We have investigated the various morphological changes of helical nanofilament (HNF; B4) phases in multiscale nanochannels made of porous anodic aluminum oxide (AAO) film. Single or multihelical structures could be manipulated depending on the AAO pore size and the higher-temperature phase of each molecule. Furthermore, the nanostructures of HNFs affected by the chemical affinity between the molecule and surface were drastically controlled in surface-modified nanochannels. These well-controlled hierarchical helical structures that have multidimensions can be a promising tool for the manipulation of chiral pores or the nonlinear optical applications.

Supercapacitive properties of ruthenium oxide (RuO2) nanoparticles electrodeposited onto the indium tin oxide (ITO) nanopillars were investigated. Compared to conventional planar current collectors, this coaxially nanostructured current collector–electrode system can provide increased contact for efficient charge transport, and the internanopillar spacing allows easy access of electrolyte ions. The morphological and electrochemical properties depended on the thickness of the RuO2 layers, i.e., the number of electrodeposition cycles. A maximum specific capacitance, Csp, of 1235 F/g at a scan rate of 50 mV/s was achieved for the 30-cycle deposited RuO2–ITO nanopillars. The other capacitive properties such as electrochemical reversibility and Csp retention at high scan rates also improved greatly.

Here we report the high performance and cyclability of an asymmetric full cell nanopore battery, comprised of V2O5 as the cathode and prelithiated SnO2 as the anode, with integrated nanotubular Pt current collectors underneath each nanotubular storage electrode, confined within an anodized aluminium oxide (AAO) nanopore. Enabled by atomic layer deposition (ALD), this coaxial nanotube full cell is fully confined within a high aspect ratio nanopore (150 nm in diameter, 50 μm in length), with an ultra-small volume of about 1 fL. By controlling the amount of lithium ion prelithiated into the SnO2 anode, we can tune the full cell output voltage in the range of 0.3 V to 3 V. When tested as a massively parallel device (∼2 billion cm−2), this asymmetric nanopore battery array displays exceptional rate performance and cyclability: when cycled between 1 V and 3 V, capacity retention at the 200C rate is ∼73% of that at 1C, and at 25C rate only 2% capacity loss occurs after more than 500 charge/discharge cycles. With the increased full cell output potential, the asymmetric V2O5–SnO2 nanopore battery shows significantly improved energy and power density over the previously reported symmetric cell, 4.6 times higher volumetric energy and 5.2 times higher power density – an even more promising indication that controlled nanostructure designs employing nanoconfined environments with large electrode surface areas present promising directions for future battery technology.

Conventional electrical energy storage (EES) electrodes, such as rechargeable batteries, are mostly based on composites of monolithic micrometer sized particles bound together with polymeric and conductive carbon additives and binders. The kinetic limitations of these monolithic chunks of material are inherently linked to their electrical properties, the kinetics of ion insertion through their interface and ion migration in and through the composite phase. Redox chemistry of nanostructured materials in EES systems offer vast gains in power and energy. Furthermore, due to their thin nature, ion and electron transport is dramatically increased, especially when thin heterogeneous conducting layers are employed synergistically. However, since the stability of the electrode material is dictated by the nature of the electrochemical reaction and the accompanying volumetric and interfacial changes from the perspective of overall system lifetime, research with nanostructured materials has shown often indefinite conclusions: in some cases, an increase in unwanted side-reactions due to the high surface area (bad). In other cases, results have shown significantly better handling of mechanical stress that results from lithiation/delithiation (good). Despite these mixed results, scientifically informed design of thin electrode materials, with carefully chosen architectures, is considered a promising route to address many limitations witnessed in EES systems by reducing and protecting electrodes from parasitic reactions, accommodating mechanical stress due to volumetric changes from electrochemical reactions, and optimizing charge carrier mobilities from both the “ionic” and “electronic” points of view. Furthermore, precise nanoscale control over the electrode structure can enable accurate measurement through advanced spectroscopy and microscopy techniques.This Account summarizes recent findings related to thin electrode materials synthesized by atomic layer deposition (ALD) and electrochemical deposition (ECD), including nanowires, nanotubes, and thin films. Throughout the Account, we will show how these techniques enabled us to synthesize electrodes of interest with precise control over the structure and composition of the material. We will illustrate and discuss how the electrochemical response of thin electrodes made by these techniques can facilitate new mechanisms for ion storage, mediate the interfacial electrochemical response of the electrode, and address issues related to electrode degradation over time. The effects of nanosizing materials and their electrochemical response will be mechanistically reviewed through two categories of ion storage: (1) pseudocapacitance and (2) ion insertion. Additionally, we will show how electrochemical processes that are more complicated because of accompanying volumetric changes and electrode degradation pathways can be mediated and controlled by application of thin functional materials on the electrochemically active interface; examples include conversion electrodes, reactive lithium metal anodes, and complex reactions in a Li/O2 cathode system. The goal of this Account is to illustrate how careful design of thin materials either as active electrodes or as mediating layers can facilitate desirable interfacial electrochemical activity and resolve or shed light on mechanistic limitations of electrochemical processes related to micrometer size particles currently used in energy storage electrodes.

Bismuth is a lithium-ion battery anode material that can operate at an equilibrium potential higher than graphite and provide a capacity twice as high as that of Li4Ti5O12, making it intrinsically free from lithium plating that may cause catastrophic battery failure. However, the potential of bismuth is hampered by its inferior cyclability (limited to tens of cycles). Here, we propose an “ion conductive solid-state matrix” approach to address this issue. By homogeneously confining bismuth nanoparticles in a solid-state γ-Li3PO4 matrix that is electrochemically formed in situ, the resulting composite anode exhibits a reversible capacity of 280 mA hours per gram (mA h/g) at a rate of 100 mA/g and a record cyclability among bismuth-based anodes up to 500 cycles with a capacity decay rate of merely 0.071% per cycle. We further show that full-cell batteries fabricated from this composite anode and commercial LiFePO4 cathode deliver a stable cell voltage of ∼2.5 V and remarkable energy efficiency up to 86.3%, on par with practical batteries (80–90%). This work paves a way for harnessing bismuth-based battery chemistry for the design of high capacity, safer lithium-ion batteries to meet demanding applications such as electric vehicles.Keywords: battery safety; bismuth electrode; conductive matrix; Electrical energy storage; energy efficiency;

Ordered mesoporous carbons (OMCs) are ideal host materials that can provide the desirable electrical conductivity and ion accessibility for high-capacity oxide electrode materials in lithium-ion batteries (LIBs). To this end, however, it is imperative to establish the correlations among material morphology, pore structure and electrochemical performance. Here, we fabricate an ordered mesoporous carbon nanowire (OMCNW)/Fe2O3 composite utilizing a novel soft–hard dual-template approach. The structure and electrochemical performance of OMCNW/Fe2O3 were systematically compared with single-templated OMC/Fe2O3 and carbon nanowire/Fe2O3 composites. This dual-template strategy presents synergetic effects combining the advantages of both soft and hard single-template methods. The resulting OMCNW/Fe2O3 composite enables a high pore volume, high structural stability, enhanced electrical conductivity and Li+ accessibility. These features collectively enable excellent electrochemical cyclability (1200 cycles) and a reversible Li+ storage capacity as high as 819 mA h g−1 at a current density of 0.5 A g−1. Our findings highlight the synergistic benefits of the dual-template approach to heterogeneous composites for high performance electrochemical energy storage materials.

Rechargeable Mg battery has been considered a major candidate as a beyond lithium ion battery technology, which is apparent through the tremendous works done in the field over the past decades. The challenges for realization of Mg battery are complicated, multidisciplinary, and the tremendous work done to overcome these challenges is very hard to organize in a regular review paper. Additionally, we claim that organization of the huge amount of information accumulated by the great scientific progress achieved by various groups in the field will shed the light on the unexplored research domains and give clear perspectives and guidelines for next breakthrough to take place. In this Perspective, we provide a convenient map of Mg battery research in a form of radar chart of Mg electrolytes, which evaluates the electrolyte under the important components of Mg batteries. The presented radar charts visualize the accumulated knowledge on Mg battery and allow for navigation of not only the current research state but also future perspective of Mg battery at a glance.

Quantifying the amount of antibody on magnetic particles is a fundamental, but often overlooked step in the development of magnetic separation-based immunoaffinity enrichment procedures. In this work, a targeted mass spectrometry (MS)-based method was developed to directly measure the amount of antibody covalently bound to magnetic particles. Isotope-dilution liquid chromatography-tandem MS (ID-LC-MS/MS) has been extensively employed as a gold-standard method for protein quantification. Here, we demonstrate the utility of this methodology for evaluating different antibody coupling processes to magnetic particles of different dimensions. Synthesized magnetic nanoparticles and pre-functionalized microparticles activated with glutaraldehyde or epoxy surface groups were used as solid supports for antibody conjugation. The key steps in this quantitative approach involved an antibody-magnetic particle coupling process, a wash step to remove unreacted antibody, followed by an enzymatic digestion step (in situ with the magnetic particles) to release tryptic antibody peptides. Our results demonstrate that nanoparticles more efficiently bind antibody when compared to microparticles, which was expected due to the larger surface area per unit mass of the nanoparticles compared to the same mass of microparticles. This quantitative method is shown to be capable of accurately and directly measuring antibody bound to magnetic particles and is independent of the conjugation method or type of magnetic particle.

Mg metal is a promising anode material for next generation rechargeable battery due to its dendrite-free deposition and high capacity. However, the best cathode for rechargeable Mg battery was based on high molecular weight MgxMo3S4, thus rendering full cell energetically uncompetitive. To increase energy density, high capacity cathode material like sulfur is proposed. However, to date, only limited work has been reported on Mg/S system, all plagued by poor reversibility attributed to the formation of electrochemically inactive MgSx species. Here, we report a new strategy, based on the effect of Li+ in activating MgSx species, to conjugate a dendrite-free Mg anode with a reversible polysulfide cathode and present a truly reversible Mg/S battery with capacity up to 1000 mAh/gs for more than 30 cycles. Mechanistic insights supported by spectroscopic and microscopic characterization strongly suggest that the reversibility arises from chemical reactivation of MgSx by Li+.

Carbon/metal oxide composites are considered promising materials for high energy density supercapacitors. So far, impregnation of the oxide into ordered mesoporous carbon materials has been demonstrated either in hard-templated carbon synthesized by using ordered mesoporous silica or alumina scaffolds, or soft-templated carbon derived from surfactant micelles. The hard-template method can provide a high pore volume but the instability of these mesostructures hinders total electrode performances upon oxide impregnation. While the soft-template methods can provide a stable mesostructure, these methods produce scaffolds with a much smaller pore volume and surface area, leading to limited metal oxide loading and electrode capacitance. Herein, anodized aluminum oxide (AAO) and triblock copolymer F127 are used together as hard and soft-templates to fabricate ordered mesoporous carbon nanowires (OMCNWs) as a host material for Fe2O3 nanoparticles. This dual-template strategy provides a high pore volume and surface area OMCNW that retains its stable structure even for high metal oxide loading amounts. Additionally, the unique nanowire morphology and mesoporous structure of the OMCNW/Fe2O3 facilitate high ionic mobility in the composite, leading to >260 F g−1 specific capacitance with good rate capability and cycling stability. This work highlights the dual-template approach as a promising strategy for the fabrication of next generation heterogeneous composites for electrochemical energy storage and conversion.

Carbon-based electrochemical double-layer capacitors and pseudocapacitors, consisting of a symmetric configuration of electrodes, can deliver much higher power densities than batteries, but they suffer from low energy densities. Herein, we report the development of high energy and power density supercapacitors using an asymmetric configuration of Fe2O3 and MnO2 nanoparticles incorporated into 3D macroporous graphene film electrodes that can be operated in a safe and low-cost aqueous electrolyte. The gap in working potential windows of Fe2O3 and MnO2 enables the stable expansion of the cell voltage up to 1.8 V, which is responsible for the high energy density (41.7 Wh kg–1). We employ a household microwave oven to simultaneously create conductivity, porosity, and the deposition of metal oxides on graphene films toward 3D hybrid architectures, which lead to a high power density (13.5 kW kg–1). Such high energy and power densities are maintained for over 5000 cycles, even during cycling at a high current density of 16.9 A g–1.Keywords: graphene; hybrid film; metal oxide; microwave; supercapacitor

The combination of high electronic conductivity, enhanced ionic mobility, and high pore volume make ordered mesoporous carbons promising scaffolds for active energy storage materials. However, mesoporous morphology and structural stability needs to be more thoroughly addressed. In this paper, we demonstrate Fe2O3 impregnation into 1D cylindrical (FDU-15), 2D hexagonal (CMK-3), and 3D bicontinuous (CMK-8) symmetries of mesoporous carbons. We use these materials for a systematic study of the effect of mesoporous architecture on the structure stability, ion mobility, and performance of mesoporous composite electrodes. By optimization of the porous structure, the oxide impregnation enabled relatively high performance: >650 F g−1 of Fe2O3 and >200 F g−1 total capacitance. This work highlights the new considerations of structure degradation in different pore symmetries with active material impregnation and its effect on ion mobility and electrochemical performance in porous scaffold electrodes. The results show that the most commonly used 2D CMK-3 is not suitable as a host material due to its poor structure stability and ion mobility, while the 1D FDU-15 and 3D CMK-8 have their own merits related to framework stability and porous structures.

A wide range of metal oxides have been studied as pseudocapitors, with the goal of achieving higher power than traditional batteries and higher energy than traditional capacitors. However, most metal oxides have relatively low conductivity, and the few exceptions, like RuO2, are prohibitively expensive. Mixed metal oxides provided an opportunity to incorporate small amounts of expensive materials to enhance the performance of a less expensive, poorer performing material. Here, by homogeneously co-depositing a small amount of energy dense and conductive RuO2 into MnO2 nanowires, we demonstrate an improvement in specific capacitance. Importantly, we also demonstrate that this improvement is not primarily provided by redox activity of RuO2, but rather by improvement of the composite conductivity. A series of RuO2–MnO2 composite nanowires with different RuO2 loading percentages have been synthesized by performing co-electrodeposition in a porous alumina template. The structure of these RuO2–MnO2 nanowires is characterized by TEM and SEM. EDS mapping shows that RuO2 is well distributed in MnO2 matrix nanowires. The chemical constituents and the phase of these composite nanowires are confirmed by X-ray photoelectron and Raman spectroscopy. The amount of RuO2 is controlled by varying the concentrations of RuCl3 and MnAc2 in the deposition solution. The precise masses of MnO2 and RuO2 are determined by ICP-AES elemental analysis. MnO2 nanowires with 6.70 wt% RuO2 demonstrate a specific capacitance of 302 F g−1 at 20 mV s−1, compared to 210 F g−1 for pristine MnO2 nanowires. Investigation of the RuO2 loading amount effect was conducted by electrochemical impedance spectroscopy (EIS) and deconvolution of capacitances, using methods previously reported by both Dunn and Transsiti. The RuO2–MnO2 nanowires studied here demonstrate a simple, straighforward method to overcome the intrinsically poor conductivity of MnO2, and clarify the source of RuO2's contribution to the improved performance.

Magnesium batteries have been considered to be one of the promising beyond lithium ion technologies due to magnesium's abundance, safety, and high volumetric capacity. However, very few materials show reversible performance as a cathode in magnesium ion systems. We present herein the best reported cycling performances of MnO2 as a magnesium battery cathode material. We show that the previously reported poor Mg2+ insertion/deinsertion capacities in MnO2 can be greatly improved by synthesizing self-standing nanowires and introducing a small amount of water molecules into the electrolyte. Electrochemical and elemental analysis results revealed that the magnitude of Mg2+ insertion into MnO2 highly depends on the ratio between water molecules and Mg2+ ions present in the electrolyte and the highest Mg2+ insertion capacity was observed at a ratio of 6H2O/Mg2+ in the electrolyte. We demonstrate for the first time, that MnO2 nanowire electrode can be “activated” for Mg2+ insertion/deinsertion by cycling in water containing electrolyte resulting in enhanced reversible Mg2+ insertion/deinsertion even with the absence of water molecules. The MnO2 nanowire electrode cycled in dry Mg electrolyte after activation in water-containing electrolyte showed an initial capacity of 120 mA h g−1 at a rate of 0.4 C and maintained 72% of its initial capacity after 100 cycles.

•Dense mesoscale architectures of nanostructures offer high power energy storage.•These present new science challenges intrinsic to the mesoscale.•Dense nanostructure assemblies alter ion and electron dynamics.•Controlling defects and degradation is essential at the mesoscale.•Architectural design strongly impacts ion, electron, and defect behavior.We examine the scientific challenges and opportunities presented at the mesoscale in the context of employing nanostructures for electrical energy storage. In order to capitalize on the power–energy and charge/discharge cycling stability that nanostructures offer, massive assemblies of nanostructures in networks must be organized into dense mesoscale architectures. With a fairly wide variety of architectures already demonstrated and more expected, the essential questions are whether regular or random 3-D arrangements are favorable, which embodiments should show best performance, and at what dimensional scaling? Dense packing raises challenging new questions about ion available and transport in highly confined electrolyte nanoenvironments, as well as designs to balance ion transport in electrolyte and electron transport in electrodes over distances long compared to nanostructure characteristic dimensions. Architectures and dimensional scaling present important issues of defects, statistical outliers, and their dynamic evolution, which in turn control degradation and failure phenomena. These considerations promise a rich set of mesoscale scientific challenges crucial to exploiting storage nanostructures in mesoscale architectures for energy storage.

A subnanometer gap-separated linear chain gold nanoparticle (AuNP) silica nanotube peapod (SNTP) was fabricated by self-assembly. The geometrical configurations of the AuNPs inside the SNTPs were managed in order to pose either a single-line or a double-line nanostructure by controlling the diameters of the AuNPs and the orifice in the silica nanotubes (SNTs). The AuNPs were internalized and self-assembled linearly inside the SNTs by capillary force using a repeated wet–dry process on a rocking plate. Transmission electron microscopy (TEM) images clearly indicated that numerous nanogap junctions with sub-1-nm distances were formed among AuNPs inside SNTs. Finite-dimension time domain (FDTD) calculations were performed to estimate the electric field enhancements. Polarization-dependent surface-enhanced Raman scattering (SERS) spectra of bifunctional aromatic linker p-mercaptobenzoic acid (p-MBA)-coated AuNP-embedded SNTs supported the linearly aligned nanogaps. We could demonstrate a silica wall-protected nanopeapod sensor with single nanotube sensitivity. SNTPs have potential application to intracellular pH sensors after endocytosis in mammalian cells for practical purposes. The TEM images indicated that the nanogaps were preserved inside the cellular constituents. SNTPs exhibited superior quality SERS spectra in vivo due to well-sustained nanogap junctions inside the SNTs, when compared to simply using AuNPs without any silica encapsulation. By using these SNTPs, a robust intracellular optical pH sensor could be developed with the advantage of the sustained nanogaps, due to silica wall-protection.

MnO2 as a material for supercapacitors is generally predicted to insert only one cation per unit cell. However, it is shown here to reversibly insert more than one cation in an organic electrolyte; however, in an aqueous electrolyte, the insertion ion is actually shown to be a combination of protons and cations.

Nickel nanotubes have been synthesized by the popular and versatile method of template-assisted electrodeposition, and a surface-directed growth mechanism based on the adsorption of the nickel–borate complex has been proposed.

A redox exchange mechanism between potassium perruthenate (KRuO4) and the functional groups of selected polymers is used here to induce RuO2 into and onto conductive polymer nanowires by simply soaking the polymer nanowire arrays in KRuO4 solution. Conductive polymer nanowire arrays of polypyrrole (PPY) and poly(3,4-ethylenedioxythiophene) (PEDOT) were studied in this work. SEM and TEM results show that the RuO2 material was distributed differently in the PPY and PEDOT nanowire matrices. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to confirm the dispersion and formation of RuO2 materials in these polymer nanowires. Cyclic voltammetry and galvanostatic charge–discharge experiments were used to characterize their electrochemical performance. RuO2–polymer samples prepared with a 6 min soaking time in 10 mM KRuO4 solution show a high specific capacitance of 371 F g−1 and 500 F g−1 for PEDOT-based and PPY-based composite nanowires, respectively. This is attributed to the high exposure area of the conductive RuO2 and the good conductivity of the polymer matrix. This work demonstrates a simple method to synthesize heterogeneous polymer based-materials through the redox reaction between conductive polymers and high oxidation state transition metal oxide ions. Different heterogeneous nanocomposites were obtained depending on the polymer properties, and high energy storage performance of the metal oxides can be achieved within these heterogeneous nanostructures.

Supercapacitive properties of ruthenium oxide (RuO2) nanoparticles electrodeposited onto the indium tin oxide (ITO) nanopillars were investigated. Compared to conventional planar current collectors, this coaxially nanostructured current collector–electrode system can provide increased contact for efficient charge transport, and the internanopillar spacing allows easy access of electrolyte ions. The morphological and electrochemical properties depended on the thickness of the RuO2 layers, i.e., the number of electrodeposition cycles. A maximum specific capacitance, Csp, of 1235 F/g at a scan rate of 50 mV/s was achieved for the 30-cycle deposited RuO2–ITO nanopillars. The other capacitive properties such as electrochemical reversibility and Csp retention at high scan rates also improved greatly.

We report improved cycling performance of high-voltage LiNi0.5Mn1.5O4 cathode for lithium-ion batteries by modifying its surface with ultrathin layer coating of Al2O3 (<1 nm) using atomic layer deposition (ALD) technique. Four and six layers of ALD Al2O3 were coated directly on the porous LiNi0.5Mn1.5O4 nanoparticle (~200 nm) slurry composite. Electrochemical characterization results show that LiNi0.5Mn1.5O4 electrode with four and six layers of ALD Al2O3 maintained 92 and 98 % of their initial capacity after 200 cycles, respectively, in comparison to bare LiNi0.5Mn1.5O4 electrode which showed 84 % capacity retention. We show that the ALD Al2O3 coated cathode surface is protected from undesired side reactions occurring at the electrode/electrolyte interface. For the first time, we used XPS studies to investigate the surface chemistry of ultrathin ALD Al2O3 coated LiNi0.5Mn1.5O4 and confirmed that the ultrathin ALD Al2O3 layer reduces side reactions involving organic components of the electrolyte decomposition product in high-voltage cathodes.

A series of simple hierarchical self-assembly steps achieve self-organization from the centimeter to the subnanometer-length scales in the form of square-centimeter arrays of linear nanopores, each one having a single chiral helical nanofilament of large internal surface area and interfacial interactions based on chiral crystalline molecular arrangements.

Intracellular glutathione-triggered doxorubicin release from silica nanotubes with hydrophobic labile cap was demonstrated for the drug-resistant cancer cell treatment.

In this work we describe three different trends of pore growth for anodic aluminum oxide nanopores based on their dependence on prepatterned interpore distances. Nanopatterned hexagonal concave arrays were formed by focused ion beam (FIB) lithography on aluminum foil with interpore distances in the range of 100 to 240 nm and the Al foil was anodized under the standard conditions known to result in a 100 nm interpore distance. This method allowed a systematic investigation of pore formation under the non-equilibrium conditions created by the FIB prepatterning. The pore diameter and the pore growth direction, which are affected by the interpore distance, were measured by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis with ion milling. When the interpore distance increases from 100 to 140 nm, the pore diameter becomes larger and nanopores are slightly tilted but maintained the interpore distance and straightness. As the interpore distance increases from 150 to 180 nm, the pore diameter becomes smaller and each nanopore starts to split into two nanopores. At interpore distances of over 190 nm, prepatterned concaves are developed into round flask-shaped nanosacks instead of one-dimensional tubes, and then these are split into three more sub-nanopores. The fundamental characteristics of anodic aluminum oxidation are discussed in accordance with various prepatterned concaves in the nanopore growth processes, providing a rational theory for the design of various complex 3-D AAO structures that can be controlled by prepatterning.

A review of electrochemically synthesized nanomaterials with different controllable architectures for electrochemical energy storage devices is shown. It is demonstrated that these nano-architectures can be created either by electrodeposition or by the electrochemical transformation of materials. Electrochemical synthesis is presented here as it provides intimate contact between the electrode and current collector and also promotes an electronic pathway for all materials to be connected to the circuit. Although still in their infancy, electrosynthesized nano-architectures show promise to be used in future electrochemical energy storage devices as utilization of this method bypasses the need for bulky conductive additives and electrochemically inactive binders. Furthermore, electrochemical transformations can be used to create additional architectural features or change the chemical make-up of the electrode. This review is meant to show the creativity of current science when it comes to these nano-architectured electrodes. It is organized by technique used for synthesis including hard template, soft template, and template-free synthesis along with electrochemical transformation techniques.

This study is reported on the effect of nanowire density on the ease of pellicle formation and the enrichment of plasma membrane (PM) proteins for analysis by mass spectrometry. An optimized synthesis is reported for iron silicate nanowires (ISNW) with a narrow size range of 900 ± 400 nm in length and 200 nm diameter. The nanowires were coated with Al2O3 and used to form pellicles around suspended multiple myeloma cells, which acted as a model for cells recovered from tissue samples. Lighter alumina-coated silica nanowires were also synthesized (Kim et al., doi:10.2217/NNM.13.96, 2013), which allowed a comparison of the construction of the two pellicles and of the effect of nanowire density on PM enrichment. Evidence is offered that the dense nanowire pellicle does not crush or distort these mammalian cells. Finally, the pellicles were incorporated into a mass spectrometry-based proteomic workflow to analyze transmembrane proteins in the PM. In contrast to a prior comparison of the effect of density with nanoparticles pellicles (Choksawangkarn et al. J Proteome Res 455 12:1134–1141, 2013), nanowire density was not found to significantly affect the enrichment of the PM. However, nanowires with a favorable aspect for pellicle formation are more easily and reliably produced with iron silicate than with silica. In addition, the method for pellicle formation was optimized through the use of ISNW, which is crucial to the improvement of PM protein enrichment and analysis.

Characterization of materials in confined spaces, rather than attempting to extrapolate from bulk material behavior, requires the development of new measurement techniques. In particular, measurements of individual meso- or nanoscale objects can provide information about their structure which is unavailable by other means. In this report, we perform measurements of ion currents through a few hundred nanometer long MnO2 rods deposited in single polymer pores. The recorded current confirms an existence of a meshlike character of the MnO2 structure and probes the effective size of the mesh voids and the polarity of surface charges. The recorded ion current through deposited MnO2 structure also suggests that the signal is mostly due to metal cations and not to protons. This is the first time that ionic current measurements have been used to characterize mesoporous structure of this important electrode material.

Hierarchical nanostructures have generated great interest in the energy, materials, and chemical sciences due to the synergic properties of their composite architectures. Herein, a hierarchical MnO2 nanofibril/nanowire array is successfully synthesized. The structure consists of a conformal layer of MnO2 nanofibrils evenly distributed on the surface of the individual MnO2 nanowires. The synthetic mechanism of this hierarchical structure is characterized by electrochemical measurements, Raman spectroscopy, EELS, and electron microscopy. This material was then investigated at slow scan rates for its charge storage mechanisms in different solvents. In aqueous electrolyte, the nanofibrils show a capacitance almost purely dedicated to double-layer and surface adsorption processes, while in an acetonitrile electrolyte, the nanofibrils’ capacitance comes mainly from a cation insertion process. This material was also tested at high scan rates in aqueous solution for its practical supercapacitor capabilities. The material shows a large capacitance of 298 F/g at 50 mV/s and 174 F/g at 250 mV/s. It also maintains 85.2% of its capacitance after 1000 cycles. The material also displays easily controllable parameters such as nanowire length, nanowire diameter, and amount of nanofibril material which is shown here to affect the capacitance dramatically.Keywords: electrochemical energy storage; hierarchical; manganese oxide; nanowires; self-limiting; template

Cellulose fibers with porous structure and electrolyte absorption properties are considered to be a good potential substrate for the deposition of energy material for energy storage devices. Unlike traditional substrates, such as gold or stainless steel, paper prepared from cellulose fibers in this study not only functions as a substrate with large surface area but also acts as an interior electrolyte reservoir, where electrolyte can be absorbed much in the cellulose fibers and is ready to diffuse into an energy storage material. We demonstrated the value of this internal electrolyte reservoir by comparing a series of hierarchical hybrid supercapacitor electrodes based on homemade cellulose paper or polyester textile integrated with carbon nanotubes (CNTs) by simple solution dip and electrodeposited with MnO2. Atomic layer deposition of Al2O3 onto the fiber surface was used to limit electrolyte absorption into the fibers for comparison. Configurations designed with different numbers of ion diffusion pathways were compared to show that cellulose fibers in paper can act as a good interior electrolyte reservoir and provide an effective pathway for ion transport facilitation. Further optimization using an additional CNT coating resulted in an electrode of paper/CNTs/MnO2/CNTs, which has dual ion diffusion and electron transfer pathways and demonstrated superior supercapacitive performance. This paper highlights the merits of the mesoporous cellulose fibers as substrates for supercapacitor electrodes, in which the water-swelling effect of the cellulose fibers can absorb electrolyte, and the mesoporous internal structure of the fibers can provide channels for ions to diffuse to the electrochemical energy storage materials.Keywords: carbon nanotubes; cellulose fibers; electrolyte absorption; electron transfer; ion diffusion; manganese oxide; supercapacitors

Poly (3,4-(2-methylene)propylenedioxythiophene) (PMProDot) nanotubes were synthesized within the pores of polycarbonate and were further modified with styrene and vinylcarbazole by a one step electrochemical method through the methylene functional group. The enhanced electrochemical and electrochromic properties of composite nanotubes were investigated using FTIR, UV/Vis absorbance spectroscopy, and AFM.

Flexible electronics such as wearable electronic clothing, paper-like electronic devices, and flexible biomedical diagnostic devices are expected to be commercialized in the near future. Flexible energy storage will be needed to power these devices. Supercapacitor devices based on freestanding nanowire arrays are promising high power sources for these flexible electronics. Electrodes for these supercapacitor devices consisting of heterogeneous coaxial nanowires of poly (3,4-ethylenedioxythiophene) (PEDOT)-shell and MnO2-core materials have been shown in a half cell system to have improved capacitance and rate capabilities when compared to their pure nanomaterials; however, their performance in a full cell system has not been fully investigated. Herein, these coaxial nanowires are tested in both a symmetric and an asymmetric (utilizing a PEDOT nanowire anode) full cell configuration in the aspect of charge storage, charge rate, and flexibility without using any carbon additives and polymer binders. It is found that the asymmetric cell outperforms the symmetric cell in terms of energy density, rate capability, and cycle ability. The asymmetric device's electrode materials display an energy density of 9.8 Wh/kg even at a high power density of 850 W kg−1. This device is highly flexible and shows fast charging and discharging while still maintaining 86% of its energy density even under a highly flexed state. The total device is shown to have a total capacitance of 0.26 F at a maximum voltage of 1.7 V, which is capable of providing enough energy to power small portable devices.

Nanostructures can improve the performance of electrical energy storage devices. Recently, metal–insulator–metal (MIM) electrostatic capacitors fabricated in a three-dimensional cylindrical nanotemplate of anodized aluminum oxide (AAO) porous film have shown profound increase in device capacitance (100× or more) over planar structures. However, inherent asperities at the top of the nanostructure template cause locally high field strengths and lead to low breakdown voltage. This severely limits the usable voltage, the associated energy density (1/2CV2), and thus the operational charge–discharge window of the device. We describe an electrochemical technique, complementary to the self-assembled template pore formation process in the AAO film, that provides nanoengineered topographies with significantly reduced local electric field concentrations, enabling breakdown fields up to 2.5× higher (to >10 MV/cm) while reducing leakage current densities by 1 order of magnitude (to ∼10–10 A/cm2). In addition, we consider and optimize the AAO template and nanopore dimensions, increasing the capacitance per planar unit area by another 20%. As a result, the MIM nanocapacitor devices achieve an energy density of ∼1.5 Wh/kg—the highest reported.Keywords: anodic aluminum oxide; atomic layer deposition; energy storage; metal−insulator−metal capacitor; nanoengineering

In order to fulfil the future requirements of electrochemical energy storage, such as high energy density at high power demands, heterogeneous nanostructured materials are currently studied as promising electrode materials due to their synergic properties, which arise from integrating multi-nanocomponents, each tailored to address a different demand (e.g., high energy density, high conductivity, and excellent mechanical stability). In this article, we discuss these heterogeneous nanomaterials based on their structural complexity: zero-dimensional (0-D) (e.g. core–shell nanoparticles), one-dimensional (1-D) (e.g. coaxial nanowires), two-dimensional (2-D) (e.g.graphene based composites), three-dimensional (3-D) (e.g. mesoporous carbon based composites) and the even more complex hierarchical 3-D nanostructured networks. This review tends to focus more on ordered arrays of 1-D heterogeneous nanomaterials due to their unique merits. Examples of different types of structures are listed and their advantages and disadvantages are compared. Finally a future 3-D heterogeneous nanostructure is proposed, which may set a goal toward developing ideal nano-architectured electrodes for future electrochemical energy storage devices.

High power electrical energy storage systems are becoming critical devices for advanced energy storage technology. This is true in part due to their high rate capabilities and moderate energy densities which allow them to capture power efficiently from evanescent, renewable energy sources. High power systems include both electrochemical capacitors and electrostatic capacitors. These devices have fast charging and discharging rates, supplying energy within seconds or less. Recent research has focused on increasing power and energy density of the devices using advanced materials and novel architectural design. An increase in understanding of structure-property relationships in nanomaterials and interfaces and the ability to control nanostructures precisely has led to an immense improvement in the performance characteristics of these devices. In this review, we discuss the recent advances for both electrochemical and electrostatic capacitors as high power electrical energy storage systems, and propose directions and challenges for the future. We asses the opportunities in nanostructure-based high power electrical energy storage devices and include electrochemical and electrostatic capacitors for their potential to open the door to a new regime of power energy.

MnO2/TiN nanotubes are fabricated using facile deposition techniques to maximize the surface area of the electroactive material for use in electrochemical capacitors. Atomic layer deposition is used to deposit conformal nanotubes within an anodic aluminium oxide template. After template removal, the inner and outer surfaces of the TiN nanotubes are exposed for electrochemical deposition of manganese oxide. Electron microscopy shows that the MnO2 is deposited on both the inside and outside of TiN nanotubes, forming the MnO2/TiN nanotubes. Cyclic voltammetry and galvanostatic charge–discharge curves are used to characterize the electrochemical properties of the MnO2/TiN nanotubes. Due to the close proximity of MnO2 with the highly conductive TiN as well as the overall high surface area, the nanotubes show very high specific capacitance (662 F g−1 reported at 45 A g−1) as a supercapacitor electrode material. The highly conductive and mechanically stable TiN greatly enhances the flow of electrons to the MnO2 material, while the high aspect ratio nanostructure of TiN creates a large surface area for short diffusion paths for cations thus improving high power. Combining the favourable structural, electrical and energy properties of MnO2 and TiN into one system allows for a promising electrode material for supercapacitors.

The formation mechanism of a coaxial manganese oxide/poly(3,4-ethylenedioxythiophene) (MnO2/PEDOT) nanowire is elucidated herein by performing electrodeposition of MnO2 and PEDOT on Au-sputtered nanoelectrodes with different shapes (ring and flat-top, respectively) within the 200 nm diameter pores of an anodized aluminum oxide (AAO) template. It is found that PEDOT prefers to grow on the sharp edge of the ring-shaped electrode, while MnO2 is more likely to deposit on the flat-top electrode due to its smooth surface. The formation of coaxial nanowires is shown to be a result of simultaneous growth of core MnO2 and shell PEDOT by an analysis of the current density resulting from electrochemical deposition. Furthermore, the structures of the MnO2/PEDOT coaxial nanowires were studied for their application as supercapacitors by modifying their coelectrodeposition potential. A potential of 0.70 V is found to be the most favorable condition for synthesis of MnO2/PEDOT coaxial nanowires, resulting in a high specific capacitance of 270 F/g. Additionally, other heterogeneous MnO2/PEDOT nanostructures are produced, such as nanowires consisting of MnO2 nanodomes with PEDOT crowns as well as segmented MnO2/PEDOT nanowires. This is accomplished by simply adjusting the parameters of the electrochemical deposition. Finally, in smaller diameter (50 nm) AAO channels, MnO2 and PEDOT are found to be partially assembled into coaxial nanowires due to the alternative depletion of Mn(II) ions and EDOT monomers in the smaller diameter pores.Keywords: coaxial nanowires; electrochemical energy storage; energy density; heterogeneous; lithium-ion battery; MnO2; PEDOT; power density; supercapacitor; template synthesis

We report the synthesis of composite RuO2/poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes with high specific capacitance and fast charging/discharging capability as well as their potential application as electrode materials for a high-energy and high-power supercapacitor. RuO2/PEDOT nanotubes were synthesized in a porous alumina membrane by a step-wise electrochemical deposition method, and their structures were characterized using electron microscopy. Cyclic voltammetry was used to qualitatively characterize the capacitive properties of the composite RuO2/PEDOT nanotubes. Their specific capacitance, energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. The pseudocapacitance behavior of these composite nanotubes originates from ion diffusion during the simultaneous and parallel redox processes of RuO2 and PEDOT. We show that the energy density (specific capacitance) of PEDOT nanotubes can be remarkably enhanced by electrodepositing RuO2 into their porous walls and onto their rough internal surfaces. The flexible PEDOT prevents the RuO2 from breaking and detaching from the current collector while the rigid RuO2 keeps the PEDOT nanotubes from collapsing and aggregating. The composite RuO2/PEDOT nanotube can reach a high power density of 20 kW kg−1 while maintaining 80% energy density (28 Wh kg−1) of its maximum value. This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the composite material and access their internal surfaces, while a thin wall provides a short diffusion distance to facilitate ion transport. The high energy density originates from the RuO2, which can store high electrical/electrochemical energy intrinsically. The high specific capacitance (1217 F g−1) which is contributed by the RuO2 in the composite RuO2/PEDOT nanotube is realized because of the high specific surface area of the nanotubular structures. Such PEDOT/RuO2 composite nanotube materials are an ideal candidate for the development of high-energy and high-power supercapacitors.

MnO2 nanoparticle enriched poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires are fabricated by simply soaking the PEDOT nanowires in potassium permanganate (KMnO4) solution. The structures of these MnO2 nanoparticle enriched PEDOT nanowires are characterized by SEM and TEM, which show that the MnO2 nanoparticles have uniform sizes and are finely dispersed in the PEDOT matrix. The chemical constituents and bonding of these composite nanowires are characterized by energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and infrared spectroscopy, which indicate that the formation and dispersion of these MnO2 nanoparticles into the nanoscale pores of the PEDOT nanowires are most likely triggered by the reduction of KMnO4 via the redox exchange of permanganate ions with the functional group on PEDOT. Varying the concentrations of KMnO4 and the reaction time controls the loading amount and size of the MnO2 nanoparticles. Cyclic voltammetry and galvanostatic charge−discharge are used to characterize the electrochemical properties of these MnO2 nanoparticle loaded PEDOT nanowires. Due to their extremely high exposed surface area with nanosizes, the pristine MnO2 nanoparticles in these MnO2 nanoparticle enriched PEDOT nanowires show very high specific capacitance (410 F/g) as the supercapacitor electrode materials as well as high Li+ storage capacity (300 mAh/g) as cathode materials of Li ion battery, which boost the energy storage capacity of PEDOT nanowires to 4 times without causing excessive volume expansion in the polymer. The highly conductive and porous PEDOT matrix facilitates fast charge/discharge of the MnO2 nanoparticles and prevents them from agglomerating. These synergic properties enable the MnO2 nanoparticle enriched PEDOT nanowires to be promising electrode materials for supercapacitors and lithium ion batteries.Keywords: electrochemical energy storage; heterostructured nanomaterials; lithium ion battery; manganese oxide; nanowire; PEDOT; supercapacitor

Metal-enhanced multiphoton absorption polymerization (MEMAP) is studied using gold nanowires with a set of three different photoresists. Photoresists that employ radical and cationic polymerization are investigated. In all cases, MEMAP is strongly correlated with multiphoton-absorption-induced luminescence (MAIL) of the nanowires. Wavelength-dependent studies indicate that the dominant mechanism for MEMAP is not field-enhanced two-photon absorption of the photoinitiator, but rather single-photon excitation of the photoinitiator by the broadband MAIL emission.

Multifunctional silica nanotubes (SNTs) are being widely used for many biomedical applications due to their structural benefits. Controlling the structure of the open end of an SNT is a crucial step for drug/gene delivery and for fabrication of multifunctional SNTs. We developed a mechanical capsulation method to fabricate caps at the ends of SNTs. A thin layer of malleable capping materials (Au, Ag, PLGA) was deposited onto the surface of an SNT-grown AAO template. Capped SNTs were then obtained by hammering with alumina microbeads. For a proof-of-concept experiment, we demonstrated dye-encapsulated SNTs without any chemical functionalizations. Since a mechanical approach is free of the issue of chemical compatibility between cargo molecules and capping materials, the method can provide an effective platform for the preparation of smart multifunctional nanotubes for biomedical applications.

Recent advances in nanomaterials have paved the way to design innovative platforms for creating nano-barcodes for a broad range of potential applications. This feature article reviews various strategies for a dispersible array of encoded one-dimensional (1D) nano/microstructures which allow highly multiplexed analysis. 1D nano-barcodes susceptible to encoding with a number of distinct patterns are exceedingly promising for the development of much improved array systems in fields such as pharmaceutical research, disease diagnostics, and gene profiling.

Conductive polymers exhibit several interesting and important properties, such as metallic conductivity and reversible convertibility between redox states. When the redox states have very different electrochemical and electronic properties, their interconversion gives rise to changes in the polymers’ conformations, doping levels, conductivities, and colors, useful attributes if they are to be applied in displays, energy storage devices, actuators, and sensors. Unfortunately, the rate of interconversion is usually slow, at best on the order a few hundred milliseconds, because of the slow transport of counterions into the polymer layer to balance charge. This phenomenon is one of the greatest obstacles toward building rapidly responsive electrochemical devices featuring conductive polymers. One approach to enhancing the switching speed is decreasing the diffusion distance for the counterions in the polymer. We have found that nanotubular structures are good candidates for realizing rapid switching between redox states because the counterions can be readily doped throughout the thin nanotube walls. Although the synthesis of conductive polymer nanotubes can be performed using electrochemical template synthesis, the synthetic techniques and underlying mechanisms controlling the nanotube morphologies are currently not well established. We begin this Account by discussing the mechanisms for controlling the structures from hollow nanotubes to solid nanowires. The applied potential, monomer concentration, and base electrode shape all play important roles in determining the nanotubes’ morphologies. A mechanism based on the rates of monomer diffusion and reaction allows the synthesis of nanotubes at high oxidation potentials; a mechanism dictated by the base-electrode shape dominates at very low oxidation potentials. The structures of the resulting conductive polymer nanotubes, such as those of poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole, can be characterized using scanning electron microscopy and transmission electron microscopy. We also discuss these materials in terms of their prospective use in nanotube-based electrochemical devices. For example, we describe an electrochromic device incorporating PEDOT nanotubes that exhibits an ultrafast color switching rate (<10 ms) and strong coloration. In addition, we report a supercapacitor based on PEDOT nanotubes that can provide more than 80% of its own energy density, even at power demands as high as 25 kW/kg.

“Template synthesized” silica nanotubes (SNTs) provide unique features such as end functionalization to control drug release, inner voids for loading biomolecules, and distinctive inner and outer surfaces that can be differentially functionalized for targeting and biocompatibility. Very limited information is available about their biological interactions. This work evaluates the influence of size and surface charge of SNTs on cellular toxicity and uptake. Results additionally indicate endocytosis to be one possible mechanism of internalization of SNTs.

In the past few decades, nanoscale materials have been widely used for controlled release applications. Importantly, many researches have focused on multifunctional nanoparticles for targeted delivery of bioactive and imaging agents as therapeutics and diagnostics. Recent advances in nanotechnology have made possible the design and development of tubular nanoscale particles called nanotubes. The tubular shape of such particles is highly attractive since it is possible to differentially functionalize the inner and outer surfaces to facilitate drug loading, biocompatibility and biorecognition. Novel synthetic strategies allow the fabrication of tubular structures with well-defined diameters and lengths. This can have important implications in biodistribution, subcellular trafficking and drug release. In this article the biomedical applications of nanotubes will be discussed with emphasis on the template synthesis of composite nanotubes containing silica and iron oxide that have potential use in drug delivery, magnetic resonance imaging (MRI), and chemical and biochemical separations.

Inorganic nanoparticles, such as carbon nanotubes, quantum dots and gold nanoshells, have been adopted for biomedical use, due to their unique optical and physical properties. Compared to conventional materials, inorganic nanomaterials have several advantages such as simple preparative processes and precise control over their shape, composition and size. In addition, inorganic porous nanomaterials are fundamentally advantageous for developing multifunctional nanomaterials, due to their distinctive inner and outer surfaces. In this review, we describe recent developments of hollow and porous inorganic nanomaterials in nanomedicine, especially for imaging/diagnosis and photothermal therapy.

Recent cytotoxicity studies on carbon nanotubes have shown that the biocompatibility of nanomaterial might be determined mainly by surface functionalization, rather than by size, shape, and material. Although the cytotoxicity for individual inorganic hollow nanomaterials should be extensively tested in vitro and in vivo, potential safety concerns about the use of inorganic nanomaterials in biomedical applications could be alleviated with proper surface treatment. Inorganic hollow nanoparticles and nanotubes have attracted great interest in nanomedicine because of the generic transporting ability of porous material and a wide range of functionality that arises from their unique optical, electrical, and physical properties. In this review, we describe recent developments of hollow and porous inorganic nanomaterials in nanomedicine, especially for drug/gene delivery.

We report the synthesis of composite RuO2/poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes with high specific capacitance and fast charging/discharging capability as well as their potential application as electrode materials for a high-energy and high-power supercapacitor. RuO2/PEDOT nanotubes were synthesized in a porous alumina membrane by a step-wise electrochemical deposition method, and their structures were characterized using electron microscopy. Cyclic voltammetry was used to qualitatively characterize the capacitive properties of the composite RuO2/PEDOT nanotubes. Their specific capacitance, energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. The pseudocapacitance behavior of these composite nanotubes originates from ion diffusion during the simultaneous and parallel redox processes of RuO2 and PEDOT. We show that the energy density (specific capacitance) of PEDOT nanotubes can be remarkably enhanced by electrodepositing RuO2 into their porous walls and onto their rough internal surfaces. The flexible PEDOT prevents the RuO2 from breaking and detaching from the current collector while the rigid RuO2 keeps the PEDOT nanotubes from collapsing and aggregating. The composite RuO2/PEDOT nanotube can reach a high power density of 20 kW kg−1 while maintaining 80% energy density (28 Wh kg−1) of its maximum value. This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the composite material and access their internal surfaces, while a thin wall provides a short diffusion distance to facilitate ion transport. The high energy density originates from the RuO2, which can store high electrical/electrochemical energy intrinsically. The high specific capacitance (1217 F g−1) which is contributed by the RuO2 in the composite RuO2/PEDOT nanotube is realized because of the high specific surface area of the nanotubular structures. Such PEDOT/RuO2 composite nanotube materials are an ideal candidate for the development of high-energy and high-power supercapacitors.

MnO2/TiN nanotubes are fabricated using facile deposition techniques to maximize the surface area of the electroactive material for use in electrochemical capacitors. Atomic layer deposition is used to deposit conformal nanotubes within an anodic aluminium oxide template. After template removal, the inner and outer surfaces of the TiN nanotubes are exposed for electrochemical deposition of manganese oxide. Electron microscopy shows that the MnO2 is deposited on both the inside and outside of TiN nanotubes, forming the MnO2/TiN nanotubes. Cyclic voltammetry and galvanostatic charge–discharge curves are used to characterize the electrochemical properties of the MnO2/TiN nanotubes. Due to the close proximity of MnO2 with the highly conductive TiN as well as the overall high surface area, the nanotubes show very high specific capacitance (662 F g−1 reported at 45 A g−1) as a supercapacitor electrode material. The highly conductive and mechanically stable TiN greatly enhances the flow of electrons to the MnO2 material, while the high aspect ratio nanostructure of TiN creates a large surface area for short diffusion paths for cations thus improving high power. Combining the favourable structural, electrical and energy properties of MnO2 and TiN into one system allows for a promising electrode material for supercapacitors.

Flexible electronics such as wearable electronic clothing, paper-like electronic devices, and flexible biomedical diagnostic devices are expected to be commercialized in the near future. Flexible energy storage will be needed to power these devices. Supercapacitor devices based on freestanding nanowire arrays are promising high power sources for these flexible electronics. Electrodes for these supercapacitor devices consisting of heterogeneous coaxial nanowires of poly (3,4-ethylenedioxythiophene) (PEDOT)-shell and MnO2-core materials have been shown in a half cell system to have improved capacitance and rate capabilities when compared to their pure nanomaterials; however, their performance in a full cell system has not been fully investigated. Herein, these coaxial nanowires are tested in both a symmetric and an asymmetric (utilizing a PEDOT nanowire anode) full cell configuration in the aspect of charge storage, charge rate, and flexibility without using any carbon additives and polymer binders. It is found that the asymmetric cell outperforms the symmetric cell in terms of energy density, rate capability, and cycle ability. The asymmetric device's electrode materials display an energy density of 9.8 Wh/kg even at a high power density of 850 W kg−1. This device is highly flexible and shows fast charging and discharging while still maintaining 86% of its energy density even under a highly flexed state. The total device is shown to have a total capacitance of 0.26 F at a maximum voltage of 1.7 V, which is capable of providing enough energy to power small portable devices.

In this work we describe three different trends of pore growth for anodic aluminum oxide nanopores based on their dependence on prepatterned interpore distances. Nanopatterned hexagonal concave arrays were formed by focused ion beam (FIB) lithography on aluminum foil with interpore distances in the range of 100 to 240 nm and the Al foil was anodized under the standard conditions known to result in a 100 nm interpore distance. This method allowed a systematic investigation of pore formation under the non-equilibrium conditions created by the FIB prepatterning. The pore diameter and the pore growth direction, which are affected by the interpore distance, were measured by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis with ion milling. When the interpore distance increases from 100 to 140 nm, the pore diameter becomes larger and nanopores are slightly tilted but maintained the interpore distance and straightness. As the interpore distance increases from 150 to 180 nm, the pore diameter becomes smaller and each nanopore starts to split into two nanopores. At interpore distances of over 190 nm, prepatterned concaves are developed into round flask-shaped nanosacks instead of one-dimensional tubes, and then these are split into three more sub-nanopores. The fundamental characteristics of anodic aluminum oxidation are discussed in accordance with various prepatterned concaves in the nanopore growth processes, providing a rational theory for the design of various complex 3-D AAO structures that can be controlled by prepatterning.

A review of electrochemically synthesized nanomaterials with different controllable architectures for electrochemical energy storage devices is shown. It is demonstrated that these nano-architectures can be created either by electrodeposition or by the electrochemical transformation of materials. Electrochemical synthesis is presented here as it provides intimate contact between the electrode and current collector and also promotes an electronic pathway for all materials to be connected to the circuit. Although still in their infancy, electrosynthesized nano-architectures show promise to be used in future electrochemical energy storage devices as utilization of this method bypasses the need for bulky conductive additives and electrochemically inactive binders. Furthermore, electrochemical transformations can be used to create additional architectural features or change the chemical make-up of the electrode. This review is meant to show the creativity of current science when it comes to these nano-architectured electrodes. It is organized by technique used for synthesis including hard template, soft template, and template-free synthesis along with electrochemical transformation techniques.

A redox exchange mechanism between potassium perruthenate (KRuO4) and the functional groups of selected polymers is used here to induce RuO2 into and onto conductive polymer nanowires by simply soaking the polymer nanowire arrays in KRuO4 solution. Conductive polymer nanowire arrays of polypyrrole (PPY) and poly(3,4-ethylenedioxythiophene) (PEDOT) were studied in this work. SEM and TEM results show that the RuO2 material was distributed differently in the PPY and PEDOT nanowire matrices. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to confirm the dispersion and formation of RuO2 materials in these polymer nanowires. Cyclic voltammetry and galvanostatic charge–discharge experiments were used to characterize their electrochemical performance. RuO2–polymer samples prepared with a 6 min soaking time in 10 mM KRuO4 solution show a high specific capacitance of 371 F g−1 and 500 F g−1 for PEDOT-based and PPY-based composite nanowires, respectively. This is attributed to the high exposure area of the conductive RuO2 and the good conductivity of the polymer matrix. This work demonstrates a simple method to synthesize heterogeneous polymer based-materials through the redox reaction between conductive polymers and high oxidation state transition metal oxide ions. Different heterogeneous nanocomposites were obtained depending on the polymer properties, and high energy storage performance of the metal oxides can be achieved within these heterogeneous nanostructures.

Magnesium batteries have been considered to be one of the promising beyond lithium ion technologies due to magnesium's abundance, safety, and high volumetric capacity. However, very few materials show reversible performance as a cathode in magnesium ion systems. We present herein the best reported cycling performances of MnO2 as a magnesium battery cathode material. We show that the previously reported poor Mg2+ insertion/deinsertion capacities in MnO2 can be greatly improved by synthesizing self-standing nanowires and introducing a small amount of water molecules into the electrolyte. Electrochemical and elemental analysis results revealed that the magnitude of Mg2+ insertion into MnO2 highly depends on the ratio between water molecules and Mg2+ ions present in the electrolyte and the highest Mg2+ insertion capacity was observed at a ratio of 6H2O/Mg2+ in the electrolyte. We demonstrate for the first time, that MnO2 nanowire electrode can be “activated” for Mg2+ insertion/deinsertion by cycling in water containing electrolyte resulting in enhanced reversible Mg2+ insertion/deinsertion even with the absence of water molecules. The MnO2 nanowire electrode cycled in dry Mg electrolyte after activation in water-containing electrolyte showed an initial capacity of 120 mA h g−1 at a rate of 0.4 C and maintained 72% of its initial capacity after 100 cycles.

Here we introduce a strategy for creating nanotube array electrodes which feature periodic regions of porous interconnections providing open pathways between adjacent nanotubes within the array, utilizing a combination of anodized aluminum oxide growth modification (AAO) and atomic layer deposition. These porous interconnected structures can then be used as testbed electrodes to explore the influence of mesoscale structure on the electrochemical properties of the interconnected mesoporous electrodes. Critically, these unique structures allow the solid state lithium diffusion pathways to be held essentially constant, while the larger structure is modified. While it was anticipated that this strategy would simply provide increased mass loading, the kinetics of the Li+ ion insertion reaction in the porous interconnected electrodes are dramatically improved, demonstrating significantly better capacity retention at high rates than their aligned counterparts. We utilize a charge deconvolution method to explore the kinetics of the charge storage reactions. We are able to trace the origin of the structural influence on rate performance to electronic effects within the electrodes.

MnO2 as a material for supercapacitors is generally predicted to insert only one cation per unit cell. However, it is shown here to reversibly insert more than one cation in an organic electrolyte; however, in an aqueous electrolyte, the insertion ion is actually shown to be a combination of protons and cations.

Intracellular glutathione-triggered doxorubicin release from silica nanotubes with hydrophobic labile cap was demonstrated for the drug-resistant cancer cell treatment.

Nickel nanotubes have been synthesized by the popular and versatile method of template-assisted electrodeposition, and a surface-directed growth mechanism based on the adsorption of the nickel–borate complex has been proposed.

Poly (3,4-(2-methylene)propylenedioxythiophene) (PMProDot) nanotubes were synthesized within the pores of polycarbonate and were further modified with styrene and vinylcarbazole by a one step electrochemical method through the methylene functional group. The enhanced electrochemical and electrochromic properties of composite nanotubes were investigated using FTIR, UV/Vis absorbance spectroscopy, and AFM.

In order to fulfil the future requirements of electrochemical energy storage, such as high energy density at high power demands, heterogeneous nanostructured materials are currently studied as promising electrode materials due to their synergic properties, which arise from integrating multi-nanocomponents, each tailored to address a different demand (e.g., high energy density, high conductivity, and excellent mechanical stability). In this article, we discuss these heterogeneous nanomaterials based on their structural complexity: zero-dimensional (0-D) (e.g. core–shell nanoparticles), one-dimensional (1-D) (e.g. coaxial nanowires), two-dimensional (2-D) (e.g.graphene based composites), three-dimensional (3-D) (e.g. mesoporous carbon based composites) and the even more complex hierarchical 3-D nanostructured networks. This review tends to focus more on ordered arrays of 1-D heterogeneous nanomaterials due to their unique merits. Examples of different types of structures are listed and their advantages and disadvantages are compared. Finally a future 3-D heterogeneous nanostructure is proposed, which may set a goal toward developing ideal nano-architectured electrodes for future electrochemical energy storage devices.

Carbon/metal oxide composites are considered promising materials for high energy density supercapacitors. So far, impregnation of the oxide into ordered mesoporous carbon materials has been demonstrated either in hard-templated carbon synthesized by using ordered mesoporous silica or alumina scaffolds, or soft-templated carbon derived from surfactant micelles. The hard-template method can provide a high pore volume but the instability of these mesostructures hinders total electrode performances upon oxide impregnation. While the soft-template methods can provide a stable mesostructure, these methods produce scaffolds with a much smaller pore volume and surface area, leading to limited metal oxide loading and electrode capacitance. Herein, anodized aluminum oxide (AAO) and triblock copolymer F127 are used together as hard and soft-templates to fabricate ordered mesoporous carbon nanowires (OMCNWs) as a host material for Fe2O3 nanoparticles. This dual-template strategy provides a high pore volume and surface area OMCNW that retains its stable structure even for high metal oxide loading amounts. Additionally, the unique nanowire morphology and mesoporous structure of the OMCNW/Fe2O3 facilitate high ionic mobility in the composite, leading to >260 F g−1 specific capacitance with good rate capability and cycling stability. This work highlights the dual-template approach as a promising strategy for the fabrication of next generation heterogeneous composites for electrochemical energy storage and conversion.

Recent advances in nanomaterials have paved the way to design innovative platforms for creating nano-barcodes for a broad range of potential applications. This feature article reviews various strategies for a dispersible array of encoded one-dimensional (1D) nano/microstructures which allow highly multiplexed analysis. 1D nano-barcodes susceptible to encoding with a number of distinct patterns are exceedingly promising for the development of much improved array systems in fields such as pharmaceutical research, disease diagnostics, and gene profiling.

A wide range of metal oxides have been studied as pseudocapitors, with the goal of achieving higher power than traditional batteries and higher energy than traditional capacitors. However, most metal oxides have relatively low conductivity, and the few exceptions, like RuO2, are prohibitively expensive. Mixed metal oxides provided an opportunity to incorporate small amounts of expensive materials to enhance the performance of a less expensive, poorer performing material. Here, by homogeneously co-depositing a small amount of energy dense and conductive RuO2 into MnO2 nanowires, we demonstrate an improvement in specific capacitance. Importantly, we also demonstrate that this improvement is not primarily provided by redox activity of RuO2, but rather by improvement of the composite conductivity. A series of RuO2–MnO2 composite nanowires with different RuO2 loading percentages have been synthesized by performing co-electrodeposition in a porous alumina template. The structure of these RuO2–MnO2 nanowires is characterized by TEM and SEM. EDS mapping shows that RuO2 is well distributed in MnO2 matrix nanowires. The chemical constituents and the phase of these composite nanowires are confirmed by X-ray photoelectron and Raman spectroscopy. The amount of RuO2 is controlled by varying the concentrations of RuCl3 and MnAc2 in the deposition solution. The precise masses of MnO2 and RuO2 are determined by ICP-AES elemental analysis. MnO2 nanowires with 6.70 wt% RuO2 demonstrate a specific capacitance of 302 F g−1 at 20 mV s−1, compared to 210 F g−1 for pristine MnO2 nanowires. Investigation of the RuO2 loading amount effect was conducted by electrochemical impedance spectroscopy (EIS) and deconvolution of capacitances, using methods previously reported by both Dunn and Transsiti. The RuO2–MnO2 nanowires studied here demonstrate a simple, straighforward method to overcome the intrinsically poor conductivity of MnO2, and clarify the source of RuO2's contribution to the improved performance.

High power electrical energy storage systems are becoming critical devices for advanced energy storage technology. This is true in part due to their high rate capabilities and moderate energy densities which allow them to capture power efficiently from evanescent, renewable energy sources. High power systems include both electrochemical capacitors and electrostatic capacitors. These devices have fast charging and discharging rates, supplying energy within seconds or less. Recent research has focused on increasing power and energy density of the devices using advanced materials and novel architectural design. An increase in understanding of structure-property relationships in nanomaterials and interfaces and the ability to control nanostructures precisely has led to an immense improvement in the performance characteristics of these devices. In this review, we discuss the recent advances for both electrochemical and electrostatic capacitors as high power electrical energy storage systems, and propose directions and challenges for the future. We asses the opportunities in nanostructure-based high power electrical energy storage devices and include electrochemical and electrostatic capacitors for their potential to open the door to a new regime of power energy.