Blue/red-shift of the p-Phenylene-ethynylene Oligomers Absorption Spectra

The absorption spectra of the p-phenylene-ethynylene(p-PPE) oligomers(up to n = 12) were estimated by DFT and TD-DFT methods. The effective conjugation length(ECL) of the corresponding polymer was obtained by extrapolating the first excitation energies of the oligmers to infinite chain length with an alternative exponential function. The absorption spectral red-shift mainly depends on the ?-conjugation segment of oligomers resulting from the planarization of the backbone. The excitation mechanism of the rotamer has been investigated sufficiently by analyzing the orbital density variation upon the conformational rotations around the cylindrical triple-bonded carbon which is believed to impact significantly on the optical spectrum. The calculated results further indicate that rotation about the cylindrical triple bond interrupts the conjugation of rod-like oligomers to lead an angle-dependence of the corresponding excitation energy. The results are helpful to interpret the conformational-dependent spectroscopic phenomena of p-phenyleneethynylene and derivatives oligomers and polymers observed in ensemble and single molecule spectroscopy.     

吸收光度法中的峰位移

该文从吸收干扰、单色光性质及被测物吸收特性改变三个方面探讨了吸收光度法中吸收峰位移的原因、影响及其消除与应用。重点论述了吸收干扰中的相长与相消干扰引起的吸收峰位移规律。该规律为研究试剂与溶剂中杂质、样品中共存物、反应试剂与产物等的吸收干扰引起被测吸收峰位置、高度及形状的变化提供了理论依据。运用被测物标准溶液的正、负吸光度吸收曲线提供的信息与吸收峰位移规律研究吸收光度法应用的新方法,为定量分析、消除共存物干扰、化学反应及试剂选择性等研究提供了新手段。作为峰的相长与相消干扰引起的测定峰位移规律也适用于检测峰的其它仪器分析。     

Cu/AAO纳米有序阵列复合结构的光吸收特性

采用电化学沉积工艺, 成功制备了铜/氧化铝(Cu/AAO)纳米有序阵列复合结构. 研究结果发现, 在λ为570 nm附近出现了明显的Cu表面等离子共振吸收峰, 且随Cu沉积量的增加, 吸收峰位稍有蓝移, 其强度逐渐增强, 峰形由宽变锐; 另外还发现, 该结构的吸收边随着Cu沉积量(或长径比)的增加大幅度红移, 可以实现在近紫外至近红外的大范围内移动, 最大频移量超过500 nm, 且Cu表面等离子振荡吸收峰会随着吸收边的大幅度红移被掩盖而逐渐消失. 对该结构光吸收边的调制机理进行了理论分析, 阐释了吸收峰逐渐消失的原因, 并从理论上定性地解释了导致吸收峰位蓝移及宽化的主要原因.     

疏水矿化棉纤维的制备及其油水分离性能

通过交替浸渍法(ASP)在天然棉纤维表面进行仿生矿化均匀地制备了碳酸钙涂层,并使用硬脂酸钠进一步对棉纤维/碳酸钙复合物进行表面疏水改性,得到了具有良好疏水性能的棉纤维材料.FTIR结果显示,碳酸钙与棉纤维之间以氢键结合.改性后的疏水棉纤维具有优异的吸附选择性,能够实现油水分离.改性棉纤维对多种油类均具有良好的吸附能力,对二甲基硅油和氯仿循环吸附30次后,吸附保持率仍可达到80%以上,表现出良好的重复使用性能.该疏水矿化棉纤维具有环境友好,成本低廉,制备方法简单等优势,在油水污染物处理方面具有潜在应用价值.     

树莓状超疏水多孔复合棉纤维的制备及油水分离性能

基于聚多巴胺（PDA）的化学性质和树莓状纳米粒子的粗糙结构,以聚多巴胺包覆的棉纤维为基底,制备了具有多重粗糙度的树莓状超疏水多孔复合棉纤维材料.通过扫描电子显微镜观察树莓状超疏水多孔复合棉纤维表面的微观形貌,PDA-SiO₂纳米粒子稳定地固定在聚多巴胺涂覆的棉纤维表面.经过氟化改性的树莓状超疏水多孔复合棉纤维具有超疏水性,水接触角为158.2°,油接触角为0°.油/水分离实验结果表明,树莓状超疏水多孔复合棉纤维对己烷/水混合物的分离效率可达99.4%以上,使用20次后仍维持较高的分离效率.同时,其具有较高的溶剂吸附能力（13~34 g/g）、重复使用性及机械稳定性,吸油能力可与硅气凝胶相媲美.     

多支结构的均三嗪衍生物的合成及双光子吸收性质

合成了3个系列各含有单支、双支和三支结构的9个均三嗪衍生物, 测定了它们的线性吸收和发射性质以及双光子吸收和发射性质. 随着三嗪环上侧链数目的增加, 线性吸收谱(吸收峰位于390～440 nm)、荧光谱(发射峰位于460～580 nm)和双光子荧光谱(激发波长800 nm)都发生红移; 各种光谱的强度逐渐增强; 基态与激发态的偶极矩之差Δμ_eg也逐渐增大. 另外, 从单支到三支结构, 双光子吸收截面σ随侧链数目呈非线性增加. 这表明多支结构的双光子吸收存在显著的增强效应.     

Absorption spectra of poly-N-vinylcarbazole derivatives by experiment and simulation

Geometry molecular optimization and quantum chemical simulations of absorption spectra for newly synthesized poly-N-vinylcarbazole derivatives were performed using a semi-empirical approach. The studied polymers were modified by changing the positions of the carbazole group with respect to the polymer backbone. The absorption spectra were calculated for different numbers of PNVK monomers. A sufficient agreement between the calculated and experimentally measured spectra was observed. A change of the red shift absorption with respect to the blue shift was observed for cases when the number of monomers was higher than 4. The theoretical simulations indicate that this behavior is a consequence of the specific molecular structure of the considered molecules. The results demonstrate the potential of combined simulation and experimental studies in materials engineering and searching of new electro-luminescent materials.     

多孔羰基铁/CoFe2O4/聚苯胺复合材料的制备及吸波机理

通过金属点蚀技术制备了表面多孔形貌的羰基铁粉（PCIP）,并采用共沉淀及原位聚合方法,将CoFe₂O₄与聚苯胺（PANI）负载于多孔羰基铁表面,得到具有电磁吸收性能的PCIP/CoFe₂O₄/PANI复合材料.通过扫描电子显微镜（SEM）、X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FTIR）、热重分析仪（TGA）及矢量网络分析仪（VNA）等对复合材料的形貌、成分和吸波性能进行了研究.结果表明,CoFe₂O₄/PANI团聚于PCIP表面,显著提升了复合材料电损耗能力,促进了低频电磁波的1/4波长干涉相消.当苯胺添加量为0.5 mL,复合材料在频率为5.7 GHz时,反射损耗达到-22.9 dB,低频吸波性能得到大幅提升.利用1/4波长干涉相消理论及电磁波界面反射模型对复合材料低频吸波性能提升的内在原因进行了分析.     

Absorption and emission spectra of fluorescent silica nanoparticles from TD-DFT/MM/PCM calculations

A multi-scale computational protocol, which combines Quantum Mechanics and Molecular Mechanics (QM/MM) calculations with the polarisable continuum model (PCM), has been used to study the tetramethylrhodamine isothiocyanate (TRITC) fluorophore, embedded in three different environments, namely in water, on an amorphous silica surface and covalently encapsulated in a silica nanoparticle (C dot). Absorption and emission spectra have been simulated by using TD-B3LYP/PCM calculations, performed on the TRITC ground and excited state geometries, optimized at the QM/MM level. The results are in good agreement with experimental data confirming the caging effect played by the silica shell on the mobility of the TRITC molecule when covalently encapsulated in silica nanoparticles. This could result in a decrease of the nonradiative decay rate and thus an increase of the quantum yield of the molecule.     

Absorption spectrophotometry

A review is given of the development of spectrophotometers from the earliest models to the latest microprocessor instruments with photodiode detection systems.     

Absorption spectra

The first band in the absorption spectra of the Z isomers of aurones, thioindogenides, and selenoindogenides is due to an electronic transition that is associated primarily with charge redistribution on the heteroatom and the carbonyl group. The effect of a substituent in the 4′ position plays a secondary role. The low sensitivity of the spectra of selenoindogenides to the effect of substituents is due to the saturation of the acceptor center (carbonyl group) by electrons drawn off from the heteroatom during interaction of the 2π _z electrons of selenium with the π system of the molecule.     

Femto/Picosecond Transient Absorption Study of Ring-Opening Dynamics in Perimidinespirocyclohexadienone Derivatives

The ring-opening dynamics of perimidinespirocyclohexadienone derivatives has been studied by means of time-resolved spectroscopy in cyclohexane and acetonitrile solutions. It has been established that molecular isomerisation leading to the open isomer occurs against the background of the S₁-S₀ internal conversion of the cyclic form. In addition, the features of the observed spectral changes in the cyclohexane made it possible to distinguish formation of the photoproduct in the T₁ state and its relaxation via intersystem crossing to the singlet ground state. The corresponding assignments for transient absorption bands were performed on the basis of TD-DFT calculations.     

基于静电吸附作用制备PPy/CNTs复合材料

通过添加十二烷基苯磺酸钠(SDBS), 在碳纳米管(CNTs)表面引入具有静电吸附作用的基团, 使吡咯单体附着于CNTs表面, 然后发生化学原位聚合, 得到了由片状聚吡咯(PPy)包覆CNTs所构成的PPy/CNTs复合材料, 开辟了一条易于工业化生产制备PPy/CNTs复合材料的途径. 所得材料和CNTs借助傅立叶变换红外光谱、扫描电子显微镜、透射电子显微镜等设备进行了成分和形貌的表征; 并将所得材料组装成电化学超级电容器, 进行了电化学性能测试. 研究结果表明, 加入SDBS后, 吡咯单体能很好地吸附于CNTs表面; CNTs的应用细化了PPy的颗粒, 改善了PPy的导电性能和机械性能, 使PPy/CNTs复合材料呈现出多孔状; 其电化学容量达到101.1 F·g-1(有机电解液), 是同样制备条件下所得纯PPy电化学容量(19.0 F·g-1)的5倍多, 约是所用纯CNTs电化学容量(25.0 F·g-1)的4倍.     

Synthesis and Microwave Absorption Properties of BaTiO3-polypyrrole Composite

BaTiO₃ powders are prepared by sol-gel method by cotton template. Polypyrrole is pre-pared by chemical oxidation route in the emulsion polymerization system. Then BaTiO₃-polypyrrole composites with different mixture ratios are prepared by as-prepared material.The structure, morphology, and properties of the composites are characterized with Infrared spectrum, X-ray diffraction, scanning electron microscope, and net-wok analyzer. The com-plex permittivity and reflection loss of the composites are measured at different microwave frequencies in S-band and C-band (0.03—6 GHz) employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO₃ to polypyrrole on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO₃-polypyrrole composite is proposed. The BaTiO₃-polypyrrole composite can find applications in suppression of electromagnetic interference and reduction of radar signature.     

Absorption and Structural Property of Ethanol/Water Mixture with Carbon Nanotubes

Molecular dynamics (MD) simulations are performed to study the structure and adsorption of ethanol/water mixture within carbon nanotubes (CNTs). Inside the (6,6) and (10,10) CNTs, there are always almost full of ethanol molecules and hardly water molecules. Inside wider CNTs, there are some water molecules, while the ethanol mass fractions inside the CNTs are still much higher than the corresponding bulk values. A series of structural analysis for the molecules inside and outside the CNTs are performed, including the distributions of radial, axial, angular density, orientation, and the number of hydrogen bonds. The angular density distribution of the molecules in the first solvation shell outside the CNTs indicates that the methyl groups of ethanol molecules have the strongest interaction with the carbon wall, and are pinned to the centers of the hexagons of the CNTs. Based on the understanding of the microscopic mechanism of these phenomena, we propose that the CNTs prefer to contain ethanol rather than methanol.     

BaPbO3的电子结构与光子吸收性能

采用固体无机化学反应制备了BaPbO₃微粉,确定了BaPbO₃微粉的结构和低温、低Pb/Ba摩尔比合成BaPbO₃的工艺。研究了该微粉对75kV的X射线的吸收性能,结果表明:含BaPbO₃材料60%(wt)、厚0.64mm的吸收材料,其对X射线的吸收率为86.82%,铅当量为1.3845;而含等量的未反应的PbO和BaCO₃的0.68mm的吸收材料,吸收率仅为44.43%,铅当量为0.3748。结合光子与核外电子相互作用的过程,提出了吸收原子的核外电子云的“交盖”及核外价电子在多个价轨道方向上的伸展是BaPbO₃材料具有优秀的吸收性能的主要原因的推断。进一步,以推广休克尔半经验分子轨道法半定量研究了BaPbO₃材料的铅-氧八面体的电子结构,证明了铅离子与相连的氧离子电子云发生交盖,且核外价电子在多个价轨道方向上均有伸展,初步分析了BaPbO₃材料的电子结构与光子吸收性能之间的关系。     

高温下硅酸锂吸收CO2的研究

以SiO₂和Li₂CO₃为反应原料，采用高温固相法于不同温度下合成了一系列可在高温500~750 ℃之间直接吸收CO₂的硅酸锂(Li₄SiO₄)材料。采用扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)分别观察和评价了合成材料的表面形貌与结构特征，用热重分析仪(TG)研究了硅酸锂材料吸收CO₂的性能。实验结果表明，在750 ℃下煅烧6 h即可合成出吸收CO₂性能良好的硅酸锂材料，在CO₂气氛下，于700 ℃保持约15 min即可达到吸收平衡，其吸收量约达43%(wt)左右。与文献报道相比，材料的合成条件有所改善，材料吸收CO₂的容量也有较大提高。     

Phase Behavior of Tweens/Toluene/Water Microemulsion Systems for the Solubilization Absorption of Toluene

The purpose of the present study was to formulate microemulsion systems comprised of polyoxyethelene sorbitan ester surfactants (Tweens) + cosurfactant + water + oil (toluene) and to investigate their potential use as absorbents for the removal of toluene from air. Toluene is an example of a volatile organic compound (VOC). The microemulsions formed are stabilized by the nonionic surfactants (Tweens) and toluene. The results indicate that Tween-60 is superior to other Tween surfactants, and the optimum value for the hydrophile-lipophile balance (HLB) is 15. The performances of the cosurfactants followed the order n-butylamine>alcohol>butyric acid. The experimental results showed that the HLB value is more meaningful than the Bansal, Shah, O’Connell (BSO) equation for representing microemulsion systems. Comparative tests of this new absorbent system were performed in a double-stirred reactor, and the experimental absorption results were consistent with the phase diagram. Nonionic surfactant microemulsions have a significant absorption enhancement for toluene, as indicated by as much as 80.81% of toluene being present in the phase composition diagram, which thus have great prospects in air pollution remediation.     

Absorption spectra of hexachlorobenzene adsorbed on SiO2 powders

Summary Photoacoustic spectra of hexachlorobenzene adsorbed on SiO₂ powders of different particle sizes were investigated. A comparison of the measured PA spectra with the calculated optical absorption lengths led to the conclusion that only absorption bands for which is much larger than the particle size, i.e. in the case of carrier transparency, appear in the PA spectrum. This indicates that the particle diameter determines the thickness of the sample. Compared to their solution spectra the PA spectra of HCB on the silica carriers do not show a red shift of the various absorption bands as was claimed in the literature. Permanent address: Institute of Public Health, B. Kidria, 52a, YU-51000 Rijeka, Yugoslavia     

The Low-Temperature UV/VIS Absorption Spectrum of [14]Annulene

The UV/VIS absorption spectrum of [14]annulene was measured in 3-methylpentane at room and liquid-N₂ temperatures and interpreted by the CNDO/S-CI method. This comparison between experiment and theory supports a structure with π-bond delocalization for this molecule.