Controlled reactions on a copper surface: synthesis and characterization of nanostructured copper compound films

Fabrication of three-dimension hierarchical structure CuO nanoflowers and their antifungal mechanism against Bipolaris sorokiniana

Nanomaterials are widely investigated in sustainable agriculture owing to their unique physicochemical properties, especially Cu-based nanomaterial with eco-friendliness and essential for plant. However, the effect of CuO nanomaterial on Bipolaris sorokiniana (B. sorokiniana) is yet to be systematically understood. In this study, a three-dimension hierarchical structure CuO nanoflower (CuO NF) with ultrathin petals and excellent dispersibility in water was constructed and proved to have outstanding antifungal activity against B. sorokiniana with the inhibition rate of 86 % in mycelial growth, 74 % in mycelial dry weight and 75 % in conidial germination. Furthermore, the antifungal mechanism was assigned to the production of reactive oxygen species in intracellular caused by antioxidant mimicking activity of CuO NF to damage of cell membrane integrity and result cellular leakage. Additionally, the good control effect of CuO NF on wheat diseases caused by B. sorokiniana was demonstrated through pot experiment. This article firstly reveals the antifungal activity and mechanism of CuO NF on B. sorokiniana, and establishes the relationship between enzyme-like activity of CuO NF and its antifungal activity, which provides a promising application of Cu-based nanomaterial as nanofungicide in plant protection and a theoretical foundation for structure design of nanomaterials to improve their antifungal activities.

In situ growth of self-supported CuO nanorods from Cu-MOFs for glucose sensing and elucidation of the sensing mechanism

Herein, we present a simple and mild method to in situ prepare CuO nanostructures for non-enzymatic glucose sensing. A Cu-metal organic framework (Cu-MOF) precursor was first directly grown on a pencil lead electrode with 3D graphene-like surfaces (EPLE) and then in situ transformed into CuO nanorods. The CuO nanorod-modified EPLE (CuO/EPLE) shows high sensitivity (1138.32 μA mM-1 cm-2), fast response time (1.5 s) and low detection limit (0.11 μM) for glucose oxidation. It has been found that NaOH promoted the generation of ˙OH groups and Cu(III) on the CuO surface, which then facilitated the electrochemical oxidation of glucose. Signals characteristic of hydroxyl and carbon-centered radical adducts were detected by EPR. Furthermore, the CuO/EPLE sensor also shows good accuracy in glucose determination in human serum samples.

Catalytic performance of PVP-coated CuO nanosheets under environmentally friendly conditions

Aromatic nitro compounds are an increasing concern worldwide due to their potential toxicity, prompting a quest for efficient removal approaches. This study established a simple and environmentally friendly method to synthesize a highly efficient, recoverable and stable CuO nanosheets catalyst to overcome public health and environmental problems caused by nitro aromatic compounds. In the current research, the effect of different concentrations of copper nitrate on the size and shape of CuO nanostructures in the chemical synthesis was studied. The CuO nanosheets were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectrophotometry. It was found that at concentrations of 0.07 M and 0.1 M of copper nitrate, pure CuO was formed. The FTIR results showed that carbonyl group in PVP coordinated with CuO and formed a protective layer. The as-synthesized CuO nanosheets with an average width of 60 ± 23 nm and length of 579 ± 154 were used as a catalyst for highly selective and efficient reduction of aromatic nitro and aromatic carboxylic acid to the corresponding amine and alcohol compounds. The reduction reaction was monitored by either UV-Vis absorption spectroscopy or high performance liquid chromatography (HPLC). 4-Nitrophenol and 4-nitroaniline were reduced to corresponding amine compounds within 12 min and 6 min, respectively in the presence of a reasonable amount of catalyst and reducing agent. The CuO nanosheets also exhibited excellent stability. The catalyst can be reused without loss of its activity after ten runs.

CO2 bubble-assisted in-situ construction of mesoporous Co-doped Cu2(OH)2CO3 nanosheets as advanced electrodes towards fast and highly efficient electrochemical reduction of nitrate to N2 in wastewater

The development of high-efficient and cost-effective electrocatalysts is crucial to remove nitrate pollutant in wastewater. Herein, we design and prepare mesoporous Co-doped Cu₂(OH)₂CO₃ malachite nanosheets as an electrocatalyst toward highly efficient nitrate reduction using a facile CO₂ bubble-assisted coprecipitation synthesis. The electrocatalytic performance is subject to the Co/Cu ratio of this malachite. Remarkably, compared with the pristine monometal Cu or Co-based electrocatalyst, the optimal electrocatalyst, 0.3Co@Cu₂(OH)₂CO₃, displays fast and highly efficient removal capacity of nitrate with an impressive high total nitrogen (TN) removal of 8628.99 mg N g^-1_CoCu (398.79 mg N g_cat^-1 h^-1), N₂ selectivity of 97.11% as well as negligible nitrite product at 100 mg L^-1 NO₃^--N and 2000 mg L^-1 Cl^- neutral electrolyte. Above all, high total nitrogen removal efficiency (81.92%) and chemical oxygen demand (73.74%) in actual wastewater. Its excellent electrocatalytic performance is achieved by regulating the electronic structure and the adsorption/desorption of the intermediate. This study discovers a new type of electrode materials for nitrate removal in wastewater.

Hydrophilic and Hydrophobic Nanostructured Copper Surfaces for Efficient Pool Boiling Heat Transfer with Water, Water/Butanol Mixtures and Novec 649

Increasing heat dissipation requirements of small and miniature devices demands advanced cooling methods, such as application of immersion cooling via boiling heat transfer. In this study, functionalized copper surfaces for enhanced heat transfer are developed and evaluated. Samples are functionalized using a chemical oxidation treatment with subsequent hydrophobization of selected surfaces with a fluorinated silane. Pool boiling tests with water, water/1-butanol mixture with self-rewetting properties and a novel dielectric fluid with low GWP (Novec™ 649) are conducted to evaluate the boiling performance of individual surfaces. The results show that hydrophobized functionalized surfaces covered by microcavities with diameters between 40 nm and 2 µm exhibit increased heat transfer coefficient (HTC; enhancements up to 120%) and critical heat flux (CHF; enhancements up to 64%) values in comparison with the untreated reference surface, complemented by favorable fabrication repeatability. Positive surface stability is observed in contact with water, while both the self-rewetting fluids and Novec™ 649 gradually degrade the boiling performance and in some cases also the surface itself. The use of water/1-butanol mixtures in particular results in surface chemistry and morphology changes, as observed using SEM imaging and Raman spectroscopy. This seems to be neglected in the available literature and should be focused on in further studies.

Wettability Difference Induced Out-of-Plane Unidirectional Droplet Transport for Efficient Fog Harvesting

Securing freshwater resources is a global issue for ensuring sustainable development. Fog harvesting is attracting great attention as a method to collect water without any energy input. Previous reports that were inspired by insects and plants have given insights such as the effectiveness of in-plane wettability and structural differences for droplet transport, which might enhance artificial water harvesting efficiency. However, further efforts to transfer droplets while maintaining performance are needed because droplet motion owing to these effects is limited to the in-plane direction. In this study, we report droplet transport between three-dimensional copper wire structures with nanostructured hydrophobic and superhydrophilic features. This mechanism enhanced the fog harvesting capability by more than 20% compared with the cumulative value of individual wires. In addition, the relationship between the droplet height and spacing of wires affected the performance. Our results show the importance of out-of-plane directional droplet transport from the wire surface assisted by differences in wire wettability, which minimizes limiting factors of fog harvesting including clogging and droplet shedding. Furthermore, the proposed arrangement reduces the overall system width compared with that of a two-dimensional arrangement while maintaining the amount of harvested water. These results provide a promising approach to designing large-scale and highly efficient fog harvesters.

Enhanced cyclic performance initiated via an in situ transformation of Cu/CuO nanodisk to Cu/CuO/Cu2O nanosponge

A simple oxidation method for preparing CuO nanodisks on a flexible Cu sheet is presented. The crystal structure of as-prepared CuO nanodisks was analyzed by X-ray diffraction. The elemental composition and surface morphology were documented by X-ray photoelectron spectroscopy, scanning, and transmission electron microscopy. The photocatalytic performance of flexible Cu/CuO nanodisks was tested to mediate the degradation of RhB and MB dyes. After 2nd recycling, an in situ transformation of the nanodisk surface leads to electron transfer between the conduction bands of Cu₂O and CuO phase, accelerating the degradation of the dyes due to a more favorable electron-hole separation under different band gap engineering. The optical and electrochemical impedance analyses were conducted to examine the efficiency of photogenerated charge carrier separation. Additionally, in the photodegradation system of Cu/CuO nanodisks, the generation of superoxide radical (·O^2-) is responsible for the dye degradation under daylight irradiation. The generation of the latter radical is energetically feasible since the conduction band of Cu₂O (- 0.28 eV) is well-matching with the redox potential of O₂/·O^2- (- 0.28 eV). Consequently, it is concluded that the cyclic stability shows the usefulness of Cu/CuO nanodisk preparation for the dye degradation under daylight irradiation. Graphical abstract.

Copper Oxide/Hydroxide Nanomaterial Synthesized from Simple Copper Salt

The copper oxide, CuO, and copper hydroxide, Cu(OH)2 nanomaterials have been prepared by a simple copper salt aqueous solution reaction. The powder X-ray diffraction (XRD) analysis showed the successful formation of Cu(OH)2 and CuO nanoparticles. The average crystallite size of these Cu(OH)2 and CuO nanoparticles was estimated and found to be around 17[Formula: see text]nm (Cu(OH)2) and 10[Formula: see text]nm (CuO). The surface morphology and size of the CuO particles were confirmed by Scanning Electron Microscope (SEM) and High-resolution transmission electron microscope (HRTEM). The Raman analysis, dielectric and conductivity of CuO nanoparticles have been performed. The frequency variation of the capacitance (real dielectric constant) and dielectric loss was studied. The capacitance of the CuO nanoparticles is high at low frequencies and decreases rapidly when the frequency is increased. The frequency dependent ac conductivity follows Johnscher’s power law.

Sessile Droplet Freezing on Hydrophobic Structured Surfaces under Cold Ambient Conditions

There have been conflicting reports as to whether surface wettability is effective in the freezing delay enhancement of attached water droplets. It is an important problem in the development of anti-icing surfaces needed for applications, such as aircraft wings and infrastructures. Here, we prepared precooled ambient conditions and surfaces which included smooth, microstructured, and two nanostructured surfaces with hydrophobic coatings to create an environment closer to the actual environment and to avoid frost formation, which enhances wetting transition and nucleation. Static and dynamic wetting characteristics of each surface were investigated as the fundamental properties and the freezing behavior of precooled water droplets were observed. A distinct elongation of the freezing delay time was observed for droplets on nanostructured surfaces which have static contact angles >150°, in contrast to those on smooth and microstructured surfaces. However, the difference in droplet adhesion induced by nanostructures showed a negligible impact on freezing delay. These results indicated that the reduction of the actual contact area between the solid and liquid phases restricted ice nucleus formation.

Novel flexible Fenton-like catalyst: Unique CuO nanowires arrays on copper mesh with high efficiency across a wide pH range

Free-standing and flexible Cu@CuO nanowires (NWs) mesh as an easily recycled Fenton-like catalyst is developed for the first time. Dense CuO nanowire arrays were uniformly grown on a copper mesh surface simply by wet etching accompanied with thermal dehydration. These dense CuO NWs provide a large specific area and therefore guarantee excellent catalytic performance toward the degradation of rhodamine B (RhB). With a k-value of 0.23 min^-1, such a Cu@CuO NWs mesh is able to degrade 100% RhB in only 16 min. This Fenton-like catalyst is also appropriate for degrading other organic dyes, including crystal violet, methylene blue, and rhodamine 6G. Unlike the conventional Fenton catalyst implemented at a pH value around 3, the Cu@CuO NWs mesh could adapt to a wide pH range from 2.1 to 12.0. More intriguingly, the Cu@CuO NWs mesh with excellent flexibility could be easily recycled after catalysis, which is a significant advance compared to the previously reported Fenton catalysts in the form of powders or nanoparticles. In addition, the recycling performance of this Cu@CuO NWs mesh was also assessed. On the basis of electron spin resonance (ESR) results, O^2- rather than OH is the main active species for the dye degradation by the Cu@CuO NWs mesh. With a marvelous combination of excellent flexibility, wide pH adaptation, and high efficiency, this easily recycled three dimensional Cu@CuO NWs architecture can afford new ideas for the Fenton chemistry.

Synthesis of Heart/Dumbbell-Like CuO Functional Nanostructures for the Development of Uric Acid Biosensor

It is always demanded to prepare a nanostructured material with prominent functional properties for the development of a new generation of devices. This study is focused on the synthesis of heart/dumbbell-like CuO nanostructures using a low-temperature aqueous chemical growth method with vitamin B₁₂ as a soft template and growth directing agent. CuO nanostructures are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. CuO nanostructures are heart/dumbbell like in shape, exhibit high crystalline quality as demonstrated by XRD, and have no impurity as confirmed by XPS. Apparently, CuO material seems to be porous in structure, which can easily carry large amount of enzyme molecules, thus enhanced performance is shown for the determination of uric acid. The working linear range of the biosensor is 0.001 mM to 10 mM with a detection limit of 0.0005 mM and a sensitivity of 61.88 mV/decade. The presented uric acid biosensor is highly stable, repeatable, and reproducible. The analytical practicality of the proposed uric acid biosensor is also monitored. The fabrication methodology is inexpensive, simple, and scalable, which ensures the capitalization of the developed uric acid biosensor for commercialization. Also, CuO material can be used for various applications such as solar cells, lithium ion batteries, and supercapacitors.

Discontinuous contact line motion of evaporating particle-laden droplet on superhydrophobic surfaces

The three-phase contact line motion on a superhydrophobic surface through particle-laden sessile droplet evaporation was investigated. Sample surfaces with micro- and nanoscale structures were generated by various durations of chemical treatment and SiO_{2} spherical particles with different sizes were used as additives of test liquid. The contact angle and contact radius profiles were studied, and the discontinuous motion of those profiles on micro- and nanostructured hierarchical surfaces was observed, while it was not observed on a nanostructured superhydrophobic surface. Suspensions with low particle concentration induced a relatively large contact radius jump compared to the high-concentrated condition; in contrast, the previous report showed the opposite trend for flat surfaces. In order to explain this result, a simple explanation was provided-that the stacked particles at the contact line region suppressed to the deformation of the liquid-vapor interface near the contact line. This is confirmed by side-view images of the deposition results because the contact line region after evaporation of the dense suspension showed a large contact angle compared to that of the diluted suspension. In addition, deposition at the contact line region was observed by scanning electron microscopy to discuss the effect of the characteristic length scale of the surface structure and particles on the contact line motion. We believe that these results will help one to understand the deposition phenomenon during particle-laden droplet evaporation on the superhydrophobic surface and its applications such as evaporation-driven materials deposition.

Underwater Curvature-Driven Transport between Oil Droplets on Patterned Substrates

Roughness contrast patterns were generated on copper surfaces by a simple one-step site-selective oxidation process using a felt-tipped ink pen masking method. The patterned surface exhibited strong underwater oil wettability contrast which allows oil droplet confinement. Oil droplets placed on two patterned smooth dots (reservoirs) connected by a patterned smooth channel will spontaneously exchange liquid as a result of Laplace pressure differences until their shapes have reached equilibrium. In our experiments, residual solubility of the oil in water was overcome by using saturated oil-in-water solutions as the aqueous medium. In the saturated solution, the dependence of pattern geometry and oil viscosity on transported volume and the flow rate in the underwater oil transport process was investigated for dichloromethane and hexadecane. Experimental results were in good agreement with a simple model for Laplace pressure-driven flow. Depending on droplet curvatures, oil can be transported from large to small reservoirs or vice versa. The model predictions enable the design of reservoir and channel dimensions to control liquid transport in the water-solid surface-oil system. The patterning technique was extended to more complex patterns with multiple reservoirs for smart oil separation and mixing processes. The concepts demonstrated in this study can be employed to seed droplet arrays with specific initial drop volumes and achieve subsequent droplet mixing at controlled flow rates for potential lab-on-a-chip applications ranging from oil-droplet-based miniature reactors and sensors to high-throughput assays.

Hierarchically structured multi-shell nanotube arrays by self-assembly for efficient water oxidation

Photosynthesis in plants occurs at structures which form by self-assembly under ambient conditions, while catalysts used for artificial photosynthesis normally need special conditions like high pressure or temperature. Herein, a facile and cost effective way for the synthesis of a highly complex and efficient oxygen evolution reaction (OER) catalyst, formed solely by self-assembly in solution, is presented. Without the need for any instrumentation except for a glass beaker, highly active nickel-iron-copper multi-shell nanotube arrays are produced by immersion of a copper plate in three different solutions. Cu(OH)₂ nanowires are first self-grown on a copper substrate in a basic solution and subsequently converted to novel iron-copper hydroxide nanotubes by immersion in an Fe³⁺ solution by a sacrificial template-accelerated hydrolysis mechanism. Finally, an additional layer of nickel nanosheets is added by treating in a nickel chemical bath. The resulting electrode shows a current density as high as 100 mA cm^-2 at an overpotential of 320 mV with a Tafel slope of 32 mV dec^-1, while also exhibiting long time stability. The use of inexpensive first-row transition metals, simple preparation methods with no energy consumption, the unique hierarchical structure of the nanosheet covered nanotubes, and the high catalytic performance are remarkable, and this study may therefore lead to more convenient and competitive routes for water splitting.

Brand new 1D branched CuO nanowire arrays for efficient photoelectrochemical water reduction

1D branched CuO nanowire arrays, with large surface area and efficient charge transfer, are reported as photocathodes for photoelectrochemical water reduction.

Controlled Wetting Properties through Heterogeneous Surfaces Containing Two-level Nanofeatures

Addressing the direct control of surface wettability has been a significant challenge for a variety of applications from self-cleaning surfaces to phase-change applications. Surface wettability has been traditionally modulated by installing surface nanostructures or changing their chemistry. Among numerous nanofabrication efforts, the chemical oxidation method is considered a promising approach because it allows cost-effective, quick, and direct control of the morphologies and chemical compositions of the grown nanofeatures. Despite the wide applicability of the surface oxidation method, the precise control of wetting behaviors through the growth of nanostructures has yet to be addressed. Here, we investigate the wetting characteristics of heterogeneous surfaces that contain two-level features (i.e., nanograsses and nanoflowers) with different petal shapes and structural chemistry. The difference in growth rates between nanograsses and nanoflowers creates a time-evolving morphology that can be classified by grass-dominated or flower-dominated regimes, which induces a wide range of water contact angles from 120 to 20°. The following study systematically quantifies the structural details and chemistry of nanostructures associated with their wetting characteristics. This investigation of heterogeneous surfaces will pave the way for selective growth of copper nanostructures and thus a direct control of surface wetting properties for use in future copper-based thermal applications.

Self-Assembled 3D Hierarchical Copper Hydroxyphosphate Modified by the Oxidation of Copper Foil as a Recyclable, Wide Wavelength Photocatalyst

In this work, three-dimensional flower-like and petal-like copper hydroxyphosphate Cu₅(OH)₄(PO₄)₂ (CHP) based on the self-assembly of numerous nanosheets has been successfully fabricated on a copper foil by a mild one-pot wet-chemical method without ligand assistance. This research contributes to the development of the method to change the morphology of the CHP active material by varying the degree of substrate oxidation. The two different CHP architectures were used to photocatalytically degrade rhodamine 6G (Rh 6G) under solar light, which can absorb wide-range light wavelength from the UV to the near-infrared region. They all exhibit high photocatalytic activity and good durability, which are potential candidates for high performance and recyclable wide wavelength photocatalysis.

Underwater Oil Droplet Splitting on a Patterned Template

Underwater oil droplets stretched and pinned by dual-dot oleophilic patterns on a superoleophobic substrate have been split into two nearly equal-volume daughter droplets using an underwater superoleophobic blade at substantially lower cutting speeds than reported in previous studies. A "liquid exchange model" based on Laplace pressure-driven liquid transport has been proposed to explain the mechanism of the underwater droplet split process. The dependence of droplet geometrical shape (curvature) and liquid properties (surface tension, viscosity) on the critical cutting speed that allows equal-volume split was investigated. Results demonstrate that critical cutting speed increases with increased curvature and surface tension of the split droplet, and decreases with increased droplet viscosity, which agrees with the proposed model. The ability to reproducibly split a single bulk oil droplet into daughter droplets with nearly equal volume facilitates the development of new functions for underwater microreactors.

Quantifying bonding strength of CuO nanotubes with substrate using the nano-scratch technique

CuO is a narrow bandgap semiconductor demonstrating applications in/as catalysts, gas sensors, adsorbents, and superconductors, and as electrodes of photocells, super-capacitors, and lithium-ion batteries. One-dimensional (1D) CuO nanostructures are of particular interest in most of these device applications, owing to their huge surface area. Strong bonding between nanomaterials and substrate is essential for extended device life. Hence, knowledge about the strength of the nanomaterial-substrate bond is highly desired. In this research work, CuO nanotubes were synthesized directly on a Cu substrate, and its adhesion strength was quantified using the nano-scratch-based technique. The adhesion energy of CuO nanotubes (for 7 h of reaction period) on the Cu substrate was measured to be 82 Jm(-2). The bonding strength can be correlated with the structure of the material. Results of this research will be valuable in analyzing and improving the lifetime of CuO nanotube-based devices, and the technique could be further extended to other 1D transition metal oxide nanostructures.

Partial conversion of current collectors into nickel copper oxide electrode materials for high-performance energy storage devices

A novel substrate sacrifice process is proposed and developed for converting part of a current collector into supercapacitor active materials, which provides a new route in achieving high energy density of supercapacitor device. Part of a copper foam current collector is successfully converted into highly porous nickel copper oxide electrode for light- and high-performance supercapacitors. Remarkably, this strategy circumvents the problem associated with poor contact interface between electrode and current collector. Meanwhile, the overall weight of the supercapacitor could be minimized. The charge transfer kinetics is improved while the advantage of the excellent mechanical properties of metal current collector is not traded off. By virtue of this unique current collector self-involved architecture, the material derived from the current collector manifests large areal capacitance of 3.13 F cm(-2) at a current density of 1 A g(-1). The capacitance can retain 2.97 F cm(-2) at a much higher density (4 A g(-1)). Only a small decay of 6.5% appears at 4 A g(-1) after 1600 cycles. The strategy reported here sheds light on new strategies in making additional use of the metal current collector. Furthermore, asymmetric supercapacitor using both solid-state gel electrolyte and liquid counterpart are obtained and analyzed. The liquid asymmetric supercapacitor can deliver a high energy density up to 0.5 mWh cm(-2) (53 Wh kg(-1)) at a power density of 13 mW cm(-2) (1.4 kW kg(-1)).

Flexible 3D porous CuO nanowire arrays for enzymeless glucose sensing: in situ engineered versus ex situ piled

Convenient determination of glucose in a sensitive, reliable and cost-effective way has aroused sustained research passion, bringing along assiduous investigation of high-performance electroactive nanomaterials to build enzymeless sensors. In addition to the intrinsic electrocatalytic capability of the sensing materials, electrode architecture at the microscale is also crucial for fully enhancing the performance. In this work, free-standing porous CuO nanowire (NW) was taken as a model sensing material to illustrate this point, where an in situ formed 3D CuO nanowire array (NWA) and CuO nanowires pile (NWP) immobilized with polymer binder by conventional drop-casting technique were both studied for enzymeless glucose sensing. The NWA electrode exhibited greatly promoted electrochemistry characterized by decreased overpotential for electro-oxidation of glucose and over 5-fold higher sensitivity compared to the NWP counterpart, benefiting from the binder-free nanoarray structure. Besides, its sensing performance was also satisfying in terms of rapidness, selectivity and durability. Further, the CuO NWA was utilized to fabricate a flexible sensor which showed excellent performance stability against mechanical bending. Thanks to its favorable electrode architecture, the CuO NWA is believed to offer opportunities for building high-efficiency flexible electrochemical devices.

Redox reaction mediated direct synthesis of hierarchical flower-like CuO spheres anchored on electrospun poly(vinylidene difluoride) fiber surfaces at low temperatures

Flower-like CuO spheres anchored on electrospun PVDF fiber surfaces as catalytic membranes for the photodegradation of rhodamine B aqueous solutions.

Synthesis of Cu(OH)2 and CuO nanotubes arrays on a silicon wafer

Growth of Cu(OH)₂ and CuO nanotubes having a diameter of 100 nm on a silicon wafer.

Solution synthesis of metal oxides for electrochemical energy storage applications

This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.

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.

Significant enhancement of optical absorption through nano-structuring of copper based oxide semiconductors: possible future materials for solar energy applications

An excellent optical absorption coefficient twice that of Si is successfully achieved in a nanostructured phase mixture of copper based oxide semiconductors.

Facile synthesis of self-assembled mesoporous CuO nanospheres and hollow Cu2O microspheres with excellent adsorption performance

Self-assembly CuO nanospheres (CuONSs) and hollow Cu₂O microspheres (Cu₂OMSs) show an excellent adsorption performance for anionic dyes in water.

Synthesis of novel CuO nanosheets and their non-enzymatic glucose sensing applications

In this study, we have developed a sensitive and selective glucose sensor using novel CuO nanosheets which were grown on a gold coated glass substrate by a low temperature growth method. X-ray differaction (XRD) and scanning electron microscopy (SEM) techniques were used for the structural characterization of CuO nanostructures. CuO nanosheets are highly dense, uniform, and exhibited good crystalline array structure. X-ray photoelectron spectroscopy (XPS) technique was applied for the study of chemical composition of CuO nanosheets and the obtained information demonstrated pure phase CuO nanosheets. The novel CuO nanosheets were employed for the development of a sensitive and selective non-enzymatic glucose sensor. The measured sensitivity and a correlation coefficient are in order 5.20 × 10² µA/mMcm² and 0.998, respectively. The proposed sensor is associated with several advantages such as low cost, simplicity, high stability, reproducibility and selectivity for the quick detection of glucose.

Metal corrosion for nanofabrication

The annual cost of corrosion has been increasing globally, and it has now reached beyond 3% of the world's gross domestic product. It remains a challenge to reduce or prevent unwanted corrosion effectively after many decades of effort. Nowadays, more efforts are being made to develop anti-corrosion platforms for decreasing the huge cost of corrosion. In parallel, it is also highly expected to be able to use corrosion for producing useful materials with reduced energy consumption. In this review, recent progress in how methods for controlling metal corrosion can be used to produce structure-diversified nanomaterials are summarized along with a presentation of their applications. As a valuable addition to the scientists' toolbox, metal corrosion strategies can be applied to different metals and their alloys for the production of various nanostructured materials; this also provides insights into how metal corrosion can be further prevented and into how corrosion wastage can be reduced.

Methodology for imaging nano-to-microscale water condensation dynamics on complex nanostructures

A better understanding of the role that nanoscale surface chemical heterogeneities and topographical features play in water droplet formation is necessary to improve design and robustness of nanostructured superhydrophobic surfaces as to make them fit for industrial applications. Lack of an imaging method capable of capturing the water condensation process on complex nanostructures with required magnification has thus far hindered experimental progress in this area. In this work, we demonstrate that by transferring a small part of a macroscale sample to a novel thermally insulated sample platform we are able to mitigate flooding and electron heating problems typically associated with environmental scanning electron microscopy of water condensation. We image condensation dynamics on individual complex particles and a superhydrophobic network of nanostructures fabricated from low thermal conductivity materials with an unobstructed 90° perspective of the surface-to-water interface with field of view as small as 1 μm(2). We clearly observe the three-stage drop growth process and demonstrate that even during late stages of the droplet growth the nearly spherical drop remains in a partially wetting Wenzel state.