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Herein we report the synthesis of covalently functionalized carbon nano-onions (CNOs) via a reductive approach using unprecedented alkali-metal CNO intercalation compounds. For the first time, an in situ Raman study of the controlled intercalation process with potassium has been carried out revealing a Fano resonance in highly doped CNOs. The intercalation was further confirmed by electron energy loss spectroscopy and X-ray diffraction. Moreover, the experimental results have been rationalized with DFT calculations. Covalently functionalized CNO derivatives were synthesized by using phenyl iodide and n-hexyl iodide as electrophiles in model nucleophilic substitution reactions. The functionalized CNOs were exhaustively characterized by statistical Raman spectroscopy, thermogravimetric analysis coupled with gas chromatography and mass spectrometry, dynamic light scattering, UV-vis, and ATR-FTIR spectroscopies. This work provides important insights into the understanding of the basic principles of reductive CNOs functionalization and will pave the way for the use of CNOs in a wide range of potential applications, such as energy storage, photovoltaics, or molecular electronics.

Owing to its singular and (to some extend) adaptable characteristics, titanium oxynitride (TixOyNz) represents an exceptional choice in the realm of new materials aiming at the development of practical devices. However, the effective use of TixOyNz in photovoltaic and (photo)catalysis applications, for example, relies on a refined production−properties balance. Accordingly, this paper reports on the physico-chemical properties of TixOyNz films as investigated by means of the Raman scattering and X-ray photoelectron spectroscopy (XPS) techniques – the former shedding light on the structural characteristics of the films, and the latter providing the state of oxidation of the film's constituents. The films were prepared by sputtering TiO2 and Ti targets in a plasma comprising different mixtures of Ar and N2. Because of the deposition method and conditions, the films exhibit Raman spectra that are consistent with a combination of TiO2 and TiN or, more properly, TixOyNz under the amorphous and (nano/micro-)crystalline structures. In fact, the experimental data indicate the presence of four TiO2- and two TiN-related phonon modes, whose relative scattering features scale with the oxygen and nitrogen contents of the films. A similar concentration dependence was verified with the percentage of Ti4+, Ti3+, and Ti2+ chemical states of oxidation. This mutual concentration dependence was explored thoroughly and the results clearly indicate the suitability of the Raman data to estimate the typical atom composition and distribution of the Ti-related chemical states of TixOyNz.

We report the dynamic behavior of surface-enhancement Raman scattering (SERS) spectra using rhodamine 6G dye (R6G, 10-8 mol L-1) adsorbed on gold nanorods (AuNRs). SERS spectra displayed a strong t...

The sorption of CO2 is often used to modify the macroscopic properties of liquids and solids. In the particular case of ionic liquids, different from molecular liquids, the sorption of CO2 may not induce volume expansions due to the strong Coulombic interactions between the ions of the fluid. However, a considerable viscosity decrease has been systematically observed. In order to understand the mechanisms of properties modifications in ionic fluids, herein we used Raman spectroscopy to probe the effect of CO2 on the structure of ionic liquids. It is shown that CO2 perturbs the electrostatic interactions between cations and anions, thus inducing a change in the polar domain of ionic liquids. It is observed that ionic liquids having bulkier ions are more prone to be perturbed by CO2 in comparison to ionic liquids having smaller ions. These results reveal new means of controlling the electrostatic forces between the ions and contributes to the mechanistic understanding of the modification of the macroscopic properties of ionic liquids by CO2 sorption.

Made available in DSpace on 2020-12-10T20:13:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-06 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Ba3MgNb2O9 is a double perovskite niobate with a trigonal structure with space group D-3d(3). Such a niobium-based compound has a great potential for applications as microwave dielectrics in the telecommunication industry. In this work, we report the lattice dynamics calculation results using a Short-Range Force Field Model and Density Functional Theory to represent the optical phonon modes at Gamma-point of the Brillouin zone. The classical method uses the nearest neighbor interactions through the interatomic force constants to describe the local order for Raman and infrared spectra. At the same time, density functional theory methods took into account two functionals (PBE and B3LYP) in order to provide the optical modes through second derivatives of the total energy. In both methods, theoretical optical modes are in good agreement with reported experimental data. The combination of both classical and quantum theoretical methods provided basis for a systematic discussion on the origin of the optical modes including the prediction of the dielectric tensor. We believe that this work presents useful information about the structural and vibrational characterization of Ba3MgNb2O9 perovskite and possible targeting for its application as microwave dielectrics for the communication technology. Univ Fed Amazonas, Inst Ciencias Exatas, Programa Posgrad Quim, Manaus, Amazonas, Brazil Sao Paulo State Univ, Modeling & Mol Simulat, Bauru, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, Sao Carlos, Brazil CSIC, Inst Ciencia Mat Madrid, Madrid, Spain Sao Paulo State Univ, Modeling & Mol Simulat, Bauru, SP, Brazil CNPq: 432242/2018-0 CAPES: 88881.171031/2018-01 FAPESP: 2013/07296-2 FAPESP: 2019/08928-9

O trabalho se propõe a avaliar o efeito do ruído de fluorescência (ruído de fóton ou shot noise) na classificação dos espectros de amostras de gasolinas padrão e adulteradas obtidas em postos de combustíveis na região de Santos/SP. Foram obtidas 15 amostras de diferentes postos de abastecimento, sendo 5 amostras padrão e 10 contendo algum tipo de adulteração (maior concentração de etanol ou presença de solvente orgânico). As técnicas de Lógica Paraconsistente Anotada com anotação de dois valores (LPA2v) e a análise de componente principal (PCA) com análise discriminante foram empregadas buscando-se verificar até que ponto a influência de diferentes níveis de ruído de fluorescência impactaria a classificação das amostras. Os resultados demonstraram que o ruído de fluorescência impacta a classificação das amostras, onde menores níveis de ruído (até 100 contagens) foram classificados corretamente pela LPA2v, enquanto que maiores níveis de ruído (200 contagens) promoveram melhor classificação para a técnica PCA.

In this article the doping of chromium in a lead metasilicate glass is explored using Raman, UV–Vis, and Cr K-edge XANES spectroscopy. Our results indicate that the Cr ions are predominantly present as CrO42− complexes, with a minor amounts of Cr(III). The solubility of Cr is limited to ∼1 mol % Cr2O3. This boundary was inferred from the intensity changes to the CrO42− stretching vibrations and confirmed by the inability to produce a homogeneous glass containing 2 mol % Cr2O3. The establishment of the solubility limit of Cr in lead glasses is important to design more effective glass compositions depending on the desired application. Finally, this low solubility indicates that Cr2O3 could be used as a potential nucleating agent for lead-silica based glass-ceramics.

The effect of the solvent on the electronic properties of the triarylmethane dye rosolic acid (RA) is investigated by means of UV-VIS and resonance Raman (RR) spectroscopies. The comparison of the solvatochromic behavior of both neutral and dianionic species of RA in acetonitrile, dimethylsulfoxide, and methanol illustrates the effect of polarity and hydrogen bonding on their electronic transitions. The resonance Raman analysis revealed two distinct chromophores in both neutral and dianionic species: i) one located at the central carbon atom, acting as an electron acceptor, and ii) the other involving the π-system of the donor groups. The observed resonance Raman excitation profiles are solvent dependent and could be interpreted as the effect of the solvent on the planarity of the aromatic rings in relation to the central carbon atom. In the case of neutral RA species, having C2 symmetry, specific hydrogen bonding interactions are responsible for inducing a symmetry increase. The opposite effect was observed for the dianionic species [RA]2-, having D3 propeller symmetry, where the interactions with the solvent induces a lowering of the symmetry.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais This work is based on the synthesis of CdSe e CdSe/CdSxSe1-x/CdS magic sized quantum dots, as well as CdSe e CdSe/CdSxSe1-x/CdS ultrasmall quantum dots in aqueous solutions. The physics properties of quantum dots were investigated using various experimental techniques and theoretical models. The modifications in the phonon confinement Gaussian model were done to perform a more realistic description of the shell and the alloy effects in quantum dots CdSe/CdSxSe1-x/CdS in the Raman Spectra. Two methods were developed, one synthesized a quantum dot magic size (MSPQs) and it was able to control the shell thickness CdS around the MSPQs depending on the synthesis temperature, and the second was obtained through the quantum dots ultrasmall, which the thickness of the shell CdS was monitored as a function of the stabilizer concentration. In addition, the results the MSPQs were functionalized with chemicals groups that may be bioconjugated. It was demonstrated that the MSPQs were not immunogenic and did not exhibit cytotoxic effects. Thus, the MSPQs were covalently bond to aspecificantibody for breast cancer targeting its use with a luminescent probe. Nesta pesquisa sintetizou-se pontos quânticos de CdSe e CdSe/CdSxSe1-x/CdS de tamanhos mágicos, além de CdSe e CdSe/CdSxSe1-x/CdS de tamanhos ultra pequenos em soluções aquosas. As propriedades físicas dos pontos quânticos foram investigadas através de várias técnicas experimentais e modelos teóricos. Foram realizadas modificações no modelo de confinamento de fônons Gaussiano a fim de realizar uma descrição mais real da casca e efeitos da liga em pontos quânticos de CdSe/CdSxSe1-x,/CdS nos espectros Raman. Duas metodologias foram desenvolvidas, uma que sintetiza pontos quânticos de tamanhos mágicos MSPQs, a qual permite controlar a espessura da casca de CdS ao redor dos MSPQs em função da temperatura de síntese, e a outra obtida através dos pontos quânticos de tamanhos ultra pequenos, em que a espessura da casca de CdS foi controlada em função da concentração de estabilizante. Além destes resultados, foram funcionalizados os MSPQs com grupamentos químicos para a bioconjugação. Demonstrou-se que os MSPQs apresentam baixa citotoxicidade e nenhuma resposta imunogênica. Dessa forma, foram acoplados covalentemente os MSPQs a um anticorpo específico de câncer de mama visando a sua utilização com uma sonda luminescente. Doutor em Física

Several calorimetric measurements have shown that 1-ethyl-3-methylimidazolium dicyanamide, [C2C1im][N(CN)2], is a glass-forming liquid, even though it is a low-viscous liquid at room temperature. Here we found slow crystallization during cooling of [C2C1im][N(CN)2] along Raman spectroscopy measurements. The low-frequency range of the Raman spectrum shows that the same crystalline phase is obtained at 210 K either by cooling or by reheating the glass (cold-crystallization). Another crystalline phase is formed at ca. 260 K just prior the melting at 270 K. X-ray diffraction and calorimetric measurements confirm that there are two crystalline phases of [C2C1im][N(CN)2]. The Raman spectra indicate that polymorphism is related to [C2C1im]+ with the ethyl chain on the plane of the imidazolium ring (the low-temperature crystal) or non-planar (the high-temperature crystal). The structural reason for the glass-forming ability of [C2C1im][N(CN)2], despite of the relatively simple molecular structures of the ions, was pursued by quantum chemistry calculations and molecular dynamics (MD) simulations. Density functional theory (DFT) calculations were performed for ionic pairs in order to draw free energy surfaces of the anion around the cation. The MD simulations using a polarizable model provided maps of occurrence of anions around cations. Both the quantum and classical calculations suggest that the delocalization of preferred positions of the anion around the cation, which adopts different conformations of the ethyl chain, is on the origin of the crystallization being hampered during cooling and the resulting glass-forming ability of [C2C1im][N(CN)2]., Author revised version of the paper published in J. Phys. Chem B in 2019. File contains 31 pages with 7 figures plus 8 pages of supporting information with 7 figures

In this article the Raman and Raman Optical Activity (ROA) spectra of a series of enantiomeric twisted anthracenes are presented. The evolution of their vibrational spectra is understood in the context of the variation of π-electron delocalization as a result of the twisting imparted by the belt structure and in terms of the modulation of the resonance Raman/ROA effects which are photonic properties also tuned by anthracene twisting. The Raman/ROA vibrational spectra are simulated by several theoretical approaches to account for their vibrational and electronic properties including the theoretical evaluation of resonance effects. We furthermore incorporate a vibrational and ROA activity dissection analysis as provided in the Pyvib2 program valid to establish correlations among vibrational modes of different molecules with different electronic structures and equivalent vibrational dynamics. This paper is one of the very first attempts to use ROA spectroscopy in π-conjugated molecules with twisted and helical morphologies that contrast with the well-known cases of ROA studies of chiral helicenes in which the impact of π-electron delocalization in the electronic/photonic/vibrational (Raman/ROA) spectra is negligible., In this article the Raman and Raman Optical Activity (ROA) spectra of a series of enantiomeric twisted anthracenes are presented.

Ceria nanoshapes exhibiting different amounts of {100}, {110} and {111} facets (cubes, rods, octahedra and polyhedra) were prepared, characterized, tested in the carbon soot oxidation reaction, and studied by operando near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and operando Raman spectroscopy up to 550 °C. The specific soot oxidation reaction rate (mgC·m-2·min-1) clearly indicated that the {110} and {100} crystallographic planes of ceria were more active than the {111} ones for the oxidation of carbon soot. As deduced from the Ce 3d and O 1s signals recorded using different photon energies, all ceria nanoshapes experienced progressive reduction upon increasing the temperature under Ar, which was accompanied by the formation of oxygen vacancies. Raman studies revealed that, at this stage, isolated graphene layers in carbon soot reacted with ceria lattice oxygen atoms following a Mars-Van Krevelen mechanism. After exposure to O2 at 550 °C, a broad signal in the O 1s region at 531.2–532.5 eV was ascribed to surface active oxygen species, such as peroxide (O22-) and superoxide (O2-) species, generated from the interaction of molecular O2 with oxygen vacancies, which proved to be highly reactive to oxidize the graphitic structures of carbon soot.

After more than 40 years, surface-enhanced Raman spectroscopy (SERS) stills attract much attention from chemists, not only because of the synthesis of plasmonic nanostructures but also due to the several simultaneous mechanisms which still remain unclear. One of the possibilities for a better understanding of the SERS mechanisms is the utilization of suitable inorganic complexes. The use of inorganic complexes makes it possible to observe the two main SERS mechanisms (electromagnetic and chemical) and to observe the intensification of Raman scattering due to the resonance Raman effect. In this publication, the observation of these mechanisms was possible utilizing an unpublished and very interesting complex with two oxo-triruthenium acetate clusters and an iron bis(terpyridine) in its structure (seven metals) and which interacted with bare gold nanoparticles and shell-isolated gold nanoparticles (SHIN), with a 1 nm silica shell. The utilization of SHIN allowed to quench the SERS chemical mechanism and led to a spectrum where iron-terpyridine peaks are absent and only the modes related to [Ru

Three different processes for the synthetization of exfoliated graphite intercalation compound have been tested in two different type of graphite, one in powder form and the other one as flakes. Each graphite was oxidized applying the same experimental conditions (sonification, neutralization, filtering and drying) but using three different auxiliary oxidizers (H2O2, HNO3 and KClO3) previously mixed with H2SO4. The resulting synthesized samples were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The Raman spectra analysis of the oxidized samples correspond to that of a graphene of few layers. Stronger delamination and exfoliation were observed in the samples of graphite, originally in powder form, treated with H2SO4/HNO3. RESUMO Três processos diferentes para a sintetização de composto de grafite intercalado esfoliado foram testados em dois tipos de grafites diferentes, um em forma de pó e o outro na forma de flocos. Cada grafite foi oxidado nas mesmas condições experimentais (de sonificação, neutralização, filtragem e secagem), porém utilizando três agentes oxidantes diferentes (H2O2, HNO3 e KClO3), previamente misturados com H2SO4. As amostras sintetizadas resultantes foram caracterizadas por difração de raios X, espectroscopia Raman e microscopia eletrônica de varredura. A análise dos espectros Raman das amostras oxidadas mostrou correspondência com a do grafeno de poucas camadas. Delaminação e exfoliação em maior proporção foram observadas nas amostras do grafite original em pó, tratado com H2SO4/HNO3.

Detection of a single molecule is a highly fluctuating event in surface-enhanced Raman scattering (SERS) measurements. Explaining these dynamic blinking events remains a challenge. To investigate this fluctuating behavior, we manufactured Au nanocylinder arrays. A monolayer of nicotinamide adenine dinucleotide (NAD) on the nanocylinder array exhibited intense and fluctuating Raman lines. Persistent Raman lines were not observed over time. These fluctuations were discussed within the dynamic back-action parametric interaction between the plasmon mode and vibrational modes. The results suggest that the highly efficient SERS structure promotes the formation and destruction of protuberances smaller than 2 nm at random on the nanocylinder surface.

Fe-doped indium tin oxide (ITO) is an exciting material because it combines the host matrix's good electrical conductivity with the magnetic properties coming from the most earth-abundant transition metal, Fe. In this regard, a single-pot synthesis route based on a polymeric precursor method has been used to produce high-quality undoped and iron-doped ITO with iron content up to 13.0 mol%. The crystal formation in the bixbyite-type structure of all samples is confirmed by X-ray diffraction data analysis. A monotonous decrease of the lattice parameters with the increase of the Fe content is determined, which is consistent with of Fe ions with an oxidation state of 3+ in agreement with the ionic radii difference between In3+ and Fe3+. Raman spectroscopy confirms the bixbyite structure formation and provides evidence of a high surface disorder. 119Sn Mossbauer spectroscopy reveals the formation of only Sn4+ ions. Meanwhile, 57Co Mossbauer spectroscopy suggests the presence of Fe3+ ions in a paramagnetic state. DC magnetization characterization of the Fe-doped ITO nanoparticles confirms the compound's paramagnetic character. The sheet resistance (R/□) measurements provide a lower value for the undoped ITO sample (~0.26 Ω/sq) than the one of commercial bulk material. It has been determined that the sheet resistance increases with the Fe content, suggesting the decrease of the conduction electrons density as the iron content is increased.

Time resolved Raman spectroelectrochemistry is a powerful technique to prepare useful Surface Enhanced Raman Scattering (SERS) substrates suitable for quantitative analysis. Moreover, following the evolution of the Raman signal with the applied potential the selection of the best conditions for the analysis is quite simple. In this work, gold SERS substrates are prepared on screen-printed electrodes for the determination of nicotinamide, vitamin B3, in a multivitamin complex. The formation of the substrate has been monitored using UV/Vis absorption spectroelectrochemistry and scanning electron microscopy, which confirmed the generation of gold nanoparticles on the electrode surface. This new method has demonstrated to be suitable for the direct quantification of simple test samples using small sample volumes (50 μL). However, it failed when a complex sample, containing several interfering species, was analysed. A high interference on the preparation of the SERS substrate is observed during the analysis of a multivitamin complex. Despite that, nicotinamide was selectively determined in a multivitamin complex using the method of the standard addition, obtaining remarkable figures of merit (R2 = 0.99, %RSD < 9%)., Ministerio de Economía, y Competitividad (Grant CTQ2017-83935-R-AEI/FEDERUE), Junta de Castilla y León (Grant BU297P18) and Ministerio de Ciencia, Innovación y Universidades (Grant RED2018-102412-T). J.V.P-R. thanks Junta de Castilla y León for his postdoctoral fellowship (Grant BU033-U16)

Electrochemical Surface Oxidation Enhanced Raman Scattering (EC-SOERS) is an interesting and promising phenomenon capable of amplifying the Raman signal in a similar way to Surface Enhanced Raman Scattering (SERS), but EC-SOERS takes place during the oxidation of a silver substrate. This phenomenon was originally described for specific electrolytic conditions in which a small amount of chloride in acidic medium was mandatory to obtain a substantial enhancement. Herein, we demonstrate that EC-SOERS can be also observed in presence of KBr, showing a potential-dependent behavior. Moreover, in this work a novel approach to reach chemical selectivity during time resolved Raman spectroelectrochemistry (TR-Raman-SEC) experiments is proposed. This new approach is based on the effect of the electrolytic medium on the structures that are formed on the electrode surface. SEM studies were carried out to study the origin of this selectivity. Although SEM images reveal clear differences between the structures of silver halides formed on the electrode surface during the oxidation of the substrate, the absence of EC-SOERS effect at open circuit potential hinders the identification of the actual structures responsible for the phenomenon., Ministerio de Economía y Competitividad (Grants CTQ2017-83935-R-AEI/FEDERUE), Junta de Castilla y León (BU297P18) and Ministerio de Ciencia, Innovación y Universidades (RED2018-102412-T)

Heavy minerals are typically rare but important components of siliciclastic sediments and rocks. Their abundance, proportions, and variability carry valuable information on source rocks, climatic, environmental and transport conditions between source to sink, and diagenetic processes. They are important for practical purposes such as prospecting for mineral resources or the correlation and interpretation of geologic reservoirs. Despite the extensive use of heavy mineral analysis in sedimentary petrography and quite diverse methods for quantifying heavy mineral assemblages, there has never been a systematic comparison of results obtained by different methods and/or operators. This study provides the first interlaboratory test of heavy mineral analysis. Two synthetic heavy mineral samples were prepared with considerably contrasting compositions intended to resemble natural samples. The contributors were requested to provide (i) metadata describing methods, measurement conditions and experience of the operators and (ii) results tables with mineral species and grain counts. One hundred thirty analyses of the two samples were performed by 67 contributors, encompassing both classical microscopic analyses and data obtained by emerging automated techniques based on electron-beam chemical analysis or Raman spectroscopy. Because relatively low numbers of mineral counts (N) are typical for optical analyses while automated techniques allow for high N, the results vary considerably with respect to the Poisson uncertainty of the counting statistics. Therefore, standard methods used in evaluation of round robin tests are not feasible. In our case the 'true' compositions of the test samples are not known. Three methods have been applied to determine possible reference values: (i) the initially measured weight percentages, (ii) calculation of grain percentages using estimates of grain volumes and densities, and (iii) the best-match average calculated from the most reliable analyses following multiple, pragmatic and robust criteria. The range of these three values is taken as best approximation of the 'true' composition. The reported grain percentages were evaluated according to (i) their overall scatter relative to the most likely composition, (ii) the number of identified components that were part of the test samples, (iii) the total amount of mistakenly identified mineral grains that were actually not added to the samples, and (iv) the number of major components, which match the reference values with 95% confidence. Results indicate that the overall comparability of the analyses is reasonable. However, there are several issues with respect to methods and/or operators. Optical methods yield the poorest results with respect to the scatter of the data. This, however, is not considered inherent to the method as demonstrated by a significant number of optical analyses fulfilling the criteria for the best-match average. Training of the operators is thus considered paramount for optical analyses. Electron-beam methods yield satisfactory results, but problems in the identification of polymorphs and the discrimination of chain silicates are evident. Labs refining their electron-beam results by optical analysis practically tackle this issue. Raman methods yield the best results as indicated by the highest number of major components correctly quantified with 95% confidence and the fact that all laboratories and operators fulfil the criteria for the best-match average. However, a number of problems must be solved before the full potential of the automated high-throughput techniques in heavy mineral analysis can be achieved. info:eu-repo/semantics/publishedVersion

Nanometric probes based on surface-enhanced Raman scattering (SERS) are promising candidates for all-optical environmental, biological and technological sensing applications with intrinsic quantitative molecular specificity. However, the effectiveness of SERS probes depends on a delicate trade-off between particle size, stability and brightness that has so far hindered their wide application in SERS imaging methodologies. In this Article, we introduce holographic Raman microscopy, which allows single-shot three-dimensional single-particle localization. We validate our approach by simultaneously performing Fourier transform Raman spectroscopy of individual SERS nanoparticles and Raman holography, using shearing interferometry to extract both the phase and the amplitude of wide-field Raman images and ultimately localize and track single SERS nanoparticles inside living cells in three dimensions. Our results represent a step towards multiplexed single-shot three-dimensional concentration mapping in many different scenarios, including live cell and tissue interrogation and complex anti-counterfeiting applications.

Although the mainly intermolecular forces involved in the self-assembly of oligoaniline molecules have been consistently discussed (hydrogen bonds and π- π stacking interactions) the correlation between the driving forces and the large variations of morphology that can be obtained is still open in discussion, mostly because a detailed chemical characterization of such products is usually difficult to achieve. In this work, 3-D fluorescence spectroscopy is presented as a powerful technique in the identification and differentiation of phenazinic segments, with Raman spectroscopy being crucial for identification of 1,4-Michael-type segments and the verification of non-hydrolyzed imine groups in oligoaniline microspheres produced under pH 4.5 buffered conditions and employing different reagent concentrations. The results suggested that the self-assembly must occur by hydrogen bonds related to the non-hydrolyzed iminic groups and π-π stacking interactions between non-substituted phenazinic segments. Moreover, obtaining specific morphologies (flower-like structures, porous microspheres and hollow microspheres) showed dependence with the increase of the relative reagent concentrations.

Light can be used to address electrochemical reactions on a monolithic semiconducting electrode with spatial and temporal resolution. Herein, such principle was used for the electrodeposition of Au, Ag and Cu nanoparticles on a unique silicon-based electrode. The parallel nature of the process granted manufacturing speed and platforms were applied to discriminate molecules via multi-wavelength and multivariate Raman analysis.

Excess proton structures in water remain unclear. The motion and nature of excess protons in water were probed using a supported water bridge structure in electric field (E) with an intensity of similar to 10(6) Vim. The experimental setup generated protons that exhibit a long lifetime. The effect of excess protons in water induced a similar to 3% variation in the pH for a 300 V overvoltage at the cathode. The current versus voltage curves show a current space charge-limited operation. By measuring the space-charge distribution in both the cathode and anode and by adjusting the Mott-Gurney law to the measured excess hydrated proton current and the voltage in drope cationic space charge region, the protonic mobility was determined to be similar to 200 x 10(-8) m(2)/(V.s) (E approximate to 4 x 10(6) V/m). This measured mobility, which is typically five times larger than the reported mobility for protons in water, is in agreement with the mechanism outlined by Grotthuss in 1805. The measured mid-Raman spectrum covering 1000-3800 cm(-1) range indicates the species character. The hydrated excess proton spectral response through the mid-Raman at 1760 and 3200 cm(-1) was attributed to the Zundel complex and the region at similar to 2000 to similar to 2600 cm(-1) response is attributed to the Eigen complex, indicating a core structure simultaneously with a Eigen-like and Zundel-like character, suggesting a rapid fluctuation between these two structures or a new specie Aberto

CoOOH/Ni(OH)2 and Ni(OH)2/CoOOH bilayer films were obtained through electrochemical deposition of Ni(OH)2 and Co(OH)2 single layers onto steel plate substrate, with subsequent electrochemical oxidation of Co(OH)2 to form CoOOH. The films were structurally characterized using X-ray diffraction and Raman spectroscopy techniques. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy techniques were used to perform the electrochemical characterization of the prepared bilayers. It was verified that during the electrochemical oxidation, CoOOH formation occurs without Ni(OH)2 oxidation. Ni(OH)2 films deposited on CoOOH (CoOOH/Ni(OH)2) showed a superior electrochemical performance, with 324.27 mA h g−1 and 96.82% at 1.0 mA cm−2 for the specific capacity and capacity retention respectively. It was also determined that the relaxation time constant under this condition is 17.05 s. These results suggested that the CoOOH/Ni(OH)2 bilayer films might be potential candidates for application as electrode in energy storage devices.

The different solvation states of SO2 in 1-butyl-3-methylimidazolium thiocyanate ionic liquid were probed by the detailed analysis of the SO2 symmetric stretching mode, νs(SO2). The band position and linewidth were monitored in function of gas molar fraction, excitation wavelength, and temperature. As expected, the decreasing of the SO2 molar fraction, XSO2, from approximately 0.8 to 0.2, leads to a gradual downshift of the νs(SO2) band, attributed to a more effective charge transfer interaction from thiocyanate anion to SO2. Interestingly, at high gas concentrations (XSO2 = 0.8), a gradual downshift of the νs(SO2) band was noticed as the Raman excitation energy increases, an unexpected behavior because the change in the excitation wavelength in Raman spectroscopy should affect only the band intensities. Such νs(SO2) Raman dispersion can be understood as a consequence of the distinct charge transfer electronic transition energies associated to different SO2 solvation states, whose relative band intensities are modulated by resonance Raman conditions. Moreover, the lowering from room temperature to 100 K showed an increasing in the Raman dispersion effect. The temperature dependence was attributed to the strengthening of the cation–anion interaction, responsible for the increasing of SO2 solvation states distribution. The vibrational spectroscopic data regarding the SO2 solvation inhomogeneity in ionic liquids are showed for the first time, and it may contribute in the understanding of why such liquids are promising solvents for SO2 capture.

Made available in DSpace on 2018-12-11T17:04:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01 Pr3+-doped CaTiO3perovskite is a promising phosphor compound with the possibility of use in several technological applications. In this paper, we report the substitution of Ca2+ions with La3+ions in order to promote Ca vacancies to further enhance photoluminescence (PL). CaTiO3:Pr,La samples were prepared by the polymeric precursor method and their short- and long-range structure and photoluminescent properties were investigated in this paper. PL measurements show a narrow emission centered at 612 nm typical of the1D2–3H4transition of Pr3+ions. As the La content increases, the intensity of this peak is increased. This enhancement of PL curves for CaTiO3:Pr,La samples is associated with disorder in the CaTiO3lattice caused by the La incorporation. This disorder as a function of the La content is shown by both X-ray absorption near edge structure (XANES) spectra at the Ti K-edge and Raman spectroscopy measurements. CaTiO3:Pr,La samples do not present PL with long term afterglow. Instituto de Geociências e Ciências Exatas UNESP – Univ Estadual Paulista Departamento de Física Instituto de Física de São Carlos Universidade de São Paulo Instituto de Geociências e Ciências Exatas UNESP – Univ Estadual Paulista Departamento de Física

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico Nesse trabalho temos como objetivo estudar blendas poliméricas, capazes de serem aplicadas em camadas ativas para a Célula Eletroquímica Emissora de Luz (LEC). Os materiais escolhidos para a formação da camada ativa foram os polímeros conjugados: o poli [2-metóxi-5-(2-etilhexiloxi)-p-fenilenovinileno)]- MEH-PPV e o Poli [2-(2',5'-bis(2"-etilhexiloxi)fenil)-1,4-fenilenovinileno]- BEHP-PPV e dois conjuntos de eletrólitos poliméricos: o polióxido de etileno bloco polietileno (PE-b-POE) complexado com o sal inorgânico, o perclorato de lítio (LiClO4)† e o triflato de lítio (LiCF3SO3). Para confeccionar as blendas, foram preparadas soluções dos eletrólitos em acetonitrila e dos polímeros conjugados em THF. As blendas foram preparadas nas concentrações de 6,5%; 7,5% e 8,5% de sal. Essa faixa de concentração optimiza às propriedades estruturais e elétricas do EPs e com isso podemos sugerir um dispositivo eletro-óptico. As análises dos resultados mostram que as propriedades ópticas de absorção e emissão das blendas com o BEHP-PPV as modificações mais relevantes com a presença do EP do que no sistema com o MEH-PPV. Já na análise vibracional notamos que somente nas blendas com o BEHP-PPV foi possível identificar os modos vibracionais referentes aos sais dissociados nos EPs. Nas medidas de superfície nota-se uma forte agregação em ambos os PC, de forma que o solvente interage fracamente com essa classe de polímeros, nas blendas confirmamos com a ajuda do AFM a separação de fase. Por fim, das medidas de I x V observamos que a blenda BEHP-PPV com 8,5% de sal LiClO4, possui maior corrente. Efeito de resistência negativa também foi observado para as blendas, que poder ser atribudo por modificações nas propriedades na estrutura de banda do PC. In this work polymer blends were studied, which were capable of being the active layer in Light Emitting Cell (L.E.C.). The materials chosen for the formation of the active layer were the poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]- MEH-PPV and the Poli(2,5-bis(2'-ethyl-hexyl)-1,4-phenylenevinylene]- BEHP-PPV and two systems polymer electrolytes, poly (ethylene oxide) block polyethylene (PE-b-POE), complexed with inorganic salts, Lithium Perchlorate (LiClO4) † and Lithium Triflate (LiCF3SO3). To obtain the blends, the solutions of polymer electrolytes were prepared in acetonitrile and the conjugated polymer were prepared in THF. The salt concentration was varied in the range of 6,5%, 7,5% and 8,5%. The results show that the optical properties, absorption and emission, of the BEHP-PPV blends are more modified with the presence of the electrolytes then the MEH-PPV systems. However, in the MEH- PPV blends the vibrational modes of salt dissociated weren’t observed, suggesting high aggregation proven surface measurements. The AFM images help us confirm the phase separation of the blends. IxV curves reveal that BEHP-PPV blend of 8,5% with Lithium Perchlorate optimized the current and negative resistance effects are also observed in this LEC. Dissertação (Mestrado)

Resumen El avance tecnológico de las últimas décadas ha propiciado el desarrollo de nuevas metodologías para la caracterización de materiales de origen biológico. La espectroscopía Raman es utilizada principalmente en la caracterización de sustancias orgánicas e inorgánicas puras, sin embargo, recientemente se está utilizando para el estudio de organismos y estructuras moleculares de interés biológico. La principal dificultad en el análisis de estos materiales mediante la espectroscopía Raman es la fluorescencia que presentan las muestras al ser iluminadas con el haz de luz láser, pero mediante la técnica SERS (Surface Enhanced Raman Spectroscopy), es posible aumentar la señal Raman y reducir la interferencia de la fluorescencia. Para la aplicación de las técnicas SERS se pueden utilizar nanopartículas metálicas, principalmente oro y plata, de una adecuada distribución de tamaños. En este trabajo se presentan los resultados de la aplicación de técnica SERS a la caracterización espectroscópica del ADN de dos organismos diferentes, de un ser humano y de una bacteria del género Rickettsia, utilizando nanopartículas de oro y plata para la aplicación de la metodología. Abstract The technological advances of the last decades have contributed to the development of new methodologies for the characterization of biological samples. Raman Spectroscopy has been used for the characterization of pure inorganic and organic compounds, but recently, it is being used to study molecular structures of biological importance. Fluorescence is usually present in Raman spectroscopy, shielding Raman signals, but using the SERS (Surface Enhanced Raman Spectroscopy) technique, it is possible to locally increase the Raman signal and to reduce the importance of the fluorescence effects on the samples. The SERS effect could be achieved by adding metallic nanoparticles, of a specific size distribution, to the sample. Usually gold and silver nanoparticles are used for SERS. In this research, DNA of human and Rickettsia bacteria were characterized by the SERS technique, with both silver and gold nanoparticles.

The photodegradation of diclofenac from aqueous medium under UV-A light condition has been essayed using co-doped with manganese and silver TiO2 photocatalysts. X-ray diffraction, Raman spectroscopy, Scanning electron microscopy, Transmission electron microscopy, High resolution transmission electron microscopy, Energy dispersive X-ray, N2 adsorption-desorption measurements at 77 K, UV–Visible diffuse reflectance, X-ray photoelectron spectroscopy and photoluminescence analyses were used to characterize the materials. A high surface specific area of 165 m2/g, low band gap energy (2.7 eV) and effective charge separation were obtained for the 0.5%Ag-0.6%Mn/TiO2 photocatalyst. The results of the photocatalytic experiments showed that co-doping improved the photocatalytic activity of TiO2. In particular, TiO2 co-doped with 0.6 mol% Mn and 0.5 mol% Ag exhibited the maximum diclofenac removal (86%) after 4 h under UV-A light irradiation. The photodegradation rates followed a first order kinetics according to the Langmuir-Hinshelwood model, being the highest apparent rate of 0.0064 min−1. The photocatalytic performance appears as related to the specific surface area, the low optical band gap energy, the creation of surface oxygen vacancies and the efficient separation of photogenerated electron-hole pairs.

Fluoride phosphate/fluorophosphate (FP) glasses form an intriguing material's basis for diverse applications in optics, photonics and energy storage. The optimization of the materials' properties with regard to the application envisioned demands an understanding of the key concepts describing their local structures on different distance regimes. Because of the inevitable losses of fluoride during melting or annealing, the synthesis and elemental analytical characterization present important and critical challenges. In this contribution we summarize the current state of the literature regarding the structural characterization of these glasses. Foci are the detailed analysis of vibrational spectra with special emphasis on Raman scattering results and multinuclear solid-state NMR spectroscopy. While vibrational spectra give important information about the local environments (short range order) advanced multi-dimensional and multi-resonance methodology can extend the informational content of solid-state NMR into the sub-nanometer distance range, including second and third coordination spheres. Exemplary results will be presented for (a) aluminum fluoride based simple model systems, (b) fluoride phosphate glasses containing heavy transition metals or post-transition metal elements, and (c) rare-earth doped fluoride phosphate glasses for laser applications. The latter application field documents the utility of correlated spectroscopic studies using both methods in understanding the structural foundations of photophysical properties. Keywords: Fluoride phosphate and fluoro-phosphate glasses, Analysis, NMR spectroscopy, ESR spectroscopy, Raman and IR, Spectroscopy, Structure

This manuscript reports the phenomenology of blood-material interface assessed by contact angle measurements and Raman spectroscopy. In particular, chemistry, topology and superhydrophobic effects on the contact line of blood droplets were investigated by using distinct substrates: Silicon, Ti13Nb13Zr and bioinspired-like PTFE, respectively. The surfaces were functionalized through different process aiming to study the specific effects. The chemical fingerprints of the biomolecules at the blood stain rings appear to be influenced by the contact line, which in turn depends on the kind of chemical treatment. A five-fold increase in roughness parameters by a metallic thinning process leads to a hydrophilic-hydrophobic transition in the metallic substrate followed by an increase in the bloodphobicity. In order to assess the extreme in the super blood-phobic state observed in a bio-inspired surface, a simple 3D model based on thermodynamic standpoint and solid-liquid fraction has been proposed to predict optimized parameters for the substrate. Collectively, the results can offer new insights towards the objective of rational substrate design that can improve next generation blood-devices and antithrombogenic metallic implants.

Materials science has observed a continuous increase in the use of metal nanoparticles in a wide range of studies, from fundamental physics to technological applications such as photocatalysis and optical communication devices. This broad scope has the same fundamental origin, the localized surface plasmons, whose excitation leads to strong light confinement, especially in the vicinity of closely spaced nanoparticles, the hot spots. The field amplification may be used to amplify the Raman scattering of adsorbed molecules, which is known as surface-enhanced Raman scattering (SERS). A crucial and limiting characteristic of SERS hot spots is their very localized nature, that influences the SERS intensity reproducibility as well as the probabilities of observation of single-molecule SERS signals. In this paper we discuss the correlation between SERS performance and gold nanorod cluster structures using transmission electron microscopy, SERS spectra and numerical simulations. The experimental data showed interesting behavior for the combination of end-to-end and side-by-side interactions, revealing the possibility of creating strong hot spots with a more extended spatial distribution. The results give insights into the development of high-performance SERS substrates.

The chemical bulk reductive covalent functionalization of thin-layer black phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkyl halides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations; the products showed higher functionalization degrees than those obtained by neutral routes., A.H. and G.A. acknowledge the European Research Council (ERC Advanced Grant 742145 B‐PhosphoChem to A.H., and ERC Starting Grant 2D‐PnictoChem 804110 to G.A.) for support. The research leading to these results was partially funded by the European Union Seventh Framework Programme under grant agreement No. 604391 Graphene Flagship. G.A. has received financial support through the Postdoctoral Junior Leader Fellowship Programme from “la Caixa” Banking Foundation (LCF/BQ/PI18/11630018). G.A. thanks the Deutsche Forschungsgemeinschaft (DFG; FLAG‐ERA AB694/2‐1), the Generalitat Valenciana (SEJI/2018/034 grant), and the FAU (Emerging Talents Initiative grant #WS16‐17_Nat_04) for support. A.H. and A.G. thank the SFB 953 “Synthetic Carbon Allotropes” funded by the DFG for support and the Cluster of Excellence “Engineering of Advanced Materials”. A.G. is grateful for funding from the Free State of Bavaria (Research Network “Solar Technologies go Hybrid”). A.M. thanks the Alexander von Humboldt (AvH) Foundation for a postdoctoral fellowship. This work was supported by the MINECO (Spain) through the Excellence Unit María de Maeztu (MDM‐2015‐0538) and the Project CTQ2017‐86735‐P.

6 Figuras. 3 Tablas., The effect of doping on the electronic properties in bulk single-walled carbon nanotube (SWCNT) samples is studied for the first time using a new in situ Raman spectroelectrochemical method, and further verified by DFT calculations and photoresponse. We use p-/n-doped SWCNTs prepared by diazonium reactions as a versatile chemical strategy to control the SWCNT behavior. The measured and calculated data testify an acceptor effect of 4-aminobenzenesulfonic acid (p-doping), and a donor effect (n-doping) in the case of benzyl alcohol. In addition, pristine and covalently functionalized SWCNTs were used for the preparation of photoactive film electrodes. The photocathodic current in the photoelectrochemical cell is consistently modulated by the doping group. These results validate the in situ Raman spectroelectrochemistry as a unique tool box for predicting the electronic properties of functionalized SWCNTs in the form of thin films and their operational functionality in thin film devices for future optoelectronic applications., The authors acknowledge financial support from the European Union FP7 RADDEL programme (ITN Marie Curie Actions PEOPLE-2011-290023) and the MEYS Inter Excellence Project no. LTC18039 and H2020-MSCA RISE Agreement no. 734834 (INFUSION). This work at the Instituto de Carboquímica has been funded by the MINECO and the European Regional Development Fund (ENE 2016-79282-C5-1-R), the Government of Aragon (T03-17R), and the European Commission (H2020-MSCA-ITN-2014-ETN 642742 ‘Enabling Excellence’). The work in Mons is supported by the European Union H2020 iSwitch programme (H2020-MSCA-ITN-2014-ETN 642196). Computational resources in Mons were provided by the Consortium des Équipements de Calcul Intensif (CÉCI) funded by the Belgian National Fund for Scientific Research (F.R.S.-FNRS) under Grant 2.5020.11. J. C. is an FNRS research director. The authors acknowledge the assistance provided by the Research Infrastructures NanoEnviCz (Project No. LM2015073) supported by the Ministry of Education, Youth and Sports of the Czech Republic and the project Pro-NanoEnviCz (Reg. no. CZ.02.1.01/0.0/0.0/16_013/0001821) supported by the Ministry of Education, Youth and Sports of the Czech Republic and the European Union – European Structural and Investments Funds in the frame of Operational Programme Research Development and Education. J. M. G.-D. is grateful to Spanish Ministry of Science, Innovation and Universities for his ‘Juan de la Cierva – Incorporación’ research grant. A. S. is grateful to Dr Sara Costa and Dr Johan Ek Weis for fruitful discussions and helpful comments., We also acknowledge institutional support from the Unit of Information Resources for Research at the "Consejo Superior de Investigaciones Científicas" (CSIC) for the article-processing charges contribution

Producción Científica, Interest in the integration of graphene and semiconductor nanowires (NWs) increased dramatically during the last two decades along with the overwhelming development of graphene technology. The possibility of combining the countless properties of graphene with the singular optical behavior of semiconductor NWs leads the way to the design of unique photonic nanodevices. In this work, the optical response of Si/SiGe axially heterostructured NWs deposited over a graphene monolayer is investigated. The results demonstrate the enhancement of the graphene Raman signal under the influence of the NW. Moreover, the presence of an axial heterojunction in the NW is shown to locally hinder this enhancement through the full confinement of the incident electromagnetic field inside the NW body around the heterojunction. This complex interaction could be the basis for near-field probes for molecules or 2D materials, and optoelectronic devices including graphene/NW interfaces., Junta de Castilla y León (project VA283P18), Gobierno de España (grants ENE 2014-56069-C4-4-R and FPU14/00916)

One of the current issues in the Mars regolith investigation is the performance evaluation of the instruments that are to be sent on the next missions, and commercial portable Raman instruments have been used in experiments aiming to simulate the capabilities of the Mars mission prototypes. In this study, several types of iron oxides with low crystallinity, some of them containing other metals as impurities, were synthetized and characterized using a bench-top research grade Raman microscope and a portable instrument, both with excitation at 785 nm. The obtained results clearly indicated that luminescence is an issue in such type of samples, even with excitation at 785 nm, and this is particularly more important with the portable instrument which lacks confocality; furthermore, the higher laser power density, necessary in this kind of instrument, is likely to cause phase transitions and de-hydration. A comparison with excitation at 514.5 nm has shown that, as expected, these effects are more marked at higher laser frequency. Laser excitation and power density are, therefore, two important issues to overcome for a successful remote characterization of the Mars regolith.

The role of thermally grown α-Fe2O3 on the nucleation of α-Al2O3 during oxidation of binary Fe–Al alloys with 15 and 26 at.%Al at 700 °C was investigated. Surface morphology of the oxide scales indicated direct nucleation of α-Al2O3 preferentially instead of conversion from metastable Al2O3 polymorphs. Oxide scale development over time was also monitored by use of synchrotron X-ray diffraction and Raman spectroscopy. The results showed that the α-Fe2O3 crystal lattice decreases in volume as oxidation progresses, which was found to be consistent with an Al3+ enrichment of α-Fe2O3 as confirmed by the change in relative intensity of α-Fe2O3 Raman peaks.

A gray cast iron disc, which had been submitted to a heavy duty automotive brake test, was examined with energy filtered transmission electron microscopy. A graphite flake in a convenient angular position showed the shear interaction of graphite layers with the iron matrix in nano-scale resolution. Atomic layers of graphite were wedged into the ferritic bulk, allowing the entrance of oxygen and the subsequent formation of magnetite. The exfoliated few-layer graphene batches deformed heavily when forced into the matrix. When Raman spectra from the disc surface, which show distinctive carbonaceous bands, were compared with Raman spectra from graphite subjected to deformation in a shaker mill with different milling times, it could be seen that the shear stress on the brake surface was much more effective to induce disorder than the milling, where compressive and impact forces had been additionally exerted on the sample. During shear load the high anisotropy of elastic modulus in the graphite crystalline structure and the low adhesion between graphite basal planes allowed the exfoliation of wrinkled few-layer grapheme batches, causing the formation of more defect related Raman bands than the mechanical stress during high-energy milling.

La preparación de compuestos híbridos de biomoléculas y estructuras de tamaño nanométrico es de especial interés para el desarrollo de aplicaciones en el campo de los biosensores y la entrega de fármacos, entre otros. En este estudio se llevó a cabo la preparación de un conjugado formado por grafeno y ácido fólico cuya caracterización se hizo mediante espectroscopia Raman y el método computacional de la teoría del funcional de la densidad (DFT). El conjugado no covalente se obtuvo mediante un método rápido y sencillo de tipo “one pot”. La espectroscopia Raman permitió evidenciar la funcionalización del grafeno con el ácido fólico mediante el análisis de las relaciones en la intensidad de las señales Raman correspondiente a las bandas G y D. El método DFT mostró que la unión de grafeno y ácido fólico ocurre por la acción de fuerzas de enlace de tipo no covalente, como las interacciones de tipo π-π, y de puentes de hidrógeno. La obtención de este tipo de conjugados permitiría explorar su aplicación en el diseño de biosensores que detecten células cancerígenas con sobreexpresión de receptores de folato, con el fin de facilitar un diagnóstico eficaz y oportuno del cáncer. Hybrid compounds formed by biomolecules and nanometric structures are attracting interest for the development of applications in the fields of biosensors and drug delivery. In this study we prepared a grapheme-folic acid conjugate which we characterized by Raman spectroscopy and the density functional theory (DFT) computational method. The non-covalent conjugate was performed through a simple and fast one-pot method. The analysis of ratio intensity of D and G bands in the Raman spectroscopy evidenced graphene functionalization. The DFT method showed that the bond between graphene and folic acid occurs by non-covalent π-π and hydrogen bond interactions. Graphene and folic acid conjugates will allow the design of biosensors for the detection of cancer cells overexpressing folate receptors using analytic devices for a faster, more effective and timely diagnosis of cancer.

Equation of state according to the Carnahan-Starling-van der Waals model has been proposed for ionic liquids based on the anions tetrafluoborate, [BF4]−, hexafluorophosphate, [PF6]−, and bis(trifluoromethanesufonyl)imide, [NTf2]−, from available volumetric data within the MPa range of pressure. Then, the equation of state is used to estimate density in the GPa range of pressure. The hard sphere part of the equation considered a binary mixture of cation and anion spheres whose diameters exhibit a satisfactory degree of transferability among different systems with a common ion. It is shown that pressure induced vibrational frequency shift, ∆ν, of the characteristic Raman band of the stretching mode of [BF4]−, [PF6]−, and [NTf2]− collapses into a master curve when ∆ν is plotted as a function of reduced density for each group of ionic liquids. Thus, Raman spectroscopy provides a validation test of the high-pressure extrapolation of the equation of state for ionic liquids.

We report the effect of gold nanoparticles (AuNPs) and unwanted sodium citrate residues (UnR) left after deposition of AuNPs by drop-casting method on the Raman spectra of graphene sheets (GS). The AuNPs solution was deposited on three different substrates: 5.0 wt% Yb3+-doped (Q5) phosphate glass, silica glass (S1), and Si/SiO2-300 nm (S2) substrates. For Q5 substrate, a slight increase in intensity of the G peak was observed, mostly for thinner layers, which can be attributed to a weak SERS effect shielded by UnR. The combination of the following aspects: a blue shift of the G band position, a slight increase in the FWHM (Full Width at Half Maximum), and a slight increase of the Raman intensities of both G and 2D bands in other GS without UnR supports the argument of shielded SERS effect. On the other hand, the effects of UnR on the S1 and S2 substrates produce a decrease on the Raman intensities of G and 2D bands, opposite to the effect produced by the AuNPs; this result was found more intense for the S2 substrate in relation to S1. This is possibly caused by the greater amount of UnR accumulated on the Si/SiO2 substrate, due to its higher hydrophilicity in relation to other samples. Additional Raman measurements reveal that the Raman intensity of GS in all substrates is unaffected by the presence of a possible humidity on GS, revealing the effect of UnR. Hence, it is vital to understand how residues influence the salient features of GS/AuNPs.

The intensities of the Raman lines of the ceramic complex (lead titanate) have been investigated as a function of the relation of the areas of the low Raman frequency modes E(1TO) and silent. A change of tetragonal phase into cubic material was observed by Raman spectrjky. The samples were subjected to the same conditions at the time of making the Raman measurements. The UV-vis spectra of absorption suggested a change in energy levels with increasing concentration of lanthanum element (La). This study’s intention is to observe structural changes in the material by means of Raman intensities without using the traditional central position of the peak width in the bands. Resumen Las intensidades de las líneas Raman del cerámico complejo (titanato de plomo) se han investigado como una función de la relación de las áreas de los modos Raman de baja frecuencia E(1TO) y silenciosos. Un cambio de fase tetragonal dentro del material cúbico fue observado por espectroscopía Raman. Las muestras fueron sometidas a las mismas condiciones en el momento de realizar las mediciones de Raman. Los espectros UV-vis de absorción sugirieron un cambio en los niveles de energía al aumentar la concentración del elemento de lantano (La). La intención de este estudio es observar cambios estructurales en el material mediante intensidades Raman sin utilizar la posición central tradicional del ancho máximo en las bandas.

PbZr0.38Ti0.62O3 and PbZr0.36Ti0.64O3 thick films deposited by screen printing on (0 0 0 1) single crystal sapphire substrates and prepared at two different sintering temperatures, were studied by Fourier-transform infrared reflectivity, time-domain THz transmission spectroscopy and micro-Raman spectroscopy. The dielectric response is discussed using the Lichtenecker model to account for the porosity of the films and to obtain the dense bulk dielectric functions. Results are compared with bulk tetragonal PZT 42/58 ceramics. The dynamic response in the films is dominated by an overdamped lead-based vibration in the THz range, as known in PZT, but its evaluated dielectric contribution is affected by the porosity and roughness of the surface.

Objective: To analyze concentration of phosphate ν1 molecule in dental enamel by means of Raman spectroscopy after applying dental bleaching materials at different concentrations. Methodology: 30 recently extracted human teeth were selected. Teeth were free of caries and pigmentations. Raman specters were obtained from each tooth before application of bleaching agents. Specimens were divided into three experimental groups according to the chemical activation of the used bleaching material concentration (Day White®, Discus Dental). Group 1: 9.5% hydrogen peroxide, group 2: 14% hydrogen peroxide, and group 3: 38% hydrogen peroxide. With a Raman spectroscope ν1 phosphate molecule concentration was measured in the dental enamel before application as well as at second and fourth week of bleaching procedure. For repetitive measurements (p ≤ 0.05) ANOVA variance analysis was conducted. Results: In experimental groups 2 and 3 (p ≤ 0.05), a decrease in concentration of phosphate ν1 molecule was observed during treatment execution and at treatment completion group 1 did not reveal statistically signifi cant reduction. Conclusions: Within the limitations inherent to the present study, it was possible to conclude that the bleaching agent caused loss of concentration of the phosphate ν1 molecule. This loss was greater in higher concentration bleaching procedures.

Se sintetizaron compósitos formados entre polióxido de etileno (PEO) y trifluoroacetato de sodio (PEO10CF3COONa) con diferentes concentraciones de óxido de aluminio (Al2O3). Los compósitos fueron caracterizados por espectroscopía infrarroja (IR), espectroscopía Raman, difracción de rayos X (XRD) y microscopía de fuerza atómica (AFM). Las combinaciones del electrolito sólido PEO10CF3COONa con diferentes concentraciones de Al2O3, mostraron cambios en la intensidad de los picos de XRD, así como cambios en la intensidad y posición de algunos picos de IR y Raman. El decrecimiento de los picos del PEO en XRD, cuando este fue combinado con la sal, reveló que la cristalinidad del polímero se redujo, siendo más baja cuando se le adicionó alúmina. Se observó un incremento en la raíz cuadrática media de la rugosidad (RRMS) obtenida por microscopia de fuerza atómica cuando se adicionó Al2O3. Este incremento está en concordancia con la reducción de la cristalinidad observada con estudios de XRD. Los cambios en la estructura del PEO mostrados en las líneas de absorción de IR y Raman, debidos a la adición de CF3COONa y Al2O3, fueron atribuidos a interacciones entre el electrolito y el relleno Al2O3.

Resumen [18] La aplicación de las técnicas espectroscópicas en el análisis de la evidencia forense es cada vez más frecuente debido la sensibilidad y confiabilidad de éstas. Se ha encontrado que cuando la evidencia consiste en fragmentos de pintura automotriz, las técnicas microscópicas de análisis visual en conjunto con las técnicas espectroscópicas, como la técnica Raman y el infrarrojo, pueden ayudar a identificar el vehículo del que proviene el fragmento. En este trabajo se demuestra que la técnica Raman resulta muy conveniente en el análisis de pequeños fragmentos de pintura, pues permite establecer su procedencia por comparación del perfil de los espectros, además, permite identificar algunos de los constituyentes de la pintura: matriz polimérica, pigmentos y otros componentes secundarios. En Costa Rica, el uso de la técnica de espectroscopía Raman, como parte de los análisis rutinarios en el Departamento de Ciencias Forenses del OIJ, está en proceso de desarrollo y por ello consideramos que los resultados de esta investigación pueden contribuir a su implementación. Abstract [22] Nowadays, the application of spectroscopic techniques in the analysis of forensic evidence is increasingly common due to its sensitivity and reliability. When evidence consists of fragments of automotive paint, microscopic and visual analysis techniques, in conjunction with other techniques, such as Raman and infrared spectroscopy, can help to identify the vehicle from which the fragment comes from. This paper shows that using Raman spectroscopy is very favorable in the analysis of small fragments of paint, because it allows establishing its origin by comparing profiles of different spectra. In addition, by this technique the identification of some of the constituents of the automotive paint such as: the polymeric matrix, the pigments and, other minor components can be performed. In Costa Rica, the use of Raman spectroscopy technique as part of a routine analysis in the Department of Forensic Sciences of the Organismo de Investigación Judicial (OIJ) is under development; therefore, the results of this research could contribute to its implementation.