Raman Scattering Technique Research Articles

Комбинационное рассеяние света в кристаллах AlN, выращенных методом сублимации на затравках SiC и AlN

AbstractThe Raman-scattering technique is used to analyze the structural quality of bulk AlN crystals grown by sublimation on SiC and AlN seeds. Growth on SiC seeds is conducted with retention of the SiC seed during growth (type 1) and with total evaporation of the SiC seed (type 2). Growth on AlN seeds is conducted in tungsten containers with no graphite parts (type 3). According to the analysis of Raman spectra, the highest quality is inherent in type-3 crystals that exhibit minimal full widths at half maximum of Raman lines. The experimentally observed specific features are defined by differences in the mechanism of growth and by the content of dopant impurities in the crystals grown.

Structural and molecular response in cyclodextrin-based pH-sensitive hydrogels by the joint use of Brillouin, UV Raman and Small Angle Neutron Scattering techniques

The response to pH variation of polymeric cyclodextrin-based hydrogels has been investigated by a multi-technique approach based on UV Raman and Brillouin light scattering (BLS) together with Small Angle Neutron Scattering (SANS). By exploiting the complementary information of these three investigation methods, the structural, viscoelastic and molecular modifications of the polymer brought about by the pH changes have been examined, over a spatial range going from mesoscopic to nanoscopic length-scale. The data provide a picture where an increase of pH promotes the change of the characteristic size of the hydrophilic pores when the cross-linker has the suitable structural and acid-base properties, and leads to the reinforcement of the polymer domains interconnections, providing a stiffer gel network on the length-scale probed by BLS. Raman signals are sensitive both to structural changes of the polymer network and to changes of the intermolecular ordering of water due to solvent-polymer interactions. The destructuring effect on the tetrahedral ice-like configurations of water is especially evident at high pH, and might be ascribed to an increased exposition to the solvent of the ionic portions of the polymer surface.

High-Resolution Raman Spectra of Metformin

High-resolution spectra of molecular vibrations in metformin, one of the most widely used antidiabetic drugs, which also possesses antiaging and antitumor properties, have been obtained by a high-sensitivity Raman-scattering technique. It is established that rather narrow (4–10 cm–1) spectral lines observed in a 300–1200 cm–1 range can be used for separating spectral components corresponding to the vibrations of particular functional groups. This circumstance makes metformin an interesting model for studying molecular biosensors.

Novel platinum-based anticancer drug: a complete vibrational study.

The introduction of cisplatin to oncology, in the 1970s, marked the onset of the search for novel and improved metal-based anticancer drugs. Polynuclear PtII and PdII complexes with linear alkylamines as bridging ligands are a class of potential antineoplastic agents that have shown promising cytotoxicity against low-prognosis human cancers, such as metastatic breast adenocarcinoma and osteosarcoma. The present study reports an analysis of [μ-N,N'-bis(3-aminopropyl)butane-1,4-diamine-κ4N,N':N'',N''']bis[dichloridoplatinum(II)], [Pt2Cl4(C10H26N4)], denoted Pt2Spm (Spm is spermine), by vibrational spectroscopy coupled to theoretical calculations. Within the latter, the Density Functional Theory (DFT - mPW1PW/6-31G*) and Effective Core Potential (ECP - LANL2DZ) approaches were used, in order to ensure the most accurate representation of the molecule and achieve a maximum agreement with the experimental data. The solid-state geometry of Pt2Spm corresponds to Ci symmetry, displaying 132 vibrational modes. A complete assignment of the experimental vibrational profile of the system was attained through the combined application of complementary Raman, FT-IR and Inelastic Neutron Scattering (INS) techniques. INS allowed an unequivocal identification of the CH2 and NH2 rocking modes, not clearly detected by the optical techniques, while Raman measurements led to a clear discrimination of the Pt-N stretching frequencies from the two distinct Pt-N moieties within the chelate. The metal-to-metal distances calculated for the molecule under study were found to allow the establishment of effective inter- and intrastrand crosslinks with DNA. These results will hopefully help to clarify the mode of action of the compound, at the molecular level, contributing to the development of improved cisplatin-like chemotherapeutic drugs having a higher efficacy and specificity coupled to lower acquired resistance and deleterious side effects.

Рамановское рассеяние света высокого спектрального разрешения в метфоpмине

AbstractHigh-resolution spectra of molecular vibrations in metformin, one of the most widely used antidiabetic drugs, which also possesses antiaging and antitumor properties, have been obtained by a high-sensitivity Raman-scattering technique. It is established that rather narrow (4–10 cm^–1) spectral lines observed in a 300–1200 cm^–1 range can be used for separating spectral components corresponding to the vibrations of particular functional groups. This circumstance makes metformin an interesting model for studying molecular biosensors.

The time resolved SBS and SRS research in heavy water and its application in CARS

We present the time-resolved character of stimulated Brillouin scattering (SBS) and backward stimulated Raman scattering (BSRS) in heavy water and its application in Coherent Anti-Stokes Raman Scattering (CARS) technique. A nanosecond laser from a frequency-doubled Nd: YAG laser is introduced into a heavy water cell, to generate SBS and BSRS beams. The SBS and BSRS beams are collinear, and their time resolved characters are studied by a streak camera, experiment show that they are ideal source for an alignment-free CARS system, and the time resolved property of SBS and BSRS beams could affect the CARS efficiency significantly. By inserting a Dye cuvette to the collinear beams, the time-overlapping of SBS and BSRS could be improved, and finally the CARS efficiency is increased, even though the SBS energy is decreased. Possible methods to improve the efficiency of this CARS system are discussed too.

Immune response in peripheral axons delays disease progression in SOD1G93A mice.

BackgroundIncreasing evidence suggests that the immune system has a beneficial role in the progression of amyotrophic lateral sclerosis (ALS) although the mechanism remains unclear. Recently, we demonstrated that motor neurons (MNs) of C57SOD1G93A mice with slow disease progression activate molecules classically involved in the cross-talk with the immune system. This happens a lot less in 129SvSOD1G93A mice which, while expressing the same amount of transgene, had faster disease progression and earlier axonal damage. The present study investigated whether and how the immune response is involved in the preservation of motor axons in the mouse model of familial ALS with a more benign disease course.MethodsFirst, the extent of axonal damage, Schwann cell proliferation, and neuromuscular junction (NMJ) denervation were compared between the two ALS mouse models at the disease onset. Then, we compared the expression levels of different immune molecules, the morphology of myelin sheaths, and the presence of blood-derived immune cell infiltrates in the sciatic nerve of the two SOD1G93A mouse strains using immunohistochemical, immunoblot, quantitative reverse transcription PCR, and rotating-polarization Coherent Anti-Stokes Raman Scattering techniques.ResultsMuscle denervation, axonal dysregulation, and myelin disruption together with reduced Schwann cell proliferation are prominent in 129SvSOD1G93A compared to C57SOD1G93A mice at the disease onset, and this correlates with a faster disease progression in the first strain. On the contrary, a striking increase of immune molecules such as CCL2, MHCI, and C3 was seen in sciatic nerves of slow progressor C57SOD1G93A mice and this was accompanied by heavy infiltration of CD8+ T lymphocytes and macrophages. These phenomena were not detectable in the peripheral nervous system of fast-progressing mice.ConclusionsThese data show for the first time that damaged MNs in SOD1-related ALS actively recruit immune cells in the peripheral nervous system to delay muscle denervation and prolong the lifespan. On the contrary, the lack of this response has a negative impact on the disease course.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0732-2) contains supplementary material, which is available to authorized users.

Simulation of Natural Convection Heat Transfer of Nitrogen in a Cylindrical Enclosure

In this work we consider the numerical simulation of heat transfer by natural convection in a horizontal cylindrical cell, filled with nitrogen gas and heated by a tungsten filament situated on its axis. The gas temperature range is from 400K to the envelope of the lamp unto the 3000K near tungsten wire. These temperatures create large temperature gradients (up to 500K/mm) which produce complex patterns of currents circulating inside the cell. The physical principles governing this problem are modeled by the Navier-Stokes equations. These equations are solved numerically using the finite volume method. Numerical results show that the temperature gradients cause the generation of the thermal buoyancy force which induces a natural convection movement within the cell. The numerical results are in good agreement with those of an experimental study conducted by the Coherent Anti-Stokes Raman Scattering (CARS) technique with the same geometric, dynamic and thermal parameters.

Determination of melamine in milk using surface plasma effect of aggregated Au@SiO2 nanoparticles by SERS technique

A simple and rapid method to detect melamine in liquid milk by Surface-enhanced Raman Scattering (SERS) technique was presented. The pretreatment procedure of milk samples only contains hydrochloric acid treatment and twice centrifugation. In order to reduce the distortion about the Raman signals originating from charge transfer and electronic tunnelling effect, SiO2 shell-isolated gold nanoparticles (Au@SiO2 NPs) instead of Au NPs were employed to enhance signal intensity. Aggregation occurs when the Au@SiO2 NPs colloid is mixed with the melamine solution or the treated milk containing melamine. Different from aggregated Au NPs, these aggregated Au@SiO2 NPs on Cu substrate can undistortedly enhance the Raman signals of melamine using surface plasma effect. Quantitative analysis was tried and the results showed a good linearity (R2 ≈ 0.99) when the melamine concentration was between 0.5 mgL−1 and 5 mgL−1. The detection sensitivity satisfies the requirement of the Codex Alimentarius Commission and this method can be practically used for melamine detection in milk.

Fabrication of disposable flexible SERS substrates by nanoimprint

In this work, we report on the fabrication of disposable flexible substrates dedicated to the Surface-Enhanced Raman Scattering (SERS) technique. The transfer of pyramidal features elaborated on silicon wafers towards flexible plastic foil is performed via a two-steps nanoimprint process. Gold coated normal and inverted square pyramids patterned on the master silicon molds are reproduced with fidelity into a double-layer flexible plastic foil. SERS spectroscopy characterization was performed on the master SERS devices as well as on the final polymeric duplicated structures. Both, masters and replica, were shown to exhibit a good Raman signal enhancement. Moreover, this fabrication procedure was shown to be compatible with the use of large size substrates and well-mastered collective fabrication techniques. As a consequence, the developed SERS-active polymeric devices combine cost effectiveness and a high application potential in various detection and process control domains.

A new mobile and portable scanning lidar for profiling the lower troposphere

Abstract. An in-house developed mobile and portable three-dimensional scanning lidar system is discussed in this work. The system uses a stimulated Raman-scattering technique for the continuous observation of atmospheric aerosols, clouds and trace gases. This system has a fast scanning technique with a high-speed data acquisition, and permits the real-time measurement of atmospheric pollutants with the temporal resolution of 1 min. This scanning lidar system provides typical horizontal coverage of about 8–10 km while scanning; however, in zenith mode, good quality backscattered signals can be from 20 km, depending upon the laser power and sky conditions. This versatile lidar system has also overcome the drawbacks which are popular in the traditional scanning lidar systems such as complicated operation, overlap height between laser beam and telescope field of view In this system, the optical damage is reduced by using an integral coaxial transmitter and receiver. Some of the initial results obtained from the scanning lidar system are also presented. This study shows that boundary-layer structure and land–sea breeze circulation can be resolved from the developed scanning lidar system. The application of this lidar system to measure the pollutants over an industrial area is also discussed.

Analysis of Core-Shell-Isolated Nanoparticle Configurations Used in the Surface-Enhanced Raman Scattering Technique

Core-shell-isolated nanoparticles are commonly used in the surface-enhanced Raman scattering (SERS) technique to detect binding events and in analyte identification at the molecule level. In this paper, an opticalscattering theoretical model was used in which the core-shell-isolated nanoparticles are considerably smaller than incident light wavelengths, and the finite difference time domain method of numerical electromagnetics was adopted to compute the scattered opticalpower density per unit volume of the nanoparticles. In addition, the power densities were analyzed using various shell materials and the influences of differing parameters (i.e., the size of metal nanoparticles, shell thickness, nanoparticle size, and the distance between nanoparticles) on power-density functions were explored. The results indicated that when the nanoparticle shells were coated with silicon dioxide (SiO 2 ) and aluminum oxide (Al 2 O 3 ) to a thickness of 1 nm and the nanoparticle core was gold (Au), a particle size of 35 nm was the optimal design. The optimal distance between Au nanoparticles possessing SiO 2 shells was 5 nm and that between Au nanoparticles possessing Al 2 O 3 or titanium dioxide (TiO 2 ) shells was 10 nm. Based on the format results of nanoparticle arrangement, the distance between the shell-isolated Au nanoparticles was 10 nm and generated a stronger scattered power density with an asymmetric arrangement than that generated using symmetrically arranged nanoparticles. The advantage of the proposed method in this paper over the conventional method is its ability to relate the scattered power density to the required number of nanoparticles used in the SERS technique.

A Rapid and Sensitive Early Diagnosis of Influenza Virus Subtype via Surface Enhanced Raman Scattering

We have developed a novel, rapid, highly sensitive biosensor protocol for diagnosis and characterization of influenza viruses in the early stage of the epidemic. Using Surface-Enhanced Raman Scattering (SERS) technique and nitrocellulose membrane, detection limit as low as 30 ng/mL was achieved with high selectivity to different subtypes of influenza virus tested. Moreover, the SERS measurement can be completed in less than 2 h, thus making the protocol useful in early diagnosis and impediment of propagation of potential influenza pandemic.

Mapping multidimensional excited state dynamics using pump-impulsive-vibrational-spectroscopy and pump-degenerate-four-wave-mixing

Pump-impulsive vibrational spectroscopy (pump-IVS) is used to record excited state vibrational dynamics following photoexcitation of two carotenoids, β-carotene and lycopene, with <30 fs temporal resolution, and covering the full vibrational spectrum of the investigated chromophores. The results record the course of S2-S1 internal conversion, followed by vibrational relaxation and decay to the electronic ground state. This interpretation is corroborated by comparison with pump-degenerate-four-wave-mixing (pump-DFWM) experiments on the same systems. The results demonstrate the potential of both time-domain spectroscopic techniques to resolve photochemical dynamics, including fingerprint frequencies which directly reflect changes in bonding and structure in the nascent sample. The exclusive strengths and limitations of these two methods are compared with those presented by the frequency-domain Femtosecond Stimulated Raman Scattering (FSRS) technique, highlighting the complementary nature of the three, and the benefits of using them in concert to investigate vibrational dynamics in reactive species.

Application of Time-Resolved Coherent Anti-Stokes Raman Scattering Technique on the Study of Photocatalytic Hydrogen Production Kinetics

Based on the laser pulse output from a femtosecond regenerative amplifier and optical parametric amplifier (OPA), a broadband time-resolved coherent anti-Stokes Raman scattering (CARS) setup was assembled. Using this setup, the relationship of hydrogen CARS spectra to its amount in a mixture with air and the relevant detection time-delay were studied. Hydrogen CARS spectra without nonresonant background interference were obtained by adjusting the detection time-delay. The observed CARS intensity exhibited a linear relationship with the square of hydrogen concentration, which is consistent with the theoretical prediction. The signal-to-noise ratio showed that when the pressure of hydrogen-air mixed gas was 0.1 MPa, the detection limit of our setup was less than 0.2%. Using this setup, the hydrogen production kinetics of a platinum(II) terpyridyl acetylide molecular-cobalt catalysttriethanolamine (TEOA) system was studied. The kinetic mechanism of hydrogen production was discussed by considering the effect of changing pH. The results indicate that a high proton concentration will reduce the hydrogen production efficiency. This can be attributed to the inhibition of hydrolysis of TEOA under acidic conditions, because it is the electron and proton donor in this hydrogen production system. [Article] doi: 10.3866/PKU.WHXB201304281 www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2013, 29 (8), 1632-1638 August Received: January 31, 2013; Revised: April 28, 2013; Published on Web: April 28, 2013. ∗Corresponding author. Email: lmfu@chem.ruc.edu.cn; Tel: +86-10-62516604. The project was supported by the National Key Basic Research Program of China (973) (2009CB220008). 国家重点基础研究发展规划项目(973) (2009CB220008)资助 C Editorial office of Acta Physico-Chimica Sinica 1632 吕永钢等:利用时间分辨相干反斯托克斯拉曼散射技术研究光催化产氢反应动力学 No.8

TLC–surface enhanced Raman scattering of apomorphine in human plasma

Apomorphine is a well-known short-acting dopamine agonist typically used in the treatment of patients with advanced Parkinson's disease. In this work we propose a method for detection of apomorphine in blood plasma through Surface Enhanced Raman Scattering (SERS) technique. Detection can be achieved in a few minutes by simply depositing a drop of the blood plasma containing Apofin® on silica Thin Layer Chromatography (TLC) substrates and dropping the silver colloid on it. The Raman measurements carried out on the edges of the stain reveal the presence of the drug through its SERS signal which is found to significantly differ from the normal Raman spectrum. We propose a Density Functional Theory (DFT) model for the interpretation of the major SERS signatures of apomorphine in terms of the interaction of the drug molecule with silver.

Tracking Multiplex Drugs and Their Dynamics in Living Cells Using the Label-Free Surface-Enhanced Raman Scattering Technique

Label free and real time detection of nonfluorescent drugs inside living cells has been realized by using surface-enhanced Raman scattering (SERS). For the first time, the characteristics of 6-mercapotopurine and methimazole, two different drugs, were monitored simultaneously by SERS in living cells. Particularly, the processes of diffusion and metabolism of drugs occurring in the intracellular matrix were investigated. The results indicate that the metabolism speed of 6-mercapotopurine in living HeLa cells is much faster than that of methimazole. Moreover, the detection sensitivity of intracellular drugs has also been checked and a low detection limit of 1 nM was obtained of drug 6-mercapotopurine in a single HeLa cell.

Layered Composites of Polyvinyl Chloride and Carboxymethylcellulose Containing Uniformly Dispersed Individual Single-Wall Carbon Nanotubes

A. M. Prokhorov General Physics Institute, RAS, 38 Vavilov Street, 119991, Moscow, RussiaAn original method for forming a layered thermodynamically incompatible systems with the alternat-ing layers of a polyvinyl chloride (PVC) and a water-soluble polymer carboxymethylcellulose (CMC)with dispersed therein the single-wall carbon nanotubes (SWNTs) has been developed. Such struc-tures can be used to create a moisture- and heat-resistant nonlinear-optical elements. Analyses ofthe optical properties of nanocomposites obtained by the optical absorption and the Raman scat-tering techniques con“rm the presence in the nanocomposite individual (not coalescent in bundles)SWCNTs.

Intrinsic radial breathing oscillation in suspended single-walled carbon nanotubes

Radial breathing mode (RBM) oscillation is the most characteristic vibration mode in carbon nanotubes. Here we investigate the intrinsic behavior of RBM oscillations of structurally defined single-walled carbon nanotubes (SWNTs) by combining Raman-scattering and electron-diffraction techniques on the same suspended nanotubes. The independent determination of RBM frequencies and nanotube structures allows us to establish conclusively the perfect linear relation between RBM frequencies and inverse nanotube diameters, which has been long speculated to hold in pristine SWNTs. Understanding the intrinsic diameter dependence of SWNT RBM oscillation not only is crucial for reliable Raman characterization of carbon nanotubes, but also enables quantitative probing of SWNT-environment interactions through the RBM oscillation frequency shift.

Bi-analyte single molecule SERS technique with simultaneous spatial resolution

The simultaneous combination on CCD detectors of both spectral and spatial information is used in the framework of the single molecule (SM) bi-analyte Surface-Enhanced Raman Scattering (SERS) technique, to provide a new level of understanding on the origins of SM-spectra, as well as reveal the advantages and limitations of the statistical identification of SM-events. A new and deeper interpretation of the roots of the inhomogeneous broadening of single molecule Raman peaks can be uncovered, as well as the origin of Surface-Enhanced Fluorescence (SEF) emission by single molecules. In this manner, subtler aspects of SM-SERS spectroscopy can be revealed by the additional presence of spatial information on the localization of single molecules producing the signal. The spatial information is normally lost through the standard binning of CCD cameras for spectroscopy, which only emphasizes the spectral dimension of the problem. This novel extension of the bi-analyte SM-SERS method should contribute to the furtherance of the technique, and several of its fundamental aspects are discussed in detail.