Mesoscale Organization of CuO Nanoribbons: Formation of “Dandelions”

Freestanding three-dimensional core-shell nanoarrays for lithium-ion battery anodes

Structural degradation and low conductivity of transition-metal oxides lead to severe capacity fading in lithium-ion batteries. Recent efforts to solve this issue have mainly focused on using nanocomposites or hybrids by integrating nanosized metal oxides with conducting additives. Here we design specific hierarchical structures and demonstrate their use in flexible, large-area anode assemblies. Fabrication of these anodes is achieved via oxidative growth of copper oxide nanowires onto copper substrates followed by radio-frequency sputtering of carbon-nitride films, forming freestanding three-dimensional arrays with core–shell nano-architecture. Cable-like copper oxide/carbon-nitride core–shell nanostructures accommodate the volume change during lithiation−delithiation processes, the three-dimensional arrays provide abundant electroactive zones and electron/ion transport paths, and the monolithic sandwich-type configuration without additional binders or conductive agents improves energy/power densities of the whole electrode.

Degradation and low conductivity of transition metal oxide anodes cause capacity fading in lithium ion batteries. Here the authors make freestanding 3D copper oxide/carbon nitride core-shell nanoarrays which accommodate volume change, provide electro-active zones and facilitate rapid charge transport.

Novel synthesis process for solar-light-active porous carbon-doped CuO nanoribbon and its photocatalytic application for the degradation of an organic dye

A simple, one-step novel solution process was developed for the synthesis of carbon-doped CuO (C-CuO) nanoribbons without the use of a catalyst, template, substrate, or costly instrumentation at room temperature.

Microstructure construction and composition modification of CeO2 macrospheres with superior performance

With controlled hydrolysis of DMF, condensed and hollow macrospherical Ce(COOH)₃ precursors are selectively produced. Upon calcination the spherical CeO₂ with high specific surface area, oxygen storage capacity and the Cr(vi) adsorption ability are obtained.

Facile synthesis of ternary CdMnS QD-based hollow nanospheres as fluorescent/magnetic probes for bioimaging

Fluorescent/magnetic dual-functional CdMnS hollow nanospheres with bright tunable emission and strong MR signal were synthesized via a facile Ostwald-ripening process with promising applications in bioimaging.

Synthesis of high quality CuO nanoflakes and CuO–Au nanohybrids for superior visible light photocatalytic behavior

High-quality CuO nanoflakes and CuO–Au nanohybrids are synthesized by a facile wet chemistry strategy. Compared with pure CuO nanoflakes, CuO–Au nanohybrids exhibit superior visible light-driven photocatalytic performance and have a higher photocurrent density (46 mA cm⁻²).

Toward Ending the Guessing Game: Study of the Formation of Nanostructures Using In Situ Liquid Transmission Electron Microscopy

The field of synthetic nanochemistry has grown tremendously in the past three decades since the discovery of nonaqueous synthesis of monodispersed particles. Almost all classes of materials, from II-VI semiconductor to metal, alloy, and metal oxide can now be prepared in various sizes and shapes. One major challenge has been the development of a technique for direct real-time recording of data during the formation of nanostructures in liquid reaction media where nucleation and growth occur. A viable solution finally arrived with the recent development of static and flow liquid cells for transmission electron microscopy (TEM). This Perspective will showcase a few selected examples in this rapidly growing area, with a focus on using the new capabilities of liquid TEM (LTEM) for quantitative study of nucleation and growth, as well as shape formation of nanocrystals in solution. A discussion on future direction is also presented.

A new approach for crystallization of copper(II) oxide hollow nanostructures with superior catalytic and magnetic response

We report the synthesis of copper(II) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow structures. The synthesis also leads to modification of physical properties such as magnetism.

ZnO/CoO and ZnCo2O4 Hierarchical Bipyramid Nanoframes: Morphology Control, Formation Mechanism, and Their Lithium Storage Properties

Mastery over the structure of nanoscale materials can effectively tailor and regulate their electrochemical properties, enabling improvement in both rate capability and cycling stability. We report the shape-controlled synthesis of novel mesoporous bicomponent-active ZnO/CoO hierarchical multilayered bipyramid nanoframes (HMBNFs). The as-synthesized micro/nanocrystals look like multilayered bipyramids and consist of a series of structural units with similar frames and uniform sheet branches. The use of an appropriate straight-chain monoalcohol was observed to be critical for the formation of HMBNFs. In addition, the structure of HMBNFs could be preserved only in a limited range of the precursor ratio. An extremely fast crystal growth process and an unusual transverse crystallization of the ZnCo-carbonate HMBNFs were newly discovered and proposed. By calcination of ZnCo-carbonate HMBNFs at the atmosphere of nitrogen and air, ZnO/CoO and ZnCo2O4 HMBNFs were obtained, respectively. Compared to the ZnCo2O4 HMBNFs, the ZnO/CoO HMBNFs with a uniform distribution of nanocrystal ZnO and CoO subunits exhibited enhanced electrochemical activity, including greater rate capability and longer cycling performance, when evaluated as an anode material for Li-ion batteries. The superior electrochemical performance of the ZnO/CoO HMBNFs is attributed to the unique nanostructure, bicomponent active synergy, and uniform distribution of ZnO and CoO phases at the nanoscale.

Spherulitic copper-copper oxide nanostructure-based highly sensitive nonenzymatic glucose sensor

In this work, three different spherulitic nanostructures Cu-CuOA, Cu-CuOB, and Cu-CuOC were synthesized in water-in-oil microemulsions by varying the surfactant concentration (30 mM, 40 mM, and 50 mM, respectively). The structural and morphological characteristics of the Cu-CuO nanostructures were investigated by ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy techniques. The synthesized nanostructures were deposited on multiwalled carbon nanotube (MWCNT)-modified indium tin oxide (ITO) electrodes to fabricate a nonenzymatic highly sensitive amperometric glucose sensor. The performance of the ITO/MWCNT/Cu-CuO electrodes in the glucose assay was examined by cyclic voltammetry and chronoamperometric studies. The sensitivity of the sensor varied with the spherulite type; Cu-CuOA, Cu-CuOB, and Cu-CuOC exhibited a sensitivity of 1,229, 3,012, and 3,642 µA mM(-1)·cm(-2), respectively. Moreover, the linear range is dependent on the structure types: 0.023-0.29 mM, 0.07-0.8 mM, and 0.023-0.34 mM for Cu-CuOA, Cu-CuOB, and Cu-CuOC, respectively. An excellent response time of 3 seconds and a low detection limit of 2 µM were observed for Cu-CuOB at an applied potential of +0.34 V. In addition, this electrode was found to be resistant to interference by common interfering agents such as urea, cystamine, L-ascorbic acid, and creatinine. The high performance of the Cu-CuO spherulites with nanowire-to-nanorod outgrowths was primarily due to the high surface area and stability, and good three-dimensional structure. Furthermore, the ITO/MWCNT/Cu-CuOB electrode applied to real urine and serum sample showed satisfactory performance.

Facile Synthesis of Novel Redox-Mediator-free Direct Z-Scheme CaIn2S4 Marigold-Flower-like/TiO2 Photocatalysts with Superior Photocatalytic Efficiency

Novel redox-mediator-free direct Z-scheme CaIn2S4 marigold-flower-like/TiO2 (CIS/TNP) photocatalysts with different CaIn2S4 weight percentages were synthesized using a facile wet-impregnation method. Uniform hierarchical marigold-flower-like CaIn2S4 (CIS) microspheres were synthesized using a hydrothermal method. Field-emission scanning electron microscopy and transmission electron microscopy analyses suggested that the formation and aggregation of nanoparticles, followed by the growth of petals or sheets and their subsequent self-assembly, led to the formation of the uniform hierarchical marigold-flower-like CIS structures. The photocatalytic degradation efficiency of the direct Z-scheme CIS/TNP photocatalysts was evaluated through the degradation of the pharmaceutical compounds isoniazid (ISN) and metronidazole (MTZ). The direct Z-scheme CaIn2S4 marigold-flower-like/TiO2 (1%-CIS/TNP) photocatalyst showed enhanced performance in the ISN (71.9%) and MTZ (86.5%) photocatalytic degradations as compared to composites with different CaIn2S4 contents or the individual TiO2 and CaIn2S4. A possible enhancement mechanism based on the Z-scheme formed between the CIS and TNP for the improved photocatalytic efficiency was also proposed. The recombination rate of the photoinduced charge carriers was significantly suppressed for the direct Z-scheme CIS/TNP photocatalyst, which was confirmed by photoluminescence analysis. Radical-trapping studies revealed that photogenerated holes (h+), •OH, and O2•- are the primary active species, and suggested that the enhanced photocatalytic efficiency of the 1%-CIS/TNP follows the Z-scheme mechanism for transferring the charge carriers. It was further confirmed by hydroxyl (•OH) radical determination via fluorescence techniques revealed that higher concentration of •OH radical were formed over 1%-CIS/TNP than over bare CIS and TNP. The separation of the charge carriers was further confirmed using photocurrent and electron spin resonance measurements. Kinetic and chemical oxygen demand analyses were performed to confirm the ISN and MTZ degradation. The results demonstrated that the direct Z-scheme CIS/TNP photocatalyst shows superior decomposition efficiency for the degradation of these pharmaceuticals under the given reaction conditions.

Hierarchical Molybdenum Nitride Nanochexes by a Textured Self-Assembly in Gas-Solid Phase for the Enhanced Application in Lithium Ion Batteries

Self-assembly, as one kind of general phenomenon, has often been reported in solution chemistry. However, in gas-solid phase, it seldom has been disclosed. The MoN nanochex exhibits unique geometrical shape. Its body segment is composed of textured single crystal MoN nanowires, while its edges parallel to [1̅22̅] direction are attached by nanowires whose crystal orientation is different from that of the body segment. In this paper, the structure of the MoN nanochex is studied, and accordingly, a possible growth mechanism is proposed. We expect to extend this method to designed synthesis of many other functional materials, such as nitrides, carbides, and borides, and thereby to significantly tailor their resulting properties. Meanwhile, as one promising electrode material for Li-ion batteries (LIBs), MoN nanochex on Ti foil has been applied in the electrochemical energy storage, and stably delivered a specific capacity of 720 mAh/g with a remarkable Coulombic efficiency up to 98.5%, implying an achieved synergic effect derived from both mesoporous structure and the direct contact with the conducting substrate.

Generation of Scalable, Metallic High-Aspect Ratio Nanocomposites in a Biological Liquid Medium

The goal of this protocol is to describe the synthesis of two novel biocomposites with high-aspect ratio structures. The biocomposites consist of copper and cystine, with either copper nanoparticles (CNPs) or copper sulfate contributing the metallic component. Synthesis is carried out in liquid under biological conditions (37 °C) and the self-assembled composites form after 24 hr. Once formed, these composites are highly stable in both liquid media and in a dried form. The composites scale from the nano- to micro- range in length, and from a few microns to 25 nm in diameter. Field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX) demonstrated that sulfur was present in the NP-derived linear structures, while it was absent from the starting CNP material, thus confirming cystine as the source of sulfur in the final nanocomposites. During synthesis of these linear nano- and micro-composites, a diverse range of lengths of structures is formed in the synthesis vessel. Sonication of the liquid mixture after synthesis was demonstrated to assist in controlling average size of the structures by diminishing the average length with increased time of sonication. Since the formed structures are highly stable, do not agglomerate, and are formed in liquid phase, centrifugation may also be used to assist in concentrating and segregating formed composites.

A template-free method for stable CuO hollow microspheres fabricated from a metal organic framework (HKUST-1)

Uniform CuO hollow microspheres were successfully achieved from a non-uniform metal organic framework by using a template-free method. The process mechanism has been revealed to be spherical aggregation and Ostwald ripening. When tested in CO oxidation and heat treatment, these assembled microspheres exhibited an excellent catalytic performance and show a much better stability than the inherited hollow structure from MOFs.

Facile synthesis of graphene-like copper oxide nanofilms with enhanced electrochemical and photocatalytic properties in energy and environmental applications

Novel graphene-like CuO nanofilms are grown on a copper foam substrate by in situ anodization for multifunctional applications as supercapacitor electrodes and photocatalysts for the degradation of dye pollutants. The as-prepared CuO consists of interconnected, highly crystalline, conductive CuO nanosheets with hierarchical open mesopores and a large surface area. The CuO nanofilms supported on a copper foam are employed as freestanding, binder-free electrodes for supercapacitors, which exhibit wonderful electrochemical performance with a large specific capacitance (919 F g(-1) at 1 A g(-1)), an excellent cycling stability (7% capacitance loss after 5000 cycles), and a good rate capability (748 F g(-1) at 30 A g(-1)). The porous CuO nanofilms also demonstrate excellent photocatalytic activities for degradation of methylene blue, with a degradation rate 99% much higher than 54% of the commercial CuO powders after 60 min. This excellent energy storage and photocatalytic performance of the graphene-like CuO nanofilms can open a new avenue for large-scale applications in energy and environmental fields.

A green strategy to prepare metal oxide superstructure from metal-organic frameworks

Metal or metal oxides with diverse superstructures have become one of the most promising functional materials in sensor, catalysis, energy conversion, etc. In this work, a novel metal-organic frameworks (MOFs)-directed method to prepare metal or metal oxide superstructure was proposed. In this strategy, nodes (metal ions) in MOFs as precursors to form ordered building blocks which are spatially separated by organic linkers were transformed into metal oxide micro/nanostructure by a green method. Two kinds of Cu-MOFs which could reciprocally transform by changing solvent were prepared as a model to test the method. Two kinds of novel CuO with three-dimensional (3D) urchin-like and 3D rods-like superstructures composed of nanoparticles, nanowires and nanosheets were both obtained by immersing the corresponding Cu-MOFs into a NaOH solution. Based on the as-formed CuO superstructures, a novel and sensitive nonenzymatic glucose sensor was developed. The small size, hierarchical superstructures and large surface area of the resulted CuO superstructures eventually contribute to good electrocatalytic activity of the prepared sensor towards the oxidation of glucose. The proposed method of hierarchical superstructures preparation is simple, efficient, cheap and easy to mass production, which is obviously superior to pyrolysis. It might open up a new way for hierarchical superstructures preparation.

Synthesis of Pt-Rich@Pt–Ni alloy core–shell nanoparticles using halides

We demonstrated the synthesis of Pt–Ni alloy core–shell nanoparticles (NPs) via a one-pot thermal decomposition method, optimized by variation of the concentration of cetyltrimethylammonium chloride (CTAC) and reaction time.

Biomolecule-assisted route for shape-controlled synthesis of 3D flower-like CdWO4 microstructures

Plausible mechanism for the formation of 3d hierarchical flower-like structures.

Synthesis of MoO2 hierarchical peony-like microspheres without a template and their application in lithium ion batteries

Hierarchical peony-like MoO₂ microspheres are fabricated via a simple template-free solvothermal method and evaluated as anode materials.

Hollow TS-1 mesocrystals: hydrothermal construction and high catalytic performances in cyclohexanone ammoximation

Hollow TS-1 mesocrystals were obtained by the hydrothermal treatment. The hollow mesocrystalline structure significantly affects their catalytic activity in cyclohexanone ammoximation.

Enhanced electrochemical performance of a ZnO–MnO composite as an anode material for lithium ion batteries

A reduced ZnO–MnO composite electrode exhibits improved electrochemical performance as an anode material for lithium ion batteries.

Hierarchical 3D-flower-like CuO nanostructure on copper foil for supercapacitors

We present a novel route for the synthesis of CuO thin films. The nano-flower like nanostructures provide high surface area, and the CuO shows excellent supercapacitive properties.

Nanoporous copper oxide ribbon assembly of free-standing nanoneedles as biosensors for glucose

Two-dimensional (2D) hierarchical nanoporous CuO ribbons were successfully synthesized by a green solution-phase route. They serve as a promising electrode material for nonenzymatic glucose detection and show high sensitivity, a low detection limit, fast amperometric response and good selectivity.

A facile hydrothermal method to synthesize Sb2S3/Sb4O5Cl2 composites with three-dimensional spherical structures

Three-dimensional spherical Sb₂S₃/Sb₄O₅Cl₂ microcrystallines were synthesized for the first time via a facile hydrothermal process without any oxychlorides at 100 °C.

Hollow mesoporous NiCo2O4 nanocages as efficient electrocatalysts for oxygen evolution reaction

The NiCo₂O₄ nanocage with a hollow cavity, large roughness and high porosity exhibits an excellent and stable activity for the oxygen evolution reaction (OER) catalysis.

Fabrication of CdMoO4@CdS core–shell hollow superstructures as high performance visible-light driven photocatalysts

Core–shell CdMoO₄@CdS hollow microspheres, fabricated by a simple ion-exchange hydrothermal method, exhibit outstanding photocatalytic activity toward degradation of RhB dye solution.

Morphology engineering of high performance binary oxide electrodes

Advances in materials have preceded almost every major technological leap since the beginning of civilization. On the nanoscale and microscale, mastery over the morphology, size, and structure of a material enables control of its properties and enhancement of its usefulness for a given application, such as energy storage. In this review paper, our aim is to present a review of morphology engineering of high performance oxide electrode materials for electrochemical energy storage. We begin with the chemical bonding theory of single crystal growth to direct the growth of morphology-controllable materials. We then focus on the growth of various morphologies of binary oxides and their electrochemical performances for lithium ion batteries and supercapacitors. The morphology-performance relationships are elaborated by selecting examples in which there is already reasonable understanding for this relationship. Based on these comprehensive analyses, we proposed colloidal supercapacitor systems beyond morphology control on the basis of system- and ion-level design. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

VO2 nanowires assembled into hollow microspheres for high-rate and long-life lithium batteries

Development of three-dimensional nanostructures with high surface area and excellent structural stability is an important approach for realizing high-rate and long-life battery electrodes. Here, we report VO2 hollow microspheres showing empty spherical core with radially protruding nanowires, synthesized through a facile and controllable ion-modulating approach. In addition, by controlling the self-assembly of negatively charged C12H25SO4(-) spherical micelles and positively charged VO(2+) ions, six-armed microspindles and random nanowires are also prepared. Compared with them, VO2 hollow microspheres show better electrochemical performance. At high current density of 2 A/g, VO2 hollow microspheres exhibit 3 times higher capacity than that of random nanowires, and 80% of the original capacity is retained after 1000 cycles. The superior performance of VO2 hollow microspheres is because they exhibit high surface area about twice higher than that of random nanowires and also provide an efficient self-expansion and self-shrinkage buffering during lithiation/delithiation, which effectively inhibits the self-aggregation of nanowires. This research indicates that VO2 hollow microspheres have great potential for high-rate and long-life lithium batteries.

A novel method to enhance the conductance of transitional metal oxide electrodes

Transitional metal oxides hold great potential for high capacity anodes. However, the low electron conductivity of such materials leads to poor cycling stability and inferior rate capability. We reported herein the use of a novel hydrogen plasma technology to improve the conductance of metal oxides, which leads great success in improving the rate performance of CuO nanotube based anodes. This method has the potential to be widely adopted in the field of lithium ion batteries and supercapacitors.

Electrochemical synthesis of p-CuO thin films and development of a p-CuO/n-ZnO heterojunction and its application as a selective gas sensor

The fabricated p-CuO/n-ZnO heterojunction senses gases selectively at room temperature.

Splitting growth of novel CuO straw sheaves and their improved photocatalytic activity due to exposed active {110} facets and crystallinity

Novel CuO straw sheaves formed by a splitting growth process show an improved photodegradation activity of RhB.