Fluorescence study of inter- and intramolecular interactions in poly(p-N,N-dimenthylaminostyrene-co-9-vinylantracene)

A new exciplex-forming polymer, poly(p-N, N-dimethylaminostyrene-co-9-vinylanthracene) (PDMA-AN, DP ≈ 25) was prepared by copolymerization of p-N, N-dimethylaminostyrene and 9-vinylanthracene. Exciplex formation was observed both in the fluid media and a polymer film. The fluorescence spectrum of PDMA-AN is characterized by the appearance of a high-energy exciplex formed by the neighboring pendant 9-anthryl (AN) and p-N, N-dimethylanilino (DMA) groups, which is shifted by approximately 85 nm to shorter wavelengths in comparison with the emission band of the intermolecular exciplex formed by the monomer model anthracene-p-N, N-dimethylaminotoluene (DMAT). The polymer conformation appropriate for the formation of this state exists prior to the initial excitation and is partially eclipsed. The effects of concentration and polarity of the solvent on the flourescence emission are discussed. A red shift of the maximum wavelength of the flourescence band as a function of concentration was found in a nonpolar solvent (toluene). However, in a relatively polar solvent (1,2-dichloroethane), a shoulder peak at a longer wavelength gains in intensity with increasing concentration. These phenomena are attributed to the increase of the contribution of the normal intermolecular exciplex state in which the interacting AN-DMA groups achieve an eclipsed and sandwiched conformation.     

Dynamics of Exciplex Formations and Dissociation in Organic Molecule Vapors

The discovery and investigation of exciplex luminescence in the polyatomic molecule vapors^1-4 is of great importance for better understanding of the relaxation mechanisms in bimolecular complexes formed due to the charge transfer between photo-excited organic molecules and other type of molecules in the ground state. The study of the vapor-phase exciplex emission from 9, 10-dicyanoanthracene in the presence of N, N-dimethylaniline (9, 10-DCA + DMA) showed⁴ that the exciplex stabilities, their luminescence properties and the relative efficiency of monomer and exciplex luminescence essentially depend on the excess of the vibrational energy of excited 9, 10-DCA molecules.     

Magnetic Field-Effect on Photoluminescence of Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) Nanoparticles in a Poly[vinyl butyral] Matrix

Abstract

In this work the magnetic field effects (MFE) on the photoluminescence of MEH-PPV film and nanoparticles were obtained using the MFE technique with continuous-wave photoexcitation. The analysis of the MFE dependence for the MEH-PPV film gave a HWHM (half-width at half maximum) ～ 65?mT and a total MFE value about 102.8% at 200?mT whereas the MFE dependence of the MEH-PPV nanoparticles showed significant broadening, with their HWHM ～ 280?mT and a total MFE value of 99% at 550?mT. By a simple theoretical model based on rate equations, the mechanism of the negative magnetic field effect was explained. The observed negative effect was the result of the dominant singlet exciton formation rate in the MEH-PPV nanoparticles. For explaining this negative effect the enhanced triplet-triplet annihilation due to confinement of triplet excitons in the nanoparticles and singlet molecular oxygen-triplet exciton annihilation were proposed.     

Exciplex emission in the blend of two blue luminescent materials

Organic light-emitting diodes (OLEDs) based on the blend of two blue luminescent materials N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-diphenyl-4,4′-diamine (NPB) and 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) were fabricated. The electroluminescence (EL) spectra of this device showed a new emission that is different from their intrinsic exciton emission. Compared with the photoluminescence (PL) spectra of single layer NPB and PBD, respectively, there was an apparent red shift in that of their blend. Thus the exciplex formation in the blend can be concluded due to the similar emission in both PL and EL spectra. The exciplex formation process and the effect of applied voltage were analyzed by Gaussian fitting.     

Exciplex emission and photoinduced energy transfer as a function of cavity dimension in naphthalene-linked aza-crown ethers

We report here the photophysical properties of two derivatives of N-(β-methylnaphthalene) aza-crown systems having different cavity dimensions. The aza-crown moiety is attached to β-position of naphthalene moiety by one >CH₂ unit in both the derivatives. The cavity size is found to have a pronounced effect on exciplex formation as well as energy transfer in the systems at room temperature and low temperature, respectively. Both the systems exhibit photoinduced electron transfer (PET) which is evident from their weaker fluorescence emission and their quenched singlet lifetimes as compared to that of free naphthalene. The systems also show a solvent sensitive red shifted broad structureless emission which is assigned to exciplex formation. The ratio of quantum yields of exciplex to monomer emission (?_Exp/?_M) is lower in the smaller aza-crown (L1) as compared to that in the larger aza-crown (L2) implying a different geometry of the two systems in the excited state. Semi-emperical calculations performed on the systems also corroborate the different geometry of the two systems. Complexation of alkali metals, rare earth ions and protons by the aza-crown moiety results in enhancement of fluorescence emission due to blocking of PET. In the presence of protons, L1 exhibits a new emission due to excimer formation which has not been observed in L2 under similar conditions. The rare earth ion complexes of L1 and L2 at low temperature exhibit energy transfer from the lowest triplet state of naphthalene to the rare earth ion states, the extent of energy transfer being greater in the larger aza-crown (L2) as compared to that in smaller aza-crown system (L1).     

用荧光探针签别CYP2C9*3基因

用一种基激复合物荧光探针系统来签别碱基错配的CYP2C9*3基因,该系统选择两个分开的与靶点碱基相对应的12碱基荧光标记的寡核苷酸作为探针,分别对24碱基、47碱基、质粒(3165bp)的靶点CYP2C9基因和CYP2C9*3基因进行杂交配对,结果该基激复合物荧光探针系统能有效签别各种长度的CYP2C9基因和CYP2C9*3基因,背景干扰很低,灵敏度高,可尝试用于其他基因型的遗传多态性的签别。     

Efficiency of quenching of the B 2Σ 1 2/+ state of mercury monoiodide and monobromide by mercury dihalides in gas-discharge plasma in multicomponent mixtures of an exciplex radiation source

The efficiency of quenching of the B ²Σ ₁ ^2/+ state of HgBr* and HgI* exciplex molecules by vapors of mercury dihalides (HgBr₂ and HgI₂) in the gas-discharge plasma of a HgBr/HgI radiation source is determined. The measurement technique used is substantiated. The quenching rate constants of mercury monobromide and monoiodide exciplex molecules by mercury dihalides are 3.4 × 10^?10 and 1.1 × 10^?10 cm³/s, respectively.     

A Low-Field Magnetically Affected Reaction Yield (MARY) Spectrometer with Spectral Fluorescence Resolution

A novel spectrometer for low-field studies in magnetically affected reaction yield (MARY) spectroscopy with fluorescence detection is described. The spectrometer is based on a yoke-free magnetic system containing no ferromagnetic elements, uses X-ray or optical excitation, and includes a monochromator to analyze the spectral composition of luminescence. Using the new setup, the effect of transversal residual magnetic field on zero field MARY line is illustrated, formation of exciplexes under X-irradiation in a naphthalene/N,N-dimethylaniline solution in alkane is demonstrated, a magnetic field effect on the emission spectrum is shown in field-cycling mode, and modulated MARY spectra in the exciplex and the intrinsic luminophor bands are compared to show that magnetic field sensitivity here is provided at the stage of the recombining radical ion pair, while exciplex formation only transforms the luminescence properties.     

Spectral characteristics of a broadband exciplex spontaneous emission source upon mixtures of the cadmium dibromide vapor with gases

The spectral characteristics of radiation from atmospheric-pressure gas-discharge plasma in mixtures of cadmium dibromide vapor with gases (Ne, Ar, Kr, Xe, and N₂), as well as the temporal characteristics of the voltage and current, have been investigated. A barrier discharge at the repetition frequency of sine voltage pulses up to 140 kHz has been used to create the gas-discharge plasma and excite the components of the working mixture. The discharge radiation has been analyzed in the spectral range 200–900 nm with a high resolution (0.05 nm). In the spectra, we have revealed radiation from exciplex molecules CdBr(B → X) and CdBr(C → X), atomic lines of cadmium and inert gases, and, in mixtures with xenon, radiation of exciplex molecules XeBr(B → X, B → A). The XeBr(B → X) radiation prevailed in the spectra at mixture temperatures up to 200°C. The further increase of the temperature resulted in the prevalence of the CdBr(B → X) radiation. The most intense CdBr(B → X) radiation was observed in mixtures of CdBr₂/Xe. When the temperature of the mixture was higher than 250°C, the discharge radiation had a silvery-white color. Regularities in the spectral characteristics of the radiation from the gas-discharge plasma are discussed. The high-frequency atmospheric-pressure barrier discharge in mixtures of cadmium dibromide with gases, excited by sine voltage pulses, can be used in multiwave and broadband excilamps, operating in the UV and visible regions.     

Spectroscopic diagnostics of barrier-discharge plasma in mixtures of cadmium diiodide vapor with gases

The spectral characteristics of the emission of atmospheric-pressure gas-discharge plasma in mixtures of cadmium diiodide vapor with gases (Ne, Ar, Kr, Xe, and N₂) were investigated along with the time characteristics of the voltage and current. The gas-discharge plasma was produced and excited by a barrier discharge at a repetition rate of sine voltage pulses of up to 140 kHz. The discharge emission was analyzed in the spectral range 200–900 nm with a high resolution (0.05 nm). Radiation from exciplex CdI(B-X) molecules and excimer I₂* molecules was revealed, as well as the atomic lines of cadmium, iodine, and inert gases. In a mixture with xenon, radiation from exciplex molecules XeI(B-X, B-A) was also found. This radiation prevailed in the spectra at mixture temperatures up to 150°C. The further increase of the temperature leads to the prevalence of the CdI(B-X) radiation. It was found that the most intense CdI(B-X) radiation is observed in mixtures CdI₂/Xe(N₂)/Ne. Regularities in the spectral characteristics of the emission of the gas-discharge plasma are discussed.     

Spectroscopic characterization of the fluorobenzene/DEMA tracer system for laser-induced exciplex fluorescence for the quantitative study of evaporating fuel sprays

Quantitative analysis of laser-induced exciplex fluorescence (LIEF) requires knowledge of the spectral characteristics of all the involved substances. The temperature dependence of the ratio of exciplex and monomer in the liquid phase as well as the temperature-dependent fluorescence intensity from monomers in the gas phase must be known when quantifying signals and correcting for cross talk between liquid and vapor phase. In this work we present an extensive characterization of the fluorescence of the fluorobenzene/diethyl-methyl-amine (DEMA)/n-hexane exciplex system. We use a mixture of 2% fluorobenzene, 9% DEMA, and 89% n-hexane, which was tested before for its coevaporative behavior. The temperature dependent fluorescence of the liquid exciplex was studied in a thin layer cell with UV-light (266 nm) excitation. Cross talk of a known combination of bandpass filters was quantified for the relevant temperature range. The temperature dependence of the gas-phase absorption and fluorescence signal (fluorobenzene) was studied in a heated static cell and a heated gas stream in a nitrogen coflow, respectively. These measurements provide the background for the application of LIEF for quantitative analysis of vapor and liquid distributions in fuel sprays.     

An Improved Composite Multiscale Fuzzy Entropy for Feature Extraction of MI-EEG

Motor Imagery Electroencephalography (MI-EEG) has shown good prospects in neurorehabilitation, and the entropy-based nonlinear dynamic methods have been successfully applied to feature extraction of MI-EEG. Especially based on Multiscale Fuzzy Entropy (MFE), the fuzzy entropies of the τ coarse-grained sequences in τ scale are calculated and averaged to develop the Composite MFE (CMFE) with more feature information. However, the coarse-grained process fails to match the nonstationary characteristic of MI-EEG by a mean filtering algorithm. In this paper, CMFE is improved by assigning the different weight factors to the different sample points in the coarse-grained process, i.e., using the weighted mean filters instead of the original mean filters, which is conductive to signal filtering and feature extraction, and the resulting personalized Weighted CMFE (WCMFE) is more suitable to represent the nonstationary MI-EEG for different subjects. All the WCMFEs of multi-channel MI-EEG are fused in serial to construct the feature vector, which is evaluated by a back-propagation neural network. Based on a public dataset, extensive experiments are conducted, yielding a relatively higher classification accuracy by WCMFE, and the statistical significance is examined by two-sample t-test. The results suggest that WCMFE is superior to the other entropy-based and traditional feature extraction methods.     

TADF激基复合物主体材料提升溶液法制备蓝色荧光有机发光二极管的效率

为了提升溶液法制备的蓝色荧光有机发光二极管(OLEDs)的效率,采用了基于热激活延迟发光(TADF)的激基复合物作为主体材料。TADF激基复合物主体可以利用反向系间窜跃上转换形成单线态激子并将能量传递到客体,从而可以同时利用发光层中的三线态激子和单线态激子,以提升蓝色荧光器件的效率。选择蓝色荧光材料1-4-Di-[4-(N,N-diphenyl)amino]styryl-benzene(DSA-ph)作为客体发光材料,4,4′,4″-T-ris(carbazol-9-yl)triphenylamine(TCTA)掺杂1,3,5-Tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)(TPBi)作为热激活延迟荧光激基复合物主体,通过溶液法制备了蓝色荧光OLEDs。通过测试TCTA,TPBi以及TCTA掺杂TPBi的光致发光光谱发现,与TCTA和TPBi相比,TCTA掺杂TPBi的光致发光谱(PL)发生了明显的红移(峰值波长变为437 nm),而且光谱变宽,证明了TCTA∶TPBi激基复合物的形成。通过对于DSA-ph掺杂激基复合物主体的薄膜与DSA-ph掺杂poly(methyl methacrylate)(PMMA)的薄膜进行PL测试发现,两者发光峰相同,都是来自DSA-ph的发光,说明激基复合物主体将能量传递到了DSA-ph;DSA-ph的吸收光谱与激基复合物主体的PL光谱存在很大重叠,说明激基复合物主体与DSA-ph的能量传递非常有效;通过对激基复合物主体掺杂不同浓度客体的薄膜进行瞬态PL衰减测试发现,与纯DSA-ph的寿命相比,DSA-ph掺杂激基复合物主体之后其寿命会延长,纯DSA-ph的寿命只有1.19 ns,DSA-ph掺杂激基复合物主体的荧光衰减曲线与激基复合物主体的荧光衰减曲线相似,这进一步证明了激基复合物主体将能量传递到了DSA-ph。研究了主体引入以及DSA-ph掺杂浓度对器件性能的影响。对于器件的亮度、电流密度、电压、电流效率、电致发光光谱等参数进行了测试,与不采用激基复合物主体的器件相比,采用激基复合物主体的器件性能明显改善,在DSA-ph掺杂浓度为10%时,器件亮度从2133.6 cd·m^-2提升到了3597.6 cd·m^-2,器件效率从1.44 cd·A-1提升到了3.15 cd·A-1,发光峰只有来自DSA-ph的发光。采用TADF激基复合物主体的方法有潜力实现溶液法制备的高效蓝色荧光OLEDs。     

Electroluminescent properties of dimeric bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex

A blue shifted photoluminescent emission in bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex, ZBZT, arises out of the dimeric structure, typical of the localized electron density around the non-bridged ligand in the excited state of the complex. An average decay lifetime of 4.8 and 3.0 ns for the ligand and the complex, respectively indicates an energy transfer from the ligand to the metal. A PL quantum efficiency of about ?_ZBZT=0.45 in DMF solution is observed, in comparison to the Alq₃, complex, ?_Alq3=0.116. Semi empirical ZINDO/S-SCF-CI calculations support the dominance of non-bridged ligand moiety in controlling the photoluminescent properties. An unusually broad white light (FWHM ∼220 nm) electroluminescent emission in the two layer device structure brings out the features of an exciplex formation between the active layer ZBZT/TPD interface, which is studied at different current densities. Such a broadened emission is verified for different thicknesses of the active layer substantiating the role of exciplex formation.     

二甲氧基蒽－蒽醌体系分子内激发态复合物形成的结构条件与溶剂效应

本文报道了电子给体二甲氧基蒽（ＤＭＡ）和电子受体蒽醌（ＡＱ）以双酚Ａ（ＢＡ）和对苯二酚（ＯＰ）连接起来的双发色团分子的合成和光谱性质研究，并根据光谱数据和荧光光谱，讨论了激发态复合物形成的结构因素和溶剂效应．     

Xe-KCl excilamp

A source of UV radiation based on the B → X transition in the XeCl exciplex molecule entering into a Xe-KCl vapor-gas mixture is created. The emission properties of the excilamp (power, spectral composition, and time characteristics) are studied. Optimal conditions for excitation of the excilamp by a high-voltage pulsed-periodic discharge are found. The mean output and the efficiency of the excilamp are one order of magnitude higher than those of a Xe-NaCl lamp. The parameters of both radiation sources are analyzed in terms of the pumping efficiency.     

Spectroscopic diagnostics of barrier discharge plasmas in mixtures of zinc diiodide with inert gases

The spectral characteristics of the emission of gas discharge atmospheric pressure plasmas in mixtures of zinc diiodide vapor with inert gases (He, Ne, Ar, Kr, and Xe) are investigated. The formation of a gas discharge plasma and the excitation of the components of a working mixture were performed in a high-frequency (with a repetition frequency of sinusoidal voltage pulses of 100 kHz) barrier discharge. The gas discharge emission was analyzed in the spectral range 200–900 nm with a resolution of 0.05 nm. Emission bands of ZnI(B-X) exciplex molecules and I₂* excimer molecules, lines of inert gases, and emission bands of XeI* exciplex molecules (in Xe-containing mixtures) were revealed. It is ascertained that the strongest emission of ZnI* molecules is observed in ZnI₂/He(Ne) mixtures. The regularities in the spectral characteristics of the gas discharge plasma emission are considered.     

Structural effects on intramolecular exciplexes of 1-amino-3-anthryl-(9)-propanes

The photophysical behavior of six 1-(N-aryl-N-alkyl)-amino-3-anthryl-(9)-propanes was studied by steady-state and time-resolved fluorescence measurements in methylcyclohexane/ isopentane (MP). Structurally, these compounds are most suitable for the formation of intramolecular exciples as shown by the high exciplex quantum yields. The rate constants and the activation energies show that the rate of the exciplex formation depends on steric effects of the N-alkyl group and on the donor effect of the N-aryl group. From the rise curves of the exciplex emission it follows that also in nonpolar solvents exciplexes with a conformation deviating from the favored sandwich structure can be formed. The solvent effect on the fluorescence properties was investigated.     

Exciplex elimination in an organic light-emitting diode based on a fluorene derivative by inserting 4,4’-N,N’-dicarbazole-biphenyl into donor/acceptor interface

Organic light-emitting diodes (OLEDs) composed of a novel fluorene derivative of 2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)-6,7-difluoroquinoxaline (F2Py) were fabricated, and exciplex emission was observed in the device. To depress the exciplex in an OLED for pure colour light emission, 4, 4'-N,N'-dicarbazole-biphenyl (CBP) was inserted as a separator at the donor/acceptor interface. It was found that the device without the CBP layer emitted a green light peaking at 542~nm from the exciplex and a shoulder peak about 430~nm from F2Py. In contrast, the OLED with CBP layer emitted only a blue light peak at about 432~nm from F2Py. Device efficiencies were calculated by a simulative mode in an injection controlled type mechanism, and the results showed that exciplexes yield much lower quantum efficiency than excitons. The device with CBP has a higher power efficiency as no exciplex was present.     

The effect of driving voltage on the electroluminescent property of a blend of poly(9-vinylcarbazole) and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole

The impact of driving voltage on the electroluminescence (EL) from organic light emitting diode with ITO/PVK:PBD:TBAPF₆(10:10:1)/Al structure was analyzed by the method of Gaussian fitting. Indium tin oxide (ITO) was used as anode, poly(9-vinylcarbazole) (PVK) as polymeric host, 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) as electron-transporting molecule, tetrabutylammonium hexafluorophosphate (TBAPF₆) as organic salt and aluminium (Al) as cathode. A broad EL has been observed and it could be attributed to the overlap of emission from four different excited state complexes, including PVK:PBD exciplex, PVK:PBD electroplex, PBD electromer and PVK electromer. The EL spectra shifted to longer wavelength with the increase of driving voltage. The ratio of PVK electromer to PVK:PBD exciplex emission intensity first declined slightly and then increased remarkably, while the relative intensity of combination of PVK:PBD electroplex and PBD electromer emission remained unchanged when the voltage was increased.