若丹明6G和若丹明B混合染料荧光谱特性及染料激光行为

实验发现若丹明6G和若丹明B混合溶液的荧光谱峰值波长随两种物质的混合比例不同而有规律地变化,与单一的若丹明6G和若丹明B相比,混合溶液的荧光谱线宽度明显增宽。使用混合染料,用改变混合比的方法对染料激光进行调谐,可简化调谐方法,调谐范围为557.4-588.5nm。     

溶剂对若丹明6G荧光寿命的影响(英文)

采用时间相关单光子计数技术测量了若丹明6G在不同溶剂中的荧光寿命.实验结果表明:在若丹明6G浓度为10~(-4)克分子/立升条件下,它的荧光寿命和溶质分子生成氢键的能力呈线性函数关系.据此,并参照溶剂对若丹明6G吸收光谱影响的实验结果,可以认为,溶剂对若丹明6G荧光寿命的影响主要是通过在溶质和溶剂分子间生成氢键,从而影响了若丹明6G分子发生缔合的容易程度所致.     

胶束中的若丹明6G荧光增强和激光行为

使用阴离子表面活性剂十二烷基硫酸钠 (SDS)有效的增强了若丹明 6G染料水溶液的荧光 ,在若丹明 6G浓度分别为 5 47× 10 -7和 5 47× 10 -4 mol·L-1时 ,最大增强比率分别为 1 95和 9 7。在后一浓度下SDS的加入使若丹明 6G染料激光阈值降低 ,能量转化效率提高。不加SDS时的激光阈值功率密度约为 6 5MW·cm-2 ,加入 4 1× 10 -2 mol·L-1的SDS后 ,激光阈值功率密度降为 0 8MW·cm-2 。泵浦光功率密度为 6 5MW·cm-2 时 ,能量转化效率达到 2 5 %。同时还观察到SDS的加入使溶液吸收谱、荧光谱和染料激光发生了红移。对以上现象的物理机制进行了讨论。     

吸附于银岛膜上的染料的表面荧光

利用“四能级”模型,对吸附于金属岛膜上的染料分子的表现荧光增强因子随分子表面覆盖度和分子的荧光量子效率的变化进行了理论分析,同时测量了吸附于银岛膜上的荧光素钠分子和若丹明6G分子的表观荧光增强因子随分子荧光量于效率的变化。 关键词：     

若丹明6G共振增强苯(C6H6)的受激拉曼散射实验研究

报道了若丹明6G乙醇溶液中苯的受激拉曼散射Stokes波共振放大的实验研究.在特定的染料溶液浓度下,1阶、2阶Stokes波得到有效放大,放大倍数分别为3.81和6.1.对荧光共振放大SRS的物理机制进行了分析讨论.     

纳米银粒子表面吸附染料分子的荧光增强及荧光猝灭现象

本文通过阴、阳离子型染料分子荧光素钠(FS)及若丹明6G(Rh6G)吸附在银胶体系内纳米银颗粒表面上,首次发现了FS的荧光增强谱及Rh6G的荧光猝灭谱.引起荧光增强及荧光猝灭的因素,除局域场和分子到金属表面能量转移这两个方面外,还与纳米银表面与被吸附分子之间的距离有关.     

铜蒸气激光泵浦的高效脉冲若丹明6G染料激光器(英文)

本文给出了铜蒸气激光泵浦的脉冲染料激光器性能的理论预测.根据这个理论,设计了一台用铜蒸气激光泵浦的、具有纵向泵浦结构和喷流的高功率高效率若丹明6G染料激光器.对若丹明6G染料,得到了0.86W的平均输出功率,效率为31%.     

染料分子荧光淬灭规律研究

本文研究了若丹明B、若丹明6G和吖啶橙三种染料分子吸附于银表面上时的荧光变化规律,发现在银胶颗粒表面的吸附均造成了其荧光强度急剧而大幅度的淬灭,淬灭随时间呈双曲线型衰减。同时利用这一实验结果对分子在表面间的吸附系数与脱附系数——这些表征分子与表面相互作用的重要参数——表达式进行了初步推导。     

十二烷基硫酸钠(SDS)增强若丹明6G水溶液激光激发荧光谱研究

报道了若丹明6G水溶液添加不同浓度的表面活性剂十二烷基硫酸钠(SDS)时激光激发染料的变化,发现较低的掺入量导致R6G荧光减弱,适量SDS的加入使荧光增强,在5×10-5 mol·L-1的R6G水溶液中,加入6×10-2 mol·L-1 SDS,荧光增强因子达到3.1。当R6G浓度为1×10-4 mol·L-1时,加入2×10-2 mol·L-1,染料激光阈值显著降低。测量了不同浓度的R6G溶液的吸收光谱及加入不同浓度SDS后的荧光谱,分析了不同SDS加入量下R6G荧光减弱及增强的物理机制。     

染料分子荧光淬灭规律研究

本文研究了若丹明B、若丹明6G和吖啶橙三种染料分子吸附于银表面上时的荧光变化规律,发现在银胶颗粒表面的吸附均造成了其荧光强度急剧而大幅度的淬灭,淬灭随时间呈双曲线型衰减。同时利用这一实验结果对分子在表面间的吸附系数与脱附系数——这些表征分子与表面相互作用的重要参数——表达式进行了初步推导。     

Optimization in Solvent Selection for Chlorin e6 in Photodynamic Therapy

The photophysical properties of chlorin e6 (Ce6) in twelve different protic, aprotic and non-polar solvents were investigated using ultraviolet–visible and fluorescence spectroscopic methods. Solvatochromic effects were determined by the changes in quantum yield, Stokes shift, fluorescence half-life and excited state dipole moments of Ce6 in the different solvents. The absorption shifts observed in different solvents were further analyzed using the Kamlet-Abboud-Taft model and the nature of solute-solvent interactions between Ce6 and different protic and aprotic solvents was elucidated. The quantum yields were found highest in protic solvents (except water), followed by aprotic and non-polar solvents. Solvent polarity parameters showed a linear increasing trend with Stokes shift and fluorescence half-life, which indicated the presence of Ce6-solvent interaction. Using the Kamlet-Abboud-Taft model, a direct correlation between the solvent polarity parameters and absorption shift was observed, which substantiated the existence of Ce6-solvent interaction by hydrogen bond formation. The excited state dipole moments in specific protic and aprotic solvents were found to be higher than the ground state dipole moments, implying a more polar nature of Ce6 during excited state transition.     

溶剂对香豆素343染料光谱性质和最低激发态偶极矩的影响

通过对香豆素343(C343)在不同溶剂中的稳态吸收光谱、稳态荧光光谱和时间分辨荧光光谱的分析,研究了溶剂对C343的光谱性质的影响,并获得了光谱特性与溶剂极性之间的依赖关系. 吸收光谱峰值的红移随着溶剂极性的增加而发生较小的变化. 然而,荧光光谱的峰值对溶剂的极性却很敏感,并随着溶剂极性参数f(ε,n)的增加呈线性增长. 这是由于C343激发态电荷分布的变化导致了它在极性溶剂中第一激发单重态能级的变化. 用溶剂效应测量法和量子化学计算方法确定了C343最低激发态的偶极矩,这两方法所得的结果一致. C343在不同溶剂中的时间分辨荧光光谱研究表明荧光寿命随着溶剂极性的增加而增加,即从甲苯溶液的3.09 ns线性地增加到水溶液中4.45 ns;荧光寿命延长的根源可归因于C343与氢键给体溶剂之间的分子间氢键相互作用.     

Solvent effects on the gain of rhodamine 6G

The effect of solvents on the gain and the peaks of gain spectra is investigated for rhodamine 6G (R6G) under nitrogen laser pumping. The non-specific solute-solvent interaction for R6G is found to be mainly dispersive. Additional shifts produced for R6G in certain solvents are explained as due to hydrogen bonding. The gain characteristics are interpreted on the basis of the position and overlap of absorption and fluorescence spectra, the quantum yield, the absorption at the pumping wavelength and the refractive index of the solvent. For the solvents studied it is found that R6G has high gain in solvents with low refractive index and high polarity. Amongst the solvents studied the alcohols displayed the highest gain with methanol being the most suitable solvent. The lowest gain amongst the alcohols was with capryllic alcohol which gave a gain that was 69% of that obtained with methanol. Amongst all the solvents studied the lowest gain was with chloroform, being only 34% of the gain in methanol.     

Absorption, fluorescence studies and ab initio calculations on binary mixture of p-dimethylaminobenzaldehyde

Absorption as well as fluorescence emission studies of p-dimethylaminobenzaldehyde (DMABA) in solvents with different polarity have been reported by varying the concentration of the solute. Dual fluorescence corresponding to the non-polar (NP) and twisted intramolecular charge transfer (TICT) states has been observed. The optimized geometry of DMABA was evaluated using ab-initio theory at various levels. The optimized geometries of the hydrogen bonded complexes with the solvent molecules were also calculated with the theory Hartree Fock at the basis set 6-31+G (HF/6-31+G). The results have been used to understand the structure of the molecule and the spectral changes in terms of hydrogen bonding and solute–solvent interaction.     

Spectral Investigations of Solvatochromism and Preferential Solvation on 1,4-Dihydroxy-2,3-Dimethyl-9,10-Anthraquinone

Solvatochromic and preferential solvation of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone (DHDMAQ) have been investigated using optical absorption and fluorescence emission techniques. Optical absorption spectra of DHDMAQ in different solvents show the intra molecular charge transfer band in the region 400–550nm. The observed blue shift with solvent polarity indicates the delocalisation of the excited state, owing to reduction in quasiaromaticity of the chelate rings formed by intra molecular hydrogen bonds, due to electrostatic or hydrogen bonding interaction. This is also confirmed by the observed low oscillator strength and the transition dipole moment. The observed quantum yield of DHDMAQ in different solvents is due to the inter molecular hydrogen bond in the excited state in addition to the intra molecular hydrogen bond. It also reveals from the low oscillator strength, which indicates that the radiative decay is low. Excited state dipole moment of DHDMAQ is calculated by solvatochromic data and it shows a lower value than ground state dipole moment. The preferential solvation parameter shows that in dimethyl formamide (DMF) + ethanol mixture, the DHDMAQ is preferentially solvated by ethanol in DMF rich region and by DMF in ethanol rich region. In the case of DMF + dichloromethane mixture DHDMAQ is preferentially solvated by DMF.     

Solvent Effects in Optical Spectra of ortho-Aminobenzoic Acid Derivatives

We investigated three amino derivatives of ortho-aminobenzoic or anthranilic acid (o-Abz): a) 2-Amino-benzamide (AbzNH₂); b) 2-Amino-N-methyl-benzamide (AbzNHCH₃) and c) 2-Amino-N-N′-dimethyl-bezamide (AbzNH(CH₃)₂), see Scheme 1. We describe the results of ab-initio calculations on the structural characteristics of the compounds and experimental studies about solvent effects in their absorption and steady-state and time-resolved emission properties. Ab-initio calculations showed higher stability for the rotameric conformation in which the oxygen of carbonyl is near to the nitrogen of ortho-amino group. The derivatives present decrease in the delocalization of π electron, and absorption bands are blue shifted compared to the parent compound absorption, the extent of the effect increasing from to Abz-NH₂ to Abz-NHCH₃ Abz-NH(CH₃)₂. Measurements performed in several solvents have shown that the the dependence of Stokes shift of the derivatives with the orientational polarizability follows the Onsager-Lippert model for general effects of solvent. However deviation occurred in solvents with properties of Bronsted acids, or electron acceptor characteristics, so that hydrogen bonds formed with protic solvents predominates over intramolecular hydrogen bond. In most solvents the fluorescence decay of AbzNH₂ and AbzNHCH₃ was fitted to a single exponential with lifetimes around 7.0 ns and no correlation with polarity of the solvent was observed. The fluorescence decay of AbzN(CH₃)₂ showed lifetimes around 2.0 ns, consistent with low quantum yield of the compound. The spectroscopic properties of the monoamino derivative AbzNHCH₃ are representative of the properties presented by Abz labelled peptides and fatty acids previously studied.     

N-Triazinyl Derivatives of 1- and 9-aminoanthracene: Synthesis and Photo-Physical Properties

New N-triazinyl derivatives were synthesized by reaction of cyanuric chloride with 1- and 9-aminoanthracenes and subsequent nucleophilic substitution of chlorine atoms on triazinyl ring with methoxy and/or phenylamino groups. The compounds were characterized by ¹H and ¹³C NMR and mass spectra. The influence of the chemical structure and solvent polarity on the UV/Vis absorption and fluorescence spectra and fluorescence quantum yields were investigated. Semi-empirical computations revealed highly polar CT states in singlet excited state manifold connected with charge-transfer from the hydrocarbon moiety to the triazinyl ring. The relationships between the CT-to-emitting state energy gap, solvent polarity and fluorescence quantum yield were discussed.     

A new coumarin laser dye 3-(benzothiazol-2-yl)-7-hydroxycoumarin

The electronic absorption, and emission spectra as well as fluorescence quantum yield of 3-(benzothiazol-2-yl)-7-hydroxycoumarin (BTHC) were measured in different solvents and are affected by solvent polarity (Δf). The deprotonation of BTHC by triethylamine is a reversible process. BTHC is relatively photostable, the quantum yield of photodecomposition (φ_c) was found to be 2×10⁻⁴ and 2.7×10⁻⁴ in EtOH and DMF, respectively. The fluorescence lifetimes of BTHC were measured in the absence and in the presence of molecular oxygen and were found to be 2.82 and 2.78 ns, respectively. BTHC acts as good laser dye upon pumping with nitrogen laser (λ_ex=337.1 nm) in ethanol and gives laser emission with maxima at 508 and 522 nm.     

The Effect of N-methylation on Photophysical Properties of 3-Aminoquinoline

It has been reported previously that the photophysics of 3-aminoquinoline (3AQ) is governed by a flip–flop motion of its amino group in apolar solvents and intersystem crossing in polar solvents. The nonradiative rates are governed by more than one solvent parameters, like polarity and hydrogen bonding ability of the solvent. So, 3AQ is not a well-behaved probe of any individual solvent parameter. In the present work, 3AQ has been modified synthetically; replacing an amino hydrogen atom with a methyl group and photophysical properties were studied in 22 different apolar, polar-aprotic and polar-protic solvents. It is found that Stokes’ shifts and fluorescence quantum yields exceptionally low in apolar solvents as compared to those in other solvents. Such substitution causes a decrease in the extent of the effect of the hydrogen bonding ability of the solvent and that nonradiative rate become a more regular function of polarity. However, the flip–flop appears to continue to be the major nonradiative pathway, as the nonradiative rates decrease with increase in micropolarity.     

General and Specific Solvent Effects in Optical Spectra of <Emphasis Type="Italic">ortho</Emphasis>-Aminobenzoic Acid

We describe studies about solvent effects on the absorption and emission properties of o-aminobenzoic acid (o-Abz), interpreting the results within the framework of general and specific solute-solvent interactions. Measurements were performed in several solvents and analysis of the absorption and emission wavelengths were made based on Lipperts model for general solvent effects and on the use of different parameters to describe the ability of the solvent to promote specific interactions with the solute. We observed low sensitivity of the Stokes shift upon changes in the medium polarity, and large deviation from the linearity predicted by Lipperts equation when the solvents were characterized as Bronsted acid in the Kamlet-Taft ^* scale. Quantum yield and fluorescence lifetimes were best interpreted based on the AN+DN scale used to describe the electron donor/acceptor properties of the solvent. The results indicated that non-radiative deexcitation processes are favoured in solvents which promote the formation of intramolecular hydrogen bond, while interactions with electron acceptor solvents lead to enhancement of fluorescence.