Supergene uranyl molybdates (calcurmolite, iriginite and umohoite) from the Majerská valley U-Mo occurrence near Čučma, Slovakia: Mineralogy, chemical composition and Raman spectroscopy

Raman and Brillouin spectroscopy enable non-invasive assessment of chemical and elastic properties of biomaterials, respectively. In this report, Brillouin micro-spectroscopy was used for the time-resolved analysis of elastic properties of Populus and Geranium leaves, while Raman micro-spectroscopy was employed for the assessment of their chemical variation during drying. Spectroscopic assessment of elastic and chemical properties can improve our understanding of mechano-chemical changes of plants in response to environmental stress and pathogens at the microscopic cellular level. This report demonstrates the potential of multimodal optical sensing and imaging of plants as an emerging technique for the quantitative assessment of agricultural crops.

Properties of dentin, enamel and their junction, studied with Brillouin scattering and compared to Raman microscopy

Spectroscopic study on the influence of post-processing annealing on ZnO films produced with a sol-gel method

Raman and FTIR spectroscopy in determining the chemical changes in healthy brain tissues and glioblastoma tumor tissues.

In the biomedicine field, scientists act as detectives working hard to unravel the mysteries surrounding cells. To this end, Raman spectroscopy has revealed itself particularly useful, providing information concerning both the chemical composition and the structural conformation of the investigated samples. If compared to many other techniques devoted to the identification of microorganisms (as for instance fluorescence spectroscopy), Raman spectroscopy presents the relevant advantage of providing sharp peaks correlated to vibrational modes of the investigated sample. Moreover, it is a noninvasive technique, not requiring the addition of chemical agents or labels for a sample identification. Therefore, Raman spectra behave as the fingerprints of the analyzed sample. Hence, the Raman spectroscopy technique represents a powerful tool to detect cellular transformations in real time, contributing to elucidate many biochemical processes even in living cells. However, the analytical capabilities of Raman spectroscopy are limited by its inability to manipulate, and therefore analyze the samples without making physical contact or disturbing their unique environment. This limitation has been resolved by coupling Raman spectroscopy to a technology called Optical Tweezers (OT). The new method, termed Raman Tweezers (RT), employs Optical Tweezers to trap a microsized object in order to confine its motion for Raman spectroscopic analysis. Optical Tweezers are based on the force exerted on micrometer-sized particles by a strongly focused laser beam. They allow trapping and manipulation of single particles without any mechanical contact. Laser Quantum Product Ventus IR Institute UNIVERSITA DI NAPOLI FEDERICO II DipartimentodiScienzeFisische Availability http://www.fedoa.unina.it/3494/

Raman spectrometers will form a key component of the analytical suite of future planetary rovers intended to investigate geological processes on Mars. In order to expand the applicability of these spectrometers and use them as analytical tools for the investigation of silicate glasses, a database correlating Raman spectra to glass composition is crucial. Here we investigate the effect of the chemical composition of reduced silicate glasses on their Raman spectra. A range of compositions was generated in a diffusion experiment between two distinct, iron‐rich end‐members (a basalt and a peralkaline rhyolite), which are representative of the anticipated compositions of Martian rocks. Our results show that for silica‐poor (depolymerized) compositions the band intensity increases dramatically in the regions between 550–780 cm−1 and 820–980 cm−1. On the other hand, Raman spectra regions between 250–550 cm−1 and 1000–1250 cm−1 are well developed in silica‐rich (highly polymerized) systems. Further, spectral intensity increases at ~965 cm−1 related to the high iron content of these glasses (~7–17 wt % of FeOtot). Based on the acquired Raman spectra and an ideal mixing equation between the two end‐members we present an empirical parameterization that enables the estimation of the chemical compositions of silicate glasses within this range. The model is validated using external samples for which chemical composition and Raman spectra were characterized independently. Applications of this model range from microanalysis of dry and hydrous silicate glasses (e.g., melt inclusions) to in situ field investigations and studies under extreme conditions such as extraterrestrial (i.e., Mars) and submarine volcanic environments.

The types of structural elements and chemical bonds forming an amorphous matrix of chalcogenide glassy semiconductors of the As–Ge–Se system and changes occurring in them depending on the chemical composition are determined using a method for studying the Raman and transmission spectra and density measurements. It is shown that a transition from the elastic to isostatic state and then to the stressed-rigid state occurs in the system under study with increasing arsenic and germanium contents. The observed changes in the Raman spectra and the features of the dependences of optical and other parameters on the chemical composition are explained within the chemical-ordering model, taking into account the existence of local states near the allowed band boundaries.

The types of structural elements and chemical bonds forming an amorphous matrix of chalcogenide glassy semiconductors of the As–Ge–Se system and changes occurring in them depending on the chemical composition are determined using a method for studying the Raman and transmission spectra and density measurements. It is shown that a transition from the elastic to isostatic state and then to the stressed-rigid state occurs in the system under study with increasing arsenic and germanium contents. The observed changes in the Raman spectra and the features of the dependences of optical and other parameters on the chemical composition are explained within the chemical-ordering model, taking into account the existence of local states near the allowed band boundaries.

Profiling differences in chemical composition of brain structures using Raman spectroscopy

The use of Raman and TRLF spectroscopy for differentiating early stage alteration products of spent nuclear fuel

Raman spectroscopy has developed significantly since its discovery and has become an important analytical vibrational technique for investigating the sample’s chemical and structural properties. Today, great emphasis is placed on detecting low-concentrated samples of small volumes, which is a problematic task considering the weak intensity of the Raman signal. To improve the sensitivity significantly, resonance Raman spectroscopy and surface-enhanced Raman spectroscopy were employed. However, they face certain limitations and cannot generally be applied to any molecule. Here, we focus on drop coating deposition Raman (DCDR) spectroscopy that offers a general solution. DCDR lies in a droplet deposition of a liquid sample on an ideally solvophobic substrate where the subsequent drying process results in a preconcentrated deposit. After focusing on the preconcentrated dried parts in the deposit under the Raman micro-spectrometer, this offers high-quality classical Raman spectra even from a low-concentrated sample. Besides the overview of the method, its potential and the applications to biomolecules, biologically significant molecules and contaminants will be discussed.

As the improvement in the nanoscience and nanotechnology, the synthesis and technology for the fabrication of nanosized materials have great development and become more complete than the past few years. In addition, it also has more structural changes in its dimensionality and size. In this thesis, four kinds of different one-dimensional semiconducting nanomaterials have been successfully fabricated using different physical or chemical synthetic methods and these nanomaterials are single-crystalline silicon nanowires, amorphous silicon dioxide nanotubes, single-crystalline tin dioxide nanobelts and single-crystalline copper indium diselenides nanorods. By mixing the pure silicon powders and the catalysts (including metal or silicon dioxide powders) and with assistance for the laser ablation technology, the single-crystalline silicon nanowires (SiNWs) can be fabricated with the diameters reach 5-40 nm and the lengths extend to tens of micrometers. While the metal powders (like Fe, Ru and Pr) are used as the catalysts for the syntheses of SiNWs, the most stable Si {111} facets are grown and the growth direction for the SiNWs is parallel to the facets growth direction, i.e., the wire growth direction is for the metal-catalyzed SiNWs. Such SiNWs are grown via the typical vapor-liquid-solid (VLS) growth mechanism that existing the eutectic liquid droplet formation during the synthesis. On the other hand, as the silicon dioxide (SiO2) used as the catalysts for the fabrication of SiNWs, the Si {111} facets also grow; however, the wire growth direction, as the direction, is perpendicular to the lattice plane growth direction. The SiNWs catalyzed by SiO2 follow an oxide-assisted (OA) growth mechanism during their growths. Furthermore, based on the different chamber pressure used during the experiments, it can be found that with the increasing of the pressure, the diameters for SiNWs enlarge and the lengths for SiNWs shorten. The Raman spectra for the different diameter SiNWs are measured and the most intense F2g phonon mode, which is located ~ 520 cm-1, can be found that with decreasing for the diameter of SiNWs, the red-shifted behavior of the F2g mode is clearly seen from the corresponding Raman spectra. By using the chemical vapor deposition method, the one-dimensional silicon dioxide nanotubes (SiO2NTs) are produced on the silicon substrate coated with Au nanoparticles which are preannealed at high temperature. The SiO2NTs can reach to 40-100 nm in diameters and extend to few micrometers in lengths. According to the electron diffraction (ED) pattern for the SiO2NTs, it can be confirmed that these nanotubes are amorphous. Besides this, the nanotubes can be separated into two groups, as thick- and thin-walled SiO2NTs, based on their different synthesis temperatures. Moreover, with the different reaction temperatures, the different shapes of Au nanoparticles are grown and this causes the different thicknesses of the SiO2NTs. With detailed analysis on the SiO2NTs, it can be figured out that the SiO2 species are diffused from the Au {111} facets and the walls of SiO2NTs are along the direction of the thick-walled SiO2NTs while the direction of the thin-walled SiO2NTs. Moreover, with the higher reaction temperature, the amorphous silicon dioxide nanowires (SiO2NWs) are synthesized on the silicon substrate. The Raman spectra of SiO2NTs and micro-crystallite SiO2 powders are taken and used for the characterization and both have the intense Raman peak (Si-O phonon mode) at ~ 467 cm-1. With the thermal evaporation-condensation method, the high purity single-crystalline tin dioxide nanobelts (SnO2NBs) are fabricated via the thermal heating of tin monoxide (SnO) powders in high temperature. The SnO2NBs have their belt width for 30-90 nm, the belt thickness for 20-30 nm and the belt length for tens of micrometers. Based on the X-ray diffraction (XRD) measurements of the SnO2NBs, it can be confirmed that the nanobelts are the pure rutile tetragonal structures. From the high-resolved transmission electron microscopic images, the {111} lattice planes are clearly seen and the SnO2 nanobelt grows along the direction indexed from the corresponding ED pattern. The growth of the SnO2NBs can be attributed to the self-disproportion reaction of SnO bulk powders via the vapor-solid (VS) growth mechanism. In the Raman spectrum measurement, the rutile SnO2NBs have good signal to noise ratio and the peaks at 475.9, 635.5, and 777.2 cm-1 are resolved which are corresponding to the Eg, A1g, and B2g phonon modes, respectively. The last part in this thesis is the fabrication of the copper indium diselenide nanorods (CuInSe2NRs) which are commonly used in the solar cell technology. During the synthesis works, two ways are used for producing the CuInSe2 nanostructures, including the laser ablation/anodic aluminum oxide (AAO) membranes and the solvothermal methods. In the laser ablation/AAO membranes method, the AAO membranes have the highly uniform pore distribution and the CuInSe2 species can diffuse into the hollow channels to form the eutectic composites with the metal catalysts coated on the membranes and grow the one-dimensional CuInSe2 nanorods. The diameters of the CuInSe2NRs can reach 150-200 nm, however, the lengths of the can only extend ~2 micrometers. On the other hand, the CuInSe2NRs can also be synthesized by the solvothermal method, but the total reaction time is needed for at least 36 hours. Due to the long reaction time, the better aspect ratio and the product yield for the CuInSe2NRs can be acquired. The CuInSe2NRs fabricated by the solvothermal method have the diameter size of 50-100 nm and the lengths can extend to tens of micrometers. Moreover, from the high resolution image, the {112} lattice planes are found in the nanorods and can be indexed that the nanorods grow along the direction. The Raman spectrum for CuInSe2NRs is taken and can be found that the most intense A1 phonon mode located at 175.1 cm-1 is clearly verified. This is another evidence tells us that the nanorods are purely with the CuInSe2 structures for the chemical composition.

Raman spectra of graphene oxides (GOs) with different chemical compositions and synthesized by oxidation of distinct starting materials were analyzed to relate the spectral features to structural properties. The chemical compositions of different graphene oxides were determined by X-ray photoelectron spectroscopy (XPS), and nanoplatelets were characterized by zeta potential (ζ) and dynamic light scattering (DLS) measurements. The results indicated that the chemical composition, size, and superficial charge of the nanoplatelets depend on the starting material. We found five reported bands (D, D′, G, D″, and D*) in the first-order Raman spectrum and three bands (2D, D + D′, and 2D′) in the second-order Raman spectrum that successfully interpret the Raman spectra between 1000 and 3500 cm–1. Analysis of the bands allowed linear correlations to be found between the maximum positions of the 2D and D + D′ bands and between the relative intensities of the D and G bands (ID/IG) and the Csp2 percentage. Moreover, our results demonstrate that the relative intensities of the D′ and D bands are in excellent agreement with the theoretical correlations and allow the type of defects produced during oxidation, namely, vacancies or sp3 hybridation, to be related to the size of the graphene oxide sheets.

Carbon nanosheets are mechanically stable, free-standing two-dimensional materials with a thickness of ≈1 nm and well defined physical and chemical properties. They are made by radiation-induced cross-linking of aromatic self-assembled monolayers. Herein, a route is presented to the scalable fabrication of multilayer nanosheets with tunable electrical, optical, and chemical properties on insulating substrates. Stacks of up to five nanosheets with sizes of ≈1 cm(2) on oxidized silicon are studied. Their optical characteristics are investigated by visual inspection, optical microscopy, UV-vis reflection spectroscopy, and model calculations. Their chemical composition is studied by X-ray photoelectron spectroscopy. The multilayer samples are then annealed in an ultrahigh vacuum at various temperatures up to 1100 K. A subsequent investigation by Raman, X-ray photoelectron, and UV-vis reflection spectroscopy, as well as by electrical four-point probe measurements, demonstrates that the layered nanosheets transform into nanocrystalline graphene. This structural and chemical transformation is accompanied by changes in the optical properties and electrical conductivity and opens up a new path for the fabrication of ultrathin functional conductive coatings.

To support the translation of Raman spectroscopy into clinical applications, synthetic models are needed to accurately test, optimize and validate prototype fiber optic instrumentation. Synthetic models (also called tissue phantoms) are widely used for developing and testing optical instrumentation for diffuse reflectance, fluorescence, and Raman spectroscopies. While existing tissue phantoms accurately model tissue optical scattering and absorption, they do not typically model the anatomic shapes and chemical composition of tissue. Because Raman spectroscopy is sensitive to molecular composition, Raman tissue phantoms should also approximate the bulk tissue composition. We describe the fabrication and characterization of tissue phantoms for Raman tomography and spectroscopy. These phantoms have controlled chemical and optical properties, and also multilayer morphologies which approximate the appropriate anatomic shapes. Tissue phantoms were fabricated to support on-going Raman studies by simulating the human wrist and rat leg. Surface meshes (triangle patch models) were generated from computed tomography (CT) images of a human arm and rat leg. Rapid prototyping was used to print mold templates with complex geometric patterns. Plastic casting techniques used for movie special effects were adapted to fabricate molds from the rapid prototypes, and finally to cast multilayer gelatin tissue phantoms. The gelatin base was enriched with additives to model the approximate chemistry and optical properties of individual tissue layers. Additional studies were performed to determine optimal casting conditions, phantom stability, layer delamination and chemical diffusion between layers. Recovery of diffuse reflectance and Raman spectra in tissue phantoms varied with probe placement. These phantoms enable optimization of probe placement for human or rat studies. These multilayer tissue phantoms with complex geometries are shown to be stable, with minimal layer delamination and chemical diffusion.