Calibration of Circular Dichrometers in the Visible Region

Abstract

The cesium salt of R, R-(-)-trans-l, 2-cyclohexane-diaminetetraacetatocobaltate(III), Δ-(+)₅₄₆-Cs[Co(R, R(-)-CDTA)], Δ-Cs[Co(R, R(-)CDTA)]), provides a compound which can be used for calibration of circular dichrometers in the visible region. Δ-Cs[Co(R, R(-)CDTA)] has three major circular dichroism (CD) maxima at 593 nm, 527 nm, and 240 nm. The molecular ellipticities, [θ], at 593 nm, 527 nm, and 240 nm are -4490 ± 40, 5720 ± 40, and -47, 900 ± 300 deg cm² dmol^?1, respectively. The CD maxima in terms of Δε at 593, 527, and 240 nm are -1.36 ± 0.01, 1.73 ± 0.01, and -14.5 ± 0.1 l cm^?1 mol^?1, respectively. Optical rotatory dispersion (ORD) and ultraviolet-visible absorption data has also been obtained for this compound.     

Synthesis of multifunctional copolymers of poly(methylphenylsilane) with (R)-N-(1-phenylethyl)methacrylamide,disperse red 1 methacrylate and their optical and photoluminescence properties

Abstract

We report the synthesis and characterization of multifunctional polysilane copolymers containing chiral and azobenzene chromophore as a pendant group. Multifunctional polymers of poly(methylphenylsilane) (PMPS) with (R)-N-(1-phenylethyl)methacrylamide (R-NPEMAM) and disperse red 1 methacrylate (DR1MA) were synthesized in a quartz tube using UV-technique. The molecular weights of such synthesized copolymers were found to be in the order of 10³. The appearance of two glass transition temperatures in DSC indicated that the synthesized copolymers are block copolymers. The electronic absorbance of synthesized polymers was observed at 272?nm (π-π* transition of aromatic ring), 330?nm (σ-σ* transition of Si-Si chain of PMPS) and 475?nm (n-π* with π-π* transition due to azobenzene chromophore of DR1MA unit). The chirality of the synthesized polymer was confirmed through circular dichroism observed at 261?nm. Induced chirality appeared at 330?nm and 470?nm due to the association of the Si-Si chain of PMPS and the presence of azobenzene chromophore of the DR1MA unit respectively. The photoluminescence (PL) properties of the synthesized copolymers (SCDRDM-1B, SCDRDM-2B, and SCDRDM-3B) were observed at 307?nm and 415?nm when excited at 275?nm. The λem was also observed at 415?nm when excited by 325?nm. The multi-emission spectra appeared at 500?nm, 550 and 590?nm are presumed to be due to exciton coupling between azobenzene chromophore of DR1MA, and Si-Si σ-conjugation in association with the aromatic ring of PMPS and chiral unit R-NPEMAM block.     

Calibration of Circular Dichrometers

Abstract

The tris (hydroxymethyl)aminomethane salt of d-10-camphorsulfonic acid (TRIS-CSA) provides a convenient, non-hygroscopic alternative to the parent compound in the calibration of circular dichrometers. The molecular ellipticities, [6], of TRIS-CSA at 291 and 191 nm are 8015± 11 and -16, 130± 40 deg cm² dmol^?1, respectively. The circular dichroism (CD) maxima in terms of δε are 2.429 1 cm^?1 mol^?1 at 291 nm and -4.888 1 cm^?1 mol^?1at 191 nm. TRIS-CSA has an ORD peak at 306.5 nm, a zero crossover at 292 nm, and a trough at 270.5 nm (molecular rotation, [M]_306.5=4475± 10, [M]_270.5= -5615± 10 deg cm² dmol^?1), and a molar absorptivity, ε, of 35.9± 0.2 1 cm^?1 mol^?1 at 286 nm.     

SURFACE MOLECULAR STRUCTURE DETERMINATION OF LITHIUM SALT OF 10,12-NONACOSADIYNOIC ACID MONOMER AND POLYMER LANGMUIR-BLODGETT FILMS BY SCANNING FORCE MICROSCOPY COMPARED TO ELECTRON DIFFRACTION RESULTS

Langmuir-Blodgett films of lithium salts of 10,12-nonacosadiynoic acid monomer (Li/16-8 DA) and polymer (Li/16-8 PDA) were characterized by scanning force microscopy (SFM or AFM) to study their surface molecular structure. Based on analysis of these images, a two-dimensional oblique unit mesh is assigned for Li/16-8 DA monomer LB film with unit mesh parameter c = 0.549 ± 0.040 nm and b = 0.541 ± 0.060 nm with an angle of 113°. A hexagonal unit mesh is assigned for Li/16-8 PDA with unit mesh parameter c = 0.497 ± 0.052 nm and b = 0.497 ± 0.060 nm. We then report the comparison of two-dimensional, fast Fourier transform (FFT) of SFM images to the electron diffraction images. From the viewpoint of a three-dimensional structure projected onto a plane, centered rectangular nets can be assigned for both Li/16-8 DA and Li/16-8 PDA. The monomer unit cell parameters are c = 0.460 ± 0.040 nm and b = 1.020 ± 0.060 nm. The polymer cell parameters are c = 0.485 ± 0.080 nm and b = 0.820 ± 0.010 nm. The correlation between the two very different methods of surface structure determination is excellent. However, care must be taken in assigning the unit net (two-dimensional representation) and the projected unit cell (three-dimensional) vectors.     

高效发光材料[(C^N)2IrL]+阳离子配合物的结构和光谱特征

从理论上研究了一系列Ir(Ⅲ)[(C^N)2IrL]+[C^N=ppy, L=pzpy(1); C^N=dfppy, L=pzpy(2); C^N=ppy, L=pybi(3); C^N=tpy, L=acac(4); 其中ppy=2-苯基吡啶, dfppy=2-(2,4-双氟苯基)吡啶, pzpy=2-吡唑基吡啶, pybi=1-苯基-2-(吡啶基)-1H-苯并咪唑, tpy=2-(4-甲苯基)-吡啶, acac=乙酰丙酮]配合物的结构和光谱特征. 分别在B3LYP/LanL2DZ和CIS/LanL2DZ计算水平下优化了它们的基态和激发态结构. 计算得到的Ir-N, Ir-C和Ir-O基态键长和相应实验值符合较好. 在激发态下, Ir-N和Ir-C键长增加了约0.0003~0.003 nm, 而Ir-O键长则缩短了约0.0012 nm. 在含时密度泛函理论(TD-DFT)计算水平下, 结合极化连续介质模型(PCM), 得到配合物1~4的最低能的吸收和发射分别出现在398 nm(1), 370 nm(2), 419 nm(3)和437 nm(4)以及511 nm(1), 457 nm(2), 602 nm(3)和479 nm(4). 配合物1, 2, 4的跃迁属于d(Ir)+π(C^N)→π*(C^N)的电荷转移跃迁, 而化合物3的跃迁则归因于d(Ir)+π(C^N)→π*(pybi)的电荷转移跃迁. 这表明此类配合物的吸收和发射主要受前线分子轨道的金属成分控制, 同时也受辅助配体L的影响.     

Fluorimetric determination of reducing carbohydrates with malonamide

Samples are heated for 90 min with malonamide in carbonate buffer (pH 9.2) for measurement at 383 nm (excitation)/425 nm (emission). For D-glucose, relative standard deviations are 1–3% at the 10^-6–10^-9 mol level. Relative fluorescence intensities are reported for 36 carbohydrates.     

WAVELENGTH DEPENDENCE OF THE INTERSYSTEM CROSSING EFFICIENCY FOR RETINAL ISOMERS

Abstract— The quantum efficiencies of intersystem crossing (_ISC) fur four isomers of retinal, the all- trans , 9- cis , 11- cis and 13- cis , have been measured using both 265 nm and 353 nm excitation. The values for the all- trans and 9- cis isomers are independent of the excitation wavelength but the values for the 11- cis and 13- cis isomers show a marked increase in the efficiency of ISC for 353 nm excitation compared with the 265 nm excitation.     

长波敏化发光铕配合物纳米粒子的制备与表征

以牛血清白蛋白(BSA)为保护剂, 利用沉淀法制备了平均粒径为35 nm的Eu(tta)3dpbt (dpbt = 2-(N,N-二乙基苯胺-4-基)-4,6-二(3,5-二甲基吡唑-1-基)-1,3,5-三嗪, tta = 噻吩甲酰三氟丙酮负离子)荧光纳米粒子. BSA保护Eu(tta)3dpbt纳米粒子在水中分散稳定性高, 光稳定性好, 长波敏化发光性能优良. 其在可见光区激发峰位于415 nm, 激发峰尾部延展至470 nm, 发光量子产率为0.20 (λex=415 nm, 25 ℃). 在近红外双光子激发下可发出纯正的红光, Eu(tta)3dpbt纳米粒子最大双光子激发作用截面为2.4×10⁵ GM (λex=830 nm, 1 GM=10^-50 cm⁴·s·photo^-1·particle^-1).     

N,N′-二-(2-吡啶基)苝四羧酸二酰亚胺的合成及性能研究

合成了N,N′ 二 (2 吡啶基)四羧酸二酰亚胺,并纯化、调晶.对产物进行了元素分析和IR光谱研究(环状二酰亚胺的CO以双峰1708.8cm-1、1664 5cm-1).α晶型产物溶液的紫外可见光谱(最大吸收波长为526.00nm)和荧光光谱(最大发射波长为538.0nm)存在很好的镜像对称关系.薄膜紫外可见光谱图在450—570nm范围内,α晶型比β晶型有较强的吸收峰.X粉末衍射也反映出α晶型在2θ为25.5°、26.3°上的衍射峰强度分别为1954、2603.α、β晶型分别作为电荷产生材料制得的功能分离型有机光导体,在光源波长λ=532nm曝光下,测得含α的感光体达到饱和电位的时间45s、半衰曝光量5.7μJ/cm2、残余电位22V等数据.测得含β的感光体达到饱和电位的时间49s、半衰曝光量9.9μJ/cm2、残余电位22V等性能数值.     

Synthesis and photophysical properties of carbazole-based blue light-emitting dendrimers

A new class of highly fluorescent and stable carbazole-based dendrimers (1-5) that contain the ethynylbenzene and diethynylbenzene cores has been synthesized and characterized. They show very high extinction coefficients of absorption (A(max) approximately 328-353 nm) and high quantum yields of fluorescence (lambda(max) approximately 386-437 nm; Phi(F) approximately 0.72-0.89; tau(F) approximately 2.09-3.91 ns) in dichloromethane. The quantum yields of fluorescence of 1-5 in the solid state are equally high (lambda(max) approximately 385-422 nm; Phi(F) approximately 0.40-0.85). These data indicate their potential use as blue-emitting materials in organic light-emitting diodes (OLEDs).     

QUALITATIVE STUDIES OF THE LOW TEMPERATURE PHOTOCHEMISTRY OF RHODOPSIN AND RELATED PIGMENTS

Abstract— Rhodopsin, the isomeric pigments formed from 9- cis - and 9, 13- dicis -retinal, and the synthetic pigments formed from 9- cis - and 11- cis -14-methylretinal were irradiated with 490 nm light at -196C. Absorption spectral changes indicate that a distinguishable bathorhodopsin type intermediate may be formed for each pigment. The bathorhodopsin intermediates of the 9- cis pigments have band maxima hypsochromically shifted by4–5 nm compared to their corresponding rhodopsins. The bathorhodopsin type intermediate formed upon irradiation of 9, 13- dicis -rhodopsin has an absorption that maximizes 6 nm shorter than that of rhodopsin. Band maxima of the bathorhodopsin intermediates of the 14-methylrhodopsins are bathochromatically shifted ca. 8 nm compared to their corresponding rhodopsins.     

Ultraviolet photochemistry of trichlorovinylsilane and allyltrichlorosilane: vinyl radical (HCCH2) and allyl radical (H2CCHCH2) production in 193 nm photolysis

The absolute gas phase ultraviolet absorption spectra of trichlorovinylsilane and allyltrichlorosilane have been measured from 191 to 220 nm. Over this region the absorption spectra of both species are broad and relatively featureless, and their cross sections increase with decreasing wavelength. The electronic transitions of trichlorovinylsilane were calculated by ab initio quantum chemical methods and the observed absorption bands assigned to the A(1)A'<-- X[combining tilde](1)A' transition. The maximum absorption cross section in the region, at 191 nm, is sigma = (8.50 +/- 0.06) x 10(-18) cm(2) for trichlorovinylsilane and sigma = (2.10 +/- 0.02) x 10(-17) cm(2) for allyltrichlorosilane. The vinyl radical and the allyl radical are formed promptly from the 193 nm photolysis of their respective trichlorosilane precursors. By comparison of the transient visible absorption and the 1315 nm I atom absorption from 266 nm photolysis of vinyl iodide and allyl iodide, the absorption cross sections at 404 nm of vinyl radical ((2.9 +/- 0.4) x 10(-19) cm(2)) and allyl radical ((3.6 +/- 0.8) x 10(-19) cm(2)) were derived. These cross sections are in significant disagreement with literature values derived from kinetic modeling of allyl or vinyl radical self-reactions. Using these cross sections, the vinyl radical yield from trichlorovinylsilane was determined to be phi = (0.9 +/- 0.2) per 193 nm photon absorbed, and the allyl radical yield from allyltrichlorosilane phi = (0.7 +/- 0.2) per 193 nm photon absorbed.     

金纳米粒子-荧光素体系的光谱特性

纳米粒子具有量子尺寸效应和表面效应等许多特有的性质 [1] ,在光吸收、医药及新材料等方面具有广阔的应用前景 .纳米粒子具有较高的比表面能且带有电荷 ,当光子与其接近时 ,实际上是光子与纳米粒子的界面电子发生了作用 [2 ,3 ] .基于此建立的共振散射 (RS)光谱技术已成为一种高灵敏度和高选择性的分析技术 ,是研究生物化学和液相纳米粒子特性的良好手段 [4～ 9] .我们 [2 ,3 ] 研究发现 ,较大粒径纳米粒子和界面的形成是导致散射光增强的根本原因 ;金、银等液相纳米粒子产生 RS效应和 RS峰等 .荧光猝灭 (FQ)效应已用于分析化学和蛋白…     

The simultaneous spectrophotometric determination of nickel and cobalt in mixtures with 3-hydroxypicolinealdehyde azine

The properties of the nickel complex of 3-hydroxypicolinealdehyde azine are described (λ_max = 480 nm, ? = 4.2· 10⁴ l mol^-1 cm^-1). The optimal conditions for a selective and sensitive spectrophotometric determination of nickel are discussed. The absorption spectra of the nickel and cobalt (II) complexes of 3-hydroxypicolinealdehyde azine are sufficiently different to permit the simultaneous spectrophotometric determination of both ions when the absorbances are measured at 480 nm and 540 nm. Mixtures containing nickel and cobalt in ratios from 0.1 to 10 can be analysed. The method has been applied to process catalysts on alumina supports.     

MULTIPLE CHROMOPHORE SPECIES IN PHYTOCHROME*,†,‡

Abstract— Buffered aqueous solutions of pure phytochrome, when irradiated at 730 nm, had a main absorption band at about 660 nm and a shoulder or secondary band at 580–600 nm. When irradiated at 660 nm, these absorption bands bleached and a pair of bands at 670 and 725–730 nm appeared. When 660 nm irradiated samples were placed in the dark the 730 nm absorption slowly bleached and the 670 nm absorption band shifted to 660 nm. The kinetics of the bleaching indicated that two populations of P_FR existed initially. These two populations decayed by first order kinetics with k's of 4.8 × 10^-4 sec^-1 and 3.1 × 10^--⁵ sec^-1at 25°. While the bleaching of P_FR was occumng, the appearance of the 660 nm and 580–600 nm absorption bands characteristic of P_R took place. The kinetics of the increase in the 580 and 660 nm absorption bands indicated that it was arising from two populations of reactants by two first order reactions with k's of 6.4 × 10^-4 sec^-1 and 3.1 × 10^-5sec^-1 at 25°. When the sodium chloride concentration of the solvent was changed the proportions of the kinetically different populations were altered. In some conditions, especially in the presence of air. reversible but non-reciprocal changes in the four absorption bands were observed. These effects were evident after the lapse of many hours in the dark. When native phytochrome was treated with sodium dodecyl sulfate all absorption bands but the 580–600 nm absorption band were bleached and photoreversibility was lost. When native phytochrome was treated with glutaraldehyde, the 730 nm absorption band was bleached but photoreversibility was retained. It was concluded that at least four species of chromophore exist in phytochrome with absorption maxima at 580, 660 , 670 and 730 nm. Each chromophore is capable of being bleached by appropriate irradiation or in the dark by chemical reactions rather than photochemical reactions. The reactions are probably coupled redox reactions between the 580–660 nm pair and the 670–730 pair of chromophores. Discrepancies observed in the reciprocity of the absorption changes in these paired bands are probably due to various degrees of uncoupling and secondarily to the redox potential of the solvent when such uncoupling occurs.     

Identification and determination of oxytetracycline, tiamulin, lincomycin, and spectinomycin in veterinary preparations by thin-layer chromatography/densitometry

A thin-layer chromatographic/densitometric method was developed for the identification and quantitation of oxytetracycline, tiamulin, lincomycin, and spectinomycin in veterinary preparations. Silica gel-coated thin layer chromatography plates and 2 mobile phases were used to separate these constituents. The appropriate compositions of the suitable mobile phases were established: 10% citric acid solution-n-hexane-ethanol (80 + 1 + 1, v/v) and n-butanol-ethanol-chloroform-25% ammonia (4 + 5 + 2 + 5, v/v). Along with Rf values and spot colors, direct UV and visual densitometric measurements were used for identification. Similar measuring ranges were used for quantitative analysis to obtain repeatable and reliable results for the preparations examined. The results of the quantitative analysis are characterized by a small confidence interval and are close to the declared contents of active constituents: oxytetracycline 30.01 +/- 0.38 g at lambda = 350 nm and 30.24 +/- 0.86 g at lambda = 430 nm; tiamulin, 10.19 +/- 0.86 g at lambda = 450 nm; lincomycin, 2.27 +/- 0.08 g at lambda = 278 nm; and spectinomycin, 2.18 +/- 0.07 g at lambda = 421 nm. The recoveries for all antibiotics ranged from 100.01 to 102.54%.     

一种新型噻唑偶氮类金属离子显色剂的合成及性能

合成了2 (4,5 二甲基 2 噻唑偶氮) 4 甲基 5 磺酸丙基氨基苯甲酸(DMTAMSOB),研究了该试剂与Cu2+、Ni2+、Co2+离子的显色反应.实验结果显示Cu2+、Ni2+、Co2+分别在628nm、590nm、583nm处有最大吸收,其摩尔吸光系数(ε)分别为8.4×104,5.8×104,4.8×104,表明DMTAMSOB是上述离子较好的分光光度分析显色剂.     

Application of prominent spectral lines in the 125-180 nm range for inductively coupled plasma optical emission spectrometry

A new axially viewed ICP optical emission spectrometer featuring an argon-filled optic and CCD detectors was evaluated for the application of prominent spectral lines in the 125-180 nm range. This wavelength range was investigated for several analytical applications of inductively coupled plasma optical emission spectrometry (ICP-OES). There are different advantages for the application of spectral lines below 180 nm. A number of elements, such as Al, Br, Cl, Ga, Ge, I, In, N, P, Pb, Pt, S and Te, were found to have the most intense spectral lines in the wavelength range from 125-180 nm. Compared with lines above 180 nm higher signal-to-background ratios were found. Low limits of detection using pneumatic nebulization of aqueous solutions for sample introduction were calculated for Al II 167.080 nm (0.04 microg L(-1)), Br I 154.065 nm (9 microg L(-1)), Cl I 134.724 nm (19 microg L(-1)), Ga II 141.444 nm (0.8 microg L(-1)), Ge II 164.919 nm (1.3 microg L(-1)), II 142.549 nm (13 microg L(-1)), In II 158.583 nm (0.2 microg L(-1)), P I 177.500 nm (0.9 microg L(-1)), Pb II 168.215 nm (1.5 microg L(-1)), Pt II 177.709 nm (2.6 microg L(-1)), S I 180.731 nm (1.9 microg L(-1)) and Te I 170.00 nm (4.6 microg L(-1)). Numerous application examples for the use of those lines and other important spectral lines below 180 nm are given. Because of fewer emission lines from transition elements, such as Fe, Co, Cr, lines below 180 nm often offer freedom from spectral interferences. Additional lines of lower intensity for the determination of higher elemental concentrations are also available in the vacuum ultraviolet spectral range. This is specially useful when the concentrations are not in the linear range of calibration curves obtained with commonly used lines.     

离子液体中Pb^2+／Pb^4+溶质局域结构的EXAFS研究

在超稀浓度条件下ω[Pb(OAc)2]或ω[Pb(OAc)4]<0.2,我们使用EXAFS方法对 溶解在离子液体中的铅化合物的局域结构进行了研究。从结果中可以看出,Pb (OAc)4的铅中心在（0.200±0.003）nm处有8个氧近邻,而Pb(OAc）2的铅中心在（ 0.225±0.003)nm处有6个氧近邻。但是溶解在离子液体中的铅化合物均具有较低的 配位数（一般小于4）,这显示出离子液体具有较低的配位性能。另一方面,铅中 心与最近邻氧的原子间距有较大的变化。例如：溶解于[bmim]PF6的Pb^4+的Pb-O间 距为（0.186±0.005)nm,配位数仅为2.4,从Fourier变换谱上可清楚地看出有第 二配位壳层的贡献;溶解于[bmim]PF6的Pb^2+的Pb-O间距也明显地小于纯样品中 Pb-O的间距。相比之下,溶解于[ bmim]BF4的铅离子显示出的Pb-O间距与纯样品几 乎没有差别,对于Pb^2+为0.223nm,而对于Pb^4+为0.210nm。     

Synthesis of Bi2Se3 thermoelectric nanosheets and nanotubes through hydrothermal co-reduction method

Bi₂Se₃ nanosheets and nanotubes were prepared by a hydrothermal co-reduction method at 150, 180, 200, and 210 °C. Bi₂Se₃ nanosheets, nanobelts and nanotubes were obtained. The Bi₂Se₃ nanoflakes are 50-500 nm in width and 2-5 nm in thickness. The Bi₂Se₃ nanotubes are 5-10 nm in diameter, 80-120 nm in length, and 1.3 nm in wall thickness. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron diffraction were employed to characterize the products. Experimental results showed that the nanosheets and the nanotubes are hexagonal in structure with a=4.1354 Å and c=27.4615 Å. A possible formation and crystal growth mechanism of Bi₂Se₃ nanostructures is proposed.