2011 Vol. 26, No. 01

Preface
CHENG Hui-ming, YANG Quan-hong, ZHI Lin-jie
2011, 26(01)
Abstract(1940) PDF(1378)
Abstract:
       For long, the elemental Carbon had been considered to have only four allotropes: diamond, graphite, amorphous carbon and carbyne. Twenty-five years on from the discovery of C60, the development of sp2-hybridized carbons have renewed our knowledge about Carbon by continuously presenting three new allotropes: zero-dimensional C60 of perfect symmetry (fullerene, 1985), the smallest one-dimensional material (carbon nanotube, 1991) and the thinnest two-dimensional material (graphene, 2004). More importantly, these novel carbons have demonstrated many intriguing and unexpected properties and promoted the development of nanomaterials and nanotechnology. Since the rediscovery and rise of graphene in 2004, such a thin sheet-like carbon has demonstrated excellent electrical, optical, thermal, mechanical, chemical and electrochemical properties and shown great potentials in many application areas such as nanoelectronics, energy storage, membrane devices and composite materials. In 2010, only six years after the mechanically-cleaved graphene was reported to be of intriguing electrical properties by Andrei Geim and Konstantin Novoselov, the two scientists was awarded Nobel Prize in Phy~sics.

    This special issue reports the latest research advances of graphene and other novel carbon nanostructures, including 2 Highlights (short review), 1 Review, 11 research articles. The two Highlights give comments on the discovery, development trend and energy storage application of graphene; the Review presents an overview of chemical vapor deposition method to prepare high quality graphene; the 8 research papers report the latest results of graphene research with several “hot” topics: preparation and characterization, assembly, modification and applications; the other 3 research papers involve in latest applications of other novel carbon nanostructures, including field emission property of carbon nanotubes with a sharp tip, adsorption of heave metal ions by nanotubes and photocatalytic properties of carbon coated titania.
  Many scientific comments have predicted that the discovery of new carbon allotropes does not come to an end after the discovery of fullerene, the synthesis of carbon nanotubes and the rediscovery of graphene. Scientists are continuing to unfold the exciting carbon family, and for example, graphane and graphdiyne are the most recently synthesized novel carbons. There will be a long way for us to fully understand the properties and realize the large-scale applications of these novel carbons, so continuous efforts by scientists and engineers are highly required to explore the exciting Carbon…

Dreams may come: from fullerene, carbon nanotube to graphene
YANG Quan-hong
2011, 26(01): 1-4.
Abstract(4872) PDF(3394)
Abstract:
The past twenty-five years have seen the discovery of three new carbon allotropes: fullerene, carbon nanotubes and graphene. Graphene, with an ideal two-dimensional structure, demonstrates many unique physical and chemical properties. This short review presents different “faces” of graphene in the eyes of physicists and chemists. For physicists, graphene means the thinnest platform to reveal new or unexpected properties of materials, while, for chemists, graphene acts as a basic and starting unit for desired structures with tuned properties. Thermal chemical exfoliation under mild and well-controllable conditions is highlighted as a feasible solution for the realization of mass-production and early applications of graphene-based materials.
Graphene based electrode materials for lithium-ion batteries: energy storage properties and prospects
ZHI Lin-jie, FANG Yan, KANG Fei-yu
2011, 26(01): 5-8.
Abstract(3135) PDF(3675)
Abstract:
Graphene is a rapidly rising star in materials science because of its two-dimensional structure, superior properties, and promising applications. Recent progress on graphene-based electrode materials for high performance lithium ion batteries (LIBs) has been highlighted. The relationship between the graphene structure, its electrochemical performance and strategies for tuning its functions are discussed. Graphene-based nanomaterial is believed to be an attractive electrode material in LIBs, particularly for the development of batteries with high-energy density and high-power density.
High-performance self-assembled graphene hydrogels prepared by chemical reduction of graphene oxide
SHENG Kai-xuan, XU Yu-xi, LI Chun, SHI Gao-quan
2011, 26(01): 9-15. doi: 1007-8827(2011)01-0009-07
Abstract(4277) PDF(2700)
Abstract:
Three-dimensional self-assembled graphene hydrogels (SGHs) have been fabricated by chemical reduction of graphene oxide (GO) with sodium ascorbate. The SGHs were characterized by scanning electron microscopy, rheological tests, electrical conductivity measurements, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. Results indicate that the reduction of GO promotes the assembly of graphene sheets. The SGHs are electrically conductive (1S · m-1) and mechanically strong and exhibit excellent electrochemical performance. In 1mol · L-1 aqueous solution of H2SO4, the specific capacitance of SGHs was measured to be about 240F · g-1 at a discharge current density of 1.2A · g-1.
“Green&rdquo|reduction of graphene oxide to graphene by sodium citrate
WAN Wu-bo| ZHAO Zong-bin| HU Han| ZHOU Quan| FAN Yan-ru| QIU Jie-shan
2011, 26(01): 16-20.
Abstract(3349) PDF(4829)
Abstract:
Graphene was produced from graphene oxide using sodium citrate as the reducing agent under mild conditions. The products were characterized by scanning electron microscopy, X-ray diffraction, ultraviolet visible absorption spectroscopy and Fourier transform infrared spectrometry. Results indicate that the electrical conductivity of graphene oxide was increased by over three orders of magnitude after reduction with sodium citrate, and the obtained graphene showed nonlinear I-V curves.
Preparation of graphene nanosheets through detonation
WANG Can, ZHAN Liang, QIAO Wen-ming, LING Li-cheng
2011, 26(01): 21-25. doi: 10.1016/S1872-5805(11)60063-2
Abstract(3141) PDF(2018)
Abstract:
Graphene nanosheets were synthesized using graphite oxide as a precursor by detonation. The composition, and structure of graphene nanosheets were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, selected area electron diffraction, and Raman spectroscopy. Results indicated that the as-prepared material was transparent and wrinkled, and comprised 2-5 graphenes with a highly crystalline structure. The exfoliation and reduction of graphite oxide to graphene nanosheets was induced by the self-generated thermal energy and shockwave of detonation.
Preparation and characterization of graphene and few-layer graphene
FENG Ying, HUANG Shi-hua, KANG Kai, DUAN Xiao-xia
2011, 26(01): 26-30.
Abstract(3222) PDF(5097)
Abstract:
Few-layer graphene was prepared from highly oriented pyrolytic graphite by micromechanical cleavage and transferred to the silicaon coated with silicon dioxide (SiO2/Si). The thickness of graphene on the SiO2/Si support was investigated by color and contrast variations under an optical microscope. Atomic force microscopy and Raman spectroscopy were used to determine the number of layers. Results show that a monolayer, double layers and multiple layers of graphene were prepared. The optical microscope images can give a satisfactory identification of the graphene thickness on SiO2/Si. In the Raman spectrum the 2D band is narrower and G band is weaker for double layers than that for multiple layers. Chemical vapor deposition was also used to grow large area (~cm2) graphene. However, micromechanical cleavage is a more simple method to prepare graphene.
High yield production of graphene and its improved property in detecting heavy metal ions
WANG Bin, CHANG Yan-hong, ZHI Lin-jie
2011, 26(01): 31-35. doi: 10.1016/S1872-5805(11)60064-4
Abstract(2674) PDF(1916)
Abstract:
A simple and economical approach to produce graphene nanosheets (GNSs) in quantity based on the thermal expansion of graphite oxide (GO) powder has been developed, and the as-prepared GNS was further used for the detection of different trace heavy metal ions including Cu2+, Pb2+, and Cd2+. The few-layer GNSs with defects and residual —OH groups were shown to be particularly well suited for the determination of metal ions in the liquid phase using an electrochemical method, in which a remarkably low detection limit of 10-11mol/L for Pb2+ was achieved. The high-yield production technique of GNSs combined with the high sensitivity for the detection of metal ions could promote the development of the industrial manufacture of graphene-based nanosensors.
High-concentration graphene aqueous suspension and a membrane self-assembled at the liquid-air interface
WEI Wei, LU Wei, YANG Quan-hong
2011, 26(01): 36-40.
Abstract(3137) PDF(2966)
Abstract:
Graphene dispersion in different surfactant aqueous solutions was investigated by absorbance measurements. Polyvinylpyrrolidone (PVP) is an excellent low cost and "green" dispersion agent. By increasing the concentration of the PVP solution, the graphene suspension concentration can reach ~1.3mg/mL, which is higher than those reported previously. This high-concentration graphene dispersion will play an important role in the application of graphene-based materials. A graphene-based membrane was assembled by the evaporation of a PVP-stabilized graphene suspension at the liquid-air interface. The free-standing, self-assembled membrane with a flat surface and ordered structure could find great practical value in a wide range of applications.
The effect of thermal treatment at low temperatures on graphene oxide films
LIU Yan-zhen, LI Yong-feng, YANG Yong-gang, WEN Yue-fang, WANG Mao-zhang
2011, 26(01): 41-45.
Abstract(2792) PDF(2881)
Abstract:
Graphite oxide was synthesized by the Hummers and Offemann method, followed by ultrasonic delamination in water to produce a stable hydrosol of graphene oxide sheets. The graphene oxide films were prepared from the hydrosol by a vacuum-assisted self-assembly technique. These films were further treated in a vacuum oven at different temperatures, and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. Results indicate that the graphene oxide films exhibit good electrical conductivity up to 527S/m after the thermal treatment at temperatures from 130 to 200℃. This environmentally friendly and easy approach is promising for the large scale preparation of graphene oxide films with no need of hydrazine and other toxic chemicals.
Effect of vacancies and Si-dopant on In adsorption on graphene
DAI Xian-qi, SUN Yong-can, ZHAO Jian-hua, WEI Shu-yi
2011, 26(01): 46-51.
Abstract(2581) PDF(1629)
Abstract:
First-principles calculations were carried out to study the effect of vacancies and Si-dopant on indium (In) adsorption on graphene. It is demonstrated that a vacancy or a Si-dopant strengthens In adsorption on graphene. The effect of the vacancy is greater at low In coverage than that of Si impurity, owing to the fact that the vacancy provides more dangling bonds for In adsorption, which strengthens the interaction between the In atom and graphene. However, the Si impurity affects In adsorption on graphene stronger than that the vacancy does at high In coverage (i.e. 1/6).
Synthesis and field emission property of carbon nanotubes with sharp tips
ZHANG Yan-li, ZHANG Li-li, HOU Peng-xiang, JIANG Hua, LIU Chang
2011, 26(01): 52-56. doi: 10.1016/S1872-5805(11)60065-6
Abstract(2223) PDF(1257)
Abstract:
Carbon nanotubes (CNTs) with sharp tips were synthesized by a hydrogen arc discharge method. Three unusual morphologies, i.e., a cone-shaped tip, a suddenly-shrinking tip, and a pencil point-like tip were observed. These novel tip structures are considered to be related to the addition of a small amount of silicon powder in the raw material, which may introduce structural defects in the CNTs. The field emission property of the sharp-tip CNTs was investigated, and a low threshold electric field of 3.75V/m, a high field emission current density of ~1.6×105A/cm2, and a good emission stability were demonstrated. The superior field emission performance of the CNTs can be attributed to their good crystallinity and unique tip structures.
Characterization and use of functionalized carbon nanotubes for the adsorption of heavy metal anions
XU Yi-jun, Rosa Arrigo, LIU Xi, SU Dang-sheng
2011, 26(01): 57-62. doi: 10.1016/S1872-5805(11)60066-8
Abstract(2422) PDF(1646)
Abstract:
Carbon nanotubes (CNTs) have been chemically functionalized with various oxygen-containing surface groups. The feature of abundant oxygen-containing surface functional groups on the functionalized CNTs is characterized by X-ray photoelectron spectroscopy and temperature-programmed desorption analyslis. Results indicate that the functionalized CNTs have a superior adsorption capacity toward anionic chromate CrO42-, a typical toxic heavy metal ion in waste water, as compared with the unmodified ones. The excellent adsorption ability of CrO42- is attributed to the interaction of CrO42- with the surface oxygen-containing functional groups on the modified CNTs. The functionalized CNTs can be potentially used as an alternatively viable and promising adsorbent for the removal of heavy metal anions in waste water.
Carbon-coated TiO2 composites for the photocatalytic degradation of low concentration benzene
ZHANG Jiang, HUANG Zheng-hong, XU Yong, KANG Fei-yu
2011, 26(01): 63-70. doi: 10.1016/S1872-5805(11)60067-X
Abstract(2014) PDF(1447)
Abstract:
Carbon-coated TiO2 was synthesized by mixing TiO2 powders and polyethylene glycol, followed by heat treatment in nitrogen atmosphere. All samples were characterized by powder X-ray diffraction, UV diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, and nitrogen adsorption. The photocatalytic activity of carbon-coated TiO2 for benzene degradation was investigated with a benzene concentration of ~1.2×10-5. Results showed that the residual carbon content was influenced greatly by heat treatment temperature (HTT) and the amount of PEG, which decreased and increased with increasing the temperature and the amount of PEG, respectively. The crystallinity of TiO2 was improved when the HTT increased. However, the carbon residue had an inhibition effect on the crystal growth of TiO2. The carbon-coated anatase samples were shown to exhibit higher photocatalytic activities than the pristine TiO2 because of the adsorption enrichment of benzene by carbon around the anatase particles and of the effective charge separation due to the electronic conduction of carbon. Another important factor affecting photocatalytic activity was the crystallinity of the anatase phase. High photocatalytic activity for benzene requires a balance between the carbon content and the anatase crystalline structure.
Preparation of graphene by chemical vapor deposition
REN Wen-cai, GAO Li-bo, MA Lai-peng, CHENG Hui-ming
2011, 26(01): 71-80.
Abstract(3355) PDF(6284)
Abstract:
Chemical vapor deposition (CVD) is an effective way for the preparation of graphene with large area and high quality. In this review, the mechanism and characteristics of the four main preparation methods of graphene are briefly introduced, including micromechanical cleavage, chemical exfoliation, SiC epitaxial growth and CVD. The recent advances in the CVD growth of graphene and the related transfer techniques in terms of structure control, quality improvement and large area graphene synthesis were discussed. Other possible methods for the CVD growth of graphene were analyzed including the synthesis and nondestructive transfer of large area single crystalline graphene, graphene nanoribbons and graphene macrostructures.