Co-reporter:Xiaofang Li, Qingzhong Xue, Daliang He, Lei Zhu, Yonggang Du, Wei Xing, and Teng Zhang
ACS Sustainable Chemistry & Engineering October 2, 2017 Volume 5(Issue 10) pp:8815-8815
Publication Date(Web):August 14, 2017
DOI:10.1021/acssuschemeng.7b01612
Using Grand Canonical Monte Carlo calculations, sulfur and nitrogen codoped (S/N-) graphite slit-pores with different defects (Divacancy 5-8-5, NS-1, NS-2, Stone–Wales (SW) 5577) are constructed to study their selective CO2 adsorption from CO2/H2, CO2/N2, CO2/CH4 and CO2/H2O mixtures. Among all the defective S/N-graphite slit-pores, it is found that the doped sites of S and N atoms affect slightly on CO2 uptake of graphite slit-pore. More importantly, the increasing ratio of S/N enhances the selective CO2 adsorption. For example, at 300 K and 1 bar, the full N-graphite slit-pore with SW 5577 has a CO2 uptake of 79.77 mmol/mol with good CO2/H2 selectivity (∼356) whereas full S-graphite slit-pore with SW 5577 possesses a considerable CO2 uptake of 104.66 mmol/mol with excellent CO2/H2 selectivity (∼526). Furthermore, density functional theory calculations indicate this defective S/N-graphite slit-pore with higher ratio of S/N interacts more strongly with CO2 molecules compared with other gases, which demonstrates that S doping is a better choice than S/N codoping for impressive selective CO2 capture.Keywords: Adsorption energy; CO2 capture; Defect; Density functional theory; Grand Canonical Monte Carlo;
Co-reporter:Ya Xiong, Wenbo Lu, Degong Ding, Lei Zhu, Xiaofang Li, Cuicui Ling, and Qingzhong Xue
ACS Sensors May 26, 2017 Volume 2(Issue 5) pp:679-679
Publication Date(Web):May 9, 2017
DOI:10.1021/acssensors.7b00129
In this paper, a facile and elegant Green Chemistry method for the synthesis of SnO2 based hollow spheres has been investigated. The influences of doping, crystallite morphology, and operating condition on the O2 sensing performances of SnO2 based hollow-sphere sensors were comprehensively studied. It was indicated that, compared with undoped SnO2, 10 at. % LaOCl-doped SnO2 possessed better O2 sensing characteristics owing to an increase of specific surface area and oxygen vacancy defect caused by LaOCl dopant. More importantly, it was found that O2 sensing properties of the 10 at. % LaOCl–SnO2 sensor were significantly improved by ultraviolet light illumination, which was suited for room-temperature O2 sensing applications. Besides, this sensor also had a better selectivity to O2 with respect to H2, CH4, NH3, and CO2. The remarkable increase of O2 sensing properties by UV light radiation can be explained in two ways. On one hand, UV light illumination promotes the generation of electron–hole pairs and oxygen adsorption, giving rise to high O2 response. On the other hand, UV light activates desorption of oxygen adsorbates when exposed to pure N2, contributing to rapid response/recovery speed. The results demonstrate a promising approach for room-temperature O2 detection.Keywords: hollow spheres; LaOCl-doped SnO2; oxygen sensing; room temperature detection; UV light radiation;
Co-reporter:Cheng Lv;Ming Ma;Dan Xia;Jie Xie;Huijuan Chen
The Journal of Physical Chemistry C April 15, 2010 Volume 114(Issue 14) pp:6588-6594
Publication Date(Web):2017-2-22
DOI:10.1021/jp100110n
The influence of the chemical functionalization of graphene on the interfacial bonding characteristics between graphene and polymers was investigated using molecular mechanics and molecular dynamics simulations. The simulations show the bonding energy and shear stress between graphene and the polymer increase with the increase of the concentration of functionalized groups. Our simulations indicated that some specific chemical modifications of graphene play important roles in determining the strength of interfacial bonding characteristics between graphene and the polymer. Therefore, the attachment of some suitable chemical groups with a reasonable concentration to the graphene surface may be an effective way to significantly improve the load transfer between the graphene and polymer when graphene is used to produce nanocomposites.
Co-reporter:Ya Xiong, Qingzhong Xue, Cuicui Ling, Wenbo Lu, Degong Ding, Lei Zhu, Xiaofang Li
Sensors and Actuators B: Chemical 2017 Volume 241() pp:725-734
Publication Date(Web):31 March 2017
DOI:10.1016/j.snb.2016.10.143
•Hollow and porous nanofibers of LaOCl-SnO2 were synthesized by a facile electrospinning technique.•The responses of LaOCl-SnO2 based sensors upon exposure to CO2 gas in different oxygen containing backgrounds were systematically investigated for the first time.•The sensing mechanisms toward CO2 in low oxygen and high oxygen concentration backgrounds are related to VO and OO×, respectively.In this paper, undoped and LaOCl-doped SnO2 nanofibers were prepared by a simple one-step electrospinning technique and their responses upon exposure to CO2 gas in different oxygen containing backgrounds were systematically investigated. It was observed that the obtained nanofibers were hollow porous structures that gave rise to excellent performance. The sensor based on 8 at.% LaOCl-SnO2 nanofibers exhibited optimal response (Rgas/Rair = 3.7) toward 1000 ppm CO2 at 300 °C with response/recovery times of 24 s/92 s, and didn’t show any saturation over a wide range of CO2 concentrations (100–20000 ppm). In terms of the sensing behavior of these sensors, their sensing mechanisms are proposed as follows: (1) In low oxygen concentration background, CO2 primarily reacts with VO, which needs high activation energy to occur, so only a slight number of CO2 can take part in the reaction. (2) In high oxygen concentration background, CO2 mainly reacts withOO×. Since this reaction conducts easily, CO2 can react with OO× sufficiently. The proposed sensing mechanisms can help readers better understand the role oxygen plays in CO2 gas sensing process.Porous nanofibers of LaOCl-SnO2 were synthesized by electrospinning technique, which can effectively detect CO2 in different oxygen containing backgrounds.
Co-reporter:Xiaofang Li, Qingzhong XueXiao Chang, Lei Zhu, Cuicui Ling, Haixia Zheng
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 9) pp:
Publication Date(Web):February 20, 2017
DOI:10.1021/acsami.6b14281
By use of grand canonical Monte Carlo calculations, we study the effects of sulfur doping and humidity on the performance of graphite split pore as an adsorbent for CO2 capture. It is demonstrated that S doping can greatly enhance pure CO2 uptake by graphite split pore. For example, S-graphite split pore with 33.12% sulfur shows a 39.85% rise in pure CO2 uptake (51.001 mmol/mol) compared with pristine graphite split pore at 300 K and 1 bar. More importantly, it is found that S-graphite split pore can still maintain much higher CO2 uptake than that by pristine graphite split pore in the presence of water. Especially, uptake by 33.12% sulfur-doped S-graphite split pore is 51.963 mmol of CO2/mol in the presence of water, which is 44.34% higher than that by pristine graphite split pore at 300 K and 1 bar. In addition, CO2/N2 selectivity of S-graphite split pore increases with increasing S content, resulting from stronger interactions between CO2 and S-graphite split pore. Moreover, by use of density functional theory calculations, we demonstrate that S doping can enhance adsorption energy between CO2 molecules and S-graphene surface at different humidities and furthermore enhance CO2 uptake by S-graphite split pore. Our results indicate that S-graphite split pore is a promising adsorbent material for humid CO2 capture.Keywords: adsorption energy; CO2 capture; density functional theory; grand canonical Monte Carlo calculations; sulfur doping;
Co-reporter:Jianqiang Zhang, Xinglong Pan, Qingzhong Xue, Daliang He, Lei Zhu, Qikai Guo
Journal of Membrane Science 2017 Volume 532(Volume 532) pp:
Publication Date(Web):15 June 2017
DOI:10.1016/j.memsci.2017.03.004
•Superhydrophilic spindle-knotted H-PAN/GO nanofibers were fabricated.•H-PAN/GO membrane is superhydrophilic and ultralow-oil-adhension.•H-PAN/GO7% membrane exhibits ultra-fast flux (~3500 LMH) and excellent FRR (~99%).•The surface-adhered oil droplets can directionally self-transport under water.Polyacrylonitrile/graphene oxide (PAN/GO) composite fibers with spindle-knot structure have been fabricated by facile electrospinning and then hydrolyzed (H-PAN/GO) for tailoring their chemical features, and their separation performance for oil-water is evaluated. Herein, bio-inspired spindle-knot structures are induced by the GO sheets, which may be attributed to the mismatch between GO size and fiber diameter and the strong interaction between PAN and GO. It is found that H-PAN/GO membrane with GO concentration at 7% (H-PAN/GO7%) is superhydrophilic in air and ultralow-oil-adhesion under water. As a result, the H-PAN/GO7% membrane exhibits ultra-high flux (~3500 LMH), satisfied rejection ration (~99%) and outstanding flux recovery ratio (~99%) for separating oil-water emulsion. These outstanding separation performances mainly are attributed to the combination of chemical features of hydrolyzed PAN and spindle-knotted structure induced by GO. Moreover, self-transport of oil along spindle-knotted fiber under water is demonstrated by Lattice Boltzmann method (LBM) and the anti-fouling mechanism of this structure was also explained in this paper. The H-PAN/GO fibrous membrane offers a novel insight into fabricating next generation membrane to separate oil-water emulsion.Download high-res image (189KB)Download full-size image
Co-reporter:Xiao Chang, Qingzhong Xue, Daliang He, Lei Zhu, ... Baoshou Tao
International Journal of Hydrogen Energy 2017 Volume 42, Issue 38(Volume 42, Issue 38) pp:
Publication Date(Web):21 September 2017
DOI:10.1016/j.ijhydene.2017.08.025
•A new 585 divacancy-defective germanene is designed for H2 separation.•The H2 separation performance of 585 germanene is studied using DFT calculations.•The 585 germanene can exhibits excellent H2 separation performance.As sustainable and clean energy, hydrogen is the most attractive and promising energy source in the future. Membrane separation is attractive due to its high hydrogen separation performance and low energy consumption. Van-der-Waals-corrected density functional theory (DFT) calculations are performed to investigate the hydrogen separation performance of 585 divacancy-defective germanene (585 germanene). It is found that the 585 germanene presents a surmountable energy barrier (0.34 eV) for hydrogen molecule passing through the membrane, and that membrane exhibits extremely high selectivity for H2 molecules over CO, CO2, N2, CH4 and H2S molecules in a wide range of temperatures. Meanwhile, the hydrogen permeance of 585 germanene can reach 1.94 × 10−7 mol s−1 m−2 Pa−1 at the low limit temperature of methane reforming (at 450 K), which is higher than the industrially acceptable gas permeance. With high selectivity and permeance, the 585 germanene is a promising candidate for hydrogen separation.Using van-der-Waals-corrected DFT calculations, we demonstrate that 585 divacancy-defective germanene has a good performance for H2 separation and it can serve as a superior membrane for H2 separation.Download high-res image (359KB)Download full-size image
Co-reporter:Lei Zhu, Xiao Chang, Daliang He, Qingzhong Xue, ... Wei Xing
International Journal of Hydrogen Energy 2017 Volume 42, Issue 18(Volume 42, Issue 18) pp:
Publication Date(Web):4 May 2017
DOI:10.1016/j.ijhydene.2017.04.043
•A new 2D graphitic carbon oxide (g-C2O) membrane is designed for H2 separation.•The H2 separation performance of g-C2O membrane is studied using both DFT calculations and MD simulations.•The g-C2O membrane can separate H2 with excellent selectivity and ultrahigh permeance.Membrane technology has been widely used for H2 separation. In this paper, we theoretically explored the H2 separation performance of graphitic carbon oxide (g-C2O) monolayer. The van-der-Waals-corrected density functional theory (DFT) calculations demonstrate that g-C2O monolayer is chemically inert to the studied gas molecules (H2, CO2, CO, N2, and CH4), and with a suitable pore size, the g-C2O monolayer shows an exceptionally high selectivity for H2/CO2 (CO, N2, and CH4) in a wide range of temperatures. In addition, the molecular dynamics (MD) simulations yield a high H2 permeance for the g-C2O monolayer at room temperature. With excellent selectivity and ultrahigh permeance, the g-C2O monolayer has great potential application in H2 separation.Using van-der-Waals-corrected DFT calculations and MD simulations, we demonstrate that graphitic carbon oxide (g-C2O) monolayer has a good performance for H2 separation and it can serve as a superior membrane for H2 separation.Download high-res image (218KB)Download full-size image
Co-reporter:Haixia Zheng, Lei Zhu, Daliang He, Tianchao Guo, ... Qingzhong Xue
International Journal of Hydrogen Energy 2017 Volume 42, Issue 52(Volume 42, Issue 52) pp:
Publication Date(Web):28 December 2017
DOI:10.1016/j.ijhydene.2017.10.134
•H2/CH4 separation mechanism for two-dimensional graphene oxide (GO) membrane is studied.•The H2/CH4 separation performance of GO membrane is studied using MD simulations.•The GO membrane can separate H2/CH4 with excellent selectivity and ultrahigh H2 permeance.As an ultrathin, high-flux, and energy-efficient membrane, graphene oxide (GO) has shown great potential for gas separation. Using molecular dynamics (MD) simulations, we studied the H2/CH4 separation performance of GO membrane. It is found that the size of gas molecule and its interaction with GO sheet are two key factors in determining the diffusivity in interlayer gallery of GO, which results in significant difference of selectivity and permeability for H2 and CH4. The influences of two interlayer configuration parameters, the interlayer spacing and oxidation degree, on the separation of H2/CH4 are firstly studied. Then the effects of gas thermal behaviors, simulation temperature and initial gas pressure are also examined. Our studies uncover the underlying mechanism of H2/CH4 separation in GO membrane, and these understandings could promote efficient two-dimensional layered gas separation membrane materials development by engineering assemblies.Using molecular dynamics (MD) simulations, we demonstrate that graphene oxide (GO) membrane has a good separation performance for H2/CH4 and it can serve as a superior membrane for H2/CH4 separation.Download high-res image (254KB)Download full-size image
Co-reporter:Qingzhong Xue, Qikai Guo, Baoshou Tao, Zhide Han, Jianqiang Zhang, Xinglong Pan
Composites Part A: Applied Science and Manufacturing 2017 Volume 100(Volume 100) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.compositesa.2017.05.027
The key matter to achieve excellent dielectric properties is not only improving the interfacial bonding between nanocarbon materials and polymer matrix but also preventing the direct contact of adjacent nanocarbon materials. Unfortunately, few works have provided a feasible route to address these problems simultaneously. In this work, surface-modified amorphous carbon/MWCNTs shell/core structured nanohybrids (s-AC@MWCNTs) are prepared using a facile and environmentally friendly approach. On one hand, the amorphous carbon shell can isolate MWCNTs from direct contact. On the other hand, the surface modification of amorphous carbon shell obviously improves the interfacial bonding between s-AC@MWCNTs and poly (vinylidene fluride) (PVDF) matrix. As a result, the s-AC@MWCNTs can be monodispersed into the PVDF matrix to form numerous microcapacitors and thus enhance the dielectric performance of PVDF by ∼4 orders of magnitude. The largest dielectric constant of s-AC@MWCNTs/PVDF composites can reach 43800 while maintaining a suppressed dielectric loss below1.8.
Co-reporter:Degong Ding, Wenbo Lu, Ya Xiong, Xinglong Pan, Jianqiang Zhang, Cuicui Ling, Yonggang Du, Qingzhong Xue
Applied Surface Science 2017 Volume 426(Volume 426) pp:
Publication Date(Web):31 December 2017
DOI:10.1016/j.apsusc.2017.07.126
•Size-controlled La2O2CO3 nanoparticles were prepared by facile hydrothermal and annealing methods.•The monoclinic spheroidal La2O2CO3 nanoparticles with size of 12–25 nm exhibited superior sensing performance toward CO2 in different oxygen containing backgrounds.•The gas sensing mechanism can be explained for the interaction of CO2 with oxygen species on La2O2CO3 surface including chemisorption, surface reaction and desorption process.In this paper, we presented a simple method to fabricate size-controlled La2O2CO3 nanoparticle by annealing La(OH)3 nanocrystallines in air atmosphere. The microstructures of the samples were analyzed by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and scanning electron microscope (SEM). TEM images indicate that the La(OH)3 precursors consists of uniform ellipsoids with width of 9–15 nm and length of 15–30 nm and La2O2CO3 are spheroidal particles with size of 12–25 nm. XRD patterns indicate that La(OH)3 nanocrystallines are hexagonal phase and transform to monoclinic La2O2CO3 after annealing. And then, La2O2CO3 nanoparticle is printed on an interdigital electrode as a sensing material for CO2 detection. La2O2CO3 sensor exhibits good cycle stability performance and fast response and recovery (53 s and 120 s) over the wide range of 300–5000 ppm CO2 in air condition. In addition, we also investigate the effect of oxygen concentration in the background atmosphere on CO2 response of La2O2CO3 sensor. The CO2 sensing mechanisms for La2O2CO3 sensor can be attributed to the interaction of CO2 with oxygen species on La2O2CO3 surface including chemisorption, surface reaction and desorption process, which also can be used to explain other metal oxide based CO2 gas sensor.
Co-reporter:Xiaofang Li, Qingzhong Xue, Xiao Chang, Lei Zhu, Haixia Zheng
Journal of CO2 Utilization 2017 Volume 21(Volume 21) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jcou.2017.07.022
•The CNT induces the one-sided fluorinated graphene sheet to form F-CNS.•The one-sided F-CNS is a promising candidate for high selective CO2 capture.•The one-sided F-CNS interacts strongly with CO2 molecules compared with CO and C2H2.Carbon nanoscrolls have shown great potential in gas adsorption and storage. In this paper, a feasible method for synthesizing one-sided fluorine doped carbon nanoscroll (F-CNS) is proposed, and the adsorption behavior of CO2, CO and C2H2 on one-sided F-CNS has been firstly investigated via Grand Canonical Monte Carlo calculations. It is demonstrated that the one-sided F-CNS possesses outstanding CO2 uptake with good CO2/CO and CO2/C2H2 selectivity compared with pristine CNS. Specially, at 300 K and 1 bar, one-sided F-CNS shows a CO2 uptake of 68.87 mmol/mol and CO uptake of 12.09 mmol/mol, which is much higher than those of CO2 (16.6 mmol/mol) and CO (6.02 mmol/mol) for pristine CNS. Furthermore, our results demonstrate that the excellent selective CO2 adsorption capacity of one-sided F-CNS is owing to its stronger interactions with CO2 molecules than CO and C2H2 molecules. Our research suggests that one-sided F-CNS is a promising candidate for high selective CO2 capture.Download high-res image (152KB)Download full-size image
Co-reporter:Cuicui Ling;Tianchao Guo;Wenbo Lu;Ya Xiong;Lei Zhu
Nanoscale (2009-Present) 2017 vol. 9(Issue 25) pp:8848-8857
Publication Date(Web):2017/06/29
DOI:10.1039/C7NR03437G
The SnO2/Si heterojunction possesses a large band offset and it is easy to control the transportation of carriers in the SnO2/Si heterojunction to realize high-response broadband detection. Therefore, we investigated the potential of the SnO2 nanoparticle thin film/SiO2/p-Si heterojunction for photodetectors. It is demonstrated that this heterojunction shows a stable, repeatable and broadband photoresponse from 365 nm to 980 nm. Meanwhile, the responsivity of the device approaches a high value in the range of 0.285–0.355 A W−1 with the outstanding detectivity of ∼2.66 × 1012 cm H1/2 W−1 and excellent sensitivity of ∼1.8 × 106 cm2 W−1, and its response and recovery times are extremely short (<0.1 s). This performance makes the device stand out among previously reported oxide or oxide/Si based photodetectors. In fact, the photosensitivity and detectivity of this heterojunction are an order of magnitude higher than that of 2D material based heterojunctions such as (Bi2Te3)/Si and MoS2/graphene (photosensitivity of 7.5 × 105 cm2 W−1 and detectivity of ∼2.5 × 1011 cm H1/2 W−1). The excellent device performance is attributed to the large Fermi energy difference between the SnO2 nanoparticle thin film and Si, SnO2 nanostructure, oxygen vacancy defects and thin SiO2 layer. Consequently, practical highly-responsive broadband PDs may be actualized in the future.
Co-reporter:Xinglong Pan;Jianqiang Zhang;Qikai Guo;Yakang Jin;Wenbo Lu;Xiaofang Li;Cuicui Ling
Advanced Materials Interfaces 2016 Volume 3( Issue 15) pp:
Publication Date(Web):
DOI:10.1002/admi.201600153
Multi-walled carbon nanotubes (MWCNTs)/hydrophilic poly(vinylpyrrolidone) (PVP) films are prepared by a simple spin-coating method and the resistive humidity sensing properties of the films are studied in detail. It is demonstrated that the thermally treated MWCNTs/PVP film exhibits a reproducible and great response over a wide relative humidity range from 11% to 94%, fast response time (less than 15 s) and ultrafast recovery time (less than 1.8 s), which are superior to that of pristine PVP films. The effective enhancement of humidity sensing characteristics of MWCNTs/PVP films can be explained by the MWCNTs/PVP interfacial effect. The thermally treated MWCNTs/PVP films can be used as robust, cost-effective, and easy-to-use resistive humidity sensors. And the design concept used in this work can be extended to other carbon composites to fabricate excellent sensing materials for sensors.
Co-reporter:Jin Sun;Liangyong Chu;Qikai Guo;Tuo Lei;Fujun Xia;Zhongyang Zhang
Polymer Composites 2016 Volume 37( Issue 2) pp:327-333
Publication Date(Web):
DOI:10.1002/pc.23184
We provide a one-step hydrothermal reaction to modify graphite powders (GPs) and prepare hydroxyl modified GPs/poly(vinylidene fluoride) (PVDF) composites which have excellent dielectric properties using high conductivity, low cost GPs as raw material. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) showed that hydroxyl groups had been introduced to the surface of GPs. Scanning electron microscopy (SEM) showed that the hydroxyl modified GPs had better dispersion in the polymer matrix than the GPs. An ultra-high dielectric constant of more than 5.1 × 103 (dielectric loss is about 3.0) was obtained for the hydroxyl modified GPs/PVDF near the percolation threshold at 1 kHz. The hydroxyl modified GPs/PVDF composites exhibited better dielectric properties than most carbon/polymer composites. POLYM. COMPOS., 37:327–333, 2016. © 2014 Society of Plastics Engineers
Co-reporter:Qingzhong Xue, Zilong Liu, Fujun Xia, Yehan Tao, Yakang Jin
Computational Materials Science 2016 Volume 117() pp:103-109
Publication Date(Web):May 2016
DOI:10.1016/j.commatsci.2016.01.036
•Metallic nanowires can activate and guide PA helical wrapping on it.•The helical wrapping mechanism for PA and NWs complex is proposed.•Interface characteristics of the length of PA, diameter and kinds of NWs are clearly elucidated.•Two distinct helical wrapping structures can be formed.Morphology manipulation opens up a new avenue for controlling and tailoring functional properties of metallic nanowires (NWs), enabling the exploration of NWs based nanomaterials. Using molecular dynamic (MD) simulations, we demonstrate that NWs can activate and guide PA helical wrapping on it. This unique helical wrapping phenomenon results from the combined action of the van der Waals (vdW) interaction and the π–π stacking interaction. The simulations show that the distance between the PA and PtNW is about 2.94 Å, and the wrapping turns are closely related with the PA length and the diameter of NWs. The types of NWs have a great influence on the structure diversity of helical PA due to the size of NWs. Moreover, two distinct helical wrapping structures can be formed, which are a perfect DNA-like double helix and two independent helix configurations. It is expected that our results could stimulate enormous interests in the synthesis of NWs-polymer composites and helical polymers, which will lead to further development of a broad class of novel helical NWs-PA-based functional materials and eventually be beneficial for fabricating nanoscale devices.PA helical wrapping on metallic nanowires.
Co-reporter:Tiantian Wu, Qingzhong Xue, Xiaofang Li, Yehan Tao, Yakang Jin, Cuicui Ling, Shuangfang Lu
The Journal of Supercritical Fluids 2016 Volume 107() pp:499-506
Publication Date(Web):January 2016
DOI:10.1016/j.supflu.2015.07.005
•Molecular dynamic simulation was used to investigate kerogen extraction.•Extraction mechanisms of kerogen moieties with supercritical CO2 are elucidated.•Electrostatic interaction played a significant role in kerogen–shale interaction.•Effects of pressure and temperature on kerogen extraction were interpreted.•The simulation results are consistent with experimental results.The extraction process and mechanism of kerogen moieties with supercritical CO2 are elucidated using molecular dynamics simulations. It is demonstrated that supercritical CO2 can effectively dissolve the kerogen moieties adsorbed onto the shale surface, and the kerogen moieties dissolved in supercritical CO2 can be easily extracted from oil shale, because the interaction between the kerogen moieties dissolved in supercritical CO2 and the shale surface is greatly reduced. The dissolving capacity of supercritical CO2 is found to effectively increase with increasing pressure before the pressure reaches a critical value (approximately 50 MPa) and then increases slowly. Moreover, the dissolving capacity of supercritical CO2 increases with increasing temperature at high pressure, which is consistent with experimental results. In addition, the hydroxyl functional groups modified on the shale surface promote the extraction of kerogen moieties with supercritical CO2, and the polar kerogen moieties were more easily dissolved in supercritical CO2.
Co-reporter:Qikai Guo, Qingzhong Xue, Tiantian Wu, Xinglong Pan, Jianqiang Zhang, Xiaofang Li, Lei Zhu
Composites Part A: Applied Science and Manufacturing 2016 Volume 87() pp:46-53
Publication Date(Web):August 2016
DOI:10.1016/j.compositesa.2016.04.008
Weak interfacial bonding between carbon materials and polymer matrix impedes the formation of homogeneous composites, challenging to the enhancement of dielectric properties of such systems. In this work, we designed novel carbonized polyacrylonitrile/polyethylene glycol copolymer fibers (CPCFs) and then used them as fillers to enhance the dielectric properties of poly(vinylidene fluoride) (PVDF)-based composites. These CPCFs are rich in nitrogen (8.55%) and oxygen (3.94%) atoms on the surface of them. The results of molecular dynamic (MD) simulations indicate that the existence of these atoms significantly increase the interaction energy between CPCFs and PVDF matrix from −45.13 kcal/mol to −62.22 kcal/mol, which promotes the intercalation of conductive CPCFs into insulated PVDF matrix to form ultrathin microcapacitors. As a result, the largest dielectric constant of CPCFs/PVDF composites can reach 1583 (1 kHz), which is about 150 times higher than that of pure PVDF.
Co-reporter:Cuicui Ling, Qingzhong Xue, Zhide Han, Haipeng Lu, Fujun Xia, Zifeng Yan, Longjiang Deng
Sensors and Actuators B: Chemical 2016 Volume 227() pp:438-447
Publication Date(Web):May 2016
DOI:10.1016/j.snb.2015.12.077
•Pd/SnO2/SiO2/Si heterojunctions were produced using magnetron sputtering method.•The heterojunctions show a high response (∼17363%) to 1% H2 in air.•The interfacial energy band characteristics of Pd/SnO2/SiO2/Si heterojunctions are proposed.A series of Pd/SnO2/SiO2/Si heterojunction sensors were produced using magnetron sputtering method. It is found that the Pd/SnO2/SiO2/Si heterojunction exhibits ultrahigh H2 response of ∼17363% to 1.0% H2 at room temperature, and has fast response and recovery, excellent stability and selectivity. Therefore, this kind of heterojunction may be a promising candidate for effective H2 detection at room temperature. The H2 response characteristics and the optimum operating voltage of the sensors is modulated by the interface barrier potential between SnO2 and Si, which can be understood by the interfacial energy band characteristics of the Pd/SnO2/SiO2/Si heterojunction.The Pd/SnO2/SiO2/Si heterojunction exhibits ultrahigh response of ∼17363% to 1.0% H2, excellent stability and selectivity at room temperature.
Co-reporter:Lei Zhu, Qingzhong Xue, Xiaofang Li, Tiantian Wu, Yakang Jin and Wei Xing
Journal of Materials Chemistry A 2015 vol. 3(Issue 42) pp:21351-21356
Publication Date(Web):04 Sep 2015
DOI:10.1039/C5TA05700K
Using the first-principles density functional theory (DFT) and molecular dynamics (MD) simulations, we investigate the He separation performance of a porous C2N monolayer synthesized recently. The DFT calculations demonstrate that the porous C2N monolayer is stable enough to be used as a gas separation membrane and the porous C2N monolayer with a suitable pore size presents a surmountable energy barrier (0.13 eV) for He molecules passing through the membrane. Furthermore, the porous C2N monolayer shows an exceptionally high selectivity for He/Ne (Ar, CH4, CO2, N2, etc.) in a wide range of temperatures. Besides, using MD simulations we demonstrate that the porous C2N monolayer exhibits a He permeance of 1 × 107 GPU at room temperature, which is much higher than the value (20 GPU) in current industrial applications. Therefore, the porous C2N monolayer should be an excellent candidate for He separation from natural gas, due to its high selectivity and excellent permeability.
Co-reporter:Lei Zhu, Qingzhong Xue, Xiaofang Li, Yakang Jin, Haixia Zheng, Tiantian Wu, and Qikai Guo
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 51) pp:28502
Publication Date(Web):December 3, 2015
DOI:10.1021/acsami.5b09648
Using the van-der-Waals-corrected density functional theory (DFT) and molecular dynamic (MD) simulations, we theoretically predict the H2 separation performance of a new two-dimensional sp2 carbon allotropes-fused pentagon network. The DFT calculations demonstrate that the fused pentagon network with proper pore sizes presents a surmountable energy barrier (0.18 eV) for H2 molecule passing through. Furthermore, the fused pentagon network shows an exceptionally high selectivity for H2/gas (CO, CH4, CO2, N2, et al.) at 300 and 450 K. Besides, using MD simulations we demonstrate that the fused pentagon network exhibits a H2 permeance of 4 × 107 GPU at 450 K, which is much higher than the value (20 GPU) in the current industrial applications. With high selectivity and excellent permeability, the fused pentagon network should be an excellent candidate for H2 separation.Keywords: DFT; energy barrier; hydrogen separation; molecular dynamics; size restriction; two-dimensional carbon network
Co-reporter:Zilong Liu, Qingzhong Xue, Yehan Tao, Xiaofang Li, Tiantian Wu, Yakang Jin and Zhongyang Zhang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 5) pp:3441-3450
Publication Date(Web):04 Dec 2014
DOI:10.1039/C4CP04102J
Morphology manipulation opens up a new avenue for controlling and tailoring the functional properties of graphene, enabling the exploration of graphene-based nanomaterials. Through mixing single-side-hydrogenated graphene (C4H) with fluorinated graphene (C4F) on one single sheet, the C4H/C4F-type graphene superlattices can self-scroll at room temperature. We demonstrate using molecular dynamic (MD) simulations that different proportions, sizes, directions of hydrogenation and fluorination, and geometry of graphene have a great influence on the self-scrolling of superlattices into a variety of well-defined carbon nanoscrolls (CNSs), thus providing a controllable approach to tune their structures. Based on molecular mechanics (MM) simulations, the CNSs bear more than eight times the radial pressure than that of their multiwalled carbon nanotube (MWNT) counterparts, and an excellent radial elasticity of CNSs is also shown. Compared with conventional CNSs, these novel CNSs are endowed with more ample and flexible heterogeneous structures due to the on-demand hydrogenation and fluorination. Besides, this work provides a feasible route to achieve the necessary electronic and optical changes to be applied in graphene device applications.
Co-reporter:Yehan Tao, Qingzhong Xue, Zilong Liu, Meixia Shan, Cuicui Ling, Tiantian Wu, and Xiaofang Li
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 11) pp:8048
Publication Date(Web):March 12, 2014
DOI:10.1021/am4058887
First-principle density functional theory (DFT) calculation and molecular dynamic (MD) simulation are employed to investigate the hydrogen purification performance of two-dimensional porous graphene material (PG-ESX). First, the pore size of PG-ES1 (3.2775 Å) is expected to show high selectivity of H2 by DFT calculation. Then MD simulations demonstrate the hydrogen purification process of the PG-ESX membrane. The results indicate that the selectivity of H2 over several other gas molecules that often accompany H2 in industrial steam methane reforming or dehydrogenation of alkanes (such as N2, CO, and CH4) is sensitive to the pore size of the membrane. PG-ES and PG-ES1 membranes both exhibit high selectivity for H2 over other gases, but the permeability of the PG-ES membrane is much lower than the PG-ES1 membrane because of the smaller pore size. The PG-ES2 membrane with bigger pores demonstrates low selectivity for H2 over other gases. Energy barrier and electron density have been used to explain the difference of selectivity and permeability of PG-ESX membranes by DFT calculations. The energy barrier for gas molecules passing through the membrane generally increase with the decreasing of pore sizes or increasing of molecule kinetic diameter, due to the different electron overlap between gas and a membrane. The PG-ES1 membrane is far superior to other carbon membranes and has great potential applications in hydrogen purification, energy clean combustion, and making new concept membrane for gas separation.Keywords: density functional theory; energy barrier; hydrogen purification; molecular dynamics; porous graphene; size restriction;
Co-reporter:Haixiang Sun, Cheng Ma, Bingbing Yuan, Tao Wang, Yanyan Xu, Qingzhong Xue, Peng Li, Ying Kong
Separation and Purification Technology 2014 Volume 122() pp:367-375
Publication Date(Web):10 February 2014
DOI:10.1016/j.seppur.2013.11.030
•Cardo polyimide is prepared using low temperature solution copolymerization method.•The gas separation properties of cardo polyimide/TiO2 MMMs were greatly improved.•The PO2 and aO2/N2 of MMMs were beyond Robeson’s trade-off upper bound.•The structure and working mechanism of MMMs on the gas separation are proposed.This paper reports the synthesis of a novel cardo type polyimide PI(BTDA–BAPF–DMMDA) based on 3,3′,4,4′-benzophenone-tetracarboxylic dianhydride (BTDA), 9,9′-bis (4-aminophenyl) fluorine (BAPF) and 4,4′-biamino-3,3′-dimethyldiphenyl-methane (DMMDA) using the low temperature solution copolymerization method, and cardo polyimide/TiO2 mixed matrix membranes (MMMs) were prepared by blending of TiO2 sol and the PI solution. The incorporation of the cardo groups was achieved through the reaction between the free –COOH of polyamide acid (PAA) and the –NH2 of the BAPF. The chemical structure and physical properties of membrane material were characterized using FTIR, 1H NMR, DSC and XRD. Results showed that the MMMs containing 24 wt% of TiO2 sol were nano-composite membranes with strong interactions between inorganic TiO2 phase and organic PI phase. Compared with PI(BTDA–DMMDA) membrane, the addition of BAPF and TiO2 greatly improved the gas separation properties of cardo PI membranes and MMMs. The gas permeation (PO2) and ideal separation factor (aO2/N2) of the cardo polyimide PI/TiO2 membrane with a BAPF: BTDA molar ratio of 0.15:1 and TiO2 content of 24 wt% were 4.5 Barrer and 15.8 respectively, which were a respective 9.4 and 4.6 times higher than that of the PI(BTDA–DMMDA) membrane. The PO2 and aO2/N2 of the cardo polyimide/TiO2 MMMs prepared in this work were beyond Robeson’s trade-off upper bound, highly promising for future gas separation application.
Co-reporter:Teng Zhang, Cuicui Ling, Qingzhong Xue, Tiantian Wu
Chemical Physics Letters 2014 Volume 599() pp:100-103
Publication Date(Web):18 April 2014
DOI:10.1016/j.cplett.2014.03.035
•Hydrogen storage process of Li-doped graphene considering H2 and O2 coadsorption has been discussed.•Both the morphological transformation and the adsorption energy have been analyzed in detail.•Li-doped graphene can adsorb 3 H2 per unit under the coadsorption condition.•The overlap among O2 5σ, 1π orbital, Li 2s orbital and the H2 σ bonding contribute to the Ead(H2) under the coadsorption condition.The influence of oxygen molecule (O2) on the hydrogen storage process of Li-doped graphene has been investigated using the density functional theory (DFT) simulation. The results show that, the existence of the O2 has a large influence on the hydrogen storage process of Li-doped graphene. Under the condition of coadsorption, each Li atom can only adsorb 3 H2 (4 H2 can be adsorbed without O2) with a theoretical storage density of 2.6 wt.%.
Co-reporter:Yonggang Du, Qingzhong Xue, Zhongyang Zhang, Fujun Xia
Materials Letters 2014 Volume 135() pp:151-153
Publication Date(Web):15 November 2014
DOI:10.1016/j.matlet.2014.07.141
•A simple method is proposed to fabricate Pd–rGO/SiO2/Si Schottky junction.•The Schottky junction shows an ultrahigh H2 response.•The mechanism of the H2 sensitivity is explained by thermionic emission theory.Palladium decorated reduced graphene oxide/SiO2/Si (Pd–rGO/SiO2/Si) Schottky junction was fabricated by a simple, practical filtration and transfer-printing method. The current–voltage characteristics of the Pd–rGO/SiO2/Si Schottky junction are very sensitive to hydrogen (H2). An ultrahigh gas response of 970% was achieved using the Schottky junction operated in reverse bias mode at room temperature (RT) for detection of 0.16% H2, which is much better than that obtained using graphene-based resistance-type H2 sensors at RT reported previously, due to the junction effect. The gas response enhancement principle demonstrated in this letter can be readily and extensively applied to other graphene-based gas sensing systems.
Co-reporter:Jin Sun, Qingzhong Xue, Qikai Guo, Yehan Tao, Wei Xing
Composites Part A: Applied Science and Manufacturing 2014 Volume 67() pp:252-258
Publication Date(Web):December 2014
DOI:10.1016/j.compositesa.2014.09.006
MnO2/graphene nanosheets/MnO2 (MGM) is fabricated by a facile and effective ethanol-assisted graphene-sacrifice reduction method. The morphology and structure of the MGM are examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The MGM is used as a dielectric filler to prepare MGM/Polyvinylidene composites by solution casting and hot pressing. The MGM/Polyvinylidene composites exhibit excellent dielectric properties (dielectric constant is 2360, dielectric loss is 2.0) near the percolation threshold at 1 kHz which are better than that of most carbon/polymer composites. The excellent dielectric properties originate from the poor conductive MnO2 layers which not only ensure good dispersion of graphene nanosheets in the Polyvinylidene fluoride but also act as inter-particle barriers to prevent direct contact of the graphene nanosheets.
Co-reporter:Tiantian Wu ; Qingzhong Xue ; Cuicui Ling ; Meixia Shan ; Zilong Liu ; Yehan Tao ;Xiaofang Li
The Journal of Physical Chemistry C 2014 Volume 118(Issue 14) pp:7369-7376
Publication Date(Web):March 19, 2014
DOI:10.1021/jp4096776
It is demonstrated that the fluorine-modified porous graphene membrane has excellent selectivity for CO2/N2 separation by using molecular dynamic (MD) simulations. We also investigated in detail the mechanism of the fluorine-modified porous graphene membrane for CO2/N2 separation by using first-principles simulations. We find that the diffusion barriers for CO2 and N2 to pass through the pore-22 (with 22 carbon atoms drilled out) graphene membrane are relatively small, which indicates that the pore-22 has a low selectivity for CO2/N2 separation. After fluorine modification, the diffusion barrier for CO2 to pass through decreases to 0.029 eV, while the diffusion barrier for N2 greatly increases to 0.116 eV. Therefore, N2 gets more difficult, while CO2 gets easier to penetrate through the fluorine-modified pore-22. The fluorine-modified pore-22 porous graphene shows a great enhancement of selectivity for CO2/N2 separation, which is consistent with the MD results. Our studies show that first-principles simulations can be well used to understand the MD results and propose an economical and efficient means of separating CO2 from N2, which may be useful for designing new concept membranes for gas separation, like CO/N2 and SO2/N2 separations.
Co-reporter:Xiaofang Li ; Qingzhong Xue ; Zilong Liu ; Cuicui Ling ; Yehan Tao ;Tiantian Wu
The Journal of Physical Chemistry C 2014 Volume 118(Issue 29) pp:16087-16094
Publication Date(Web):July 7, 2014
DOI:10.1021/jp4122084
C4H nanotube (C4HNT) which is a novel kind of hydrogenated carbon nanotubes (CNTs) has gradually attracted much attention due to its unique structure and potential applications. In this work, we systematically studied the mechanical properties of C4HNT using classical molecular dynamics and molecular mechanics simulations. It is found that C4HNT can bear much greater radial pressure than CNT. For example, the collapse pressure of (10, 0) C4HNT can reach 25 GPa, which is more than 4 times that of (10, 0) CNT (6 GPa). However, hydrogenation weakens the value of Young’s modulus of CNT, and leads to the descent of axial strength of CNT. Besides, it is demonstrated that the collapse pressure of C4HNT decreases with increasing tube diameter while the Young’s modulus of C4HNT is independent of tube diameter. And the tube number, chirality, length have no effect on the axial and radial mechanical properties of C4HNT. The results show that C4HNT has much better radial mechanical properties than CNT so that C4HNT may be an ideal filler to enhance the local mechanical support of nanocomposites.
Co-reporter:Liangyong Chu, Qingzhong Xue, Jin Sun, Fujun Xia, Wei Xing, Dan Xia, Mingdong Dong
Composites Science and Technology 2013 Volume 86() pp:70-75
Publication Date(Web):24 September 2013
DOI:10.1016/j.compscitech.2013.07.001
A novel sandwich structure based on few-layer graphene nanosheets (FLGs) composed of functionalized porous graphene, pristine graphene and functionalized porous graphene is proposed. After one-step alkaline-mediated hydrothermal treatment, the outmost layers of FLGs are etched to porous structure. Sandwich FLGs/poly(vinylidene fluoride) (PVDF) composites are fabricated and the composites show excellent dielectric properties among carbon-based fillers/PVDF composites. Owing to the unique semiconductor/conductor/semiconductor structure, theoretical analysis indicates that the dielectric constant of the sandwich FLGs/PVDF composites can be as high as 105. Our findings provide a novel strategy to fabricate high dielectric performance graphene based composites and the process is simple, low-cost and environmentally friendly.
Co-reporter:Zilong Liu, Qingzhong Xue, Cuicui Ling, Zifeng Yan, Jingtang Zheng
Computational Materials Science 2013 Volume 68() pp:121-126
Publication Date(Web):February 2013
DOI:10.1016/j.commatsci.2012.09.025
Efficient storage of hydrogen at room temperature is a bottleneck problem for hydrogen-based energy applications. A simple way of hydrogen storage and release by bending carbon nanotubes (CNTs) at room temperature is demonstrated using molecular dynamics (MD) simulations. A large number of hydrogen molecules can be put in CNTs at low temperatures, and then the hydrogen molecules can be completely encapsulated in the CNTs by bending the CNTs to a critical angle. The critical angle decreases with increasing CNT length, while it increases with increasing hydrogen number and temperature. However, the CNT chirality has a negligible influence on the critical angle and hydrogen storage process. It is demonstrated that the release of the hydrogen molecules also can be controlled accurately at room temperature by changing bending angle. The van der Waals force plays an important role in the hydrogen storage and release process. Compared with the conventional methods for hydrogen storage, the brand-new one occurs at room temperature and the release of the hydrogen molecules can be controlled accurately by changing bending angle. Besides, the special structure of the bent CNTs will also significantly enhance their applications in atomic storage, various chemical and biological sensors and actuators, catalyst and catalyst supports, nanoelectronic devices as well as high-capacity energy storage in solar cells or fuel cells.Graphical abstractHighlights► A simple way of hydrogen storage and release by bending carbon nanotubes (CNTs) at room temperature is demonstrated. ► Bending different CNTs with different hydrogen molecules was simulated. ► Bending the nanotubes to a critical angle, an energy barrier impedes the hydrogen molecules from fleeing out of the CNTs.
Co-reporter:Qingzhong Xue, Cheng Lv, Meixia Shan, Hongxin Zhang, Cuicui Ling, Xiaoyan Zhou, Zhiyong Jiao
Computational Materials Science 2013 Volume 71() pp:66-71
Publication Date(Web):April 2013
DOI:10.1016/j.commatsci.2013.01.009
In this study, a “cooling process”, performed by molecular dynamics simulation, was used to predict the glass transition temperature (Tg) of graphene–polymer composites. It was found that the functionalization of graphene can greatly enhance Tg of graphene–polymer composites, which shows that the functionalized graphene can intensify the arrest of the polymer chains mobility. Meanwhile, it was found that the thermal expansion of the composites exhibited a relation with the phonon mode vibrations and Brownian motions of the graphene in the composites. The computational results of Tg were in good agreement with the experimental results indicating that this computational method can be used to predict effectively Tg of graphene–polymer composites.Graphical abstractAdding functionalized graphenes to a polymer matrix can greatly increase Tg of the composites.Highlights► A simple method of predicting effectively the glass transition temperature (Tg) of graphene–polymer composites. ► Adding graphenes can increase the Tg of the composites. ► Adding functionalized graphenes can greatly increase Tg of the composites. ► The improved Tg of the PMMA nanocomposites provide new applications of the polymer.
Co-reporter:Meixia Shan, Qingzhong Xue, Tuo Lei, Wei Xing, and Zifeng Yan
The Journal of Physical Chemistry C 2013 Volume 117(Issue 31) pp:16248-16255
Publication Date(Web):July 12, 2013
DOI:10.1021/jp405155n
The self-assembling of helical polyacetylene (PA) nanostructures on single-walled nanotubes (SWNT) is studied using molecular dynamics (MD) simulations. The results indicate that SWNT can activate and guide the polymer chains helically wrapping onto it through van der Waals interaction and the π–π stacking interaction between the polymer chain and the outer surface of SWNT. The effects of SWNT diameter, SWNT chirality, and PA chain length on the configuration of the nanostructure have been extensively examined. It is found that a DNA-like double helix of two PA chains appears when the diameter of SWNT is larger than about 13.56 Å, the SWNT chirality has a negligible effect on whether the helical process could happen, and the two PA chains can interact with each other and then influence the formation of the perfect double helix. The geometrical structures between PA and SWNT may trigger enormous interests in chemical functionalization and helical polymer synthesis, which may eventually be beneficial for fabricating nanoscale devices. In addition, the self-assembly process of helical nanostructures on SWNT may also be helpful for understanding biological systems at the molecular level and for developing new materials.
Co-reporter:Zilong Liu, Qingzhong Xue, Teng Zhang, Yehan Tao, Cuicui Ling, and Meixia Shan
The Journal of Physical Chemistry C 2013 Volume 117(Issue 18) pp:9332-9339
Publication Date(Web):April 17, 2013
DOI:10.1021/jp402297n
The fabrication of carbon (C) doped hexagonal boron nitride (h-BN) has attracted more and more attention due to its widespread applications. A novel method of constructing custom-designed C doped h-BN via CO molecules interaction with the vacancy defect h-BN is demonstrated in this paper using density functional theory (DFT) calculations. The reaction process consists of the CO-vacancy recombination and extra O removal by CO; thus, C doped h-BN is formed without introducing additional defects. According to the population analysis, the charge transfer between CO and the defect h-BN is found to be important for the reaction. The proposed method is not only theoretically feasible but also has a relatively low reaction energy barrier, so the doping process can be easily achieved. Such a doping method provides a promising route toward on-demand tailoring of electrical and magnetic properties of diverse C doped BN nanostructures.
Co-reporter:Meixia Shan, Qingzhong Xue, Nuannuan Jing, Cuicui Ling, Teng Zhang, Zifeng Yan and Jingtang Zheng
Nanoscale 2012 vol. 4(Issue 17) pp:5477-5482
Publication Date(Web):17 Jul 2012
DOI:10.1039/C2NR31402A
The separation of CO2 from a mixture of CO2 and N2 using a porous graphene membrane was investigated using molecular dynamics (MD) simulations. The effects of chemical functionalization of the graphene sheet and pore rim on the gas separation performance of porous graphene membranes were examined. It was found that chemical functionalization of the graphene sheet can increase the absorption ability of CO2, while chemical functionalization of the pore rim can significantly improve the selectivity of CO2 over N2. The results show that the porous graphene membrane with all-N modified pore-16 exhibits a higher CO2 selectivity over N2 (∼11) due to the enhanced electrostatic interactions compared to the unmodified graphene membrane. This demonstrates the potential use of functionalized porous graphene as single-atom-thick membrane for CO2 and N2 separation. We provide an effective way to improve the gas separation performance of porous graphene membranes, which may be useful for designing new concept membranes for other gases.
Co-reporter:Cui-Cui Ling, Qing-Zhong Xue, Liang-Yong Chu, Nuan-Nuan Jing and Xiao-Yan Zhou
RSC Advances 2012 vol. 2(Issue 32) pp:12182-12189
Publication Date(Web):05 Oct 2012
DOI:10.1039/C2RA21581K
The effects of carbon nanotube (CNT) chirality, Stone–Wales (SW) defects and defect orientation on the radial collapse and elasticity of single-walled CNTs (SWNTs) were investigated using molecular mechanics and molecular dynamics (MD) simulations. It is found that the collapse pressure (Pc) of the armchair SWNT is 13.75 times higher than that of the zigzag SWNT. Moreover, the armchair SWNT with SW defects is easier to collapse compared to the intrinsic armchair SWNT, while the zigzag SWNT with SW defects is more difficult to collapse compared to the intrinsic zigzag SWNT; the SW2 defect makes Pc of SWNT (10, 10) decrease by 11.0%, while the SW4 defect makes Pc of SWNT (17, 0) increase by 100.0%. We introduce a model for SWNTs deformed in the radial direction according to the projection of the C–C bond along the bending direction. The model is validated for defect-free SWNTs and is then used to study the radial collapse of SWNTs with SW defects. The effect of chirality and SW defect on the radial collapse of SWNTs can be understood by the model. The strong sensitivity of radial collapse of SWNTs to chirality and SW defect can provide some guidance for high load structural applications of SWNTs.
Co-reporter:Nuannuan Jing, Qingzhong Xue, Cuicui Ling, Meixia Shan, Teng Zhang, Xiaoyan Zhou and Zhiyong Jiao
RSC Advances 2012 vol. 2(Issue 24) pp:9124-9129
Publication Date(Web):30 Jul 2012
DOI:10.1039/C2RA21228E
The effect of defects including vacancy and Stone–Wales (SW) defects on the Young's modulus of graphene sheets is investigated using molecular dynamic (MD) simulations. The simulations show that the presence of defects reduces the Young's modulus of graphene sheets and Young's modulus decreases with increasing degree of defects. In addition, the vacancy defects bring about a decrease in the Young's modulus, but their reconstruction is an important factor in stabilizing the modulus. Furthermore, we explore the Young's modulus of graphene with defects functionalized by hydrogen atoms and find that the hydrogenation of vacancy defects can increase the Young's modulus of the defective graphene but the hydrogenation of SW defects has the opposite effect.
Co-reporter:Cui-Cui Ling, Qing-Zhong Xue, Nuan-Nuan Jing and Dan Xia
RSC Advances 2012 vol. 2(Issue 19) pp:7549-7556
Publication Date(Web):13 Jun 2012
DOI:10.1039/C2RA20554H
The collapse and stability of carbon nanotubes (CNTs) functionalized by corrosion inhibitor molecules on the Fe (1 0 0) surface were studied using molecular mechanics and molecular dynamics simulations. The results show that the pristine CNTs can approach and even collapse spontaneously onto the Fe surface due to the van der Waals force between them when the CNT diameter exceeds a certain threshold. To avoid collapse of the CNTs, they are randomly side-functionalized by three corrosion inhibitors. When the modification coverage exceeds 4.33%, these modified CNTs can basically maintain their cylindrical structures on the Fe surface. The CNTs, randomly modified by appropriate inhibitor groups, can maintain their cylindrical structure stably, giving them the potential to be used as nanocontainers for maintaining or transporting molecules, etc. Moreover, our findings have great practical significance, and CNTs modified by the organic inhibitor groups can be considered to be environmentally-friendly corrosion inhibitors, which can provide some guidance towards understanding corrosion resistance of CNT-inhibitor composites.
Co-reporter:Teng Zhang ; Qingzhong Xue ; Meixia Shan ; Zhiyong Jiao ; Xiaoyan Zhou ; Cuicui Ling ;Zifeng Yan
The Journal of Physical Chemistry C 2012 Volume 116(Issue 37) pp:19918-19924
Publication Date(Web):August 30, 2012
DOI:10.1021/jp3073359
The interaction between oxygen molecule (O2) and metal-doped graphene has always been a heated discussed issue because O2 plays an important role in the graphene-based gas-storage materials, sensing platforms, and catalysts. In this article, the effect of an external electric field on the interaction between O2 and Au-doped graphene is studied using density-functional theory (DFT) calculations. The simulations show that O2 vertically moves away from Au-doped graphene substrate under a positive electric field, whereas under a negative electric field, accompanied by the vertical pushing out movement, O2 also moves toward the specific Au atom horizontally. Besides, the adsorption energy (Ead) of O2 is dramatically changed with electric field. A negative electric field strengthens the interaction between O2 and Au-doped graphene substrate, resulting in an enhanced Ead; the corresponding O–O distance (dO–O) is also elongated, while Ead is decreased and dO–O is shortened under a positive electric field. Because dO–O of the adsorbed O2 correlates with its catalytic activation, the findings can provide a new avenue to tune the O2 adsorption process onto Au-doped graphene substrate and may be useful in the future applications of graphene-based nanocatalyst.
Co-reporter:Dan Xia, Qingzhong Xue, Teng Zhang, Liangyong Chu, and Mingdong Dong
The Journal of Physical Chemistry C 2012 Volume 116(Issue 44) pp:23181-23187
Publication Date(Web):October 9, 2012
DOI:10.1021/jp308007c
Using molecular dynamics (MD) simulations, we report a carbon/silicon (C/Si) heterojunction formed by inserting carbon nanotubes (CNTs) into silicon nanotubes (SiNTs). Due to the weak mechanical property of the SiNTs, insertion of CNTs into them can not only reinforce their mechanical stabilities but also form multiwalled C/Si nanotube heterojunctions. The driving force of the coaxial assembly is primarily the intertube van der Waals (vdW) interactions. The coaxial self-assembly process is strongly tube size dependent, and the intertube distance (Δd) for a successful assembly between the two type nanotubes is around 3.5 Å. Simulations suggest possible bottom-up self-assembly routes for fabrication of novel nanomachines and nanodevices in nanomechanical systems. This study also suggests that the possibility of synthesizing SiNTs with fewer walls, even single-walled SiNT in aid of CNTs.
Co-reporter:CuiCui Ling;NuanNuan Jing
Science Bulletin 2012 Volume 57( Issue 23) pp:3030-3035
Publication Date(Web):2012 August
DOI:10.1007/s11434-012-5286-9
Using molecular mechanics and molecular dynamics simulations, we demonstrate that it is difficult to fabricate single-walled carbon nanotube (SWNT)/carbon nanoscroll (CNS) core/shell nanostructures on solid substrates because of the strong interaction between the graphene (GN) and the substrate. We propose an effective way to reduce the interaction between the GN and the substrate; SWNT/CNS core/shell nanostructures can be fabricated easily on SiO2 substrates by exploiting the volatilization of organic solvents, and inducement with SWNTs. These SWNT/CNS core/shell nanostructures on SiO2 substrates have the potential to be applied in telecom network transmission, or as electronic components in apparatuses such as microcircuit interconnects, nanoelectronics devices, heterojunctions, or sensors.
Co-reporter:Teng Zhang, Qingzhong Xue, Shuai Zhang, Mingdong Dong
Nano Today 2012 Volume 7(Issue 3) pp:180-200
Publication Date(Web):June 2012
DOI:10.1016/j.nantod.2012.04.006
Graphene with its peculiar and exceptional properties has been widely used in the preparation of next generation functional nanocomposites. However, future development of graphene and graphene-based composites crucially depends on the fundamental understandings of their hierarchical structures and dynamical behaviors provided by multiscale modeling and simulation. In the beginning of this review, some computational methods that have been applied extensively in the area of graphene and graphene-based composites are introduced, covering from Quantum Chemistry approach, Molecular Dynamics method to Monte Carlo simulation technique. Then the applications of these methods to various aspects of graphene and graphene-based composites are discussed in some detail. Particular emphasis is laid on researches that explore the physical properties, interacting mechanisms, and potential applications of graphene-based materials. Finally, future challenges and perspectives in modeling and simulation of graphene-based composites are addressed.Graphical abstractHighlights► Covers interacting mechanisms, physical properties, potential applications of graphene and graphene-based composites. ► CMS helps explain experimental phenomena, analyze interacting processes and provide guidance to experimental research. ► Detailed systematic study on the theoretical studies of graphene-based materials. ► Helpful for the future theoretical investigations and experimental fabrications of graphene-based composites.
Co-reporter:Xiaoyan Zhou, Qingzhong Xue, Ming Ma, Jianpeng Li
Thin Solid Films 2011 Volume 519(Issue 18) pp:6151-6154
Publication Date(Web):1 July 2011
DOI:10.1016/j.tsf.2011.04.009
We prepared ZnO/n-Si heterojunctions by depositing ZnO films on n-Si substrates with different resistivities by radio-frequency magnetron sputtering. The microstructure of ZnO film was analyzed by X-ray diffraction and scanning electron microscopy. The current–voltage characteristics and ethanol gas sensing properties of the junctions were investigated at room temperature. It is found that optimization of n-Si substrate resistivity is critical to enhance the ethanol gas sensitivity of ZnO/n-Si heterojunction. The ZnO/n-Si heterojunction with n-Si substrate of 2–3 Ω cm exhibits the best ethanol gas sensing property. The junction shows the sensitivity of 29.41% to 0.24 g/L ethanol gas under + 0.52 V forward bias voltage.
Co-reporter:Xiaoyan Zhou, Jianpeng Li, Ming Ma, Qingzhong Xue
Physica E: Low-dimensional Systems and Nanostructures 2011 Volume 43(Issue 5) pp:1056-1060
Publication Date(Web):March 2011
DOI:10.1016/j.physe.2010.12.014
An ethanol gas sensor based on ZnO nanorods was fabricated by hydrothermal synthesis. The structure and morphology of the ZnO nanorods are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electrical resistance, capacitance and impedance of the sensor were investigated at room temperature (23 °C) when exposed to air and ethanol gas of different concentrations. When the sensor was transferred from air to 20 ppm ethanol in air the electrical resistance decreased by 67%, the capacitance increased by 122% and the impedance decreased by 56% at the frequency of 100 Hz. The mechanism for the changes in capacitance and impedance as a function of frequency is presented.Graphical abstractResearch highlights► Capacitance of the ZnO nanorods increases with increase in ethanol concentration at low frequency. ► Impedance of the ZnO nanorods decreases with increase in ethanol concentration. ► Resistance of the ZnO nanorods decreases with increase in ethanol concentration.
Co-reporter:Liangyong Chu ; Qingzhong Xue ; Teng Zhang ;Cuicui Ling
The Journal of Physical Chemistry C 2011 Volume 115(Issue 31) pp:15217-15224
Publication Date(Web):June 29, 2011
DOI:10.1021/jp2030768
It is demonstrated using molecular dynamics (MD) simulations that P-doped silicon nanowires (Si NWs) can activate graphenes self-scrolling onto Si NWs and thus produce new kinds of graphene nanoscroll (NS)/Si core/shell heterojunctions. The simulations show that graphene sheets can fully self-scroll onto Si NWs when the Si NW radius is larger than a threshold of about 5 Å, forming a stable core/shell structure. It is the van der Waals force that plays a primary role in the self-scrolling process. The configuration of the graphene–Si heterojunction depends significantly on the diameter of the Si NWs. The final NS becomes multiwalled with increasing graphene length when the diameter of the Si NWs is larger than a threshold of about 6 Å. The zigzag NS is proved to be the most stable, while the chiral NSs are unstable and tend to evolve into zigzag NS and a model is set up to interpret the tendency from the standpoint of bond. It is demonstrated that the graphene width has no influence on the self-scrolling process at all. Compared with the conventional fabricating method, the new self-assembling one occurs at room temperature and the thickness of the NSs can be controlled accurately. Besides, the unique structure of the graphene/Si core/shell heterojunctions will significantly enhance their applications in nanoelectronic devices, hydrogen storage, solar cells, chemical or biological sensors, and energy storage in supercapacitors or batteries.
Co-reporter:Qingzhong Xue ; Dan Xia ; Cheng Lv ; Nuannuan Jing ;Cuicui Ling
The Journal of Physical Chemistry C 2011 Volume 115(Issue 42) pp:20471-20480
Publication Date(Web):September 13, 2011
DOI:10.1021/jp207064d
Using molecular dynamics (MD) simulations, we demonstrate the domino effect of a carbon nanotube (CNT) whose diameter is less than 35 Å. Our simulations show that the domino wave will propagate backward, when the CNT has certain appropriate dimensions (length and diameter), after passing through the whole CNT for the first time, and then develops over the leftover standing up CNT ring again, until the energy is released. The optimal conditions for the backward-propagating phenomenon are that the CNT diameter is about 22 Å and its length is around 225–325 Å. Molecules and atoms inside the CNT can be expelled by the domino wave at muzzle velocities of over 1 km/s, more than 1.5 times the muzzle velocity of an AK-47 machine gun. The domino effect is also found in SiC nanotubes for the first time. Our findings show a potential use for CNTs as the energy provider to deliver drug molecules, gas, water, and so on, and even can be used to design new concept domino-driven nanodevices, such as nanoinjectors, nanoperforators, and nanoguns.
Co-reporter:Jie Xie, Qingzhong Xue, Huijuan Chen, Adrian Keller, Mingdong Dong
Computational Materials Science 2010 Volume 49(Issue 1) pp:148-157
Publication Date(Web):June 2010
DOI:10.1016/j.commatsci.2010.04.038
Molecular mechanics (MM) and molecular dynamics (MD) simulations are conducted to investigate the influence of four different factors, namely temperature, chirality, radius and surface chemical modification, on the interaction between single-walled carbon nanotubes (SWNTs) and three fluorocarbon resins: PVF, PVDF, and PTFE. The results show that the interactions between the SWNTs and fluorocarbon resins are not influenced by temperature and chirality but strongly depend on the radius of SWNTs with the interactions increasing monotonously with the radius. Also the surface chemical modification on the SWNTs has a great effect on the interaction between the nanotubes and the fluorocarbon resins. Among five kinds of functional groups: methyl, amidogen, hydroxyl, –F and carboxyl, the three fluorocarbon resins can only adhere onto the SWNTs modified by methyl. The interactions between the SWNTs and the fluorocarbon resins are observed to increase with increasing functional group coverage. However, in the case for PTFE, an optimum functional group coverage is found beyond which the interactions decrease again. In addition, the ability of the PTFE to adsorb onto the methylic SWNTs is weaker than that of the other two resins due to its non-adhesive nature.
Co-reporter:Jie Xie, Qingzhong Xue, Huijuan Chen, Dan Xia, Cheng Lv and Ming Ma
The Journal of Physical Chemistry C 2010 Volume 114(Issue 5) pp:2100-2107
Publication Date(Web):January 15, 2010
DOI:10.1021/jp910630w
Using molecular dynamics (MD) simulations, we focus on the influences of different solid surfaces and functional groups on the collapse of single-walled nanotubes (14, 14) (SWNTs). The results show that the SWNTs can fully collapse on Fe, Ni, and graphite surfaces, which may attribute to the strong metallicity of these surfaces, but partially collapse on the Si surface, and the deformation of SWNTs with different diameters on the Si surface is in line with previous investigations. Besides, with increasing oxygen concentration, the deformation degree of SWNTs on Fe, FeO, and Fe2O3 surfaces decreases, which demonstrates that the deformation of SWNTs is mainly caused by the interaction between the SWNT and the metal atoms. Take −NH2-modified SWNT as an example. It is found that the modification coverage required for avoiding the collapse of the SWNTs varies for different surfaces. The interaction energies between Fe, Ni, graphite, and Si surfaces and −NH2-modified SWNTs linearly decrease with increasing functional group coverage. For four kinds of functional groups, −NH2 and −COOH have similar and better ability to avoid the collapse of the SWNTs; −CH3 has a worse ability; and the ability of −OH is the worst.
Co-reporter:Hui-Juan Chen, Qing-Zhong Xue, Ming Ma, Xiao-Yan Zhou
Sensors and Actuators B: Chemical 2010 Volume 150(Issue 1) pp:487-489
Publication Date(Web):21 September 2010
DOI:10.1016/j.snb.2010.07.038
Amorphous carbon (a-C) films were deposited on n-silicon by direct current magnetron sputtering at room temperature (RT) and the corresponding microstructures were characterized. The RT capacitive humidity sensing properties of the a-C film/n-Si (C/Si) heterojunctions were studied by a standard two-probe method. The result shows that the capacitance of the heterojunctions increases with decreasing frequency, because the adsorbed water molecules can become more polarized at lower frequencies. It was also shown that with the relative humidity (RH) changing from 11% to 95%, a capacitive response of over 200% was achieved at 1 kHz, and the capacitive response is highly linear with RH for the given frequencies. The increase in capacitance of the C/Si junction with increasing relative humidity can be attributed to the increase in the amount of physisorbed water having a dipole moment. The study shows that the C/Si junctions have potential application as humidity gas sensors.
Co-reporter:Qingbin Zheng, Dan Xia, Qingzhong Xue, Keyou Yan, Xili Gao, Qun Li
Applied Surface Science 2009 Volume 255(Issue 6) pp:3534-3543
Publication Date(Web):1 January 2009
DOI:10.1016/j.apsusc.2008.09.077
Abstract
In this study, the non-covalent association of single-walled nanotube (SWNT) with polyethylene (PE) molecule and the influence of sidewall modification on the interfacial bonding between the SWNTs and polymer were investigated using molecular mechanics (MM) and molecular dynamics (MD) simulations. The model of interaction between the initially separated PE and SWNT fragments, which can be either wrapping or filling, was computed. The possible extension of polymers wrapping or filling SWNTs can be used to structurally bridge the SWNTs and polymers to significantly improve the load transfer between them when SWNTs are used to produce nanocomposites. The interfacial bonding characteristics between the single-walled nanotubes, on which –COOH, –CONH2, –C6H11, or –C6H5 groups have been chemically attached, and the polymer matrix were also investigated by performing pullout simulations. The results show that appropriate functionalization of nanotubes at low densities of functionalized carbon atoms drastically increase their interfacial bonding and shear stress between the nanotubes and the polymer matrix, where chemisorption with –C6H5 groups to as little as 5.0% of the nanotube carbon atoms increases the shear stress by about 1700%. Furthermore, this suggests the possibility to use functionalized nanotubes to effectively reinforce other kinds of polymer-based materials as well.
Co-reporter:Jie Xie, Qingzhong Xue, Qingbin Zheng, Huijuan Chen
Materials Letters 2009 Volume 63(Issue 2) pp:319-321
Publication Date(Web):31 January 2009
DOI:10.1016/j.matlet.2008.10.034
Two typical phenomena (wrapping and filling), mainly about the interactions between biological molecules and carbon nanotubes (CNTs), were investigated by performing molecular dynamics (MD) simulations. We calculated the center of mass (COM) distance and the interaction energy between the biological molecules and single-walled nanotubes (SWNTs). The influence of nanotube wall number, chirality, radius and temperature was also investigated by a series of MD simulations. The results indicated that Vitamin A and β-Carotene were two promising biomaterials for decoration of CNTs. The interactions between biological molecules and CNTs could be influenced by those four factors. The general conclusions derived from this study may be of importance in medical and biological areas.
Co-reporter:Jie Xie, Qingzhong Xue, Keyou Yan, Huijuan Chen, Dan Xia and Mingdong Dong
The Journal of Physical Chemistry C 2009 Volume 113(Issue 33) pp:14747-14752
Publication Date(Web):July 15, 2009
DOI:10.1021/jp904670u
The rapid collapse of intrinsic single-walled carbon nanotube (SWNT) on the aluminum surface is observed using molecular dynamics simulation. The collapsing threshold is ∼10 Å, and the length has no influence on its collapse. Furthermore, we report that the structural stability of cylindrical SWNTs on the aluminum surface can be improved through the surface modification method. The stability of SWNTs can be enhanced by increasing the modification coverage. When the modification coverage exceeds 3.3% and 3.8% coverage, respectively, both amidogen- and carboxyl-modified SWNTs can basically maintain the cylindrical structure in our described systems. The results also show that, to avoid SWNTs collapse by chemical modification, the longer and larger SWNTs are, the more modification coverage SWNTs require, and vice versa. Our method allows potentially used modified SWNTs as nanocontainers for maintaining or transporting molecules, etc.
Co-reporter:KeYou Yan, QingZhong Xue, QingBin Zheng, Dan Xia, Huijuan Chen and Jie Xie
The Journal of Physical Chemistry C 2009 Volume 113(Issue 8) pp:3120-3126
Publication Date(Web):2017-2-22
DOI:10.1021/jp808264d
We studied the radial collapse of single-walled carbon nanotubes (CNTs) on the Cu2O surface using molecular dynamic simulations. When the diameter of CNTs exceeds a threshold, the CNTs approach the Cu2O surface and collapse spontaneously by the van der Waals force between the CNTs and the Cu2O surface. Because the collapsed CNTs are much more like graphenes, this collapse process of CNTs seems the reverse process of folding graphene nanoribbons to form CNTs. The collapsed CNTs exhibit as linked graphene ribbons and have the largest area to contact with the Cu2O surface, which greatly enhances adhesion between the CNTs and the Cu2O surface and keeps the system much more stable. Due to the hydrophobic properties of CNTs, the collapsed CNTs on the oxide surface can isolate the metal oxide from water solution, which suggests that the collapsed CNTs on the metal oxide surfaces have potential applications in corrosion protection and scale inhibition fields.
Co-reporter:Keyou Yan, Qingzhong Xue, Dan Xia, Huijuan Chen, Jie Xie and Mingdong Dong
ACS Nano 2009 Volume 3(Issue 8) pp:2235
Publication Date(Web):August 6, 2009
DOI:10.1021/nn9005818
We demonstrated a novel method to produce core/shell composite nanowires (NWs) by self-scrolling carbon nanotubes (CNTs) onto copper NWs via forced-field-based molecular dynamic (MD) simulations. When large diameter CNTs are placed beside the copper NWs, the CNTs approach the NWs, collapse, and self-scroll onto the NWs, resulting in coaxial core/shell composite NWs. It is found that the van der Waals force plays an important role in the formation of the composite NWs. The expected outcome of this novel method is to determine various strategies on how to produce composite NWs. Coaxial core/shell composite NWs represent an important class of nanoscale building blocks with substantial potential for exploring new concepts and functional materials.Keywords: carbon nanotubes; composite nanowires; molecular dynamic simulation; nanowires; self-scrolling
Co-reporter:Qun Li, Qingzhong Xue, Qingbin Zheng, Lanzhong Hao, Xili Gao
Materials Letters 2008 Volume 62(Issue 26) pp:4229-4231
Publication Date(Web):15 October 2008
DOI:10.1016/j.matlet.2008.06.047
The chemically purified multiwalled carbon nanotube/poly(vinylidene fluoride) (MWCNT/PVDF) composites were fabricated. Raman spectroscopy and transmission electron microscopy micrographs indicated that the catalysts metal particles and amorphous carbon had been removed from the purified MWCNTs. The percolation threshold of the composites is relatively large, about 3.8 vol.%. The most important result is that the dielectric constant of the composites is enhanced remarkably, and the dielectric constant of 3600 is obtained in the composite with 8 vol.% purified MWCNT at 1 kHz. The large dielectric constant can be attributed to the preparation procedure and the interface effect between the MWCNTs and the polymer.
Co-reporter:Huijuan Chen, Qingzhong Xue, Qingbin Zheng, Jie Xie and Keyou Yan
The Journal of Physical Chemistry C 2008 Volume 112(Issue 42) pp:16514-16520
Publication Date(Web):2017-2-22
DOI:10.1021/jp803615v
Molecular dynamics (MD) simulations were used to study the interaction energy between single-walled carbon nanotubes (SWNTs) and polyphenylacetylene (PPA). The “wrapping” of nanotubes by PPA chains was computed. The influence of nanotube chirality, temperature, and chemical modification on the interfacial adhesion of nanotube−PPA was investigated. The results showed that the interaction energy between the SWNTs and PPA is strongly influenced by chirality but the influence by temperature could be negligible. For SWNTs with similar molecular weights, diameters, and lengths, the armchair-type nanotube may be the best nanotube for reinforcement. Besides, our simulations indicated that some specific chemical modifications of SWNTs play a very important role in determining the strength of interaction between the SWNTs and PPA. The SWNTs modified by methyl or phenyl groups can be well-wrapped by PPA, while the SWNTs modified by other types of groups cannot. The results also indicated that the interaction energy between the SWNTs and PPA increases with the increase of the concentration of functionalized groups. People have demonstrated that the increase of the concentration of functionalized groups can weaken the mechanics of SWNT. Therefore, the attachment of methyl or phenyl groups with reasonable concentration to the outer SWNTs should significantly improve the load transfer between the SWNTs and polymer when the SWNTs are used to produce nanocomposites.
Co-reporter:Lei Zhu, Yakang Jin, Qingzhong Xue, Xiaofang Li, Haixia Zheng, Tiantian Wu and Cuicui Ling
Journal of Materials Chemistry A 2016 - vol. 4(Issue 39) pp:NaN15021-15021
Publication Date(Web):2016/09/20
DOI:10.1039/C6TA04456E
Using van der Waals corrected density functional theory (DFT), we theoretically predict the performance of a strain-controlled graphenylene membrane in multifunctional gas separation. By applying lateral strain to this membrane, we find that the transition points between “closed” and “open” states for CO2, N2, CO, and CH4 passing through graphenylene membrane occur under 3.04%, 4.20%, 5.12%, and 10.78% strain, respectively. The H2 permeance is remarkably enhanced through tensile strain, and it reaches 2.6 × 10−2 mol s−1 m−2 Pa−1 under 3.04% strain, which is about 6 times higher than that with unstrained graphenylene membrane. At strain levels between 3.04% and 4.20%, this membrane can be used to separate CO2/N2. In particular, at strain levels of 4.20%, the permeance of CO2 for this strained membrane can reach 1.03 × 10−7 mol s−1 m−2 Pa−1 as well as 15.4 selectivity for CO2/N2, which are both higher than the industrially acceptable values of the permeance and selectivity. In addition, with a strain magnitude from 5.12% to 10.78%, a graphenylene monolayer can be used as a CH4 upgrading membrane. Our results demonstrate the promise of a tunable, multifunctional graphenylene gas-separation membrane, wherein the sizes of the nanopores can be precisely regulated by tensile strain. These findings may be useful for designing tunable nanodevices for gas separation and other applications.
Co-reporter:Zilong Liu, Qingzhong Xue, Yehan Tao, Xiaofang Li, Tiantian Wu, Yakang Jin and Zhongyang Zhang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 5) pp:NaN3450-3450
Publication Date(Web):2014/12/04
DOI:10.1039/C4CP04102J
Morphology manipulation opens up a new avenue for controlling and tailoring the functional properties of graphene, enabling the exploration of graphene-based nanomaterials. Through mixing single-side-hydrogenated graphene (C4H) with fluorinated graphene (C4F) on one single sheet, the C4H/C4F-type graphene superlattices can self-scroll at room temperature. We demonstrate using molecular dynamic (MD) simulations that different proportions, sizes, directions of hydrogenation and fluorination, and geometry of graphene have a great influence on the self-scrolling of superlattices into a variety of well-defined carbon nanoscrolls (CNSs), thus providing a controllable approach to tune their structures. Based on molecular mechanics (MM) simulations, the CNSs bear more than eight times the radial pressure than that of their multiwalled carbon nanotube (MWNT) counterparts, and an excellent radial elasticity of CNSs is also shown. Compared with conventional CNSs, these novel CNSs are endowed with more ample and flexible heterogeneous structures due to the on-demand hydrogenation and fluorination. Besides, this work provides a feasible route to achieve the necessary electronic and optical changes to be applied in graphene device applications.
Co-reporter:Lei Zhu, Qingzhong Xue, Xiaofang Li, Tiantian Wu, Yakang Jin and Wei Xing
Journal of Materials Chemistry A 2015 - vol. 3(Issue 42) pp:NaN21356-21356
Publication Date(Web):2015/09/04
DOI:10.1039/C5TA05700K
Using the first-principles density functional theory (DFT) and molecular dynamics (MD) simulations, we investigate the He separation performance of a porous C2N monolayer synthesized recently. The DFT calculations demonstrate that the porous C2N monolayer is stable enough to be used as a gas separation membrane and the porous C2N monolayer with a suitable pore size presents a surmountable energy barrier (0.13 eV) for He molecules passing through the membrane. Furthermore, the porous C2N monolayer shows an exceptionally high selectivity for He/Ne (Ar, CH4, CO2, N2, etc.) in a wide range of temperatures. Besides, using MD simulations we demonstrate that the porous C2N monolayer exhibits a He permeance of 1 × 107 GPU at room temperature, which is much higher than the value (20 GPU) in current industrial applications. Therefore, the porous C2N monolayer should be an excellent candidate for He separation from natural gas, due to its high selectivity and excellent permeability.
