超支化聚合物的光物理行为及其压力效应

在溶液中观察到超支化聚合物2-甲氧基-5-（2’-乙基已氧基）-对-苯乙烯/3 ，5-二乙烯基苯共聚体（MEH-PPV-HS_1）具有很强的荧光发射，并且在紫外区有两 个明显的相邻吸收带。分别激发这两个吸收带得到相同的荧光发射。在压力作用下 ，这两个吸收带表现出不同的压力效应，并且在不同的压力下分别激发这两个吸收 带时，所得到的荧光发射效率随压力的变化趋势表现出明显的不同。结果表明，这 两个相邻的吸收带分别来自于超支化聚合物分子中具有不同长短的有效共轭结构。 不同的共轭结构受光激发后到达不同的激发态。然后经过不同的松弛途径到达相同 的发光激发态而发出荧光。     

Multicomponent analysis in luminescence spectroscopy

Multicomponent analysis of absorption spectra (infrared or electronic spectra) by factor analysis is a suitable method to use. The algorithm of factor analysis is now available for luminescence spectroscopy. The first possibility, as in absorption spectroscopy, is to determine pure components emission spectra for a unique set of spectra of mixtures in overdetermined conditions. On the other hand, it is also possible to extract pure components emission and excitation spectra of the only data corresponding to the 3D fluorescent spectrum of a single mixture. The results are evaluated in respect to noise level and concentrations ratio on both simulated and real spectra.     

Facile Synthesis Method for the Preparation of Large‐scale Ultra‐small GdPO4:Tb and GdPO4:Tb@LaPO4 Nanowires

A simple and efficient method is presented for the large‐scale synthesis of ultra‐small, wired‐shaped GdPO₄:Tb nanostructured phosphor material with an average diameter of 2–5 nm and typical average length of 100 nm. X‐ray diffraction (X RD), transmission electron microscopy (TEM), energy dispersive X‐ray (EDX) analysis, as well as FTIR, UV–vis, emission, and excitation spectral techniques were employed to examine the crystal phase, purity, morphology, surface chemistry, and optical and photoluminescence properties of the as‐prepared nanoproducts. The TEM image clearly revealed the single‐phase, highly crystalline, narrow‐size‐distributed, ultra‐small, wire‐shaped nanostructures, which was confirmed from the XRD pattern. Optical absorption spectra in the ultraviolet region show high absorbance because of the high solubility and colloidal stability in aqueous solvents. Surface coating of an undoped LaPO₄ shell remarkably enhanced the crystallinity and photoluminescence properties of the nanowires (NWs). Core/shell NWs represent high emission and excitation intensity regardless of the core NWs because of a decrease in multiphoton relaxation pathways. It could be a highly suitable nanomaterial for optical bioprobes, biodetectors, and so on.     

Multicomponent analysis in luminescence spectroscopy

Multicomponent analysis of absorption spectra (infrared or electronic spectra) by factor analysis is a suitable method to use. The algorithm of factor analysis is now available for luminescence spectroscopy. The first possibility, as in absorption spectroscopy, is to determine pure components emission spectra for a unique set of spectra of mixtures in overdetermined conditions. On the other hand, it is also possible to extract pure components emission and excitation spectra of the only data corresponding to the 3D fluorescent spectrum of a single mixture. The results are evaluated in respect to noise level and concentrations ratio on both simulated and real spectra.     

荧光法测定N-(α-烷苯氧基)十四酰基牛磺酸钠的临界胶束浓度

研究了一类以苯氧基作疏水支链的新型阴离子表面活性剂——N-(α-烷苯氧基)十四酰基牛磺酸钠(SAPTT)水溶液的紫外吸收光谱、探针(芘)稳态荧光发射光谱及自身稳态荧光发射光谱性质.研究结果表明,荧光探针(芘)法和自身稳态荧光法可用来测定这类表面活性剂的临界胶束浓度(CMC),且测定结果与表面张力法(吊片法)接近;与荧光探针(芘)法相比,对于所研究体系,自身稳态荧光法的灵敏度和准确性均较高,所测得CMC结果与表面张力法(吊片法)能较好地吻合.     

Dual fluorescence of the isoquinolinium cation in methanol: time-resolved emission spectra and semiempirical calculations

The fluorescence behavior of the N-ethyl isoquinolinium (iso-NEQ) cation in viscous methanol is reported and discussed on the basis of time-resolved fluorescence spectra, polarization measurements and semiempirical calculations. Dual fluorescence results from two nearby excited states (S₁ and S₂) above 300 nm only at low temperature. The detection of an isoemissive point verifies this two-state model of the emission. We use the numerical self-consistent reaction field (SCRF) to include solute–solvent interactions for the calculations of the absorption transitions of iso-NEQ in methanol. We also involved the so-called supermolecular approach with three methanol molecules to reproduce the absorption transitions. The latter results are in good agreement with our experimental data.     

Density functional theory calculation of 2p spectra of SiH4, PH3, H2S,HCl, and Ar

The method developed recently for prediction of 1s electron spectra is now extended to the 2p spectra of SiH₄, PH₃, H₂S, HCl, and Ar. The method for X‐ray absorption spectra involves the use of ΔE for the excitation and ionization energies, and application of time‐dependent density functional theory using the exchange‐correlation potential known as statistical average of orbital potentials for the intensities. Additional assumptions and approximations are also made. The best exchange‐correlation functional E_xc for the earlier calculation of ΔE in 1s spectra of C to Ne (namely Perdew–Wang 1986 exchange, combined with Perdew–Wang 1991 correlation) is no longer used in this work on 2p spectra of Si to Ar. Instead, recently tested E_xc good for 2p core‐electron binding energies (known as OPTX) for exchange and LYP for correlation, plus scalar zeroth‐order regular approximation is adopted here for the ΔE calculations. Our calculated X‐ray absorption spectra are generally in good agreement with experiment. Although the predictions for the higher excitations suffer from basis set difficulties, our procedure should be helpful in the interpretation of absorption spectra of 2p electrons of Si to Ar. In addition, we report calculated results for other kinds of electron spectra for SiH₄, PH₃, H₂S, HCl, and Ar, including valence electron ionizations and excitations as well as X‐ray emission. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Self-consistent reaction field calculations of the solvent effect on absorption and emission n, π* transitions of diazines

A modified version of the self-consistent reaction field (SCRF) method has been accomplished in order to study the solvent effect on the electronic transition energies. The dielectric relaxation properties both of solvent and solute are directly taken into account in the Hartree—Fock equation. The method has been applied to calculate the solvent shifts, both in absorption and in emission, for n, π^* transitions of the three diazine isomers. It was found that the continuum model is able to describe experimental findings for aprotic solvents; the discrete plus continuum model is needed to account for the solvent shifts observed in water solution.     

Comparison of basis set effects and the performance of ab initio and DFT methods for probing equilibrium fluctuations

The electronic absorption and emission spectra of large molecules reflect the extent and timescale of electron-vibration coupling and therefore the extent and timescale of relaxation/reorganization in response to a perturbation. In this paper, we present a comparison of the calculated absorption and emission spectra of NADH in liver alcohol dehydrogenase (LADH), using quantum mechanical/molecular mechanical methods, in which we vary the QM component. Specifically, we have looked at the influence of basis set (STO-3G, 3-21G*, 6-31G*, CC-pVDZ, and 6-311G**), as well as the influence of applying the DFT TD-B3LYP and ab initio TD-HF and CIS methods to the calculation of absorption/emission spectra and the reorganization energy (Stokes shift). The ab initio TD-HF and CIS methods reproduce the experimentally determined Stokes shift and spectral profiles to a high level of agreement, while the TD-B3LYP method significantly underestimates the Stokes shift, by 45%. We comment on the origin of this problem and suggest that ab initio methods may be naturally more suited to predicting molecular behavior away from equilibrium geometries.     

对—苯二甲酸邻菲罗啉铕镧配合物的红外光谱及荧光光谱研究

用对-苯二甲酸铵和邻菲罗啉与氯化铕和氯化镧在乙醇-水溶液中反应,合成了对-苯二甲酸邻菲罗啉铕镧异核稀土配合物,测定了配合物的C,H,N和稀土元素的含量、红外光谱、紫外光谱及荧光光谱,确定了配合物的组成。结果表明,羧基氧和邻菲罗啉氮原子均与稀土离子配位,桥联配体对-苯二甲酸根可有效的传送能量,不发光的镧离子对铕离子的发光有明显的增强作用。     

基于时间分辨方法的LicT蛋白荧光动力学特性

使用时间分辨荧光方法,结合紫外吸收光谱和稳态荧光光谱技术,测量了LicT蛋白中色氨酸残基的荧光动力学特性,进而对LicT蛋白质激活前后的局部微环境和结构变化进行了研究。LicT蛋白质的激活态使得有关糖类利用的基因转录过程继续进行,促进机体新陈代谢。通过色氨酸残基的荧光发射和寿命的差异判断出激活型蛋白AC 141和野生型蛋白Q 22不同的结构性质和微环境差异。在此基础上,通过衰减相关光谱(DAS)和时间分辨发射光谱(TRES)阐释了两种蛋白色氨酸残基和溶剂的相互作用,说明了激活型AC 141的比野生型Q 22的结构更加紧密。此外,TRES还说明了蛋白中的色氨酸残基存在连续光谱弛豫过程。各向异性结果则对残基和整个蛋白的构象运动进行了阐述,说明了色氨酸残基在蛋白质体系内有独立的局部运动,且在激活型蛋白中该运动更加强烈。     

Exciton dynamics of GaSe nanoparticle aggregates

Time-resolved and static spectroscopic results on GaSe nanoparticle aggregates are presented to elucidate the exciton relaxation and diffusion dynamics. These results are obtained in room-temperature TOP/TOPO solutions at various concentrations. The aggregate absorption spectra are interpreted in terms of electrostatic coupling and covalent interactions between particles. The spectra at various concentrations may then be interpreted in terms of aggregate distributions calculated from a simple equilibrium model. These distributions are used to interpret concentration-dependent emission anisotropy kinetics and time-dependent emission spectral shifts. The emission spectra are reconstructed from the static emission spectra and decay kinetics obtained at a range of wavelengths. The results indicate that the aggregate z axis persistence length is about 9 particles. The results also show that the one-dimensional exciton diffusion coefficient is excitation wavelength dependent and has a value of about 2 x 10(-5) cm(2)/s following 406 nm excitation. Although exciton diffusion results in very little energy relaxation, subsequent hopping of trapped electron/hole pairs occurs by a Forster mechanism and strongly red shifts the emission spectrum.     

The nature of the rapid relaxation of excited charge-transfer complexes

Examples of contact radical-ion-pair (CRIP) formation from excited charge-transfer (CT) complexes are described. The reduced absorption and emission spectra of the CT complexes formed between hexamethylbenzene, pentamethylbenzene, and durene donors and 1,2,4,5-tetracyanobenzene (TCNB) in 1,2-dichloroethane (DCLE) exhibit a mirror image relationship, suggesting that each set of spectra describes transitions between the same two states. It was concluded that a CRIP is produced immediately upon excitation of the CT complex and that relaxation of the CRIP includes only minor geometry changes and changes in solvent polarization. In contrast to these results, the reduced absorption and emission spectra of the mesitylene (MES)/TCNB CT complex in DCLE are distinctly different and do not display a mirror image relationship. Time-resolved emission decay traces reveal the presence of an initial intermediate species that contributes approximately 10% of the total steady-state emission. The emission spectrum of this initial species mirrors the absorption spectrum of the MES/TCNB complex. In the MES/TCNB complex, excitation does not lead directly to the CRIP, and the relaxation of the excited complex must include an electronic component in addition to changes in geometry and solvation. The implications of these results on the applicability of golden-rule expressions of electron transfer are discussed.     

Tuning the Nature of the Fluorescent State: A Substituted Polycondensed Dye as a Case Study

An extensive spectroscopic analysis is presented of an elongated polycondensed dye with a donor–acceptor substitution. The charge‐transfer (CT) state, polarized along the long molecular axis, is close in energy to a local excitation (LE) of the polycondensed system, roughly polarized along the short molecular axis, which makes this system particularly suitable to investigate the subtle LE/CT interplay. An essential‐state model is presented that quantitatively reproduces absorption and fluorescence spectra, as well as fluorescence emission and excitation anisotropy spectra collected in solvents of different polarity and viscosity, which sets a sound basis for the understanding of how solvent polarity and solvent relaxation affect the nature of low‐lying excitations. The markedly different fluorescence emission and excitation anisotropy spectra measured in glassy and liquid polar solvents unambiguously demonstrate the major role played by solvent relaxation in the definition of fluorescence properties of the dye.     

Examination of the photophysical processes of chlorophyll d leading to a clarification of proposed uphill energy transfer processes in cells of Acaryochloris marinas

A comprehensive study of the photophysical properties of chlorophyll (Chl) d in 1:40 acetonitrile-methanol solution is performed over the temperature range 170-295 K. From comparison of absorption and emission spectra, time-dependent density-functional calculations and homologies with those of Chl a, we assign the key features of the absorption and fluorescence spectra. Possible photophysical energy relaxation mechanisms are summarized, and thermal equilibration processes are studied in detail by monitoring the observed emission profiles and quantum yields as a function of excitation energy. In particular, we concentrate on emission subsequent to excitation in the extreme far-red tail of the Qy absorption spectrum, with this emission partitioned into contributions from hot-band absorptions as well as uphill energy transfer processes that occur subsequent to absorption. No unusual photophysical processes are detected for Chl d; it appears that all intramolecular relaxation processes reach thermal equilibration on shorter timescales than the fluorescence lifetime even at 170 K. The results from these studies are used to reinterpret a previous study of photochemical processes observed in intact cells and their acetone extracts of the photosynthetic system of Acaryochloris marina. In the study of Mimuro et al., light absorbed by Chl d at 736 nm is found to give rise to emission by another species, believed to also be Chl d, at 703 nm; this uphill energy transfer process is easily rationalized in terms of the thermal equilibration processes that we deduced for Chl d. However, no evidence is found in the experimental results of Mimuro et al. to support claims that (nonequilibrium) uphill energy transfer is additionally observed to Chl a species that emit at 670-680 nm. This finding is relevant to broader issues concerning the nature of the special pair in photosystem II of A. marina because suggestions that it is comprised of Chl a can only be correct if nonthermal uphill energy transfer processes from Chl d are operative.     

几种方酸菁染料的NMR及光谱特性研究

研究了几种方酸菁染料的核磁、可见、荧光光谱。通过二维核磁共振谱和¹³CNMR确定了分子的结构和构型。测定了其在不同溶剂中吸收光谱和荧光发射光谱及其发射的荧光量子产率。发现它具有微弱的正向溶致变色特性,通过光谱特征分析得出整个分子处于平面结构并形成一个长的共轭体系,其激发态和基态的结构相近的结论。同时,讨论了结构对分子电荷分布及相应荧光光谱特征的影响。     

藻胆体核心复合物结构与功能的研究(Ⅱ)──4种变藻蓝蛋白复合物发色团相互作用机制

从螺旋藻藻胆体中分离出4种不同结构和光谱形式的变藻蓝蛋白复合物APⅠ、APⅡ、APⅢ和APB, 利用吸收光谱、荧光光谱比较了三聚体和单体的光谱特性, 通过对吸收光谱的光谱解曾以及各组分的归属, 研究了变藻蓝蛋白复合物内各色团间相互作用的性质和在能量传递中的功能.结果表明, 复合物内色团间的作用关系可以用Forster偶极-隅极作用机制来解释, 由于连接蛋白和同源亚基的存在影响其结构的对称性, 进而影响各色团间相互作用的形式和性质.     

Excitation and emission spectra of polyethylene terephthalate and polyethylene 2,6‐naphthalate films

With excitation by the light of the wavelengths longer than 320 nm, fluorescence spectra of polyethylene terephthalate (PET) films had somewhat different shapes from those excited below 300 nm through the intrinsic absorption of PET molecules. Also, in the measurements taken with a polarizer in front of the receiving monochoromator but none before the sample, the intensity ratio of parallel (to the draw axis of the film) and perpendicular components of the emission spectra was different if excited above 320 nm or below 300 nm. Discussion was made about the first step of pumping photon energy at the wavelengths above 320 nm. Fluorescence spectra of polyethylene 2,6‐naphthalate films showed a mirror image of their absorption spectra, consisting of one broad band having the same polarization as their absorption spectra. Their fluorescence occurred from the lowest excited level, conforming to the Kasha law. Copyright © 1999 John Wiley & Sons, Ltd.     

3-(3’-吡啶基)-6-芳基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑衍生物基态和激发态性质

用密度泛函B3LYP方法对3-(3’-吡啶基)-6-芳基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑衍生物(芳基为苯基、3-吡啶基和苯乙烯基)进行基态几何构型全优化, 计算分子的电离势IP和电子亲和势EA等相关能量, 并用Zerner间略微分重叠(ZINDO)和含时密度泛函(TDDFT)方法计算吸收光谱, 用单组态相互作用方法(CIS)优化三种化合物分子的S1激发态结构, 分析其能量与发射光谱的关系, 计算溶剂中分子的吸收和发射光谱, 并与实验结果对照. 计算结果表明, 从3-(3’-吡啶基)-6-苯基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑分子(化合物A)到3-(3’-吡啶基)-6-(3’-吡啶基)-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑分子(化合物B)以及3-(3’-吡啶基)-6-对乙烯苯基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑分子(化合物C)的电子亲和势依次增大, 愈来愈容易接受电子, 吸收光谱和发射光谱红移.