固体活性基底表面增强拉曼光谱研究进展

表面增强拉曼光谱(SERS)是一种研究分子吸附和界面现象的有效手段,它促进了拉曼光谱技术应用的发展,其增强机理主要包括电磁增强机理和化学增强机理。固体活性基底是SERS技术的重要组成部分,综述了水体系和非水体系SERS固体活性基底的研究状况及SERS固相基底在定量分析方面的应用,指出了SERS固体活性基底在非水体系的应用潜力。     

水汽界面二维银颗粒表面上的单分子拉曼光谱检测

随着各种超灵敏分析仪器的发展 ,已经可以在低温固体中、室温液体中和电介质表面检测、鉴定单分子及其动力学行为 .这种新进展为科学家在分析化学、分子生物学和纳米结构材料等各种学科的应用开辟了许多新的视窗 .单分子谱学的研究在基础科学和应用科学方面引起了人们广泛的兴趣 .人们不仅希望能够“看到”单分子 ,而且希望了解单分子的物理化学行为 .在各种超灵敏检测技术中 ,拉曼光谱成为一种重要的技术 .由于原子力显微等微区技术的发展 ,并结合高灵敏度检测技术的进步 ,拉曼光谱已经发展成为一种检测灵敏度可以达到分子级的检测技术 [1,…     

活性艳兰X-BR在银镜表面增强拉曼光谱的研究

自1974年Fleishmann[1]等人发现表面增强拉曼散射(surface-enhanced Raman scattering,SERS)现象以来,SERS技术由于其高的表面检测灵敏度以及易于获得全波段振动光谱等优点,已为人们在分子水平上认识贵金属表面提供了丰富的信息。人们主要利用该技术研究吸附分子的各种性质。一     

基于超微电极的原位电化学拉曼光谱

原位电化学拉曼光谱是一种重要的光谱电化学技术.基于超微电极的原位电化学拉曼光谱将拉曼光谱反映的结构信息与电极表面的电化学过程从实验上严格对应和关联,为深刻理解电化学反应机理提供依据.本文综述了采用超微电极作为工作电极的原位电化学拉曼光谱的研究方法和应用进展,总结了应用超微电极作为工作电极开展电化学拉曼光谱实验的方法和具有表面增强拉曼活性的超微电极制备方法,展示了如何利用在超微电极表面获得的拉曼光谱与界面电化学过程的严格关联研究单个锌颗粒电化学氧化过程、吡啶分子在Au电极表面的电化学吸附过程,以及如何利用该技术能以高的信噪比和灵敏度同时测量光电流与分子反应这一特性研究对巯基苯胺选择性光氧化反应.采用超微电极作为工作电极的原位电化学拉曼光谱技术极大拓展了拉曼光谱技术的研究范围,有望成为探索(光)电化学反应的有力工具.     

拉曼光谱技术在聚合物研究中的应用进展

拉曼光谱可以提供分子的振动信息,对于聚合物分子链的构象和链间的相互作用非常敏感,能够提供聚合物固体、薄膜或溶液的物理化学特性信息,如聚合物的结构单元、空间构型、晶态结构、分子链的物理构象或分子链子链和侧基在界面间或在各向异性材料中的排列等链取向信息等。因此拉曼光谱作为一种原位无损检测技术,其衍生出的表面增强拉曼光谱技术(Surface-enhanced Raman Scattering,SERS)、变温拉曼光谱技术、共焦显微拉曼光谱技术(Confocal Raman Microscopy,CRM)、拉曼Mapping成像技术和共振拉曼散射技术(Resonance Raman scattering,RRS)等,广泛应用于物理、化学和生物医学等领域。本文从拉曼光谱的基本理论基础、拉曼光谱技术及其在聚合物研究中的最新应用进展等方面进行综述,以探索扩展拉曼光谱技术在高分子物理与化学领域中许多问题,如分子链的构象结构、分子链的结晶行为、分子链的扩散运动和共混体系相态结构变化等方面的应用。     

一种新型表面增强拉曼活性基底的制备方法

表面增强拉曼光谱技术 (SERS)具有极高的灵敏度 ,对某些分子其灵敏度比常规拉曼光谱高一百万倍 ,能检测吸附在金属表面的单分子层和亚单分子层的分子 ,并提供丰富的分子结构信息 [1～ 5] .活性基底的制备是获得 SERS信号的前提 ,电化学粗糙化的电极、贵金属溶胶及真空蒸镀的金属岛膜是SERS分析中最常用的 3种活性基底 ,在实际应用中各有利弊 .本文报道一种新的制备银纳米粒子基底的方法 ,可使银纳米粒子生长到合适的尺寸 ,以达到最佳SERS增强效果 .利用紫外 -可见光谱和 AFM研究该 SERS基底纳米粒子的尺寸分布和形貌 ,以 1 ,4-(双…     

催化材料的紫外拉曼光谱研究

综述了在过去的几年中,我们研究组利用紫外拉曼以及共振拉曼光谱技术在含过渡金属的微孔和介孔材料中活性位结构的表征.分子筛合成机理以及氧化物表面相结构研究中取得的进展.微孔.介孔材料骨架中超低含量的孤立的过渡金属离子或氧化物包括TS-1,Ti-MCM-41,Fe-ZSM-5,Fe-SBA-15和V-MCM-41等能够通过紫外拉曼光谱可靠、准确地鉴别出来.利用紫外拉曼可避开荧光和增加灵敏度的特点,利用自行设计的可用于原位研究水热合成过程的原位紫外拉曼光谱池,对几种典型分子筛(X型分子和Fe-ZSM-5)的合成过程实现了拉曼光谱研究.结果表明,紫外拉曼光谱可以灵敏地检测出合成前体、中间物以及分子筛晶体的演化过程.此外.通过共振拉曼光谱研究了Fe/ZSM-5上的活性中心以及活性氧物种.结果表明,这种具有高活性的氧物种是一种双原子铁物种上的过氧离子,反应的中间物种类似于单加氧酶中的铁络合物.紫外拉曼光谱对氧化锆和氧化钛等氧化物的研究中发现,氧化物的表面与体相结构不同.这一发现对于催化材料的研究有着非常重要的意义,因为大多数的催化材料性质主要取决于它的表面结构.例如,在氧化钛体系中,将用紫外拉曼光谱鉴定出的表面物相信息与氧化钛光催化活性相关联,提出了"锐钛矿-金红石表面异相结增强光催化活性"的新概念.     

细胞功能分子的表面增强拉曼成像及其应用研究进展

表面增强拉曼光谱(surface-enhanced Raman spectroscopy, SERS)具有高灵敏、高通量的特性.基于SERS的拉曼成像技术是一种无损的生物成像技术,已被广泛应用于细胞表面与细胞内生物分子的检测和成像,如对聚糖、microRNA、蛋白质等分子的定量、结构分析与功能追踪等.这一技术也已用于细菌的快速检测、细胞或细菌间的信号通讯研究、细胞p H检测,并可通过活体肿瘤组织的边缘描绘指导手术切除. SERS成像可以规避生命体系中强的分子自荧光以及荧光成像中的光漂白现象,并可以利用不同拉曼信标的指纹光谱实现高灵敏、高通量的生物成像.通过与其他成像技术(如核磁共振成像、光声成像)的结合, SERS成像有望用于更复杂生命体系中生物分子的研究.本文综述了近年来细胞功能分子的表面增强拉曼成像及其应用方面的研究进展.     

表面增强拉曼光谱在毒品检测中的应用进展

表面增强拉曼光谱(surfaced-enhanced Raman spectroscopy, SERS)作为一种借助贵金属纳米材料可以增强目标分子信号的拉曼光谱技术,由于其具有指纹识别、高灵敏、高准确度、快速无损、不受水分子干扰等特点,在法庭科学领域中的痕量毒品检测方面逐渐受到人们的关注.SERS不仅用于毒品纯品的检测...     

电化学表面增强拉曼光谱的量子化学研究

对于在分子水平上研究电化学表面吸附和反应过程,表面增强拉曼光谱(SERS)显示出了其独到的优势,提供了有力的技术方法,但对于其表面增强机理仍有待深入研究.本文总结了将量子化学计算应用于电化学表面增强拉曼光谱(EC-SERS)分析的研究,以电化学界面分子吸附、电化学反应以及光电化学反应的研究体系为模型,提取EC-SERS光谱所蕴藏的物理化学信息.通过对吡啶在电化学表面的吸附、水的吸附及其电化学反应、以及对巯基苯胺的电化学表面催化偶联反应等体系的研究,揭示了电化学表面吸附、反应和光电化学过程的本质.     

A new mechanism of Raman enhancement and its application

Strong electronic Raman bands corresponding to the transition between 4I9/2 and 4I11/2 manifolds of Nd3+, caused by a Raman-enhancement effect, are observed in the FT-Raman spectrum of Nd2O3. Neither resonance enhancement (RR) nor surface enhancement (SERS) accounts for the Raman enhancement observed here. We propose a new mechanism of Raman enhancement called the "feed-back" mechanism. A YAG laser excites the final state of the Raman transition (4I11/2 of Nd3+) to the 4F3/2 state and causes a significant decrease in the population of Nd3+ at the 4I11/2 state. This causes the population ratio of Nd3+ at 4I9/2 and 4I11/2 to deviate from the value required by Boltzmann's law. To restore equilibrium, Raman scattering is enhanced so that more Nd3+ ions are brought from the 4I9/2 state to the 4I11/2 state. This hypothesis gets support from the temperature-variable FT-Raman spectroscopic results. Additionally, obvious differences between the Stokes and anti-Stokes Raman spectrum of Nd3+ provide further evidence to support the feed-back mechanism. The Raman-enhancement effect confers on the electronic Raman bands a special ability to reflect the variation of coordinated structure around metal ions. The structural variations in polymer-metal ion composites and biomineralization systems have been investigated by using the electronic Raman bands.     

Fourier transform Raman spectrometry

Conclusions FT-Raman spectrometry has advanced significantly through the combination of CW Nd: YAG lasers, high sensitivity near-infrared detectors, and state-of-the-art filter technology. Obtaining fluorescence-free spectra through nearinfrared excitation has now become practical.Raman spectrometry provides data which is complementary in nature to infrared spectra and often helps provide unambiguous structural determination. Sample preparation, if necessary, is often easier than for the mid-infrared analysis. Sample categories for which Raman spectrometry can provide significant data include: aqueous soultions, catalysts [9], thin films, minerals and inorganics [10], and biological [9, 11] compounds, Typical scan times are 1 min or less. FT-Raman has truly become a powerful, general purpose analytical tool.     

Fluorescence properties of Nd3+-doped tellurite glasses

The compositional and concentration dependence of luminescence of the (4)F(3/2)-->(4)I(J) (J=13/2, 11/2 and 9/2) transitions in four Nd(3+)-doped tellurite based glasses has been studied. The free-ion energy levels obtained for 60TeO(2)+39ZnO(2)+1.0Nd(2)O(3) (TZN10) glass have been analysed using the free-ion Hamiltonian model and compared with similar results obtained for Nd(3+):glass systems. The absorption spectrum of TZN10 glass has been analysed using the Judd-Ofelt theory. Relatively longer decay rates have been obtained for Nd(3+)-doped phosphotellurite glasses. The emission characteristics of the (4)F(3/2)-->(4)I(11/2) transition, of the Nd(3+):TZN10 glass, are found to be comparable to those obtained for Nd(3+):phosphate laser glasses. The non-exponential shape of the emission decay curves for the (4)F(3/2)-->(4)I(11/2) transition is attributed to the presence of energy transfer processes between the Nd(3+) ions.     

Step-scan near-infrared Fourier-transform Raman spectroscopy with 100 picosecond laser pulses

Time-resolved Fourier-transform Raman scattering with picosecond excitation is reported for the first time. The resonance Raman spectrum of 9,10-diphenylanthracene in its excited single state was obtained by Raman excitation at 1064 nm with 100 ps pulses, following photoexcitation at 355 nm. The implementation and characterization of time-resolved FT-Raman spectroscopy with a step-scan interferometer is discussed. FT-Raman spectra generated with continuous and mode-locked beams in the continuous-scan mode of the interferometer are compared with step-scan FT-Raman spectra generated with 2 kHz pulses.     

Syntheses, structures, and spectroscopic properties of K9Nd[PS4]4, K3Nd[PS4]2, Cs3Nd[PS4]2, and K3Nd3[PS4]4

Four new quaternary alkali neodymium thiophosphates K 9Nd[PS 4] 4 ( 1), K 3Nd[PS 4] 2 ( 2), Cs 3Nd[PS 4] 2 ( 3), and K 3Nd 3[PS 4] 4 ( 4) were synthesized by reacting Nd with in situ formed fluxes of K 2S 3 or Cs 2S 3, P 2S 5 and S in appropriate molar ratios at 973 K. Their crystal structures are determined by single crystal X-ray diffraction. Crystal data: 1: space group C2/ c, a = 20.1894(16), b = 9.7679(5), c = 17.4930(15) A, beta = 115.66(1) degrees , and Z = 4; 2: space group P2 1/ c, a = 9.1799(7), b = 16.8797(12), c = 9.4828(7) A, beta = 90.20(1) degrees , and Z = 4; 3: space group P2 1/ n, a = 15.3641(13), b = 6.8865(4), c = 15.3902(13) A, beta = 99.19(1) degrees , and Z = 4; 4: space group C2/ c, a = 16.1496(14), b = 11.6357(7), c = 14.6784(11) A, beta = 90.40(1) degrees , and Z = 4. The structure of 1 is composed of one-dimensional (1) infinity{Nd[PS 4] 4} (9-) chains and charge balancing K (+) ions. Within the chains, eight-coordinated Nd (3+) ions, which are mixed with K (+) ions, are connected by [PS 4] (3-) tetrahedra. The crystal structures of 2 and 3 are characterized by anionic chains (1) infinity{Nd[PS 4] 2} (3-) being separated by K (+) or Cs (+) ions. Along each chain the Nd (3+) ions are bridged by [PS 4] (3-) anions. The difference between the structures of 2 and 3 is that in 2 the Nd (3+) ions are coordinated by four edge-sharing [PS 4] (3-) tetrahedra while in 3 each Nd (3+) ion is surrounded by one corner-sharing, one face-sharing, and two edge-sharing [PS 4] (3-) tetrahedra. The structure of 4 is a three-dimensional network with K (+) cations residing in tunnels running along [110] and [110]. The {Nd(1)S 8} polyhedra share common edges with four [PS 4] tetrahedra forming one-dimensional chains (1) infinity{Nd[PS 4] 2} (3-) running along [110] and [110]. The chains are linked by {Nd(2)S 8} polyhedra yielding the final three-dimensional network (3) infinity{Nd[PS 4] 2} (3-). The internal vibrations of both crystallographically independent [PS 4] (3-) anions of 2- 4 have been assigned in the range 200-650 cm (-1) by comparison of their corresponding far/mid infrared and Raman spectra (lambda exc = 488 nm) on account of locally imposed C 1 symmetry. In the Fourier-transform-Raman spectrum (lambda exc = 1064 nm) of 2- 4, very similar well-resolved electronic Raman (ER) transitions from the electronic Nd (3+) ground-state to two levels of the (4)I 9/2 ground manifold and to the six levels of the (4)I 11/2 manifold have been determined. Resonant Raman excitation via a B-term mechanism involving the (4)I 15/2 and (4)F 3/2 intermediate states may account for the significant intensity enhancement of the ER transitions with respect to the symmetric P-S stretching vibration nu 1. Broad absorptions in the UV/vis/NIR diffuse reflectance spectrum at 293 K in the range 5000-25000 cm (-1) of 2- 4 are attributed to spin-allowed excited quartet states [ (4)(I < F < S < G < D)] and spin-forbidden doublet states [ (2)(H < G < K < D < P)] of Nd (3+). A luminescense spectrum of 3 obtained at 15 K by excitation with 454.5 nm shows multiplets of narrow lines that reproduce the Nd (3+) absorptions. Sharp and intense luminescence lines are produced instead by excitation with 514.5 nm. Lines at 18681 ( (4)G 7/2), 16692 ( (4)G 5/2), 14489 ( (4)F 9/2), and 13186 cm (-1) ( (4)F 7/2) coincide with the corresponding absorptions. Hypersensitive (4)G 5/2 is split by 42 cm (-1). The most intense multiplet at about 16500 cm (-1) is assigned to the transition from (4)G 5/2 to the Stark levels of the ground manifold (4)I 9/2.     

Er2O3的光致发光光谱,吸收光谱和Raman光谱

在可见激光的激发下,Ｅｒ２Ｏ３粉晶样品的Ｒａｍａｎ光谱易受Ｅｒ＾３＋光致发光光谱的干扰。本文利用同一Ｒａｍａｎ光谱仪测得Ｅｒ２Ｏ３的高分辨可见光吸收光谱和激发光谱。     

Enhanced Raman spectrum of lawsone on Ag surface: vibrational analyses, frequency shifts, and molecular geometry

The surface-enhanced Raman spectrum of lawsone, a well known natural dye, has been investigated. Activation with KNO(3) or Na(2)SO(4) solution was necessary to enhance the Raman signal, whereas addition of NaCl solution depletes the effects. In the enhanced Raman spectrum, the strong double-bond stretching bands are most distinctive and show large red shifts from those in the infrared and FT-Raman spectra. The observed strong double-bond stretching bands reflect lawsone coordinated perpendicular to the Ag surface. DFT computations have been carried out for the plausible configurations of lawsone coordinated to an adatom on the Ag surface. Lawsone coordinated to an Ag(+) adatom with H(+) released best reproduces the observed vibrational characteristics.     

Investigation of concentration quenching and 1.3 microm emission in Nd(3+)-doped bismuth glasses

Nd(2)O(3)-doped 70Bi(2)O(3)-20B(2)O(3)-10SiO(2)-xNd(2)O(3) (x=0.1, 0.3, 0.5, 0.7, 1.0, 1.5 mol%) bismuth glasses were prepared by the conventional melt-quenching method, and the Nd(3+):(4)F(3/2)-->(4)I(13/2) fluorescence properties had been studied for different Nd(3+) concentrations. The Judd-Ofelt analysis for Nd(3+) ions in bismuth boron silicate glasses was also performed on the base of absorption spectrum. The transition probabilities, excited state lifetimes, the fluorescence branching ratios, quantum efficiency and the stimulated emission cross-sections of (4)F(3/2)-->(4)I(13/2) transition were calculated and discussed. Based on the electric dipole-dipole interaction theory, the interaction parameters: C(DD), for the energy migration rate (4)F(3/2), (4)I(9/2)-->(4)F(3/2), (4)I(9/2) and C(DA), for cross-relaxation rate (4)F(3/2), (4)I(9/2)-->(4)I(15/2), (4)I(15/2), and/or (4)F(3/2), (4)I(9/2)-->(4)I(13/2), (4)I(15/2) in bismuth boron silicate glasses were about 18.4 x 10(-40)cm(6)/s and 3.4 x 10(-40)cm(6)/s, respectively.     

Electronic and resonance Raman spectra of [Au2(CS3)2]2-. Spectroscopic properties of a "short" Au(I)-Au(I) bond

The anion [Au2(CS3)2]2- has an unusually short Au-Au distance (2.80 A) for a binuclear Au(I) complex. We report detailed Raman studies of the nBu4N+ salt of this complex, including FT-Raman of the solid and UV/vis resonance Raman of dimethyl sulfoxide solutions. All five totally symmetric vibrations of the anion have been located and assigned. A band at delta nu = 125 cm-1 is assigned to nu (Au2). The visible-region electronic absorption bands (384 (epsilon 30,680) and 472 nm (epsilon 610 M-1 cm-1)) are attributable to CS3(2-) localized transitions, as confirmed by the dominance of nu sym(C-Sexo) (delta nu = 951 cm-1) in RR spectra measured in this region. An absorption band at 314 nm (22,250 M-1 cm-1) is assigned as the metal-metal 1(d sigma*-->p sigma) transition, largely because nu sym(C-Sexo) is not strongly enhanced in RR involving this band. Observation of the expected strong resonance enhancement of nu (Au2) was precluded as a result of masking by intense solvent Rayleigh scattering in the UV.     

尿嘧啶和5-氯尿嘧啶1S0→1S2跃迁动态结构的共振拉曼光谱

采用含时量子波包理论的简单模型对5-氯尿嘧啶和尿嘧啶的共振拉曼光谱开展了强度分析拟合, 获得了1(π, π*)激发态的几何结构变化动态特征. 结果表明, 尿嘧啶1S0→1S2跃迁的动态结构特征因5-位氯原子取代而改变. 5-氯尿嘧啶的动态结构特征主要沿C5=C6伸缩振动+C6H12 弯曲振动和N3H9/N1H7弯曲振动+N1C6伸缩振动反应坐标展开, 而尿嘧啶的动态结构特征主要沿嘧啶环的伸缩振动+C5H11/C6H12/N1H7弯曲振动和C4=O10伸缩振动反应坐标展开. π和π*轨道中氯原子的pz电子参与嘧啶环的p-π共轭作用导致了在1(π, π*)激发态上5-氯尿嘧啶的振动重组能更多地配分给嘧啶环的弯曲振动模式和C5=C6伸缩振动模式. 尿嘧啶在甲醇中的激发态动态结构特征与在水中的基本一致, 但波包沿C5H11/C6H12/N1H7弯曲振动+N1C6伸缩振动(υ12)和环呼吸振动(υ17)反应坐标的运动明显增强.