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The structural battery is a multifunctional energy storage device that aims to address the weight and volume efficiency issues that conventional batteries face, especially in electric transportation. By combining the functions of mechanical load bearing and energy storage, structural batteries can reduce the reliance on, or even eventually replace the main power source in an electric vehicle or a drone. However, one of the key challenges to be addressed before achieving multifunctionality in structural batteries would be the design of a suitable multifunctional structural battery electrolyte. The structural battery electrolyte is the constituent that provides mechanical integrity under flexural loads or impact and hence determines the electrochemical and much of the mechanical performance of a structural battery device. This concept paper aims to cover the key considerations and challenges facing the design of structural battery electrolytes. In addition, the main approaches to surmount these challenges are highlighted, keeping design aspects like sustainability and recyclability in view. The authors would like to acknowledge the Structural Power for portable and electrified transportation grant (Grant number A20H3b0140, AME programmatic) for the support of this work.

ZIF-67 comprises alternately arranged cobalt atoms and nitrogen-rich organic linkers, making it an ideal single source precursor to producing Co and N co-doped carbon (C-ZIF-67) catalyst for oxygen reduction reaction (ORR). C-ZIF-67 particle catalyst in air-cathode, however, often shows limited activity and stability because of the particle-to-particle resistances and particle detachment issues. Herein, we introduce an in-situ approach to selectively growing ZIF-67 on electrospun polyacrylonitrile (PAN) fibers, forming an interesting “gems-on-string” structured PAN@ZIF-67 hybrid. Upon pyrolysis the hybrid is converted to conductive C-PAN@ZIF-67 with well-retained hierarchical structure, showing high ORR activity with excellent durability in alkaline electrolyte. A zinc-air battery (ZnAB) using C-PAN@ZIF-67 in air-cathode delivers a stable discharge voltage of 1.24 V at a high current density of 20 mA cm−2. With the regeneration of the cell after its full-discharges by mechanically replenishing the zinc anode and the electrolyte, a continuous operation over 38 days is demonstrated with the discharge voltage above 1.0 V at a current density of 10 mA cm−2. Significantly, a freestanding C-PAN@ZIF-67 mat serves directly as the flexible cathode for thin and bendable ZnABs to deliver high discharge voltages in both flat and bent states, promising great potential for future wearable electronics.

Electrification is seen as one of the key strategies to mitigate the growing energy demands in areas like transportation. With electrification, a better and safer energy storage system becomes a pressing need. Therefore, Li-based batteries are gaining popularity due to their high theoretical capacities. However, the use of Li-based batteries had been fraught with safety concerns. Specifically, Li dendrite formation during Li-plating can cause shorting in cells and thermal runaway. To that end, much effort has been put into mitigating the growth of these dendrites. To tackle this issue, the mechanisms involved in the formation of different morphologies of the plated Li is highlighted, as it determines, to a large extent, the mechanical properties of the plated Li. In turn, the mechanical properties of the plated Li will affect the cyclability and the overall safety of the battery. However, the yield strength of most materials used in separators and solid electrolytes are usually not high enough to prevent penetration by Li dendrites. Hence, various strategies to control the growth and morphology of Li deposits that can form dendrites, has been highlighted here as these strategies are key research directions for the advancement of high energy density Li-based batteries.

Gel polymer electrolytes are an important advancement in energy storage technology due to their enhanced safety and practical ionic conductivities at ambient temperatures. Herein, a simple one-step facile synthesis of chemically crosslinked polyurethanes containing polyethylene oxide (PEO) and polypropylene oxide (PPO) macromolecular segments was developed, using ubiquitous non-toxic tetrabutylammonium or potassium chloride and bromide salts as catalysts. These salts were shown to catalyze the gelation of diol-diisocyanate polyaddition reactions within minutes. When impregnated with a liquid electrolyte, the resulting gel electrolyte exhibited a practical ionic conductivity of 1.1×10-4 S cm-1 at 40 °C and low segmental chain motion activation energy (11 kJ mol-1 ). These findings further promote PEO-PPO polyurethanes as a biocompatible class of materials suitable for further exploration as gel polymer electrolytes for supercapacitors.

The energy density of lithium ion batteries heavily relies on the loading of electrochemically active materials in their cathode. LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) as a promising high-energy cathode material has a practical specific capacity of about 200 mAh g −1 which, however, is often compromised by the additives in the electrode, such as the conductive carbon and binder. To harvest a higher energy density NCA electrode, cyclic voltammetry and galvanostatic intermittent titration techniques are employed herein to evaluate the apparent chemical diffusion coefficient of Li + and maximize the loading of NCA. Our results show that the carbon content can be reduced to 0.2 wt% (with 97.8 wt% of NCA), making a high-energy cathode for Li-ion batteries. This protocol would also set a precedent for the energy density optimization of other cathodes.

The storage modulus and ionic conductivity of prototypical gel electrolytes consisting of different amounts of poly (vinyl alcohol) and the ionic liquid 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMI TFSI) were made and characterized. Peak ionic conductivity and room temperature storage modulus of 2.4 × 10−2 S cm−1 and 128 MPa respectively were achieved. The gel electrolytes were also characterized with a multifunctional index. It was found that the optimal ionic conductivity and mechanical properties were obtained with 40 wt% EMI TFSI loading, where an ionic conductivity of 1.2 × 10−3 S cm−1 and a room temperature storage modulus of 30.7 MPa were obtained. A specific capacitance of 29.24 F g−1 was obtained in a test supercapacitor device.

© 2016 Elsevier LtdThe Electrophoretic Deposition (EPD) of graphene-related materials (GRMs) is an attractive strategy for a wide range of applications. This review paper provides an overview of the fundamentals and specific technical aspects of this approach, highlighting its advantages and limitations, in particular considering the issues that arise specifically from the behaviour and dimensionality of GRMs. Since obtaining a stable dispersion of charged particles is a pre-requisite for successful EPD, the strategies for suspending GRMs in different media are discussed, along with the resulting influence on the deposited film. Most importantly, the kinetics involved in the EPD of GRMs and the factors that cause deviation from linearity in Hamakers Law are reviewed. Side reactions often influence both the efficiency of deposition and the nature of the deposited material; examples include the reduction of graphene oxide (GO) and related materials, as well as the decomposition of the suspension medium at high potentials. The microstructural characteristics of GRM deposits, including their degree of reduction and orientation, strongly influence their performance in their intended function. These factors will also determine, to a large extent, the commercial potential of this technique for applications involving GRMs, and are therefore discussed here.

This work describes a novel supercapacitor electrode based on a glass fiber felt substrate, single-walled carbon nanotube (SWCNT) and metal oxide layers (RuO2 or MnO2). It is fabricated by the repeated and alternate deposition of SWCNTs and metal oxides via dipping and electrodeposition, respectively, to achieve three-dimensional layered hierarchical structured supercapacitor electrodes. The results show that the layered structured electrodes fabricated by alternating deposition of SWCNTs and metal oxides have higher capacitance as compared with the bulk deposited samples, which are fabricated by deposition of SWCNTs followed by metal oxides. The best configuration studied in this work shows specific capacitance of 72 and 98 F/g for the SWCNT–MnO2 and SWCNT–RuO2, respectively, whereas the corresponding areal capacitances are 0.07 and 0.09 F/cm2. This three-dimensional porous electrode structure design combines the high mechanical stability of the felt substrate with the high conductivity and specific surface area of SWCNTs, and the high capacitance of metal oxides. This will add immensely to the research and development of wearable lightweight electronics in harsh environments.

Graphene Oxide (GO) is analogous to graphene with oxygen moieties. It offers several advantages over graphene, such as a tunable band-gap, facile synthesis and no use of metal catalysts. Due to the monolayer configuration of GO, all of its carbon atoms are readily exposed to the atmosphere and are sensitive to surface perturbations, thus making GO very suitable for liquid-gated field effect transistor (FET) type sensing applications. However, there are two main limitations preventing GO usage in practical FET sensors. It displays (1) variable coverage between fabricated chips and (2) high electrical resistance. In this paper, we overcome these two limitations by using a facile atmospheric-pressure ethanol Chemical Vapor Deposition treatment on top of pre-coated GO (ECVDGO) which decreases the electrical resistivity from 1.99 × 106 Ω square−1 to 4.68 × 103 Ω square−1, and resistivity variation from 1.60 × 106 to 7.72 × 102 Ω square−1; whilst enlarging the surface GO coverage up to 100%. We then demonstrate the ability of the post-treated ECVDGO liquid-gated FET transducer to detect Interleukin-6 which is a multi-functional cytokine involved in regulating the immune function and the acute phase response. The sensing window of the fabricated biosensor to Interleukin-6 is within the physiologically-relevant range, from 4.7 to 300 pg ml−1. The LOD of the sensor based on 3σ is 2.9 pA or 1.53 pg ml−1. This study demonstrates the emerging potential of GO with high manufacturability in liquid-gated FET biosensors for sensitive and label-free detection of bio-molecules.

Interleukin-6 (IL-6) is a pleiotropic cytokine with an important role in both immune regulation and exercise metabolism. During exercise, IL-6 is predominantly produced within, and released from, the working skeletal muscle, with the magnitude of IL-6 release related to the duration and intensity of the exercise bout. IL-6 (a) is the first cytokine to appear in circulation following initiation of exercise and (b) undergoes the most pronounced increase as compared to any cytokine in response to exercise. In the last decade, studies have suggested a role for IL-6 as a muscle energy sensor, pointing to its potential role as a biomarker of overtraining. Currently, ELISA and western blot is the staple detection technique for IL-6. However, they require substantial time, cost, machinery and specialist training. On the other hand, a Graphene Oxide-based amperometric sensor can provide real-time, low-cost yet sensitive protein detection. But, the coverage of mono-layered Graphene Oxide (GO) flake on SiO2 substrate is limited due to rinsing and unwanted crosslinking of the 3-AminoPropylTriEthoxy Silane (APTES) adhesion layer, thus leading to low available GO surface area, high variability of electrical conductivity between chips and low sheet transconductance that limits sensitivity of the sensor. This work had overcome this limitation by depositing carbon on the edges of GO flakes using an ethanol chemical vapor deposition (CVD). Then, the post-treated GO is fabricated into a liquid-gated biosensor and the detection window for IL-6 is presented. Our work yielded a highly conductive and electrically homogeneous carbon-based transducer to enable low-cost, facile, real-time yet sensitive amperometric sensors for IL-6. © 2013 Published by Elsevier Ltd. Selection and peer-review under responsibility of RMIT University Interleukin-6, Reduced Graphene Oxide Growth, Chemical Vapor Deposition, Biosensor, Liquid-gated Field Effect Transistor

A novel horizontally aligned single-walled carbon nanotube (CNT) Field Effect Transistor (FET)-based biosensing platform for real-time and sensitive protein detections is proposed. Aligned nanotubes were synthesized on quartz substrate using catalyst contact stamping, surface-guided morphological growth and chemical vapor deposition gas-guided growth methods. Real-time detection of prostate-specific antigen (PSA) using as-prepared FET biosensors was demonstrated. The kinetic measurements of the biosensor revealed that the drain current (Id) decreased exponentially as the concentration of PSA increased, indicating that the proposed FET sensor is capable of quantitative protein detection within a detection window of up to 1 µM. The limit of detection (LOD) achieved by the proposed platform was demonstrated to be 84 pM, which is lower than the clinically relevant level (133 pM) of PSA in blood. Additionally, the reported aligned CNT biosensor is a uniform sensing platform that could be extended to real-time detections of various biomarkers.

Reduced graphene oxide (RGO) has many advantages over graphene such as low-cost, aqueous processable and industrial-scalable. However, two main limitations that prevent the use of RGO in electronics are the high electrical resistance and large electrical resistance deviation between fabricated devices. This limits RGO's use in biosensors, capacitors and other electronic devices. Herein, we present (1) a modified Hummer's method to obtain large RGO flakes via in-situ size fractionation and (2) the novel growth of RGO which can bridge the gaps in-between existing RGO flakes. Together, these two processes reduced the electrical resistance drastically from 1.99E + 06 to 4.68E + 03 Ω/square and the standard deviation decreased from 80.5 % to 16.5 %. The RGO was then fabricated into a field-effect transistor biosensor. A 1 pmol to 100 nmol change in Cytochrome C protein corresponded to a 3 % change in electrical resistance. The reported improved RGO synthesis method and subsequent growth enable large-scale application of RGO in practical electronic devices such as biosensors.

Carbon foams were produced from a macroporous poly(divinylbenzene) (poly(DVB) precursor, synthesized by polymerizing the continuous but minority phase of water-in-oil high internal phase emulsions (HIPEs) stabilized by molecular and/or particulate emulsifiers. Both permeable and non-permeable hierarchically porous carbon foams, or ‘carboHIPEs’, were prepared by carbonization of the resulting macroporous polymers at 800 °C. The carbon yields were as high as 26 wt.% of the original polymer. CarboHIPEs retain the pore structure of the macroporous polymer precursor, but with surface areas of up to 505 m2/g and excellent electrical conductivities of 81 S/m. Contrary to some previous reports, the method does not require further modification, such as sulfonation or additional crosslinking of the polyHIPE prior to carbonization, due to the inherently crosslinked structure of poly(DVB). The use of a pourable, aqueous emulsion-template enables simple moulding, minimises waste and avoids the strong acid treatments used to remove many conventional solid-templates. The retention of the macroporous structure is coupled with the introduction of micropores during carbonization, producing hierarchically porous carboHIPEs, suitable for a wide range of applications as sorbents and electrodes.

Carbon nanotubes (CNTs) are one of the advanced functional materials of today and has been researched extensively since its discovery. Although much is still not known about the physical and chemical properties of CNTs, it has already found potential applications in many industries, from defense to electronics and even in environmental remediation. CNTs possess many desirable mechanical and chemical properties, which supercedes many of the advanced materials of today. It was also found that CNTs have excellent electronic properties like unprecedented mobilities of up to 100,000 cm 2 /V s, which can potentially result in a quantum leap in the electronics industry. Over the recent years, CNT and their derivatives (decorated/functionalized) were also intensively studied, especially in the field of bio and chemical sensing owing to the size similarity of nanotubes with the analytes such as biospecies that enable strong interactions between them. However, despite intensive research, commercialization of these potential applications still remains elusive mainly due to the lack of control in synthesis of specific chirality, diameter and length of CNTs, which influences the device performance. This short review focuses on addressing recent advances in CNT research especially on aspects such as controlled synthesis, decoration/functionalization for specific recognition, sensor device fabrication and commercialization strategies.

This paper reports a selective method of sensing hydrogen sulphide in gaseous state using silver nanoparticle decorated single-walled carbon nanotubes (SWCNT) at room temperature. The transduction platform is a simple resistor which was constructed by drop-casting of a random network of silver nanoparticle decorated carbon nanotubes onto a channel joining two electrodes. This study shows the differential sensing of hydrogen sulphide with respect to interfering analytes such as carbon monoxide and nitric oxide, displaying the different mechanisms involved in the sensing of the gases. These results indicate the possibility of fabricating simple devices with low power consumption based on flexible plastic substrate for selective sensing of gaseous molecules at room temperature by appropriately functionalizing the carbon nanotubes (CNTs). Accepted version

Reduced graphene oxide (RGO) has the advantage of an aqueous and industrial-scalable production route. However, one of the main limitations that prevent the use of RGO in electronics is the high electrical resistance deviation between fabricated chips. In this article, we present the novel growth of RGO which can bridge the gaps in-between existing flakes and thus reduce the electrical resistance standard deviation from 80.5 % to 16.5 %. The average resistivity of the treated RGO of ∼ 3.8 nm thickness was 200 Ω/square. The study uses an atmospheric-pressure chemical vapour deposition (CVD) system with hydrogen and argon gas bubbling through ethanol before entering the furnace. With a treatment of 2 hours, 100 % of the silicon dioxide substrate was covered with RGO from an initial 65 % coverage. This technology could enable large-scale application of RGO use in practical electronic devices.

A facile route for sensitive label-free detection of bio-toxins using aligned single walled carbon nanotubes is described. This approach involves patterning of a catalyst on the surface of a quartz substrate using a sub-100 μm stripe-patterned polydimethylsiloxane stamp for aligned carbon nanotube generation followed by fabrication of field effect transistor (FET). Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy are employed to characterize the synthesized nanotubes. Unlike previous reports, the adopted approach enables direct electronic detection of bio-toxins with sensitivities comparable to ELISA. As a proof of concept, the fabricated FET responds to nM concentration levels (with a LOD of ∼2 nM) of epsilon toxin produced by Clostridium perfringens and a prominent food toxin. This facile approach could be customized to detect other classes of toxins and biomarkers upon appropriate functionalization of the aligned carbon nanotubes. Finally, we demonstrate the use of the FET-platform for detection of toxin in more complex matrices such as orange juice.

Single- and multilayer MoS(2) films are deposited onto Si/SiO(2) using the mechanical exfoliation technique. The films were then used for the fabrication of field-effect transistors (FETs). These FET devices can be used as gas sensors to detect nitrous oxide (NO). Although the single-layer MoS(2) device shows a rapid response after exposure to NO, the current was found to be unstable. The two-, three-, and four-layer MoS(2) devices show both stable and sensitive responses to NO down to a concentration of 0.8 ppm.

We report the extended growth of Graphene Oxide (GO) flakes using atmospheric pressure ethanol Chemical Vapor Deposition (CVD). GO was used to catalyze the deposition of carbon on a substrate in the ethanol CVD with Ar and H2 as carrier gases. Raman, SEM, XPS and AFM characterized the growth to be a reduced GO (RGO) of