Carbon Nanowalls Research Articles

Flexible and Highly Sensitive Pressure Sensors Based on Microstructured Carbon Nanowalls Electrodes.

Wearable pressure sensors have attracted widespread attention in recent years because of their great potential in human healthcare applications such as physiological signals monitoring. A desirable pressure sensor should possess the advantages of high sensitivity, a simple manufacturing process, and good stability. Here, we present a highly sensitive, simply fabricated wearable resistive pressure sensor based on three-dimensional microstructured carbon nanowalls (CNWs) embedded in a polydimethylsiloxane (PDMS) substrate. The method of using unpolished silicon wafers as templates provides an easy approach to fabricate the irregular microstructure of CNWs/PDMS electrodes, which plays a significant role in increasing the sensitivity and stability of resistive pressure sensors. The sensitivity of the CNWs/PDMS pressure sensor with irregular microstructures is as high as 6.64 kPa−1 in the low-pressure regime, and remains fairly high (0.15 kPa−1) in the high-pressure regime (~10 kPa). Both the relatively short response time of ~30 ms and good reproducibility over 1000 cycles of pressure loading and unloading tests illustrate the high performance of the proposed device. Our pressure sensor exhibits a superior minimal limit of detection of 0.6 Pa, which shows promising potential in detecting human physiological signals such as heart rate. Moreover, it can be turned into an 8 × 8 pixels array to map spatial pressure distribution and realize array sensing imaging.

Front Cover: Hierarchical, Vertically‐Oriented Carbon Nanowall Foam Supercapacitor using Room Temperature Ionic Liquid Mixture for AC Line Filtering with Ultrahigh Energy Density (ChemElectroChem 8/2019)

The Front Cover shows a hierarchical, vertically-oriented carbon nanowall foam supercapacitor that utilizes a room-temperature ionic liquid mixture. More information can be found in the Article by Z. Bo et al. on page 2167 in Issue 8, 2019 (DOI: 10.1002/celc.201801825).

Hierarchical, Vertically‐Oriented Carbon Nanowall Foam Supercapacitor Using Room Temperature Ionic Liquid Mixture for AC Line Filtering with Ultrahigh Energy Density

AbstractThe front cover artwork is provided by Prof. Zheng Bo and Dr. Huachao Yang, Zhejiang University (Zhejiang, China). The image shows a hierarchical, vertically‐oriented carbon nanowall foam supercapacitor that uses a room‐temperature ionic liquid (RTIL) mixture. Read the full text of the article at 10.1002/celc.201801825.

Effect of processing gas compositions on growth of carbon nanowalls by ECR-CVD process

Carbon nanowalls (CNWs) have been synthesized by electron-cyclotron resonance chemical vapour deposition (ECR-CVD) method on Si substrates. During deposition, processing gas compositions were varied to improve growth rate and it was found that replacing inflammable H2 by safer and cheaper N2 improves growth rate of CNWs. Energy dispersive x-ray spectroscopy and Fourier transform Infra-red spectroscopy results showed that N2 did not take part in bond formation. Emissive probe diagnostics showed that increasing precursor gas to 90% of total gas mixture increases impinging ions’ energy by 3.5 times leading to deposition of vertically oriented CNWs on Si substrate.

ZnO/Carbon nanowalls shell/core nanostructures as electrodes for supercapacitors

In this work, carbon nanowalls (CNW) were coated with zinc oxide (ZnO) for use as supercapacitor electrodes. The ZnO layers of different thicknesses were deposited using pulsed laser ablation in oxygen reactive atmosphere. The performance of the CNW-ZnO electrodes was found to be dependent on the thickness of ZnO deposit, which in turn influences the specific capacitance and capacitance retention of the CNW-ZnO electrodes. The areal capacitance of the CNW-ZnO measured in mild electrolyte of 1 M KCl was as high as 4.3 mF·cm−2 at a current density of 0.2 mA·cm−2 and 1.41 mF·cm−2 at a scan rate of 10 mV·s−1 with an enhanced capacitance stability over 26,000 cycles. Such results demonstrate the potential use of ZnO nanostructures for low cost and high performance material for electrochemical capacitors.

Hierarchical nickel cobalt sulfide nanosheet on MOF-derived carbon nanowall arrays with remarkable supercapacitive performance

Nickel cobalt sulfide (CoNi2S4)-based materials have attracted extensive attention as electrodes which arise from their high theoretical capacitance, but their wide application is limited by relatively low electrical conductivity and electrochemical stability. Herein, the metal-organic framework (MOF) derived carbon nanowall arrays (CNWAs) are successfully fabricated on carbon cloth (CC) as secondary substrate, which provides more sites for electrodeposition of CoNi2S4. Furthermore, the integration of Ni layer to bridge CoNi2S4 and CNWAs, which is favorable for fast charge transfer, as well as improved conductivity. Thus, the CC/CNWAs@Ni@CoNi2S4 electrode exhibits a remarkable specific capacitance (3163 F g−1/2825 F g−1 at 1 A g−1/5 mV s−1) and rate capability (1503 F g−1/1500 F g−1 at 40 A g−1/50 mV s−1), outperforming others CoNi2S4-based electrodes reported previously. The as-prepared CC/CNWAs@Ni@CoNi2S4//commercial activated carbon asymmetric supercapacitor demonstrates superior electrochemical performance with maximum energy density of 53.8 W h kg−1 at a power density of 801 W kg−1 and long-term cycling stability with 90.1% retention after 10 000 cycles. These remarkable supercapacitive performances are attributed to the rationally hierarchical architecture, high utilization ratio of active materials and aligned ion diffusion channels of the CC/CNWAs@Ni@CoNi2S4 electrode.

Effect of nitrogen configuration on carbon nanowall surface: Towards the improvement of electrochemical transduction properties and the stabilization of gold nanoparticles

Abstract In this work, unintentionally nitrogen doped carbon nanowall (CNW) films, deposited on silicon substrates, were treated in argon plasma admixed with nitrogen (Ar/N2) or oxygen (Ar/O2). X-ray photoelectron spectroscopy (XPS) showed that oxygen functional groups have been incorporated in various amounts with high nitrogen doping concentration (∼12.5–13.5 at%. for Ar/N2 and Ar/O2 gas mixtures). More importantly, nitrogen configuration on the surface has been modified after the treatment. The electrochemical reactivity of the CNW electrodes, before and after the treatment, was investigated by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy. The CV results indicate that the pyrrolic nitrogen can play a key role in the electrochemical transaction improvement. In addition, deposition of gold (Au) nanoparticles (NPs) onto CNW samples and their interaction with CNWs has been discussed through XPS results. It was suggested that a certain nitrogen configuration there is a promotion of electron donation from nitrogen to the Au NPs. Such findings open the way to design nitrogen doped carbon materials with specific nitrogen configuration to improve electrochemical properties and to prepare better platform for Au NPs for use in catalysis and sensor applications.

Tailoring Electro/Optical Properties of Transparent Boron-Doped Carbon Nanowalls Grown on Quartz.

Carbon nanowalls (CNWs) have attracted much attention for numerous applications in electrical devices because of their peculiar structural characteristics. However, it is possible to set synthesis parameters to vary the electrical and optical properties of such CNWs. In this paper, we demonstrate the direct growth of highly transparent boron-doped nanowalls (B-CNWs) on optical grade fused quartz. The effect of growth temperature and boron doping on the behavior of boron-doped carbon nanowalls grown on quartz was studied in particular. Temperature and boron inclusion doping level allow for direct tuning of CNW morphology. It is possible to operate with both parameters to obtain a transparent and conductive film; however, boron doping is a preferred factor to maintain the transparency in the visible region, while a higher growth temperature is more effective to improve conductance. Light transmittance and electrical conductivity are mainly influenced by growth temperature and then by boron doping. Tailoring B-CNWs has important implications for potential applications of such electrically conductive transparent electrodes designed for energy conversion and storage devices.

Formation of carbon nanowalls by pulsed filtered cathodic vacuum arc deposition

In the present study, Carbon Nanowalls (CNWs) were produced by Pulsed Filtered Cathodic Vacuum Arc Deposition (PFCVAD) on glass substrates. A high purity graphite rod was used as a cathode target. Growth was performed by varying the distance between the target and substrate, namely 1 cm (1A250), 2 cm (2A250) and 3 cm (3A250). No CNW formation has been observed on the substrate, when the target and substrate distance is 3 cm. Amorphous nature of carbon structures has been shown with the Raman measurements. Raman mapping has been also performed to show the vertical wall structures of the CNWs. Surface morphology of the CNWs was investigated by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) measurements. It has been found that the wall widths are roughly 1.8 μm and 1.0 μm for the samples 1A250 and 2A250, respectively. It has also shown that curvier vertical wall structures have formed for samples 2A250 compared to that of 1A250. X-ray Photoelectron Spectroscopy measurements have shown that 40% sp3 CC bonding and CO bonding which indicates the amorphous nature of the structure. Optical studies have shown that CNWs have low reflectance in visible region when the substrate to target distance is 1 cm which makes this thin coating very suitable for dark coating applications.

Photomemristors using carbon nanowall/diamond heterojunctions

Abstract

Hierarchical, Vertically‐Oriented Carbon Nanowall Foam Supercapacitor using Room Temperature Ionic Liquid Mixture for AC Line Filtering with Ultrahigh Energy Density

AbstractSupercapacitors have been considered as a promising alternative of aluminum electrolytic capacitors (AECs) for AC line filtering applications. However, realizing supercapacitors with fast frequency response and superior energy density still remains an open issue. Herein, we demonstrate a hierarchical, vertically‐oriented carbon nanowall foam (CWF) supercapacitor using mixed room temperature ionic liquids (RTILs) for high‐performance AC line filtering. Hierarchical CWF exhibits macrospores as electrolyte reservoirs to shorten ion transport distance, vertically‐oriented, open channels to enable fast ion diffusion and consecutive scaffolds to promote electron transfer. CWF supercapacitor using RTIL mixture realizes a recorded‐high areal energy density of 1.23 μWh cm−2 at 120 Hz (almost ∼2.0 times/∼10.0 times larger than those of organic/aqueous electrolytes, respectively) and fast frequency response (RC time constant=∼1.3 ms). More importantly, CWF supercapacitor achieves a capacitance advantage over commercial AECs up to 1,000 V, substantially larger than those reported in state‐of‐the‐art literatures (maximum of ∼250 V).

Functionalized Carbon Nanowalls as Pro-Angiogenic Scaffolds for Endothelial Cell Activation.

Substrates that can be utilized to assist in expression of the inherent characteristics of cells under in vitro conditions are necessary to mimic the in vivo scenario to the maximum extent possible. We demonstrate the application of functionalized carbon nanowalls (CNW) in facilitating human endothelial cell attachment and proliferation. The CNW films were grown on silicon substrates by surface-wave microwave plasma-enhanced chemical vapor deposition (SWMWPECVD) technique. These CNW were then functionalized using nitrogen (N2) gas plasma to form functionalized N2 doped CNW (CNW-N2). Characterization of CNWs revealed a uniform petal-like morphology with the individual CNW width measured to be 1-5 nm and the film thickness in the range of 10-12 μm. The N2 functionalized CNWs proved to be highly efficient in providing cell-anchorage to the endothelial cells. Profiles of major cytoskeletal proteins revealed a higher degree of expression in the functionalized CNWs depicting the maintenance of structural integrity of cells. Interestingly, the CNW-N2 substrate was found to promote pro-angiogenic factors in the cells, which is observed here for the first time, that could pave way for the utilization of this substrate for detailed studies of angiogenesis processes in vitro and further biomedical applications.

Electrochemical Reaction in Hydrogen Peroxide and Structural Change of Platinum Nanoparticle-Supported Carbon Nanowalls Grown Using Plasma-Enhanced Chemical Vapor Deposition

Hydrogen peroxide (H2O2) reactions on platinum nanoparticle-decorated carbon nanowalls (Pt-CNWs) under potential applications were investigated on a platform of CNWs grown on carbon fiber paper (CFP) using plasma-enhanced chemical vapor deposition. Through repeated cyclic voltammetry (CV), measurements of 1000 cycles using the Pt-CNW electrodes in phosphate-buffered saline (PBS) solution with 240 μM of H2O2, the observed response peak currents of H2O2 reduction decreased with the number of cycles, which is attributed to decomposition of H2O2. After CV measurements for a total of 3000 cycles, the density and height of CNWs were reduced and their surface morphology changed. Energy-dispersive X-ray (EDX) compositional mapping revealed agglomeration of Pt nanoparticles around the top edges of CNWs. The degradation mechanism of Pt-CNWs under potential application with H2O2 is discussed by focusing on the behavior of OH radicals generated by the H2O2 reduction.

Effect of electrical stimulation on proliferation and bone-formation by osteoblast-like cells cultured on carbon nanowalls scaffolds

Carbon nanowalls (CNWs) were synthesized by radical injection plasma-enhanced chemical vapor deposition and used as scaffolds for cell culture. The proliferation of osteoblast-like cells (Saos-2) was enhanced on the CNW scaffold upon electrical stimulation (ES) with 10 Hz square pulses at a current of 226 nA. However, after incubation with ES for 10 d, differentiation of the cells toward bone formation was suppressed.

Effects of 3D structure on electrochemical oxygen reduction characteristics of Pt-nanoparticle-supported carbon nanowalls

For polymer electrolyte fuel cell applications, effects of Pt-nanoparticle-supported 3D carbon nanostructures, i.e. carbon nanowalls (Pt/CNWs), on electrochemical characteristics were determined by alternating current impedance analysis of resistive elements, which contribute to the oxygen reduction reaction. CNWs were fabricated by radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD), and Pt catalysts were formed on the template of CNWs by supercritical fluid metalorganic chemical fluid deposition. CNWs of different wall densities were synthesized during RI-PECVD by varying the deposition pressure. The resistive elements can be consisted of three regions with different corresponding frequencies, and the resistive elements of mass diffusion, which showed up in the lowest frequency region of less than 100 Hz, increased as the wall density of CNWs increased. It was found that the wall density of CNWs was one of the essential parameters of Pt/CNWs for the electrochemical reaction involving the fluid flow and the mass transfer of active materials.

Синтез углеродных наностен методом химического осаждения из газовой фазы в плазме высокочастотного разряда

Синтез углеродных наностен методом химического осаждения из газовой фазы в плазме высокочастотного разряда

V2O5 nanosheets supported on 3D N-doped carbon nanowall arrays as an advanced cathode for high energy and high power fiber-shaped zinc-ion batteries

A 3D hierarchical core–shell nanostructure was designed as an advanced cathode for high energy and high power fiber-shaped Zn-ion batteries.

Pt nanoparticle-supported carbon nanowalls electrode with improved durability for fuel cell applications using C2F6/H2 plasma-enhanced chemical vapor deposition

The electrochemical durability of Pt nanoparticles-supported carbon nanowalls (Pt/CNWs) determined from potential cycle tests was 88% performance after 20 000 cycles and 50% performance around 140 000 cycles when the CNWs were fabricated by the C2F6/H2 plasma-enhanced chemical vapor deposition system (C2F6-CNWs). Even after the extended start/stop-simulation tests of fuel cell Pt/C2F6-CNWs, Pt was aggregated; however, the morphological structure of the CNWs was maintained and no corrosion was evident from scanning electron microscopy observations and Raman analysis. For graphene-based catalyst supports, i.e., the Pt/C2F6-CNWs, graphene crystallinity is essential to extend electrochemical durability by inhibiting corrosion during fuel cell operation.

Oriented Carbon Nanostructures by Plasma Processing: Recent Advances and Future Challenges.

Carbon, one of the most abundant materials, is very attractive for many applications because it exists in a variety of forms based on dimensions, such as zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and-three dimensional (3D). Carbon nanowall (CNW) is a vertically-oriented 2D form of a graphene-like structure with open boundaries, sharp edges, nonstacking morphology, large interlayer spacing, and a huge surface area. Plasma-enhanced chemical vapor deposition (PECVD) is widely used for the large-scale synthesis and functionalization of carbon nanowalls (CNWs) with different types of plasma activation. Plasma-enhanced techniques open up possibilities to improve the structure and morphology of CNWs by controlling the plasma discharge parameters. Plasma-assisted surface treatment on CNWs improves their stability against structural degradation and surface chemistry with enhanced electrical and chemical properties. These advantages broaden the applications of CNWs in electrochemical energy storage devices, catalysis, and electronic devices and sensing devices to extremely thin black body coatings. However, the controlled growth of CNWs for specific applications remains a challenge. In these aspects, this review discusses the growth of CNWs using different plasma activation, the influence of various plasma-discharge parameters, and plasma-assisted surface treatment techniques for tailoring the properties of CNWs. The challenges and possibilities of CNW-related research are also discussed.

Comparative Study of Graphite and the Products of Its Electrochemical Exfoliation

A comparative study of electrochemical characteristics of graphite electrodes and precipitates of suspensions produced by the graphite exfoliation is carried out. The graphite is exfoliated into low-layered graphene structures formed in the course of electrochemical impact during the applying of alternating potential to the electrodes. The low-layered graphene structures and graphite electrodes were characterized using numerous procedures from optical, electron, and scanning microscopy, UV-vis-, IR-, Raman, and XPSspectroscopy, and thermogravimetric analysis. The rate constant of electron transfer at the initial graphite for [Ru(NH3)6]2+/3+ and [Fe(CN)6]4–/3– redox pairs is shown to approach the value measured both for the lowlayered graphene structures obtained during the graphite electrode exfoliation and for highly oriented carbon nanowalls and single-walled nanotubes measured earlier. At the same time, the Fe2+/3+ redox-process occurring at the graphite electrode is faster than at the low-layered graphene structures and much faster (by 2–3 orders of magnitude) than at the nanowalls. It is concluded that no significant acceleration of the electron transfer generally occurs when passing from the graphite electrodes to the low-layered graphene structures.