Charging lithium ion battery cathode materials such as LiCoO2 to a higher voltage may simultaneously enhance the specific capacity and average operating voltage and thus improve the energy density. However, battery cycle life is compromised in high voltage cycling due to lattice instability and undesired oxidation of electrolyte. Cathode solid-electrolyte interphase (SEI), or cathode-electrolyte interphase (CEI), in situ formed at the cathode–electrolyte interface under high voltage, is critically important in understanding the cathode degradation process and crucial in improving high voltage cycle stability. Here we present in situ atomic force microscopy (AFM) investigation of CEI on LiCoO2 at high voltage. The formation of CEI is only observed at the LiCoO2 edge plane, not at the basal plane. The thin layer of Al2O3 coating completely suppresses the formation of CEI at the edge planes, and is shown to significantly improve coin cell high voltage cycle stability.Keywords: cathode electrolyte interphase (CEI); in situ atomic force microscopy; lithium cobalt oxide (LiCoO2); lithium ion battery; solid-electrolyte interphase (SEI);

Here, novel multifunctional electronic skins (E-skins) based on aligned few-walled carbon nanotube (AFWCNT) polymer composites with a piezoresistive functioning mechanism different from the mostly investigated theory of “tunneling current channels” in randomly dispersed CNT polymer composites are demonstrated. The high performances of as-prepared E-skins originate from the anisotropic conductivity of AFWCNT array embedded in flexible composite and the distinct variation of “tube-to-tube” interfacial resistance responsive to bending or stretching. The polymer/AFWCNT-based flexion-sensitive E-skins exhibit high precision and linearity, together with low power consumption (<10 µW) and good stability (no degradation after 15 000 bending–unbending cycles). Moreover, polymer/AFWCNT composites can also be used for the construction of tensile-sensitive E-skins, which exhibit high sensitivity toward tensile force. The polymer/AFWCNT-based E-skins show remarkable performances when applied to monitor the motions and postures of body joints (such as fingers), a capability that can find wide applications in wearable human–machine communication interfaces, portable motion detectors, and bionic robots.

•Quantification of energy band alignment of inverted structure organic solar cells.•A deconvolution protocol was established for SKPM to gauge tip transfer function.•A molecular beam epitaxy grown ideal abrupt junction was used as reference sample.Inverted structure thin-film organic solar cells (OSCs) are becoming increasingly important as they deliver higher power conversion efficiency and demonstrate better long-term stability than conventional devices. However, the energy band alignment and the built-in field across the device, which are crucial in understanding the device operation, is yet to be directly characterized. Here we present a direct visualization of the energy level alignment in operando inverted structure poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) OSCs using cross-sectional scanning Kelvin probe microscopy. The raw data of measured energy level alignment appear to be inconsistent with each other, and sometimes can even be contradictory to the device polarity observed in current density-voltage measurements. It is identified to be caused by the tip/cantilever induced convolution effect, which may severely mask abrupt energy level offsets at the thin electrode interlayers. A numerical deconvolution method is devised to quantitatively recover the energy level alignment across the device, and reveals the non-uniform electric field distribution in photoactive layer.Download high-res image (139KB)Download full-size image

Li metal has been considered as the ultimate anode material for high-density electrochemical energy storage technology because of its extremely high specific capacity (3860 mAh g−1), lowest redox potential, and ability to enable battery chemistries with lithium free cathode materials. However, the practical application of Li metal anodes is still prohibited by its low Coulombic efficiency (CE) and growth of Li dendrites during Li dissolution/deposition. Here we report the successful preparation of a lithium carbon nanotube (Li-CNT) composite via a facile and scalable molten impregnation method. When used as an anode material, the Li-CNT composite not only displays the good traits of Li metal such as high specific capacity and low lithium dissolution/deposition potential, but also shows significantly suppressed dendrite formation and high CE. When the Li-CNT composite is paired with a commercial LiFePO4 (LFP) cathode, a CE of around 90.1% can be achieved, which is much higher than the value (75.4%) obtained from a lithium foil anode.

Carbon nanotubes (CNTs) have long been regarded as an efficient free radical scavenger because of the large-conjugation system in their electronic structures. Hence, despite abundant reports on CNT reacting with incoming free radical species, current research has not seen CNT itself displaying the chemical reactivity of free radicals. Here we show that reactive free radicals can in fact be generated on carbon nanotubes via reductive defluorination of highly fluorinated single-walled carbon nanotubes (FSWNTs). This finding not only enriches the current understanding of carbon nanotube chemical reactivity but also opens up new opportunities in CNT-based material design. For example, spacer-free direct intertube cross-linking of carbon nanotubes was previously achieved only under extremely high temperature and pressure or electron/ion beam irradiation. With the free radicals on defluorinated FSWNTs, the nanotubes containing multiple radicals on the sidewall can directly cross-link with each other under ambient temperature through intertube radical recombination. It is demonstrated that carbon nanotube fibers reinforced via direct cross-linking displays much improved mechanical properties.Keywords: Carbon nanotubes; intertube cross-linking; mechanical strength; radical chemistry;

•A mild reaction was adopted to prepare MnO2-CNT with fewer defects on the CNT.•The electrode exhibited excellent rate performance at high areal density.•The electrode areal capacitance reached 1.0 F cm−2 at 0.2 A g−1 (1.28 mA cm−2).•The electrode power density: 45.2 kW kg−1, energy density: 16.7 Wh kg−1.Practical supercapacitor devices require high areal capacitance and areal power density, and thus demand high utilization of active material and good rate performance under high areal mass loading. However, ion transport in high-mass-loading electrodes can be a challenge, which leads to deteriorate specific capacitance and rate performance. In this paper, a well-dispersed porous MnO2-carbon nanotube (CNT) composite was prepared for use as a supercapacitor electrode material. The small MnO2 nanoparticles and porous CNT network facilitated fast electron/ion transfer kinetics in the electrode. With a mass loading as high as 6.4 mg cm−2 on the electrode, the MnO2-CNT composite exhibited an excellent areal capacitance of 1.0 F cm−2 at 0.2 A g−1 (1.28 mA cm−2), with a retention of 77% even at a high current density of 20 A g−1 (128 mA cm−2). The electrode exhibited a high power density of 45.2 kW kg−1 (0.29 W cm−2) while maintaining a reasonable energy density of 16.7 Wh kg−1 (106 μWh cm−2). No apparent fading was observed even after 3000 charge/discharge cycles at 1 A g−1. This porous and evenly distributed MnO2-CNT composite has great potential for practical applications in supercapacitors.

Single-walled carbon nanotubes (SWNTs) are post-treated by argon (Ar) or ammonia (NH3) plasma irradiation to introduce defects that are potentially related to catalysis towards the oxygen reduction reaction (ORR). Electrochemical characterization in alkali medium suggests that the plasma irradiated SWNTs demonstrate enhanced catalytic activity toward the ORR with a positively shifted threshold potential. Moreover the enhanced desired four-electron pathway catalytic activity, which exhibited as the positive shifted threshold potential, is independent of the nitrogen dopant. The nature of the defects is probed with Raman and X-ray photoelectron spectroscopy. The results indicate that the non-nitrogen doped defects of SWNTs contribute to the actual active site for the ORR.

•In-situ electrochemical activated radical polymer was used as a multifunctional additive for Li-S batteries.•The additive not only displays strong binding affinity to polysulfides but also improves the kinetics of the cathode reaction.•Significant increase in specific discharge capacity and cycling stability.While Li–S batteries are poised to be the next generation high-density energy storage devices, the low sulfur utilization and intrinsic polysulfide shuttle have limited their practical applications. Here, we report that radical polymer Poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA)—a stable free radical polymer reported to be potential organic electrode materials–can perform as a multifunctional sulfur-trapping and catalytic binder for high performance Li-S batteries once activated via in-situ electrochemical oxidation. The activated PTMA+ not only displays strong binding affinity to polysulfides but also provides PTMA+-assisted additional redox sites and improves the kinetics of the cathode reaction. Thus the novel multifunctional additive for Li-S batteries results in improved cycle life, faster rate performance and most importantly, a significantly increase in specific discharge capacity by ~80%, with specific capacity of 1254 mAh/g and Coulombic efficiency of 96% at a four-hour charge/discharge (C/4) current rate.

Nanomaterials are increasingly used in electronic, optoelectronic, bioelectronic, sensing, and energy nanodevices. Characterization of electrical properties at nanometer scales thus becomes not only a pursuit in basic science but also of widespread practical need. The conventional field-effect transistor (FET) approach involves making electrical contacts to individual nanomaterials. This approach faces serious challenges in routine characterization due to the small size and the intrinsic heterogeneity of nanomaterials, as well as the difficulties in forming Ohmic contact with nanomaterials. Since the charge carrier polarization in semiconducting and metallic materials dominates their dielectric response to external fields, detecting dielectric polarization is an alternative approach in probing the carrier properties and electrical conductivity in nanomaterials.This Account reviews the challenges in the electrical conductivity characterization of nanomaterials and demonstrates that dielectric force microscopy (DFM) is a powerful tool to address the challenges. DFM measures the dielectric polarization via its force interaction with charges on the DFM tip and thus eliminates the need to make electrical contacts with nanomaterials. Furthermore, DFM imaging provides nanometer-scaled spatial resolution.Single-walled carbon nanotubes (SWNTs) and ZnO nanowires are used as model systems. The transverse dielectric permittivity of SWNTs is quantitatively measured to be ∼10, and the differences in longitudinal dielectric polarization are exploited to distinguish metallic SWNTs from semiconducting SWNTs. By application of a gate voltage at the DFM tip, the local carrier concentration underneath the tip can be accumulated or depleted, depending on charge carrier type and the density of states near the Fermi level. This effect is exploited to identify the conductivity type and carrier type in nanomaterials.By making comparison between DFM and FET measurements on the exact same SWNTs, it is found that the DFM gate modulation ratio, which is the ratio of DFM signal strengths at different gate voltage, is linearly proportional to the logarithm of FET device on/off ratio. A Drude-level model is established to explain the semilogarithmic correlation between DFM gate modulation ration and FET device on/off ratio and simulate the dependence of DFM force on charge carrier concentration and mobility. Future developments towards DFM imaging of charge carrier concentration or mobility in nanomaterials and nanodevices can thus be expected.

While Li–S batteries are poised to be the next generation high-density energy storage devices, low sulfur utilization and slow rate performance have limited their practical applications. Here, we report the synthesis of monodispersed S8 nanoparticles (NPs) with different diameter and the nanosize dependent kinetic characteristics of the corresponding Li–S batteries. Most remarkably, 5 nm S NPs display the theoretical discharging/charging capacity of 1672 mAh g–1 at 0.1 C rate and a discharge capacity of 1089 mAh g–1 at 4 C.

Practical applications of Li–S batteries require not only high specific capacities and long cycle lifetimes but also high rate performance. We report a rationally designed Li–S cathode, which consists of a freestanding composite thin film assembled from S nanoparticles, reduced graphene oxide (rGO), and a multifunctional additive poly(anthraquinonyl sulfide) (PAQS). The S nanoparticles provide a high initial specific capacity, and the layered and porous rGO structure provides electron and ion transport paths and restricts polysulfide shuttling. PAQS is not only a highly efficient sulfide trapping agent but also an excellent Li+ conductor, which benefits the battery reaction kinetics at a high rate. The resulting cathode exhibits an initial specific capacity of 1255 mAh g–1 with a decay rate as low as 0.046% per cycles over 1200 cycles. Importantly, it displays a reversible capacity of 615 mAh g–1 when discharged at a high rate of 8 C (13.744 A g–1).

Sulfurized carbon is a promising candidate for cathode materials in practical lithium–sulfur batteries due to its high and stable capacity retention, extremely low self-discharge, and excellent safety. The main disadvantage is the relatively low sulfur content in sulfurized carbon materials. Borrowing the idea from rubber crosslinking chemistry, here we report the use of a vulcanization accelerator in carbon sulfurization. Vulcanization accelerators significantly improve sulfur content by ∼8 wt%, which results in a remarkable increase in the discharge capacity of corresponding Li–S batteries by ∼120 mA h g−1 while maintaining the outstanding cycling stability and low self-discharge. The effectiveness of this approach and the wide variety of vulcanization accelerator chemistry will pave the way for sulfurized carbon materials towards practical applications in Li–S batteries.

A high rate capability is a primary requirement for an electric double-layer capacitor (EDLC) in practical applications, which is mainly governed by the ionic diffusion rate. Construction of the electrode structure with proper paths for the rapid transport of ions is an efficient method to facilitate the diffusion of ions in the electrode. In this study, we prepared multi-walled carbon nanotube microspheres (MWNTMS) with a stable porous structure via the spray drying method. The MWNTMS act as a local electrolyte micro-reservoir and provide stable ion transport paths in the EDLC electrode, which will facilitate the access of the electrode to the electrolyte and accelerate the diffusion rate of the ions. Using only MWNTMS as active materials, an areal capacitance of 105 mF/cm2 at 30 A/g is observed at an areal density of 7.2 mg/cm2. When the MWNTMS are combined with reduced graphene oxides (rGO) to form an rGO-MWNTMS hybrid electrode with an areal density of 3.0 mg/cm2, a high areal capacitance of 136 mF/cm2 at 100 A/g is observed. This rGO-MWNTMS-based EDLC presents a high areal power density of 1540 mW/cm2. These favorable results indicate that MWNTMS are promising materials for applications in high power supercapacitors.

•PSS-free Ag-grid/VPP-PEDOT electrode shows high transmittance and conductivity.•Efficiency of 1.2 cm2 flexible organic solar cells with this electrode reaches 2.6%.•10 times better stability is obtained in comparison with that of Ag-grid/PH1000 cells.The presence of PSS in solution processed high conducting polymer PEDOT:PSS (PH1000) limits the reliability and lifetime of organic photovoltaic devices due to its acidic and hygroscopic nature. We have developed an alternative PSS-free transparent electrode, based on vapor-phase polymerized (VPP) PEDOT in combination with a current collecting silver grid. The hybrid electrode exhibits a low sheet resistance of 1.6 Ω/□ with an excellent bending proof performance. The power conversion efficiency (PCE) is 2.63% in a 1.21 cm2 area device with a stacking structure of PET/Ag-grid/VPP-PEDOT/ZnO/poly[(9,9-bis(3-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN)/poly(3-hexylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester (P3HT:PC61BM)/MoO3/Al. This efficiency is lower than, but comparable to the PCE (3.36%) of a control device with similar structure PET/Ag-grid/PH1000/ZnO/PFN/P3HT:PC61BM/MoO3/Al. A striking advantage using VPP-PEDOT to replace PH1000 is the high ambient stability of the device. The PCE of un-encapsulated devices after 120 h continuous exposure to ambient oxygen and moisture is retained at a 75% level of its initial value. These results suggest that the Ag grid/VPP-PEDOT is a promising alternative to ITO or high conducting PEDOT:PSS for realization of high efficiency, low cost and stable organic solar cells (OSCs).

We report a sulfur–amine chemistry-based method to prepare multi-walled carbon nanotube–sulfur (MWNT–S) composites in a highly efficient and quantitative manner. The resulting MWNT–S composites exhibit excellent cycling stability at up to 400 cycles, with high sulfur loading. Developing this method also increases the number of research routes that could be pursued with respect to Li–S batteries.

Culture conditions including pH, nutrient concentration and temperature strongly influence the properties of a microbial strain by affecting many factors such as the microbial membrane and metabolism. We present a microfluidic chip for screening pH and nutrient content with a concentration gradient generator connected to eight parallel suspension culture loops and another chip for the screening of temperature with four different temperature zones under suspension culture loops. Bacteria grow much faster on chips than in test tubes, and yet interestingly, on-chip screening of culture conditions for E. coli yields results similar to those from a culture in test tubes, demonstrating the validity of the on-chip screening approach. The microfluidic chips were applied to study the growth conditions of two wild type Bacillus subtilis strains isolated from polluted water. The on-chip screening experiments show advantages of nanoliter scale screening units, high-throughput and requiring only one-fourth of the time.

The solid electrolyte interphase (SEI) that forms on electrodes largely defines the performances of lithium ion batteries (LIBs), such as cycling performance, shelf life, and safety. Additives in the electrolyte can modify the properties of the SEI and thus efficiently improve the performances of LIBs. However, the effects of additives on the mechanical properties, structure, and stability of the SEI have rarely been studied directly. In this paper, we report the influence of vinylene carbonate (VC) and lithium bis(oxalate)borate (LiBOB) additives on the mechanical properties of SEI films formed on MnO electrodes using atomic force microscopy (AFM) and force spectroscopy. The results show that the SEI formed from VC additive is thick and soft and partially decomposes upon charging. LiBOB forms thin, stiff, and electrochemically stable SEI films, but the stiff SEI may not be favorable for adapting the volume change of the electrodes. The VC and LiBOB mixed additive combines the advantages of the two components and produces stable SEI with moderate thickness and stiffness. This work also demonstrates that the AFM–force spectroscopy method is effective in investigating the structure and mechanical properties of SEI films.

The adsorption of O2/H2O molecules on the ZnO nanowire (NW) surface results in the long lifetime of photo-generated carriers and thus benefits ZnO NW-based ultraviolet photodetectors by suppressing the dark current and improving the photocurrent gain, but the slow adsorption process also leads to slow detector response time. Here we show that a thermally evaporated copper phthalocyanine film is effective in passivating surface trap states of ZnO NWs. As a result, the organic/inorganic hybrid photodetector devices exhibit simultaneously improved photosensitivity and response time. This work suggests that it could be an effective way in interfacial passivation using organic/inorganic hybrid structures.

Si/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanowire arrays have been prepared by chemical etching of Si nanowires followed by vapor-phase polymerization of PEDOT as hybrid photoanodes for photoelectrochemical water-splitting. The PEDOT layer is employed as a multi-functional coating to prevent photocorrosion of Si nanowires, collect photogenerated holes and catalyze the water oxidation reaction. The amino silane modified Si nanowire surface improves PEDOT layer adhesion, and the resulting photoanode exhibits better photoresponse and improved stability. By tuning the length of the nanowires, we identify that the competition between the carrier recombination and catalytic water oxidation reaction is the primary factor determining the photoelectrocatalytic activity of the hybrid photoanode.

AbstractAn ITO-free transparent hybrid electrode based on an embedded high resolution current collecting silver grid (Ag-grid) in combination with solution processed high conductive PEDOT:PSS (PH1000) has been demonstrated for applications in organic photovoltaic cells. The high resolution embedded Ag-grid lends low shadow loss and gives rise to current collecting layers with good electrical conductivity. Sheet resistance of the hybrid electrode combining the high-resolution Ag-grid and the PH1000 reaches several Ohms per square. Solution-processed large area flexible polymer bulk-heterojunction (BHJ) photovoltaic cells are prepared from the Ag-grid/PH1000 hybrid electrode with a configuration of hybrid electrode/PEDOT:PSS-4083/P3HT:PCBB-C8/LiF/Al. A self-assembling fullerene derivative (PCBB-C8) is chosen as the acceptor, which induces the P3HT to form ordered active layer and hence avoids the annealing process on flexible PET substrates. Power conversion efficiency (PCE) of the resulting devices reaches 1.36%.Graphical abstractThe high resolution embedded Ag-grid lends low shadow loss and gives rise to current collecting layers with good electrical conductivity. An ITO-free transparent hybrid electrode based on the silver grid (Ag-grid) in combination with solution processed high conductive PEDOT:PSS (PH1000) has been demonstrated for applications in large area flexible organic photovoltaic cells. Highlights► High resolution Ag-grid with ultra low sheet resistance was prepared. ► The Ag-grid was exploited for application as the hybrid electrode in flexible OPV. ► The PCE of the ITO-free flexible large-area OPV reached 1.36%.

•The conductivity of VPP PEDOT films is critically dependent on temperature.•Synchrotron GAXRD shows [1 0 0] inter-chain stacking determines film conductivity.•Temperature has a significant effect on VPP film growth rate.The structure and properties of PEDOT films prepared under different vapor-phase polymerization (VPP) temperatures were characterized by grazing angle X-ray diffraction, Raman spectroscopy, UV/vis absorption, atomic force microscopy, scanning electron microscopy and electrical conductivity measurements. The VPP temperature plays key roles on the polymerization reaction rate and the mobility of the polymer chains as well as the volatilization of the reactant and product, which result in drastically different properties of the VPP PEDOT films. In the range of 33–57 °C, the lattice structure and the morphology of the films can be significantly affected by the VPP temperature. The optimum temperature (46 ± 1 °C) resulted in PEDOT film with the highest conductivity on glass substrate (622 S/cm), which is ascribed to highly ordered crystal structure and smooth morphology. After polymerization, the topography, efficiency of current transport and crystal structure of the PEDOT film in response to temperature were in situ monitored by means of conductive AFM and grazing XRD. For PEDOT films with a high level of conjugation, the film conductivity is mainly determined by the crystal structure of the film. The lamella inter-chain stacking order in [1 0 0] direction deeply influences the film conductivity, while the π–π stacking order in [0 1 0] direction has no apparent relation with the film conductivity. The film with highly ordered structure in [1 0 0] direction tends to have good film conductivity.

Solid electrolyte interphase (SEI) is an in situ formed thin coating on lithium ion battery (LIB) electrodes. The mechanical property of SEI largely defines the cycling performance and the safety of LIBs but has been rarely investigated. Here, we report quantitatively the Young’s modulus of SEI films on MnO anodes. The inhomogeneity of SEI film in morphology, structure, and mechanical properties provides new insights to the evolution of SEI on electrodes. Furthermore, the quantitative methodology established in this study opens a new approach to direct investigation of SEI properties in various electrode materials systems.

The electronic properties of single-walled carbon nanotubes (SWNTs) are sensitive to the gas molecules adsorbed on nanotube sidewalls. It is imperative to investigate the interaction between SWNTs and gas molecules in order to understand the mechanism of SWNT-based gas-sensing devices or the stability of individual SWNT-based field effect transistors (FETs). To avoid the Schottky barrier at the metal/SWNT contact, which dominates the performance of SWNT-based FETs, we utilize a contactless technique, dielectric force microscopy (DFM), to study the intrinsic interaction between SWNTs and gaseous ammonia molecules. Results show that gaseous ammonia affects the conductivity of semiconducting SWNTs but not metallic SWNTs. Semiconducting SWNTs, which are p-type doped in air, show suppressed hole concentration in ammonia gas and are even inverted to n-type doping in some cases.Keywords: chemical sensing; dielectric force microscopy (DFM); electrostatic force microscopy (EFM); single-walled carbon nanotube (SWNT);

Characterization of electronic properties of nanomaterials usually involves fabricating field effect transistors and deriving materials properties from device performance measurements. The difficulty in fabricating electrical contacts to extremely small-sized nanomaterials as well as the intrinsic heterogeneity of nanomaterials makes it a challenging task to measure the electronic properties of large numbers of individual nanomaterials. Here, we utilize a scanning probe technique, the dielectric force microscopy (DFM) to address the challenges. The DFM technique measures the low frequency dielectric response of nanomaterials, which is intrinsically related to their electrical conductivity. The incorporation of a gate bias voltage in DFM measurements allows for charge carrier density modulation, which is exploited to determine the carrier type in nanomaterials such as semiconducting single-walled carbon nanotubes (SWNTs) and ZnO nanowires (ZnO NWs). This technique avoids the need of electrical contacts and inherits the spatial mapping capability of scanning probe microscopy, as manifested in the imaging of intratube metallic/semiconducting junctions in SWNTs. We expect the DFM technique to find broad applications in the characterization of various nanoelectonic materials and nanodevices.

A solution filling and drying method has been demonstrated to fabricate Si/PEDOT:PSS core/shell nanowire arrays for hybrid solar cells. The hybrid core/shell nanowire arrays show excellent broadband anti-reflection, and resulting hybrid solar cells absorb about 88% of AM 1.5G photons in the 300–1100 nm range. The power conversion efficiency (PCE) of the hybrid solar cell reaches 6.35%, and is primarily limited by direct and indirect interfacial recombination of charge carriers.

Large-scale transparent and flexible electronic devices have been pursued for potential applications such as those in touch sensors and display technologies. These applications require that the power source of these devices must also comply with transparent and flexible features. Here we present transparent and flexible supercapacitors assembled from polyaniline (PANI)/single-walled carbon nanotube (SWNT) composite thin film electrodes. The ultrathin, optically homogeneous and transparent, electrically conducting films of the PANI/SWNT composite show a large specific capacitance due to combined double-layer capacitance and pseudo-capacitance mechanisms. A supercapacitor assembled using electrodes with a SWNT density of 10.0 µg cm−2 and 59 wt% PANI gives a specific capacitance of 55.0 F g−1 at a current density of 2.6 A g−1, showing its possibility for transparent and flexible energy storage.

Microfluidic systems could, in principle, enable high-throughput breeding and screening of microbial strains for industrial applications, but parallel and scalable culture and detection chips are needed before complete microbial selection systems can be integrated and tested. Here we demonstrate a scalable multi-channel chip that is capable of bacterial suspension culture. The key invention is a multi-layered chip design, which enables a single set of control channels to function as serial peristaltic pumps to drive parallel culture chamber loops. Such design leads to scalability of the culture chip. We demonstrate that E. coligrowth in the chip is equivalent or superior to conventional suspension culture on shaking beds. The chip could also be used for suspension culture of other microbes such as Bacillus subtilis, Pseudomonas stutzeri, and Zymomonas mobilis, indicating its general applicability for bacterial suspension culture.

Glucose oxidase (GOx) is widely used in the glucose biosensor industry. However, mediatorless direct electron transfer (DET) from GOx to electrode surfaces is very slow. Recently, mediatorless DET has been reported via the incorporation of nanomaterials such as carbon nanotubes and nanoparticles in the modification of electrodes. Here we report GOx electrodes showing DET without the need for any nanomaterials. The enzyme after immobilization with poly-l-lysine (PLL) and Nafion® retains the biocatalytic activities and oxidizes glucose efficiently. The amperometric response of Nafion–PLL–GOx modified electrode is linearly proportional to the concentration of glucose up to 10 mM with a sensitivity of 0.75 μA/mM at a low detection potential (−0.460 V vs. Ag/AgCl). The methodology developed in this study will have impact on glucose biosensors and biofuel cells and may potentially simplify enzyme immobilization in other biosensing systems.

Sulfurized carbon is a promising candidate for cathode materials in practical lithium–sulfur batteries due to its high and stable capacity retention, extremely low self-discharge, and excellent safety. The main disadvantage is the relatively low sulfur content in sulfurized carbon materials. Borrowing the idea from rubber crosslinking chemistry, here we report the use of a vulcanization accelerator in carbon sulfurization. Vulcanization accelerators significantly improve sulfur content by ∼8 wt%, which results in a remarkable increase in the discharge capacity of corresponding Li–S batteries by ∼120 mA h g−1 while maintaining the outstanding cycling stability and low self-discharge. The effectiveness of this approach and the wide variety of vulcanization accelerator chemistry will pave the way for sulfurized carbon materials towards practical applications in Li–S batteries.

We report a sulfur–amine chemistry-based method to prepare multi-walled carbon nanotube–sulfur (MWNT–S) composites in a highly efficient and quantitative manner. The resulting MWNT–S composites exhibit excellent cycling stability at up to 400 cycles, with high sulfur loading. Developing this method also increases the number of research routes that could be pursued with respect to Li–S batteries.