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A woven carbon fiber (WCF)-based triboelectric nanogenerator (TENG)-cum-structural supercapacitor is an excellent multifunctional device for clean energy harvesting and storage. This type of device has high load-bearing capacity and functions smoothly under severe outdoor conditions. Herein, WCF-based multifunctional TENG is reported that generated 8.9 W m−2 power with 84% energy conversion efficiency. The energy generated by the TENG was simultaneously stored in a connected supercapacitor that provide 1.93 Wh kg−1 of energy density and delivers 39.23 W kg−1 of power density. The specific surface area of the WCF was enhanced several hundred-fold by coating with an N-doped Zn–Cu selenide nanoporous material, thereby enabling higher energy generation and elevated storage capacity of the device. The TENG use a polyester-based solid polymer electrolyte as the negative electrode and polydimethylsiloxane-coated WCF as the positive electrode. The device has a very high coulombic efficiency with high mechanical strength and ability to resist massive impact. An application of the multifunctional device was demonstrated. These types of multifunctional devices have great potential in the self-charging automobile, aerospace, sensor, and electronics sectors.

Reduced graphene oxide (rGO) composites for energy-related applications have attracted increasing attention. However, previous studies on rGOs still showed limitations because of unresolved several...

A carbon electrode was designed to guarantee flexibility of symmetric electric double layer capacitors (EDLCs) based on its architecture. Three different dimensional carbon materials were combined ...

Graphene-based materials are an attractive lithium storage material for next-generation lithium-based batteries due to its high capacity, surface area and conductivity. However, one of the major problems for its broad application in batteries is a large irreversible capacity, and the poor cycle stability and low rate capability remain. Here, we report a MoS2-stabilized hierarchical three-dimensional graphene-based nanostructure, in which the MoS2 layer acts as a stabilizer as well as an active material. We show that the presence of MoS2 thin layer adjacent to the graphene surface can improve lithium storage capability by improving lithium ion diffusion property with fast Li-ion transport kinetic. On the basis of experimental and theoretical approaches, we ascribe the improved reversible lithium storage to the unusual reversible Li-MoS2 redox reaction and charge distribution on the graphene and MoS2 interlayers. These findings will provide a potential new direction in the design of electrode materials for advanced lithium storage technologies.

We introduce the use of xurography as a facile plotter-assisted integration technique for an all-solid-state flexible micro-supercapacitors (mSCs), which is cost-effective and time-saving, by which 162 mSCs can be simultaneously produced on an A4 sized PET film. 3D-graphene networks (3DGNs) grown on a SiO2 template exhibited large surface area and outstanding electrical conductivity as active materials for mSCs due to the interconnected 3D structure. By simply mixing SWNTs and Ag NWs with 3DGNs, an excellent specific areal capacitance of 19 mF cm−2 was obtained from an as-prepared 3DGN/SWNT/AgNW mSC on a flexible substrate and 84% of the initial capacitance was maintained after 10,000 cycles. The device exhibited stable electrochemical performances under various deformation conditions. The subsequent transfer onto a textile further allowed the fabrication of a wearable particle detector, which confirmed a practical application of a mSC with good performance integrated via a plotter-assisted technique.

We present a facile yet efficient single-step pyrolysis method to prepare bulk-scale high-performance N-doped 3D-graphitic foams with various length-scale pores. The iron precursors act as catalysts for the conversion of organic substances to a graphitic structure while simultaneously providing a rigid template that prevents the aggregation of organic components, and soluble polymers act as a carbon source for the formation of N-doped multilayer graphene under high-temperature and inert conditions. The 3D-graphitic foams possess highly interconnected networks composed of micro-, meso-, and macropores with a specific surface area of up to 1509 m2 g–1 and a high conductivity of 10 S m–1. The resulting 3D-graphitic foams exhibited specific capacitance values of 330 and 242 F g–1 with outstanding cycling stability (a 23% loss after 100 000 cycles for a symmetric cell) in a three-electrode system and in a symmetric cell, respectively, when used as active materials in a supercapacitor. This study suggests the g...

We report a three-dimensional graphene network decorated with nickel nanoparticles as a current collector to achieve outstanding performance in Ni(OH)2-based supercapacitors with excellent energy density. A cost-efficient and single-step fabrication method creates nickel-particle decorated three-dimensional graphene networks (Ni–GNs) with an excellent electrical conductivity of 107 S m−1 and a surface area of 16.4 m2 g−1 that are superior to those of carbon alternatives and commercial 3D-Ni foam, respectively. The supercapacitor in which Ni(OH)2 active materials are deposited on Ni–GNs exhibited an outstanding capacitance value of 3179 F g−1 at 10 A g−1 in a three-electrode system and 90% of capacitance retention after 10 000 cycles. Furthermore, it showed an outstanding energy density of 197.5 W h kg−1 at a power density of 815.5 W kg−1 when tested in a two-electrode system. To the best of our knowledge, our device realized the world record value of energy density with a high rate capability and good cycle stability among Ni(OH)2-based supercapacitors. The excellent electrical properties of easily synthesized Ni–GNs as the ideal current collector clearly suggest a straightforward way to achieve great performance supercapacitors with both high energy density and power density.

Realization of a highly flexible, lightweight, and high performance flexible supercapacitor was achieved using three-dimensional graphene on flexible graphite-paper. A simple and fast self-assembly approach was utilized for the uniform deposition of chemical vapor deposition (CVD)-grown high quality 3D-graphene powders on a flexible graphite-paper substrate. The fabricated paper-based symmetric supercapacitor exhibited a maximum capacitance of 260 F g −1 (15.6 mF cm −2 ) in a three electrode system, 80 F g −1 (11.1 mF cm −2 ) in a full cell, high capacitance retention and a high energy density of 8.8 Wh kg −1 (1.24 μWh cm −2 ) at a power density of 178.5 W kg −1 (24.5 μW cm −2 ). The flexible supercapacitor maintained its supercapacitor performance well, even under bent, rolled, or twisted conditions, signifying the excellent flexibility of the fabricated device. Our straightforward approach to the fabrication of highly flexible and lightweight supercapacitors offers new design opportunities for flexible/wearable electronics and miniaturized device applications that require energy storage units that meet the demands of the multifarious applications.

Vertically aligned iron oxide nanowire arrays were successfully synthesized via a cost-efficient maskless top-down approach. High density nanowires are formed by simple oxygen reactive ion etching of an iron-containing polymer film without any artificial mask. Highly crystalline hematite nanowires with a diameter of 38–45 nm and a high aspect ratio of 131 are uniformly produced over large areas after calcination. The high density graphene/magnetite nanostructure created by pyrolyzing iron oxide/organic nanowires with three-dimensional morphology provided highly enhanced Raman scattering with an enhancement factor of up to 7.0 × 104 due to trapping of the absorbed light in the three-dimensional graphene forest. Our maskless top-down approach to fabricate iron oxide nanowires offers unique advantages of a solution-based process to easily overcome the limit in the morphology and substrate-dependent properties of nanowire synthesis. This technique may have excellent practical potential as a simple, rapid, and reproducible process for the fabrication of high density and high aspect ratio iron oxide nanowires that are useful in various applications.

This is the first report on the fabrication of defect-free submicron structures with more than 100 μm thickness and an aspect ratio over 100. Highly transparent poly(glycidyl methacrylate-co-acryloisobutyl POSS) (PGP) was synthesized via radical polymerization. The mechanical properties of the PGP submicron structure displayed a Young's modulus of 6.09 GPa and a hardness of 0.16 GPa, 4.2 and 8 times, respectively, than those of SU8 nanopatterns. These enhancements enable the utilization of ultrathick 2D-/3D-submicron structures as an ideal platform for microelectromechanical systems, big data storage systems, energy devices, etc.

We demonstrate a unique synthetic route for oxygen-deficient mesoporous TiOx by a redox-transmetalation process by using Zn metal as the reducing agent. The as-obtained materials have significantly enhanced electronic conductivity; 20 times higher than that of as-synthesized TiO2 material. Moreover, electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) measurements are performed to validate the low charge carrier resistance of the oxygen-deficient TiOx . The resulting oxygen-deficient TiOx battery anode exhibits a high reversible capacity (∼180 mA h g-1 at a discharge/charge rate of 1 C/1 C after 400 cycles) and an excellent rate capability (∼90 mA h g-1 even at a rate of 10 C). Also, the full cell, which is coupled with a LiCoO2 cathode material, exhibits an outstanding rate capability (>75 mA h g-1 at a rate of 3.0 C) and maintains a reversible capacity of over 100 mA h g-1 at a discharge/charge of 1 C/1 C for 300 cycles.

This study introduces an in situ fabrication of nanoporous hematite with a Ti-doped SiOx passivation layer for a high-performance water-splitting system. The nanoporous hematite with a Ti-doped SiOx layer (Ti-(SiOx /np-Fe2 O3 )) has a photocurrent density of 2.44 mA cm(-2) at 1.23 VRHE and 3.70 mA cm(-2) at 1.50 VRHE . When a cobalt phosphate co-catalyst was applied to Ti-(SiOx /np-Fe2 O3 ), the photocurrent density reached 3.19 mA cm(-2) at 1.23 VRHE with stability, which shows great potential of the use of the Ti-doped SiOx layer with a synergistic effect of decreased charge recombination, the increased number of active sites, and the reduced hole-diffusion pathway from the hematite to the electrolyte.

Supercapacitors are known to suffer from relatively low energy density and stability, which hampers their substitution for existing batteries. Here, we report an outstanding positive electrode platform for supercapacitor having both high energy density and high power density as well as good stability, by fabricating a low resistance Ohmic contact between Ni(OH)2 active materials and a 3-D current collector, nanoporous gold (NPG). The Ni(OH)2/NPG electrode was optimized by finely adjusting the portion of two different parts of the deposited Ni(OH)2, one part in direct contact with the NPG and the other part on top of the NPG. The optimized Ni(OH)2/NPG electrode exhibited 2223 F/cm3 of volumetric capacitance (considering both the active material and the current collector) at a current density of 5 A/g, values which are beyond the theoretical capacitance value, and the device retained 90% capacitance of the initial value at 500 A/g and after 30,000 cycles, respectively. This electrode showed an excellent energy density of 98 Wh/kg and power density of 50 kW/kg in a Ni(OH)2/NPG//MnO2/NPG two electrode supercapacitor system. The excellent performance of the Ni(OH)2/NPG electrode is attributed not only to the increased surface area of the Ni(OH)2 active materials, but also to the favorable path for charge transport created between the Ni(OH)2 and the gold electrode due to the presence of Ohmic contact, which eventually leads to the good kinetic properties and good stability.

Capacitive deionization (CDI) has attracted immense attention in recent years due to its simple energy efficient and eco-friendly desalination process. In capacitive deionization research, limited scale of fabrication for active materials and improving desalination efficiency have been the major challenges. Herein, micro-meso-macroporous three-dimensional graphene (MMM-3DG) with a high surface area (1492.8 m2 g−1) was fabricated in gram-scale production (>1.0 g per one time) as an effective active material for CDI. MMM-3DG exhibited a high electrosorption capacity (9.37 mg g−1) and a fast electrosorption rate (2.79 mg g−1 min−1). Furthermore, MMM-3DG delivered an outstanding rate constant value of 0.071 by a pseudo-second-order kinetic model, and thus low energy consumption value per desalinating ion (33.17 kJ mol−1) during the adsorption process.

By creating a p–n heterojunction of molybdenum sulfide (MoSx)/Ti-doped Fe2O3 (Ti-Fe2O3), we successfully addressed electron–hole transfer problems of hematite and thus achieved the enhanced photoelectrochemical (PEC) performance. MoSx/Ti-Fe2O3 with a thin MoSx layer on the surface of Ti-Fe2O3 fabricated a p–n junction that provided facile charge transfer pathways due to an internal electric field between Ti-Fe2O3 and MoSx, and achieved suppressed charge recombination. The optimized MoSx/Ti-Fe2O3 sample showed a 240% increased photocurrent density (3.03 mA cm−2) over pristine Fe2O3 at RHE 1.50 V. All our data including IPCE, PL, and EIS clearly confirmed the improved PEC performance of MoSx/Ti-Fe2O3 achieved by the formation of a p–n junction with a facile electron–hole transport pathway.

We propose a straightforward way to realize the theoretical capacitance and high rate capability of nickel hydroxide supercapacitors, by utilizing a mesoporous hollow dendritic three-dimensional-nickel (3D-nkckel) current collector. A facile electrodeposition method employing a hydrogen bubble template is chosen for rapid fabrication of the dendritic 3D-nickel structure. After nickel hydroxide is deposited on the hollow 3D-nickel current collector, it exhibits a highest capacitance of 3,637 F/g at a current density of 1 A/g, and retains 97% of capacitance at a high current density of 100 A/g with great cycle stability of over 80% after 10,000 cycles. The enhanced performance can be attributed to the large surface area and high conductivity of the moss-like dendritic 3D-nickel current collector, which allows direct contact between the active materials and the current collector and reduced diffusion resistance between the surface of the active materials and the electrolyte. These results not only confirm a facile fabrication method for high-performance 3D-metal nanostructures, but also offer a promising solution for state-of-the-art energy storage systems.

By coupling α-Fe2O3 with a 3D graphene inverse opal (3D-GIO) conducting electrode, the short diffusion length of carriers and low absorption coefficient in α-Fe2O3 for photoelectrochemical applications were successfully addressed. GIO was directly grown on FTO substrate under low temperature conditions, removing the need for a graphene transfer process. α-Fe2O3 nanoparticles (NPs) were hydrothermally deposited on the surface of GIO, creating α-Fe2O3/GIO. The photocurrent density of α-Fe2O3/GIO in water splitting reactions reached 1.62 mA/cm(2) at 1.5 V vs RHE, which is 1.4 times greater than that of optimized α-Fe2O3. The EIS and IPCE data confirm reduced electron-hole recombination and fast electron transfer processes due to the short distance between active materials and the conducting electrode in the α-Fe2O3/GIO system. Our result may pave the way for designing devices in advanced energy conversion applications as well as a high efficiency hematite-based PEC system.

We introduce a straightforward strategy to simultaneously improve the capacitance, rate capability, and cycle life of a supercapacitor by simply electrodepositing Ni-nanoparticles (Ni-NPs) on an as-prepared electrode. 3D-structured current collectors such as metal foams, metal meshes, and carbon meshes have been widely used in supercapacitors, secondary batteries, glucose sensors, etc. In particular, the 3D-metal foam readily improves device properties due to its unique 3D-nature and high surface area. However, there are practical constraints when applying 3D-current collectors to the industrial world, including high cost. Here, by simply electrodepositing Ni-NPs in a cost-efficient manner, a similar effect to that derived with the use of 3D-metal foam was realized. After deposition, Ni-NPs are preferentially located near the contact area between the active materials and a plate-type current collector, which allows for tight binding between the active materials and the current collector as well as facile charge transfer and high capacitance. The Ni-deposited Ni(OH)2 electrode pasted on a plate metal substrate showed 350% increased capacitance (1264 F g−1) and stability of 75% and 72% after 10 000 cycles and at a high current density of 20 A g−1, respectively. Given the simplicity and cost-efficiency of this method, it can be readily applied to other energy storage devices with practical applications in the industrial world.

We report CVD-grown p-doped three-dimensional graphene nano-networks (3D-GNs) that provide superior performance to Pt as a counter electrode material in dye sensitized solar cells (DSSCs). The 3D-GN based DSSC exhibits a maximum photoconversion efficiency of 8.46%, which is 6.01% greater than that exhibited by Pt based DSSCs.

In this report, we show that by creating a nanoporous haematite (α-Fe2O3) structure using boric acid (H3BO3) treatment, the chronic issue of the short diffusion length of carriers in α-Fe2O3 for photoelectrochemical (PEC) applications can be successfully addressed. The slow release of Fe3+ ions because of the presence of H3BO3 leads to the creation of smaller dimension FeOOH nanorods, creating nanoporous α-Fe2O3 nanorods, composed of ∼15 nm α-Fe2O3 domains. The nanoporous α-Fe2O3 suppresses recombination by providing the facile extraction of holes from the surface of favorably sized α-Fe2O3 domains. The optimized nanoporous sample showed a photocurrent density of 1.41 mA cm−2 at a reversible hydrogen electrode of 1.23 V, which is 1.7 times higher than that of pristine hematite. The electrochemical impedance spectroscopy and incident photon-to-current efficiency data, and Mott–Schottky plots confirmed the superior performance of the nanoporous samples. Our impressive results may pave the way for designing devices for advanced energy conversion applications as well as fabricating a high efficiency hematite-based PEC system.

Chemically reduced graphene oxide (rGO) decorated with aliphatic dendrimers having gold nanoparticles either in their endo- or exo-positions was firstly formulated through fully noncovalent functio...

A hierarchically patterned metal/semiconductor (gold nanoparticles/ZnO nanowires) nanostructure with maximized photon trapping effects is fabricated via interference lithography (IL) for plasmon enhanced photo-electrochemical water splitting in the visible region of light. Compared with unpatterned (plain) gold nanoparticles-coated ZnO NWs (Au NPs/ZnO NWs), the hierarchically patterned Au NPs/ZnO NWs hybrid structures demonstrate higher and wider absorption bands of light leading to increased surface enhanced Raman scattering due to the light trapping effects achieved by the combination of two different nanostructure dimensions; furthermore, pronounced plasmonic enhancement of water splitting is verified in the hierarchically patterned Au NPs/ZnO NWs structures in the visible region. The excellent performance of the hierarchically patterned Au NPs/ZnO NWs indicates that the combination of pre-determined two different dimensions has great potential for application in solar energy conversion, light emitting diodes, as well as SERS substrates and photoelectrodes for water splitting.

Dendrimer-stabilized gold nanoparticles (Au-Den) were prepared by a facile solution based method for a highly reliable and robust surface enhanced Raman scattering (SERS) substrate. Au-Den was selectively attached on the surface of reduced graphene oxide (rGO) by noncovalent interactions between the Au capping dendrimer and the graphene surface. Au-Den/rGO exhibits the outstandingly stable and highly magnified Raman signal with an enhancement factor (EF) of 3.9 × 10(7) that enables detection of R6G dyes with concentration as low as 10 nM, retaining 95% of the Raman signal intensity after 1 year. The remarkable stability and enhancement originated not only from a simple combination of the electromagnetic and chemical mechanism of SERS but also from intensified packing density of stable Au-Den on the graphene substrate due to the firm binding between the dendrimer capped metal nanoparticles and the graphene substrate. This method is not limited to the gold nanoparticles and G4 dendrimer used herein, but also can be applied to other dendrimers and metal nanoparticles, which makes the material platform suggested here superior to other SERS substrates.

Phase mask interference lithography was employed to fabricate three-dimensional (3D) hydrogel structures with high surface area on neural prosthetic devices. A random terpolymer of poly(hydroxyethyl methacrylate-ran-methyl methacrylate-ran-methacrylic acid) was synthesized and used as a negative-tone photoresist to generate bicontinuous 3D hydrogel structures at the submicrometer scale. We demonstrated that the fully open 3D hydrogel/air networks can be used as a pH-responsive polymeric drug-release system for the delivery of neurotrophins to enhance the performance of neural prosthetic devices. Additionally an open hydrogel structure will provide direct access of neuronal growth to the device for improved electrical coupling.

hasemergedasanattractivealternativetechniquethatallowstherationaldesignofcomplexanddefect-free1D,2D,and3Dpatternsoverlargeareas.Besidesbeingfastandefficient,ILalsoaffordscontrolovergeometricalparameters,suchassymme-try and volume fractions, of the structures formed. ILperformed using an elastomeric poly(dimethylsiloxane)(PDMS)phasemask

Interference lithography (IL) holds the promise of fabricating large-area, defect-free 3D structures on the submicrometer scale both rapidly and cheaply. A stationary spatial variation of intensity is created by the interference of two or more beams of light. The pattern that emerges out of the intensity distribution is transferred to a light sensitive medium, such as a photoresist, and after development yields a 3D bicontinuous photoresist/air structure. Importantly, by a proper choice of beam parameters one can control the geometrical elements and volume fraction of the structures. This article provides an overview of the fabrication of 3D structures via IL (e.g., the formation of interference patterns, their dependence on beam parameters and several requirements for the photoresist) and highlights some of our recent efforts in the applications of these 3D structures in photonic crystals, phononic crystals and as microframes, and for the synthesis of highly non spherical polymer particles. Our discussion concludes with perspectives on the future directions in which this technique could be pursued.

Materials science, especially metallurgy, has long exploited the relationship between microstructural scale, arising from various processing routes, and resultant properties, with increasing emphasis on the benefits of ultrafine-scale structures. Critical elements for the design of lightweight materials for mechanical applications include a means for stiffening and strengthening as well as providing energy absorption and controlled crack propagation. [1–4] Combinations of hard and soft components, control over component size, shape, and arrangement, and attention to interfacial strength are widely used to design composite materials with superior properties. Manmade ordered composites are typically assembled via machine or hand lay up and generally rely on macroscopic components. On the other hand, load-bearing structures in nature are much more complex, often using a combination of hard (e.g., calcite) and soft (e.g., proteins) components and importantly, feature elegant self-organized hierarchical designs extending from the nanometer to the millimeter scale. [5] Moreover, nature has evolved certain structures into nearly optimized mechanical designs. [6] Most current man-made sub-micrometer-scale composites provide little control over the detailed microstructure of the respective components. [7] For example, recent efforts with polymer–carbon-nanotube composites currently lack the processing ability to pattern the components at various length scales to create optimally designed materials. Patterning using self-assembly is one means to mimic nature but at present most ordered structures occur more by chance than by purposeful design and the pattern is achieved normally only at one length scale. Taking advantage of lengthscale-dependent mechanical properties is another strategy used by nature to tailor mechanical behavior. [5] Polymeric materials in particular are also sensitive to the influence of sample dimensions on properties; for example, below a critical film thickness brittle polymers can exhibit increased strain-tobreak and improved toughness. [8,9] Lightweight microframe structural materials possessing load-bearing capabilities approaching theoretical limits have recently been constructed from millimeter-sized metallic assemblies. [10] Their open architecture provides a density well below 10% of that of the corresponding bulk materials. [11] Several structures have been fabricated, tested, and theoretically analyzed. However, for feature sizes at the millimeter scale, the material’s mechanical properties are not size dependent; indeed, theoretical models that rely only on inputting a constitutive equation based on bulk material behavior along with the particular truss geometry do a very good job of capturing the experimentally observed behavior. Designs that provide conditions such that beams are under compression or tension while avoiding bending are desired. In particular, pyramidal and octahedral frame structures provide maximum stiffness and strength at a given density. [12] In addition to outstanding specific mechanical properties, the open structure and high surface area (ca. m 2 g –1 ) of microframes add addi

In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g(-1) at 1 A g(-1), which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g(-1) and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g(-1) and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data.

This work has been performed to determine the critical size of the GeO2 nanoparticle for lithium battery anode applications and identify its quantum confinement and its related effects on the electrochemical performance. GeO2 nanoparticles with different sizes of ∼ 2, ∼ 6, ∼ 10, and ∼ 35 nm were prepared by adjusting the reaction rate, controlling the reaction temperature and reactant concentration, and using different solvents. Among the different sizes of the GeO2 nanoparticles, the ∼ 6 nm sized GeO2 showed the best electrochemical performance. Unexpectedly smaller particles of the ∼ 2 nm sized GeO2 showed the inferior electrochemical performances compared to those of the ∼ 6 nm sized one. This was due to the low electrical conductivity of the ∼ 2 nm sized GeO2 caused by its quantum confinement effect, which is also related to the increase in the charge transfer resistance. Those characteristics of the smaller nanoparticles led to poor electrochemical performances, and their relationships were discussed.

By simply heating commercial copper foil under an oxygen atmosphere and subsequently annealing CuO under a hydrogen atmosphere, the 3D Cu structures in the form of double hierarchical bumps are generated. The contact angle of a lotus leaf-inspired graphene grown on the reconstructed 3D Cu structures is 154.2°.

A mass-producible mesoporous graphene nanoball (MGB) was fabricated via a precursor-assisted chemical vapor deposition (CVD) technique for supercapacitor application. Polystyrene balls and reduced iron created under high temperature and a hydrogen gas environment provide a solid carbon source and a catalyst for graphene growth during the precursor-assisted CVD process, respectively. Carboxylic acid and sulfonic acid functionalization of the polystyrene ball facilitates homogeneous dispersion of the hydrophobic polymer template in the metal precursor solution, thus, resulting in a MGB with a uniform number of graphene layers. The MGB is shown to have a specific surface area of 508 m(2)/g and is mesoporous with a mean mesopore diameter of 4.27 nm. Mesopores are generated by the removal of agglomerated iron domains, permeating down through the soft polystyrene spheres and providing the surface for subsequent graphene growth during the heating process in a hydrogen environment. This technique requires only drop-casting of the precursor/polystyrene solution, allowing for mass-production of multilayer MGBs. The supercapacitor fabricated by the use of the MGB as an electrode demonstrates a specific capacitance of 206 F/g and more than 96% retention of capacitance after 10,000 cycles. The outstanding characteristics of the MGB as an electrode for supercapacitors verify the strong potential for use in energy-related areas.

Dual-scale diamond-shaped gold nanostructures (d-DGNs) with larger scale diamond-shaped gold nanoposts (DGNs) coupled to smaller scale gold nanoparticles have been fabricated via interference lithography as a highly reliable and efficient substrate for surface enhanced Raman scattering (SERS). The inter- and intra-particle plasmonic fields of d-DGNs are varied by changing the periodicity of the DGNs and the density of gold nanoparticles. Because of the two different length scales in the nanostructures, d-DGNs show multipole plasmonic peaks as well as dipolar plasmonic peaks, leading to a SERS enhancement factor of greater than 10(9). Simulations are carried out by finite-difference time-domain (FDTD) methods to evaluate the dependence of the inter- and intra-particle plasmonic field and the results are in good agreement with the experimentally obtained data. Our studies reveal that the combination of two different length scales is a straightforward approach for achieving reproducible and great SERS enhancement by light trapping in the diamond-shaped larger scale structures as well as efficient collective plasmon oscillation in the small size particles.

Phase mask interference lithography was employed to fabricate three-dimensional (3D) hydrogel structures with high surface area on neural prosthetic devices. A random terpolymer of poly(hydroxyethyl methacrylate- ran-methyl methacrylate- ran-methacrylic acid) was synthesized and used as a negative-tone photoresist to generate bicontinuous 3D hydrogel structures at the submicrometer scale. We demonstrated that the fully open 3D hydrogel/air networks can be used as a pH-responsive polymeric drug-release system for the delivery of neurotrophins to enhance the performance of neural prosthetic devices. Additionally an open hydrogel structure will provide direct access of neuronal growth to the device for improved electrical coupling.

We present a new route for the fabrication of highly nonspherical complex multivalent submicron particles. This technique exploits the ability of holographic interference lithography to control geometrical elements such as symmetry and volume fraction in 3D lattices on the submicron scale. Colloidal particles with prescribed complex concave shapes are obtained by cleaving low volume fraction connected structures fabricated by interference lithography. Controlling which Wyckoff sites in the space group of the parent structure are connected assures specific “valencies” of the particles. Two types of particles, 2D “4-valent” and 3D “6-valent” particles are fabricated via this technique. In addition to being able to control multivalent particle shape, this technique has the potential to provide tight control over size, yield, and dispersity.

Increasing interest in electric transportation and bulk energy storage systems has fueled a growth in the demand for battery technologies that can offer both a high capacity and high energy density. Potential candidates include lithium sulfur batteries based on a lithium sulfide (Li2S) cathode material, which overcome many of the problems associated with other lithium sulfur battery designs. The downside of this is that Li2S has a sluggish activation process, and so, in a bid to overcome this shortcoming, various studies have aimed at better understanding the activation mechanism of this material so that it can be more effectively utilized. An overview of these efforts, as well as of the various full-cell systems that have been subsequently developed based on Li2S cathodes in combination with different anode materials such as silicon nanowires, silicon thin films, and tin composites is provided.

We show how to employ an interference lithographic template (ILT) as a facile mold for fabricating three-dimensional bicontinuous PDMS (poly(dimethylsiloxane)) elastomeric structures and demonstrate the use of such a structure as a mechanically tunable PDMS/air phononic crystal. A positive photoresist was used to make the ILT, and after infiltration with PDMS, the resist was removed in a water-based basic solution which avoided PDMS swelling or pattern collapse occurring during the ILT removal process. Since the period of the structure is approximately 1 microm, the density of states of gigahertz phonons are altered by the phononic PDMS/air crystal. Brillouin light scattering (BLS) was employed to measure phononic modes of the structure as a function of mechanical strain. The results demonstrate that the phononic band diagram of such structures can be tuned mechanically.

We propose three dimensional-graphene nanonetworks (3D-GN) with pores in the range of 10 ∼ 20 nm as a potential candidate for thermoelectric materials. The 3D-GN has a low thermal conductivity of 0.90 W/mK @773 K and a maximum electrical conductivity of 6660 S/m @ 773 K. Our results suggest a straightforward way to individually control two interdependent parameters, σ and κ, in the nanoporous graphene structures to ultimately improve the figure of merit value.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

We demonstrate a graphene-coated polymer film as a transparent piezoresistive strain sensor. Strain sensitivity was tuned by controlling the thickness and density of the graphene layer as well as the adhesion force between graphene and the substrate. Chemically reducing the graphene oxide, thereby maximizing its adhesion to the substrate, while minimizing the coating density and thickness resulted in excellent transparency and high gauge factors. The fabrication method presented allows design optimization of transparent, high-performance, and sensitivity-tunable piezoresistive sensors, which can make inroads into such applications as wide-area strain sensors, self-sensing flexible electronics, and intelligent structural health monitoring.

We present a simple route towards a superhydrophobic graphene surface, which opens up possibilities for transparent flexible graphene-based electrodes with a non-wetting property. By tailoring the surface energy and surface roughness, superhydrophobic properties of graphene with a contact angle greater than 150° at an optical transparency of 72.7% were obtained.

We report a robust and direct route to fabricate a three-dimensional nano-foam of few-layer graphene (3D-NFG) with large area coverage via a chemical vapor deposition (CVD) technique. Pyrolysis of polymer/nickel precursor film under a hydrogen environment, simply prepared by spin-coating, leads to the creation of nano-foam in the film and the reduction process of nickel ions. Carbonized-C and the nickel nano-frame formed from the pyrolysis are used as a solid carbon source and as a catalyst for the growth of graphene under CVD conditions, respectively. We investigate the use of 3D-NFG, with the advantage of large surface area and high conductivity, as an alternative to the Pt counter electrode material in dye sensitized solar cells. The excellent properties of 3D-NFG, fabricated in this simple and direct manner, suggest a great potential for interconnected graphene networks in electronic devices and photocatalytic sensors as well as in energy-related materials.

Combining the physical principle of actuators with the basic concept of photonic crystals, colour-tunable three-dimensional (3D) photonic actuators were successfully fabricated. By controlling the d-spacings and the refractive index contrasts of the self-assembled 3D colloidal photonic crystals, colours of the photonic actuators were tuned. Various shapes of these 3D actuating objects were constructed by transforming the programmed 2D structures via bending, twisting and folding mechanisms. These 2D structures were first programmed by breaking the symmetry. The selective swellings were then applied as driving forces to control the shapes and colours of the photonic actuators. Scroll photonic actuators had been first demonstrated by bending the traditional 2D cantilever structure (K.-U. Jeong, et al., J.Mater.Chem., 2009, 19, 1956). By breaking the symmetry of a cantilever structure perpendicular to its long axis, polypeptide-/DNA-like 3D helical photonic actuators were obtained from the programmed 2D structure via twisting processes. Both left- and right-handed scrolls and helices with various colours can be achieved by changing the polarity of solvents. Different types of 3D actuators, such as cube, pyramid and phlat ball, were also demonstrated via the folding mechanism. The reversible 3D photonic actuators transformed from the programmed 2D structures via the bending, twisting and folding mechanisms may be applied in the field of mechanical actuators, and optoelectronic and bio-mimetic devices.