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  • Surface-enhanced Raman scattering of graphene caused by self-induced nanogating by GaN nanowire array
    Carbon (IF 6.337) Pub Date : 2017-11-24
    J. Kierdaszuk, P. Kaźmierczak, R. Bożek, J. Grzonka, A. Krajewska, Z.R. Zytkiewicz, M. Sobanska, K. Klosek, A. Wołoś, M. Kamińska, A. Wysmołek, A. Drabińska

    A constant height of gallium nitride (GaN) nanowires with graphene deposited on them is shown to have a strong enhancement of Raman scattering, whilst variable height nanowires fail to give such an enhancement. Scanning electron microscopy reveals a smooth graphene surface which is present when the GaN nanowires are uniform, whereas graphene on nanowires with substantial height differences is observed to be pierced and stretched by the uppermost nanowires. The energy shifts of the characteristic Raman bands confirms that these differences in the nanowire height has a significant impact on the local graphene strain and the carrier concentration. The images obtained by Kelvin probe force microscopy show clearly that the carrier concentration in graphene is modulated by the nanowire substrate and dependent on the nanowire density. Therefore, the observed surface enhanced Raman scattering for graphene deposited on GaN nanowires of comparable height is triggered by self-induced nano-gating to the graphene. However, no clear correlation of the enhancement with the strain or the carrier concentration of graphene was discovered.

    更新日期:2017-11-24
  • Superior potassium storage in chitin-derived natural nitrogen-doped carbon nanofibers
    Carbon (IF 6.337) Pub Date : 2017-11-24
    Rui Hao, Hao Lan, Chengwei Kuang, Hua Wang, Lin Guo

    Potassium ion batteries (KIBs) are drawing intensive attention as the next-generation energy storage technology, owning to their similar electrochemical properties to lithium system and rich abundance of potassium resources. The carbonaceous materials with low cost, nontoxicity and high safety have been considered as promising candidates for KIBs anodes. However, they still suffer from several problems, such as poor cycling and rate capability, complex activation process steps and multiple procedures to import heteroatoms doping. Herein, the N-doped carbon nanofibers (NCFs) are fabricated by direct pyrolysis of bio-waste chitin, which is the second most abundant biopolymer throughout nature. The as-prepared NCFs used as KIBs anodes, without any additional activation steps, are systematically investigated for the first time. They deliver high capacity, excellent rate capability and long-term cycling stability, which benefit from the multiple synergistic effects of suitable interlayer spacing, heteroatom doping and unique one dimensional mesoporous structure. With the spotlight of environmental friendliness, low cost and high energy density in energy storage field, the chitin-based NCFs demonstrate great potential for future low-cost energy storage applications.

    更新日期:2017-11-24
  • Transformation of C60 fullerene aggregates suspended and weathered under realistic environmental conditions
    Carbon (IF 6.337) Pub Date : 2017-11-24
    Josep Sanchís, Yann Aminot, Esteban Abad, Awadhesh N. Jha, James W. Readman, Marinella Farré

    The occurrence, fate and behaviour of carbon nanomaterials in the aquatic environment are dominated by their functionalization, association with organic material and aggregation behaviour. In particular, the degradation of fullerene aggregates in the aquatic environment is a primary influence on their mobility, sorption potential and toxicity. However, the degradation and kinetics of water suspensions of fullerenes remain poorly understood.In the present work, first, an analytical method based on liquid chromatography and high-resolution mass spectrometry (LC-HRMS) for the determination of C60 fullerene and their environmental transformation products was developed. Secondly, a series of C60 fullerene water suspensions were degraded under relevant environmental conditions, controlling the salinity, the humic substances content, the pH and the sunlight irradiation. Up to ten transformation products were tentatively identified, including epoxides and dimers with two C60 units linked via one or two adjacent furane-like rings. Fullerenols were not observed under these environmentally relevant conditions.The kinetics of generation of each transformation product were studied with and without simulated sunlight conditions. The ionic strength of the media, its pH and the humic substances content were observed to modulate the kinetics of generation.

    更新日期:2017-11-24
  • Precursor gas composition optimisation for large area boron doped nano-crystalline diamond growth by MW-LA-PECVD
    Carbon (IF 6.337) Pub Date : 2017-11-24
    A. Taylor, P. Ashcheulov, P. Hubík, L. Klimša, J. Kopeček, Z. Remes, Z. Vlčková Živcová, M. Remzová, L. Kavan, E. Scheid, J. Lorinčík, V. Mortet

    We report on the optimisation of precursor gas composition for the repeatable preparation of large area highly conductive boron doped nano-crystalline diamond layers with low sp2 content using microwave plasma enhanced linear antenna chemical vapour deposition apparatus. The precursor gas composition parameter space was probed by varying the boron, oxygen and carbon atomic ratios whilst fixing all other parameters constant. By radically increasing the B content and careful consideration of the B and O content in the gas phase, thin B-NCD layers (∼300 nm) were prepared over large areas, repeatable, with high boron concentrations (∼2 × 1021 at/cm3) and electrical conductivity levels akin to B-NCD layers prepared in conventional MW PECVD systems (>35 S cm−1) with electrochemical properties suitable for industrial applications.

    更新日期:2017-11-24
  • C3B monolayer as an anchoring material for lithium-sulfur batteries
    Carbon (IF 6.337) Pub Date : 2017-11-23
    Yu Qie, Junyi Liu, Shuo Wang, Sheng Gong, Qiang Sun

    The shuttle effect caused by polysufides dissolution and diffusion in electrolyte solutions severely hinders the practical application of Li<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">S batteries. To overcome this problem for achieving long cycle life and high rate performance, anchoring materials are highly desirable. In this work, for the first time, we explore the anchoring behaviors of polysulfides on C3B and C3N monolayers with reference to pristine graphene by using density functional theory computations. The complicated anchoring mechanisms are further explored by analyzing the competition between van der Waals, electrostatic, and chemical interactions. Our results suggest that C3B monolayer shows the best anchoring performance for lithium polysulfides due to the strong chemical interaction induced by charge transfer while C3N monolayer has relative weak anchoring effect due to the electrostatic interaction. Based on the enhanced conductivity, strong anchoring ability, and improved rate capability, C3B monolayer shows the promise as an anchoring material for lithium-sulfur batteries.

    更新日期:2017-11-24
  • White-emitting carbon dots with long alkyl-chain structure: Effective inhibition of aggregation caused quenching effect for label-free imaging of latent fingerprint
    Carbon (IF 6.337) Pub Date : 2017-11-23
    Bang-Ping Jiang, Yun-Xiang Yu, Xiao-Lu Guo, Zhao-Yang Ding, Bo Zhou, Hong Liang, Xing-Can Shen

    The surface functionalization of carbon dots (CDs) can introduce an additional dimension for the control of their photoluminescence properties and effective promotion of the applications of CDs such as imaging, sensing, etc. In this study, a simple one-step carbonization using Tween 80 as the sole carbon source is described for directly synthesizing white-emitting CDs (WCDs) in high yield. The results revealed the presence of several long alkyl chains on the surface of the as-fabricated WCDs, which effectively suppress the aggregation-caused quenching (ACQ) effect and emit bright white luminescence under an UV illumination of 365 nm in the solution and solid states. Besides, together with the surface protection of long alkyl chains, WCDs preferentially interact with lipophilic fatty residues and are beneficial for the label-free imaging of latent fingerprints. This study provides a promising new method to not only effectively inhibit the intrinsic ACQ effect of CDs but also develop the surface engineering of functionalized white-emitting CDs for practical applications via facile synthesis.

    更新日期:2017-11-24
  • A novel approach for forming carbon nanorods on the surface of carbon felt electrode by catalytic etching for high-performance vanadium redox flow battery
    Carbon (IF 6.337) Pub Date : 2017-11-23
    Saleem Abbas, Hyuck Lee, Jinyeon Hwang, Asad Mehmood, Hyun-Jin Shin, Sheeraz Mehboob, Ju-Young Lee, Heung Yong Ha

    In this work a novel method is unfolded to modify carbon felts (CF) to substantially improve the performance of the electrodes for vanadium redox flow batteries (VRFBs). The carbon felt, a well-known electrode material for VRFB, is catalytically etched by cobalt oxide to form carbon nanorods on the surface of the fibers comprising the CF. Unlike conventional multistep processes to grow nano-structures on carbon felts, this method simply involves a thermal treatment of catalyst-loaded felt in air to produce well aligned nanorods on its fibers. The surface morphology is optimized by etching temperature, treatment time and catalyst type. The catalytically etched CF shows an improved surface wettability and an enlarged specific surface area about two times compared to pristine CF that lead to an improvement of kinetics towards vanadium redox reactions. When used as electrode in all-vanadium redox flow battery, the nanorod-structured CF shows around 35% higher charge/discharge rate capability at 150 mA cm−2 and 80% retained-capacity compared to 48% in case of un-etched CF as confirmed by a long run test with a hundred cycles of charge/discharge operation at 50 mA cm−2.

    更新日期:2017-11-23
  • Carbon dots with red-shifted photoluminescence by fluorine doping for optical bio-imaging
    Carbon (IF 6.337) Pub Date : 2017-11-23
    Wanning Yang, Hong Zhang, Junxin Lai, Xinyi Peng, Yuping Hu, Wei Gu, Ling Ye

    Carbon dots (CDs) are environmentally benign alternatives to quantum dots comprised of heavy metals with outstanding photoluminescent (PL) properties and have shown great promise in optical bio-imaging and sensing. However, it remains challenging to rationally design and synthesize CDs with red PL emission. We herein disclose that a red-shifted PL emission could be achieved by doping the electron-withdrawing fluorine atoms into CDs. Moreover, we demonstrate the preparation of fluorine doped CDs with a red PL emission under excitation at 530 nm by an easy, environmental friendly, one-step microwave-assistant carbonation route. A possible mechanism of the red-shifted emission upon fluorine doping is tentatively proposed. In addition, the applicable of these red-emissive fluorine doped CDs as optical nanoprobes for bio-imaging applications, both in vivo and in vitro, was explored. It is indicated that the as-prepared fluorine doped CDs with red-shifted PL emission are promising candidates for tumor bio-imaging/or diagnostics.

    更新日期:2017-11-23
  • Atomic and electronic structures of stable linear carbon chains on Ag-nanoparticles
    Carbon (IF 6.337) Pub Date : 2017-11-22
    D.W. Boukhvalov, I.S. Zhidkov, E.Z. Kurmaev, E. Fazio, S.O. Cholakh, L. D’Urso

    In this work, we report X-ray photoelectron (XPS) and valence band (VB) spectroscopy measurements of surfactant-free silver nanoparticles and silver/linear carbon chains (Ag@LCC) structures prepared by pulse laser ablation (PLA) in water. Our measurements demonstrate significant oxidation only on the surfaces of the silver nanoparticles with many covalent carbon-silver bonds but only negligible traces of carbon-oxygen bonds. Theoretical modeling also provides evidence of the formation of robust carbon-silver bonds between linear carbon chains and pure and partially oxidized silver surfaces. A comparison of theoretical and experimental electronic structures also provides evidence of the presence of non-oxidized linear carbon chains on silver surfaces. To evaluate the chemical stability, we investigated the energetics of the physical adsorption of oxidative species (water and oxygen) and found that this adsorption is much preferrable on oxidized or pristine silver surfaces than the adsorption of linear carbon chains, which makes the initial step in the oxidation of LCC energetically unfavorable. E-mail: danil@hanyang.ac.kr

    更新日期:2017-11-23
  • Carbons from biomass precursors as anode materials for lithium ion batteries: New insights into carbonization and graphitization behavior and into their correlation to electrochemical performance
    Carbon (IF 6.337) Pub Date : 2017-11-22
    Olga Fromm, Andreas Heckmann, Uta C. Rodehorst, Joop Frerichs, Dina Becker, Martin Winter, Tobias Placke

    We report a comprehensive and systematic study on the preparation and characterization of carbonaceous materials that are obtained from five different sustainable precursor materials and petroleum coke as reference material, particularly focusing on the correlation between the structural transformation of the precursors into carbons in dependence of high temperature treatment (HTT) and their corresponding electrochemical characteristics as anode material in lithium ion batteries. The carbons were carbonized and graphitized in 200 °C steps, covering a broad temperature range from 800 °C to 2800 °C. So far, such a systematic synthesis approach has not been reported in literature. For biomass-derived carbons, we found a heterogeneous (discontinuous) graphitization process, i.e. a transformation from the amorphous to the graphitic phase via the turbostratic phase. A general trend was observed for the discharge capacity, i.e. a decrease of capacity from 800 °C to ≈1800–2000 °C, followed by an increase of capacity for temperatures >2000 °C. An increase of the 1st cyle Coulombic efficiency was found and could be directly correlated to the decrease of the “non-basal plane” surface area upon HTT. In addition, we found that the voltage efficiency and energy efficiency of the different carbons also increase with rising treatment temperatures.

    更新日期:2017-11-23
  • Nest-like assembly of the doped single-walled carbon nanotubes with unique mesopores as ultrastable catalysts for high power density Zn-air battery
    Carbon (IF 6.337) Pub Date : 2017-11-21
    Qiangmin Yu, Chuxin Wu, Jiaoxing Xu, Yi Zhao, Jianshuo Zhang, Lunhui Guan

    Uniform nest-like structures with high surface areas and unique pore sizes were prepared by self-assembly of the oxidized single-walled carbon nanotubes (SWCNT). After doping with cobalt and nitrogen, the assembly exhibited much higher electrocatalytic activity for the oxygen reduction reaction than the commercial Pt/C catalyst. Benefited from effective exposing the active sites and sufficient diffusion pathways of O2 for fast reaction kinetic, when used as the air electrode catalysts for a Zn-air battery, the power density constructed by the assembly reached as high as 248 mW cm−2 under the high current density of 330 mA cm−2, superior to that of Pt/C air-cathode (195 mW cm−2) and other non-precious metal catalysts ever reported.

    更新日期:2017-11-22
  • Self-terminated activation for high-yield production of N,P-codoped nanoporous carbon as an efficient metal-free electrocatalyst for Zn-air battery
    Carbon (IF 6.337) Pub Date : 2017-11-21
    Hao Luo, Wen-Jie Jiang, Yun Zhang, Shuai Niu, Tang Tang, Lin-Bo Huang, Yu-Yun Chen, Zi-dong Wei, Jin-Song Hu

    To enhance the electrocatalytic activity of heteroatom doped carbon for oxygen reduction reaction (ORR), high surface area and favorable porous structure are commonly required for providing sufficient accessible active sites. However, these features usually come with the severe carbon loss during pyrolysis and carbonization activation process. Herein, we report a facile self-terminated activation strategy for high-yield production of nitrogen and phosphorus codoped nanoporous carbon (NP-NC) by using potassium phytate as carbonaceous source. The in-situ formed potassium species enable the effective carbon activation to create plenty of nanopores without additional corrosive chemicals while the formation of K4P2O7 properly terminates the activation, resulting in the extremely low weight loss less than 17%. Benefited from the high surface area of 1294 m2 g−1 and trimodal nanoporous structure, the resulted N, P-codoped catalyst exhibits superior ORR activity close to Pt/C, high catalytic current density as well as excellent methanol tolerance and durability. Importantly, as cathode catalyst for Zn-air battery, N,P-NC also exhibits current and power densities comparable to the state-of-the art 20% Pt/C. Therefore, such a facile, scalable and high-yield synthesis of N,P-codoped nanoporous carbon materials opens up opportunities for the mass-production of highly efficient cost-effective electrocatalysts for energy applications.

    更新日期:2017-11-21
  • One-pot environment-friendly synthesis of boron doped graphene-SnO2 for excellent anodic performance in Li ion battery
    Carbon (IF 6.337) Pub Date : 2017-11-21
    Madhumita Sahoo, S. Ramaprabhu

    High specific capacity, availability of tin oxide (SnO2) and improved electrical conductivity and rate capability of boron-doped graphene sheets (BG) promises the composite of the two as a potential anode material for Li ion battery. We report for the first time, one-pot synthesis of SnO2 dispersed boron-doped few layer graphene (SnO2/BG-I) in an environment friendly, hazardous-harmful reducing agent free, hydrogen assisted reduction technique in comparison to complicated two-step conventional process. In addition, a two-step, wet chemical free, greener approach is also employed to achieve SnO2 nanoparticles over BG support (SnO2/BG-II). Both the materials as anode showed enhanced performance compared to un-doped graphene supported SnO2 nanoparticles (SnO2/G). One-pot synthesized SnO2/BG-I as anode in Li ion battery shows comparable performance with a reversible capacity of 348 mAh g−1 at a current density 200 mA g−1, while SnO2/BG-II with higher amount of boron doping, exhibits higher stability over cycles with an excellent reversible capacity of 558 mAh g−1 due to the uniform distribution of SnO2 over boron-doped graphene sheets.

    更新日期:2017-11-21
  • New insights into the surface properties of hard-templated ordered mesoporous carbons
    Carbon (IF 6.337) Pub Date : 2017-11-21
    Xiaoan Li, Farisa Forouzandeh, Tobias Fürstenhaupt, Dustin Banham, Fangxia Feng, Siyu Ye, Daniel Y. Kwok, Viola Birss

    Although hard-templated ordered mesoporous carbons (OMCs) have been widely studied in the past decades, their surface properties, especially surface wettability, have not been investigated in detail. This study shows that as-synthesized hard-templated OMCs (sucrose- and anthracene-derived OMCs, i.e., OMC-S and OMC-A, respectively, formed using the identical hexagonal mesoporous silica template) have very different surface characteristics, with OMC-S being significantly more hydrophobic than OMC-A. This is attributed to the presence of a thin, hydrophobic, microporous carbon shell layer surrounding the mesoporous core of the OMC-S particles, seen here for the first time by transmission electron microscope tomography and confirmed by the slower water uptake and slower electrochemical kinetics of OMC-S vs. OMC-A. At the same time, the mesopores within both OMC-S and OMC-A remain hydrophilic, as shown primarily by water vapor sorption measurements, due to the high density of surface oxygen groups inside the pores, as also confirmed by cyclic voltammetry. These oxygen groups are proposed to have been derived from C single bond O single bond Si bonds that formed at the carbon/silica interface during the carbonization process, leaving C single bond OH groups behind after removal of the silica template. These findings are relevant to a broad range of nanoporous carbon surfaces prepared with hard templates.

    更新日期:2017-11-21
  • Utilizing a graphene matrix to overcome the intrinsic limitations of red phosphorus as an anode material in lithium-ion batteries
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Zishuang Yue, Tushar Gupta, Fan Wang, Chao Li, Rajesh Kumar, Zhenyu Yang, Nikhil Koratkar

    Red phosphorus (P) shows enormous potential as a high-performance and cost-effective Lithium (Li)-ion anode material. It alloys with Li forming Li3P, which translates to a theoretical capacity of ∼2595 mAh g−1 (∼7 times better than graphite). Further, the cost of bulk P is comparable to battery-grade graphite. However, there are two intrinsic limitations that prevent deployment of P, viz., its low electrical conductivity and high volume change on cycling that leads to pulverization and loss of electrical contact. We present an approach to concurrently address both limitations. We employ electro-spraying and far-infrared reduction (FIR) to fabricate composites of P and reduced graphene oxide (rGO). The electro-spraying process enables ultra-small P particles (5–10 nm), which suppresses stress-induced pulverization and drastically reduces Li-ion diffusion distances. The low electrical conductivity of P is also not a limitation at such small particle sizes. FIR establishes carbon-phosphorous bonds that prevent surface migration and agglomeration of P, and enable efficient electron transfer between the rGO matrix and P nanoparticles. The P/rGO anode delivers outstanding specific capacity (∼1763 mAh g−1 at current density of ∼0.1 A g−1), extraordinary high-rate capability (up to ∼40 A g−1) and long cycle-life (>1000 cycles with ∼99% coulombic efficiency).

    更新日期:2017-11-21
  • Tubular titanium oxide/reduced graphene oxide-sulfur composite for improved performance of lithium sulfur batteries
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Junhua Song, Jianming Zheng, Shuo Feng, Chengzhou Zhu, Shaofang Fu, Wengao Zhao, Dan Du, Yuehe Lin

    Lithium sulfur (Li single bond S) batteries are promising alternatives to conventional Li-ion batteries in terms of specific capacity and energy. However, the technical challenges raised from the soluble polysulfide (PS) in organic electrolyte deter their implementation in practical applications. Nanoengineered structure and chemical adsorptive materials hold great promise in mitigating the PS migration problem. Here, we develop a tubular titanium oxide (TiO2)/reduced graphene oxide (rGO) composite structure (TG) as a sulfur hosting material for constructing better performed Li single bond S batteries. The TG/sulfur cathode (TG/S) is able to deliver ∼1200 mAh g−1 specific capacity with stable operation for over 550 cycles. Moreover, the TG/S composite cathode shows stable Coulombic efficiencies of over ∼95% at various C rates, which are ∼10% higher than those of the rGO/sulfur (G/S) counterparts. The superior electrochemical performances of TG/S could be ascribed to the synergistic effects between the conductive rGO support and the physically/chemically absorptive TiO2, that is, the spatial tubular structure of TiO2 provides intimate contact and physical confinement for sulfur, while the polar TiO2 in TG/S shows strong chemical interaction towards the sulfur species.

    更新日期:2017-11-21
  • Phosphorus-doped 3D hierarchical porous carbon for high-performance supercapacitors: A balanced strategy for pore structure and chemical composition
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Wang Yang, Wu Yang, Lina Kong, Ailing Song, Xiujuan Qin, Guangjie Shao

    Phosphorus-doped three-dimensional hierarchical porous carbons (P-3DHPCs) have been synthesized by direct pyrolysis of mixture containing glucose, manganese nitrate and sodium hypophosphite without any hard templates. Glucose and sodium hypophosphite are used as carbon and phosphorus source in the facile template-free strategy, respectively. The P-3DHPCs not only possess favorable hierarchical pore structure which is beneficial to ion adsorption and transportation, but also acquire effective heteroatoms doping, further improving the capacitive performance. More importantly, the amount of sodium hypophosphite plays a critical role in textural properties and phosphorus content of P-3DHPCs. The results demonstrate that P-3DHPC-0.2 shows the best electrochemical performance compared to the other samples. High specific capacitance (367 F g−1 at 0.3 A g−1) is obtained in 6 M KOH, and the capacitance still maintains 319 F g−1 when tested at 20 A g−1 (ca.88% capacitance retention). Moreover, the P-3DHPC-0.2 also possesses good cycling stability with only a loss of 3.5% after 10000 cycles at 3 A g−1. The facile preparation method and good electrochemical performance render P-3DHPCs to be a promising candidate for supercapacitor application.

    更新日期:2017-11-21
  • Giant optical absorption and low dark current characteristics in wrinkled single layer graphene/bismuth nanorods heterostructures
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Lichuan Jin, Yong Xiao, Dainan Zhang, Huaiwu Zhang, Xiaoli Tang, Zhiyong Zhong, Qinghui Yang

    Wrinkled graphene shows an enhanced photoelectric effect owing to the opening of a bandgap induced by stress. Here, bismuth (Bi) nanorods array with trigonal orientation are assembly grown on silicon substrates by molecular beam epitaxy. Single layer graphene (SLG) is transferred on top of the Bi nanorods array to make flat SLG forming into wrinkles. Through the application of visible-infrared and Fourier transform infrared spectroscopies, enhanced optical absorption in the wrinkled SLG/Bi nanorod heterostructures was observed. Raman spectral analysis showed a large 2D peak shift of up to −11 cm−1 compared with that of flat graphene on silicon wafers. This finding indicates the existence of a tensile stress induced opening of the band gap. Nonlinear current-voltage characteristics confirmed the opening of an intrinsic bandgap in the wrinkled graphene. The on-off ratio was shown to increase by 30 times and the dark current was remarkably suppressed by 3 to 4 orders of magnitude for the Bi nanorods/wrinkled SLG heterostructures when compared with those properties of flat SLG on silicon.

    更新日期:2017-11-21
  • Chemical etching of a semiconductor surface assisted by single sheets of reduced graphene oxide
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Tomoki Hirano, Kazuki Nakade, Shaoxian Li, Kentaro Kawai, Kenta Arima

    Catalyst-assisted chemical etching is an emerging technology for fabricating a variety of three-dimensional nanostructures on a semiconductor surface for future electronic and optical devices. In contrast to conventional wet etching using noble metals, we performed a fundamental study on the chemical etching of a Ge surface assisted by dispersed sheets of reduced graphene oxide (rGO) in water with dissolved O2 molecules. We found that a monolayer sheet of rGO on Ge does not act as a mask but as a chemical tool that enhances etching under the entire sheet. This is probably caused by the dissociation of adsorbed O2 molecules at the edges of vacancies in an rGO sheet, which leads to the formation of a soluble GeO2 layer. We also propose that the reagents and by-products involved in this etching diffuse along the interface between an rGO sheet and the wall of etched Ge, which we believe is a key for achieving higher etching rates. This study is expected to lead to a nanoscale manufacturing process for semiconductor surfaces free from noble-metal contamination.

    更新日期:2017-11-21
  • Effects of Cu Contamination on System Reliability for Graphene Synthesis by Chemical Vapor Deposition Method
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Changqing Shen, Yi Jia, Xingzhou Yan, Wanli Zhang, Yanrong Li, Fangzhu Qing, Xuesong Li

    Reliability is one of the key specifications of a system. For graphene synthesis by chemical vapor deposition (CVD), previous studies have shown that a trace amount of oxidants can significantly affect graphene growth, either positively or negatively. Other than deliberately introducing oxygen, oxidant impurities may be introduced by the air leaked into the system or from impurities of the reaction gases, which are normally constant and can be balanced by hydrogen and carbon precursors. Here we report a systematic investigation on the effects of Cu contamination on graphene growth, which is very common due to Cu evaporation at high temperature. The accumulated Cu deposited on the quartz tube are inevitably oxidized to form Cu2O and CuO, which result in an introduction of water either due to the desorption of water adsorbed on the rough surface or the reduction of oxides by hydrogen and methane. In addition, the introduction of water in this way is not constant, leading to a non-steady state for graphene growth and may significantly reduce the system reliability. Our finding brings caution to the study on graphene synthesis and the development of its industrial production.

    更新日期:2017-11-21
  • Decoration of graphene with 2-aminoethanethiol functionalized gold nanoparticles for molecular imprinted sensing of erythrosine
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Xiaoyu Zhao, Wenshuai Hu, Yanfei Wang, Liang Zhu, Libin Yang, Zuoliang Sha, Juankun Zhang

    In this account, sodium citrate was used as reductant and stabilizer to decorate reduced graphene oxide (rGO) with 2-aminoethanethiol (2-AET) functionalized and well-distributed gold nanoparticles (AuNPs), as well as to improve the sensitivity and stability of rGO deposited on the electrode surface. The molecular imprinted polymer (MIP) was prepared on the electrode surface using erythrosine (ERT) as the template molecule, and both m-dihydroxybenzene (m-DB) and o-phenylenediamine (o-PD) as functional monomers. A sensitive sensor was then fabricated for the direct determination of ERT. The prepared nanomaterials were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrum analysis (EDX), and infrared spectroscopy (FT-IR). The properties of the resulting sensor were examined by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The data revealed that the as-prepared sensor could achieve wide linear range (3.75 × 10−8 to 1.50 × 10−4 M) and low detection limit (4.77 × 10−9 M), meeting the requirements of ERT trace analysis. The stability and reproducibility of the prepared molecular imprinted electrodes showed excellent long-term stability and relevant reproducibility, making these platforms promising for future electrochemical sensors.

    更新日期:2017-11-21
  • Facile construction of MoS2/RCF electrode for high-performance supercapacitor
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Chunhua Zhao, Yanan Zhou, Zhengxiang Ge, Chongjun Zhao, Xiuzhen Qian

    Aligned reclaimed carbon fiber (RCF) was reused as a conductive support to load hierarchical molybdenum disulfide (MoS2) spheres and thus MoS2/RCF composite was constructed. The synthesis of MoS2 and its loading were simultaneously completed during a facile hydrothermal process. This MoS2/RCF was directly utilized as the negative electrode for supercapacitor without any further process, which exhibited superior electrochemical performance: A specific capacitance of 225 F g-1 at 0.5 A g-1. Furthermore, an asymmetric supercapacitor (ASC) was assembled by coupling this MoS2/RCF electrode (-) with MnO2/RCF electrode (+), which delivered an energy density of 22.5 W h kg-1 at a power density of 703 W kg-1 over a wide potential range of 1.7 V. This RCF may be a promising conductive support candidate for those electrodes in the energy storage devices.

    更新日期:2017-11-21
  • Facile synthesis of N-doped carbon layer encapsulated Fe2N as an efficient catalyst for oxygen reduction reaction
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Zaojin Liu, Jing Yu, Xingyun Li, Lixue Zhang, Dong Luo, Xuehua Liu, Xiaowei Liu, Shuibo Liu, Hongbin Feng, Guanglei Wu, Peizhi Guo, Hongliang Li, Zonghua Wang, Xiu Song Zhao

    Development of non-noble metal catalysts for oxygen reduction reaction (ORR) is of significant importance for the commercialization of fuel cells and metal-air batteries. Here we provide an efficient method to produce core-shell structured Fe single bond N single bond C catalyst via a facile in-situ chelating strategy by introducing ammonia iron citrate during the polymerization process of dopamine. The influence of calcination temperature and atmosphere on the physicochemical property and the activity of the catalyst are systematically evaluated. By calcination at 800 °C with NH3 atmosphere, Fe2N encapsulated with N doped carbon layers shows excellent activity with close onset and half wave potential (E1/2) while better methanol crossover resistance than the Pt/C catalyst. The high activity could be due to the synergistic effect of Fe2N with the N-doped graphitic carbon layers and the mesoporous structure facilitating the mass transfer. Moreover, the simple synthesis process could provide a versatile routine to construct core-shell structured metal-N single bond C composite for a wild catalytic application.

    更新日期:2017-11-21
  • Covalent coupling of porphines to graphene edges: Quantum transport properties and their applications in electronics
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Jing Zeng, Ke-Qiu Chen, Yu-Xuan Tong

    Recently, He et al. succeeded in covalently linking porphines to graphene edges on a Ag(111) substrate by dehydrogenative coupling [Nat. Chem. 9 (1) (2017) 33–38], thus created a new hybrid material with tunable functionalities. Motivated by this work, we further investigate the electron transport properties of three porphine/graphene coupling motifs observed by scanning-probe technology with submolecular resolution in the experiment. By using density-functional theory combined with the Keldysh nonequilibrium Green's technique, we find many interesting electron transport phenomena in these new hybrid structures. Conductivity enhancement can be observed when porphines are covalently bound to the edges of specific armchair graphene nanoribbon (AGNR) and symmetric zigzag GNR (ZGNR). However, the origin of conductivity enhancement in the AGNR related hybrid system is completely different from that in the ZGNR related system. Moreover, negative differential resistance (NDR) behaviors can be found in ZGNR related coupling configurations. In particular, two different NDR mechanisms are found in these hybrid systems.

    更新日期:2017-11-21
  • Rice husk-derived hard carbons as high-performance anode materials for sodium-ion batteries
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Qiaoqiao Wang, Xiaoshu Zhu, Yuhan Liu, Yuyan Fang, Xiaosi Zhou, Jianchun Bao

    Sodium-ion batteries (SIBs) have drawn ever-increasing attention for scalable electrical energy storage owing to the inexhaustible sources and wide distribution of sodium. However, to develop feasible anode materials still remains a great challenge for the practical application of SIBs. Here, we report hard carbons derived from a plentiful and deserted biomass of rice husk through a facile acid treatment and subsequent pyrolysis. The investigation illustrates that the electrochemical properties of the rice husk-derived hard carbons (RHHCs) are significantly influenced by the pyrolysis temperature because of the discrepancy in their microstructure. The RHHC pyrolyzed at 1300 °C (RHHC-1300) shows the highest reversible capacity of 372 mAh g−1 and good cycling stability and rate performance due to its large interlayer distance and suitable oxygen content. Moreover, full sodium-ion batteries are assembled to examine the application prospect using Na3V2(PO4)2F3/C and RHHC-1300 as cathode and anode materials, respectively, delivering a high-energy density of 185 Wh kg−1 and stable cycling performance. This work could intensify the fundamental understanding of the sodium storage mechanism in biomass-derived hard carbons.

    更新日期:2017-11-21
  • Monoclinic C16: sp2-sp3 Hybridized Nodal-Line Semimetal Protected by PT-Symmetry
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Xing Feng, Quansheng Wu, Yong Cheng, Bin Wen, Qian Wang, Yoshiyuki Kawazoe, Puru Jena

    Based on first-principles calculations and Wannier tight-binding model, a three-dimensional (3D) carbon structure, named mC16, composed of interpenetrating graphene, is shown to be a topological nodal-line semimetal. The band structure calculations reveal that mC16 exhibits some exceptional properties. These include the Dirac band and band inversion around the Fermi level, and four nodal-lines in the entire Brillouin zone, symmetrically distributed on both sides of the mirror plane, and protected by the PT symmetry. In addition, the topological “drumhead-like” surface states appear on the (001) surface of mC16 and the double “drumhead-like” flat surface state emerges on the type-II (001) surface of the 3D mC16 structure. Moreover, the exotic surface Dirac points are located on the type-I (001) surface, implying that mC16 may process interesting surface transport properties. These new features make mC16 a new member in the topological carbon family, with promising novel applications in electronic device.

    更新日期:2017-11-21
  • The influence of hydrogen on transition metal - Catalysed graphene nucleation
    Carbon (IF 6.337) Pub Date : 2017-11-20
    I. Mitchell, A.J. Page

    We demonstrate how hydrogen influences graphene nucleation on two archetypal catalysts, Cu(111) and Ni(111), using first-principles methods. The graphene nucleation mechanism is shown to be the result of the balance between the nature and strength of the carbon – metal interaction, and the influence of the hydrogen chemical potential on adsorbed carbon fragments. While the former drives the formation of ring structures in carbon fragments, the latter promotes the growth of saturated carbon chain structures during the nucleation process. Importantly, our results reveal how the presence of hydrogen dramatically influences the nature of the sp → sp2 transition, a key step in the nucleation of both graphene and carbon nanotubes. Increasing the presence of hydrogen during nucleation stabilises smaller ring structures earlier in the nucleation process, in fragments as small as carbon pentagons, which are known to be a key intermediate structure in carbon nanostructure nucleation. Conversely, lower hydrogen chemical potentials lead to the formation of carbon ring structures only in much larger fragments. These results present a new potential route by which hydrogen leads to greater control over CVD-synthesised carbon nanotubes and graphene, i.e. by driving the formation of smaller, more stable ring structures earlier in the growth process.

    更新日期:2017-11-21
  • Rationally regulating complex dielectric parameters of mesoporous carbon hollow spheres to carry out efficient microwave absorption
    Carbon (IF 6.337) Pub Date : 2017-11-20
    Yan Cheng, Zhaoyong Li, Yong Li, Sisi Dai, Guangbin Ji, Huanqin Zhao, Jieming Cao, Youwei Du

    In this study, the mesoporous carbon hollow spheres (MCHS) have been prepared through a facile hard-template etching strategy. It is confirmed that the tetrapropoxysilane (TPOS) has distinct influence on the dispersity, hollow cavity and shell thickness of MCHS. Furthermore, MCHS with different construction can regulate dielectric and microwave absorption effectively. We also proved that the generated hollow void and mesporous lay in carbon spheres could boost dielectric loss ability and impedance match behavior. When the addition of TPOS is 1.73 mL, the high specific surface area of MCHS can be achieved, in addition, the maximum reflection loss value of −50.9 dB at 11.1 GHz with a thickness of 3.2 mm can be gained. Moreover, corresponding effective bandwidth can be reached to 5.4 GHz ranging from 9.1 to 14.5 GHz. Besides, MCHS prepared by 3.46 mL TPOS can achieve broad bandwidth of 6.5 GHz (from 11.2 to 17.7 GHz) under 2.0 mm. The excellent microwave absorption capability of MCHS can be ascribed to the strong dielectric loss, hollow void and mesoporous in carbon shell, which were beneficial to the reflection and absorption of the microwave. Such light and efficient absorbers may be as predominant candidate for the applied in microwave absorption territory.

    更新日期:2017-11-21
  • Dispersion of optical and structural properties in gel column separated carbon nanoparticles
    Carbon (IF 6.337) Pub Date : 2017-11-17
    Alina A. Kokorina, Ekaterina S. Prikhozhdenko, Nadezda V. Tarakina, Andrei V. Sapelkin, Gleb B. Sukhorukov, Irina Y. Goryacheva

    We report an effective and simple method for separation of carbon nanodots (CNDs) by size-exclusion chromatography that yields CNDs fractions with different sizes and luminescent properties. As a result, three major types of CNDs with spectrally distinct luminescent centers were identified. The first type of luminescent particles has emission maxima at about 400–440 nm, the highest size and luminescence intensity. CNDs of the second type have a middle size and the lowest luminescence intensity with emission maxima in the range 450–470 nm. The distinctive feature of these two fractions is the excitation-dependent shift of the emission maxima to longer wavelengths. The third type of CNDs has luminescence around 520 nm with no emission shift upon the increase of excitation wavelength and the smallest size. The observed spectral variations in different fractions correlate with a change in average particle size as seen in TEM images. Size fractionation of CNDs mixture is very important to many fields, mostly for bioimaging and medicine applications because it leads to CNDs' unified distribution and behavior. Dilution of CNDs in water suspension leads to the increase of emission intensity and shifts the PL spectra to shorter wavelengths providing evidence for concentration quenching effect in CNDs.

    更新日期:2017-11-17
  • Influence of chemical bonding on the variability of diamond-like carbon nanoscale adhesion
    Carbon (IF 6.337) Pub Date : 2017-11-17
    Rodrigo A. Bernal, Polun Chen, J. David Schall, Judith A. Harrison, Yeau-Ren Jeng, Robert W. Carpick

    Diamond-like-carbon (DLC) is a promising material for tribological applications such as hard-disks, automotive, machine-tool, and aerospace coatings. We performed in-situ transmission electron microscopy (TEM) and molecular dynamics (MD) studies of nanoscale single-asperities made of tetrahedral amorphous carbon (ta-C, a type of DLC with high strength) contacting single-crystal diamond, to understand the factors controlling adhesion. Visualization of the contacts in TEM enabled us to correlate the asperity's geometry and the adhesion measurements. MD simulations allowed the atomic-scale mechanisms of adhesion to be elucidated and correlated with the TEM observations. Experimentally-determined pull-in forces show less scatter than pull-off forces. The magnitude of the pull-in forces is consistent with adhesion arising from van der Waals (VDW) interactions, allowing us to estimate the ta-C/diamond Hamaker constant. MD simulations with the AIREBO potential confirmed that including VDW interactions leads to less scatter in adhesive forces in approach than in separation. MD simulations with the REBO+S potential demonstrate that the large scatter in pull-off forces observed experimentally arises from the complex nature of covalent bonding between substrate and tip, influenced by the local energy landscape, hydrogen coverage, and the number of repeated contact events. The scatter in pull-off force also tends to decrease with increasing roughness.

    更新日期:2017-11-17
  • Lateral heterostructures of two-dimensional materials by electron-beam induced stitching
    Carbon (IF 6.337) Pub Date : 2017-11-17
    Andreas Winter, Antony George, Christof Neumann, Zian Tang, Michael J. Mohn, Johannes Biskupek, Nirul Masurkar, Leela Mohana Reddy Arava, Thomas Weimann, Uwe Hübner, Ute Kaiser, Andrey Turchanin

    We present a novel methodology to synthesize two-dimensional (2D) lateral heterostructures of graphene and MoS2 sheets with molecular carbon nanomembranes (CNMs), which is based on electron beam induced stitching. Monolayers of graphene and MoS2 were grown by chemical vapor deposition (CVD) on copper and SiO2 substrates, respectively, transferred onto gold/mica substrates and patterned by electron beam lithography or photolithography. Self-assembled monolayers (SAMs) of aromatic thiols were grown on the gold film in the areas where the 2D materials were not present. An irradiation with a low energy electron beam was employed to convert the SAMs into CNMs and simultaneously stitching the CNM edges to the edges of graphene and MoS2, therewith forming a heterogeneous but continuous film composed of two different materials. The formed lateral heterostructures possess a high mechanical stability, enabling their transfer from the gold substrate onto target substrates and even the preparation as freestanding sheets. We characterized the individual steps of this synthesis and the structure of the final heterostructures by complementary analytical techniques including optical microscopy, Raman spectroscopy, atomic force microscopy (AFM), helium ion microscopy (HIM), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) and find that they possess nearly atomically sharp boundaries.

    更新日期:2017-11-17
  • Humidity and CO2 gas sensing properties of double-layer graphene
    Carbon (IF 6.337) Pub Date : 2017-11-17
    Xuge Fan, Karim Elgammal, Anderson D. Smith, Mikael Östling, Anna Delin, Max C. Lemme, Frank Niklaus

    Graphene has interesting gas sensing properties with strong responses of the graphene resistance when exposed to gases. However, the resistance response of double-layer graphene when exposed to humidity and gasses has not yet been characterized and understood. In this paper we study the resistance response of double-layer graphene when exposed to humidity and CO2, respectively. The measured response and recovery times of the graphene resistance to humidity are on the order of several hundred milliseconds. For relative humidity levels of less than ∼3% RH, the resistance of double-layer graphene is not significantly influenced by the humidity variation. We use such a low humidity atmosphere to investigate the resistance response of double-layer graphene that is exposed to pure CO2 gas, showing a consistent response and recovery behaviour. The resistance of the double-layer graphene decreases linearly with increase of the concentration of pure CO2 gas. Density functional theory simulations indicate that double-layer graphene has a weaker gas response compared to single-layer graphene, which is in agreement with our experimental data. Our investigations contribute to improved understanding of the humidity and CO2 gas sensing properties of double-layer graphene which is important for realizing viable graphene-based gas sensors in the future.

    更新日期:2017-11-17
  • Spin-charge transport properties for graphene/graphyne zigzag-edged nanoribbon heterojunctions: A first-principles study
    Carbon (IF 6.337) Pub Date : 2017-11-16
    Liemao Cao, Xiaobo Li, Chunxia Jia, Guang Liu, Ziran Liu, Guanghui Zhou

    Graphene and graphyne hold great potential for spintronic device applications due to their exceptionally good electrical and mechanical properties in the pristine form. Recently, considering these 2D carbon allotropes have similar bond lengths and unit cell shapes, ensuring a perfectly matched interface between them and construction of graphene/graphyne heterojunctions feasible. To this end, we study the spin-charge transport properties for monolayer graphene/graphyne zigzag-edged nanoribbon heterojunctions by employing the ab initio calculations, where two types of γ- and (6,6,12)-graphynes are considered, respectively. Our important result here is that these heterojunctions can exhibit an interesting variation of magnetoresistane by applying ferromagnetic stripes or external magnetic fields onto the ribbons to initially orient their spin configuration. Specifically, the magnetoresistance ratio can be up to 104% for graphene/γ-graphyne heterojunction, but only 300% for the graphene/(6,6,12)-graphyne one. In addition, the effects of spin-filtering and negative differential resistance are also observed in those heterojunctions. The maximum of spin filtering efficiency can be up to 99%. The mechanisms are revealed and analyzed by the connection of these effects to the evolution of the spin-resolved electron transmission spectra and pathways around the Fermi level at zero bias.

    更新日期:2017-11-16
  • Synthesis and Optoelectronic Applications of Graphene/Transition Metal Dichalcogenides Flat-Pack Assembly
    Carbon (IF 6.337) Pub Date : 2017-11-16
    Henan Li, Yumeng Shi, Lain-Jong Li

    Being a representative candidate from the two-dimensional (2D) materials family, graphene has been one of the most intensively researched candidates because of its ultrahigh carrier mobility, quantum Hall effects, excellent mechanical property and high optical transmittance. Unfortunately, the lack of a band gap makes graphene a poor fit for digital electronics, where the current on/off ratio is critical. Huge efforts have been advocated to discover new 2D layered materials with wonderful properties, which complements the needs of 2D electronics. Appropriately designed graphene based hybrid structure could perform better than its counterpart alone. The graphene hybrid structure soon become one of the most exciting frontiers in advanced 2D materials, and many efforts have been made to create artificial heterostructures by assembling of graphene with various layered materials. In this review, we present the recent development in synthesis and applications of graphene based 2D heterostructures. Although 2D transition metal dichalcogenide semiconductors have been demonstrated as strong candidates for next-generation electronics and optoelectronics, by combining advantages of various properties of 2D materials together with graphene, it is highly possible to build entire digital circuits using atomically thin components, and create many novel devices that can be utilized in different areas.

    更新日期:2017-11-16
  • Fabricating Pt-decorated three dimensional N-doped carbon porous microspherical cavity catalyst for advanced oxygen reduction reaction
    Carbon (IF 6.337) Pub Date : 2017-11-15
    Yaru Cheng, Huiting Lu, Kai Zhang, Fan Yang, Wenhao Dai, Conghui Liu, Haifeng Dong, Xueji Zhang

    Abundant and low-cost materials with high electrochemical catalytic activity for oxygen reduction reaction (ORR) are in urgent demand for energy storage and conversion devices. In this work, an advanced ORR electrocatalyst of Pt-decorated three dimensional (3D) N-doped carbon porous microspherical cavity (Pt<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">N/C PMC) was fabricated by using polystyrene microspheres (PS) as template, and dopamine and K2PtCl6 as precursors. Microscopic and spectroscopic characterizations revealed large surface area available and affluent pore structures were observed in the resulted Pt<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">N/C PMCs, and numerous Pt nanoparticles (NPs) with active (111) facet were decorated on the surface of N/C PMCs. The proposed Pt<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">N/C CMCs presented good onset potential, remarkable mass activity (MA) and specific activity (SA), superb methanol tolerance and excellent durability toward ORR in alkaline solutions. The numerous decorated Pt with high active (111) facet coupled with high content of active pyridinic and graphitic nitrogen synergistically contributed to the enhanced ORR activity, while the unique 3D porous structures facilitated O2 and electrolyte transport during the ORR process. This work may open new avenue for designing advanced and cost-effective Pt-based ORR catalyst.

    更新日期:2017-11-16
  • Tailored CuO nanostructures decorated amorphous carbon nanotubes hybrid for efficient field emitter with theoretical validation
    Carbon (IF 6.337) Pub Date : 2017-11-15
    Supratim Maity, Swati Das, Dipayan Sen, Kalyan Kumar Chattopadhyay

    Amalgamation of excellent properties of semiconductor nanostructure and carbon nanotubes (CNT) creates advanced material with superior properties which are otherwise unachievable. Here we report cupric oxide (CuO) nanostructure decorated amorphous carbon nanotubes (aCNT) with improved field emission properties. Sharp wedge shaped CuO nanostructure attached aCNT is prepared by a simple cost effective large scale synthesis procedure. Pristine aCNT and CuO-aCNT hetero structure are characterised by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Field emission properties of CuO-aCNT hybrid structure is compared with bare aCNT sample. The turn-on field of CuO-aCNT in comparison with pristine aCNT is downshifted from 8.07 V/μm to 3.73 V/μm. Density functional theory calculation of aCNT and CuO-aCNT hybrid model has been employed to calculate the work function and hence to estimate the field enhancement factor. This theoretical study has supported our experimental result. Furthermore, the origin of local field enhancement of the hybrid nanostructure is examined by finite element modelling method.

    更新日期:2017-11-15
  • Next generation membranes —using tailored carbon
    Carbon (IF 6.337) Pub Date : 2017-11-15
    Oishi Sanyal, Chen Zhang, Graham B. Wenz, Shilu Fu, Nitesh Bhuwania, Liren Xu, Meha Rungta, William J. Koros

    Carbon molecular sieve (CMS) membranes are a special class of nanoporous membranes with angstrom-level molecular discrimination properties, which make them appealing for separating a wide spectrum of gas-pairs. The mechanism of pyrolysis by which a polymer coil is transformed into these rigid sieves is complex; however, we present a framework that can explain this transformation. Representative polymer precursors and pyrolysis conditions are discussed that yield attractive CMS membrane separation performance for extremely challenging gas pairs. Control of penetrant motions in the diffusion activated state, reflected in the entropy of activation of subtly different penetrants, enables the attractive diffusion selectivity of such membranes. This control, virtually absent even in rigid state-of-the-art polymeric membranes, makes CMS materials extraordinarily attractive. Moreover, unlike other rigid sieving materials, CMS membranes have the added advantage of being processable into highly productive, flexible hollow fibers with good mechanical properties and long-term stability under constant gas feeds. In this article, we also identify some key areas of CMS which would greatly benefit from expertise from other fields like computation or materials characterization that can potentially complement transport-based studies.

    更新日期:2017-11-15
  • 3D superelastic graphene aerogel-nanosheet hybrid hierarchical nanostructure as high-performance supercapacitor electrode
    Carbon (IF 6.337) Pub Date : 2017-11-15
    Qiangqiang Zhang, Yu Wang, Baoqiang Zhang, Keren Zhao, Pingge He, Boyun Huang

    A three-dimensional graphene-based nanostructure with graphene aerogel templating graphene nanosheets (GA-GNs) has been fabricated via a modified hydrothermal method, followed by a microwave plasma chemical vapor deposition process. The mechanical properties of such hybrid nanostructures, for the first time, were quantitatively measured to demonstrate their superior mechanical robustness with stress and Young's modulus up to 96 kPa and 181.25 kPa, respectively. Finite-element modeling further reveals the mechanical strengthening mechanism with GNs as stiffening ribs layered over thin cellular walls within the GA. Moreover, GA-GNs present excellent electrical conductivity as high as ∼1000 S/m, showing great promise as high-performance supercapacitor electrodes. The as-prepared free-standing and binder-free GA-GN electrode exhibits a high specific capacitance of 245 F g−1 (based on the entire electrode mass) which corresponds to a high areal capacitance of 1.1 F cm−2, desirable rate capability and outstanding cyclic stability with a capacitance retention of 92% over 10000 cycles. To assess their practical functionality, a two-terminal symmetric all-solid-state supercapacitor based on such all-carbon electrodes was fabricated. Such supercapacitor devices exhibited desirable areal capacitance, low internal resistance and outstanding cyclic stability.

    更新日期:2017-11-15
  • Interactions between bacteria and heteroatom-modified nanoporous carbon: The influence of nitrogen and sulfur doping
    Carbon (IF 6.337) Pub Date : 2017-11-15
    Wojciech Kiciński, Mateusz Szala, Tomasz Cłapa, Marcin Syczewski, Andrzej Borkowski

    Heteroatom-doped carbon structures have successfully entered the field of advanced functional materials but their impact on living organisms is still poorly examined. Interactions between typical Gram-negative bacteria Escherichia coli, Gram-positive Bacillus cereus and heteroatom-doped nanoporous carbons are studied in this paper. Four types of carbonaceous materials, that is N-doped, S-doped, S/N-co-doped and undoped carbon gels, are considered. Respirometric measurements, dehydrogenases activity and viability tests were conducted to assess the toxicity of the doped carbons against bacteria. The heteroatom-doped and dopant-free carbon gels do not cause an inhibition of bacterial growth nor a lethal effect. On the contrary, we demonstrate that the doped carbons enhance microbial activity. The adhesion of bacteria to the carbon surface was investigated based on the adsorption studies and biofilm formation. It is demonstrated that the doping of carbons with nitrogen induces surface acidity and hydrophilicity, which in turn significantly enhances the bacteria sorption. Unlike the S-doped or undoped materials, the N-doped carbons are characterized by high bacterial affinity, even when compared to efficient bacteria adsorbents, e.g. active carbon Norit. The results obtained demonstrate that N-containing carbon gels support bacterial proliferation and as such may constitute attractive materials for wastewater treatment technologies as well as bioelectrochemical processes.

    更新日期:2017-11-15
  • Properties of graphene-metal contacts probed by Raman spectroscopy
    Carbon (IF 6.337) Pub Date : 2017-11-15
    Hejun Xu, Xing Wu, Xinming Li, Chen Luo, Fang Liang, Edmond Orignac, Jian Zhang, Junhao Chu

    The high intrinsic carrier mobility of graphene has drawn much attention. However, the high contact resistance between the graphene and metal electrode limits the application of high-speed graphene-based transistors. In this work, we combined both electrical characterization and Raman spectroscopy to study the contact resistance issue in graphene field effect transistor (FET). As FET size scaling down, the graphene-metal contact resistance is found to be a significant contributor to the total resistance. The signature of the graphene/metal bonding with various metal electrodes is probed by using high-resolution Raman spectroscopy. Graphene-metal Raman signals vary on different metal electrodes. This study unearths the properties of the graphene/metal bonding, and paves a way for the investigations into improving the stability and scalability of the graphene-based transistor for future high-speed nanoelectronics.

    更新日期:2017-11-15
  • Synergism between carbon materials and Ni chains in flexible poly(vinylidene fluoride) composite films with high heat dissipation to improve electromagnetic shielding properties
    Carbon (IF 6.337) Pub Date : 2017-11-14
    Biao Zhao, Sai Wang, Chongxiang Zhao, Ruosong Li, S. Mahdi Hamidinejad, Yasamin Kazemi, Chul B. Park

    We prepared poly(vinylidene fluoride) (PVDF)/carbon/Ni-chain composites by dispersing Ni chains, and either carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs) into a PVDF solution. The electrical conductivity and the electromagnetic interference (EMI) shielding properties of the PVDF/CNT/Ni-chain and the PVDF/GNP/Ni-chain composites were increased by increasing the Ni-chain filler content. The electrical conductivity of the PVDF/CNT/10 wt%Ni-chain composite was lower than the PVDF/CNT/6 wt%Ni-chain composite. We attributed this abnormality to the Ni chains having blocked the CNT connections, when there was a high Ni-chain content. Furthermore, the PVDF-based composites' EMI shielding properties were effectively tuned by controlling the films' thicknesses. The total shielding of the PVDF/CNT/6 wt%Ni-chain and the PVDF/GNP/8 wt%Ni-chain composite films increased from 23.6 to 57.3 dB and from 22.7 to 55.8 dB, as their thicknesses were increased from 0.3 mm to 0.6 mm, respectively. The synergetic relationship between the Ni chains and the carbon materials (CNT or GNP), meant that the main EMI shielding mechanisms of the PVDF/carbon/Ni-chain composites had resulted from the absorption process. Moreover, these composites possessed high thermal conductivity, which can convert microwave energy into Joule heating systems. Thus, these PVDF-based composite films can be used to make high-efficiency EMI shielding devices that can rapidly dissipate heat.

    更新日期:2017-11-15
  • Effect of matrix-alloying-element chromium on the microstructure and properties of graphite flakes/copper composites fabricated by hot pressing sintering
    Carbon (IF 6.337) Pub Date : 2017-11-14
    Shubin Ren, Jianhao Chen, Xinbo He, Xuanhui Qu

    Copper matrix composites reinforced with graphite flakes (GFs/Cu) were fabricated by powder hot pressing method and the alloying chromium (Cr) element in powdered form was directly added into the Cu matrix powder to enhance the interfacial bonding between GFs and Cu matrix. Effects of addition of Cr on thermal conductivity (TC), coefficient of thermal expansion (CTE), and bending strength of GFs/Cu composites in X-Y (basal plane of GF) and Z directions were investigated in this study. The results showed that in X-Y direction, the TC of 50 vol.% GFs/Cu composites increased from 560 to 628 W m−1 K−1 after adding 2.0 wt.% Cr, and the bending strength nearly doubled from 53.8 (GF/Cu) to 93 MPa. The CTE in Z direction could be obviously reduced with Cr addition, which dropped gradually from 9.4 to 3.2 ppm K−1 at 150 °C with the increase in content of Cr from 0 to 5.0 wt.%. This improvement in TC, bending strength, and CTE is attributed to the formation of carbide transition layer at the interface between Cu and graphite. The detailed influence of carbide layer on the properties of the composites was thoroughly studied by corresponding evolution of interfacial microstructure with increasing Cr content.

    更新日期:2017-11-14
  • Effect of Ti doping on spin injection and relaxation in few-layer graphene
    Carbon (IF 6.337) Pub Date : 2017-11-12
    Bing Zhao, Xiaoguang Xu, Le Wang, Juan Li, Ziyu Zhang, Pengfei Liu, Qi Liu, Zhicheng Wang, Yong Jiang

    Abstract We demonstrate the spin filtering effect in Co|MgO|TiOx|graphene junctions and a large negative spin polarization in graphene at room temperature. By systematically introducing Ti (TiOx) clusters to the exfoliated few-layer graphene, we confirm that the Ti (TiOx) clusters will increase the charged impurity scattering and lead to a decreased momentum scattering time and an abnormal Gaussian broadening effect. However, the spin relaxation mechanism is not significantly affected, indicating that the spin relaxation mechanism of graphene will not be affected by the atomic-scale Ti (TiOx) clusters induced charged impurity scattering.

    更新日期:2017-11-13
  • Root-like porous carbon nanofibers with high sulfur loading enabling superior areal capacity of lithium sulfur batteries
    Carbon (IF 6.337) Pub Date : 2017-11-11
    Xiaohui Zhao, Miso Kim, Ying Liu, Hyo-Jun Ahn, Ki-Won Kim, Kwon-Koo Cho, Jou-Hyeon Ahn

    A hierarchically porous carbon nanofiber (HPCNF) material was prepared by a facile electrospinning method, with polyvinylpyrrolidone (PVP) as the carbon source and silica formed in-situ as the template. The carbon nanofibers showed a well-designed pore structure: centered macropores are surrounded by a denser cycle consisting of micro-/mesopores near the surface. Sulfur was encapsulated into the pores by solution penetration, followed by a melt diffusion method to generate a flexible sulfur/HPCNF (S/HPCNF) cloth as the binder-free cathode in lithium sulfur (Li-S) batteries. The HPCNF carbon with multi-scaled pores acts as an efficient host for large amounts of sulfur, and accommodates the associated volume expansion during electrochemical cycling. Moreover, the hierarchical architecture significantly reduces the escape of polysulfides during the cycling. The unique material allowed sulfur loading of 2.2–12.1 mg cm−2, and exhibited a high sulfur utilization of more than 80% with high areal capacity of 11.3 mAh cm−2, demonstrating that S/HPCNF is a promising cathode material for Li-S batteries of high energy density.

    更新日期:2017-11-13
  • Adhesive transfer at copper/diamond interface and adhesion reduction mechanism with fluorine passivation: A first-principles study
    Carbon (IF 6.337) Pub Date : 2017-11-11
    Zengjia Liu, Shaoxian Zheng, Zhibin Lu, Jibin Pu, Guangan Zhang

    Tribological behavior of Cu is peculiar among soft metal when it rubs on diamond flat in experiments, and passivating element F and H at Cu/diamond interface can affect mechanical properties and even tribological characteristics as well, related special adhesive transfer (fracture location) and adhesion tuning mechanism at Cu/diamond interface remain obscure. Here, we investigate the interfacial structure change, electronic and mechanical properties of Cu/diamond and interface with fully F passivation (Cu/diamond:F) through first-principles calculations. The study shows that Cu(111)/diamond(111) interface exhibits the special phenomenon of adhesive transfer (different cleavage location and interfacial strength under applied load) due to adhesion, and this contribute to different frictional properties among soft metal. The effect on mechanical properties of F at Cu/diamond interface is studied systematically, passivation of fluorine on diamond surface reduces work of separation of the interface significantly, from 3.64 to 0.02 J/m2. Combining with kinetic analysis, we gain that fluorine might be a kind of promising adhesion-reducing element at interface and improve related tribological characteristics of Cu(111)/diamond(111) system. The results of this study benefit the understanding of different tribological properties of Cu/diamond system, adhesion reduction mechanism of fluorine at interface and its effect on tribological behavior at atomic scale.

    更新日期:2017-11-13
  • Carbon dot capped gold nanoflowers for electrochemiluminescent aptasensor of thrombin
    Carbon (IF 6.337) Pub Date : 2017-11-10
    Xu You, Wei Lin, Huan Wu, Yongqiang Dong, Yuwu Chi

    A simple method has been developed to synthesize carbon dot capped gold nanoflower (CD/AuNF) nanohybrids. In principle, anodic electrochemiluminescent (ECL) carbon dots (CDs) with a lot of reductive functional groups were used to react with oxidative hydrogen tetrachloroaurate trihydrate in the presence of trisodium citrate. The obtained globular CD/AuNF nanohybrids had uniform sizes of 50–60 nm. The CD/AuNF nanohybrids were composed of gold nanoparticle aggregates in the centers and CDs on the surfaces. The easy self-assembly with some bio-molecules of AuNFs and the unique ECL activities of the CDs, made the obtained CD/AuNF nanohybrids promising in biosensing. For instance, a novel ECL aptasensor for thrombin (TB) detection has been developed based on the CD/AuNF nanohybrids. The aptasensor showed good selectivity towards TB. Furthermore, it presented a wide linear response range from 0.5 nM to 40 nM and a low detection limit (S/N = 3) of 0.08 nM.

    更新日期:2017-11-13
  • Instabilities in carbon nanocone stacks
    Carbon (IF 6.337) Pub Date : 2017-11-09
    Arindam Raj, Aningi Mokhalingam, Shakti S. Gupta

    Possessing remarkable electronic, mechanical and optical properties, pristine single-walled carbon nanocones are envisioned here to be pulled-out co-axially from a nanocone stack. The process is simulated using molecular mechanics (MM) and dynamics (MD) employing MM3 and REBO + LJ potentials, respectively. During pulling-out, rim of the lowermost cone is constrained while the tip of the outermost cone is displaced axially from its equilibrium, quasi-statically in case of MM and by prescribing velocity of 0.1 Å/pico-sec in case of MD. During pulling-out, at a critical distance, the top cone abruptly breaks the axial symmetry with its wall deforming considerably outward. The source of this instability is building-up of compressive circumferential strain in wall with increasing displacement; a competition between stretching and van der Waal's energy terms of the system. Interestingly, during reversal of the pulling-out process, the system is found to trace a different equilibrium path. Further, in a few-walled CNCs if the tip of the top-most cone is compressed from its equilibrium position, the stack inverts completely by breaking axial symmetry aided by snap-through buckling in segments of the periphery. Irrespective of apex angle, hydrogen passivation, temperature and potential used, the aforementioned observations are found to be intrinsic to the system.

    更新日期:2017-11-10
  • Phosphorus and sulfur codoped g-C3N4 as an efficient metal-free photocatalyst
    Carbon (IF 6.337) Pub Date : 2017-11-09
    Chechia Hu, Wei-Zeng Hung, Mao-Sheng Wang, Pei-Ju Lu

    In this study, the photocatalytic activity of graphitic carbon nitride (g-C3N4) was improved by codoping S and P on the interstitial and carbon sites of its aromatic heptazine units, respectively. X-ray photoelectron spectra and X-ray diffraction measurements demonstrated that P covalently bonded with N because of the substitution of C with P and that S was located at the interstitial sites with relatively weak bonding with N in the heptazine units of the g-C3N4 structure. The samples of g-C3N4 codoped with P and S (PSCN) displayed low photoluminescence emission intensity, suggesting suppressed recombination of photogenerated charges, and thus increased photocatalytic degradation activity. In particular, PC (C replaced by P) and Si (interstitial doping of S) doping on g-C3N4 was prominently able to enhance the charge transfer through the N<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">S<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">N<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">C<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">N<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">P pathway to cross the heptazine units for the photocatalytic reaction, making PSCN a highly visible-active and effective metal-free photocatalyst.

    更新日期:2017-11-10
  • Metal-organic framework derived nanoporous carbon/Co3O4 composite electrode as a sensing platform for the determination of glucose and high-performance supercapacitor
    Carbon (IF 6.337) Pub Date : 2017-11-08
    Yuvaraj Haldorai, Sang Rak Choe, Yun Suk Huh, Young-Kyu Han

    Here, we demonstrate the controlled synthesis of nanoporous carbon and cobalt oxide (NPC–Co3O4) composite from a single precursor source zeolitic imidazolate framework-67, which leads to some new interesting electrochemical properties. The composite shows an outstanding electrochemical performance for measuring the oxidation of glucose in alkaline solution. The differential pulse voltammetric response of the NPC–Co3O4 composite electrode for the sensing of glucose exhibits a linear relation with the concentration range of 5 × 10-12–2.05 × 10-10 M and a low detection limit of 2 × 10-12 M. The fabricated sensor shows high sensitivity, reliable reproducibility, and good selectivity. The sensor, when used for the direct determination of glucose in blood serum samples, shows good recovery (98.5–101.0%), suggesting its feasibility for biomedical applications. In addition, in a given potential range of 0 to 1 V, the composite exhibits a high capacitance (885 F g-1 at a current density of 2.5 A g-1) and long cycle life (∼94% capacitance retention after 10,000 cycles).

    更新日期:2017-11-10
  • Investigation of the microstructure change due to phase transition in nanosecond pulsed laser processing of diamond
    Carbon (IF 6.337) Pub Date : 2017-11-08
    G.B.J. Cadot, K. Thomas, J.P. Best, A.A. Taylor, J. Michler, D.A. Axinte, J. Billingham

    Experiments and theory are employed to investigate the thermal damage induced by infra-red nanosecond pulses in atmospheric air into a boron-doped diamond target. Micro-Raman spectroscopy, Transmission Electron Microscopy (TEM) analysis and surface topography measurement are used to investigate the carbon phase created during the rapid heating and cooling of diamond, as well as the amount of material ablated during the interaction with the laser. The analysis provides insight into the phenomena occurring for the rapid graphitisation of diamond during pulsed laser ablation, and also the microstructural disorder induced by the thermal and pressure fields at level of energy below and above the melting threshold. To support the understanding from the experimental investigations, a model is constructed for the graphitisation and ablation of diamond coupled with a collisional radiative model for the plasma evolution. The one-dimensional system of non-linear equations that model the physical processes provides an insight into the dynamics of the phenomena leading to the creation of disturbed graphite during pulsed laser ablation. Furthermore, the model helps to identify the main physical processes leading to the creation of disordered graphite, suggesting that plasma evolution does not follow a Boltzmann-Saha equilibrium and that radiative recombination is a main factor influencing the thermal evolution of the plasma and the diamond target. Finally, a good agreement with experimental findings is obtained, particularly in regards to the amount of material ablated, the thickness of the graphite layer and the processes leading to the melting of graphite.

    更新日期:2017-11-10
  • Understanding the mechanical characteristics of nanotwinned diamond by atomistic simulations
    Carbon (IF 6.337) Pub Date : 2017-11-08
    Ligang Sun, Xiaoqiao He, Jian Lu

    As is known to all, diamond is the hardest natural substance. The synthesis of harder materials than the natural diamond is very favorable but challenging. It has been found that the introduction of nanotwinned (NT) structure into diamond could be an effective approach to improve the hardness of diamond. Nevertheless, the fundamental understanding of the strengthening characteristics by NT structure is still ambiguous. In this work, we unveil the effect of NT structure on the deformation mechanism and mechanical properties of diamond at the atomic scale by virtue of atomistic simulations. Interestingly, the hardness measured by nanoindentation shows a positive correlation to the twin spacing instead of the inverse Hall-Petch effect extensively discovered in many traditional metal materials. However, it is not the smallest twin spacing achieving the highest tensile strength, indicating the existence of twin-spacing-induced inverse Hall-Petch effect in NT diamond during tensile deformation. The specific deformation mechanisms are investigated which are capable of providing an explicit explanation for the observed mechanical characteristics.

    更新日期:2017-11-10
  • Insights on the mechanism of water-alcohol separation in multilayer graphene oxide membranes: Entropic versus enthalpic factors
    Carbon (IF 6.337) Pub Date : 2017-11-07
    Daiane Damasceno Borges, Cristiano F. Woellner, Pedro A.S. Autreto, Douglas S. Galvao

    Experimental evidence has shown that graphene oxide (GO) can be impermeable to liquids, vapors and gases, while it allows a fast permeation of water molecules. Theoretical studies to understand the filtration mechanisms come mostly from water desalination, while very few works have been dedicated to alcohol dehydration. In this work, we have investigated the molecular level mechanism underlying the alcohol/water separation inside GO membranes. A series of Molecular Dynamics and Grand-Canonical Monte Carlo simulations were carried out to probe the ethanol/water and methanol/water separation through GO membranes composed of multiple layered graphene-based films with different interlayer distance values and number of oxygen-containing functional groups. Our results show that the size exclusion and membrane affinities are not sufficient to explain the selectivity. Besides that, the favorable water molecular arrangement inside GO 2D-channels forming a robust H-bond network and the fast water permeation are crucial for an effective separation mechanism. In other words, the separation phenomenon is not only governed by membrane affinities (enthalpic mechanisms) but mainly by the geometry and size factors (entropic mechanisms). Our findings are consistent with the available experimental data and contribute to clarify important aspects of the separation behavior of confined alcohol/water in GO membranes.

    更新日期:2017-11-10
  • Raman spectroscopy revealing noble gas adsorption on single-walled carbon nanotube bundles
    Carbon (IF 6.337) Pub Date : 2017-11-07
    Renato Cunha, Ricardo Paupitz, Kichul Yoon, Adri C.T. Van Duin, Ana Laura Elías, Victor Carozo, Archi Dasgupta, Kazunori Fujisawa, Néstor Perea Lopez, Paulo T. Araujo, Mauricio Terrones

    The interaction of the noble atoms (Ar and Xe) with single-walled carbon nanotube (SWCNT) bundles are investigated using Raman spectroscopy in conjunction with computational modeling known as ReaxFF force field. SWCNT bundles were deposited on transmission electron microscopy (TEM) grids, and different noble gases were adsorbed onto the nanotubes at 20 K. Raman spectra acquired show significant frequency blueshifts of the radial breathing mode (RBM), G- and G′(or 2D)-bands due to gas solidification within the external groove sites (free spaces between the tubes in the bundle) and external surfaces of the bundles. This solid shell formed by the adsorbed gases contributes with a hydrostatic pressure to the system. We show from Raman measurements that the frequencies found after gas adsorption exhibit almost the same shifts indicating that the interactions between SWCNTs bundles and the gases (Ar or Xe) are nearly identical.

    更新日期:2017-11-10
  • Monolayer graphene doping and strain dynamics induced by thermal treatments in controlled atmosphere
    Carbon (IF 6.337) Pub Date : 2017-11-06
    A. Armano, G. Buscarino, M. Cannas, F.M. Gelardi, F. Giannazzo, E. Schilirò, S. Agnello

    Time dynamics of doping and strain induced in single layer graphene by thermal treatments up to 300°C in vacuum, nitrogen, carbon dioxide and oxygen controlled atmosphere are deeply studied by Raman spectroscopy and they are compared with its morphological evolution investigated by Atomic Force Microscopy. The reaction dynamics in oxygen treatments is determined down to a time scale of few minutes as well as that of dedoping process made by water vapor treatment. The interplay of strain modification and doping effects is separated. The strain is clarified to be strongly influenced by the cooling time. The doping removal is dominated by the water vapor, showing that the concentration of molecular water in gas phase governs the process rate. The opportune choice of heating/cooling and atmosphere enables to tune selectively the strain or doping.

    更新日期:2017-11-10
  • Electrosprayed silicon-embedded porous carbon microspheres as lithium-ion battery anodes with exceptional rate capacities
    Carbon (IF 6.337) Pub Date : 2017-11-06
    Gemeng Liang, Xianying Qin, Jinshuo Zou, Laiyan Luo, Yunzhe Wang, Mengyao Wu, Hua Zhu, Guohua Chen, Feiyu Kang, Baohua Li

    Silicon-embedded porous carbon microspheres with an exceptional conductive framework for ions and electrons were obtained by electrospraying a mixed polymer solution of polystyrene and polyvinylpyrrolidone, containing silicon nanoparticles, carbon nanotubes and carbon blacks, and subsequent heat treatment. In the composite microspheres, silicon particles were embedded in the porous carbon framework composed of interwoven carbon nanotubes, filled carbon blacks and interconnected amorphous carbon derived from polymers. The cage-like porous carbon microspheres could not only accommodate the volume expansion of silicon but also ensure a robust electrical contact, fast transport for electrons and ions. Therefore, the silicon/carbon anode exhibits a high capacity of 1325 mAh g−1 at 0.2 A g−1 after 60 cycles and superior rate capability with a capacity of 925 mAh g−1 at a large current density of 5 A g−1.

    更新日期:2017-11-10
  • Engineering graphene properties by modulated plasma treatments
    Carbon (IF 6.337) Pub Date : 2017-11-06
    Giuseppe Valerio Bianco, Alberto Sacchetti, Chiara Ingrosso, Maria Michela Giangregorio, Maria Losurdo, Pio Capezzuto, Giovanni Bruno

    We demonstrate modulated H2 and O2 plasma treatments as an effective methodology for controlled chemical functionalization by hydrogen and oxygen atoms of single- and multi-layer chemical vapor deposition (CVD) graphene aiming at engineering material properties. The effects of the functionalization degree on the optical and transport properties of graphene are discussed with a twofold aim of (i) providing reproducible experimental protocols for tailoring graphene properties, and of (ii) providing insights into the chemical mechanisms involved in the plasma-processing of graphene with hydrogen and oxygen atoms.An unprecedented control over the graphene functionalization by hydrogen atoms is demonstrated together with the fine tuning of multi-layer graphene resistivity as well as the transition from metallic to semiconducting behavior with a gap opening. The interaction of oxygen atoms with multilayer graphene provides a strong modification of surface wettability without significant change in conductivity, thus suggesting that oxidation effects are mainly confined on the outmost graphene. Moreover, the air exposure of graphene oxidized by plasma treatment results in peculiar chemical mechanisms with important effect on the transport properties of the material. Finally, we investigate the restoration of graphene from graphene oxide by modulated hydrogen plasma.

    更新日期:2017-11-10
  • Visible light laser-induced graphene from phenolic resin: A new approach for directly writing graphene-based electrochemical devices on various substrates
    Carbon (IF 6.337) Pub Date : 2017-11-06
    Zhuchan Zhang, Mengmeng Song, Junxing Hao, Kangbing Wu, Chunya Li, Chengguo Hu

    The cost-effective construction of self-designed conductive graphene patterns on desired substrates is crucial to the fabrication of graphene-based electrochemical devices. Here, we report a new approach for the scalable construction of laser-induced graphene (LIG) patterns on diverse substrates by using phenolic resin (PR) as the precursor. The PR-based LIG, which was produced with smart and inexpensive 405 nm semiconductor lasers under ambient conditions, possesses several interesting properties, e.g., 3D porous structures, low resistance (∼44 Ω/sq), good mechanical property and a wide range of applicable substrates, e.g., polymer films, glass slides, metal foils, ceramic plates and plant leaves. The efficient absorption of laser light by PR coatings themselves or dopants such as metal salts and organic dyes is demonstrated critical to the formation of PR-based LIG by visible light lasers. Based on this technique, self-designed and highly conductive graphene arrays can be easily constructed on various substrates to fabricate all-carbon supercapacitors and electrochemical glucose biosensors. The unique properties of PR materials, including easy synthesis, tunable structure and composition, excellent film-formation ability and extremely low cost, thus foresee the promising applications of PR-based LIG in electrochemical fields.

    更新日期:2017-11-10
  • Robust, hydrophilic graphene/cellulose nanocrystal fiber-based electrode with high capacitive performance and conductivity
    Carbon (IF 6.337) Pub Date : 2017-11-06
    Guoyin Chen, Tao Chen, Kai Hou, Wujun Ma, Mike Tebyetekerwa, Yanhua Cheng, Wei Weng, Meifang Zhu

    Graphene fiber-based electrodes for supercapacitors are promising candidates for wearable energy storage. Their main limitation, although, is the low electrochemical performance caused by the restacking of graphene sheets and their hydrophobicity to electrolytes. Incorporation of nanofillers into graphene is an efficient way to overcome the challenges, however, often leading to a sever deterioration in their mechanical property and/or conductivity, thus significantly influences the practical applications and rate performance of the device. Herein, an approach of fabricating hybrid fibers from graphene oxide (GO) and cellulose nanocrystal (CNC) via non-liquid-crystal spinning and followed by chemical reduction is presented to collectively work around the problems. The resultant hybrid GO/CNC fibers demonstrated a high capacitive performance, enhanced mechanical property, and improved hydrophilicity simultaneously. Furthermore, the conductivity kept at a high value. Sample with a GO/CNC weight ratio of 100/20 possessed a high capacitance of 208.2 F cm−3, a strength of 199.8 MPa, a contact angle of 63.3°, and conductivity of 64.7 S cm−1. Moreover, the supercapacitor assembled from this fiber exhibited a high energy density and power density (5.1 mW h cm−3 and 496.4 mW cm−3), excellent flexibility and bending stability, which has a great potential for using as flexible power storage.

    更新日期:2017-11-10
  • Water adsorption on the diamond (111) surfaces: An ab initio study
    Carbon (IF 6.337) Pub Date : 2017-11-06
    Giacomo Levita, Seiji Kajita, Maria Clelia Righi

    The physical and chemical adsorptions of water at the (1 × 1) and (2 × 1)-reconstructed C(111) surfaces are investigated by means of first principles calculations and compared to hydrogen adsorption. The study aims at filling a gap of knowledge about the interaction of water with the most stable diamond surface. The calculated reaction energies and barriers indicate that the Pandey-reconstructed surface is almost inert towards water and hydrogen chemisorption in comparison with the unreconstructed surface and other low-index diamond surfaces. We also show that by increasing the amount of chemisorbed hydroxyl or hydrogen groups the stability of the Pandey reconstruction is progressively reduced with respect to the unreconstructed (111) surface, which becomes energetically more favourable above about 40% of adsorbate coverage. Our results provide a microscopic description of diamond surface passivation, which is very important for controlling macroscale phenomena, such as the friction reduction of diamond coatings in humid environments.

    更新日期:2017-11-10
  • Investigation of dispersion behavior of GO modified by different water reducing agents in cement pore solution
    Carbon (IF 6.337) Pub Date : 2017-11-05
    Li Zhao, Xinli Guo, Yuanyuan Liu, Chuang Ge, Zhongtao Chen, Liping Guo, Xin Shu, Jiaping Liu
    更新日期:2017-11-05
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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