Push-Pull Fluorophores Based on Imidazole-4,5-dicarbonitrile: A Comparison of Spectral Properties in Solution and Polymer Matrices

Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties. The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and methanol. The fluorescence lifetimes are in the range of 1–4 ns for all measured fluorophores. The large Stokes shift (4,000 to 8,000 cm⁻¹) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by the diffusion-controlled bimolecular rate (cca 2 × 10¹⁰ L mol⁻¹ s⁻¹). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism.     

Spectral Properties of Amphiflavins in Polymer Matrices

The parameters characterizing the absorption, fluorescence and phosphorescence of 10-dodecylisoalloxazine (DIA), 10-octadecylisoalloxazine (OIA) 3-methyl-10-dodecylisoalloxazine (MDIA) embedded into polymeric matrices (polystyrene – PS, polymethacrylate methyl – PMM and poly(vinyl alcohol) – PVA) were studied. It was found that both the polarity of microenvironment and its structure influenced the changes of the spectral properties of the examined amphiflavins.     

Spectral Properties of Probes Containing Benzothioxanthene Chromophore Linked with Hindered Amine in Solution and in Polymer Matrices

Absorption and emission spectroscopy as well as laser flash photolysis was employed in order to characterize the spectral properties of novel probes based on benzothioxantheneimide chromophore covalently linked with different types of sterically hindered amines. These were chosen as 2-(2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXINH), the equivalent stable nitroxyl radical, i.e. 2-(1-oxo-2,2,6,6-tetramethyl-4-piperidyl)thioxantheno[2,1,9dej]isoquinoline 1,3-dione (BTXINO) and the alkoxy derivative 2-(1-(1′-phenylethoxy)-2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXINOR). Spectral properties, in solutions and in various polymer matrices such as polystyrene, polymethyl methacrylate, polyvinyl chloride and polypropylene, were compared with the compound 2-(1-dodecyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXID) taken in the present study as a reference compound. By means of the fluorescence decay and in the contrary to three other probes, BTXINO probe clearly showed a biexponential decay while the three other probes led to monoexponential decay. Two different singlet excited states with lifetimes of about 0.4 and 5 ns were proposed. They correspond to two dispositions of the nitroxyl radical chain above and along the fluorescent moiety of the molecule. Such behaviour depends on the surrounding media. Moreover, an efficient intramolecular quenching of the fluorescence emission was only observed with the short lived singlet excited state. The ratio BTXID/BTXINO was found equal to about 4 and 9 in solutions and polymer matrices respectively. Laser flash photolysis indicated that the novel probes as well as the model compound yielded transient absorption with maximum at 530 nm, corresponding to the triplet states. The intermolecular quenching of such species by molecular oxygen and by free N-oxyl, such as 1-oxy-2,2,6,6-teramethylpiperidine (TEMPO) and 1-oxy-2,2,6,6-teramethyl-4-hydroxypiperidine (TEMPOL), and the intramolecular quenching was not efficient.     

铕铽共掺稀土聚合物的光谱分析及发光性能研究

合成了一种新型的稀土配合物Eu_0.5Tb_0.5(TTA)₃Phen,并采用原位乳液聚合法进一步制备了Eu_0.5Tb_0.5(TTA)₃Phen/PMMA稀土聚合物。利用红外光谱仪(IR)、电子探针X射线能谱仪等对其结构进行了表征,利用扫描隧道电子显微镜(SEM)、荧光光谱仪(FS)等研究了其微观形貌,并探讨了其发光性能。结果表明,聚合物中PMMA与稀土部分Eu_0.5Tb_0.5(TTA)₃Phen通过键合的方式结合, 仍保持Eu0.5Tb_0.5(TTA)₃Phen原有的发光特性;在365 nm紫外光的激发下,产生发光峰在611.8 nm附近、谱线带宽为10.4 nm的红光发射,发光亮度高,色纯度高;Eu_0.5Tb_0.5(TTA)₃Phen/PMMA具有良好的发光性能,其发光强度与MMA加入的含量有关。     

偶氮染料掺杂高分子薄膜的荧光光谱特性

利用旋涂法制备了新的偶氮染料掺杂薄膜，在室温下测试了该薄膜的吸收光谱，稳态荧光光谱和时间分辨荧光光谱，研究了荧光衰减动力学过程，得到了反式和顺式异构体的激光发单线态（S1）的荧光寿命。     

脱氢枞酸基D-A型分子的合成、空间构型及光谱性能

对三苯胺进行溴代和C-N偶联反应合成4-萘基三苯胺(a),对脱氢枞酸进行酯化、溴代、硝化、还原和C-N偶联反应合成13-[N,N-(4-萘基苯基)-苯基]胺基-脱异丙基脱氢枞酸甲酯(b)及13-[N,N-双(4-萘基苯基)]胺基-脱异丙基脱氢枞酸甲酯(c)两个化合物,通过1H MNR,13C MNR及MS对化合物的结构进行表征。为了研究化合物结构与光谱性能之间的关系,首先利用Gaussian 09程序采用密度泛函DFT/B3LYP方法,对三个化合物的空间构型进行全优化,得到它们的键长、键角和二面角,对比发现脱氢枞酸骨架和萘环的引入会影响化合物的共平面性,而萘环的引入会增大化合物的共轭程度。光谱性能方面,研究了三种化合物在甲醇、二氧六环、四氢呋喃、二氯甲烷和环己烷这5种极性逐渐减小的溶剂中的荧光发射光谱和紫外吸收光谱。结果表明,在荧光光谱中,化合物a,b和c在不同极性溶剂中最大荧光发射波长均有不同程度位移,在甲醇中最大,在环己烷中最小,但是位移并非随着极性的增大而只发生红移,在二氯甲烷、四氢呋喃和二氧六环3种极性依次增大的溶剂中,a,b,c的荧光发射波长均随着溶剂极性的增大而发生较大程度的蓝移;在同一溶剂中,化合物b和c相对于a的荧光发射波长依次发生红移,c的红移程度与b差距不大。紫外吸收光谱中,三个化合物在不同极性溶剂中的最大吸收波长也有差异,在200～250 nm区间,三个化合物均在二氯甲烷中有较大位移,在300～350 nm区间,在甲醇中位移较大,而在250～300 nm区间,最大吸收波长差别不大;在同一溶剂中,它们在300～350 nm区间的最大吸收波长差别较大,化合物c较a红移26 nm。结合结构优化所得数据可以证明,化合物的共轭程度对荧光发射光谱和紫外吸收光谱均有影响,而共平面性对荧光发射光谱影响较大。化合物a,b和c在不同极性溶剂中荧光发射光谱和紫外吸收光谱的较大变化,表明它们有明显的溶致变色行为,具有作为分子探针探测外部环境极性大小的潜能。     

On New Relations Between Spectral Properties of Jacobi Matrices and Their Coefficients

We study the spectral properties of Jacobi matrices. By using ``higher order' trace formulae we obtain a result relating the properties of the elements of Jacobi matrices and the corresponding spectral measures. Complicated expressions for traces of some operators can be magically simplified allowing us to apply induction arguments. Our theorems are generalizations of a recent result of R. Killip and B. Simon [17].     

Spectral and Aggregation Properties of Phenylthio-Substituted Al-Phthalocyanine Molecules in Nanoporous Silicate Matrices

Journal of Applied Spectroscopy - The absorption, fluorescence, and fluorescence excitation spectra of phenylthio-substituted Al-phthalocyanine in solutions, polyvinyl butyral films, and silicate...     

偶氮染料掺杂高分子薄膜的光谱和光存储性质研究

利用旋涂法,制备了以二乙基胺基〖Ｎ（ＣＨ２ＣＨ３）２〗作为推电子基因、以具有强电负性的羧基（ＣＯＯＨ）作为拉电子基团的推－拉型偶氮染料掺杂的高分子（ＰＭＭＡ）薄膜。在室温下测试了该偶氮染料在溶液和薄膜态的吸收光谱、薄膜态的反射光谱和透过光,发现该薄膜在４００～５５０ｎｍ波长范围内具有强的吸收。在５１４．５ｎｍ光盘静脉测试仪上测试了膜片的静脉光存储性能,结果表明,用低功率Ａｒ＾＋激光（５１４．５ｎ     

人血液荧光的光谱特性及其物质来源

取健康人的静脉血,首次实验测量了人血液的三维荧光光谱,并通过分析荧光激发-发射矩阵研究了血液自体荧光的物质来源。 结果表明：人血液的荧光激发-发射对主要有260-630, 280-340, 340-460, 450-520 nm,它们所对应的内源性荧光物质分别来源于血液中的内源性卟啉,色氨酸,还原烟碱腺嘌呤二核苷酸(磷酸盐)和黄素腺嘌呤二核苷酸。 这些物质的荧光激发效率随着激发光波长的变化而表现出显著差异。     

富勒烯C60掺杂的共轭高聚物混合薄膜的光谱性质

测量了不同富勒烯C60掺杂浓度的聚对亚苯基亚乙烯衍生物（MEH-PPV）混合薄膜的紫外-可见吸收光谱、稳态荧光和时间分辨荧光光谱。观察到MEH-PPV吸收峰受到明显的抑制以及荧光峰的猝灭。证明混合薄膜内，由于л-л共轭体系的强相互作用在基态发生MEH-PPV向C60的电子转移、形成电荷转移络合物。在光激发下会发生MEH-PPV向C60的激发传递进一步抑制了发光跃迁过程，导致了MEH-PPV荧光的强猝灭效应。     

双掺杂聚合物电致发光中能量传递的光谱分析

将两种荧光染料掺杂到有机聚合物中,制作了双掺杂的电致发光器件ITO/PVK:TPB:Rubrene/LiF/Al, 得到了聚合物与两种荧光染料之间的阶梯式的能量传递。当PVK作为能量给体,Rubrene为能量受体时,能量传递不是很有效。但通过研究共掺杂体系的发光性质,发现辅助染料TPB的加入,作为能量传递的桥梁,提高了能量传递的效率,从而增加了器件的色纯度。     

钇与偶氮氯膦MK多配位络合物溶液光谱性质的研究

在ＰＨ３．２９溶液中,钇（Ⅲ）与偶氮氯膦ＭＫ（ＣＰＡＭＫ）发生灵敏配位反应,本文应用β－修正分析理论研究此研究合物溶液性质的测定,包括配位比,逐级摩尔吸收系数、络合物稳定常数等。     

Random Incidence Matrices: Moments of the Spectral Density

We study numerically and analytically the spectrum of incidence matrices of random labeled graphs on N vertices: any pair of vertices is connected by an edge with probability p. We give two algorithms to compute the moments of the eigenvalue distribution as explicit polynomials in N and p. For large N and fixed p the spectrum contains a large eigenvalue at Np and a semicircle of small eigenvalues. For large N and fixed average connectivity pN (dilute or sparse random matrices limit) we show that the spectrum always contains a discrete component. An anomaly in the spectrum near eigenvalue 0 for connectivity close to e is observed. We develop recursion relations to compute the moments as explicit polynomials in pN. Their growth is slow enough so that they determine the spectrum. The extension of our methods to the Laplacian matrix is given in Appendix.     

Bodipy Based Fluorescent Materials in Cellulose Matrices: Synthesis,Spectral Properties and Vapochromic Fluorescent Recognition of Alcohols and Acetone

This paper highlights advances made using the 4-bora-3a,4a-diaza-s-indacene (BODIPY) as a fluorophore in design and application of fluorescent sensors for microenvironment polarity. Sections of the paper cover broad analysis of a range of fluorescent indicators immobilized in ethyl- and methyl cellulose matrices. The present study demonstrates that BODIPY-based fluorescent materials could be successfully utilized for ratiometric detection of ethanol and acetone in gas phase. The achieved limit of detection value equals 0.02 mg/ml for acetone and 0.08 mg/ml for ethanol, whereas obtained sensoric materials are reusable without regeneration required.

     

Spectral Properties of the k-Body Embedded Gaussian Ensembles of Random Matrices for Bosons

We consider m spinless Bosons distributed over l degenerate single-particle states and interacting through a k-body random interaction with Gaussian probability distribution (the Bosonic embedded k-body ensembles). We address the cases of orthogonal and unitary symmetry in the limit of infinite matrix dimension, attained either as l→∞ or as m→∞. We derive an eigenvalue expansion for the second moment of the many-body matrix elements of these ensembles. Using properties of this expansion, the supersymmetry technique, and the binary correlation method, we show that in the limit l→∞ the ensembles have nearly the same spectral properties as the corresponding Fermionic embedded ensembles. Novel features specific for Bosons arise in the dense limit defined as m→∞ with both k and l fixed. Here we show that the ensemble is not ergodic and that the spectral fluctuations are not of Wigner-Dyson type. We present numerical results for the dense limit using both ensemble unfolding and spectral unfolding. These differ strongly, demonstrating the lack of ergodicity of the ensemble. Spectral unfolding shows a strong tendency toward picket-fence-type spectra. Certain eigenfunctions of individual realizations of the ensemble display Fock-space localization.     

Solid-state Fluorescence Emission and Second-Order Nonlinear Optical Properties of Coumarin-based Fluorophores

Some coumarin-based fluorophores were synthesized and characterized by elemental analysis, ¹H NMR, ¹³C NMR and MS. The solid-state photoluminescence properties were studied. The benzocoumarins display interesting solid-state emission properties with an emission at wavelengths ranging from 532 to 645 nm, when excited by a 325 nm helium–cadmium laser at room temperature. The results demonstrated that the luminescent colors can be tuned from green to red by simply varying molecular structure. The benzocoumarin-phenyl boronic acid hybrid, 4-(3-oxo-3-(2 -oxo-2H-1-naphtho[2,1-b]pyran-3-yl)-prop-1-enyl)phenyl boronic acid, showed obvious fluorescence response to water. Whereas the free compound was very weakly fluorescent in tetrahydrofuran (THF), the addition of water leads to an appearance of strong blue-green fluorescence and a dramatic increase of emission intensity. Besides, 3-(3-(3,4,5-trimethoxyphenyl)-prop-2-enoyl)-2H-1-benzopyran-2-one exhibited second order nonlinear optical response to laser pulses. A noticeable second harmonic generation (SHG) under pulsed excitation at 1064 nm was observed. Preliminary nonlinear measurements on powder samples showed that the second harmonic generation efficiency is roughly 5.8 times that of potassium dihydrogen phosphate (KDP).     

Influence of the Bulk and Donor-Acceptor Properties of Solvent on Ligand Field Spectra

The influence of solvents on the electronic absorption spectra of chromium (III) complexes was investigated. The dependence of the crystal field parameter Dq on dielectric constant as well as Gutmann donor number DN of solvent was found and described. By using the proposed model, unknown in the literature donor numbers for a few alcohols were estimated.     

Spectral Measure of Heavy Tailed Band and Covariance Random Matrices

We study the asymptotic behavior of the appropriately scaled and possibly perturbed spectral measure of large random real symmetric matrices with heavy tailed entries. Specifically, consider the N × N symmetric matrix whose (i, j) entry is , where (x _ij , 1 ≤ i ≤ j < ∞) is an infinite array of i.i.d real variables with common distribution in the domain of attraction of an α-stable law, , and σ is a deterministic function. For random diagonal D _N independent of and with appropriate rescaling a _N , we prove that converges in mean towards a limiting probability measure which we characterize. As a special case, we derive and analyze the almost sure limiting spectral density for empirical covariance matrices with heavy tailed entries. Supported in part by a Discovery grant from the Natural Sciences and Engineering Research Council of Canada and a University of Saskatchewan start-up grant. Research partially supported by NSF grant #DMS-0806211.