铂掺杂氮化硼纳米管及CO在其表面的吸附行为的理论研究

采用基于密度泛函理论的PBEPBE方法对铂(Pt)掺杂的氮化硼(BN)纳米管进行了理论研究. 计算结果表明, Pt原子突出BN纳米管表面, Pt的d轨道暴露到外面, 使它更容易和外来分子发生相互作用, 提高了纳米管的反应活性. Pt取代掺杂缩小了纳米管的能隙, 从而提高BN纳米管的导电性. 一氧化碳(CO)在Pt掺杂BN纳米管上的吸附行为表明, 2个CO能化学吸附到纳米管表面, 更多的CO分子吸附是物理吸附.     

Theoretical Study of Adsorption Behavior of Vemurafenib Drug over BNNT(5,5-9) as a Factor of Drug Delivery: a DFT Study

In this research, a density functional theory(DFT) calculation was performed for investigation adsorption behavior of the anticancer drug Vemurafenib on BNNT(5,5-9) by using the M06-2X/6-31 G* level of theory in the solvent water. The electronic spectra of the Vemurafenib drug, BNNT(5,5-9) and complex BNNT(5,5-9)/Vemurafenib in solvent water were calculated by Time Dependent Density Functional Theory(TD-DFT) for the study of adsorption effect. The non-bonded interaction effects of the Vemurafenib drug with BNNT(5,5-9) on the electronic properties, natural charges and chemical shift tensors have been also detected. The results display the change in title parameters after process adsorption. According to the natural bond orbital(NBO) results, the molecule Vemurafenib and BNNT(5,5-9) play as both electron donor and acceptor at the complex BNNT(5,5-9)/Vemurafenib. On the other hand, the charge transfer occurs between the bonding, antibonding or nonbonding orbitals in two molecules drug and BNNT. As a consequence, BNNT(5,5-9) can be considered as a drug delivery system for the transportation of Vemurafenib as anticancer drug within the biological systems.     

Water phase transition induced by a Stone-Wales defect in a boron nitride nanotube

Boron nitride nanotubes (BNNTs) have been reported to possess superior water permeation properties. In this work, using molecular dynamics simulations with partial charges, capturing BNNT polarization effects obtained from quantum calculations, we found that Stone-Wales (SW) defects in a (5,5) BNNT result in phase transition of water, i.e., a transition between liquid-like phase and vapor-like phase was observed. The 90 degree rotation of the B-N bond, SW transformation, in an SW-defective (5,5) BNNT results in breaking of hydrogen bonding with neighboring water molecules and leads to the existence of a vapor-like phase near the SW defect. Water transport rate was evaluated by measuring translocation time. Water in an SW-defective (5,5) BNNT has fewer translocation events, longer translocation time, and a higher axial diffusion coefficient compared to water in a nondefective (5,5) BNNT.     

杂原子掺杂的含单空位缺陷BN纳米管的非线性光学性质

采用密度泛函理论(DFT)研究了杂原子M(M=Li, Na, K, Be, Mg, Ca, C和Si)在B/N单空位缺陷处的掺杂对(6,0)BN纳米管体系非线性光学性质的影响. 采用B3LYP方法共得到了14种几何构型, 并采用BHandHLYP方法计算了这些结构的第一超极化率β₀值. 研究结果表明, 单纯的B或N缺陷几乎不影响BN纳米管体系的非线性光学性质; 与B缺陷处掺杂的体系相比, 杂原子在N缺陷处的掺杂更有利于提高BN纳米管体系的第一超极化率β₀值; 对于同周期掺杂原子, 还原性越强的原子掺杂对BN纳米管体系的第一超极化率β₀值的改善越明显, 表现为β₀(Ⅰ族)>β₀(Ⅱ族)>β₀(Ⅳ族); 对比同主族掺杂原子, 第三周期元素Na和Mg的掺杂能更有效地提高体系的第一超极化率β₀值, 原因主要在于原子半径和还原性等因素共同决定其对BN纳米管体系第一超极化率β₀值的改善程度. 本文研究结果为有效提高BN纳米管体系的非线性光学性质提供了一种新思路, 为基于BN纳米管的非线性光学材料设计提供了有价值的理论信息.     

A combined ab initio/Franck-Condon study of the A-X single-vibronic-level emission spectrum of CCl2 and the photodetachment spectrum of CCl2 -.

State-of-the-art ab initio calculations have been carried out on the X1A1, ?3B1 and A1B1 states of CCl2 and the X2B1 state of CCl2-. Franck-Condon factors including anharmonicity have been calculated, between the CCl2 states, and between the CCl2- X2B1 state and the CCl2 states. They are used to simulate the A-X single-vibronic-level (SVL) emission spectra of CCl2 determined by M.-L. Lui et al. [PCCP 2003, 5, 352] and the 364 nm laser photodetachment spectrum of CCl2- obtained by R. L. Schwartz et al. [J. Phys. Chem. A 1999, 103, 8213]. Comparison between simulated and observed spectra confirms the vibrational assignments of the X2B1 SVL emission spectra and the T0 position of the A1B1 state of CCl2. For the photodetachment spectrum of CCl2-, spectral simulation shows that the higher binding energy ?3B1(CCl2) <-- X2B1(CCl2-) band is well separated from the X1A1(CCl2) <-- X2B1(CCl2-) band. It is concluded that the observed second band, which overlaps heavily with the X1A1(CCl2) <-- X2B1(CCl2-) band in the photodetachment spectrum of CCl2- cannot be assigned to the CCl2(?3B1) + e --> CCl2-(X2B1) detachment process. Further ab initio calculations carried out in the present investigation support the suggestion that the second band in the 364 nm photodetachment spectrum of CCl2- is due to detachment from an excited state of CCl2-, a linear quartet state, to a triplet state of CCl2. These calculations identify the anionic state to be the lowest 4Sigmag- (4Sigma-) state, which photodetaches vertically to the 3Sigmag- (3Sigma-; adiabatically ?3B1) and/or 3Pi(u) (3Pi) states of CCl2 to give the second band observed in the 364 nm photodetachment spectrum of CCl2-.     

氮化硼纳米管气敏特性的理论研究

采用密度泛函理论计算研究了氮化硼纳米管及碳掺杂氮化硼纳米管对CH4, CO2, H2, H2O, N2, NH3, NO2, O2, F2等十余种气体小分子的气敏特性. 研究结果表明: 氮化硼纳米管对CH4, CO2, H2, H2O, N2, NH3等气体分子不敏感, 而对O2, NO2, F2等气体分子比较敏感. 虽然碳掺杂氮化硼纳米管可以明显地改变其表面的化学反应活性, 增强了气体分子与氮化硼纳米管之间的相互作用, 但是并不能明显地改变其对所研究气体分子的敏感性.     

Interaction of vitamins A,B1, C,B3 and D with zigzag and armchair boron nitride nanotubes: A DFT study

In this work, based on the density functional theory, the interaction of vitamins A, B1, C, B3 and D with (5, 5) armchair and (9, 0) zigzag single-walled boron nitride nanotubes (BNNTs) are studied. It is found that binding of vitamins A, B1, C, B3 and D with (9, 0) and (5, 5) BNNTs is thermodynamically favorable. Calculated solvation energies show that the solubility of functionalized (9, 0) BNNTs is higher than that of functionalized (5, 5) BNNT, and both dissolutions in water are spontaneous. The results showed that BNNTs can act as a suitable drug delivery vehicle for vitamins A, B1, C, B3 and D within biological systems. This study may provide a new insight into the development of the functionalized boron nitride nanotubes as drug delivery systems for virtual applications.     

Single‐wall Boron Nitride Nanotube with Various Diameters under the Influence of Electric Field,A Computational Investigation

Structural and electrical response of the (4, 0), (5, 0) and (6, 0) zigzag model of single‐walled boron nitride nanotube (BNNT) with H‐terminated at the open ended, have been investigated under the external electric field (EF) with intensities 0–1.6 × 10^?2 a.u. using the DFT B3LYP/6‐31G* level of theory. Results of this study show that with increasing BNNTs diameter, the HOMO‐LUMO gap (HLG) values increase, and with increasing the EF intensity, the HLG values decrease. In both cases with increasing EF intensity and the BNNT diameters, the electric dipole moment is increased significantly. Also the calculated natural bond orbital (NBO) atomic charges on the atoms of the BNNT show that the separation of the center of the positive and the center of the negative electric charges of the boron nitride nanotubes are increases in both case. We have found that the properties of the BNNTs are dependent on their diameters and can be tuned by applied electric fields intensity.     

Electronic structure of octagonal boron nitride nanotubes

The effect of an octagonal lattice configuration on a boron nitride nanotube is explored using first principle calculations. Calculations show that the formational energy of an octagonal boron nitride nanotube (o‐BNNT) is an exothermic reaction. Boron and nitrogen atoms within an o‐BNNT have an average of 2.88 electrons and 9.09 electrons, respectively, indicating ionic‐like bonding. In addition, the electronic structure of the octagonal boron nitride nanotube shows semiconductive properties, while h‐BNNT is reported to be an insulator. Additional o‐BNNTs with varying diameters are calculated where the results suggest that the diameter has an effect on the binding energy and bandgap of the o‐BNNT. The defect sites of the o‐BNNT are reactive against hydrogen where a boron defect is particularly reactive. Thus, this work suggests that physical and chemical properties of a boron nitride nanotube can be tailored and tuned by controlling the lattice configuration of the nanotube.     

A computational investigation of the reactions of methylene, chlorocarbene, and dichlorocarbene with cyclopropane

The reactions of CH(2), CHCl, and CCl(2) with cyclopropane, 1, have been examined computationally. In all cases the lowest energy reaction between the carbene and 1 is predicted to be C-H insertion. In the reaction of CH(2) with 1, the transition state for C-C insertion leading to cyclobutane is 1.7 kcal/mol higher in enthalpy than the transition state for C-H insertion at the G3B3 level. A pathway higher in energy than C-H insertion in the reactions of CHCl and CCl(2) with 1 involves two-bond cleavages generating ethylene along with chloro and dichloroethylene, respectively.     

Geometries and stabilities of transition metals doped perfect and Stone–Wales defective armchair (5,5) boron nitride nanotubes

The binding abilities of transition metals (TMs) (TMs?=?Ni, Pd, and Pt) on perfect and Stone?CWales (SW) defective armchair (5,5) single-walled boron nitride nanotubes (BNNTs) were investigated using density functional theory method at the B3LYP/LanL2DZ level. The geometrical parameters and electronic properties of all BNNTs doped with TM atoms are reported. The strongest binding energy of Ni doped on SW defective BNNT of ?91.87?kcal/mol was found. The binding abilities of the most stable of TMs on the BNNTs are in order: Ni/SW2?CBNNT(Z_N)?>?Pt/SW2?CBNNT(Z_B)?>?Pd/SW2?CBNNT(Z_B). In all case, energy gaps of MTs doped perfect and defective BNNTs are obviously lower than their undoped nanotubes.     

分子束技术研究Ba与CHCl~3, CCl~4的反应

本文分别在交叉分子束和分子束-气体条件下, 利用化学发光方法, 研究了Ba(^3D)+CH~2Cl~2, CHCl~3,CCl~4和Ca(^1S~O),Ca(^3P),Ba(^1S～O)Ba(^3D)+CCl~4的反应, 实验得出了Ba(^3D)与CH~2Cl~2, CHCL~3, CCl~4反应时, A^2II,B~2Σ^+态BACl产物的发光截面对反应物碰撞能的依赖关系和反应阈能, 以及Ba(^3D)与CCl~4反应时, 产生电子激发态BaCl产物的光子产率。发现当Ba,Ca被激发到亚稳态时, Ba+CCl~4的反应电子基态BaCl产物的振动激发增加; 而Ca+CCl~4的反应电子基态CaCl产物的转动激发增加. 并针对以上结果进行分析讨论。     

Addition of carbenes to the sidewalls of single-walled carbon nanotubes

The addition of carbenes CX(2) (X=H, Cl) to single-walled carbon nanotubes (SWNTs) was investigated by density functional theory and finite, hydrogen-terminated nanotube clusters or periodic boundary conditions in conjunction with basis sets of up to polarized triple-zeta quality. For armchair [(3,3) to (12,12)] and zigzag tubes [(3,0) to (18,0)], reaction of CH(2) with the C--C bond oriented along the tube axis (A) is less exothermic than with those C--C bonds having circumferential (C) orientation. This preference decreases monotonically with increasing tube diameter for armchair, but not for zigzag tubes; here, tubes with small band gaps have a very low preference for circumferential addition. Axial addition results in cyclopropane products, while circumferential addition produces "open" structures for both armchair and zigzag tubes. The barriers for addition of dichlorocarbene to a (5,5) SWNT, studied for a finite C(90)H(20) cluster, are higher than that for addition to C(60), in spite of similar diameters of the carbon materials. Whereas addition of CCl(2) to [60]fullerene proceeds in a concerted fashion, addition to a (5,5) armchair SWNT is predicted to occur stepwise and involve a diradicaloid intermediate according to B3LYP, PBE, and GVB-PP computations. Addition to C bonds of (5,5) armchair tubes resulting in the thermodynamically more stable insertion products is kinetically less favorable than that to A bonds yielding cyclopropane derivatives.     

CCl2(A^1B1)自由基不同振动态的猝灭动力学

对CCl4/Ar混合气体直流脉冲放电产生CCl2自由基，再分别用波长为550.56nm,541.52nm,532.25nm,524.31nm,523.82nm和523.27nm的激光将电子基态CCl2激励到激发态A^1B1的(0,3,0),(0,4,0),(1,3,0),(0,6,0),(1,4,0),(2,2,0)振动态，激发态CCl2(A^1B1)的不同振动态的时间分辨荧光信号显示该信号呈双指数衰减，测得室温下CCl2(A^1B1)不同振动态被NH3,H2O,CH2Br2,NH(CH3)2,NH(C2H5)2,N(C2H5)3,n-C6H14等分子猝灭的实验结果，用三能级模型分析处理实验数据，获得态分辨速率常数kA和ka值，并对实验结果进行了讨论。     

Nitrogen monoxide storage and sensing applications of transition metal–doped boron nitride nanotubes: a DFT investigation

The structural properties, electronic properties, and adsorption abilities for nitrogen monoxide (NO) molecule adsorption on pristine and transition metal (TM = V, Cr, Mn, Nb, Mo, Tc, Ta, W, and Re) doping on B or N site of armchair (5,5) single-walled boron nitride nanotube (BNNT) were investigated using the density functional theory method. The binding energies of TM-doped BNNTs reveal that the Mo atom doping exhibits the strongest binding ability with BNNT. In addition, the NO molecule weakly interacts with the pristine BNNT, whereas it has a strong adsorption ability on TM-doped BNNTs. The increase in the adsorption ability of NO molecule onto the TM-doped BNNTs is due to the geometrical deformation on TM doping site and the charge transfer between TM-doped BNNTs and NO molecule. Moreover, a significant decrease in energy gap of the BNNT after TM doping is expected to be an available strategy for improving its electrical conductivity. These observations suggest that NO adsorption and sensing ability of BNNT could be greatly improved by introducing appropriate TM dopant. Therefore, TM-doped BNNTs may be a useful guidance to be storage and sensing materials for the detection of NO molecule.

     

CCl2(A1B1和a3B1)被酮类分子猝灭速率常数的测定

对CCl4/Ar混合气体脉冲直流高压放电产生CCl2自由基,经过约110μs后,再用541.52mm激光将电子基态CC2激励到激发态A1B1(0,4,0)振动态K=0能级上,通过检测激发态CCl2(A)时间分辨荧光信号,测得室温下CC2(A1B1和a3B1)被酮类分子猝灭的实验结果,用所提出的三能级模型分析处理实验数据,获得态分辨速率常数KA和Ka值.     

The singlet-triplet separation in CF2: state-of-the-art ab initio calculations and Franck-Condon simulations including anharmonicity.

Geometrical parameters, vibrational frequencies and relative electronic energies of the X2B1 state of CF2- and the X1A1 and ?3B1 states of CF2 have been calculated. Core-electron effects on the computed minimum-energy geometries and relative electronic energies have been investigated, and relativistic contributions to the computed relative electronic energies calculated. Potential energy functions of the X2B1 state of CF2- and the X1A1 and ?3B1 states of CF2 have been determined, and anharmonic vibrational wavefunctions of these states calculated variationally. Franck-Condon factors including anharmonicity and Duschinsky rotation have been computed and used to simulate the ?-X emission spectrum of CF2 determined by S. Koda [Chem. Phys. Lett. 1978, 55, 353] and the 364 nm laser photodetachment spectrum of CF2- obtained by R. L. Schwartz et al. [J. Phys. Chem. A 1999, 103, 8213]. Comparison between theory and experiment shows that the theoretical approach benchmarked in the present study is able to give highly reliable positions for the CF2(X1A1) + e <-- CF2-(X2B1) and CF2(?3B1) + e <-- CF2-(X2B1) bands in the photoelectron spectrum of CF2- and a reliable singlet-triplet gap for CF2. It is therefore concluded that the same theoretical approach should give reliable simulated CCl2(X1A1) + e <-- CCl2-(X2B1) and CCl2(?3B1) + e <-- CCl2-(X2B1) bands in the photodetachment spectrum of CCl2- and a reliable singlet-triplet gap for CCl2.     

CCl2自由基被无机小分子猝灭的速率常数

对CCl4/Ar混合气体脉冲直流高压放电产生CCl2自由基,用541.52 nm激光将电子基态CCl2激励到A 1B1(0,4,0)振动能级上. 通过检测激发态CCl2时间分辨荧光信号,测得室温下CCl2(A 1B1和a 3B1)被O2、N2、NO、 CO2、 CS2、H2O、SO2,和SF6分子猝灭的实验结果.用我们提出的三能级模型分析处理实验数据,获得了CCl2(A 1B1)态和CCl2(a 3B1)态的碰撞猝灭速率常数kA和ka值.     

CCl_2(A~1B_1,a~3B_1)自由基被烷烃类分子猝灭动力学

用放电- LIF实验装置 ,对 CCl4/Ar混合气体放电产生 CCl_2自由基 ,再用 541.52 nm激光将电子基态 CCl_2激励到激发态 A~B_1(0,4,0)振动能级上 ,通过检测激发态 CCl_2时间分辨荧光信号 ,测得室温下 CCl_2(A~B_1)被烷烃类分子猝灭的实验结果 ,用我们提出的三能级模型分析处理实验数据 ,获得 CCl_2(A~1B_1)态和 CCl_2(a~3B_1)态的碰撞猝灭速率常数 k_A和 k_a值 .     

钴掺杂氮化硼纳米管吸附氯酚类污染物的理论研究

氯酚(CPs)类污染物是形成持久性有机污染物二噁英的先驱物, 具有较强的致畸、致癌和致突变性. 为探索去除或检测这类污染物的新型材料, 应用密度泛函理论研究了(8,0)单壁氮化硼纳米管(BNNT)和Co掺杂的(8,0)单壁氮化硼纳米管(Co-BNNT)对2-氯酚(2-CP)、2,4,6-三氯酚(TCP)、五氯酚(PCP)的吸附行为及作用机制. 结果表明, 与BNNT相比, Co-BNNT费米能级附近出现杂化态, 带隙明显减小. BNNT对2-CP、TCP和PCP呈现物理吸附, 而Co-BNNT对三种氯酚则是化学吸附, 纳米管与分子间发生了明显的电荷转移, 体系态密度在费米能级附近发生了明显变化. Co原子掺杂明显增强了BNNT的电子输运能力, 提高了纳米管对氯酚的吸附活性. Co-BNNT有望是去除或检测氯酚类污染物的潜在资源.