甲基橙-银胶体系pH和氯离子效应的光谱研究

研究了甲基橙-银胶体系的光吸收和光致发光信号随pH值和加入氯离子的变化规律.实验发现随着pH值的增加, 分子的荧光发射峰与银胶的光吸收峰的重叠增大, 引起体系中能量转移效率的增加, 即428 nm分子荧光峰的淬灭和560 nm聚集体的特征光致发光峰增强现象的加剧.另外, 不同pH值下氯离子的加入都会使染料分子更加密集的吸附在胶体银颗粒表面, 形成分子吸附更加紧密的聚集体, 造成体系中受表面吸附分子影响的光致发光峰获得了极大的增强.同时, 因聚集体表面吸附层染料分子对入射光的大量吸收, 导致到达内核银表面的入射光强度减弱, 致使体系能量转移通道在一定程度上受阻, 表现为428 nm荧光峰的淬灭幅度减小.参照分子聚集体的形成理论, 接合体系光谱的变化, 从pH值的改变和Cl^-的加入对分子结构及加剧聚集体的形成等方面的影响来解释发光和光吸收的显著变化.     

3种核酸碱基(胞嘧啶、胸腺嘧啶、尿嘧啶)在银电极表面的吸附形态

通过表面增强拉曼散射研究了胞嘧啶、胸腺嘧啶和尿嘧啶在粗糙银电极表面上的吸附形态随电极电位的变化关系.大量的结构信息可从丰富的表面拉曼信号及其随电极电位相应的变化而获得.分析表明在电极电位负移过程中,胞嘧啶一直通过N3位垂直吸附于纳米银颗粒表面;而胸腺嘧啶分子和尿嘧啶分子在表面的吸附状态都随电位改变发生了变化,较正电位下...     

半胱胺单分子膜结构的表面增强拉曼散射研究(英文)

在金属电极表面所形成的有机分子的单分子膜或薄膜对于基础研究和实际应用都有着极其重要的意义。以化学吸附形式在金电极表面所形成的半胱胺单分子膜,常常用于蛋白质等生物大分子在金属表面进行吸附的连接层,以避免这些生物大分子在金属表面直接吸附而造成的变性、失活现象的发生。本文报道了我们采用表面增强拉曼散射光谱方法研究在金电极表面吸附的半胱胺单分子膜的结构特征。研究结果表明,在金电极表面所形成的半胱胺单分子膜中,半胱胺分子主要的构型为扭转构型。在与金表面的相互作用中,由于除巯基的结合作用以外,还存在半胱胺分子中端基氨基和金表面较强的亲和性,使得以扭转构型吸附在金表面的半胱胺单分子膜相当稳定。这是金电极表面的半胱胺单分子膜结构的主要行征。当考察外加电势对此单分子膜结构的影响时,可以发现有关扭转构型的特征谱峰其相对强度随着电位负移而减小。这一结构随电位的变化关系可以通过表面电势的变化对氨基氮原子上孤对电子与金属表面间相互作用的影响来加以阐释。     

荧光分子印迹膜选择性检测7-氨基-4-甲基香豆素

合成了以7-氨基-4-甲基香豆素为模板分子,聚偏氟乙烯微孔滤膜为支撑介质的分子印迹复合膜.采用荧光光度法,研究了荧光分子印迹膜的吸附动力学、吸附容量和选择性吸附性能.研究表明,该印迹膜对模板分子具有良好的识别功能.     

染料分子吸附在正、负电性纳米银上的荧光增强及荧光猝灭现象

制备了两种不同表面电性的胶态纳米银 ,选取阴离子型染料分子荧光素钠、既有阴离子基团又有阳离子的染料分子罗丹明B ,研究其在两种纳米银表面的荧光增强及荧光猝灭现象 .当罗丹明B(RhB)分子分别吸附在这两种纳米银上时 ,对负电性纳米银 ,观察到荧光猝灭、荧光峰红移现象 ,且在分子的浓度适当时 ,加入KBr可获得较强的表面增强拉曼光谱 ;在正电性纳米银上 ,当分子的浓度较大时观察到荧光猝灭 ,当分子的浓度较小时观察到荧光增强 .而当荧光素钠分子 (FS)分别吸附在这两种纳米银上时 ,在负电性纳米银 ,观察到荧光猝灭 ;在正电性纳米银上观察荧光急剧增强现象 .从分子的结构及纳米银表面局域场增强或无辐射通道的增加对增强和猝灭的原因作了讨论 .     

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。     

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。     

吡啶羧酸在银电极表面随电极电位变化的表面增强拉曼光谱研究(英文)

本文通过表面增强拉曼散射研究了三种不同构型的吡啶羧酸—皮考酸、异烟酸和烟酸在粗糙银电极表面上的吸附形态随电极电位的变化关系。大量的表面结构信息可从丰富的表面拉曼信号及其随电极电位相应的变化而获得。分析表明在电极电位负移过程中皮考酸分子一直采取通过羧基和苯环上的N原子侧立吸附在银电极表面,与之不同的是,异烟酸分子和烟酸分子在表面的吸附状态都随电位改变发生了变化,我们对此进行了分析和解释     

纳米银与表面吸附荧光素的荧光性能的影响

研究了纳米银粒子对表面吸附荧光素(fluorescein,Fl)的荧光性能的影响。Fl溶液中加入纳米银粒子,Fl分子包覆在纳米银粒子表面形成Fl_n-Ag复合物使纳米银相互桥连形成类似网络的结构,且Fl分子吸收峰随着纳米银浓度的增加发生红移。纳米银通过产生的强局域场将能量传输给Fl发光中心,实现了Fl的荧光增强,荧光增强效率随着纳米银浓度的增加具有最大值。较大粒径的纳米银使Fl获得最大荧光增强效率所需浓度较低且最大荧光增强效率值较高。研究结果表明,纳米银与Fl间的能量传输主要由Fl分子附近局域电磁场增强和分子到金属表面无辐射跃迁能量转移过程所决定并与纳米银的浓度、尺寸密切相关。     

染料分子吸附在正、负电性纳米银上的荧光增强及荧光猝死现象

制备了两种不同表面电性的胶态纳米银，选取阴离子型染料分子荧光素钠、既有阴离子基团又有阳离子的染料分子罗丹明B，研究其在两种纳米银表面的荧光增强及荧光猝死现象，当罗丹明B（RhB）分子分别吸附在这两种纳米银上时，对负电性纳米银，观察到荧光猝死、荧光峰红移现象，且在分子的浓度适当时，加入KBr可获得较强的表面增强拉曼光谱：在正电性纳米银上，当分子的浓度较大时观察到荧光猝灭，当分子的浓度较小时观察到荧光增强，而当荧光素钠分子（FS）分别吸附在这两种纳米银上时，在负电性纳米银，观察到荧光猝死；在正电性纳米银上观察荧光急剧增强现象，从分子的结构及纳米银表面局域场增强或无辐射通道的增加对增强和猝灭的原因作了讨论。     

Absorption and luminescence of Nd3+:Y3Al5O12

In this paper there are briefly summarized the results of our experimental measurements of the fluorescence spectra, originating in levels of the⁴ F _3/2 term and terminating on the first two terms of the⁴I multipet, and the results of the absorption spectra at room temperature (RT) and at liquid-nitrogen temperature (NT) from which Nd³⁺: Y₃Al₅O₁₂ energy-level diagram was determined. Further, using the splitting of the⁴F_3/2,⁴F_5/2 and⁴F_7/2 terms the crystal-field parameters were calculated.     

High-pressure optical studies of Y2O3:Eu3+ nanoparticles

Abstract

The fluorescence spectra of Y₂O₃:Eu³⁺ nanoparticles have been measured under the pressure of up to 78 kbar at room temperature. In this pressure range, a red-shift of 0.02(1) nm/kbar^?1 is noticed for the 0–2 line (⁵D₀→⁷F₂ transition). This shift is explained by the change of negative charge of the surrounding ligands. Compatibility between measured and calculated values for the 0–2 line position was obtained. The luminescence decay curves of the ⁵D₀→⁷F₂ transition were studied up to 78 kbar and were found to behave exponentially for all pressures studied. The fluorescence lifetime τ for the 0–2 line (⁵D₀→⁷F₂ transition) slowly decreased with pressure. The pressure effect on τ for the 0–2 line (⁵D₀→⁷F₂ transition) was explained by a model which considers the pressure effect on the line position, inter-ionic distance, ion volume and polarizability, molecular volume and polarizability, molecular refractive index and the refractive index medium n _med of the surrounding hydrostatic medium. The fluorescence lifetime calculated by the present model is in close correspondence with the experimental values.     

High Pressure effect on fluorescence lifetime τ for magnetic dipole 5D0→5F1 transitions in YAG:Eu3+

The fluorescence lifetime for magnetic dipole ⁵D₀→⁷F₁ transition in yttrium aluminum garnet doped with Eu³⁺ (YAG:Eu³⁺) crystal was studied under the pressure of up to 10.4?GPa at room temperature. The fluorescence lifetime τ (⁵D₀→⁷F₁ transition) slowly decreased with pressure. The pressure effect on τ (⁵D₀→⁷F₁ transition) was explained with a model which considered pressure effect on line position: inter-ionic distance, ion volume, molecular volume, ion polarizability, molecular polarizability, sample refractive index, and surrounding hydrostatic medium refractive index. The fluorescence lifetime τ calculated by the presented model was in close correspondence with the experimental values.     

LiF晶体F3+色心的实验研究

本文从实验上系统地研究了在不同条件下电子束辐照LiF晶体所形成的F₃⁺色心的光学特点。并且由荧光光谱分析了F₃⁺心和F₂心,的相对密度关系。实验表明,辐照温度对于色心的形成和密度的相对大小起着关键的作用。主要实验结果包括:1)在液氮温度下辐照,然后在暗处加热至室温可形成高密度的F₃⁺心,表现在发射光谱中F₃⁺心荧光占绝对优势。吸收光谱表明没有N心和R心。2)由动力学荧光谱可以看到低温辐照的样品在F₂⁺心衰变的同时,F₃⁺心密度迅速增加。而室温辐照的样品则是F₂心,与F₃⁺心的密度以近似相等的速率增加。3)详细观察了F₃⁺心530nm荧光激发带与F₂心670nm荧光激发带半宽度的变化和双峰结构。由此对M吸收区的发光特点作了解释。 关键词：     

Luminescence properties of pyron red—A new molecular probe for protein research

The dependence of the luminescence of the new anionic dye Pyron Red (PR) on the polarity of the medium is investigated. Upon passage from an aqueous phase to a nonpolar phase, PR shows a shortwave shift of the fluorescence emission maximum from 675 to 650 nm and an increase in the fluorescence quantum yield from 0.03 to 0.54–0.70. When complexed with human serum albumin, PR shows fluorescence excitation and emission maxima at 525 and 625 nm and a fluorescence quantum yield of 0.8. In a comparison of the luminescence properties of PR with those of the well-known probes ANS and K35 in water and a complex with albumin, PR is shown to have the maximum absolute sensitivity but a lower fluorescence enhancement upon binding with a protein compared to ANS. A convenient criterion of the probe sensitivity toward binding with a protein that is defined as the ratio of the fluorescence intensities of the protein-bound and the free probe A_F=F_b/F_f is proposed. The value of A_F(35) for the PR probe ranks between those for the K35 probe with a low A_F(18) and ANS with a high A_F(105). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 369–374, May–June, 1999.     

Phenyl substituted Mg porphyrazines: The effect of annulation of a chalcogen-containing heterocycle on the spectral-luminescent properties

We have performed complex experimental and theoretical investigations of the spectral-luminescent properties and electronic structure of new phthalocyanine analogs, Mg octaphenylporphyrazine and its derivatives with an annulated thiadiazole or selenadiazole ring instead of two phenyl groups. Fluorescence characteristics have been determined at 293 and 77 K: emission, excitation, and fluorescence polarization spectra; fluorescence quantum yield ?? _F , and lifetime ?? _F . Annulation of a five-membered chalcogen-containing heterocycle leads to splitting of the long-wavelength absorption band Q(0-0) and to the bathochromic shift of its longest wavelength component Q _x (0-0), which increase upon passage from S to Se. At the same time, the fluorescence quantum yield ?? _F and lifetime ?? _F decrease, which is related to the intramolecular heavy-atom effect. The geometric structure of the ground state of the Mg porphyrazine molecules has been determined based on the density functional theory (DFT), and excited electronic states have been calculated with modified parametrization of the INDO/S method, INDO/Sm. Semiquantitatively, the calculated level positions of the lowest Q states and spectral shifts of Mg octaphenylporphyrazine and S-derivative agree with experimental data. For the range of the Soret band, calculated transition energies and their intensity distributions substantially depend on the dihedral angle ?? between a phenyl ring and porphyrazine macrocycle. We show that, based on calculations at the angle ?? = 60°, bands in the observed absorption spectra can be assigned with an accuracy of ??2000 cm^?1.     

Intense ultraviolet and blue upconversion emissions in Yb-Tm codoped stoichiometric Y7O6F9 powder

Stoichiometric Y₇O₆F₉ powder codoped with Yb³⁺-Tm³⁺ was synthesized via co-precipitation and subsequent calcining route. The results of X-ray diffraction and transmission electron microscopy reveal that when the calcining temperature is beyond 800 °C, orthorhombic YF₃ nanoparticles can be completely oxidized into orthorhombic Y₇O₆F₉ powder. Under the excitation of a 980 nm laser, Y₇O₆F₉ powder exhibits multicolor UC emission in regions spanning the UV to the NIR. In addition, the upconversion emission intensities of YF₃, Y₇O₆F₉ and Y₂O₃ powders were compared under the same dopant condition (Yb/Tm=5/0.5 mol%). The low phonon energy revealed by Raman spectra helped to understand the high efficient upconversion emission of Y₇O₆F₉ and the main phonon vibration of Y₇O₆F₉ lies at 472 cm⁻¹, which is far lower that of Y₂O₃ (at 708 cm⁻¹). Our results indicate that orthorhombic rare earth ions doped Y₇O₆F₉ is an efficient matrix for UV and blue UC emission, and has potential applications in color displays, anti-counterfeiting and multicolor fluorescent labels.     

Diode-pumped actively Nd:Lu0.33Y0.37Gd0.3VO4 Q-switched laser with electro-optic (EO) modulator

Nd:Lu_0.33Y_0.37Gd_0.3VO₄ crystal is a new triple-mixed vanadate crystal and has broader fluorescence line-width. By using electro-optic (EO) modulator as active Q-switch, a diode-pumped actively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser is realized for the first time. The average output power and the pulse width under different EO repetition rates are measured. The experimental results show that the actively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser can generate shorter pulse width with higher peak power. Due to broader fluorescence line-width, the triple-mixed crystal Nd:Lu_0.33Y_0.37Gd_0.3VO₄ is a promising laser medium for the Q-switched laser.     

A Molecular Thermometer Based on the Delayed Fluorescence of C70 Dispersed in a Polystyrene Film

A new optical molecular thermometer, based on the thermally activated delayed fluorescence of C₇₀ dispersed in a polystyrene film, was developed. In the presence of oxygen, the fluorescence intensity of the C₇₀ film is essentially temperature independent in a wide range. In the absence of oxygen, however, the fluorescence intensity markedly increases with temperature. At room temperature (25°C), and after degassing the sample, the fluorescence intensity of C₇₀ increases 22 times, while at 100°C the fluorescence intensity is increased by 70 times. With our system, the very weak fluorescence of C₇₀ (Φ_F ≅ 5 × 10⁻⁴, in toluene) can be increased up to 91 times (up to an estimated maximum value Φ_F = 0.046). The estimate value of the singlet-triplet gap (29 kJ mol⁻¹) and the fluorescence lifetime (0.63 ns) of the C₇₀ in film are in agreement with the values reported in the literature for C₇₀ in solution. The values of the phosphorescence lifetime at room temperature (23 ms) and the quantum yield of triplet formation (0.989) were also determined. The system is completely reversible with respect to heating-cooling cycles.     

Passively Q-switched laser performance of the mixed crystals Nd:Lu0.15 Y0.85 VO4, Nd:Lu0.5 Y0.5 VO4 and Nd:Lu0.33Y0.37Gd0.3VO4 with GaAs saturable absorber

By using the mixed crystals Nd:Lu_0.15 Y_0.85 VO₄, Nd:Lu_0.5Y_0.5VO₄ and Nd:Lu_0.33Y_0.37Gd_0.3VO₄ as laser media, the LD pumped passively Q-switched mixed lasers with GaAs saturable absorber are realized. The average output power, the pulse width etc. have been measured and compared. The experimental results show that the passively Q-switched Nd:Lu_0.33Y_0.37Gd_0.3VO₄ laser can generate shorter pulse width with higher peak power due to broader fluorescence line-width. Under Gaussian spatial distribution approximation, the rate equations for LD pumped passively Q-switched lasers of the mixed crystals with GaAs saturable absorber are given. The numerical solutions of the equations are in agreement with the experimental results.