Effect of the calculation method and the basis set on the structure and electrical properties of (4,4) carbon nanotubes with different lengths and open ends

The structure and electrical properties of open carbon nanotube with chirality (4,4), consisting of 5-15 segments, are calculated within four quantum chemical models: AM1, PM3, LSDA/3-21G*, and B3LYP/6-31G. Size effects and the effect of the model choice on the geometry, energy, enthalpy and Gibbs energy of the formation (atomization), Mulliken atomic charges, polarizability, and predicted adsorption properties of nanotubes are discussed.     

The effect of surface curvature of aluminum nitride nanotubes on the adsorption of NH3

Our main objectives are to address the following fundamental issues: (1) A density functional theory study on the structural and electronic properties of the zigzag single-walled aluminum nitride nanotubes (AlNNTs) with various diameters, using B3LYP/6-31G* level of theory. (2) An ONIOM study on the curvature effect of AlNNTs on the NH₃ adsorption process using B3LYP/6-31G* and semiempirical AM1 approaches. Furthermore, a potential energy surface is calculated for NH₃ moving toward AlNNT surface. In contrast to semiconducting carbon nanotubes (Louie, Top Appl Phys 80:113, 2001) our calculations confirmed that the HOMO?CLUMO energy gap of AlNNTs increases with an increase of the tube diameter. Additionally, we showed that HOMO/LUMO interaction between NH₃ and AlNNTs becomes stronger as the tube diameter decreases.     

Adsorption properties of OCN radical on (6,0), (8,0), and (10,0) zigzag single-walled carbon nanotubes: a density functional study

Abstract  

The behavior of the OCN radical adsorbed on the external surface of H-capped (6,0), (8,0), and (10,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 98 suite of programs. We present the nature of the OCN radical–surface interaction in selected sites of the nanotubes. Binding energies corresponding to adsorption of the OCN radical are calculated to be in the range 280–315 kJ mol⁻¹. More efficient binding energies cannot be achieved by increasing the nanotube diameter. We also provide the effects of OCN radical adsorption on the electronic properties of the nanotubes.     

Adsorption properties of N<Subscript>2</Subscript>O on (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes: a density functional study

Abstract  

The behavior of N₂O adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the N₂O interaction in selected sites of the nanotubes. Binding energies corresponding to adsorption of the N₂O are calculated to be in the range 4–21 kJ mol⁻¹. More efficient binding energies cannot be achieved by increasing the nanotube diameter. We also provide the effects of N₂O adsorption on the electronic properties of the nanotubes.     

椅型碳纳米管吸附氧原子的密度泛函理论研究

利用密度泛函B3LYP对有限长扶手椅形单壁碳纳米管(3,3),(4,4)和(5,5)吸附O原子的几何结构、电子属性、反应能和红外光谱进行了系统地理论研究,获得了一些有意义的结果,主要包括如下4个方面:(1)2个O原子吸附在管外壁垂直于管轴的C—C键形成开环的轮烯结构,吸附在管内壁形成环氧结构;(2)O原子吸附在管外壁要比吸附在管内壁具有较大的能隙和吸附反应能;(3)与单壁碳纳米管管外壁吸附1个O原子相比,2个O原子吸附在管外壁具有较大的吸附反应能;(4)B3LYP得到的C—O伸缩振动频率与实验一致.     

NH3在硼纳米管表面吸附的密度泛函理论研究

利用密度泛函理论研究了NH₃在完整和含有缺陷的硼纳米管上的吸附行为以及相关电子性质. 计算结果表明, 对于α硼纳米管, 在不同的直径和手性条件下, NH₃均倾向于吸附在配位数为6的顶位上. 电子结构计算结果表明, NH₃能够吸附在纳米管表面主要是由于N和B原子产生了较强的相互作用. 表明硼纳米管是一种潜在的NH₃气气敏材料.     

功能化碳纳米管的电化学性质及在6-巯基嘌呤分析检测中的应用

采用修饰单壁碳纳米管(SWNT、SWNT-COOH或SWNT-OH)及多壁碳纳米管(MWNT、MWNT-COOH或MWNT-OH)的石墨电极研究配位阴离子[Fe(CN)6]3-和配位阳离子[Co(phen)3]3+的电化学行为与吸附性能,借助[Co(phen)3]3+在碳纳米管(CNT)的强吸附特性制备[Co(phen)3]3+/CNT/C修饰电极,以其应用于6-MP的分析检测.结果表明:1)在CNT修饰电极上[Fe(CN)6]3-/4-呈现很好的氧化还原可逆性,而[Co(phen)3]3+则显示明显的吸附控制特征.2)[Co(phen)3]3+在多壁碳纳米管修饰电极上的吸附量较单壁碳纳米管大,但经羧基化或羟基化后,吸附量减小,而且在羧基化表面的吸附量较羟基化的大.3)[Co(phen)3]3+与6-MP间存在明显的相互作用,其配位产物的还原峰电流与6-MP浓度呈线性关系.     

Adsorption properties of SCN? on (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes: a density functional study

Abstract  

The behavior of the thiocyanate anion (SCN⁻) adsorbed on the external surface of H-capped (6,0), (7,0), (8,0), and Al-doped (6,0) zigzag single-walled carbon nanotubes was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the SCN⁻ interaction in selected sites of the nanotubes. Our results show that the pristine carbon nanotubes cannot significantly detect SCN⁻. The calculated binding energy of the Al-doped (6,0) single-walled carbon nanotubes indicated that SCN⁻ can be adsorbed significantly on the C and Al sites and these nanotubes can therefore be used for SCN⁻ storage. Binding energies corresponding to adsorption of SCN⁻ on the Al site in the Al-doped (6,0) single-walled carbon nanotubes was calculated as −286.38 kJ mol⁻¹. The calculated binding energies for SCN⁻ in N-down orientation are higher than those in S-down orientation for all of the configurations. More efficient binding could not be achieved by increasing the nanotube diameter. We also report the effects of SCN⁻ adsorption on the electronic properties of the nanotubes.     

Property control of new forms of carbon materials by fluorination

Multiwall carbon nanotubes (MWNTs) based on the template carbonization technique were fluorinated in a temperature range 323-473 K by elemental fluorine. The fluorination of the carbon nanotubes results in functionalization and modification of pristine nanotubes with respect to adsorption and electrochemical properties. Selective fluorination of the inner surface of the carbon nanotubes, brings about a decrease in the surface free energy of the inner surface of the tubes and an increase in colombic efficiency of Li/nanotubes rechargeable cells in an aprotic medium. Electrochemical fluoride-ion doping of fullerene C₆₀ thin films (250-450 nm) was carried out in a fluoride-ion conductive solution, MeCN solution of 1 M Et₄NF·4HF. Galvanostatic oxidation yielded C₆₀F_ca.1-3 where fluorine exists as a semi-ionic species in the cavity surrounded by C₆₀ molecules without forming covalent CF bonds     

Fluoride and lead adsorption on carbon nanotubes

The properties and applications of CNT have been studied extensively since Iijima discovered them in 1991[1,2]. They have exceptional mechanical properties and unique electrical property, highly chemical stability and large specific surface area. Thus far, they have widely potential applications in many fields. They can be used as reinforcing materials in composites[3], field emissions[4], hydrogen storage[5], nanoelectronic components[6], catalyst supports[7], adsorption material and so on.…     

Adsorption of the nitrosamine and thionitrosamine molecules as carcinogen compounds on the BN and B3Al N nanotubes: A DFT study

DFT calculations were performed to investigation of the influence of doping three atoms of aluminum on the electronic properties of the (4,0) zigzag boron nitride nanotube (BNNT). Also, adsorption properties of nitrosamine (NA) and thionitrosamine (TNA) molecules as carcinogen agents onto BN and B_Al3N nanotubes were studied. The results show that the B_3AlN nanotube is the most energetically favorable candidates for adsorption of these molecules. Also, B(B_3Al)NNT/TNA complexes are more stable than B(B_3Al)NNT/NA complexes. The HOMO–LUMO gap, electronic chemical potential (μ), hardness (?), softness (S), the maximum amount of electronic charge (ΔN_max) and electrophilicity index (ω) for monomers and complexes in the gas and polar solvent phases were calculated. The results show that the conductivity and reactivity of BNNT increase by doping Al atoms instead of B atoms. Also, the interaction of NA and TNA molecules with BN and B_Al3N nanotubes results in significant changes in the electronic properties of nanotubes. Based on the natural bond orbital (NBO) analysis, in all complexes charge transfer occurs from NA and TNA molecules to nanotubes. Theory of atoms in molecules (AIM) was applied to characterize the nature of interactions in nanotubes. It is predicted that, BN and B_3AlN nanotubes can be used to as sensor for detection of NA and TNA molecules.     

碳纳米管负载氧化铝材料的制备及其吸附水中氟离子的研究

采用碳纳米管和硝酸铝制备了碳纳米管负载氧化铝新型除氟材料.X射线衍射检测发现,当焙烧温度低于850℃时,氧化铝为无定形态,当焙烧温度为1050℃时,氧化铝为α形态,扫描电子显微镜观察到碳纳米管与氧化铝均匀掺杂.同时用碳纳米管负载氧化铝复合材料进行水中氟离子的吸附研究,结果表明,该复合材料具有优良的除氟效能.氧化铝负载量为30%、焙烧温度为450℃条件下制备的碳纳米管负载氧化铝复合材料的吸附除氟能力是γ-氧化铝的2.0～3.5倍,与IRA-410聚合树脂的吸附除氟能力相当,适宜pH范围为5.0～9.0,吸附等温线符合Freundlich方程.     

Kinetics and thermodynamic study of aniline adsorption by multi-walled carbon nanotubes from aqueous solution

Multi-walled carbon nanotubes (MWCNTs) were used in the adsorptive removal of aniline, an organic pollutant, from an aqueous solution. It was found that carbon nanotubes with a higher specific surface area adsorbed and removed more aniline from an aqueous solution. The adsorption was dependent on factors, such as MWCNTs dosage, contact time, aniline concentration, solution pH and temperature. The adsorption study was analyzed kinetically, and the results revealed that the adsorption followed pseudo-second order kinetics with good correlation coefficients. In addition, it was found that the adsorption of aniline occurred in two consecutive steps, including the slow intra-particle diffusion of aniline molecules through the nanotubes. Various thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), were calculated. The results indicated that the spontaneity of the adsorption, exothermic nature of the adsorption and the decrease in the randomness reported as ΔG°, ΔH° and ΔS°, respectively, were all negative.     

中分子毒素在碳纳米管上的吸附

研究了两种不同形态的碳纳米管(随机生长多壁碳纳米管(MWCNTs)及定向生长多壁碳纳米管(ACNTs))对典型中分子毒素的吸附性能. 并与两种现有商用血液灌流吸附材料(活性炭(AC)及大孔吸附树脂(MR))进行了对比. 结果显示, 碳纳米管(CNTs)具有优异的中分子吸附能力, 其中MWCNTs对典型中分子毒素的吸附量可达47.18 mg·g-1, 为活性炭的10.8倍, 为大孔吸附树脂的5.5倍. 此外, 碳纳米管的吸附非常迅速, 中分子毒素在MWCNTs及ACNTs达到吸附平衡的时间仅为10 min和15 min, 而活性炭及大孔吸附树脂则分别需要60 min及120 min. 碳纳米管优异的吸附性能得益于其独特的微观结构所形成的发达的中孔. 因此, 碳纳米管可望成为高效的吸附材料, 应用于血液灌流中.     

胺类分子在LiMOR分子筛中吸附的量子化学研究

 采用量子化学方法(ONIOM,B3LYP/6-31G(d,p):HF/3-21G)研究了锂型丝光沸石(LiMOR)的结构及其对胺类分子的吸附性能. 在校正基组迭加误差的基础上计算得到氨、甲胺、二甲胺和三甲胺分子的吸附热分别为117.6,132.7,122.2和106.0 kJ/mol,表明胺分子在LiMOR分子筛上吸附强度的次序为三甲胺＜氨＜二甲胺＜甲胺. 通过结构优化得到了吸附复合物的平衡几何参数、电子结构数据以及N-H键伸缩振动频率,胺分子与分子筛之间的主要作用力为氮上的孤对电子和锂离子之间的静电作用力,胺分子与分子筛骨架氧之间的弱氢键作用对其吸附有一定的稳定作用.     

Studies of modified carbon nanotubes by means of thermogravimetry Q-TG and sorptometry techniques

The paper presents the physicochemical (adsorption and porosity) properties of closed carbon nanotubes, opened through the action of an oxidizing acid and modified with metal ions of nickel, cobalt, and iron/cobalt. The carbon nanotubes were prepared via the oxidation process by means of 65 % nitric acid and/or nickel and cobalt nitrates dissolved with 65 % nitric acid. Using special thermogravimetry Q-TG and sorptometry methods physicochemical properties of pure and modified nanotube surfaces were investigated. A numerical and analytical procedure for the evaluation of heterogeneous properties (adsorption capacity, statistical number of adsorbed liquid layers, desorption energy distribution functions) on the basis of liquid thermodesorption Q-TG from the sample surfaces under the quasi-equilibrium conditions are presented. The calculations of the specific surface areas, pore size and volume, and fractal dimensions of carbon nanotubes were made from sorptometry data.     

ZnCl2、KOH和HNO3改性MWCNT对苯酚的吸附行为研究

通过扫描电子显微镜、X射线衍射仪、N₂吸附分析仪及Boehm滴定法获得ZnCl₂、KOH和HNO₃化学处理对高纯多壁碳纳米管的结构和表面含氧官能团的影响,通过批处理实验考察吸附条件（吸附时间、初始浓度、温度）对处理前后的碳纳米管吸附苯酚行为的影响,并采用准一级、准二级、Evolich动力学模型和热力学方程拟合其吸附数据,分析其动力学行为、热力学行为和吸附机理。结果表明,虽然ZnCl₂、KOH和HNO₃化学处理法均未对碳纳米管BET比表面积产生显著影响,但会影响其表面化学性质（即,对于ZnCl₂和KOH化学处理降低表面羧基、内酯基含量和增大碱性官能团量,而对于HNO₃化学处理可以增大表面羧基、内酯基含量,而碱性官能团略有增加）;改性处理影响碳纳米管去除苯酚效率：由于ZnCl₂和KOH改性处理降低碳纳米管表面羧基量,故其提高了苯酚去除率,而HNO₃处理则略减小碳纳米管的苯酚去除率,可能是由于碳纳米管结构和表面化学性质共同影响所致;碳纳米管的苯酚去除率均随苯酚溶液初始浓度的增大而减小;高温不利于吸附;热力学研究发现碳纳米管吸附苯酚过程是自发的和放热的,属于物理吸附;动力学研究表明,吸附过程符合准二级动力学方程。通过ZnCl₂和KOH化学处理,可以显著提高碳纳米管对苯酚的吸附性能。     

1,3,5-三硝基苯在高岭石表面吸附的理论研究

构造了高岭石硅氧层和铝氧层的团簇模型(分别为Si₁₃O₃₇H₂₂和Al₆O₂₄H₃₀), 并分别在B3LYP/6-31G(d), MP2/6-31G(d)//B3LYP/6-31G(d)和B3LYP/6-311++G(d,p)//B3LYP/6-31G(d)理论水平上对1,3,5-三硝基苯(TNB)在高岭石表面的吸附性质(如优化的几何构型、 结构参数、 吸附能、 振动频率、 静电势和分子轨道等)进行了研究. 结果表明, TNB和硅氧层表面间的相互作用以静电和范德华相互作用为主; TNB与铝氧层间的相互作用以氢键为主, 且TNB和铝氧层间相互作用的能量更低, 结构更稳定.     

Functionalized mesoporous materials for adsorption and release of different drug molecules: A comparative study

The adsorption capacity and release properties of mesoporous materials for drug molecules can be improved by functionalizing their surfaces with judiciously chosen organic groups. Functionalized ordered mesoporous materials containing various types of organic groups via a co-condensation synthetic method from 15% organosilane and by post-grafting organosilanes onto a pre-made mesoporous silica were synthesized. Comparative studies of their adsorption and release properties for various model drug molecules were then conducted. Functional groups including 3-aminopropyl, 3-mercaptopropyl, vinyl, and secondary amine groups were used to functionalize the mesoporous materials while rhodamine 6G and ibuprofen were utilized to investigate the materials’ relative adsorption and release properties. The self-assembly of the mesoporous materials was carried out in the presence of cetyltrimethylammonium bromide (CTAB) surfactant, which produced MCM-41 type materials with pore diameters of ∼2.7-3.3 nm and moderate to high surface areas up to ∼1000 m²/g. The different functional groups introduced into the materials dictated their adsorption capacity and release properties. While mercaptopropyl and vinyl functionalized samples showed high adsorption capacity for rhodamine 6G, amine functionalized samples exhibited higher adsorption capacity for ibuprofen. While the diffusional release of ibuprofen was fitted on the Fickian diffusion model, the release of rhodamine 6G followed Super Case-II transport model.