Surface-enhanced resonance Raman scattering: Single-molecule detection in a Langmuir-Blodgett monolayer

Surface-enhanced resonance Raman scattering (SERRS) is used for single-molecule detection from spatially resolved 1-mum(2) sections of a Langmuir-Blodgett (LB) monolayer deposited onto a Ag film. The target molecule, his (benzimidazo) thioperylene (BZP), is dispersed in an arachidic acid monomolecular layer containing one BZP molecule per mum(2) which is also the probing area of the Raman microscope. For concentrated samples (attomole quantities in the field of view), average SERRS, surface-enhanced fluorescence (SEF), and Raman imaging, including line mapping and global images at different temperatures, were recorded. Single-molecule SERRS spectra, obtained using an LB monolayer, present changes in bandwidth and relative intensities, highlighting the properties of single-molecule SERRS that are lost in average SERRS measurements of mixed LB monolayers obtained at the same temperatures. Also, the dilute system phenomenon of blinking is discussed with regard to results obtained from LB monolayers. The dilution process used in the single-molecule LB SERRS work is independently supported by fluorescence results obtained from very dilute solutions with monomer concentrations down to 10(-12) M.

Coupling Surface-Enhanced Resonance Raman Scattering and Electronic Tongue as Characterization Tools to Investigate Biological Membrane Mimetic Systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vibrational spectra and surface-enhanced resonance Raman scattering of palladium phthalocyanine evaporated films

The vibrational spectra of palladium phthalocyanine (PdPc) evaporated thin solid films are reported, including the resonance Raman scattering, surface-enhanced resonance Raman scattering (SERRS) and SERRS mapping of the film surface using micro-Raman spectroscopy with 633 nm laser radiation. SERRS of PdPc was obtained by evaporating an overlayer of Ag nanoparticles on to the PdPc film on glass. The SERRS enhancement factor is estimated as similar to10(4) with reference to PdPc evaporated films on glass. The molecular organization of the PdPc evaporated films was probed using transmission and reflection-absorption infrared spectra. It was established that a random molecular distribution found in PdPc evaporated films is independent of temperature. No evidence of thermal degradation due to thermal annealing was found in the films. Electronic absorption and emission spectra are also discussed. Copyright (C) 2002 John Wiley Sons, Ltd.

Surface-enhanced resonance Raman scattering as an analytical tool for single molecule detection

A perylene derivative, n-(n-butyl)-n'-(4-aminobutyl) perylene-3,4,9,10-tetracarboxylic acid diimide (simplified as nBu-PTCD-(CH2)(4)-NH2) has been chosen as the target molecule for studies involving single molecule detection (SMD) using Raman scattering. The enhancement of the Raman signal is the result of the multiplicative effects of two phenomena, resonance Raman scattering (RRS) and surface-enhanced Raman scattering (SERS), which leads to the resulting surface-enhanced resonance Raman scattering (SERRS) process. The SERRS spectra from a single molecule have been collected using both silver and gold colloids. The SMD detection of the fundamental vibrational frequencies characteristic of nBu-PTCD-(CH2)(4)-NH2 is complemented with the detection of some overtones and combinations from ring stretching modes at the single molecule level. The background characterization of the ensemble vibrational spectroscopy of the target perylene and its SERRS is also presented, which includes the UV-vis absorption, experimental and calculated Raman scattering and infrared absorption, and molecular organization using reflection-absorption infrared spectroscopy (RAIRS).

Kinetics, electrochemistry and resonance raman spectra of the (2-mercaptopyridine) (edta)ruthenium(III) complex

The chemistry of the pentadentate edta complexes of ruthenium(III) and (II) with 2-mercaptopyridine (HSpy) has been investigated based on spectroscopic, kinetic and electrochemical techniques. The reaction of [Ru(III)(edta)H2O]- with HSpy proceeds with a specific rate of 1.05 × 104 M-1 S -1 (25°C, I = 0.10 M, acetate buffer), forming a red complex (λmax = 550 nm) which undergoes a relaxation process as a function of pH, with an apparent pKa = 4.35 and kobs = 0.31 S -1. The second reaction depends on the concentration of HSpy and leads to a stable green product (λmax = 630 mn). A pronounced enhancement has been observed in the Raman spectra of the complexes, particularly in the region of the metal-ligand vibrations. The electronic and resonance Raman spectra are consistent with the coordination of HSpy via the sulfur atom in the red complex, and with a chelate binding in the green species. © 1987.

Contracted GTF basis sets applied to the theoretical interpretation of the Raman spectrum of hexaaquachromium(III) ion

Contracted GTF basis sets designed with aid of the Generator Coordinate Hartree-Fock (GCHF) method for H(2S), O2-(1S), and Cr3+(4F) atomic species are applied to perform theoretical interpretation of the Raman spectrum of hexaaquachromium(III) ion. The 16s, 16s 10p, and 24s17p13d GTF basis sets were contracted to [4s] for H atom, [6s4p], and [9s6p3d] for O2- and Cr3+, respectively, by Dunning's scheme. For Cr3+, the [9s6p3d] basis set was enriched with f polarization function and used in combination com [4s] and [6s4p] in the study of our interest. The results obtained in this report show that the contracted GTF basis sets used are a useful alternative for the theoretical interpretation of Raman spectrum of hexaaquachromium(III) ion and that GCHF method is an effective alternative to selection of GTF basis sets for theoretical study of vibrational properties of poliatomic species. © 2003 Elsevier Science B.V. All rights reserved.

Single-wall carbon nanotube interactions with copper-oxamato building block of molecule-based magnets probed by resonance Raman spectroscopy

The electronic interactions between the [Cu(opba)]2- anions (where opba is orthophenylenebis (oxamato)) and single-wall carbon nanotubes (SWCNTs) were investigated by resonance Raman spectroscopy. The opba can form molecular magnets, and the interactions of opba with SWCNTs can produce materials with very different magnetic/electronic properties. It is observed that the electronic interaction shows a dependence on the SWCNT diameter independent of whether they are metallic or semiconducting, although the interaction is stronger for metallic tubes. The interaction also is dependent on the amount of complex that is probably adsorbed on the carbon surface of the SWCNTs. Some charge transfer can be also occurring between the metallic complex and the SWCNTs. Copyright (c) 2012 John Wiley & Sons, Ltd.

Time-resolved surface enhanced resonance Raman spectro-electrochemistry of heme proteins

The membrane protein Cytochrome c Oxidase (CcO) is one of the most important functional bio-molecules. It appears in almost every eukaryotic cell and many bacteria. Although the different species differ in the number of subunits, the functional differences are merely marginal. CcO is the terminal link in the electron transfer pathway of the mitochondrial respiratory chain. Electrons transferred to the catalytic center of the enzyme conduce to the reduction of molecular oxygen to water. Oxygen reduction is coupled to the pumping of protons into the inter-membrane space and hence generates a difference in electrochemical potential of protons across the inner mitochondrial membrane. This potential difference drives the synthesis of adenosine triphosphate (ATP), which is the universal energy carrier within all biological cells. rnrnThe goal of the present work is to contribute to a better understanding of the functional mechanism of CcO by using time-resolved surface enhanced resonance Raman spectroscopy (TR-SERRS). Despite intensive research effort within the last decades, the functional mechanism of CcO is still subject to controversial discussions. It was the primary goal of this dissertation to initiate electron transfer to the redox centers CuA, heme a, heme a3 and CuB electrochemically and to observe the corresponding redox transitions in-situ with a focus on the two heme structures by using SERRS. A measuring cell was developed, which allowed combination of electrochemical excitation with Raman spectroscopy for the purpose of performing the accordant measurements. Cytochrome c was used as a benchmark system to test the new measuring cell and to prove the feasibility of appropriate Raman measurements. In contrast to CcO the heme protein cc contains only a single heme structure. Nevertheless, characteristic Raman bands of the hemes can be observed for both proteins.rnrnIn order to investigate CcO it was immobilized on top of a silver substrate and embedded into an artificial membrane. The catalytic activity of CcO and therefore the complete functional capability of the enzyme within the biomimetic membrane architecture was verified using cyclic voltammetry. Raman spectroscopy was performed using a special nano-structured silver surface, which was developed within the scope of the present work. This new substrate combined two fundamental properties. It facilitated the formation of a protein tethered bilayer lipid membrane (ptBLM) and it allowed obtaining Raman spectra with sufficient high signal-to-noise ratios.rnSpectro-electrochemical investigations showed that at open circuit potential the enzyme exists in a mixed-valence state, with heme a and and heme a3 in the reduced and oxidized state, respectively. This was considered as an intermediate state between the non-activated and the fully activated state of CcO. Time-resolved SERRS measurements revealed that a hampered electron transfer to the redox center heme a3 characterizes this intermediate state.rn

Raman spectrum of group IV nanowires: influence of temperature

Group IV semiconductor nanowires are characterized by Raman spectroscopy. The results are analyzed in terms of the heating induced by the laser beam on the nanowires. By solving the heat transport equation one can simulate the temperature reached by the NWs under the exposure to a laser beam. The results are illustrated with Si and Si1-xGex nanowires. Both bundles of nanowires and individual nanowires are studied. The main experimental conditions contributing to the nanowire heating are discussed

Interaction between a laser beam and semiconductor nanowires: application to the raman spectrum of Si nanowires

One presents in this work the study of the interaction between a focused laser beam and Si nanowires (NWs). The NWs heating induced by the laser beam is studied by solving the heat transfer equation by finite element methods (fem). This analysis permits to establish the temperature distribution inside the NW when it is excited by the laser beam. The overheating is dependent on the dimensions of the NW, both the diameter and the length. When performing optical characterization of the NWs using focused laser beams, one has to consider the temperature increase introduced by the laser beam. An important issue concerns the fact that the NWs diameter has subwavelength dimensions, and is also smaller than the focused laser beam. The analysis of the thermal behaviour of the NWs under the excitation with the laser beam permits the interpretation of the Raman spectra of Si NWs, where it is demonstrated that temperature induced by the laser beam play a major role in shaping the Raman spectrum of Si NWs

Interaction between a laser beam and semiconductor nanowires: application to the raman spectrum of Si nanowires

One presents in this work the study of the interaction between a focused laser beam and Si nanowires (NWs). The NWs heating induced by the laser beam is studied by solving the heat transfer equation by finite element methods (FEM). This analysis permits to establish the temperature distribution inside the NW when it is excited by the laser beam. The overheating is dependent on the dimensions of the NW, both the diameter and the length. When performing optical characterisation of NWs using focused laser beams, one has to consider the temperature increase introduced by the laser beam. An important issue concerns the fact that the NW's diameter has subwavelength dimensions, and is also smaller than the focused laser beam. The analysis of the thermal behaviour of the NWs under the excitation with the laser beam permits the interpretation of the Raman spectrum of Si NWs. It is demonstrated that the temperature increase induced by the laser beam plays a major role in shaping the Raman spectrum of Si NWs.

Resonance fluorescence spectrum of a \Lambda-type quantum emitter close to a metallic nanoparticle

We theoretically study the resonance fluorescence spectrum of a three-level quantum emitter coupled to a spherical metallic nanoparticle. We consider the case that the quantum emitter is driven by a single laser field along one of the optical transitions. We show that the development of the spectrum depends on the relative orientation of the dipole moments of the optical transitions in relation to the metal nanoparticle. In addition, we demonstrate that the location and width of the peaks in the spectrum are strongly modified by the exciton-plasmon coupling and the laser detuning, allowing to achieve controlled strongly subnatural spectral line. A strong antibunching of the fluorescent photons along the undriven transition is also obtained. Our results may be used for creating a tunable source of photons which could be used for a probabilistic entanglement scheme in the field of quantum information processing.

光系统Ⅱ核心天线复合物CP43和CP47的分离纯化及其光谱学特性的研究

应用改进DEAE-Toyopearl 650S阴离子交换柱层析从高等植物菠菜(Spinacia oleracea)中分离纯化了核心天线复合物CP43和CP47。并对它们的纯度和完整性色素种类和含量，以及色素分子的结合状态进行了研究并对色素分子间的能量传递机制进行了讨论。结果如下： 1、HPLC检测结果表明：纯化的CP43和CP47均只含Chla和β-Car两种色素分子，并且，平均每分子CP43多肽含19-20分子Chla和4-5分子β-Car;而平均每分CP47则含20-21分子Chla和3-4分子β-Car。 2、以436nm和480nm激发光激发样品得到的CP43和CP47的低温荧光发射光谱的最大荧光发射峰分别位于683nm和693nm。进一步发现，CP43和CP47，在相同条件下分别以436nm和480nm激发光激发样品得到的低温荧光发射光谱经归一化后几乎完全重叠，而且400-500nm波长范围内的激发光扫描得到的三维低温荧光发射光谱沿激发轴具有较好的对应关系，表明纯化的CP43和CP47都具有较高的完整性。 3、纯化的CP43和CP47的吸收光谱的红区最大吸收峰分别位于671nm和674nm。该光区的导数光谱均分辨出偏蓝区和偏红区两个子峰，CP43的这两个子峰分别位于669nm和682nm;而CP47的两个子峰则分别位于669nm和680nm。进一步用包含这两个子峰的高斯解析参数对红区最大吸收峰进行拟合，结果证明，拟合的曲线与实测曲线几乎完全吻合，这表明，CP43和CP47均至少包含两种不同状态的Chla分子。 3．1应用不同的变性温度处理CP43，发现随变性温度的不断提高，其红区最大吸收峰的峰值逐渐减小，四阶导数光谱分辨出的两个子峰同时减小，但差光谱显示：随处理温度的不断提高，这两个组分峰值的变化并不同步进行，较低温度范围内(55℃以下)682nm吸收峰下降明显，而较高温度范围内(55℃以上)，669nm吸收峰下降明显。 同时，随处理温度不断提高CP43脱辅基蛋白的结构也在不断发生变化，其变化过程明显表现出两个跃变阶段。这两个跃变阶段分别出现在40～50℃范围内和55～60℃范围内，恰与吸收光谱两个组分峰变化的转变过程相一致。这证明，CP43中分别位于669nm和682nm的不同的色谱组分即代表两种不同结合态的Chla分子，分别简称为“CP43-669”和“CP43-682”。它们在色素蛋白复合物中所处的环境不同，因而对蛋白质结构的依赖性不同，前者更高地依赖于蛋白复合物的整体构象，而后者则主要依赖于蛋白质的二级结构。 3.2 经不同的变性温度处理的CP47，其红区最大吸收峰的峰位逐渐蓝移，而吸收峰值无明显的变化，只有当处理温度提高到65℃以后，蓝移后的吸收峰值(669nm)才开始明显减小;四阶导数光谱表现为680nm吸收峰的信号逐渐下降669nm的吸收信号逐渐明显;处理减对照差光谱只观察到680nm吸收值的逐渐减少，而几乎观察不到669nm吸收值的变化。同时，随变性温度的不断提高，CP47的脱辅基蛋白的结构也发生相应的变化与CP43不同，蛋白结构变化最大的温度范围为60℃～65℃之间，但同CP47的峰位蓝移、导数光谱中680nm信号的减小，以及差光谱中680nm吸收值的减小相一致。由此认为，同CP43一样，CP47的吸收光谱中分辨出的分别位于669nm和680nm处的两个不同光谱组分亦分别代表两种不同结合状态的Chla分子，分别简称为“CP47-669”和“CP47-680”，与CP43中的相应组分对应，它们处于不同的蛋白环境中，从而对蛋白质结构变化的依赖性不同。 3.3 CP43和CP47的CD光谱表现出明显的正负双峰，表明色素分子间存在较强的激子相互作用。随变性温度的不断提高，正负CD双峰的信号逐渐减弱，变化过程与脱辅基蛋白结构的变化以及CP43-682的变化相一致，表明色素分子间的激子相互作用更高依赖于CP43-682和CP47-680。并认为CP43-682和CP47-680可能以二聚体或多聚体的形式存在，并且二聚体或多聚体的形成依赖于蛋白天然构象。而CP43-669和CP47-669则以单体的形式位于蛋白结构中相对伸展的区域。并提出：在CP43-682以CP47-680分子之间，激发能主要以激子偶合机制进行而在CP43-669，CP47-669分子间及CP43-669至CP43-682间，CP47-669至CP47-680之间激发能则主要以Foster机制进行。 4、以488nm激发光得到的CP43和CP47的共振拉曼光谱都具有全反式构型类胡萝卜素分子的四个典型特征峰由此认为CP43和CP47中的β-Car分子亦具有全反式构型;与溶于丙酮抽体物中的β-Car分子相比较，CP43和CP47中的β-Car分子的共振拉曼光谱中具有较强的960cm~(-1)的拉曼峰，表明，CP43和CP47中的β-Car分子具有扭曲的构象。 应用经归一化后的吸收光谱与荧光激发光谱相比较的办法发现CP43和CP47中存在β-Car分子和Chla分子间的能量传递其能量传递效率分别为29.8～29.9%和52.3～56.9%。这表明，在正常条件下，CP47中β-Car分子和Chla分子间的能量传递效率远大于CP43。此外，当选用蛋白结构变化最明显的热变性温度处理样品后，发现，不论CP43还是CP47中β-Car与Chla分子间的能量传递效率大大降低，表明，这两种色素分子间的能量传递严格依赖于蛋白复合物的天然构象，并认为，正常条件下，CP43和CP47内β-Car与Chla分子间的空间距离较近，可能不大于10A，CP43和CP47相比较，CP47内这两种色素分子间的距离更近。并进一步提出，在CP43和CP47中，β-Car到Chla分子间的能量传递最大可能以Dexter的电子交换机制进行。

Electron paramagnetic resonance, optical absorption and Raman spectral studies on a pyrite/chalcopyrite mineral

Pyrite and chalcopyrite mineral samples from Mangampet barite mine, Kadapa, Andhra Pradesh, India are used in the present study. XRD data indicate that the pyrite mineral has a face centered cubic lattice structure with lattice constant 5.4179 Å. Also it possesses an average particle size of 91.9 nm. An EPR study on the powdered samples confirms the presence of iron in pyrite and iron and Mn(II) in chalcopyrite. The optical absorption spectrum of chalcopyrite indicates presence of copper which is in a distorted octahedral environment. NIR results confirm the presence of water fundamentals and Raman spectrum reveals the presence of water and sulfate ions.

Second order Coriolis resonance in the v2, v5 Raman bands of CH3F

The vibration-rotation Raman spectrum of the ν2 and ν5 fundamentals of CH3F is reported, from 1320 to 1640 cm−1, with a resolution of about 0.3 cm−1. The Coriolis resonance between the two bands leads to many perturbation-allowed transitions. Where the resonance is still sufficiently weak that the quantum number K′ retains its meaning, perturbation-allowed transitions are observed for all values of ΔK from +4 to −4; in regions of strong resonance, however, we can only say that the observed transitions obey the selection rule Δ(k−l) = 0 or ±3. The spectrum has been analyzed by band contour simulation using a computer program based on exact diagonalization of the Hamiltonian within the ν2, ν5 vibrational levels, and improved vibration-rotation constants for these bands are reported. The relative magnitudes and relative sings of polarizability derivatives involved in these vibrations are also reported.