Raman Academy - Read

Because of the structural use of polymers, it is important to understand the origin of their strength, elongation to break, elasticity, flexibility, and so on. It is in the very low frequency region (the so called “terahertz” range) where it is believed that the real indicators for crystallinity appear.

Raman Spectroscopy is a powerful and widely used analytical tool within the pharmaceutical industry. Excipients and active pharmaceutical ingridients (APIs) can be analysed within seconds, and extensive Raman spectral libraries allow easy chemical identification.

With the coming shortages in fuel, the issues of high carbon dioxide emissions, and the problems in waste disposal, society is now searching for alternative, sustainable energy sources. Biological materials are being targeted as attractive feedstocks. They are available in industrial and urban waste streams, in lumber and prairie grasses, and in agricultural products including agricultural waste. The major constituents of plant biomass from these sources are polysaccharides and lignin. To capture high-energy products from these materials, useful chemical forms have to be identified and isolated.

Due to the corona crisis, hand sanitizer became part of our daily routine. However, their use is not without potential risks because of their microplastics content. HORIBA offers all the tools necessary to analyze and characterize the presence of Microplastics in hand sanitizers: High-performance Raman microscopes, dedicated filtration kit, and especially the powerful particles detection software ParticleFinder™. We analyzed 3 samples of hand sanitizers, from different countries, and we were able to identify the different plastic content of each.

How can you navigate the maze of choices for detecting molecular vibrations with mid-infrared (IR), near IR (NIR), and visible (Raman)? Understanding what is being measured, how it is measured, and the advantages and disadvantages of each technique, will help.

The orientation of a crystal can be determined from the phase shift of the experimental P/O micro-Raman diagram relative to that calculated for a particular crystal face.

Leading experts generally base their certification of ancient artefacts on stylistic analysis and on personal sensory perceptions. However, greater objectivity is mandatory for identification and dating purposes. Different manufacturing technologies often result in products of very similar external appearance (from the visual and sensory points of view), but which differ completely in their micro/nanostructure.

The present study of mediaeval pigments using micro-Raman spectroscopy provides important information on the inorganic and organic type of pigments used in the wall paintings in the remains of the church in Skopsko Kale (Skopje Fortress).

We have measured solutions of lysozyme under conditions known to effect its physical state in order to investigate the potential of Raman spectroscopy as a non-invasive and label-free tool to assess protein formulation stability. Results from this study identified specific Raman signature bands in this protein that can be used to identify individual amino acid residues that are reflect structural changes in proteins.

We recorded the Raman spectra of NodaxTM (PHBHx-copolymer of hydroxybutyrate) biopolymer class with varying amounts of comonomer hydroxyhexanoate (Hx). The properties of Nodax is controlled by the amount of Hx added. Engineering the polymer for specific applications requires understanding the effects of Hx on the physical and chemical properties, and vibrational spectra provide a window on this information. Inspection of the structure of PHBHx indicates that the addition of Hx only replaces the methyl group with a propyl group on the hydroxyhexanoate segments of the polymer chains.

It is common for overlapping spectral lines to occur in Raman spectra. To the extent that analytical bands can provide physical or chemical meaning relevant to the material being studied, it becomes necessary to follow these spectral lines separately as sample parameters change. Anyone who has band-fitted spectra knows that the results are fraught with pitfalls. The most common one is to add a spectral component in order to improve the overall fit. The problem with this approach is that there may not be physical or chemical meaning to this extra component.

In a quiet NYC neighborhood, a frustrated artist created forgeries of America’s Modernistic masters. Raman Spectroscopy did him in.

The resonance Raman spectra of carotenoids vary with subtle changes on the functional side groups, making these spectra useful for identifying and characterizing carotenoids. Carotenoids serve multiple uses in biological systems ranging from visual pigments to antioxidants. Because the resonance Raman spectrum varies with subtle chemical changes on the functional side groups, the spectra of carotenoids have been used for identification and characterization.

The objective of the measurements is to identify the unknown components and their respective dispersion within pharmaceutical tabs by Raman and FT-IR microspectrometry.

The use of TERS to reveal the defects density in the structure of CNTs is of interest for a better understanding of the electrical properties of the devices made with such nano-objects. Not only defects concentration but also local chirality changes from the different radial breathing modes, pressure effect and strain distribution can be studied at the single carbon nanotube level through TERS.

Resulting from the combination of Raman spectroscopy and optical microscopy, Raman hyperspectral imaging has proven to be an indispensable tool in the pharmaceutical field, especially to study the distribution of active(s) and excipients in a pharmaceutical drug product.

The recent development of side-illuminated TERS analysis even provides the possibility to investigate the behavior of graphene-based structures under device operation.

Both TEPL and TERS images are well correlated with AFM morphological images obtained simultaneously, and all are consistent in revealing the nature (number of layers) of MoS2 flakes. Upon deconvolution, the TEPL signal is even capable of revealing local inhomogeneities within a MoS2 flake of 100 nm size. Kelvin probe measurement supports TEPL and TERS measurements and adds to the power of such tip-enhanced combinative tools.

Due to Covid-19, a wide choice of protective masks are now on the market. These types of masks are distinguished, in particular, by their different efficiencies linked to their filtration capacity. These differences in protective properties have therefore made it essential to characterize the composition of the masks. In this paper, we present why LabRAM Soleil™ confocal Raman multimode microscope is the perfect tool for studying the distribution and composition of mask fibers.

Raman spectra of celluloses modified for use in the pharmaceutical, food, and materials industries will be compared and analyzed, with the goal of determining spectroscopic features that can be of use in aiding in the determination of physical and chemical properties.

In this study we have chosen to investigate pyrite and its surrounding minerals in order to identify the different mineral phases as well as the chemical variations from micro- to nano-scale. Using the different microscopes instruments and being co-localized allows a comprehensive characterization of the sample and a precise superimposition of all the images.

The colour enhancement treatment on native brown and yellow diamonds can be highlighted by Photo Luminescence analyses performed with the Raman spectrometer LabRAM HR. The PL signature of green and violet diamonds has also been recorded. The defect centres responsible of the colour of the diamonds have all been detected and assigned. This proves the Raman spectrometer to be a very good tool to investigate the fine defects in the Diamond structure by Photoluminescence analysis.

Raman and photoluminescence spectroscopy and imaging are used to examine the spatial variation of solid state structure and electronic character of two dimensional (2D) WS2 crystals. Simultaneous acquisition of photoluminescence spectra with the Raman scattering provides complementary ways of rendering Raman and photoluminescence spectral images of thin film WS2.

Combined Raman and photoluminescence (PL) spectroscopy and imaging are used to examine the spatial variation of solid-state structure and electronic character of two-dimensional (2-D) tungsten disulfide (WS2) crystals. Simultaneous mapping acquisition of PL and Raman scattering from the same spatial locations provide complementary structural information and a way of rendering combinative Raman and PL spectral images of thin film 2-D crystals in general, and WS2 in particular.

The coupling of the power of confocal Raman microscopy to the inverted sampling geometry has enabled detailed investigations to be made of solvent and water based coating systems, providing important information on the processes and chemistry that occurs at the coating interface and within.

The atmosphere contains a large variety of particles in suspension (aerosols) that differ in chemical composition as well as in size distribution depending on the region of the atmosphere, the meteorological conditions and the anthropogenic activity. Their dimensions range from a few nanometers to tens of micrometers and their atmospheric life time can be as long as several weeks so that they can impact the global as well as the regional climates.

The performance of a Raman spectrograph for a particular application will depend, among other things, on its sensitivity and spectral resolution. The sensitivity will determine how long it will take to record a spectrum with a given signal-to-noise ratio. In turn, the grating reflectivity will determine the optical throughput of the instrument. The spectral resolution will determine how easy it will be to extract subtle information from a spectrum.

Many challenges remain before the promise of 2D materials is realized in the form of practical nano-devices. An information-rich, nanoscale characterization technique is required to qualify these materials and assist in the deployment of 2D material-based applications.

Raman microscopy has been attractive because of its ability to characterize materials on a spatial scale commensurate with optical microscopy. Typically, the lateral spatial resolution is quoted as determined by the Airy disk (1), which is 1.22λ/NA. λ is the wavelength of the illuminating light, and NA is the numerical aperture, which is equal to nsinθ, where n is the index of refraction of the medium (1.0 in the case of air) and θ is the angle subtended by the optics. However, it is interesting to this aging Raman spectroscopist that in recent years, the quoted spatial resolution of a Raman microscope has been getting smaller and smaller as more instrument manufacturers enter into the business of Raman microscopy.

The Raman spectra of elemental carbon materials are known to be sensitive to polymorphy. For hard carbon films, the spectra of amorphous and diamond-like carbons can be band-fit to separate the contributions of the "graphitic carbon" (G band) from the "disordered carbon" (D band). The spectral behaviour of carbon films has been empirically correlated with thin film physical properties such as hardness, durability, optical transparency, electrical conductivity, thermal conductivity and corrosion resistance, and can be of use for prediction of these properties without extensive alternative testing.

Decreasing turnaround time is a paramount objective in clinical diagnosis. We evaluated the discrimination power of Raman spectroscopy when analyzing microcolonies from nine bacterial and one yeast species directly on solid culture medium after a shortened incubation time of 6 h (compared to 24 hour for macrocolonies). This approach, that minimizes sample preparation and culture time, would allow resuming culture after identification to perform downstream antibiotic susceptibility testing.

Raman spectroscopy is a convenient method for probing the chemical bonding and solid state structure of crystals, and it is sensitive to the presence of dopants, impurities, and crystal defects in the host-crystal lattice. Here is what you need to know about how a hostcrystal Raman spectrum is affected by dopants and impurities.

Raman imaging provides detailed crystal orientation information for two-dimensional MoS2 prepared by chemical vapor deposition on silicon substrates. These two-dimensional crystals consist of individual atomic layers of sulfur, molybdenum, and sulfur atoms.

Depth profiles of a laminar material have been measured on a confocal Raman microscope with a selection of microscope objectives. It is well known that the quality of the profiles will depend on the quality of the focus, which requires matching the objective’s engineered properties with the properties of the material, particularly the effects of the indices of refraction. Depth profile comparisons performed with a series of objectives will illustrate how better matching improves the spatial resolution and chemical speciation in the depth profile.

Raman spectroscopy can be used to measure the vibrational spectra of both organic and inorganic materials. It is now well understood that Raman spectroscopy can provide information that is not available by other analytical means. This fact has sparked interest in the technique, yet many analysts remain uneasy because of their lack of knowledge or experience.

Resonance Raman spectroscopy demonstrates up to 106 signal enhancement. In this overview a detailed description of how resonance Raman spectroscopy differs from normal Raman spectroscopy is given with some specific examples explained.

Vibrational spectra are of interest to analytical and materials scientists because of their potential to yield nondestructively detailed information on materials. This is because the vibrations quite sensitively reflect interatomic bonding. There are several spectroscopies in which vibrational transitions can be detected. The simplest is infrared (IR) absorption. In this case, when a molecule is irradiated with photons whose energy corresponds to the energy of one of its vibrations (which is in the mid- and far-IR part of the electromagnetic spectrum), those photons will be absorbed.

Graphene is a new nanomaterial which may partially replace silicon in microcircuits and computer chips in the future. In order to better understand its quality characteristics, fast reliable techniques that deliver the right property measures are needed. Raman spectroscopy has emerged as a key technique for studying this exceptional material.

Graphene has potential applications ranging from computer monitors to solar cells, and Raman spectroscopy is a useful method for its characterization. Graphene, which consists of single layers of perfectly crystalline graphite, was first reported in Science in 2004 (1). It was were created by the "highly sophisticated" technique of peeling off layers of highly oriented pyrolytic graphite (HOPG). One might imagine that Geim and Novoselov and their colleagues were simply searching for a new interesting material, interesting due to the physical properties resulting from its two-dimensional nature.

We examine vapor-phase Raman spectroscopy through the acquisition of spectra from gas molecules confined to the headspace of sealed containers. Studying the Raman spectra of the liquid and vapor phases of compounds with different functional groups, degrees of hydrogen bonding, and polarity provides insight into the energetics of molecular interactions.

Spectral changes revealed by two-dimensional correlation spectroscopy can be used to interpret structural changes in polymers determined by processing conditions, so that materials can be rationally engineered for particular applications with known mechanical requirements.

The prevalence of allergies in the world is between 30 and 40%. Even though it exists medical treatments such as antihistaminic and desensitization this number is constantly increasing. Thus, in this application note, the identification and chemical characterization of aeroallergens by Raman microscopy will allow to prevent people who are affected by respiratory allergies of the presence of this type of allergens in indoor and outdoor air.

With the increase of allergic disorders over the past years, fast and reliable techniques for characterization and identification of pollen types are required. The presented examples demonstrate that Raman microspectroscopy can be successfully applied to the analysis and the identification of airborne pollen.

The Raman spectra of the various forms of elemental carbon are very sensitive to the type of nearest neighbour bonding, and to intermediate and long range order. In many cases Raman spectroscopy is the technique of choice for characterization of carbon materials. Correlation of Raman spectral features with tribological properties can facilitate the deposition of carbon films.

Vibrational spectroscopic characterization can take place all along the catalyst life from the control of the synthesis of the precursor to the cpntrol of the catalyst regeneration via the analysis of the surface reaction mechanism.

Confocal Raman spectroscopy is beginning to be recognized as a high potential technique for the non invasive study of biological tissues and human skin under in vivo conditions. Raman spectroscopy can be applied to obtain information regarding the molecular composition of the skin down to several hundred micrometers below the skin surface.

In this application note, SERS is used to study the behaviour of glycoprotein αIIbβ3 which plays a critical role in thrombosis (pathological blood clotting which can reduce or completely stop blood supply to tissues and organs, leading to myocardial infarction or stroke).

Review the band assignments of a protein spectrum, pointing out why it can be useful to know the band assignments when attempting to use the Raman spectra to understand the functionality of proteins. In fact, the American Chemical Society (ACS) has just issued a virtual issue of Journal of Physical Chemistry entitled “Protein Crowding and Stability,” discussing how the protein conformation impacts its biological functionality. I address how the Raman spectra can help with the determination of protein structure.

In several of my earlier columns I discussed the interpretation of Raman spectra. This column continues that theme, examining the spectra of a series of functionalized celluloses. It is interesting to see what is consistent from material to material, and what is different. In particular, it is useful to identify marker bands for the various functional groups. In addition, when identifying an unknown, it is important to identify a collection of functional group bands that would all be present when that functional group is part of a molecule.

A mouse model for human atherosclerosis has been developed in which the animals lack ApoE; these animals are called ApoE knock-out mice. These two measurements -the results of the aorta of an ApoE knock-out mouse and the results of the chemical study - indicate that the globule deposits contain cholesterol dissolved in fatty acid, and thus can be used as an early indicator of the atherosclerosis process in animal models during drug development.

Blending, an alternative method for engineering products that combines the properties of polymer types is a physical mixing. It has the advantage of being not only simple and inexpensive, but also allows for re-cycling used material. The first part of this note concerns the dispersion of the two components in a polyethylene-polybutylene terephthalate blend. The chemical imaging capabilities of the LabRAM will be used to get this information. The second part deals with the depth analysis of laminated films made of different polymer layers.

The spectral behavior of water is studied using Raman with an NIR spectrograph and dual wavelength lasers for measurements of both the fingerprint and the OH stretching regions. Raman spectra are recorded between 5 ⁰C and 80 ⁰C, and treated with both band-fitting and the 2D-COS algorithm revealing improved insights into the spectral behavior of water.

Micro-Raman spectroscopy has been used to depth-profile a waveguide produced by an ion-exchange reaction in a single crystal of a ferroelectric metal oxide, and to reveal the changes in chemical bonding and atomic structure that occur in this process.

In order to engineer materials with controlled diffusive properties, we need to be able to measure the diffusive process in situ. Ideally, we would like a technique that provides molecular information with resolution on a microscopic scale, that is non destructive of the samples, and can be set up and used on a laboratory bench top with a minimum of time and effort involved in sample preparation. Raman microprobe spectroscopy is an ideal candidate for this type of studies.

In the food industry, the compounds characterization is a critical step to ensure the quality of the products or to provide information to customers which can be sensitive to allergies. In this application note, we showed how optical spectroscopies and laser diffraction can help for food compounds characterization, especially on a specific product, i.e. milks.

One of the major challenges in the pharmaceutical development of a new product consists in its formulation, highly impacting the release and the efficiency of the active molecules in the body.

The scientific community is increasingly interested in environmental contamination by plastics. Recently, this interest in the contamination of aquatic systems by plastics has shifted to smaller particles, microplastics.

An imaging platform that combines Raman microscopy with enhanced darkfield and hyperspectral imaging technology was used to study lung tissue sections containing carbon nanotubes. It enabled easy identification of the regions containing the carbon nanotubes followed by spectroscopic characterization of chemical composition.

In this article, we present the combination of Raman spectroscopy, Photoluminescence and SEM-CL techniques, where the instruments weren’t physically connected. Smart nanostructured materials require a comprehensive understanding of their morphology, elemental and chemical composition. nanoGPS Suite solution allows a colocalized combination of a variety of microscopy techniques, providing a full characterization of nanostructured materials and a precise superimposition of the results obtained.

There are two types of vibrational modes in MoS2 (as in all layered structures): vibrational modes inside layers (intralayer) and modes resulting from the movements of complete layers (interlayer).

Metal oxides, in contrast to most metals, are wekk known to be easily distinguished by their characteristic Raman spectra; their presence can be detected on a scale of micrometers with a Raman microprobe.

In this article, we present how our Raman and X-Ray Fluorescence microscopies can be combined to shed some light on the origins of the universe. We show some examples on a meteorite piece and on water inclusion in quartz matrix.

Carbon materials are crucial due to their widespread application in industries like energy storage. Analyzing carbon helps ensure material quality and performance. However, its structural complexity and variability, such as the presence of defects and morphological disparities, pose challenges, making precise analysis difficult.

For the study of a pharmaceutical drug product, particle characteristics (count, size and chemistry) and compound distributions (size and spatial) are among key parameters that strongly determine the quality of the product due to their huge impact on the dissolution rate (and thus bioavailability) for the final solid dosage form. Laser diffraction and Raman microscopy were applied to highlight the benefits of combining two technologies for particle characterization.

Peak-fitting software is frequently written to offer the user a choice of automated peak fitting or one that allows the user to enter specific values of peak shape, amplitude, and width. The shapes are most often presented as a choice of percent Gaussian or Lorentzian profile contributions to the peak. To better understand these spectral profiles, we briefly explain the physical basis of the so-called spectral line shapes. Furthermore, we discuss and model the spectral shape, bandwidth, and broadening to help the reader see how the percentage of Gaussian and Lorentzian components contribute to overall peak shape and how two closely spaced and unresolved peaks of different amplitudes or bandwidths can affect the maximum position and overall appearance of the convolved peak.

In the final step of the formulation process, pharmaceutical and cosmetic industries have to control their products to check if the compounds' distribution in the final product, or in its application form, i.e. dispersed on a skin for an intracutaneous product, are homogenous and stable in order to guarantee the product's efficacy. In this paper, we present why confocal Raman microscopy is an excellent tool for product characterization after formulation.

Photoluminescence can provide information about the composition and solid state structure of a material. The high spectral resolution of a Raman spectrometer can be useful in performing photoluminescence spectroscopy of solid state materials, particularly when the emission spectra consist of narrow bands or even lines. Having the capability to perform photoluminescence and Raman spectroscopies simultaneously with the same instrument is advantageous, especially when studying 2D crystals. When used to perform photoluminescence spectroscopy, the Raman spectrometer becomes two instruments in one.

Since the physical state can affect the pharmaceutical behavior of drug substances, it is important to know what controls crystallization, solid state reactions, phase stability, and solubility.

During the last 5-10 years, the molecular solid state has gained recognition by the pharmaceutical industry for its role in drug manufacturing, stability, and activity. In addition, definition of the crystalline phase has become as important as molecular composition in patent protection.

Polarized Raman spectra are presented along with a discussion of the association of the symmetry species of the normal vibrational mode and the depolarization ratio of Raman scattering.

Bipolar plates are key components of proton exchange membrane fuel cells – they notably distribute fuel gas and air and conduct electricity. Various materials and surface treatments have been developed to improve their properties. Here, we described a reverse engineering study on a bipolar plate from a commercial vehicle using GD-OES and Raman spectroscopy. The analyses revealed that the plate had an amorphous carbon coating on a titanium base plate.

Disinfecting your hands with hydroalcoholic gel has become a daily practice. In the meanwhile, 70° alcohol has been used for even longer to disinfect wounds. But, to remain efficient, the alcohol concentration of these products must not be below a defined threshold and must be controlled. This application note demonstrates how to evaluate alcohol concentrations in a quality control process with Raman.

We all consume or have all consumed sugary drinks at least once. Sugar content of those drinks must be regulated. Also, to avoid those properties of sugar, it has been replaced by sweeteners. These have lower sweetness than natural sugars. Whether it is sugar or sweetener, their content just be controlled. Here, we demonstrate that Raman spectroscopy is one solution to identify and evaluate sugar/sweetener concentrations in a quality control process.

In this application note, Raman spectroscopy is explored as an easier and more flexible technique for quantifying common components in a CMP slurry, such as benzotriazole and glycine, without any sample preparation or costly consumables.

Raman spectroscopy is well known as a powerful analytical method for qualitative chemical analysis. Less well known is that under certain conditions Raman spectroscopy can also be an effective method for quantitative analysis. Here we demonstrate that capability for quantitative analysis under a variety of conditions, involving different solutes in a solution and solution mixtures, and its applications to pharmaceutical analysis such as content uniformity.

Raman Spectroscopy has many useful properties which can be explored and exploited in the analysis of pharmaceutical formulations.

Raman 2D-COS spectral data provide information on conformational changes of polymers. Here, Raman spectra of ethylene vinyl acetate and vinyl acetate copolymer are measured and interpreted, enabling a description of morphological changes related to the vinyl acetate group.

Laser processing provides a fast, non-contact and flexible method of modifying and patterning materials, from glasses to metals. Micro-machining, thin layers ablation, two-photon polymerization are just a few examples of what has already been demonstrated.

Traditionally, Raman has been a technique of the material scientist, physicist or chemist, but as instrumentation continues to evolve, the power of Raman in biological and medical applications is fast being realized, not least because of the high information content provided and an excellent tolerance for water.

Raman Spectroscopy was evaluated as a non-invasive method of analysis of sperm DNA and the influence of UV irradiation on the sperm. The results show that Raman Spectroscopy, combined with multivariate analysis provide the reproducible and accurate information on DNA of sperm and the effect and location of damage.

Raman and resonance Raman spectroscopy have proven to be important research tools to investigate structure-function relationships in enzymes.

Recent developments in Raman instrumentation have made the technique easier to use, more compact, and more affordable. Consequently, all of the demonstrated potential of the spectroscopy for industrial uses can now be exploited, including its use in combination with statistical methods for concentration calibrations.

Polarization/orientation (P/O) micro-Raman spectroscopy can be used to identify vibrational modes, determine crystal structure, distinguish allotropes and polymorphs, differentiate single from polycrystalline materials, and determine orientation of the crystal and degree of disorder, all on a micrometer scale. P/O micro-Raman spectroscopy promises to be an important analytical tool because of its complementarity to micro-X-ray diffraction.

Group theory in conjunction with Raman polarization selection rules may be applied to the study and characterization of crystalline materials. The Polarization–Orientation (P-O) Raman method employs this relationship, and is useful for the identification of a material’s crystal class, orientation, degree of disorder, and determination of the symmetry species to which the Raman bands in a spectrum belong.

Resulting from the combination of Raman spectroscopy and optical microscopy, Raman hyperspectral imaging has proven to be an indispensable tool in the pharmaceutical field. This article will broach a number of Raman hyperspectral imaging applications that were developed in our laboratory, in order to demonstrate the significance of the technique.

In recent years, core-shell particles have attracted significant attention due to their smart properties. Size, morphology, and composition are the key features that strongly affect the performance and suitable applications of such structures.

We have performed a complete Raman polarized study of a single GaN nanowire using a confocal microscope together with a high resolution stage. The high spatial resolution of our Raman confocal instrument together with a piezoelectric stage demonstrates unambiguously the possibility to image the optical properties of nano-objects with a resolution better than 200 nm keeping the fill advantage of the polarization control under a confocal microscope.

Using holographic techniques we have structured the surface in a one step procedure (no wet nor photocuring processing ) along the X and Y directions. A grating is first inscribed with grooves along the X direction, the sample is rotated by 90° and a second grating is inscribed with grooves along the Y direction. The intensity of the 1st diffracted orders is monitored to have equal intensities in both X and Y directions.

Fast and non-invasive methods for clinical and non clinical investigations for biological tissue are more and more required. Raman imaging at micro scale can answer to crucial questions about the monkey brain tissue morphology and structural evolution.

Identification of contaminating microbes is an important public safety issue in many fields such as the control of food quality and the manufacture of pharmaceutical and cosmetic products. Previous research has shown the potential for Raman spectroscopy in combination with chemometric methods to investigate bulk samples as well as a single bacterium and yeast cell for classification on the species and strain level.

The use of Raman spectroscopy to produce material images whose contrast is derived from chemical or crystallographic species has been seen as quite useful since the introduction of the Raman microscope in 1976, but particularly, more recently, with the development of more sensitive and easier-to-use instruments. When the various species in the field of view have spectra with non-overlapping analytical bands, simple univariate analysis can provide good images. When overlapping bands are present, multivariate techniques, especially MCR (Multivariate Curve Resolution), have been successfully applied. However, there are cases where even MCR results may be problematic. We will look at some maps of a ceramic composite containing SiC, Si, B4C, and Carbon, where each of these species has non-unique spectra to see what type of results flexible software can produce. What is the goal in this type of exercise? For some of us, creating images is like a teenager’s computer game. But really what we are trying to do is to extract information about a sample from its Raman image. A beautiful rendition is nice, but it must yield information. The following will show how Raman maps can provide useful information on a sample.

Raman analysis of a 50 μm section of a wheat grain kernel has allowed spectral features corresponding to starch, lipid and proteins to be identified. The distribution of these components on the micron scale has been studied using a Raman mapped image. Decomposition of the Amide I band allows a correlation between protein structures and grain hardness.

The processes involved in creating fibers from organic polymers — either man-made or natural — have the potential to orient the molecules in the fibers. Examination of a number of fibers confirms that orientation is a more or less ubiquitous phenomenon that can be detected and quantified by Raman microscopy. In addition, the presence of molecular orientation can mediate the crystallization process which can also be followed with the Raman signatures.

In the polymer field, Raman microscopy has become one of the most important characterization tools due to the large number of chemical and structural information which could be extracted from a single result.

We show Raman spectra of polymeric fibers acquired as a function of increasing stress and temperature. With knowledge of Raman band assignments, it becomes possible to understand, in detail, the molecular changes that are responsible for polymer orientation and crystallization.

Pharmaceutical and crystallographic samples typically require detailed characterisation and analysis to optimise a samples stability, physical properties and indeed general efficacy where an active drug substance is involved. Furthermore, strict regulatory and manufacturing procedures demand precise characterisation of a solid salt form drug candidate and the possible influence of environmental conditions. The hydration and structure of such samples under varying conditions is important in this full characterisation.

Controlling the orientation of the laser and Raman polarization relative to the sample orientation can provide a wealth of information in the Raman spectrum that would be difficult to achieve by other methods. Presentation of the spectra makes these effects appear straightforward, but because of multiple instrumental factors, and experimental design, it is easy to produce erroneous results. This column is going to explain what instrumental components affect the polarization effects that are observed, and how the sample setup itself affects the Raman signal.

Metal oxides often occur in crystals where there are no molecular units. Here, we provide an introduction to the concepts that need to be understood when analyzing metal oxides in materials such as paint, ceramic pigments, corrosion films, catalysts, and minerals.

We investigated in detail the Raman scattering of barium fluorohalides BaFX (X = Cl, Br, I) in an effort to characterize changes in structure and chemical bonding. The overall picture that emerges from the BaFX Raman data is that with the compositional change from X = Cl → Br → I, electron density shifts from the axial Ba-X bond to the equatorial Ba-X bonds with compositional change to the heavier halide, and that the charge distribution becomes more delocalized in the halide layers. This change in electron density indicates an increase in covalency of the Ba-X bonds from Cl to I.

Raman bands in the low energy region of the spectrum of crystals are attributed to so-called external lattice vibrational modes. The Raman bands from these external vibrational modes (low energy phonons) are very sensitive to crystal structure and orientation with respect to the incident laser polarization and to molecular interactions within the crystal. The low energy vibrational modes of many organic molecular crystals have very high Raman scattering cross-sections. Raman spectra and images of low energy phonons in so-called two dimensional (2D) crystals such as few-layer MoS2 reveal spatial variations in the solid state structure that are not evident in the higher energy bands.

The differentiation of polymorphs is important, particularly in the pharmaceutical industry. We demonstrate the practicality of using Raman spectroscopy to differentiate crystal forms for polymorph characterization and screening, and explain aspects of chemical bonding and solid state structure that affect the Raman spectra of crystal lattice vibrational modes.

The application note explains how the Raman Spectroscopy can be helpful in the analysis of cathodes and anodes in Li-ion batteries. Today’s state of art of technology requires more reliable, more efficient and powerful energy sources. Lithium-ion batteries are thus of high interest. Raman spectroscopy adapts to the different stages of life of these batteries, such as the characterisation of new materials for more flexible systems, failure analysis; but also more standard analysis of used material during charge/discharge process, including structural and electronic properties, and even robust, automated QC tests.

Here, we discuss the use of Raman spectroscopy to characterize oil shale, particularly black shale, which consists of kerogen (fossilized organic matter) trapped in sedimentary rock consisting of clays, calcites, silicates, and titanium dioxides among other inorganic minerals. We show that Raman spectroscopy is useful for characterizing the varieties of kerogen structure (chemical bonding and solid state), differentiating shales with different relative amounts of kerogen to inorganic mineral, and differentiating polymorphs of naturally occurring inorganic oxides.

Full and detailed characterization of pharmaceutical formulations is required before release of new drugs. When exposed to warm and humid weather over time, ingredients may undergo change in their hydration level, thus affecting the properties and/or efficiency of the drug. Raman spectroscopy, combined to a temperature and humidity controller can mimic such harsh conditions and can be used to monitor the properties of the different ingre-dients and track their modifications induced by environmental changes.

Raman spectroscopy can be used to determine the temperature of a material when other more direct means are either impractical or not possible. The material’s temperature can affect the peak position of Raman bands. When a Raman band shifts significantly with temperature, the monitoring of the peak position can be the most straightforward manner of determining temperature provided the Raman spectrometer has sufficient spectral resolution. Another method is to determine the temperature from the ratio of the Stokes and anti-Stokes signal strengths of a given Raman band. The latter method requires the ability to detect light at wavelengths longer and shorter than that of the laser and an accurate measurement of the wavelength dependent instrument response function.

Raman measurements can be used to infer the temperature of a material based on the Stokes and anti-Stokes band signal strengths, and by applying a predefined mathematical relationship. In reality, the temperature, Raman shift, and laser excitation wavelength all interact, and should be considered to better understand these measurements.

Plastic pollution from fishing gear is a global problem that harms the environment. Recycling of damaged or abandoned fishing gear is one way of mitigating the issue, however the exact nature of the polymer must be known in order to identify the correct recycling stream. In this paper, the MacroRAM benchtop Raman spectrometer with remote BallProbe® is used to quickly identify plastics used in various gillnet samples.

Raman spectra, in conjunction with Multivariate (Chemometric) Analysis, have been demonstrated to provide real-time information on the progress of a polymerisation reaction. As shown by this example, these results can provide unexpected information on the details of the reaction. in this case, the inequivalent reaction rates of the two monomers. Such information ultimately enables the process engineer to optimise his process.

Multilayer polymer films, composed of different materials, are used in a variety of industrial applications. The analysis of these multilayers is important to support, especially for safety and performances control. Here, we use Raman microscopy by cross-section analysis and confocal depth profiling to investigate the chemical composition of two multilayers films.

The presence of electronic transitions in the visible part of the spectrum can provide enormous enhancement of the Raman signals, if these electronic states are not luminescent. In some cases, the signals can increase by as much as six orders of magnitude. How much of an enhancement is possible depends on several factors, such as the width of the excited state, the proximity of the laser to that state, and the enhancement mechanism. The good part of this phenomenon is the increased sensitivity, but the downside is the nonlinearity of the signal, making it difficult to exploit for analytical purposes.

Resonance and off-resonance Raman spectroscopy and imaging are used to examine the spatial variation of the solid-state structure and electronic character of few-layer MoS2 flakes. Simultaneous acquisition of photoluminescence spectra with the Raman scattering provides complementary ways of rendering Raman and photoluminescence spectral images of thin-film MoS2.

Were it not for the problem of photoluminescence, only one laser excitation wavelength would be necessary to perform Raman spectroscopy. Here, we examine the problem of photoluminescence from the material being analyzed and the substrate on which it is supported. Selecting an excitation wavelength that does not generate photoluminescence reduces the noise level and yields a Raman spectrum with a superior signal-to-noise ratio. Furthermore, we discuss the phenomenon of resonance Raman spectroscopy and the effect that laser excitation wavelength has on the Raman spectrum.

Raman microscopy is a technique which has proven highly valuable in a wide range of applications. Within biomedical research, its relevance to highly selective identification of biomolecules including amino acids and proteins, DNA/RNA and chemotherapeutic drugs is fast being realised. However, the efficiency of Raman scattering is low, and collection times can be long, and detection limits high.

By coupling Raman spectroscopy with microscopy, it is possible to obtain full spectral information with a spatial resolution in the order of 1 µm. However, Raman is a weak phenomenon, and its sensitivity is not always ideal, particularly when analysing what are often relatively low concentration of intracellular components.

Raman has shown a high potential in characterizing the SWCNTs' structure. The correlation between knowledge about structure with physical and chemical properties about the tubes make the technique extremely powerful to control the quality of the SWCNTs for specific applications. Raman spectrometer capabilities like spatial resolution, spectral resolution and excitation wavelength versatility have been examined. Beside Raman, preliminary fluorescence studies are describing the potential of the technique.

In the soap industry, many chemical reactions are involved for the preparation of the final product. A hight control of the reactions is a major part of the quality control mission in these industries in order to ensure the non-invasivity of the final product on human skin.

A Raman spectrometer’s spectral resolution is determined by its spectral dispersion in conjunction with the entrance slit width. We explain the instrument design parameters involved.

This Application Note outlines three different kinds of spectroscopic tools being used for the characterization of sunscreens, and discusses the obtained results. These include Fluorescence spectroscopy for photoactivity, Particle Size analysis for composition and Raman microscopy for formulation investigation.

Raman spectroscopy is a very well suited technique to determine both Ge fraction and strain in SiGe layers and Si cap layers. Moreover the possibility of using both UV and visible excitation lines on the same instrument is essential to study structures made up of a Silicon cap layer on top of a SiGe layer. The relative Ge content in the constant Si1-xGex layer is calculated from the visible Raman spectrum and the strain of the cap Si layer is derived from the UV Raman spectrum.

Stress and strain are terms that are often used interchangeably when discussing the characteristics of materials. Nevertheless, their meanings are different. Stress is a force per unit area applied to an object, and strain is the effect on the object from the stress.

2D materials are state-of-the-art in nano- and opto-electronics. Characterizing their structural properties with a non-destructive approach at the micron scale is very important.

Natural rocks composing the Earth are complex. They consist of an aggregate of one or more minerals. Each mineral can be defined by its chemical composition and its crystalline structure and sometimes can also contain fluid inclusions. Geologists need a powerful characterization technique to get detailed information on the rock formation history.

Raman is usually thought of as a tool for studying molecular and crystalline structure; in this context it also can differentiate the amorphous phase from any number of crystalline phases. However, it is also known that Raman spectra of a crystalline phase can be acquired under conditions where X-ray crystallography indicates that the sample is amorphous. With the development of nanophase materials, Raman is exhibiting a unique capability for characterizing materials that are between crystalline and amorphous.

The application of vibrational selection rules is usually taught with respect to the vibrational motions of individual molecules. However, many of the materials studied by infrared or Raman spectroscopy are solids and even single crystals. Furthermore, some materials such as covalent or ionic solids have no molecular species associated with them. Consequently, there is a need to understand the application of group theory for the determination of spectroscopically active vibrational modes of crystals. The correlation method is ideal for that purpose.

The Raman spectra of a particular face of a single crystal can be significantly different if acquired with different microscope objectives. This article explains the underlying physics of changes in relative intensity and even peak position of certain Raman bands depending on the microscope objective used to acquire the spectrum.

The natural scientific identification of pigments has some problems because of their insolubility in common solvents. Especially when one deals with examinations of evry small sample amounts or wishes to perform non-destructive analysis, e.g. in forensic laboratories or analysis of art paintings. Raman spectroscopy turns out to be an ideally suited technique to solve these analytical problems.

It has been a problems for a long time for forensic scientists, customs officials and historians alike to be able to verify and authenticate printed documents just from the inks that have been used. It is a difficult and often impossible task to analyse an ink in-situ on a paper surface and techniques such as GC-MS and HPLC are fundamentally destructive requiring complicated extraction procedures to isolate the ink constituents before analysis.

Segmented channel waveguides have been fabricated in single crystal KTiOPO4 through a topotactic process of partial cation exchange. The ion-exchanged waveguides maintain the high nonlinear susceptibility of KTiOPO4 to function as frequency doubling laser light sources. We apply three dimensional (3D) Raman imaging to understand and characterize the changes to the chemical bonding and crystalline structure as well as measure the volumetric structure of the waveguide segments.

Segmented channel waveguides have been fabricated in single-crystal KTiOPO4 through a topotactic process of partial cation exchange. The ion-exchanged waveguides maintain the high nonlinear susceptibility of KTiOPO4 to function as frequency doubling laser light sources

The use of the transmission raman mode instead of the traditional backscattering one brings additional flexibility for the analysis of material, especially when averaged information of bulky samples is required.

This introduction to two-dimensional correlation spectroscopy (2D COS) illustrates how to understand the structural changes occurring in polyester molecules in the fibers as they are annealed under tension.

Any product used for medical purposes has to follow the adage “do no harm.” In the current work, we assess if and how Raman microscopy, in combination with X-ray fluorescence (XRF), can aid in the characterization of material leached from several implantable devices. The results show both the presence of metal oxides and organic compounds. In one case, two crystalline forms of an identical oxide existed simultaneously, and we suggest that such information may be useful in characterizing the oxidation of the metal. One of the samples was tinged pink, and its spectrum was consistent with a resonance Raman (RR) spectrum of a pigment.

In the last 30 to 40 years, various new types of carbon materials have been engineered for multiple industrial uses. It is now well-known that the Raman spectrum is sensitive to the structure, even though the spectrum is rather uncomplicated. Because Raman spectroscopy now has a reputation for providing good information, potential users of Raman equipment can request information on the quality of their sample.

As far as polymeric fibres are concerned, slight modifications of Raman features are directly related to differences in the molecular orientation and the degree of crystallinity of the fibres. To utilize these subtle spectral changes and correlate them with physical properties of the polymer, one is obliged to use Chemometrics on the Raman spectra.

Confocal Raman Spectroscopy is an important analytical tool in various fields and it has shown high efficiency for specific applications in the cosmetic and/or pharmaceutical fields. Its non-invasive behavior, and its high molecular sensitivity make it one of the preferred label-free analytical techniques to characterize materials such as skin and cosmetic products.

The study of vibrational spectra of linear alkanes has been used in the past to model the structure of polyethylenes. In particular, from these studies it has become clear that, in polyethylene, the longitudinal acoustic mode (LAM) frequency is inversely related to the length of polymer units between folds (lamellae), which is determined by sample history. This relationship had been developed by studying a series of linear alkanes. Spectra of samples of (C44H90), (C20D42), (C24D50), and (C36D74) are reported here. Although full spectra were recorded, we were more interested in the behavior in the low frequency region.

Pulsed RF Glow Discharge Optical Emission Spectrometry, coupled with the Ultra Fast Sputtering system, offers the Ultra Fast Elemental Depth Profiling of plastic thin films Polymer Mobile Screen Protection Covers. By coupling this technique with the Raman spectroscopy z-Scan analysis it is possible to acquire important information concerning the fabrication of smartphone screen protectors.

The Raman spectra of crystalline and amorphous solids of the same chemical composition can be significantly different primarily because of the presence or absence of spatial order and long range translational symmetry, respectively. The purpose or goal of this installment of Molecular Spectroscopy Workbench is to help readers understand the underlying physics that affect the Raman spectra of crystalline and amorphous solids. Wave vector, reciprocal space, and the Brillouin zone are explained with respect to Raman spectroscopy of solids.