphere architecture providing fast ion/electron transfer. Our growth approach may offer a new strategy for the synthesis of other transition metal oxides hollow spheres for applications in electrochemical energy storage, catalysis, and gas sensing.

Facile Aerosol Route to Hollow CuO Spheres and its Superior Performance as an Oxidizer in Nanoenergetic Gas Generators

AbstractThermochemical metal/metal oxide redox reactions have twice the energy density of 2,4,6‐trinitrotoluene (TNT). They suffer, however, from low pressure‐volume work due to low gas expansion from the reaction. This study focuses on the development of a nanocomposite that delivers a high energy density and the potential of rapid gas release. Hollow CuO spheres with nanosized building blocks are fabricated using a “droplet‐to‐particle” aerosol spray pyrolysis method with the introduction of gas‐blowing agents in the synthesis procedure. Nanoaluminum with hollow CuO as an oxidizer ignites in a very violent manner and exhibits excellent gas‐generation behavior, demonstrating a high pressurization rate of 0.745 MPa μs−1 and a transient peak pressure of 0.896 MPa with a charge density of 1 mg cm−3, as well as a rapid oxygen release. Compared with wet‐chemistry methods, gas‐phase processes are relatively low cost, nominally offer a higher purity product, and are usually configured as continuous production processes, with a limited number of steps. The synthesis strategy demonstrated is simple and should be extendable to the preparation of other hollow metal oxide structures.

PbS–Organic Mesocrystals: The Relationship between Nanocrystal Orientation and Superlattice Array

The ability to prepare nanostructured and/or nanocompositematerials on a large scale by simple and controllable routesstill remainsachallenge in chemistry and materialscience. Byemploying well-established synthetic strategies, nanoparticleswith different sizes, shapes and compositions can be readilyproduced. The high tendency for self-aggregation and self-organization of these nanosized building blocks, which aresurface-stabilized by organic molecules, into superstructureshas been used to create 2D and 3D assemblies.

Self-Limiting Assembly of Two-Dimensional Domains from Graphene Oxide at the Air/Water Interface

Self-assembly is a powerful approach to making new superstructures and high-level hierarchical structures with unique physical/chemical properties from nanosized building blocks. As-prepared graphene oxides (GOs) are in general highly polydisperse not only in size but also in shape. Yet we have demonstrated that such GO sheets tend to assemble into two-dimensional, nearly monodisperse aggregate domains at the air/water interface in a self-limiting fashion, which can be controlled. It was further shown that the self-limiting assembly was driven by the competing interactions between electrostatic repulsion between the negatively charged GO sheets and attractive potentials. This finding provides a convenient platform to understand the forces involved in the 2D assembly and opens a new direction for creating novel materials and structures at the air/water interface.

Synthesis of Hierarchical Three-Dimensional Vanadium Oxide Microstructures as High-Capacity Cathode Materials for Lithium-Ion Batteries

Hierarchical three-dimensional (3D) vanadium oxide microstructures, including urchin-like microflowers, nanohorn-structured microspheres, nanosheet-assembled microflowers, and nanosheets bundles, are successfully synthesized by a versatile template-free solvothermal method. It is found that the concentration of the precursor (VOC(2)O(4)) solution has a significant effect on the morphologies of the products. As an example, the time-dependent phase and morphology evolution for the urchin-like vanadium oxide microflowers has been investigated in detail. Urchin-like VO(2) microflowers can be self-assembled within 2 h without using any surfactants. After calcination, the VO(2) microflowers can be easily transformed to urchin-like V(2)O(5) microstructures. The as-obtained V(2)O(5) microflowers are highly porous with a specific surface area of 33.64 m(2) g(-1). When evaluated as a cathode material for lithium-ion batteries, the V(2)O(5) sample delivers very high specific discharge capacity of 267 mA h g(-1) at a current density of 300 mA g(-1). Further, it also exhibits improved cycling stability. The excellent electrochemical performance is attributed to multiple advantageous structural features, including the nanosized building blocks, high porosity, and the 3D hierarchical microstructures.

A General Strategy for Self‐Assembly of Nanosized Building Blocks on Liquid/Liquid Interfaces

A family of water/oil interfaces is introduced to provide effective platforms for rapid fabrication of large-area self-assembled nanofilms composed of various nanosized building blocks, including nanoparticles (NPs), nanocubes (NC), nanowires (NWs), and nanosheets, at room temperature. As a general interfacial assembly method, NWs and NPs are co-assembled at the liquid/liquid interface. The as-prepared co-assembled Ag NW and Ag NC films show high surface-enhanced Raman spectroscopy (SERS) intensity, the SERS performance being strongly dependent on the number ratio of the two kinds of nanosized building blocks. The results demonstrate that this interfacial system provides a general method for the assembly of various nanosized building blocks with different shapes and dimensionalities, and thus paves an alternative pathway for further applications of macroscopic assemblies with different functionalities.

Hierarchical plasmonic-metal/semiconductor micro/nanostructures: green synthesis and application in catalytic reduction of p-nitrophenol

Hierarchical micro/nano arrays can offer both the advantages of nano-sized building blocks and micro- or submicrometer-sized ordered arrays, therefore representing one kind of potential functional materials and having received enormous attention for a wealth of applications. In this study, four-dimensionally flower-like CuO micro/nanostructures decorated by Au nanoparticles are synthesized via an environmentally friendly route assisted by polyethylene glycol. Experiments reveal that the product demonstrates high catalytic performance for the reduction of 4-nitrophenol using NaBH4 as the reducing agent, which could be attributed to the rich Au/CuO interfaces in the samples. Compared to the pure noble metal catalysts, the obtained sample is quite economic. In terms of methodology and cost-effectiveness, this study proposes an economically useful and green method to produce a highly efficient metal-based catalyst. It is also a good example for the organic combination of green chemistry and functional materials.

Hierarchically structured hybrid honeycomb films via micro to nanosized building blocks

Metal oxide nanoparticles were chemically modified by surface initiated polymerization to core@shell building blocks (CSBBs). These CSBBs were then self-assembled using the bottom up breath figure (BF) method to design honeycomb (HC) porous hybrid films exhibiting hexagonal pore arrays. Depending on the nature, the size and the shape of the building blocks, honeycomb hybrid films with tunable pore sizes can be achieved.

LiNi0.5Mn1.5O4 Hollow Structures as High‐Performance Cathodes for Lithium‐Ion Batteries

Built to last: Uniform LiNi0.5Mn1.5O4 hollow microspheres and microcubes (see picture; scale bars: 1 μm) with nanosized building blocks have been synthesized by a facile impregnation method followed by a simple solid-state reaction. The resultant LiNi0.5Mn1.5O4 hollow structures deliver a discharge capacity of about 120 mA h g−1 over prolonged cycling and exhibit excellent rate capability.

Biomolecule-assisted in situ route toward 3D superhydrophilic Ag/CuO micro/nanostructures with excellent artificial sunlight self-cleaning performance

Three-dimensionally (3D) hierarchical micro/nano oriented arrays constructed from nanometer-sized building blocks represent an important group of materials and have received enormous attention for a series of applications because they can offer both the advantages of nanosized building blocks and micro- or submicrometer-sized ordered arrays. In this work, 3D flower-like superhydrophilic CuO micro/nanostructures decorated by Ag nanoparticles were synthesized via an amino acid-assisted biomimetic hydrothermal method. Experiments reveal that the product demonstrates excellent sunlight self-cleaning performance in terms of wettability (without the help of high-free-energy compounds and in the absence of UV irradiation) and enhanced photocatalytic activities, which portends a bright future for this material as self-cleaning photovoltaic coatings. It is also a good example for the organic combination of green chemistry and functional materials.

Semiconducting oxide heterostructures

The properties of semiconducting oxide heterostructures are demonstrated using ZnO and its ternary alloy MgxZn1 − xO as a model system. This system is of particular importance, as it shows by far the most detailed research activities among oxide semiconductors. MgxZn1 − xO can be grown pseudomorphically on single crystalline ZnO in the step flow growth mode yielding atomically flat surfaces. In such structures, a two-dimensional electron gas was detected with an areal concentration of up to n2d = 3.9 × 1013 cm−2. The quantum Hall effect was observed in ZnO/MgxZn1 − xO single heterostructures, the first oxide system ever to show the quantum Hall effect. Likewise, quantization plays a dominating role in double heterostructures of ZnO and MgxZn1 − xO. Quantum confinement and the quantum-confined Stark effect were observed in ZnO/MgxZn1 − xO quantum wells grown by MBE and also by PLD. Finally, the ability to induce and control quantized states in ZnO/MgxZn1 − xO heterostructures was combined with the extraordinary properties of one-dimensional nanostructures, thus resulting in nano-sized building blocks.

Preparation and Li Storage Properties of Hierarchical Porous Carbon Fibers Derived from Alginic Acid

One-dimensional (1D) hierarchical porous carbon fibers (HPCFs) have been prepared by controlled carbonization of alginic acid fibers and investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nitrogen adsorption-desorption isotherms, and electrochemical tests toward lithium storage. The as-obtained HPCFs consist of a 3D network of nanosized carbon particles with diameters less than 10 nm and exhibit a hierarchical porous architecture composed of both micropores and mesopores. Electrochemical measurements show that HPCFs exhibit excellent rate capability and capacity retention compared with commercial graphite when employed as anode materials for lithium-ion batteries. At the discharge/charge rate of 45 C, the reversible capacity of HPCFs is still as high as 80 mA h g(-1) even after 1500 cycles, which is about five times larger than that of commercial graphite anode. The much improved electrochemical performances could be attributed to the nanosized building blocks, the hierarchical porous structure, and the 1D morphology of HPCFs.

Microrods based on nanocubes of Prussian blue

Using a facile dynamic vacuum evaporation method, a novel microrod with diameters of ca. 1–2 μm and lengths of up to 80 μm has been constructed using uniform Prussian blue (PB) nanocubes as the building blocks. The PB nanocubes are arranged fairly orderly in the rod-like superstructures. The assembled architecture can be transformed from one-dimensional microrods to two-dimensional layers via a fish-bone-like structure by tuning the evaporation rate. The formation of the PB superstructures follows an oriented-attachment mechanism and this provides a simple approach to fabricate hierarchical nanostructures and self-assembled superstructures using nanosized building blocks. Magnetic studies indicate that the PB microrods have a Curie temperature ( T c) of 4.9 K and a coercivity of ca. 26 Oe at 1.8 K. The photoluminescence (PL) spectra of the PB microrods and the dispersed nanocubes show an UV emission band at 358 and 367 nm respectively, suggesting an interesting assembly effect.

Engineering Multiwalled Carbon Nanotubes Inside a Transmission Electron Microscope Using Nanorobotic Manipulation

This paper provides a review of recent experimental techniques developed for shell engineering individual multiwalled carbon nanotubes (MWNTs). Basic processes for the nanorobotic manipulation of MWNTs inside a transmission electron microscope are investigated. MWNTs, bamboo-structured carbon nanotubes (CNTs), Cu-filled CNTs, and CNTs with quantum dots attached are used as test structures for manipulation. Picking is realized using van der Waals forces, ldquostickyrdquo probes, electron-beam-induced deposition, and electric breakdown. Cap opening and shell shortening are presented using field emission current. Controlled peeling and thinning of the shells of MWNTs are achieved by electric breakdown, and changes in MWNT structures are correlated with electrical measurements. These processes are fundamental for the characterization of nanoscale materials, the structuring of nanosized building blocks, and the prototyping of nanoelectromechanical systems.

Mercaptopyridine Surface-Functionalized CdTe Quantum Dots with Enhanced Raman Scattering Properties

We report that 3 nm diameter CdTe quantum dots can generate enhanced Raman scattering. The Raman signal of 4-mercaptopyridine (4-Mpy) adsorbed on CdTe quantum dots shows a 104 enhancement compared with that of bulk 4-Mpy. The enhanced phenomenon based on CdTe quantum dots also provides new insight to help understand the enhancement mechanism. A charge-transfer mechanism is most likely responsible for the observed enhancement, since plasmon resonances are ruled out. This study points to the possibility of using quantum dots, with chemisorption in some important practical systems, such as the application of quantum dots as nanosized building blocks and markers in biological imaging.

Charge-Transfer Interaction in Single-Walled Carbon Nanotubes with Tetrathiafulvalene and Their Applications

We observed that single-walled carbon nanotube (SWNT) was aligned in the presence of TTF This alignment was induced by a specific interaction between SWNT and tetrathiafulvalene (TTF), a well-known organic donor. The interaction between the two molecules can be explained by a charge-transfer, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The binding energies of S (2P1/2) and S (2P3/2) were shifted from 163.0 eV and 164.1 eV to 163.9 eV and 165.1 eV, respectively. In Raman spectra of the SWNT-TTF, three peaks of SWNT in radial breathing mode were also upshifted by 4-5 cm(-1). The charge-transfer interaction also contributed in modifying the electronic structure of SWNT and furthermore enhanced the electrical conductivity of SWNT. A more conductive thin film was fabricated using the SWNT-TTF Four-probe measurement revealed that the surface resistance of the SWNT-TTF film was reduced to 4.359 omega at room temperature while that of SWNT film was 6.894 omega. These results enable carbon nanotubes to be utilized more for practically for industrial applications in fabricating peculiar nano-sized building blocks.

New Methacrylate-Functionalized Ba and Ba−Ti Oxoclusters as Potential Nanosized Building Blocks for Inorganic−Organic Hybrid Materials: Synthesis and Characterization

Two different methacrylate modified barium-titanium and barium-based oxoclusters, Ba2Ti10(mu3-O)8(mu2-OH)5(mu2-OMc)20(OiPrOMe)2 (1) and [Ba(OMc)2(McOH)3]n (2), were synthesized by reacting methacrylic acid with barium-titanium and barium-zirconium double alkoxides, respectively. The X-ray structure determination of oxocluster 1 shows a core consisting of a ring of 10 titania octahedra, sharing corners, that surround the two barium oxygen decaeders which are linked by common edges to the titania octahedra and the neighboring barium decaeder. The solid-state structure of 2 consists of zigzag chains of edge-sharing {BaO9} polyhedra linked through bridging bidentate metacrylate anions, displaying different coordination mode of carboxylate groups. The presence of methacrylate groups surrounding the two polynuclear compounds has been exploited for the embedding of the oxocluster in inorganic-organic hybrid materials, and some preliminary results are presented.

NANOROBOTIC MANIPULATION OF CARBON NANOTUBES INSIDE A TRANSIMISSION ELECTRON MICROSCOPE

Basic processes for nanorobotic manipulation of carbon nanotubes (CNTs) inside a transmission electron microscope are investigated experimentally. These processes are fundamental for the characterization of nanoscale materials, for the structuring of nanosized building blocks, and for the prototyping of nanoelectromechanical systems. Multi-walled CNTs, bamboo-structured CNTs, Cutipped CNTs, and quantum dots attached to CNTs have been used as test structures for manipulation.