Showing papers in "Journal of Raman Spectroscopy in 2012"
TL;DR: Raman spectra acquired from spherical SnO2 nanocrystals prepared by pulsed laser ablation and hydrothermal synthesis exhibit three oxygen-vacancy-related Raman modes at 234, 573, and 618 cm−1.
Abstract: Raman spectra acquired from spherical SnO2 nanocrystals prepared by pulsed laser ablation and hydrothermal synthesis exhibit three oxygen-vacancy-related Raman modes at 234, 573, and 618 cm−1. The peak location and intensity vary with annealing temperature under O2 finally approaching those of bulk materials. Density functional calculation discloses that the three Raman modes stem from subbridging, in-plane, and bridging oxygen vacancies, respectively. Raman spectra can thus be used to discern different types of oxygen vacancies in SnO2 nanocrystals. Copyright © 2012 John Wiley & Sons, Ltd.
164 citations
TL;DR: The miniaturisation of laser sources, charge-coupled device electronic control boxes and increasing Lap-top computer capacity led to a revolution in Raman spectrometry: measurements can be made outside the laboratory with transportable, mobile and ultramobile instruments, even in severe conditions as discussed by the authors.
Abstract: The miniaturisation of laser sources, charge-coupled device electronic control boxes and increasing Lap-top computer capacity led to a revolution in Raman spectrometry: Measurements can be made outside the laboratory with transportable, mobile and ultramobile instruments, even in severe conditions (e.g. rock shelter in mountains). However, many specific difficulties must be previously solved: The variety of mobile laser sources remains limited to red and green excitations, the positioning/focusing and protection against solar/bulb lighting are difficult and, more importantly, the spectral resolution and spectral window are limited. Nevertheless, the definition of good procedures and the use of advanced optics allow the on-site analysis of various cultural heritage materials: pigments of pastels, miniatures, drawings, glasses, enamels and glazes, rock art, crystalline and amorphous phases of pottery, enamelled glass artefacts or stained glasses, bronze and brass patinas, etc. Simultaneously, mobile instruments equipped with a telescope and pulsed Yttrium Aluminum Garnet laser are being implemented for planetary mission (Mars). The present state of the art and future development are discussed. Copyright © 2012 John Wiley & Sons, Ltd.
148 citations
140 citations
TL;DR: In this paper, the Raman spectrum of pure-phase U4O9 is described and interpreted, which is a superstructure of UO2, and a band at 630 cm-1 is interpreted as characteristic of clusters of interstitial oxygen atoms.
Abstract: Characterisation of uranium oxides in different conditions is a challenge both in nuclear and environment sciences. We focus here on U4O9, which is a superstructure of UO2. Homogeneous U4O9 powder was fabricated and characterised by Raman spectroscopy. The Raman spectrum of a pure-phase U4O9 is, for the first time, completely described and interpreted. U4O9 Raman spectrum derives from the well characterised one of UO2. Besides reminiscent modes of UO2, a band at 630 cm-1, which has a specific response to polarised light, was interpreted as characteristic of clusters of interstitial oxygen atoms. These experimental data will help to rationalise the interpretation of UO2 damaged samples. Copyright © 2011 John Wiley & Sons, Ltd.
129 citations
TL;DR: In this paper, the authors used micro-Raman spectroscopy to identify carbon-based pigments in two South American colonial paintings dated from the early 18th century and found that the characteristic bands at approximately 1580 and 1350 cm−1 showed a clear difference in position, width and relative intensity.
Abstract: Carbon-based black pigments are a wide group of dark-colored materials, which are classified according to the starting material used and their method of manufacture. Raman spectroscopy is an ideal technique for the characterization of carbonaceous matter: crystalline carbon materials present well-defined peaks, which can be easily assigned; amorphous carbon materials, on the other hand, show broad bands between 1300 and 1600 cm−1. The aim of this work was the discrimination between carbon-based pigments by micro-Raman spectroscopy. Five carbon-based pigments provided by Zecchi (lampblack, ivory black, bistre, bitumen, and graphite), two humic-earth materials [Van Dyck (Kremer) and Earth of Kassel (Zecchi)], and a commercial wood charcoal were studied. Raman spectra of all the samples showed the characteristic bands at approximately 1580 and 1350 cm−1; however, a clear difference in position, width, and relative intensity could be observed for most of the samples. The resulting analysis showed that micro-Raman spectroscopy allowed the discrimination of most of the reference pigments and allowed the identification of carbon-based black pigments in two South American colonial paintings dated from the early 18th century. Copyright © 2012 John Wiley & Sons, Ltd.
129 citations
TL;DR: A digital spectral library that comprehends almost 300 spectra of different SOPs is presented and was tested by means of non-invasive analysis of four contemporary paintings from the collections of the Stedelijk Museum voor Actuele Kunst (Ghent, Belgium).
Abstract: Identification of pigments in modern and contemporary arts is indispensable to determine correct conservation strategies, to study degradation processes and to answer authenticity-related questions. Since the early 20th century, the introduction of synthetic organic pigments (SOPs) has enormously increased the number of available pigments. Micro-Raman spectroscopy has proven to be the first line technique for the identification of these pigments, which often only show small variations on the same basic chemical structures. To ensure a correct identification, however, an as complete as possible library of reference spectra is needed. Although reference spectra of SOPs have been published before, they have always been limited to a certain number of pigments. Some publications discuss only one or a few chemical classes, and others are limited to a certain number of pigments belonging to different classes; none, however, have attempted to create an extensive library of commercially available pigments. Moreover, most of the reference spectra published so far are only available as small imprints or as peak lists and, as such, hardly usable for spectral matching algorithms. Often, flow charts have been developed on the basis of the pigments studied, to help in identifying unknown SOPs. In this paper, a digital spectral library that comprehends almost 300 spectra of different SOPs is presented. The library was tested by means of non-invasive analysis of four contemporary paintings from the collections of the Stedelijk Museum voor Actuele Kunst (Ghent, Belgium). Published flow charts have been evaluated in relation to digital search algorithms by using the extensive library of SOPs. To enable fellow research and conservation institutes to make use of these data, the nearly 300 reference spectra of synthetic organic pigments are available in digital format on http://modern.kikirpa.be. Copyright © 2012 John Wiley & Sons, Ltd.
104 citations
TL;DR: The spectral properties of agglomerated 30-nm Co3O4 nanoparticles have been studied in this paper, showing that the properties of these nanoparticles depend strongly on their agglieration state.
Abstract: The features of the Raman spectra of Co3O4 30-nm nanoparticles depend strongly on their agglomeration state. When measured at low incident laser power, the spectrum of isolated nanoparticles corresponds to that found in bulk materials, whereas the agglomerated nanoparticles present a clear red-shift and broadening of the Raman bands. On the other hand, when measured at even lower power, both agglomerated and isolated nanoparticles show the same spectrum of microscopic particles. These effects have been studied by variations of the 532-nm laser power and the environmental temperature. The thermal dependence of Raman spectra of agglomerated nanoparticles is different to that of isolated nanoparticles but is comparable to the one of bulk material. The different behaviour of the nanoparticles at different agglomeration state is associated to the transmission of phonons among the particles. On the other hand, an increase of the laser power causes a larger number of acoustic phonons, producing a variation of the vibration anharmonicity of the nanoparticles. This increase is more pronounced in the agglomerated nanoparticles, due to the transmission of phonons, causing a much intense modification of the Raman spectrum produced by the laser power. These results clearly indicate that the agglomeration state of the nanoparticles affects their Raman properties. Copyright © 2012 John Wiley & Sons, Ltd.
104 citations
TL;DR: In this article, the authors reported the synthesis of ultrathin and compact Au@MnO2 NPs, which can be applied in alkaline systems in which Au@SiO2 or Au@Al2O3 NPs cannot be applied.
Abstract: Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) based on Au@SiO2 or Au@Al2O3 nanoparticles (NPs) shows great potential to break the long-standing limitations of substrate and surface generality of surface-enhanced Raman scattering (SERS). However, the shell of SiO2 or Al2O3 can easily be dissolved in alkaline media, which limits the applications of SHINERS in alkaline systems. Besides that, the synthesis of Au@SiO2 NPs can be further simplified and Au@Al2O3 NPs be replaced by other NPs that are more amenable for mass production. In an attempt to make SHINERS NPs available in any systems practically, we report the synthesis of ultrathin and compact Au@MnO2 NPs. The shell thickness of MnO2 can be controlled down to about 1.2 nm without any pinhole. SHINERS based on such Au@MnO2 NPs exhibits much higher Raman enhancement effect than Au@SiO2 NPs and can be applied in alkaline systems in which Au@SiO2 or Au@Al2O3 NPs cannot be applied. Copyright © 2011 John Wiley & Sons, Ltd.
101 citations
TL;DR: In this article, the ability of the developed method to detect ethanol and methanol concentrations in real samples was also investigated, and the results of this developed method were compared with the experimental results from traditional method and high correlation value (R 2 = 0.926) was obtained.
Abstract: R 2 values of the calibration graphs proved the notable linear correlations (0.998 for ethanol and 0.998 for methanol). The method was validated based on linearity, sensitivity, intraday and interday repeatability, and recovery tests. The limit of detection and limit of quantification values of the validated method were determined for ethanol concentration as 1.2 and 3.7mM, and for methanol concentration as 3.4 and 10.3mM, respectively. The ability of the developed method to detect ethanol and methanol concentrations in real samples was also investigated. The results of the developed method were compared with the experimental results from traditional method and high correlation value (R 2 =0.926) was obtained. Besides being sensitive and cheap, the developed method is rapid with the analysis time of less than 30 s. Furthermore, it eliminates labor-consuming operations, chromatographic separation, and measurement error due to the high number of experiment steps in the standard method. Copyright © 2012 John Wiley & Sons, Ltd.
98 citations
TL;DR: In this paper, the authors used Raman spectroscopy to probe structural modifications in amorphous Ta2O5 coatings submitted to thermal annealing, and they performed Raman spectrum simulations in disordered and partially ordered Ta 2O5 from a phonon density of states.
Abstract: Many of the interesting properties that make Ta2O5 a strategic material for current and future applications in chemistry, microelectronics and optics, depend on its structural characteristics. In this work, we use Raman spectroscopy to probe structural modifications in amorphous Ta2O5 coatings submitted to thermal annealing. On the basis of previous knowledge on the crystalline material, we perform Raman spectrum simulations in disordered and partially ordered Ta2O5 from a phonon density of states. Calculated spectra are in good agreement with complex experimental spectra. Our original approach allows assignment of the vibrational features of the amorphous material, and quantitative interpretation of observed structural modifications in terms of ordering scales. In addition, it provides numerical indicators to analyse amorphous to crystalline phase transformation. Copyright © 2012 John Wiley & Sons, Ltd.
95 citations
TL;DR: In this article, a series of graphitized carbon materials, produced by the pyrolysis of an anthracene-based coke at temperatures ranging from 1600 to 2900 °C, were studied by Raman microspectroscopy to assess the applicability of this technique to the particular case of polished carbon materials.
Abstract: A series of graphitized carbon materials, produced by the pyrolysis of an anthracene-based coke at temperatures ranging from 1600 to 2900 °C, were studied by Raman microspectroscopy to assess the applicability of this technique to the particular case of polished carbon materials. The polishing process was shown to change significantly the first-order Raman spectra (D band intensity increase) and therefore to induce unacceptable errors in the characterization of the intrinsic structure of these materials. The deconvolution of Raman spectra, related to the unpolished graphitized carbons at varying temperatures, highlighted a linear relationship between the intensity ratio ID/IG and the G band width. Thus, as the latter appears to be insensitive to the polishing, we highly recommend using it for a reliable assessment of the intrinsic structural disorder of polished carbon materials. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this article, a detailed description of phase transitions occurring in the V2O5 composite electrode is provided by Raman spectroscopy, on the basis of a complete assignment of the spectra.
Abstract: The structural behaviour of the LixV2O5 active material in a composite electrode is determined upon lithium insertion/extraction in the 4–2.15 V potential range (0≤x < 2) using Raman microspectrometry. For the first time, a detailed description of phase transitions occurring in the V2O5 composite electrode is provided by Raman spectroscopy, on the basis of a complete assignment of the spectra. This approach has been successful because of the knowledge of the Raman fingerprints of the chemically lithiated compounds, combined with a rigorous and systematic deconvolution of the Raman spectra obtained for the electrochemically lithiated materials. The successive emergence of α, e, δ and γ phases is clearly established, as well as the α/e, e/δ and δ/γ biphasic regions corresponding to the 3.4, 3.2 and 2.3 V potential plateaus, respectively. This study shows that Raman spectroscopy constitutes a sensitive and relevant tool to explore the emergence of the various phases governing the electrochemical properties of cathode materials for lithium batteries. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, the peak position and full width at half maximum (FWHM) of the TiO2 anatase Raman bands located around 144, 398, and 638 cm−1 are influenced by crystallite dimension.
Abstract: TiO2 aerogels prepared by sol-gel method and followed by supercritical drying have been annealed at temperatures ranging between 400 and 550 °C. The obtained TiO2 anatase crystallites with the mean size between 6.4 and 13.9 nm, as obtained from transmission electron microscopy measurements, have been further investigated by Raman spectroscopy. It was found that the peak position and full width at half maximum (FWHM) of the TiO2 anatase Raman bands located around 144, 398, and 638 cm−1 are influenced by crystallite dimension. These spectral changes can be assigned to the combined action of several nanosize effects such as phonon confinement, phonon coupling, strain, and stoichiometry defects. Surprisingly, the best discrimination of the FWHM change with the nanocrystallite mean size was achieved for the 638 cm−1 band, whereas the best discrimination for the peak position was found for the 398 cm−1 band. The critical size values obtained from the peak position and FWHM evaluation were between 12.7 and 13.1 nm. Taking into consideration that only the phonon confinement and inhomogeneous strain can induce an asymmetric broadening of the Raman signal, the bands asymmetry was evaluated, and the critical size values of the nanocrystallites were determined to be between 10 and 11 nm. For a symmetric size distribution of TiO2 anatase crystallites with dimensions between 6.4 and 13.9 nm, the obtained result indicates that the phonon confinement contribution to the overall size effects is more than 75%. No evidence about the influence of the phonon coupling and vacancies on the Raman features was observed. The comparison of the data derived from the experimental analysis with those obtained by applying the theoretical phonon confinement model indicates the necessity of developing an improved phonon confinement model. The asymmetry approach can be applied for a great variety of nanostructures, as a measure of the confinement effect. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors compared the performance of three different spectral methods: conventional Raman, surface-enhanced Raman (SERS) and tip-enhance Raman spectroscopy (TERS) on gold and silver substrates.
Abstract: Although conventional Raman, surface-enhanced Raman (SERS) and tip-enhanced Raman spectroscopy (TERS) have been known for a long time, a direct, thorough comparison of these three methods has never been carried out. In this paper, spectra that were obtained by conventional Raman, SERS (on gold and silver substrates) and TERS (in ‘gap mode’ with silver tips and gold substrates) are compared to learn from their differences and similarities. Because the investigation of biological samples by TERS has recently become a hot topic, this work focuses on biologically relevant substances. Starting from the TER spectra of bovine serum albumin as an example for a protein, the dipeptides Phe–Phe and Tyr–Tyr and the tripeptide Tyr–Tyr–Tyr were investigated. The major findings were as follows. (1) We show that the widely used assumption that spectral bands do not shift when comparing SER, TER and conventional Raman spectra (except due to binding to the metal surface in SERS or TERS) is valid. However, band intensity ratios can differ significantly between these three methods. (2) Marker bands can be assigned, which should allow one to identify and localize proteins in complex biological environments in future investigations. From our results, general guidelines for the interpretation of TER spectra are proposed. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, BTA− film formation was investigated on single-crystal and polycrystalline Cu surfaces with shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) using silica-encapsulated Au nanoparticles.
Abstract: Benzotriazole (BTAH) is well known as an effective corrosion inhibitor for Cu because of its ability to make a coordination polymer film on the surface that provides a barrier to Cu oxidation. BTA− film formation was investigated on single-crystal and polycrystalline Cu surfaces with shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) using silica-encapsulated Au nanoparticles. Potential-dependent spectra display reversible film formation on polycrystalline Cu and irreversible film formation on single-crystal Cu. Grain boundaries leading to smaller BTA−-Cu oligomers are proposed to be the reason for cathodic degradation of the BTA− polymeric films on polycrystalline Cu. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: A review of the state-of-the-art tools currently available for intracellular SERS can be found in this paper, where various types of SERS probes are considered, including colloidal gold and silver nanoparticles, metallized optical fibers, and tip-enhanced Raman probes.
Abstract: Surface-enhanced Raman spectroscopy (SERS) is a promising and powerful label free technique for high resolution analysis of single cells. For intracellular analysis, there is a need for SERS-active nanoprobes that are minimally invasive to cells, do not affect cell viability, and provide reproducible signals. This work reviews the state-of-the-art tools currently available for intracellular SERS. Various types of SERS probes are considered, including colloidal gold and silver nanoparticles, metallized optical fibers, and tip-enhanced Raman probes. We also discuss recently developed SERS-active nanopipettes implemented on the basis of pulled glass microcapillaries. Finally, the critical aspects of selecting an optimal SERS nanoprobe for single-cell analysis depending on a particular application are summarized. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this paper, Raman scattering results of wurtzite ZnS nanowires, nanocombs, and nanobelts are reported, indicating that the residual strain varies during the morphological change to nanocomb and ultimately to nanobels.
Abstract: We report Raman scattering results of wurtzite ZnS nanowires, nanocombs, and nanobelts. The Raman spectrum obtained from ZnS nanowires exhibits first-order phonon modes at 272, 284, and 350 cm−1, corresponding to A1/E1 transverse optical, E2 transverse optical, and A1/E1 longitudinal optical phonons, respectively. Several multiphonon modes are also observed. The longitudinal optical phonon mode varies in wavenumber for nanocombs and nanobelts, indicating that the residual strain varies during the morphological change from ZnS nanowires to nanocombs and ultimately to nanobelts. Interestingly, a surface optical (SO) phonon mode varies in wavenumber depending on the shape and surface roughness of the ZnS nanostructures. The surface modulation wavelengths of the ZnS nanowires, nanocombs, and nanobelts are estimated using the SO phonon dispersion relations and the observed SO phonon wavenumbers. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors compare the performance of the time-domain Kramers-Kronig and maximum entropy approaches with respect to their ability to faithfully and robustly recover Raman spectra from coherent anti-Stokes spectroscopy spectra simulated to reproduce a range of scenarios.
Abstract: Phase retrieval methods are used to recover Raman spectra from multiplex and broadband coherent anti-Stokes Raman spectroscopy signals. Two methods are in widespread use, one based on maximum entropy, and one based on a modified time-domain Kramers–Kronig method. Here we compare these methods with respect to their ability to faithfully and robustly recover Raman spectra from coherent anti-Stokes Raman spectroscopy spectra simulated to reproduce a range of scenarios expected for experimental data and their efficiency. We find that the time-domain Kramers–Kronig and maximum entropy approaches perform in functionally equivalent ways, having only minor differences between them. Published 2012. This article is a US Government work and is in the public domain in the USA.
TL;DR: In this article, an effective interaction between the polyaniline and the carbon nanotube was proposed based on a polyanILine-to-nanotube charge transfer, which was shown to induce important changes in the electronic structure of the polymer, resulting in a more polaronic organization.
Abstract: Thin, transparent, and self-assembled films of neat polyaniline and polyaniline/carbon nanotube nanocomposites were deposited over glass substrates by interfacial polymerization. The effect of the carbon nanotubes on the structure and conformation of the polyaniline, and the type of interaction between the polymer and the nanotubes, have been studied by resonant Raman spectroscopy and UV–Vis and Raman spectroelectrochemistry. The results indicate clearly that the carbon nanotubes induce important changes in the electronic structure of the polymer, resulting in a more polaronic organization. Additionally, an effective interaction between the polymer and the nanotube, based on a polyaniline-to-nanotube charge transfer, is proposed in this work. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, it was shown for the first time that such Raman characterization has to be achieved at very low laser power to avoid formation of oxygen species by photolysis and analyze only the chemisorbed species.
Abstract: Raman spectroscopy is a powerful technique for detecting peroxo (O2)2– and superoxo (O2)– species adsorbed on defect sites of ceria. These sites are probed by reducing CeO2 at high temperature and then chemisorbing oxygen species at low temperature. In the present study, it is shown for the first time that such Raman characterization has to be achieved at very low laser power to avoid formation of oxygen species by photolysis and analyze only the chemisorbed species. Respecting this requirement, the (O2)2– and (O2)– species formed on 0.7% Pt/CeO2 compound, and the CeO2 support used to prepare it were compared after reduction for various times and at various temperatures. Superoxo species were more stabilized on reduced 0.7% Pt/CeO2 after short reduction at 773 K than on reduced CeO2. Additionally, the distributions of peroxo species adsorbed on defect sites of Pt/CeO2 and CeO2 were significantly different after long reduction at 773 K in spite of similar amounts. Indeed, less stable species were formed during the reduction of 0.7% Pt/CeO2. These two features revealed that new sites were created during the preparation and reduction of Pt/CeO2 compared to its bare support. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this paper, the results of field Raman analyses assisted by a hand-held energy dispersive-X-ray fluorescence spectrometer were used to experimentally determine the composition of compounds present in the walls and wall paintings of two Pompeian houses, one with many luxurious decorative elements and a more modest building (Regio IX, Insula 3, House 5/24).
Abstract: This work presents the results of field Raman analyses, assisted by a hand-held energy dispersive-X-ray fluorescence spectrometer, to experimentally determine the composition of compounds present in the walls and wall paintings of two Pompeian houses, one with many luxurious decorative elements (the House of Marcus Lucretius, Regio IX, Insula 3, House 5/24) and a more modest building (Regio IX, Insula 3, House 1–2). These houses were excavated 150 years ago, and the majority of the rooms have been exposed outdoors. The chemical attacks of the acid gases and the biological colonisation can be considered the most serious problems of the archaeological remains from Insula IX 3 of Pompeii. The walls and wall paintings exposed to the rain-wash are the worst preserved ones, probably due to a continuous cycle of SO2 attack to the original materials, involving loss of plaster. This severe decay was not observed in the rooms covered by roofs; in these last rooms, the most noticeable pathologies are the presence of high humidity in the walls and the elevated amount of efflorescences. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this paper, the microstructural changes of nanocrystalline CeO2−x annealed at different temperatures in the range 200-500 °C were investigated by X-ray diffraction and Raman spectroscopy.
Abstract: Nanocrystalline ceria (CeO2) is known for its ionic conductivity and oxygen storage properties, which depend on the presence of oxygen ion vacancies. The vacancies cause several important changes in CeO2 involving microstrain, electronic structure, magnetic properties, etc. In this article, we focus our attention to the microstructural changes of nanocrystalline CeO2−x annealed at different temperatures in the range 200–500 °C. Structural and vibrational properties were investigated by X-ray diffraction and Raman spectroscopy. It was observed that the content of oxygen vacancies changed significantly with increasing annealing temperature, which plays an important role in the observed microstructural changes of the annealed samples. We demonstrate that the observed microstrain changes, because of variable defect content, dominate over the crystallite size effect. This finding is opposite to the conclusions made by several other authors. A new mode, classified as a probable surface mode, was observed in the Raman spectra at ∼480 cm−1, the appearance of which can be explained by the large defective structure and disorder in the ceria lattice. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this article, surface-enhanced Raman scattering (SERS) was applied to Ag nanoparticles synthesized on porous silicon samples and applied as substrates for SERS applications on biological assays.
Abstract: Ag nanoparticles synthesized on porous silicon samples were studied and applied as substrates for surface-enhanced Raman scattering (SERS). The metallic nanostructures prepared by immersion plating were characterized by UV–Vis reflectance spectroscopy and scanning electron microscopy. SERS activity of the substrates was tested using Cyanine dye 1,3,3,1′,3′,3′-esamethyl-5,5′-dimethoxyindodicarbocyanine iodide (Cy5-OCH3) as a probe molecule. The Raman spectra obtained for different excitation wavelengths indicate amplifications ascribed to plasmonic resonances with an enhancement factor up to 107. CGIYRLRS peptides were chemisorbed on the Ag nanoparticles with the plasmonic resonance tuned at the excitation energy. Such oligopeptides were used as baits for a specific polyclonal antibody. The overall Raman enhancement allowed to evidence a good selectivity to the target analyte as required by most of the SERS applications on biological assays. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this article, the reproducibility of tip-enhancement effect on metallized silicon cantilever tips for characterization of carbon nanotubes has been improved for Raman spectroscopy.
Abstract: We have successfully improved the reproducibility of tip-enhancement effect on metallized silicon cantilever tips for characterization of carbon nanotubes. Plasmon resonance tuning relative to an excitation wavelength is crucial for efficient tip-enhancement, which is accomplished by thermal oxidization and subsequent metallization of commercial silicon tips. Because of the change of the refractive index of the tip from silicon to silicon dioxide, the plasmon resonance of the silver-coated tip is blue-shifted showing an enormous enhancement at 532 nm excitation. Highly reproducible tips exhibit an enhancement factor of >100 with a 100% yield. Because the tips are fabricated from commercially available silicon cantilever tips in a simple and robust way, our approach provides an important step of ‘tip-enhanced Raman spectroscopy for everyone’. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: Au/Ag core/shell bipyramids were used as surface-enhanced Raman scattering (SERS) substrates to determine the thiram in this paper.
Abstract: Au/Ag core/shell bipyramids were used as surface-enhanced Raman scattering (SERS) substrates to determine the thiram. The metallic substrates showed high SERS performance and are very suitable for the analytical sensors. The fabrication and characterization of the Au/Ag core/shell bipyramids were described. The influence of experimental parameters, such as the thickness of Ag shell of the bipyramids, sodium chloride concentration, and pH value on SERS of thiram was examined and optimized. Under the optimum conditions, thiram molecules were effectively adsorbed onto bipyramids and the SERS intensity is proportional to the concentration of thiram in the range of 3.3 to 400.0 ng mL–1. The corresponding correlation coefficient of the linear equation is 0.997, which indicates that there is a good linear relationship between SERS intensity and thiram concentration. The limit of detection for thiram is 2.0 ng mL–1. The experimental results indicate that the proposed method is a viable method for determination of thiram. Some environmental water samples were analyzed and the analytical results were satisfactory. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, Raman spectroscopic studies were performed to probe the tensile strain along the length of a bent ZnO nanowire and photoluminescence (PL) spectroscopy was used to investigate the stress in the bend.
Abstract: Raman spectroscopic studies are performed to probe the stress along the length of a bent ZnO nanowire. The zone-centre E2high optical phonon shows a systematic red shift as the junction point of the two arms of the nanowire is approached. The mechanism of the red shift is discussed on the basis of the tensile strain. From the red shift of the phonon peak position, the strain at different regions on the nanowire is estimated. Stress in the bent nanowire is also investigated using photoluminescence (PL) spectroscopy. Results of both Raman and PL study confirm that the bent nanowire is under tensile strain. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this article, the solid phase synthesis of Ag-coated Fe3O4 microspheres was elaborated under argon atmosphere and they were assembled into a surfaceenhanced Raman scattering (SERS) substrate holding clean and reproducible properties.
Abstract: The solid-phase synthesis of Ag-coated Fe3O4 microsphere was elaborated under argon atmosphere. This straightforward process utilized neither reducing agents nor electric current and involved the dry mixing of a precursor of CH3COOAg with Fe3O4 microspheres followed by heating in an inert atmosphere. Ag nanoparticles with diameters of 30–50 nm were well-decorated on the surfaces of Fe3O4 microspheres. The as-synthesized Ag-coated Fe3O4 microspheres were assembled into a surface-enhanced Raman scattering (SERS) substrate holding clean and reproducible properties under an externally exerted magnetic force. Using these nanoprobes, analyte molecules can be easily captured, magnetically concentrated, and analyzed by SERS. This clean SERS substrate was used to detect 4-aminothiophenol, even at a concentration as low as1.0 × 10–12 M. In particular, the Ag-coated Fe3O4 microspheres, acting as reproducible SERS substrates, were applied to detect methyl-parathion and 4-mercaptopyridine. Strong SERS signals were obtained with the analytes at a concentration of 1.0 × 10–6 M. The unique, clean, and reproducible properties indicate a new route in eliminating the single-use problem of traditional SERS substrates and show promising applications for detecting other organic pollutants. Similarly, this work may provide a new model system to a series of metal–Fe3O4 decorating reactions for a reproducible utilization. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this paper, a specially designed fiber-optic Raman probe with a ball lens was utilized for real-time, in vivo Raman measurements of various oral tissue sites (i.e. inner lip, attached gingiva, floor, dorsal tongue, ventral tongue, hard palate, soft palate, and buccal).
Abstract: Raman spectroscopy is an inelastic light scattering technique that is capable of probing biochemical and biomolecular structures and conformations of tissue. This study aims to characterize the in vivo Raman spectroscopic properties of different normal oral tissues in the fingerprint region (800–1800 cm−1) and to assess distinctive biochemical variations of different anatomical regions in the oral cavity. A specially designed fiber-optic Raman probe with a ball lens was utilized for real-time, in vivo Raman measurements of various oral tissue sites (i.e. inner lip, attached gingiva, floor, dorsal tongue, ventral tongue, hard palate, soft palate, and buccal). The semiquantitative non-negativity-constrained least squares minimization fitting of reference biochemicals representing oral tissue constituents (i.e. hydroxyapatite, keratin, collagen, DNA, and oleic acid) and partial least squares-discriminant analysis (PLS-DA) were employed to assess the significance of inter-anatomical variability. A total of 402 high-quality in vivo oral Raman spectra were acquired from 20 subjects. The histological characteristics of different oral tissues were found to have influence on the in vivo Raman spectra and could be grossly divided into three major clusterings: (1) buccal, inner lip, and soft palate; (2) dorsal, ventral tongue, and floor; (3) gingiva and hard palate. The PLS-DA multiclass algorithms were able to identify different tissue sites with varying accuracies (inner lip 83.1%, attached gingiva 91.3%, floor 86.1%, dorsal tongue 88.8%, ventral tongue 83.1%, hard palate 87.6%, soft palate 83.3%, and buccal mucosa 85.3%), bringing out the similarities among different oral tissues at the biomolecular level. This study discloses that inter-anatomical variability is significant and should be considered as an important parameter in the interpretation and rendering of Raman diagnostic algorithms for oral tissue diagnosis and characterization. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: The characterization of corrosion patinas on bronzes is preliminarily connected to the determination of proper conservation strategies and also provides an essential contribution to the comprehension of the mechanisms of formation of patinas as mentioned in this paper.
Abstract: The characterization of corrosion patinas on bronzes is preliminarily connected to the determination of proper conservation strategies. Moreover, it also provides an essential contribution to the comprehension of the mechanisms of formation of patinas.
Concerning the last aspect, several studies highlighted that bronze corrosion behaviour cannot be assimilated to that of pure copper. In particular, decuprification and relative enrichment of tin in the corrosion layers were observed. Tin therefore, together with its insoluble salts, plays an important role in the mechanism of formation of bronze patinas. Thus, the characterization of Sn-based corrosion products becomes fundamental, although remaining quite problematic. This work reports several case studies where Sn-based corrosion products grown in bronzes have been identified, thanks to the hyphenated system scanning electron microscopy–energy dispersive spectrometry–Raman structural and chemical analyser. Combining the main characteristics of these techniques, different Sn-containing compounds, mainly crystalline and nano-sized tin dioxides, were detected in bronze patinas exposed to different environments (to the atmosphere, in both natural and accelerated ageing conditions, and to the soil). The main issues regarding the interpretation of Raman spectra of these compounds are presented and discussed. Copyright © 2012 John Wiley & Sons, Ltd.