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To improve the mechanical properties and corrosion resistance of the hydraulic column in the mine, a semiconductor fiber-coupled laser was used to laser-clad iron-based alloy powder on a 27SiMn steel substrate (SUB). The microstructure, mechanical properties, and corrosion resistance of the obtained cladding layer (CL) were studied based on experiments. Results show that equiaxed grains at the top of the CL are fine and tightly arranged. Compared with the SUB, the CL average microhardness is increased by 0.3 times, the average friction coefficient is decreased by 0.12, and the wear amount is significantly reduced. The bonding strength between the CL and the SUB is good, and the tensile strength is increased by 10.82%. Compared with the SUB, the mechanical properties and corrosion resistance of the CL are better. The research has an important guiding significance for the practice of hydraulic column repair and strengthening engineering.

Dendritic growth of the metallic lithium anode cannot be fully avoided for prolonged cycling due to the inherent thermodynamic and kinetic tendency, which causes serious safety issues. Here, we strategically control the lithium metal growth direction by designing a three-dimensional porous host with lithiophilic-lithiophobic characterized ligaments. Therefore, lithium metal can only nucleate on the lithiophilic back surface and grow toward the direction away from the separator. Such ‘backside-growth’ can ensure safe battery operation even when lithium dendrites exist. For a proof-of-concept study, highly lithiophilic gold layer is sputtered on backside surface of each copper foam ligament. During lithium plating, lithium nucleates on the lithiophilic backside and keeps growing conformably from the existing nuclei towards the opposite direction to the separator, and eventually forms a lithium-metal layer with highly compacted self-aligned columnar structure. The novel approach controls lithium deposition in two aspects simultaneously: growth direction and morphology. Notably, the featured surface dendrite-free anode exhibits ultra-long-term stable cycling with a high Coulombic efficiency (e.g., 95.0% after 300 cycles, 0.5 mA cm−2, 1 mA h cm−2). This work may not only pave ways for building ultimate safe lithium batteries but also conceptually provides new opportunities for other metal anodes.

LixMnO2 nanowires with controllable morphology and excellent electrochemical performance are synthesized by a hydrothermal method with tunable lithium contents. Both double layer capacitive process and diffusion-controlled Faradaic process play roles in the charging-discharging process. Aqueous Li-ion hybrid supercapacitors are assembled using LixMnO2 nanowires as the positive electrode and activated carbon as the negative electrode. The hybrid devices deliver high energy density of 88.56 Wh kg−1 and 25.2 Wh kg−1 at the high power density of 151.8 W kg−1 and 2155.8 W kg−1, respectively. The device also shows superb cycling life with capacitance retention of 95.2% after 10,000 cycles and 85.2% after 20,000 cycles.

Three-dimensional (3D) porous N-doped carbon nanoflake structures decorated with in situ formed Ag nanoparticles (Ag-NCNS) have been synthesized for the first time by a feasible salt-assisted polym...

Low ionic conductivity and poor interfacial compatibility between lithium electrodes and Li7P3S11 sulfide solid electrolytes are the greatest challenges for all-solid state lithium-sulfur batteries. Herein, we introduce a hybrid solid electrolyte with Li7P3S11 being wrapped with polyethylene oxide-LiClO4 (PEO-LiClO4). As served as conductive bridge between Li7P3S11 particles, PEO-LiClO4 would provide Li+ transition paths between Li7P3S11 particles, thus successfully improve its ionic conductivity. Moreover, the polymer layer of PEO-LiClO4 can isolate lithium metal and Li7P3S11 solid electrolyte, suppressing the reaction between lithium electrode and Li7P3S11 electrolyte. Therefore, hybrid solid electrolyte Li7P3S11-PEO-LiClO4 shows excellent interfacial compatibility with lithium foil. Lithium-sulfur battery with the hybrid electrolyte Li7P3S11-PEO-LiClO4 exhibits much improved electrochemical performance with better cycling stability and higher Coulombic efficiency.

Lithium–oxygen batteries (LOBs) have attracted increasing interest because of their superior theoretical specific energy. However, the stability of lithium metal anode is one of the obstacles limiting their practical applications. Here, we introduce an artificial Li3PO4 solid electrolyte interphase (SEI) film to protect the lithium anode in LOB with LiI/LiNO3/DMSO (dimethyl sulfoxide) electrolyte. The Li3PO4-protected Li anode exhibits excellent electrochemical stability during the Li stripping/plating process and leads to a relatively uniform and featureless surface in LOB after cycling. Our research demonstrates that superior electrochemical performance can be achieved in the Li–O2 battery with the synergistic combination of the DMSO-based electrolyte, the LiI redox mediator, and the Li3PO4-protected Li anode. The LOB with a Li3PO4-protected Li anode exhibits a prolonged cycling life span of 152 cycles with a fixed capacity of 1000 mA h g–1 at 2 A g–1. The results in this work provide knowledge for the ...

Uniform hierarchical Na3V1.95Mn0.05(PO4)2F3@C hollow microspheres composed of nanoplates and nanoparticles were successfully synthesized by a one-step polyol-assisted hydrothermal method combined with chemical vapour deposition (CVD). We also investigated the formation mechanism of the hierarchical hollow microspheres and it was found that both tetraethylene glycol and citric acid play important roles in the formation of the hierarchical hollow microspheres. Na3V1.95Mn0.05(PO4)2F3@C showed an initial reversible capacity of 122.9 mA h g−1 and the discharge capacity of 109 mA h g−1 was maintained with a coulombic efficiency of 99.1% after 500 cycles. The unique architecture, enhanced electronic conductivity and improved diffusion coefficient of sodium ions for Na3V2(PO4)2F3 by Mn2+ doping as well as carbon coating account for the enhanced electrochemical properties. Therefore, we present an approach to design a tunable structure for multi-element compounds with enhanced electrochemical performance as a promising cathode material for practical applications.

Programmable positioning of 2 μm polystyrene (PS) beads with single particle precision and location selective, "on-demand", particle deposition was demonstrated by utilizing patterned electrodes and electrophoretic deposition (EPD). An electrode with differently sized hole patterns, from 0.5 to 5 μm, was used to illustrate the discriminatory particle deposition events based on the voltage and particle-to-hole size ratio. With decreasing patterned hole size, a larger electric field was required for a particle deposition event to occur in that hole. For the 5 μm hole, particle deposition began to occur at 10 V/cm where as an electric field of 15 V/cm was required for particles to begin depositing in the 2 μm holes. The likelihood of particle depositions continued to increase for smaller sized holes as the electric field increased. Eventually, a monolayer of particles began to form at approximately 20 V/cm. In essence, a voltage threshold was found for each hole pattern of different sizes, allowing fine adjustments in pattern hole size and voltage to control when a particle deposition event took place, even with the patterns on the same electrode. This phenomenon opens a route toward controlled, multimaterial deposition and assembly onto substrates without repatterning of the electrode or complicated surface modification of the particles. An analytical approach using the theories for electrophoresis and dielectrophoresis found the former to be the dominating force for depositing a particle into a patterned hole. Ebeam lithography was used to pattern spherical holes in precise configurations onto electrode surfaces, where each hole accompanied a polystyrene (PS) particle placement and attachment during EPD. The versatility of e-beam lithography was utilized to create arbitrary pattern configurations to fabricate particle assemblies of limitless configurations, enabling fabrication of unique materials assemblies and interfaces.

We report on an innovative approach to fabricate lithium ion battery anodes based on optimized growth of hybrid carbon nanotube (CNT) and graphene nanostructures directly on copper foil substrates by an ambient pressure chemical vapor deposition process. Seamlessly connected graphene and CNT pillars provide a relatively strong active material-current collector integrity, which facilitates charge transfer in the system. This innovative architecture provides a binder-free technique for preparing electrodes for lithium ion batteries.

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Interest in graphene as a two-dimensional quantum-well material for energy applications and nanoelectronics has increased exponentially in the last few years. The recent advances in large-area single-sheet fabrication of pristine graphene have opened unexplored avenues for expanding from nanoto meso-scale applications. The relatively low level of absorptivity and the short lifetimes of excitons of single-sheet graphene suggest that it needs to be coup led with light sensitizers in order to explore its feasibility for photonic applications, such as solar-energy conversion. Red-emitting CdSe quantum dots are employed for photosensitizing single-sheet graphene with areas of several square centimeters. Pyridine coating of the quantum dots not only enhances their adhesion to the graphene surface, but also provides good electronic coup ling between the CdSe and the two-dimensional carbon allotrope. Illumination of the quantum dots led to injection of n-carrier in the graphene phase. Time-resolved spectroscopy reveals three modes of photoinduced electron transfer between the quantum dots and the graphene occurring in the femtosecond and picosecond time-domains. Transient absorption spectra provide evidence for photoinduced hole-shift from the CdSe to the pyridine ligands, thereby polarizing the surface of the quantum dots. That is, photoinduced electrical polarization, which favors the simultaneous electron transfer from the CdSe to the graphene phase. These mechanistic insights into the photoinduced interfacial charge transfer have a promising potential to serve as guidelines for the design and development of composites of graphene and inorganic nanomaterials for solar-energy conversion applications.

Large-area flexible and transparent optoelectronic devices were fabricated through non-covalent interaction between CdSe/ZnS core/shell quantum dots and single layer graphene. The photo-induced charge transfer was confirmed by fluorescence quenching experiments and photoconductivity measurements. Quantum dots decorated graphene device exhibits excellent photo-switching property making it promising as a long wavelength sensitive photodetector. 1-D (graphene)/ 0-D (QD) hybrid structure facilitates electron transfer faster. When used as photoelectrochemical cell anode, this hybrid material displays both high photon to current conversion efficiency (IPCE) and fast photo-switch response.

Electrochemical capacitors are promising alternative energy storage systems dueto their relatively fast rate of energy storage and delivery. We describe a simple andscalable method to grow three-dimensional (3D) graphene/multi-wall carbon nanotubes(MWNTs) hybrid nanostructure on industrially used foamed metal foils (nickel foam) viaa one-step ambient pressure chemical vapor deposition (APCVD). The as-growngraphene/MWNTs carbon nanostructure foam demonstrates a homogeneous and denselypacked hierarchical nanostructure and possesses a high surface area which can bepotentially used for the electrodes of energy storage devices such as supercapacitors andbattery. Symmetrical electrochemical double-layer capacitors (EDLCs) ofgraphene/MWNTs nanostructures shows a high specific capacitance of 286 F g-1 whichleads to an energy density of 39.72 Wh kg-1 and a superior power density of up to 154.67kW kg-1. Moreover, the capacitance retention of ~100% after 11000 charge-dischargecycles demonstrates the high stability of the material for electrodes of supercapacitor.These merits enable the innovative 3D hierarchical graphene/MWNTs foam to serve asEDLC electrodes, resulting in energy storage devices with high stability and powerdensity.

Supercapacitors are promising alternative energy storage systems due to their relatively fastrate of energy storage and delivery. We describe a simple and scalable method to fabricatethree-dimensional (3D) few-layer graphene/multi-walled carbon nanotube (MWNT) hybridnanostructures on industrial grade metal foam foils (nickel foam) via a one-step ambientpressure chemical vapor deposition (APCVD) process. The as-grown few-layer graphene/MWNTnanocarbon foams are in the form of a homogeneous and densely packed hierarchicalnanostructures and possess a very large surface area of 743 m 2 g 1 . Symmetrical electro-chemical double-layer capacitors (EDLCs) of 3D hybrid hierarchical few-layer graphene/MWNTnanostructures show a high specific capacitance of 286 F g 1 which leads to an energy density of39.72 Wh kg 1 and a superior power density of up to 154.67 kW kg . Moreover, the capacitanceretention of 99.34% after 85000 charge–discharge cycles demonstrates the very high stability ofthe electrode architectures for supercapacitors. These merits enable the innovative 3Dhierarchical few-layer graphene/MWNT foam to serve as high performance EDLC electrodes,resulting in energy storage devices with very high stability and power density.& 2012 Elsevier Ltd. All rights reserved.2211-2855/$-see front matter & 2012 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.nanoen.2012.10.001

Three-dimensional (3D) chrysanthemum-like carbon nanofiber (CCNF) foam architectures were synthesized on highly porous nickel foam via a one-step ambient pressure chemical vapor deposition process by introducing a mixture of precursor gases (H2 and C2H2). The as-synthesized 3D foam architectures were characterized by scanning electron microscopy and transmission electron microscopy, which demonstrate high porosity and a densely packed nature of the hierarchical carbon nanostructures. Symmetrical electrochemical double-layer capacitors were fabricated using electrodes based on the CCNF foam architectures. Cyclic voltammetry, charge–discharge measurements, and electrochemical impedance spectroscopy were conducted to determine the performance metrics. The supercapacitors (SCs) demonstrate a high areal capacitance of 1.37 F/cm2 (gravimetric specific capacitance: 23.83 F/g), which leads to superior values for per area energy density (0.19 Wh/cm2) and power density (141.77 W/cm2). In addition, capacitance retention of ∼100% over 13,000 charge–discharge cycles demonstrates the high electrochemical stability of this type of carbon nanostructure foam for high areal capacitance SCs.

We report on the successful synthesis of a graphene–carbon nanotube (CNT) hybrid architecture by a parallel chemical vapor deposition (CVD) of the two carbon allotropes. The carbon hybrid is a three-dimensional (3D) nanostructure with tuneable architecture comprising vertically grown CNTs as pillars and a large-area graphene plane as the floor. The formation of CNTs and graphene occurs simultaneously in a single CVD growth that we describe as a synchronous synthesis method. Unique nature of the fabrication approach contributes significantly to the quality and composure of final nanohybrid. Detailed characterization elucidates the cohesive structure and robust contact between the graphene floor and the CNTs in the hybrid structure. The functionality of the synthesized graphene hybrid structure has been demonstrated by its incorporation into a supercapacitor cell. Our fabrication approach provides an attractive pathway for the fabrication of novel 3D hybrid nanostructures and efficient device integration.

We describe the synthesis and fabrication of a graphene oxide (GO) and single-walled carbon nanotube (SWCNT) composite ink (GO–SWCNT ink) for electrochemically stable supercapacitors. Atomic force microscopy and scanning electron microscopy studies demonstrate that the obtained GO flakes are single layer with size distribution from 100 nm to 20 μm. SWCNTs are dispersed using a GO aqueous solution (2 mg/mL) with sonication support to achieve a SWCNT concentration of 12 mg/mL, the highest reported value so far without surfactant assistance. Raman spectroscopy studies indicate that the full-width at half-maximum of the G band increases with the mixing of SWCNT and GO indicating that electronic structure changes via π–π interactions of GO sheets and SWCNTs. Paper-based electrodes of supercapacitor were conveniently fabricated with GO–SWCNT composite ink via a dip casting method. By using different concentrations of SWCNT in the ink, the paper electrodes provide different capacitance values. The highest value of specific capacitance reaches 295 F/g at a current density of 0.5 A/g with a GO/SWCNT weight ratio of 1:5. The cycling stability for the GO–SWCNT paper electrode supercapacitors indicates capacitance retention of 85% over 60,000 cycles.

In order to investigate the effects of process parameters on the quality of laser cladding layer, Co-based alloy laser cladding experiments based on orthogonal method was performed on the 304 stainless steel by high power diode laser (HPDL). The results show that the laser scanning speed has the most significant influence on the width, height and depth of laser cladding layer, and the powder feeding rate has the most important influence on the hardness of laser cladding layer. For the sake of getting optimum process parameters and reducing the times of process experiments in practical engineering application, a back propagation (BP) neural network model was established to predict the optimum process parameters. The calculation and predication results show a good agreement with the experimental results. The research results have both significant reference value and guidance meaning in processing parameters of Co-based alloy cladding by a high power diode laser in the application.

Carbon-based nanomaterials such as single-walled carbon nanotubes and reduced graphene oxide are currently being evaluated for biomedical applications including in vivo drug delivery and tumor imaging. Several reports have studied the toxicity of carbon nanomaterials, but their effects on human male reproduction have not been fully examined. Additionally, it is not clear whether the nanomaterial exposure has any effect on sperm sorting procedures used in clinical settings. Here, we show that the presence of functionalized single walled carbon nanotubes (SWCNT-COOH) and reduced graphene oxide at concentrations of 1–25 μg/mL do not affect sperm viability. However, SWCNT-COOH generate significant reactive superoxide species at a higher concentration (25 μg/mL), while reduced graphene oxide does not initiate reactive species in human sperm. Further, we demonstrate that exposure to these nanomaterials does not hinder the sperm sorting process, and microfluidic sorting systems can select the sperm that show low oxidative stress post-exposure.

The utilization of fluorescence quenching microscopy (FQM) for quick visualization of chemical functionalization in relatively large regions of graphene, grown via chemical vapor deposition (CVD), is discussed. Through reactive ion plasma etching, patterns of p-type CVD-grown graphene functionalized with fluorine are generated. 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) is used as the fluorescent agent. The emission of DCM is quenched to a different extent by fluorinated and pristine graphene, which provides the fluorescence-imaging contrast essential for this metrology. To probe the functionalized surface patterns with DCM, the dye is dispersed in polymethylmethacrylate (PMMA) then the graphene surface is coated, forming a 30-nm-thick DCM-PMMA layer. Fluorescence images of dye-coated graphene distinctly reveal the difference between the chemically treated and as-grown regions. The pristine graphene quenches the DCM emission more efficiently than the fluorinated graphene. Therefore, the regions with pristine graphene appear darker on the fluorescence images than the regions with fluorinated graphene, enabling large-scale mapping of the functionalized regions in CVD grown graphene sheets Due to its simplicity and consistent results, FQM is now poised for widespread adoption by graphene manufacturers as a basis for facile and high throughput metrology of large-scale graphene sheets.

Fluorescence Quenching Microscopy has been shown to be an effective means of characterizing graphene on the macroscale. Centimeter-scale CVD-grown pristine and doped graphene were manufactured in a high temperature (1000°C) furnace on pristine copper substrates. The copper was then etched away in a FeCl3solution and the graphene was coated with DCM-based fluorescent dye before being imaged in a fluorescence microscope. The fluorescence image was then image-processed using modified Matlab software. The resulting image showed clear contrast between the pristine graphene sheet and defects on the graphene surface, which revealed that fluorescence microscopy could determine the quality of a large region of graphene. Also, significant contrast was identified between single-layer and multi-layer regions, showing that this technique is also effective at determining the degree of uniformity within a graphene sample. Lastly, the fluorescence images showed contrast between doped and undoped regions of graphene.

Supercapacitors are promising candidates for alternative energy storage applications since they can store and deliver energy at relatively high rates. In this work, we integrated large area chemical vapor deposition (CVD) grown three dimensional graphene heterostructures with high capacitance metal oxides (MnO2) to fabricate highly conductive, large surface-area composite thin films. Uniform, large area 3D graphene heterostructures layers were produced by a one-step CVD on nickel foams. MnO2 nanowires were deposited on the as-obtained 3D graphene heterostructures film by a simple chemical bath depostion process. The oxide loading of the 3D graphene/MWNTs/MnO2 nanowires (GMM) composite films can be simply controlled by deposition time and nanowire solution concentration. The surface morphology was investigated by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), and Energy-dispersive X-ray spectroscopy (EDS) was performed to characterize the MnO2on the surface of the film. By introducing the fast surface redox reactions into the graphene heterostructures film via integrating pseudocapacitive material like MnO2, the capacitive ability of the system enhanced dramatically. Supercapacitor was fabricated based on the 3D graphene heterostructures /MnO2 hybrid film electrodes; the measurements of cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) are conducted to determine its performance for the electrodes of supercapacitors.

Graphene, with unique electrical, optical and mechanical properties is a promising material in industrial applications, such as batteries, supercapacitors, transistors and semiconductor devices. These potential applications of graphene have motivated the development of large-scale synthesis of graphene on copper substrates by chemical vapor deposition (CVD). To enable practical applications of large-area, high quality graphene layers at the centimeter and wafer scales, process control needs to be implemented for optimizing the morphology and electrical properties and enable repeatable growth-cycle of graphene layers for process-line implementation. Here we investigate the effects of process quartz-tube position on the structural properties of graphene. Furthermore, we describe a procedure for process optimization of the growth parameters. Graphene is grown on copper foils by CVD, and transferred to the SiO2/Si and glass substrates. The detailed characterization of the graphene layers are conducted using Raman spectroscopy, optical microscopy (OM), scanning electron microscopy (SEM) and UV-vis spectroscopy. The experimental results show that the position of copper foil into the quartz tube plays a significant role in the Raman features of the graphene, and influences the optical, morphology and surface properties of graphene layers. We believe that these results will be useful for determining the optimum processing conditions of high quality graphene layers at the centimeter and wafer scales.

In this work, we demonstrated the growth of three dimensional graphene/carbon nanotubes hybrid carbon nanostructures on metal foam through a one-step chemical vapor deposition (CVD). The as-grown three dimensional carbon nanostructure foams can be potentially used as the electrodes of energy storage devices such as supercapacitors and batteries. During the CVD process, the carbon nanostructures are grown on highly porous nickel foam to form a high surface area 3-D carbon nanostructure by introducing a mixture precursor gases (H2, C2H2). The surface morphology was investigated by scanning electron microscopy (SEM) and the results demonstrated relatively homogeneous and densely packed 3-D carbon nanostructure. The quality was characterized by Raman spectroscopy. To further increase the capacitive capability the supercapacitors were fabricated based on the electrodes of carbon nanostructure foam and cyclic voltammetry, charge-discharge, and electrochemical impedance spectroscopy (EIS) were conducted to determine their performance.

A high-throughput metrology method for measuring the thickness and uniformity of entire large-area chemical vapor deposition-grown graphene sheets on arbitrary substrates is demonstrated. This method utilizes the quenching of fluorescence by graphene via resonant energy transfer to increase the visibility of graphene on a glass substrate. Fluorescence quenching is visualized by spin-coating a solution of polymer mixed with fluorescent dye onto the graphene then viewing the sample under a fluorescence microscope. A large-area fluorescence montage image of the dyed graphene sample is collected and processed to identify the graphene and indicate the graphene layer thickness throughout the entire graphene sample. Using this metrology method, the effect of different transfer techniques on the quality of the graphene sheet is studied. It is shown that small-area characterization is insufficient to truly evaluate the effect of the transfer technique on the graphene sample. The results indicate that introducing a drop of acetone or liquid poly(methyl methacrylate) (PMMA) on top of the transfer PMMA layer before soaking the graphene sample in acetone improves the quality of the graphene dramatically over immediately soaking the graphene in acetone. This work introduces a new method for graphene quantification that can quickly and easily identify graphene layers in a large area on arbitrary substrates. This metrology technique is well suited for many industrial applications due to its repeatability and flexibility.

We describe the fabrication of highly sensitive graphene based field effect transistor (FET) biosensors with a cost-effective approach and their application in label-free Deoxyribonucleic acid (DNA) detection. Chemical vapor deposition (CVD) grown graphene layers were used to achieve mass production of FET devices via conventional photolithographic patterning. Non-covalent functionalization of the graphene layer with 1-Pyrenebutanoic acid succinimidyl ester ensures high conductivity and sensitivity of the FET device. The present device could reach a detection limit as low as 3 x 10(-9) M.

Deoxyribonucleic acids (DNA) provide exciting opportunities as templates in self assembled architectures and functionality in terms of optical and electronic properties. In this study, we investigate the effects of DNA and metalized DNA sequences in polymer fullerene bulk-heterojunction (BHJ) solar cells. These effects are characterized via optical, quantum efficiency and current-voltage measurements. We demonstrate that by placing on the hole collection side of the active layer, DNA and Pt-DNA sequences lead to an increase in the power conversion efficiency (POE) by %16 and %30, respectively. Then, we examine the metallization process with SEM and AFM images and optimized the metallic cluster formation on DNA by changing the duration of steps in the process. Furthermore, we studied the electrical charge characteristics of our DNA layer by using capacitance voltage (C-V) measurements to explain the increase in hole collection. The shift in the C-V measurements showed that spray coated DNA formed a negatively charged layer which can increase the hole collection on the cathode side.

Thermal stability of LiPF 6 -based electrolyte (1 M LiPF 6 /EC + DMC) was studied by in-situ FTIR spectroscopy and C80 calorimetry, which indicated that the electrolyte underwent furious polymerization and decomposition reactions and sharp heat flow was generated below 225 °C. The thermal stability of the electrolyte in contact with various delithiated cathodes (Li x CoO 2 , Li x Ni 0.8 Co 0.15 Al 0.05 O 2 , Li x Ni 1/3 Co 1/3 Mn 1/3 O 2 , Li x Mn 2 O 4 , Li x Ni 0.5 Mn 0.5 O 2 , Li x Ni 0.5 Mn 1.5 O 4 and Li x FePO 4 ) was also investigated by C80 calorimetry. The results show that the cathode materials except for Li x FePO 4 usually have an enhancement effect on the decomposition of the electrolyte, but Li x FePO 4 exhibits a suppression effect on the reactions of the electrolyte. Li x FePO 4 is found to be with excellent thermal stability. Among the other cathodes, Li x CoO 2 , Li x Ni 0.8 Co 0.15 Al 0.05 O 2 , Li x Ni 0.5 Mn 0.5 O 2 and Li x Ni 0.5 Mn 1.5 O 4 promote the decomposition of electrolyte by releasing oxygen and thus considered not favorable for safety, but Li x Ni 1/3 Co 1/3 Mn 1/3 O 2 with a lesser reaction heat and Li x Mn 2 O 4 with even less heat flow in the low temperature range (50–225 °C) are believed as promising cathodes for better safety. By comparing X-ray diffraction (XRD) patterns of these cathode materials at room temperature and those heated to 300 °C in the presence of the electrolyte, we have found that Li x FePO 4 only has experienced tiny structure change, which is greatly different from the other cathode materials.

A family of functional metal oxide nanotubes such as TiO2, Fe2O3, SnO2, ZrO2, and SnO2@Fe2O3 composite can be successfully fabricated by using highly active carbonaceous nanofibres as templates, which are synthesized via a hydrothermal approach. Compared with the previous strategy of using carbon nanotubes as templates, the carbonaceous nanofibres synthesized by the hydrothermal approach have higher reactivity, thus making them more suitable for templating synthesis of a variety of metal oxide nanotubes. This general method can be further developed to synthesize uniform ternary oxide nanotubes such as BaTiO3 and metal oxide composite nanotubes. The gas sensitivity of SnO2nanotubes synthesized by this approach has showed higher sensitivity, which exemplifies the distinct properties of such 1D hollow nanostructures. These uniform nanotubes might find potential applications in fields such as catalysis, chemical/biological separation, and sensing.

Biocompatible and green luminescent monodisperse silver/phenol formaldehyde resin core/shell spheres with controllable sizes, in the range of 180 to 1000 nm, and interesting architectures (centric, eccentric, and coenocytic core/shell spheres) have been synthesized by a facile one-step hydrothermal approach. These spheres can be used as bioimaging labels for human lung cancer H1299 cells. The results demonstrate that the nanoparticles can be internalized into cells and exhibit no cytotoxic effects, showing that such novel biocompatible core/shell structures can potentially be used as in vivo bioimaging labels. This facile one-pot polymerization and encapsulation technique may provide a useful tool to synthesize other core/shell particles that have potential application in biotechnology.

Dimethyl methylphosphonate (DMMP) was used as a cosolvent to reformulate the nonflammable electrolyte of 1 M LiPF 6 /EC + DEC + DMMP (1:1:2 wt.) in order to improve the safety characteristics of lithium-ion batteries. The flammability, cell performance, low-temperature performance and thermal stability of the DMMP-based electrolyte were compared with the electrolyte of 1 M LiPF 6 /EC + DEC (1:1 wt.). The nonflammable electrolyte exhibits good oxidation stability at the LiCoO 2 cathode and poor reduction stability at the mesocarbon microbead (MCMB) and surface-modified graphite (SMG) anodes. The addition of vinyl ethylene carbonate (VEC) to the DMMP-based electrolyte provided a significant improvement in the reduction stability at the carbonaceous electrodes. Furthermore, it was found that the addition of DMMP resulted in optimized low-temperature performance and varied thermal stability of the electrolytes. All of the results indicated the novel DMMP-based electrolyte is a promising nonflammable electrolyte to resolve the safety concerns of lithium-ion batteries.

Solid solutions of Ce1-xNdxO2-x/2 (0.05

Owing to their simple chemistry and structure, controllable geometry, and a plethora of unusual yet exciting transport properties, carbon nanotubes (CNTs) have emerged as exceptional channels for fundamental nanofluidic studies, as well as building blocks for future fluidic devices that can outperform current technology in many applications. Leveraging the unique fluidic properties of CNTs in advanced systems requires a full understanding of their physical origin. Recent advancements in nanofabrication technology enable nanofluidic devices to be built with a single, nanometer-wide CNT as a fluidic pathway. These novel platforms with isolated CNT nanochannels offer distinct advantages for establishing quantitative structure–transport correlations in comparison with membranes containing many CNT pores. In addition, they are promising components for single-molecule sensors as well as for building nanotube-based circuits wherein fluidics and electronics can be coupled. With such advanced device architecture, molecular and ionic transport can be manipulated with vastly enhanced control for applications in sensing, separation, detection, and therapeutic delivery. Recent achievements in fabricating isolated-CNT nanofluidic platforms are highlighted, along with the most-significant findings each platform enables for water, ion, and molecular transport. Furthermore, the implications of these findings and remaining open questions on the exceptional fluidic properties of CNTs are also discussed.

Simulations and experimental studies have reported an unusually high ionic conductance in carbon nanotubes (CNTs) nanochannels. The origin of this phenomenon is, however, poorly-understood: literature reports often disagree in the magnitude of the different transport mode contributions to the measured ionic current and even in what ions are actually carrying the current; moreover, results obtained with single pore measurements differ frequently from those with membranes containing billions of open CNT channels, i.e. the average CNT behavior. Toward shedding light on these phenomena, we fabricated a novel platform having vertically-aligned sub-5nm carbon nanotubes as nanofluidic channels, the number of which can be controlled from one to billions. By employing this platform with only one or a few open CNTs, we observed giant ionic currents in CNT channels and a power-law increase of conductance with KCl concentration (G ∼ cn, n=0.1-0.4), a dependence that seems to be unique of CNT pores. To understand and quantify electro-osmotic flow in CNT pores (which has been proposed as the transport mode responsible for the giant ionic currents in CNTs), we investigated translocation of neutral molecules in a single CNT nanochannel with the resistive pulse technique. Furthermore, we studied the effect of solution pH, matrix type, and CNT diameter on the magnitude and the on the electrolyte concentration based power law dependence of the conductance. Implications of our findings on the physics of electric-field-driven ionic and molecular transport in CNTs will be presented here.

Simulations and experimental studies have reported an unusually high ionic conductance in carbon nanotube (CNT) nanochannels. The origin of this phenomenon is, however, poorly-understood: literature reports often disagree in the magnitude of the different transport mode contributions to the measured ionic current and even in what ions are actually carrying the current; moreover, results obtained with single pore measurements differ frequently from those with membranes containing billions of open CNT channels, i.e. the average CNT behavior. Toward shedding light on these phenomena, we fabricated a novel platform having vertically-aligned sub-5nm carbon nanotubes as nanofluidic channels, the number of which can be controlled from one to billions. By employing this platform with only one or a few open CNTs, we observed giant ionic currents in CNT channels and a power-law increase of conductance with KCl concentration (G ∼ cn, n=0.1-0.4), a dependence that seems to be unique of CNT pores. To understand and quantify electro-osmotic flow in CNT pores (which has been proposed as the transport mode responsible for the giant ionic currents in CNTs), we investigated translocation of neutral molecules in a single CNT nanochannel with the resistive pulse technique. Furthermore, we used first-principle simulations to show that cation-CNT interactions may explain the origin of this electro-osmotic flow. Implications of our findings on the physics of electric-field-driven ionic and molecular transport in CNTs will be presented here.

In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO2) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO2 nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g(-1), areal capacitance: 1.11 F cm(-2)) which leads to an exceptionally high energy density of 39.28 Wh kg(-1) and power density of 128.01 kW kg(-1). The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications.

Rapid charging and discharging supercapacitors are promising alternative energy storage systems for applications such as portable electronics and electric vehicles. Integration of pseudocapacitive metal oxides with single-structured materials has received a lot of attention recently due to their superior electrochemical performance. In order to realize high energy-density supercapacitors, a simple and scalable method is developed to fabricate a graphene/MWNT/MnO2 nanowire (GMM) hybrid nanostructured foam, via a two-step process. The 3D few-layer graphene/MWNT (GM) architecture is grown on foamed metal foils (nickel foam) via ambient pressure chemical vapor deposition. Hydrothermally synthesized α-MnO2 nanowires are conformally coated onto the GM foam by a simple bath deposition. The as-prepared hierarchical GMM foam yields a monographical graphene foam conformally covered with an intertwined, densely packed CNT/MnO2 nanowire nanocomposite network. Symmetrical electrochemical capacitors (ECs) based on GMM foam electrodes show an extended operational voltage window of 1.6 V in aqueous electrolyte. A superior energy density of 391.7 Wh kg(-1) is obtained for the supercapacitor based on the GMM foam, which is much higher than ECs based on GM foam only (39.72 Wh kg(-1) ). A high specific capacitance (1108.79 F g(-1) ) and power density (799.84 kW kg(-1) ) are also achieved. Moreover, the great capacitance retention (97.94%) after 13 000 charge-discharge cycles and high current handability demonstrate the high stability of the electrodes of the supercapacitor. These excellent performances enable the innovative 3D hierarchical GMM foam to serve as EC electrodes, resulting in energy-storage devices with high stability and power density in neutral aqueous electrolyte.

Ultracapacitors are promising candidates for alternative energy storage applications since they can store and deliver energy at relatively high rates. Here, we present hybrid nanocarbon ultracapacitor electrodes with a low equivalent series resistance (ESR) of 7 ohms. 1-pyrenebutyric acid treated large-area single layer graphene (SLG) sheets covered with shortened multi-walled carbon nanotubes (MWNTs) have been utilized as highly conductive and percolated networks of hybrid carbon nanomaterial composites or thin films as ultracapacitor electrodes. Uniform centimeter scale single layer graphene sheets were produced via low pressure chemical vapor deposition using copper foil substrates and then subsequently modified by 1-pyrenebutyric acid functionalization. Chemically shortened MWNTs ranging in length of 200 similar to 500 nm, were deposited by drop casting on 1-pyrenebutyric acid functionalized SLG films. SLG/MWNT nancomposite hybrid films of different thicknesses were obtained by controlling the density of MWNT suspension. Surface morphology and nanostructure of the hybrid nanocomposites indicated relatively dense and homogeneous weblike networks. Specific capacitance values of the hybrid electrodes were substantially increased by 200% compared to those ultracapacitors fabricated using buckypaper electrodes. Average values of specific capacitance and energy density obtained were 140.64 F/g and 21.54 Wh/kg respectively. SLG/MWNT nanocomposite electrodes are very promising for future ultracapacitor devices with their low ESR value that is 95% lower than that of buckypaper based ultracapacitors.

This work describes the fabrication of highly sensitive graphene-based field effect transistor (FET) biosensors in a cost-effective way and its application in label-free DNA detection. CVD graphene was used to achieve mass production of FET device through photolithography method. Non-covalent functionalization of graphene with 1-Pyrenebutanoic acid succinimidyl ester ensures the high conductivity and sensitivity of the device. The present device could reach the low detection limit as low as 3*10-9 M.

The direct methanol fuel cell (DMFC) is a promising power source for electronic applications due to its high efficiency and compactness. To improve the efficiency, many support materials have been developed. We investigated uniform graphene nanoflake films as a support for catalytic Pt nanoparticles in direct carbon monooxide and formic acid electro-oxidation. Pt nanoparticles were deposited on the surface of graphene films with chemical reduction method. Chemical functionalization of graphene with ethylenediamine enables Pt nanoparticles mobilize on graphene uniformly. By simply changing the loading amount of Pt precursor, various particle sizes were achieved. The particle size of Pt plays prominent role in fuel cell test. The electrochemically active surface area of different sample are 6.3 (5 wt% Pt/G), 4.1 (20 wt% Pt/G), and 3.0 (50 wt% Pt/G) cm2mg-1 corresponding to the particle size 3±1nm, 10±2nm, 20±2nm respectively. The results obtained are ascribed to a uniform network made of 2-4 nm Pt monolayer nanopaticles on the surface of graphene flakes. Graphene will play significant role in developing next-generation advanced Pt based fuel cells and their relevant electrodes in the field of energy.