Study on ultrasound-assisted liquid-phase exfoliation for preparing graphene-like molybdenum disulfide nanosheets

Nanomaterials with graphene-like structures have many excellent properties different from bulk materials and have become one of the most popular international frontiers in recent years. In this paper, graphene-like molybdenum disulfide materials are prepared by ultrasonic exfoliation method assisted with 1-Dodecanethiol. Double solvent ultrasonic exfoliation is realized by introducing chloroform. In addition, the optimal preparation conditions for the preparation of graphene-based molybdenum disulfide are investigated from the aspects of ultrasonic processing time and volume ratio of 1-Dodecanethiol and chloroform. Ultrasonic cleaning instrument is used in the experiment, it’s type is KQ3200E (40KHz, 150 W). Results show that the prepared graphene-like molybdenum disulfide has the highest concentration when the volume ratios of 1-Dodecanethiol and chloroform is 1:1 and ultrasonic processing time is 12 h. The dispersion of graphene-like molybdenum disulfide in low-boiling organic solvents, such as chloroform, tetrahydrofuran (THF), isopropanol (IPA), acetone, acetonitrile (CH₃CN) and ethanol, is realized by solvent exchange method. Characterized by transmission electron microscopy, a relatively thin sheet material is obtained. In addition, the latest methods for preparing graphene-like molybdenum disulfide nanosheet are discussed in view of micromechanical exfoliation, lithium ion intercalation, chemical vapor deposition and chemical synthesis, the advantages and limitations of various preparation methods are compared, the applications of graphene-like molybdenum disulfide nanosheets are also investigated.     

催化剂对类石墨烯纳米片结构和发光性能的影响

利用热丝化学气相沉积在沉积有碳点和金催化剂层的Si衬底上制备了类石墨烯纳米片。分别用扫描电子显微镜、透射电子显微镜、显微Raman光谱仪、傅立叶变换红外光谱仪、X光电子谱仪和Ramalog系统对它的结构、组成和发光性能进行了研究。结果表明碳点和金引起了类石墨烯纳米片厚度和缺陷的变化,进而导致了发光带的漂移和发光强度的改变。根据表征结果,分析了类石墨烯纳米片结构的变化引起发光性能改变的原因。     

Neutron scattering study of reduced graphene oxide of natural origin

This paper presents a direct confirmation of graphene-like configuration and first suggests the chemical composition of basic structural elements of shungite attributing the latter to reduced graphene oxide nanosheets with an average 11:1:3 (C:O:H) atomic content ratio.     

DFT studies of Si- and Al-doping effects on the acetone sensing properties of BC3 graphene

In order to find a novel sensor, reactivity and sensitivity of the intrinsic, Al- and Si-doped BC₃ graphene-like sheets to an acetone molecule were investigated by using B3LYP and ωB97X-D density functional calculations. Adsorption of acetone on the intrinsic, Al- and Si-doped BC₃ sheets releases energies of about 7.2, 36.5 and 24.8 kcal/mol, respectively, using ωB97X-D. The Si-doped sheet presents high sensitivity to acetone compared with the intrinsic and Al-doped sheets indicated by the calculated geometrical structures and electronic properties for these systems. The HOMO/LUMO energy gap of Si-doped BC₃ sheet is significantly decreased from 2.20 to 1.65 eV (B3LYP), which would result in electrical conductance increment. Thus, Si-doped sheet are expected to be a potential candidate for detecting the presence of acetone.     

Dynamic magnetic properties of Ising graphene-like monolayer

Dynamic magnetic properties of the mixed-spin (3/2, 5/2) Ising graphene-like monolayer in an oscillating magnetic field are studied by means of Monte Carlo simulation. The effects of Hamiltonian parameters such as crystal field and time-dependent oscillating magnetic field on the dynamic order parameter, susceptibility and internal energy of the system are well presented and explained. Moreover, much attention has also been dedicated to the phase diagrams with different parameters in order to better comprehend the impacts of these parameters on the critical temperature. Our results reveal that the crystal fields of two sublattices have similar effects on the critical temperature, but the bias field and amplitude of oscillating field have opposite effects on it. We hope that our research can be of guiding significance to the theoretical and experimental studies of graphene-like monolayer.     

New template for metal decoration and hydrogen adsorption on graphene-like C3N4

From density functional theory calculations we identify a graphene-like C₃N₄ (g-C₃N₄) as an excellent template for stable and well dispersed decoration of alkali (Li) and 3d transition metal (TM) atoms. The porous sites of g-C₃N₄ accommodate excessive N lone-pair electrons and promote hybridization between the orbitals of N and the metal atoms. The most stable TM decorations (Ti and Sc) on g-C₃N₄ exhibit high capacities of hydrogen adsorption with binding energies suitable for mobile applications. These metal decorated g-C₃N₄ may also prove useful in catalytic and sensing applications for their unique nanoscale structural features unavailable in conventional nano-clusters.     

Band Gap Modulation by Two-Dimensional h-BN Nanostructure

Physics of the Solid State - Two-dimensional hexagonal boron nitride (h-BN) as a graphene-like material was investigated due to its impending applications in electronics. The h-BN band gap Eg as an...     

Synthesis of biomass-derived 3D porous graphene-like via direct solid-state transformation and its potential utilization in lithium-ion battery

Biomass-derived porous carbon materials have recently received considerable attention for the use in energy storage devices due to the low cost. In the work here, water-absorbing biomass of agarics has been used directly to synthesize three-dimensional porous graphene-like (3D-PGL) via a facile, economical, and eco-friendly two-step solid-state transformation process. Characterization results reveal that Fe³⁺ pre-adsorbed agarics are carbonized to be uniform Fe₃O₄/C composite in the first step. Then the C precursor is catalyzed to be 3D-graphene in the second step by in situ-formed Fe that was reduced by C around. When assembled as anodes for lithium-ion batteries, the 3D-PGL delivers excellent cycling performance (as high as 572 mAh g^?1 after 1200 cycles’ running at 0.2 A g^?1). Furthermore, it is worth to mention that when tuning the amount of pre-adsorbed Fe³⁺, two-dimensional graphene sheet (2D-GS) is obtained.     

单元素类石墨烯二维拓扑材料的研究进展

除了石墨烯外,很多主族元素也可以形成类似石墨烯的稳定单层结构,并且具有丰富的物理化学性质及广阔的应用前景.其中在物理学中最引人注目的是理论预言在这些材料中预言存在的二维拓扑物性.单元素类石墨烯二维材料已经经历了十余年的研究进程,目前已经理论发现和实验制备出了若干新型二维拓扑材料,成为当前凝聚态物理和新材料领域重要研究方向之一.在这篇评述中,我们将详细介绍这一领域的研究历程、研究思路,以及最新研究进展,并对其进一步的研究方向做出展望.     

Adsorptions of metal adatoms on graphene-like BC_3 and their rich electronic properties: A first-principles study

Density functional calculations have been performed to investigate the adsorption of twenty two different kinds of metal adatoms on graphene-like BC_3. In contrast to the graphene adsorbed with adatoms, the BC_3 with adatoms shows many interesting properties.(1) The interaction between the metal adatoms and the BC_3 sheet is remarkably strong. The Li, Na, K, and Ca possess the binding energies larger than the cohesive energies of their corresponding bulk metals.(2)The Li, Na, and K adatoms form approximately ideal ionic bonds with BC_3, while the Be, Mg, and Ca adatoms form ionic bonds with BC_3 with slight hybridization of covalent bonds. The Al, Ga, In, Sn, and all transition metal adatoms form covalent bonds with BC_3.(3) For all the structures studied, there exhibit metal, half-metal, semiconducting, and spin-semiconducting behaviors. Especially, the BC_3 with Co adatom shows a quantum anomalous Hall(QAH) phase with a Chern number of -1 based on local density approximation calculations.(4) For Li, Na, K, Ca, Ga, In, Sn, Ti, V, Cr,Ni, Pd, and Pt, there exists a trend that the adatom species with lower ionization potential have lower work function. Our results indicate the potential applications of functionalization of BC_3 with metal adatoms.     

Fermi Surface Topology Signature on the High Harmonics Generation in Graphene-Like Nanostructure

Journal of Experimental and Theoretical Physics - The response of high harmonics of a laser field to the change of Fermi surface topology in graphene-like nanostructures during the process of the...     

On the correction of errors in quantum cryptography systems

The Raman and photoluminescence spectra of short-period C/SiC superlattices produced by RF magnetron sputtering are investigated. The Raman data indicate that, in 35-period Sitall/Ni/[C/SiC] superlattices with the C and SiC effective thicknesses of 3.5 and 3 Å, respectively, subjected to postgrowth avalanche annealing, the carbon layers assume the structure of multilayer graphene with 3–5 graphene sheets per superlattice period. A method for the fabrication of graphene-like carbon structures on the basis of short-period superlattices grown by RF sputtering is suggested and implemented.     

石墨烯形核初期Cu(111)面上CxHy团簇生成的理论研究

采用基于密度泛函理论的第一原理计算方法,我们研究了Cu(111)表面上石墨烯成核生长过程中CxHy小团簇的吸附和生成行为. 计算结果表明：随着氢原子饱和度、氢原子个数的增大,CxHy团簇的形成能减小,碳原子与铜表面的平均距离增加,C-C键的平均键长呈增大趋势. 然而,当生成的CxHy团簇具有空间对称结构时,在一定程度上打破了上述规律性. 令人惊奇的是,形成的C3H4和C3H5对称团簇具有类似石墨烯的空间结构,这类结构可能在石墨烯的形成过程中起着重要的作用.     

石墨烯形核初期Cu(111)面上C_xH_y团簇生成的理论研究

采用基于密度泛函理论的第一原理计算方法,我们研究了Cu(111)表面上石墨烯成核生长过程中CxHy小团簇的吸附和生成行为.计算结果表明:随着氢原子饱和度、氢原子个数的增大,CxHy团簇的形成能减小,碳原子与铜表面的平均距离增加,C-C键的平均键长呈增大趋势.然而,当生成的CxHy团簇具有空间对称结构时,在一定程度上打破了上述规律性.令人惊奇的是,形成的C3H4和C3H5对称团簇具有类似石墨烯的空间结构,这类结构可能在石墨烯的形成过程中起着重要的作用.     

The hyperconjugation effect on the graphene counterparts based on silicon and germanium

Bending of the A = A (A of the group IVA) double bond neighboring is rationalized by the hyperconjugation phenomenon analysis. The bending is also observed for the high sized linear, cyclic or graphene-like compounds that imply the conjugated double bonds. The electronic delocalization takes place between occupied σ(π) and unoccupied π*(σ*) orbitals especially for compound implying Si and Ge atoms. Leading to rippled structure, this phenomenon affects the silicene and germane thickness sheets and probably would have some consequences on the properties of such compounds when they will be involved in the industries in the future. However we introduce a new parameter to assess the thickness of graphenic structures when the hyperconjugation takes place in the bonding framework. The study has been undertaken at high levels of theory like B3LYP/6-311 + G(3df,2p).     

Piezoelectric effect in graphene-like 2D supracrystals with a periodic perforation breaking the central symmetry

Components of the piezoelectric modulus tensor in graphene-like carbon 2D supracrystals with a periodic perforation breaking the centrosymmetry of the structure have been calculated. It has been shown that the piezoelectric moduli of the supracrystals with sp ² hybridization are one order of magnitude lower and those of the supracrystals with sp ³ hybridization are several time higher than in lithium niobate.     

Role of Van der Waals Forces in Graphene Adsorption over Pd, Pt, and Ni

We report ab initio computations with the Vienna Ab initio Simulation Package (VASP) aimed at elucidating the adsorption mechanism of graphene-like structures on (111) Pd, Pt, and Ni surfaces. To study the adsorption properties, we simulate an already-formed graphene layer. We present a comparative discussion of the graphene interactions with the three metals, focusing on the very particular adsorption of graphene over Pd.     

Physics and chemistry of silicene nano-ribbons

We review our recent discovery of silicene in the form of silicon nano-ribbons epitaxially grown on silver (1 1 0) or (1 0 0) surfaces, which paves the way for the growth of graphene-like sheets. We further draw some perspectives for this unique novel material upon mild hydrogenation.     

Design and synthesis of a novel 3D hierarchical mesocarbon microbead as anodes for lithium ion batteries and sodium ion batteries

This work presents a feasible route for the facile synthesis of three-dimensional (3D) hierarchical mesocarbon microbead (MCMB) as anodes for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). The MCMB is oxidized by modified hummers method, and then the precursor is treated by hydrogen reduction to form the HMCMB. The HMCMB with graphene-like architecture has high specific surface, sufficient pore volume, and increased interlayer spacing, which can provide more active insertion/extraction sites and reduce the Li⁺/Na⁺ diffusion resistance. When employed as anode materials for LIBs and SIBs, HMCMB anodes exhibit improved lithium and sodium storage capability. The HMCMB delivers a higher reversible capacity (471.1 and 177.5 mAh g^?1 at 100 mA g^?1 after 100 cycles) and a good rate performance (250 and 121 mAh g^?1 even at 1000 mA g^?1) for LIBs and SIBs, respectively.     

CuO掺杂C3N对C5F10O分解组分吸附性能的第一性原理研究

全氟五碳酮（C5F10O）作为可替代SF6的新型环保绝缘气体已被投入到实际应用中. 在绝缘设备内部不可避免的会发生局部放电等故障,造成C5F10O绝缘气体分解产生弱绝缘性能甚至剧毒的分解组分,为保证绝缘设备的安全运行,在不影响气敏传感器正常检测绝缘设备内部故障的情况下,需对这些分解组分进行有选择地吸附去除. 新型类石墨烯C3N材料在气体吸附领域具有良好的应用前景,文中基于第一性原理计算了CuO分子掺杂C3N对主要分解组分CF4、C2F6及剧毒产物CF2O、HF的吸附过程,计算并分析了各分解组分吸附时的吸附能、态密度、电荷转移量、差分电荷密度以及不同环境温度下的恢复时间. 结果表明,CuO-C3N对HF表现出良好的吸附性,CF2O次之,但其无法吸附CF4与C2F6,因此CuO-C3N可以作为一种高性能的气体吸附剂对C5F10O绝缘设备内的剧毒分解组分HF进行吸附去除.