天然橡胶掺杂导电机制的理论研究

绝大多数导电聚合物均具有共轭骨架,因而化学家们认为共轭作用是聚合物导电的先决条件,然而Thakur用I_2处理具有非共轭骨架的聚合物——聚异戊二烯(PI),其电导率提高十几个数量级,达到了10~(-2)～10~(-1)S·cm~(-1),引起了人们的极大关注。相关实验亦报道了基本类似的结果,但对PI的导电机制尚无统一的认识。本文利用EHMO/CO法,通过计算系列模型的二维能带结构,提出了掺杂模型以探讨天然橡胶的导电机制。     

Effects of Various Dopants on Solitons in Polyacetylene

The effects of various dopants on solitons in polyacetylene were studied by using CNDO/2 level semiempirical quantum chemical method. The width of solitons is reduced when dopant is present, and the charge density wave(CDW) is further gathered on the carbon atom in soliton center. The effects of p-type of dopants are greater than those of n-type of ones. The charge transfer in doped polyacetylene can be achieved by the propagation of CDW along the chain. The conductivity of doped polyacetylene is proportional to the quantity of charge transfer between dopant and polyacetylene chain.     

Temperature-modulated nanostructures of ytterbium-doped Cobalt Selenide (Yb-CoSe) for photovoltaic applications

This research investigated the influence of temperature variation on the properties of ytterbium-doped cobalt Selenide (Yb-CoSe) nanostructures synthesized via the electrodeposition technique. The structural, optical, morphological, and elemental features of the synthesized films were investigated through X-ray diffractometry (XRD), ultraviolet–visible (UV–vis) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) respectively. XRD results showed prominent peaks with a cubic phase. Good absorbance values in the visible region and reduced band gap energies upon the introduction of ytterbium were obtained from the optical analysis. Morphological results gave nanoclusters of varying sizes spread throughout the substrate surface. The elemental constituents of the deposited films were evident from the EDX spectra. The synthesized films have significant potential to be used in solar cells and optical devices.     

Combination of corona discharge ion mobility spectrometry with a novel reagent gas and two immiscible organic solvent liquid-liquid-liquid microextraction for analysis of clomipramine in biological samples

A novel and sensitive method based on combination of two immiscible organic solvents hollow fiber-based liquid-liquid-liquid microextraction and corona discharge ion mobility spectrometry (HF-LLLME-CD-IMS) was employed for the analysis of clomipramine in human urine and plasma. The effect of formic, acetic and propionic acid as the reagent gas (dopant) on the corona discharge ion mobility signal was investigated. The influence of dopant amount was also studied. Optimum mass flow rates of the dopants were 3.7, 1.1 and 1.0 μmol min(-1) for formic, acetic and propionic acid, respectively. Experimental parameters influencing the extraction efficiency of HF-LLLME, such as NaOH concentration as donor solution, ionic strength of the sample, stirring rate, and extraction time were investigated and optimized. Under the optimum conditions, analytical parameters such as linearity, precision and limit of detection were also evaluated. The linear dynamic range was from 1 to 100 μg L(-1) (r(2)=0.9980) and the limit of detection was 0.35 μg L(-1). Intra- and inter-day precisions were satisfactory with a relative standard deviation (RSD) of 5.9 and 6.7%, respectively. The proposed method was satisfactorily applied for the determination of clomipramine in human plasma and urine.     

Sb掺杂纳米TiO2光催化剂的晶体结构与光催化性能

用溶胶-凝胶法将纳米TiO2:Sb薄膜沉积在玻璃基板上．通过XRD、Raman光谱研究了Sb掺杂量对薄膜的晶体结构和晶相转变的影响．结果表明:纯TiO2薄膜中,TiO2不仅以无定型态存在,而且还以板钛矿和锐钛矿的形式存在．掺入适量的Sb后,由于Sb替代了TiO2的部分Ti形成Sb-O-Ti结构,改变了TiO2的晶格结构,改善了薄膜的结晶效率,使锐钛矿结构的TiO2:Sb含量明显提高．掺杂0．2％Sb时,薄膜的结晶效率最高．254 nm光源照射时,掺杂0．2％Sb的电极的阳极光电流密度可达42．49μA／cm2,是用同种方法制备的纯TiO2薄膜电极的近11倍;对亚甲基蓝具有最高分解性能,其一级反应速率常数为0．171 h／cm2,是未掺杂的纯TiO2薄膜的近2倍．     

Study on electroluminescence processes in dye-doped organic light-emitting diodes

Electroluminescence (EL) mechanism of dye-doped organic light-emitting diodes (OLEDs) was investigated by using three familiar fluorescent dyes, i.e., 5,12-Dihydro-5,12-dimethylquino [2,3-b]acridine-7,14-dione (DMQA), 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), and 5,6,11,12-tetraphenylnaphthacene (Rubrene). EL spectra of the doped devices with structure of indium tin oxide (ITO)/N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′- diamine (NPB) (40 nm)/tris-(8-hydroxyquinolate)-aluminum (Alq₃) (x nm, x=0–40 nm)/dye: Alq₃ (weight ratio≈1%, 2 nm)/Alq₃ (48−x nm)/MgAg indicated that direct carrier trapping (DCT) process dominated light emission of devices. As a result, investigation of carrier-recombination site via doping, which is conventionally applied in OLEDs, is questionable since the doping site and the dopant itself may significantly influence the carrier-recombination process in the doped devices.     

High-precision quantitative atomic-site-analysis of functional dopants in crystalline materials by electron-channelling-enhanced microanalysis

Knowledge of the location and concentration of impurity atoms doped into a synthesized material is of great interest to investigate the effect of doping. This would usually be investigated using X-ray or neutron diffraction methods in combination with Rietveld analysis. However, this technique requires a large-scale facility such as a synchrotron radiation source and nuclear reactor, and can sometimes fail to produce the desired results, depending on the constituent elements and the crystallographic conditions that are being analysed. Thus, it would be preferable to use an element-selective spectroscopy technique that is applicable to any combination of elements. We have established a quantitative method to deduce the occupation sites and their occupancies, as well as the site-dependent chemical states of the doped elements, using a combination of transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and electron energy-loss spectroscopy (EELS). The method is based on electron channelling phenomena where the symmetries of the Bloch waves excited in a crystal are dependent on the diffraction condition or incident beam direction with respect to the crystal axes. By rocking the incident electron beam with a fixed pivot point on the sample surface, a set of EDX/EELS spectra are obtained as a function of the beam direction. This is followed by a statistical treatment to extract the atom-site-dependent spectra, thereby quantitatively enabling the estimation of the site occupancies and chemical states of the dopants. This is an extension of the ‘ALCHEMI’ (Atom Location by Channelling Enhanced Microanalysis) method or ‘HARECXS/HARECES’ (High Angular Resolution Channelled X-ray/Electron Spectroscopy), and we further extended the method to be applicable to cases where the crystal of interest contains multiple inequivalent atomic sites for a particular element, applying the precise spectral predictions based on electron elastic/inelastic dynamical scattering theory. After introduction of conceptual aspects of the method, we describe the extension of the method together with the development of the theoretical calculation method. We then demonstrate several useful applications of the method, including luminescent, ferrite, and battery materials. We discuss the advantages and drawbacks of the present method, compared with those of the recently developed atomic column-by-column analysis using aberration-corrected scanning TEM and high-efficiency X-ray detectors.     

集成电路中多晶硅薄膜载流子迁移率的实验研究和理论模型

本文系统地研究了多晶硅薄膜载流子迁移率与掺杂浓度的关系,发现不仅如前人所指出的那样,多晶硅载流子迁移率在中等掺杂区有一极小值,而且同时在高掺杂区存在一个极大值.本文将前人提出的杂质分凝模型、晶粒间界陷阱模型和杂质散射机构结合起来,从理论上计算了极大值及其相应的掺杂浓度与晶粒大小、晶粒间界界面态密度的关系,并与实验结果进行了比较.理论模型较好地说明了实验结果.     

On-line capillary electrophoresis-mass spectrometry using dopant-assisted atmospheric pressure photoionization: setup and system performance

The on-line coupling of capillary electrophoresis (CE) and mass spectrometry (MS) via atmospheric pressure photoionization (APPI) is demonstrated. To achieve CE-APPI-MS, an adapted coaxial sheath-flow interface was combined with an ion-trap mass spectrometer equipped with an APPI source originally designed for liquid chromatography-MS. Effective photoionization of test compounds was accomplished after optimization of several interface and MS parameters, and of the composition and flow rate of the sheath liquid. Further enhancement of the ionization efficiency could be achieved by adding a dopant, such as acetone or toluene, to the sheath liquid to aid indirect ionization. Acetone significantly increased the ionization of the polar test compounds by proton transfer, while toluene was more useful for the enhanced formation of molecular ions from nonpolar compounds. The effect of several common CE background electrolytes (BGEs) on the APPI-MS response of the analytes was also studied. It appeared that in contrast with electrospray ionization, nonvolatile BGEs do not cause suppression of analyte signals using APPI. Therefore, in CE-APPI-MS, a variety of buffers can be chosen, which obviously is a great advantage during method development. Remarkably, also sodium dodecyl sulfate (SDS) did not affect the photoionization of the test compounds, indicating a strong potential of APPI for the on-line coupling of micellar electrokinetic chromatography (MEKC) and MS.     

The influence of precursor temperature on strontium sulphide doped silver for optoelectronic application

This research aims at the study of strontium sulphide doped silver using 0.1 mol of strontium chloride hexahydrate (SrCl2.6H2O), Thioacetamide (C₂H₅NS), and 0.01 mol of silver nitrate (AgNO3) as the cationic, anionic, and dopant concentrations via electrochemical deposition technique. The film had a strong peak at (111) and (211) which corresponds to 2theta values of 26.69° and 51.77° for undoped SrS and doped SrS respectively, and a flawless crystalline peak with a cubic phase that is indexed at orientations (111), (112), (200), and (211). SrS/Ag of deposited different precursor temperatures (room, 35, 40, and 45)^o correspond to 2theta values of 26.69°, 33.79°, 37.60°, and 51.77° respectively. The crystal lattice is shown by the rise in peak intensity with higher 2theta degree values; the appearance of an unindexed peak is caused by the substrate utilized for the deposition. Clove-like material with precipitate is visible in the SrS material's micrograph; the big nano grain on the surface of the substrate exhibits photon absorption but lacks any signs of pinholes. At the introduction of dopant and heating the precursor at 35 °C, 40 °C, and 45 °C there is a drastic change in the micrograph of the films, for the films at 35 °C the nanoparticle clave together with a melted wax with a sharp large white precipitate which is very visible on the surface of the film and the material deposited at 40 °C and 45 °C there is no visible precipitate on the film which show that as the precursor temperature increases it eliminate lattice strain and improve the photovoltaic properties of the deposited material. The energy band gap of strontium sulphide (SrS) and strontium sulphide doped silver (SrS/Ag) at different precursor temperatures of 35 °C, 40 °C, 45 °C is 1.50–2.35 eV.