石墨烯吸附甲醛的第一性原理研究

采用第一性原理研究了甲醛分子吸附于本征石墨烯、缺陷石墨烯和掺杂石墨烯的体系.通过计算石墨烯掺杂前后对甲醛气体的吸附能、电荷转移及能带和态密度,发现掺杂Pt后甲醛分子吸附能和电荷转移显著增大,这是由于Pt的掺杂在本征石墨烯能带中引入了杂质能级,增强了石墨烯和甲醛分子间的相互作用,可以提高石墨烯对甲醛气体的气敏响应速度和吸附能力.     

双层石墨烯掺杂Pd对CO和NO的气敏特性研究

采用基于密度泛函理论的第一性原理计算方法,研究了AA堆叠型双层石墨烯掺杂Pd原子(Pd/BG)后对气体分子CO和NO的气敏特性和吸附机理.结果表明,Pd原子的掺杂改变了双层石墨烯的电子性质和局部几何结构.Pd原子替代双层石墨烯的一个碳原子后,杂质原子突出层外区域(Po)和突入层间区域(Pi)都可以形成稳定结构,但是突出(Po)构型更有利于气体分子的吸附.对于Po构型,CO和NO吸附在Pd/BG上的最稳定结构是不同的,CO分子与石墨烯表面呈一定夹角,而NO分子近似垂直于石墨烯表面.Pd/BG对NO分子的吸附强于CO分子.气体分子在Po构型上属于化学吸附,而在Pi构型上属于物理吸附.Pd/BG吸附CO和NO气体分子后具有不同的电子性质.Pd/BG体系为半导体性质,在吸附CO气体分子后,转变为金属性,系统无磁性;而在吸附NO气体分子后变为金属性且具有较大磁矩.这种电子性质的变化能够阐明气体分子吸附的敏感程度.研究结果能够为石墨烯基的气体传感器或者探测器提供理论基础和实验指导.     

4d过渡金属掺杂石墨烯对HCN吸附行为的第一性原理研究

采用第一性原理的密度泛函理论方法研究了掺杂Y、Zr、Nb、Mo、Tc和Ru的石墨烯体系对氰化氢(HCN)的吸附作用。首先考察了HCN分子中H、C或N原子分别靠近吸附点的三种吸附构型。然后比较了吸附HCN前后掺杂石墨烯的能带变化。研究结果表明,掺杂Mo和Ru的石墨烯吸附HCN后的带隙大小变化大于20%,并表现为半导体行为,说明吸附后掺杂石墨烯的电导性能受影响较大。此外,进一步研究了掺杂Mo和Ru的石墨烯吸附HCN的过程,讨论了吸附能、带隙、晶格常数、HCN电荷和键长的变化,并分析了掺杂Mo和Ru的石墨烯的振动特性。研究表明,掺杂Mo和Ru的石墨烯对HCN的吸附非常敏感,这可能是开发HCN传感器的有用材料。     

基于石墨烯基复合材料的NH3气体传感器研究进展

NH₃的排放对环境和人类健康有重大影响。近年来,对NH₃的高效实时检测已成为环境监测及分析化学领域的研究热点。作为二维(2D)纳米材料的典型代表——石墨烯,以其独特的物化性能为气体的检测提供了良好的平台。石墨烯及石墨烯基复合材料已被广泛应用于NH₃气体的检测。本文综述了近10年来国内外基于石墨烯基复合材料的NH₃气体传感器的研究进展,重点介绍了几种常见石墨烯复合材料在NH₃气体传感器中的应用。与本征石墨烯相比,金属粒子掺杂石墨烯可增强其对NH₃的吸附能力;金属氧化物掺杂石墨烯可有效提高NH₃气体传感的灵敏度,但响应时间长、重复性较差;有机高分子掺杂石墨烯稳定性相对较差,对环境要求较高;石墨烯三元复合材料可有效提高传感器的稳定性,改善传感选择性。最后,文章对NH₃气体传感器的未来发展趋势进行了展望。     

空气吸附对石墨烯电学性能的影响

研究了空气掺杂对化学气相沉积(CVD)法制备的双层石墨烯底栅型场效应管电输运性能的影响。分别在大气、真空(<1Pa)、氮气以及不同湿度环境中测试了石墨烯场效应管的电学性能,测试结果表明大气中水分子和氧气分子的吸附导致的空穴掺杂作用使石墨烯的电学性能发生了严重退化,随着石墨烯表面吸附水分子和氧气分子的增多,狄拉克转变点电压向正方向的偏移量逐渐增大,空穴掺杂浓度增大,载流子迁移率减小。     

石墨烯传感器的研究进展

论述了石墨烯电化学和生物传感器的研究进展,包括石墨烯的直接电化学基础、石墨烯对生物小分子(Hydrogen peroxide,NADH,dopamine,etc.)的电催化活性、石墨烯酶传感器、基于石墨烯薄膜和石墨烯纳米带的实用气体传感器(可检测O2、CO和NO2)、石墨烯DNA传感器和石墨烯医药传感器(可用于检测扑热息痛)。     

石墨烯气敏性能的研究进展

石墨烯因具有高的电子迁移率和超大的比表面积而有望成为新一代的气敏材料,近年来有关石墨烯气体传感器的研究工作逐年增加.概述了石墨烯的结构和特性;介绍了典型石墨烯气体传感器的工作原理;综述了本征和功能化石墨烯的多种气体气敏特性在理论和实验上的研究现状.     

Li吸附对石墨烯、BC_3、C_3N电学性质影响的第一性原理研究

基于密度泛函理论(DFT)的第一性原理方法,对Li在未掺杂和B(N)掺杂浓度为25%(原子分数)的石墨烯表面最稳定位置的吸附进行了结构优化,计算了本征石墨烯及B(N)掺杂石墨烯吸附Li前后的能带结构、态密度、电荷转移、差分电荷密度和结合能。计算结果表明,B掺杂浓度为25%(原子分数)时可显著提高石墨烯的Li吸附能,N掺杂浓度为25%(原子分数)时减弱了石墨烯的Li吸附能。吸附Li后的石墨烯、BC3和C3N体系均显示出金属性。     

SW缺陷石墨烯铝原子吸附能的第一性原理研究

基于密度泛函理论（DFT）和广义梯度近似（GGA）,对SW（Stone--Wales）陷石墨烯的结构和吸附能进行了研究,计算了石墨烯吸附Al原子前后的能带结构,态密度和吸附能,计算结果表明,掺杂SW缺陷有利于石墨烯和具有自由电子的金属原子的吸附结合,与未掺杂时对比,掺杂SW缺陷可显著提高石墨烯片的吸附能。     

金原子修饰的石墨烯片对半胱氨酸的响应机理的第一性原理研究

使用密度泛函理论研究了本征石墨烯和经过金原子修饰的石墨烯吸附半胱氨酸的构型和电子性质.对比本征石墨烯,修饰金原子后的石墨烯与半胱氨酸之间有较强的结合能力和较短的连接距离,发生的是化学吸附.态密度的计算结果也显示半胱氨酸与金修饰后的石墨烯轨道之间存在显著的杂化现象,而本征石墨烯轨道杂化现象不明显.本征石墨烯与半胱氨酸发生的是物理吸附.预测相比于本征石墨烯,金修饰后的石墨烯是一种潜在的、更高灵敏度的半胱氨酸检测材料.     

Evaluation of Constants of Electron–Phonon Coupling between Gas Molecules and Graphene

The adsorption of CO, NO, NO₂, Н₂О, and NH₃ molecules on ideal graphene and graphene doped with aluminum is analyzed using simple models. The constants of electron–phonon coupling are evaluated with the Lennard-Jones 6–12 potential for ideal graphene and the 2–4 potential for doped graphene. It is demonstrated that the dimensionless electron–phonon-coupling constant for ideal graphene is ζ ? 1, while ζ ~ 1 corresponds to graphene doped with aluminum. Ways to use both types of graphene as a resistive gas sensor are discussed.     

掺杂和修饰的石墨烯对半胱氨酸吸附性能的密度泛函理论研究

使用密度泛函理论计算了掺杂或修饰Al或Mn原子的石墨烯对半胱氨酸的吸附性能。计算结果表明,掺杂或修饰Al或Mn原子后,Graphene与半胱氨酸之间结合稳定,具有较大的结合能。其中掺杂或修饰Mn原子的体系的吸附能整体高于掺杂或修饰Al原子的体系。石墨烯上修饰或掺杂Al或Mn原子,增加了石墨烯基底与半胱氨酸之间的电荷转移,特别是修饰方式显著改变了费米能级附近的性质,同时改变了Graphene的电导性质。Al或Mn原子修饰或者掺杂的Graphene除了增加对半胱氨酸吸附能力外,也是一种潜在的检测半胱氨酸的传感器材料,进而在生物领域得到更广泛的应用,比如用来检测富含半胱氨酸的金属硫蛋白。     

Effects of Stone-Wales defect on the interactions between NH3, NO2 and graphene

Using the density functional theory, the interactions between pristine, Stone-Wales defected graphenes (SW-graphene) and two small gas molecules (NH3 and NO2) were investigated and the potential applications of SW-graphene as gas sensors were exploited. Both NH3 and NO2 show weak interactions with pristine graphene. Introducing SW defect into the graphene structure has little effect on the NH3 adsorption, but dramatically enhances the adsorption of NO2 and causes significant deformation of the graphene sheet around the defect site. The strong interaction between NO2 and the SW-graphene also induces dramatic changes to the graphene's electronic structure. This work reveals that the SW-graphene could be an excellent candidate as highly selective sensing material for NO2.     

氧化石墨烯在气体传感器中的应用研究进展

氧化石墨烯因表面含有丰富的含氧官能团而具有十分优异的气敏性能,可应用于低浓度(ppb级)环境下气体的检测。综述了现阶段氧化石墨烯在气体传感器中的研究进展,分析了氧化石墨烯对湿度、NO_2、H_2、CH_4的敏感性能,重点探究了氧化石墨烯表面含氧官能团的类型对其选择性的影响规律,并总结了目前研究中存在的问题,为后续开展氧化石墨烯气体传感器的研究与应用提供借鉴。     

氨基化石墨烯气凝胶的制备及其对Cr(Ⅵ)吸附性能研究

以四乙烯五胺(TEPA)为氮源和改性剂,对氧化石墨烯(GO)进行氨基化改性,通过一步水热法制备四乙烯五胺-石墨烯气凝胶(TEPA-GA),采用FT-IR、XRD、拉曼光谱、SEM、XPS、TG等方法对产品的化学结构与形貌进行表征及性能检测。结果表明,通过TEPA成功将GO进行氨基化改性,并制备出具有多孔互穿网络结构的TEPA-GA,其具有超轻、密度小及热性能优异等特点。再将TEPA-GA用于对Cr(Ⅵ)的吸附研究,发现在最佳吸附条件下,吸附容量高达342.48mg/g。     

Effective Separation of CO2 Using Metal-Incorporated rGO Membranes

Graphene-based materials, primarily graphene oxide (GO), have shown excellent separation and purification characteristics. Precise molecular sieving is potentially possible using graphene oxide-based membranes, if the porosity can be matched with the kinetic diameters of the gas molecules, which is possible via the tuning of graphene oxide interlayer spacing to take advantage of gas species interactions with graphene oxide channels. Here, highly effective separation of gases from their mixtures by using uniquely tailored porosity in mildly reduced graphene oxide (rGO) based membranes is reported. The gas permeation experiments, adsorption measurement, and density functional theory calculations show that this membrane preparation method allows tuning the selectivity for targeted molecules via the intercalation of specific transition metal ions. In particular, rGO membranes intercalated with Fe ions that offer ordered porosity, show excellent reproducible N₂/CO₂ selectivity of ≈97 at 110 mbar, which is an unprecedented value for graphene-based membranes. By exploring the impact of Fe intercalated rGO membranes, it is revealed that the increasing transmembrane pressure leads to a transition of N₂ diffusion mode from Maxwell–Stefan type to Knudsen type. This study will lead to new avenues for the applications of graphene for efficiently separating CO₂ from N₂ and other gases.     

Nitrated tyrosine adsorption on metal-doped graphene: A DFT study

The adsorption of nitrated tyrosine on the intrinsic and metal-doped graphene was studied by density functional theory in order to explore the possibility of using graphene-based biosensor to detect the protein tyrosine nitration (PTN). The configurations of (a) phenolic ring coordination and (b) nitro group coordination on the graphene were compared. It was found that nitrated tyrosine was physisorbed on the intrinsic graphene and favored coordinating with the intrinsic graphene by phenolic ring, while chemisorption was observed on Au, Cr and Ni-doped graphene with high binding energy. In contrast, the nitrated tyrosine favored coordinating with the metal-doped graphene through metal-nitro group configuration. The electronic density of states analysis showed strong orbital hybridization between the nitro group and metal-doped graphene. The calculation indicated that the metal-doped graphene was sensitive to the tyrosine nitration, thus suggesting the potential application of metal-doped graphene for PTN detection.     

Preparation of large-sized graphene from needle coke and the adsorption for malachite green with its graphene oxide

With needle coke (NC) as an initial material, large-sized graphene was successfully prepared through an oxidation–exfoliation–thermal reduction process. The prepared graphene was characterized by SEM, TEM, AFM, FTIR, XRD, Raman, and XPS, respectively. Results showed that the morphology of graphene from NC was different from that of natural graphite although the spectroscopic properties of graphene from NC are very similar to those from natural graphite. The lateral size of the prepared graphene is concentrated in 3–8?µm, which was considerably larger than that of natural graphite, multiwalled carbon nanotubes (MWCNTs) and stacked graphene nanofibers (SGNFs). In addition, the adsorption capacity of graphene oxide from NC for malachite green was investigated to confirm the size of graphene indirectly. The equilibrium adsorption capacity of 437.7?mg/g for malachite green was considerably higher than that from natural graphite whose adsorption capacity was 209.5?mg/g under identical conditions. All results confirm that NC is a better alternative for the preparation of graphene than natural graphite.     

Adsorption of gas molecules on transition metal embedded graphene: a search for high-performance graphene-based catalysts and gas sensors

We report an investigation on the adsorption of small gas molecules (O(2), CO, NO(2) and NH(3)) on pristine and various transition metal embedded graphene samples using a first-principles approach based on density-functional theory (DFT). The most stable adsorption geometry, energy, charge transfer, and magnetic moment of these molecules on graphene embedded with different transition metal elements are thoroughly discussed. Our calculations found that embedded transition metal elements in general can significantly enhance the interactions between gas molecules and graphene, and for applications of graphene-based catalysis, Ti and Au may be the best choices among all transition metal elements. We also expect a detailed analysis of the electronic structures and magnetic properties of these systems to shed light on future applications of graphene-based gas sensing and spintronics.     

Large-area nanopatterned graphene for ultrasensitive gas sensing

Chemical vapor deposited （CVD） graphene is nanopatterned using a spherical block copolymer etch mask. The use of spherical rather than cylindrical block copolymers allows homogeneous patterning of cm-scale areas without any substrate surface treatment. Raman spectroscopy was used to study the con- trolled generation of point defects in the graphene lattice with increasing etching time, confirming that alongside the nanomesh patterning, the nanopatterned CVD graphene presents a high defect density between the mesh holes. The nanopatterned samples showed sensitivities for NO2 of more than one order of magnitude higher than for non-patterned graphene. NO2 concentrations as low as 300 ppt were detected with an ultimate detection limit of tens of ppt. This is the smallest value reported so far for non-UV illuminated graphene chemiresistive NO2 gas sensors. The dramatic improvement in the gas sensitivity is believed to be due to the high adsorption site density, thanks to the combination of edge sites and point defect sites. This work opens the possibility of large area fabrication of nanopatterned graphene with extremely high densities of adsorption sites for sensing applications.