官能团对分子器件电输运特性的影响

以4,4′-二巯基联苯分子为研究对象,利用第一性原理计算方法和非平衡格林函数理论,研究了官能团氨基和硝基对分子的电子结构以及分子结电输运性质的影响. 计算结果表明,在分子的不同位置添加同一类官能团氨基会使分子的电子结构发生变化,从而影响分子结的电输运性质. 而在分子的同一位置添加不同类型的官能团氨基和硝基则对分子间的相互作用有着显著影响,会使分子发生转动,从而改变分子的几何结构和电子结构,影响分子结的电输运特性. 并且发现随着分子的转动,添加官能团硝基时分子会呈现出记忆功能. 关键词： 官能团 电子输运 分子电子学     

金属银离子与四氯二苯并对二恶英相互作用及其表面增强拉曼光谱的研究

本文基于DFT方法计算了2,3,7,8-四氯二苯并对二恶英(2,3,7,8-TCDD)结构和振动性质。为了考察分子与金属表面的吸附和相互作用,建立了两种金属银离子与2,3,7,8-TCDD分子的复合体系,计算了它们的分子结构、电子结构和振动性质。基于计算结果详细分析了结构的变化、金属离子与分子中不同原子之间的相互作用;另外,根据不同体系拉曼散射强度的变化,对拉曼强度变化较大的特征振动进行了分析和讨论。文中给出的计算结果可用于指导相应的实验研究。     

官能团对芳烃体系电学特性的影响

以联苯分子为研究对象,利用密度泛函理论和弹性散射格林函数方法,研究了不同官能团对分子的电子结构以及分子结电输运性质的影响.计算结果表明在分子中的同一位置添加不同的官能团时,会使分子的几何结构和电子结构发生变化,从而影响分子结的电输运性质.     

官能团对芳烃体系电学特性的影响

以联苯分子为研究对象,利用密度泛函理论和弹性散射格林函数方法,研究了不同官能团对分子的电子结构以及分子结电输运性质的影响.计算结果表明在分子中的同一位置添加不同的官能团时,会使分子的几何结构和电子结构发生变化,从而影响分子结的电输运性质.     

二维Ti_2CO_2单层吸附H_2S分子的第一性原理研究

采用第一性原理计算方法研究了H_2S分子在二维单层Ti_2CO_2表面上的吸附以及外加应变和电场对其性质的调制,发现该吸附为物理吸附,其吸附强度几乎不受外加拉伸应变的影响,而外加电场使H_2S分子的吸附增强.同时,通过单层Ti_2CO_2表面不同结构(如水分子修饰、官能团掺杂、氧官能团空位)对H_2S分子吸附性质影响的研究表明:(1)表面吸附的水分子促进H_2S分子的吸附,其吸附强度随H_2O分子数增多而增强;(2)官能团OH掺杂浓度低于0.22 ML时,促进H_2S分子的吸附,而较高浓度OH掺杂使H_2S分子吸附减弱;官能团F掺杂对H_2S分子吸附强度几乎没有影响;(3)含氧空位的Ti_2CO_2表面与H_2S分子相互作用较强,吸附能高达-1.06 eV,且电子结构改变明显.     

远程作用对晶体生长的影响——Monte-Carlo模拟

本文推导了在考虑了分子与分子、离子与离子之间远程相互作用时,不同情况下的动力学常数普遍表达式;并用计算机模拟方法模拟了不同情况下的界面形貌和生长速度。结果表明,即使对以范德瓦耳斯力相互作用的分子晶体,长程相互作用也是不能忽略的;对于AB型离子晶体,则必须考虑长程相互作用。为了解决对长程相互作用的计算困难,我们采用了中性组合法。     

功能纳米结构可控生长的新途径：非模板选择性自组装

文章介绍了一种非模板选择性自组装纳米结构的方法.从实验和理论上研究了两种有机分子在Ag单晶不同表面上的吸附行为,发现在Ag（775）基底上PTCDA分子会完全吸附在（111）台阶面上,而DMe-DCNQI分子则完全吸附在（221）台阶面上.该研究还阐明了PTCDA分子与基底原子之间的相互作用机制,提出了PTCDA与基底之间的相互作用是通过分子末端官能团的氧原子实现的,中心的π共轭区域与基底相排斥,理论模拟得到的氧原子的NIXSW相干长度以及碳原子的近边X射线吸收谱与实验结果符合得较好.     

功能纳米结构可控生长的新途径:非模板选择性自组装

文章介绍了一种非模板选择性自组装纳米结构的方法.从实验和理论上研究了两种有机分子在Ag单晶不同表面上的吸附行为,发现在Ag（775）基底上PTCDA分子会完全吸附在（111）台阶面上,而DMe-DCNQI分子则完全吸附在（221）台阶面上.该研究还阐明了PTCDA分子与基底原子之间的相互作用机制,提出了PTCDA与基底之间的相互作用是通过分子末端官能团的氧原子实现的,中心的π共轭区域与基底相排斥,理论模拟得到的氧原子的NIXSW相干长度以及碳原子的近边X射线吸收谱与实验结果符合得较好.     

C60分子之间相互作用势的Kihara形式

根据Ｃ６０－晶体的升华焓，晶包参数和压缩系数，求得了Ｃ６０分子之间相互作用势的Ｋｉｈａｒａ形式，并且讨论了简单的Ｌｅｎｎａｒｄ－Ｊｏｎｅｓ势不能很好地描述Ｃ６０分子之间的相互作用。根据Ｃ６０分子之间相互作用势的Ｋｉｈａｒａ形式，计算了不同Ｃ６０晶型的某些性质，讨论了Ｃ６０晶体不同晶型的稳定性问题。     

分子和金表面相互作用的第一性原理研究

硫氢官能团可以很强地吸附于金表面上,从而可作为连接体用于纳米电子学中的分子器件.从第一性原理出发利用密度泛函理论研究了4,4′二巯基联苯分子和金表面的相互作用,并利用了前线轨道理论和微扰理论定量地确定了该相互作用能常数.计算结果表明,当含有硫氢官能团的有机分子化学吸附于金表面时,硫原子将与金原子形成以共价键为主的混和键,此时一些分子轨道扩展于金原子和有机分子中,这些轨道为分子结中电子的输运提供了通道,从而可使分子线的电导呈现出欧姆特性.而其他分子轨道具有局域性,此时电子的输运只能通过隧道效应来实现. 关键词： 化学吸附 分子线 分子电子学     

Structure and spectral properties of truxene dye <Emphasis Type="Italic">S</Emphasis>5

On the ground of functional theory with the B3LYP and BMK functionals, we have studied the structure and optical properties of a truxene dye sensitizer S5 for photoelectric transducers. Based on the calculations of the vertical excitations energy of the dye molecule and accounting the influence of the solvent, we have revealed a positive solvatochromic effect that is weak compared to results obtained in the vacuum approximation. We have studied new features describing stabilization of the planar structure of the cyanothiophene-acrylic fragment of the S5 dye.     

Environmentally friendly surface modification of silk fiber: Chitosan grafting and dyeing

In this paper, the surface modification of silk fiber using anhydrides to graft the polysaccharide chitosan and dyeing ability of the grafted silk were studied. Silk fiber was degummed and acylated with two anhydrides, succinic anhydride (SA) and phthalic anhydride (PA), in different solvents (dimethyl sulfoxide (DMSO) and N,N-dimethyl formamide (DMF)). The effects of anhydrides, solvents, anhydride concentration, liquor ratio (L:R) and reaction time on acylation of silk were studied. The polysaccharide chitosan was grafted to the acylated silk fiber and dyed by acid dye (Acid Black NB.B). The effects of pH, chitosan concentration, and reaction time on chitosan grafting of acylated silk were investigated. The physical properties show sensible changes regardless of weight gain. Scanning electron microscopy (SEM) analysis showed the presence of foreign materials firmly attached to the surface of silk. FTIR spectroscopy provided evidence that chitosan was grafted onto the acylated silk through the formation of new covalent bonds. The dyeing of the chitosan grafted-acylated silk fiber indicated the higher dye ability in comparison to the acylated and degummed silk samples. The mechanism of chitosan grafting over degummed silk through anhydride linkage was proposed. The findings of this research support the potential production of new environmentally friendly textile fibers. It is worthwhile to mention that the grafted samples have antibacterial potential due to the antibacterial property of chitosan molecules.     

Synthesis and spectroscopic characterization of Kiton Red-620 dye doped silica gel rods

The work was carried out to achieve two different but interdependent objectives; one to synthesis a transparent silica matrix with enough strength and thermal stability, by sol–gel technique, to host an organic dye molecule without quenching its fluorescence and two to find the probability if the said material is suitable for the construction of solid state dye lasers. Crack-free transparent silica gel rods with good mechanical strength, thermal stability and dimensions were successfully synthesized by sol–gel techniques. The rods were doped with Kiton Red-620 dye in different concentration separately. Effect of various synthesis parameters like time, temperature and aging condition was extensively studied to obtain crack-free silica rods doped with dye. Optical properties of prepared rods were studied by FTIR, UV/VIS–NIR and fluorescence spectroscopy. It is observed that Kiton Red-620 dye doped silica gel rods show good fluorescence with sharp peaks in the visible range. Their UV–VIS spectrum indicates the absorption in visible range. Thermal stability of rods were studied by DSC/TGA methods. Eventually it is found that these dye doped silica gel materials explore the possibility for new solid-state dye laser materials.     

Special features of spectral and luminescent properties of squarilic dyes in polymer matrices

A study was made of spectral and luminescent properties of a squarilic dye on the basis of 1,3,3-trimethyl-3H-indoline in comparison with the cationic polymethine dye representing a derivative of the same heterocycle. The squarilic dye was introduced into polymer films of poly-N-epoxypropylcarbazole, which is capable of bearing photoproduced charges, and polystyrene, which lacks this ability. Luminescence spectra of films with different dye concentrations at temperatures of 4.2 and 300 K were studied. Spectral and luminescent properties of squarain in both types of polymers were found to be determined by the dye tendency to aggregation. For poly-N-epoxypropylcarbazole, this tendency is less pronounced than for polystyrene, which is associated with the enhancement of specific solvation of a bipolar squarain molecule by polar groups of poly-N-epoxypropylcarbazole. The structure with an angle between chromophore directions of 180° is shown to be the most likely spatial structure of associates. The advantage of this structure is that it is stabilized at both ends of bipolar molecules by electrostatic attractive forces between opposite charges.     

Fourier transform IR spectroscopic study of substituent effect in aromatic amino acids on the zwitterion–neutral molecule tautomeric equilibrium

Four aromatic amino acids (p-aminobenzoic, 4,6-diaminoisophthalic, o-aminobenzoic, and methylene-bis-anthranilic) were studied by FTIR spectroscopy. The first two molecules were found to exist in the solid phase exclusively in neutral form and the latter two in coexisting neutral and ionic forms. The shift of the tautomeric equilibrium from neutral molecule to zwitterion is determined by the character of substitution, molecular conformation, and the possibility of noncovalent bonds formed between the functional groups. The separation of charges becomes possible only if the conformers of the molecule include a structure with an OH….N intramolecular hydrogen bond. The proton is completely transferred from the acid group to the amino group when the strong intermolecular hydrogen bonds can stabilize the formed zwitterion. Otherwise, uncharged complexes with different degrees of proton transfer to the amino group are formed.     

Crystal growth,spectral, thermal and optical properties of an organic single crystal – Dye doped hippuric acid

A new organic dye doped hippuric acid (DHA) single crystals have been grown from aqueous solution of acetone by doping with rhodamine using slow evaporation technique. Rhodamine is a dye, an organic molecule well-studied in laser physics and nonlinear optics for its fluorescent properties. Dyeing of crystals is a practice that was developed particularly for quantum optical applications because of the very significant increase in surface area achieved in growing crystals. In the present work, The DHA single crystals were successfully grown by the slow evaporation method. Good quality single crystals were harvested after 5 days. The grown crystal was characterized by various techniques namely Single crystal X-ray diffraction, FT-IR, UV–vis, NLO and thermal analysis. The FT-IR analysis confirms the presence of various functional groups available in DHA. The optical transmission study and Kurtz and Perry SHG measurement shows the suitability of doped crystals for NLO applications.     

消逝波激励的双波段光纤回音壁模式激光辐射

将石英光纤浸入低折射率的染料溶液中后构成圆柱形微腔.采用轴向光抽运消逝波激励激光增益的方式,使增益区域局限在圆柱形微腔回音壁模式的模场区域内,由此显著地提高了抽运效率,增加了沿光纤轴向的增益长度.在一根石英光纤的轴向分段填入浓度同为2×10^-3mol/L的罗丹明6G和罗丹明B乙醇溶液,在567—576nm 和592—600nm的两个波长范围内同时获得回音壁模式的激光辐射;分段填入浓度为8×10^-4和8×10^-3mol/L的罗丹明B乙醇溶液, 关键词： 消逝波激励 圆柱形微腔 回音壁模式 双波段激光辐射     

Rapid wavelength scans over one octave and application to laser-induced fluorescence

Rapid excitation scans of laser-induced fluorescence (LIF) have been demonstrated. Broadband light was generated in a photonic crystal fiber and transmitted through a long fiber. Due to group-velocity dispersion in the long fiber, a wavelength scan emerged from the fiber in time. The wavelength was swept over approximately one octave in approximately 150 ns. The generated light was used to excite LD 700 Perchlorate diluted in methanol. The LIF excitation scan had a spectral resolution of approximately 15 nm, and the integrated fluorescence spectrum was found to be within 7% of the integrated absorption spectrum of the dye molecule. The method presented makes possible spatially and spectrally resolved LIF excitation scans with scanning speeds up to the limits set by the excited-state lifetime of the dye molecule.     

Christopher Longuet-Higgins, 1923 to 2004

The structure, harmonic vibrational frequencies, dissociation energies with respect to possible fragmentation pathways, dipole moment, natural bond orbital (NBO) partial atomic charges and time-dependent density functional theory (TD-DFT) excitation energies for the novel molecule periodane, FBeCNLiOB, and three structural analogues were computed using density functional theory (DFT). Two isoelectronic analogues (FBeCNLiNC and FBeBOLiOB) result from the replacement in periodane of the BO fragment with the CN fragment and vice versa, while the third, called hydroperiodane, is formed by replacing the F atom of periodane with a H atom. These three species are predicted to have a stable structural motif based on that of the theoretically predicted planar global minimum of the periodane molecule.     

Structure and spectral properties of triphenylamine dye functionalized with 3,4-propylenedioxythiophene

Based on the density functional theory with the B3LYP, BMK, and PBE1PBE hybrid functionals and 6?C31G(d) atomic-orbital basis set, the structure and electronic-spectral properties of a triphenylamine dye sensitizer for photoelectric converters that is functionalized with 3,4-propylenedioxythiophene have been studied. The nature of an intense color of the sensitizer is elucidated. The relation of the orbital structure of the first excited state to the mechanism by which the intensity and polarization of the visible absorption band are formed, as well as the electron injection efficiency into the conduction band of titanium oxide, are explained. In terms of the Bader theory, a complete analysis of the electron density distribution in the dye molecule under study has been performed and the role played by nonvalent interactions in its stabilization has been determined.