Articles de revues : « Two dimensional visible spectroscopy »

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Belabas, Nadia, et Manuel Joffre. « Visible–infrared two-dimensional Fourier-transform spectroscopy ». Optics Letters 27, n^o 22 (15 novembre 2002) : 2043. http://dx.doi.org/10.1364/ol.27.002043.

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Mewes, Lars, Rebecca A. Ingle, Andre Al Haddad et Majed Chergui. « Broadband visible two-dimensional spectroscopy of molecular dyes ». Journal of Chemical Physics 155, n^o 3 (21 juillet 2021) : 034201. http://dx.doi.org/10.1063/5.0053554.

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Cassette, Elsa, Jacob C. Dean et Gregory D. Scholes. « Two-Dimensional Visible Spectroscopy For Studying Colloidal Semiconductor Nanocrystals ». Small 12, n^o 16 (5 février 2016) : 2234–44. http://dx.doi.org/10.1002/smll.201502733.

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Vietze, Laura, Ellen H. G. Backus, Mischa Bonn et Maksim Grechko. « Distinguishing different excitation pathways in two-dimensional terahertz-infrared-visible spectroscopy ». Journal of Chemical Physics 154, n^o 17 (7 mai 2021) : 174201. http://dx.doi.org/10.1063/5.0047918.

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Meisel, D. C., M. Deubel, M. Hermatschweiler, K. Busch, W. Koch, G. von Freymann, A. Blanco, C. Enkrich et M. Wegener. « Three-Dimensional Photonic Crystals ». Solid State Phenomena 99-100 (juillet 2004) : 55–64. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.55.

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We review our work on two complementary and compatible techniques, namely direct laser writing and holographic lithography which are suitable for fabricating three-dimensional Photonic Crystal templates for the visible and near-infrared. The structures are characterized by electron micrographs and by optical spectroscopy, revealing their high optical quality.

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Silfies, Myles C., Yuning Chen, Henry Timmers, Abijith S. Kowligy, Alex Lind, Scott A. Diddams et Thomas K. Allison. « Widely tunable cavity-enhanced ultrafast spectroscopy ». EPJ Web of Conferences 205 (2019) : 01024. http://dx.doi.org/10.1051/epjconf/201920501024.

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Generation of widely tunable frequency combs in the UV, visible, and infrared is discussed for use in cavity-enhanced transient absorption spectroscopy on gas-phase clusters. Progress towards cavity-enhanced two-dimensional spectroscopy is also presented.

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Li, Zi-Long, et Yuan Wan. « A theoretical survey of two-dimensional coherent spectroscopy in strongly-correlated electronic systems ». Acta Physica Sinica 70, n^o 23 (2021) : 230308. http://dx.doi.org/10.7498/aps.70.20211556.

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Two-dimensional coherent spectroscopy (2DCS) diagnoses a material’s nonlinear optical response with multiple time variables, thus offering information that is inaccessible with conventional linear optical spectroscopy. The 2DCS in the infrared, visible, and ultraviolet frequency range has yielded fruitful results in chemistry and biology. In the terahertz (THz) frequency window, 2DCS has shown its promise in the study of strongly-correlated electronic systems. As a guide to this rapidly developing field, we survey the current status of the theory of THz-2DCS in strongly-correlated electronic systems. We then introduce the basic concepts and theoretical methods of 2DCS, and analyze the main characteristics of the two-dimensional spectra. Finally, we summarize our latest theoretical research in this field.

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Guo, Xunmin, Hailong Chen, Xiewen Wen et Junrong Zheng. « Electron-phonon interactions in MoS2 probed with ultrafast two-dimensional visible/far-infrared spectroscopy ». Journal of Chemical Physics 142, n^o 21 (7 juin 2015) : 212447. http://dx.doi.org/10.1063/1.4921573.

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Liu, Yongliang, Yud-Ren Chen et Yukihiro Ozaki. « Two-Dimensional Visible/Near-Infrared Correlation Spectroscopy Study of Thermal Treatment of Chicken Meats ». Journal of Agricultural and Food Chemistry 48, n^o 3 (mars 2000) : 901–8. http://dx.doi.org/10.1021/jf990662b.

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Zhang, Zhengyong, Min Sha, Yuehu Wang et Haiyan Wang. « Chemical Perturbation Two-Dimensional Correlation Ultraviolet Visible Spectroscopy for Quality Control of Chinese Liquor ». Journal of the American Society of Brewing Chemists 76, n^o 2 (23 février 2018) : 141–46. http://dx.doi.org/10.1080/03610470.2017.1406257.

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Shen, Y. R. « Exploring new opportunities with sum-frequency nonlinear optical spectroscopy ». Pure and Applied Chemistry 73, n^o 10 (1 octobre 2001) : 1589–98. http://dx.doi.org/10.1351/pac200173101589.

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Over the last decade, infrared-visible sum-frequency generation has been developed into a powerful vibrational spectroscopic technique, especially for surface studies. We give here a brief review of the technique and a few recent applications of the technique to liquid and polymer surfaces. We also describe how the technique has found unique applications in our studies of surface melting of ice, ferroelectric ice films, and molecular chirality in chiral liquids. Doubly resonant sum-frequency generation as surface-specific two-dimensional spectroscopy is discussed.

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Son, Minjung, Alberta Pinnola, Roberto Bassi et Gabriela S. Schlau-Cohen. « Ultrabroadband two-dimensional electronic spectroscopy reveals energy flow pathways in LHCII across the visible spectrum ». EPJ Web of Conferences 205 (2019) : 09034. http://dx.doi.org/10.1051/epjconf/201920509034.

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We utilise ultrabroadband two-dimensional electronic spectroscopy to map out pathways of energy flow in LHCII across the entire visible region. In addition to the well-established, low-lying chlorophyll Qy bands, our results reveal additional pathways of energy relaxation on the higher-lying excited states involving the S2 energy levels of carotenoids, including ultrafast carotenoid-to-chlorophyll energy transfer on 90-150 fs timescales.

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Mahdiyanti, Siti Hanifah, Tetsuya Inagaki et Satoru Tsuchikawa. « Analysis of wood thermal degradation using 2D correlation of near infrared and visible-light spectroscopy ». Journal of Near Infrared Spectroscopy 27, n^o 5 (23 juillet 2019) : 354–69. http://dx.doi.org/10.1177/0967033519863878.

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Wood changes its properties, especially color, as a result of thermal degradation. In this study, change in wood properties due to thermal degradation have been studied using the nondestructive test methods of near infrared spectroscopy, CIELAB color measurement, visible-light spectroscopy, and Arrhenius time–temperature superposition. Arrhenius time–temperature superposition allowed analysis of near infrared and visible-light spectra, and color parameters to predict thermal degradation and color change of wood at 120–180℃ for 6 min to nine months duration. Two-dimensional correlation spectroscopy for the complementary analysis of near infrared and visible-light spectroscopy was applied to investigate chemical changes during wood thermal degradation that cause the observed color change. Visible-light spectroscopy with CIELAB color measurement was used to obtain information on color changes, and near infrared spectroscopy was applied in the measurement of chemical changes during thermal degradation. Changes in spectral intensities in 2D correlation spectroscopy indicated that different chemical components are responsible for color change during heat treatment and accelerated aging of wood. With dry-thermal treatment, the hemicellulose content decreased following a color change, whereas cellulose and lignin/extractives decreased with hygro-thermal treatment.

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Han, Bingbing, Sila Jin, Qi Chu, Yang Jin, Xiangxin Xue, Shuang Guo, Yeonju Park, Lei Chen et Young Mee Jung. « New insight into SPR modulating by two-dimensional correlation spectroscopy : the case for an Ag/ITO system ». Nanoscale 12, n^o 48 (2020) : 24357–61. http://dx.doi.org/10.1039/d0nr06256a.

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The localized surface plasmon resonance (LSPR) of Ag/indium tin oxide (ITO)@polystyrene (PS) in the visible-NIR region was dependent on the tuning of the carrier density caused by adjusting the thickness of the ITO layer.

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Vallimeena, S., et B. Helina. « Effect of Calcium on Two-Dimensional Morphology and Photocatalytic Properties of Tin Oxide Nanoparticles ». Asian Journal of Chemistry 35, n^o 3 (2023) : 679–86. http://dx.doi.org/10.14233/ajchem.2023.27550.

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A simple, inexpensive and environmental friendly co-precipitation approach has been used to synthesize calcium doped SnO2 photocatalysts effectively with a high surface area. The X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopies all have been used to characterize the structural, morphological, optical and electrochemical properties of the prepared SnO2:Ca nanoparticles. Both crystallized SnO2 and SnO2:Ca nanoparticles have tetragonal geometry. The structure and defects of the prepared sample were verified by the Raman spectra. The redshift in optical investigations confirmed the reduction in the optical band gap with increasing Ca content. The photocatalytic decomposition of methylene blue were also carried out using prepared SnO2:Ca nanoparticles in visible light. In particular, when compared to other samples, the SnO2:Ca (7 wt.%) nanoplates show the best photocatalytic activity which is confirmed from the low photoluminescence spectrum. By evenly dispersing Ca atoms across the SnO2 matrix, the band gap may be significantly lowered, allowing for more effective separation of photogenerated electron-hole pairs and, in turn, more visible-light absorption. The charge separation efficacy of SnO2:Ca (7 wt.%) nanoplates has been confirmed by EIS measurements.

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Liu, Yongliang, Yud-Ren Chen et Yukihiro Ozaki. « Characterization of Visible Spectral Intensity Variations of Wholesome and Unwholesome Chicken Meats with Two-Dimensional Correlation Spectroscopy ». Applied Spectroscopy 54, n^o 4 (avril 2000) : 587–94. http://dx.doi.org/10.1366/0003702001949780.

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Generalized two-dimensional (2D) correlation analysis of visible spectra (400–700 nm) was performed to characterize the spectral intensity variations of wholesome and five different classes of unwholesome chicken meats. The meats were obtained from the chicken carcasses that were judged to be wholesome or condemned by a Food Safety and Inspection Service (FSIS) veterinarian at a poultry processing plant. The unwholesome carcasses were condemned either because they were improperly bled (cadaver) or showed a disease symptom such as air-sacculitis, ascites, septicemia, or tumors. The results showed that there are at least three prominent bands around 445, 485, and 560 nm that could be attributed to deoxymyoglobin, metmyoglobin, and oxymyoglobin absorption, respectively. The results also demonstrated that deoxymyoglobin, metmyoglobin, and oxymyoglobin components coexist in all meats. There is, however, a clear indication that there were more variations in oxymyoglobin and deoxymyoglobin and less variations in metmyoglobin in the wholesome and cadaver meats than in the diseased meats. The asynchronous spectral analysis of the wholesome and unwholesome meats revealed that the spectral intensity change at the 485 nm band occurs later than those of the 445 and 560 nm bands. It indicates that metmyoglobin, the degraded species of both the deoxymyoglobin and oxymyoglobin, mainly existed in the diseased meats.

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Hutzler, Andreas, Christian D. Matthus, Christian Dolle, Mathias Rommel, Michael P. M. Jank, Erdmann Spiecker et Lothar Frey. « Large-Area Layer Counting of Two-Dimensional Materials Evaluating the Wavelength Shift in Visible-Reflectance Spectroscopy ». Journal of Physical Chemistry C 123, n^o 14 (8 mars 2019) : 9192–201. http://dx.doi.org/10.1021/acs.jpcc.9b00957.

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Nakaya, Yuki, Satoru Nakashima et Mihoko Moriizumi. « Nondestructive Spectroscopic Tracing of Simulated Formation Processes of Humic-Like Substances Based on the Maillard Reaction ». Applied Spectroscopy 72, n^o 8 (29 mai 2018) : 1189–98. http://dx.doi.org/10.1177/0003702818775737.

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The formation processes of humic-like substances have been simulated by heating a glycine and ribose mixed solution (0.1 mol L−1) at 80 ℃ using the Maillard reaction. Ultraviolet–visible (UV–Vis), three-dimensional excitation emission spectroscopy and size exclusion liquid chromatography succeeded in quantitatively tracing increases of the products during the heating of glycine and ribose mixed solution (0.1 mol L−1). Two-dimensional correlation spectroscopic analyses suggested that a band area around 280 nm ( UV280) and 254 nm absorbance ( UV254) can be used as measures of the formation of furfural-like intermediates and humic-like products, respectively. They were monitored using in situ UV–Vis spectroscopy with the original heatable liquid cell at 60–80 ℃. Kinetic analyses of the obtained data gave activation energies of 91.4–96.6 kJ mol−1. These nondestructive measurements by an in situ spectroscopic method did not require any additional procedures including drying or extracting the solution and they can be effectively used for direct tracing of the reaction progress and/or decomposition.

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He, Xiao Chun, Lin Bian, Bo Zhang, Lu Wei Ma, Bin Guo, Ming Jun Gao, Xing Fa Ma et Guang Li. « Two-Dimensional Composite Biomimetic Films with Wide Optical Spectrum Response and their Properties ». Materials Science Forum 848 (mars 2016) : 57–63. http://dx.doi.org/10.4028/www.scientific.net/msf.848.57.

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Since graphene was discovered, the biomimetic materials with laminated structure (such as, shellfish) had become one of the research-hot fields. Chitosan comes from shellfish, and was considered as a very promising abundant natural biopolymer. It holds not only outstanding mechanical properties, film-forming technology and low cost, but also has good applications in environmental fields due to its excellent adsorption properties to a broad range of organic pollutants and some heavy metal ions. Preparation of biomimetic materials with laminated structure utilizing chitosan have many advantages, however, to improve functional properties of chitosan based biomimetic materials is still a great challenge. Graphene has various applications, including storage energy devices, hydrogen production with photo-catalysts, and environmental fields because of its high charge mobility and good mechanical properties. However, graphene and its oxide have difficult re-dispersion properties in fabrication of nanocomposite. In this paper, the nanosheets stacking of metal oxide and grapheme oxide with aid of chitosan was carried out. Several characterizations were examined by SEM (scanning electron microscopy), XRD (X-ray diffraction), ultraviolet-visible spectroscopy (UV-Vis), and Fourier-Transform Infrared (FTIR) spectra. Photocatalytic tests were examined by selecting typical organic pollutants. The photoconductivity response of nanocomposite film to visible light and 808 nm laser with low-power were investigated based on interdigital electrodes of Au on flexible PET (polyethylene terephthalate) film substrate. The results indicated that the organic-inorganic film not only had wide visible light and NIR (near-infrared) responses, but also had good removal ability to organic pollutants. The nanocomposite film also exhibited clearly photo-response to visible light and 808 nm laser. It would be potential good applications in self-cleaning film, nanocoating, et al.

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Yan, Xiaoxia, Gang Liu, Lianzhou Wang, Yong Wang, Xianfang Zhu, Jin Zou et Gao Qing (Max) Lu. « Antiphotocorrosive photocatalysts containing CdS nanoparticles and exfoliated TiO2 nanosheets ». Journal of Materials Research 25, n^o 1 (janvier 2010) : 182–88. http://dx.doi.org/10.1557/jmr.2010.0007.

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Aimed at designing an efficient visible light active photocatalyst and suppressing the self-corrosion tendency of CdS nanoparticles, a novel composite consisting of CdS nanoparticles and exfoliated two-dimensional (2D) TiO2 nanosheets was successfully fabricated using a simple self-assembly process. The prepared samples were characterized using various techniques including x-ray diffraction, ultraviolet–visible absorption spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. It was found that the exfoliated 2D nanosheets played an important role as an ultrathin coating to suppress the photocorrosion of CdS nanoparticles, evidenced by inductively coupled plasma-atomic emission spectrometer analysis. The resultant CdS/TiO2 composites exhibited enhanced photocatalytic activity in the oxidation of Rhodamine B in water under visible light irradiation (λ > 420 nm).

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Garcia-Nieto, David, Nuria Benavent, Rafael Borge et Alfonso Saiz-Lopez. « Two-dimensional monitoring of air pollution in Madrid using a Multi-AXis Differential Optical Absorption Spectroscopy two-dimensional (MAXDOAS-2D) instrument ». Atmospheric Measurement Techniques 14, n^o 4 (17 avril 2021) : 2941–55. http://dx.doi.org/10.5194/amt-14-2941-2021.

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Abstract. Trace gases play a key role in the chemistry of urban atmospheres. Therefore, knowledge about their spatial distribution is needed to fully characterize air quality in urban areas. Using a new Multi-AXis Differential Optical Absorption Spectroscopy two-dimensional (MAXDOAS-2D) instrument, along with an inversion algorithm (bePRO), we report the first two-dimensional maps of nitrogen dioxide (NO2) and nitrous acid (HONO) concentrations in the city of Madrid, Spain. Measurements were made during 2 months (6 May–5 July 2019), and peak mixing ratios of 12 and 0.7 ppbv (parts per billion by volume) for NO2 and HONO, respectively, were observed in the early morning in the southern part of the downtown area. We found good general agreement between the MAXDOAS-2D mesoscale observations – which provide a typical spatial range of a few kilometers – and the in situ measurements provided by Madrid's air quality monitoring stations. In addition to vertical profiles, we studied the horizontal gradients of NO2 in the surface layer by applying the different horizontal light path lengths in the two spectral regions included in the NO2 spectral analysis: ultraviolet (UV, at 360 nm) and visible (VIS, 477 nm). We also investigate the sensitivity of the instrument to infer vertically distributed information on aerosol extinction coefficients and discuss possible future ways to improve the retrievals. The retrieval of two-dimensional distributions of trace gas concentrations reported here provides valuable spatial information for the study of air quality in the city of Madrid.

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Schultz, Jeremy F., et Nan Jiang. « Characterizations of two-dimensional materials with cryogenic ultrahigh vacuum near-field optical microscopy in the visible range ». Journal of Vacuum Science & ; Technology A 40, n^o 4 (juillet 2022) : 040801. http://dx.doi.org/10.1116/6.0001853.

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The development of new characterization methods has resulted in innovative studies of the properties of two-dimensional (2D) materials. Observations of nanoscale heterogeneity with scanning probe microscopy methods have led to efforts to further understand these systems and observe new local phenomena by coupling light-based measurement methods into the tip-sample junction. Bringing optical spectroscopy into the near-field in ultrahigh vacuum at cryogenic temperatures has led to highly unique studies of molecules and materials, yielding new insight into otherwise unobservable properties nearing the atomic scale. Here, we discuss studies of 2D materials at the subnanoscale where the measurement method relies on the detection of visible light scattered or emitted from the scanning tunneling microscope (STM). We focus on tip-enhanced Raman spectroscopy, a subset of scattering-type scanning near-field optical microscopy, where incident light is confined and enhanced by a plasmonic STM tip. We also mention scanning tunneling microscope induced luminescence, where the STM tip is used as a highly local light source. The measurement of light-matter interactions within the atomic STM cavity is expected to continue to provide a useful platform to study new materials.

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Liu, Yongliang, et Yud-Ren Chen. « Two-Dimensional Correlation Spectroscopy Study of Visible and Near-Infrared Spectral Variations of Chicken Meats in Cold Storage ». Applied Spectroscopy 54, n^o 10 (octobre 2000) : 1458–70. http://dx.doi.org/10.1366/0003702001948600.

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Wang, Zhi-Xiang, Hai-Xin Tian, Jian-Gang Ding, Bao-Long Li et Bing Wu. « A Co-MOF with a (4,4)-connected binodal two-dimensional topology : synthesis, structure and photocatalytic properties ». Acta Crystallographica Section C Structural Chemistry 76, n^o 1 (6 décembre 2019) : 23–29. http://dx.doi.org/10.1107/s2053229619016097.

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The Co-MOF poly[[diaqua{μ4-1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene-κ4 N:N′:N′′:N′′′}cobalt(II)] benzene-1,4-dicarboxylic acid benzene-1,4-dicarboxylate], {[Co(C34H24N12)(H2O)2](C8H4O4)·C8H6O4} n or {[Co(ttpe)(H2O)2](bdc)·(1,4-H2bdc)} n , (I), was synthesized by the hydrothermal method using 1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene (ttpe), benzene-1,4-dicarboxylic acid (1,4-H2bdc) and Co(NO3)2·6H2O, and characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD), luminescence, optical band gap and valence band X-ray photoelectron spectroscopy (VB XPS). Co-MOF (I) shows a (4,4)-connected binodal two-dimensional topology with a point symbol of {44·62}{44·62}. The two-dimensional networks capture free neutral 1,4-H2bdc molecules and bdc2− anions, and construct a three-dimensional supramolecular architecture via hydrogen-bond interactions. MOF (I) is a good photocatalyst for the degradation of methylene blue and rhodamine B under visible-light irradiation and can be reused at least five times.

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Li, Dengshan, et Lina Li. « Detection of Water pH Using Visible Near-Infrared Spectroscopy and One-Dimensional Convolutional Neural Network ». Sensors 22, n^o 15 (3 août 2022) : 5809. http://dx.doi.org/10.3390/s22155809.

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pH is an important parameter for water quality detection. This study proposed a novel calibration regression strategy based on a one-dimensional convolutional neural network (1D-CNN) for water pH detection using visible near-infrared (Vis-NIR) spectroscopy. Two groups of Vis-NIR spectral analysis experiments of water pH detection were employed to evaluate the performance of 1D-CNN. Two conventional multivariate regression calibration methods, including partial least squares (PLS) and least squares support vector machine (LS-SVM), were introduced for comparative analysis with 1D-CNN. The successive projections algorithm (SPA) was adopted to select the feature variables. In addition, the learning mechanism of 1D-CNN was interpreted through visual feature maps by convolutional layers. The results showed that the 1D-CNN models obtained the highest prediction accuracy based on full spectra for the two experiments. For the spectrophotometer experiment, the root mean square error of prediction (RMSEP) was 0.7925, and the determination coefficient of prediction (Rp2) was 0.8515. For the grating spectrograph experiment, the RMSEP was 0.5128 and the Rp2 was 0.9273. The convolutional layers could automatically preprocess the spectra and effectively extract the spectra features. Compared with the traditional regression methods, 1D-CNN does not need complex spectra pretreatment and variable selection. Therefore, 1D-CNN is a promising regression approach, with higher prediction accuracy and better modeling convenience for rapid water pH detection using Vis-NIR spectroscopy.

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Ferjani, Hela. « Crystal structure, optical property and Hirshfeld surface analysis of bis[1-(prop-2-en-1-yl)-1H-imidazol-3-ium] hexachloridostannate(IV) ». Acta Crystallographica Section E Crystallographic Communications 76, n^o 10 (8 septembre 2020) : 1624–28. http://dx.doi.org/10.1107/s2056989020012177.

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A new 0D organic–inorganic hybrid material bis[1-(prop-2-en-1-yl)-1H-imidazol-3-ium] hexachloridostannate(IV), (C6H9N2)2[SnCl6], has been prepared and characterized by single-crystal X-ray diffraction, Hirshfeld surface analysis and UV–visible spectroscopy. The structure consists of isolated [SnCl6]2− octahedral anions separated by layers of organic 1-(prop-2-en-1-yl)-1H-imidazol-3-ium cations. The 1-(prop-2-en-1-yl) fragment in the organic cation exhibits disorder over two sets of atomic sites having occupancies of 0.512 (9) and 0.488 (9). The crystal packing of the title compound is established by intermolecular N/C–H...Cl hydrogen bond and π– π stacking interactions. Hirshfeld surface analysis employing three-dimensional molecular surface contours and two-dimensional fingerprint plots has been used to analyse the intermolecular interactions present in the structure. The optical properties of the crystal were studied using UV–visible absorption spectroscopy, showing one intense band at 208 nm, which is attributed to π–π* transitions in the cations.

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Zhang, Tao, Lu Chen, Jing Yao et Qi Zhu. « A Two-Dimensional Guidance Strategy to Fabricate Perovskite Gadolinium Aluminate Ceramic Film ». Coatings 12, n^o 12 (8 décembre 2022) : 1927. http://dx.doi.org/10.3390/coatings12121927.

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Gadolinium aluminate is an effective host for doping with various ions, and it can emit various colors. However, it is not easy to prepare transparent ceramics of gadolinium aluminate using traditional methods, although transparent ceramics are very suitable for solid lighting. In this work, a two-dimensional guidance strategy has been successfully carried out for perovskite-structured aluminate ceramic film. Through the two-dimensional interfacial reaction, GdAlO3:Eu3+ (GAP:Eu3+) transparent ceramic films were successfully fabricated using nanosheets exfoliated from layered gadolinium hydroxide, a rare earth source. The final films were tested by characterization techniques, including XRD, SEM, TEM, FT-IR, PLE/PL spectroscopy, temperature-dependent PL spectroscopy, and luminescence decay analysis. The perovskite film of transparent ceramics can be obtained by calcining LRH nanosheets on the substrate of amorphous alumina at 1550 °C in air with a reaction time of 2 h. During the interface reaction, temperature-dependent element diffusion takes the dominant role, and increased reactants take in the reaction with increasing calcination temperature. The grain for ceramic film is only 2–5 μm, which is much smaller than that for bulk ceramic. This is mainly due to the lower temperature and the interface diffusion. Ceramic film has a high transmittance larger than 90% at the visible range. Upon UV excitation at 254 nm, the film exhibits intense emission at the red wavelength range. The outcomes described in this work may have wide implications for transparent ceramics and layered rare-earth hydroxides.

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Tsubouchi, Masaaki, Nobuhisa Ishii, Yuji Kagotani, Rumi Shimizu, Takatoshi Fujita, Motoyasu Adachi et Ryuji Itakura. « Beat-frequency-resolved two-dimensional electronic spectroscopy : disentangling vibrational coherences in artificial fluorescent proteins with sub-10-fs visible laser pulses ». Optics Express 31, n^o 4 (10 février 2023) : 6890. http://dx.doi.org/10.1364/oe.480505.

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We perform a beat-frequency-resolved analysis for two-dimensional electronic spectroscopy using a high-speed and stable 2D electronic spectrometer and few-cycle visible laser pulses to disentangle the vibrational coherences in an artificial fluorescent protein. We develop a highly stable ultrashort light source that generates 5.3-fs visible pulses with a pulse energy of 4.7 µJ at a repetition rate of 10 kHz using multi-plate pulse compression and laser filamentation in a gas cell. The above-5.3-fs laser pulses together with a high-speed multichannel detector enable us to measure a series of 2D electronic spectra, which are resolved in terms of beat frequency related to vibrational coherence. We successfully extract the discrete vibrational peaks behind the inhomogeneous broadening in the absorption spectra and the vibrational quantum beats of the excited electronic state behind the strong incoherent population background in the typical 2D electronic spectra.

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Sadergaski, Luke R., et Kyle Morgan. « Applying Two-Dimensional Correlation Spectroscopy and Principal Component Analysis to Understand How Temperature Affects the Neptunium(V) Absorption Spectrum ». Chemosensors 10, n^o 11 (12 novembre 2022) : 475. http://dx.doi.org/10.3390/chemosensors10110475.

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The visible-near infrared (Vis-NIR) electronic absorption spectrum of neptunium(V) (NpO2+) comprises numerous f-f electronic transitions with mostly undocumented temperature dependencies. The effect of temperature on the absorption spectrum of the pentavalent neptunyl dioxocation (NpO2+) is an important factor to consider with spectrophotometric applications but has often been overlooked. Optical Vis-NIR absorption spectra (400–1700 nm) of Np(V) (0.017–0.89 M) in 1 M nitric acid were evaluated with varying temperatures (T = 10–80 °C). The intensity, position, and overall shape of the bands were sensitive to interactions with the solvent and coordination environment. Numerous temperature-induced isosbestic points were identified resulting from dynamic, overlapping peak shifts. Spectral variations were characterized using principal component analysis (PCA) and 2D correlation spectroscopy (COS). 2D-COS revealed that the absorption band near 1095 nm likely consists of two bands centered near 1087 and 1096 nm, which cannot be explained by current computational methods. 2D-COS analysis also provided an unambiguous assignment of unresolved peaks in the visible region for comparison with computational predictions. PCA was used to identify nonlinearity in the spectral response at elevated Np(V) concentrations ≥ 0.5 M. This unique experimental data and interpretation will foster a deeper understanding of the absorption spectra for complex actinyl ions.

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Hassoun, Abdo. « Exploring the Potential of Fluorescence Spectroscopy for the Discrimination between Fresh and Frozen-Thawed Muscle Foods ». Photochem 1, n^o 2 (2 septembre 2021) : 247–63. http://dx.doi.org/10.3390/photochem1020015.

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Substitution of frozen-thawed food products for fresh ones is a significant authenticity issue being extensively investigated over the past few years by various conventional methods, but little success has been achieved. Fluorescence spectroscopy is a sensitive and selective spectroscopic technique that has been widely applied recently to deal with various food quality and authenticity issues. The technique is based on the excitation of certain photosensitive components (known as fluorophores) to fluoresce in the UV and visible spectral ranges. Fluorescence spectroscopy can be performed to obtain simple classical two-dimensional fluorescence spectra (excitation/emission), synchronous or three-dimensional excitation–emission matrices (excitation/emission/fluorescence signal). The technique can be used in front-face or right-angle configurations and can be even combined with hyperspectral imaging, requiring the use of multivariate data analysis to extract useful information. In this review, we summarize the recent progress in applications of fluorescence spectroscopy to differentiate truly fresh foods from frozen-thawed products. The basics of the technique will be briefly presented and some relevant examples, focusing especially on fish and meat products, will be given. It is believed that interdisciplinary collaboration between researchers working with data analysis and spectroscopy, as well as industry and regulatory authorities would help to overcome the current shortcomings, holding the great promise of fluorescence spectroscopy for fighting food fraud in the food industry.

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Li, Jia-Le, Wei-Dong Li, Zi-Wei He, Shuai-Shuai Han et Shui-Sheng Chen. « Synthesis, Crystal Structure, and Properties of a Zn(II) Coordination Polymer Based on a Difunctional Ligand Containing Triazolyl and Carboxyl Groups ». Crystals 8, n^o 11 (9 novembre 2018) : 424. http://dx.doi.org/10.3390/cryst8110424.

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A new compound, namely, [Zn(L)2]n (1) was obtained by the reaction of 2-methyl-4-(4H-1,2,4-triazol-4-yl) benzoic acid (HL) with ZnSO4·7H2O, and the compound was characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, powder X-ray diffraction (PXRD), and thermogravimetric analysis. The linear HL ligands were deprotonated to be L− anions and act as two-connectors to link Zn2+ to form a two-dimensional (2D) lay structure with (4, 4) topology. The large vacancy of 2D framework allows another layer structure to interpenetrate, resulting in the formation of 2D + 2D → 2D parallel interpenetration in 1. The weak interactions, such as hydrogen bonding and π–π stacking interactions, connect the adjacent 2D layers into a three-dimensional (3D) coordination polymer. The solid-state UV-visible spectroscopy and luminescent property have also been studied.

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Yu, Yu, Wanfu Shen, Guoteng Ma, Qingqing Luo, Yufeng Huang, Huoqing Lu, Haile Wang, Lidong Sun et Chunguang Hu. « Anomalous narrow-band optical anisotropy of MoO₂ crystal in the visible regime ». Applied Physics Letters 121, n^o 25 (19 décembre 2022) : 251901. http://dx.doi.org/10.1063/5.0124683.

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The emergence of anisotropic two-dimensional (2D) materials provides a platform for the cutting-edge nano- and optoelectronic devices. Exploring low-dimensional materials and revealing their anisotropic behavior are crucial for designing angle-dependent nanodevices. The metallicity of molybdenum dioxide (MoO2) crystal differentiates it from the most commonly studied semi-conductive anisotropic 2D materials. However, the studies on its optical anisotropy are still lacking. Here, two most commonly obtained shapes of rhombic and hexagonal MoO2 were synthesized by one step method of chemical vapor deposition. The rhombic and hexagonal MoO2 display a slight frequency shift of 1–5 cm−1 depending on the variation modes, but the Raman modes at 366 cm−1 remain unaltered. Using a combination of differential reflectance spectroscopy and reflectance difference spectroscopy, we revealed the unusual narrow-band optical anisotropies of rhombic and hexagonal MoO2 crystals in the visible wavelength region due to its unique metallic properties. Furthermore, it is found that the center wavelengths of the narrow-band optical anisotropy of the MoO2 crystal can be effectively adjusted by coherent optical interference. Our results present an interesting anisotropic metallic 2D candidate and an effective cavity-based approach to regulate the center wavelengths of as-obtained narrow-band optical anisotropy, which is highly beneficial for the wavelength-selected devices.

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Liu, Ze-Hua, Chuan-Lu Yang, Mei-Shan Wang et Xiao-Guang Ma. « Two-dimensional SiMI4(M = Ge, Sn) monolayers as visible-light-driven photocatalyst of hydrogen production ». Spectrochimica Acta Part A : Molecular and Biomolecular Spectroscopy 261 (novembre 2021) : 120013. http://dx.doi.org/10.1016/j.saa.2021.120013.

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Zhou, Xiao Yan, Peng Wei Zhou, Hao Guo, Bo Yang et Ru Fei Ren. « Photocatalytic Activity of CuO/ZnO Heterostructure Nanocrystals under UV-Visible Light Irradiation ». Materials Science Forum 787 (avril 2014) : 35–40. http://dx.doi.org/10.4028/www.scientific.net/msf.787.35.

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The p-n junction photocatalysts, p-CuO (at. 0-25%)/n-ZnO nanocomposite were prepared through hydrothermal method without using any organic solvent or surfactant. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-Ray spectroscopy, and UV-vis spectroscopy. The results demonstrated that the CuO/ZnO nanocomposite presented a two-dimensional morphology composed of sheet-like ZnO nanostructures adorned with CuO nanoparticles. The photocatalytic activity of CuO/ZnO with different Cu/Zn molar rations and pure ZnO synthesized by the identical synthetic route were evaluated by degrading methylene blue (MB) dye under UV-visible light irradiation. The CuO/ZnO with Cu/Zn molar ratio of 4% exhibits the highest photocatalytic activity compared that of the other photocatalysts under the identical conditions. It is mainly attributed to the increased charge separation rate in the nanocomposite and the extended photo-responding range.

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Wu, Ming-Der, Ming-Jen Cheng, Yen-Lin Chen, Tai-Wei D. Liu et Kai-Ping Chen. « Screening of Azaphilone Derivatives From Monascus pilosus-Fermented Rice (Red Yeast Rice) and Their Evaluation as Nonsteroidal Androgen Receptor Antagonists ». Natural Product Communications 14, n^o 12 (1 décembre 2019) : 1934578X1987891. http://dx.doi.org/10.1177/1934578x19878918.

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Monascus pilosus BCRC 38093 is a mutant strain of M. pilosus BCRC 38072. The 95% ethanol extract of red yeast rice fermented by M. pilosus BCRC 38093 showed 4 major signals on high performance liquid chromatography (HPLC) examination. The extraction of metabolites and chromatography of the ethyl acetate crude extract on silica gel yielded 2 azaphilone derivatives, monascin (1) and monascinol (2), and 2 monacolin-type derivatives, acid-form monacolin K (3) and lactone-form monacolin K (4). Their structural characterization was elucidated by spectroscopic techniques ultraviolet-visible (UV), infrared spectroscopy (IR), and two dimensional-nuclear magnetic resonance (2D-NMR) and mass spectrometry. These compounds were assayed for their anti-androgen activity; monascinol (2) exhibited strong activity.

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Gantri, M., H. Trabelsi, E. Sediki et R. Ben Salah. « Computational Laser Spectroscopy in a Biological Tissue ». Journal of Biophysics 2010 (7 avril 2010) : 1–9. http://dx.doi.org/10.1155/2010/253763.

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We present a numerical spectroscopic study of visible and infrared laser radiation in a biological tissue. We derive a solution of a general two-dimensional time dependent radiative transfer equation in a tissue-like medium. The used model is suitable for many situations especially when the external source is time-dependent or continuous. We use a control volume-discrete ordinate method associated with an implicit three-level second-order time differencing scheme. We consider a very thin rectangular biological-tissue-like medium submitted to a visible or a near infrared light sources. The RTE is solved for a set of different wavelength source. All sources are assumed to be monochromatic and collimated. The energetic fluence rate is computed at a set of detector points on the boundaries. According to the source type, we investigate either the steady-state or transient response of the medium. The used model is validated in the case of a heterogeneous tissue-like medium using referencing experimental results from the literature. Also, the developed model is used to study changes on transmitted light in a rat-liver tissue-like medium. Optical properties depend on the source wavelength and they are taken from the literature. In particular, light-transmission in the medium is studied for continuous wave and for short pulse.

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Koinkar, Pankaj, Kohei Sasaki, Tetsuro Katayama, Akihiro Furube et Satoshi Sugano. « Laser assisted synthesis of WS2 nanorods by pulsed laser ablation in liquid environment ». International Journal of Modern Physics B 35, n^o 14n16 (24 juin 2021) : 2140007. http://dx.doi.org/10.1142/s0217979221400075.

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Two dimensional (2D) materials are widely attracting the interest of researchers due to their unique crystal structure and diverse properties. In the present work, tungsten disulfide (WS[Formula: see text] nanorods were synthesized by a simple method of pulsed laser ablation in liquid (PLAL) environment. The prepared WS2 are analyzed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and Raman spectroscopy to confirm the surface morphology, phase and structure. A possible growth mechanism of WS2 is proposed. This study indicates new door for the preparation of 2D materials with specific morphology.

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Dhongade, Siddhant, Pankaj Koinkar, Akihiro Furube et Satoshi Sugano. « Liquid exfoliation of graphene oxide nanoribbons using chemical assisted laser ablation ». International Journal of Modern Physics B 35, n^o 14n16 (14 mai 2021) : 2140009. http://dx.doi.org/10.1142/s0217979221400099.

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The interest toward two-dimensional (2D) materials is gradually increasing because of their structure at nanoscale and great importance for electronic and optical applications. In this study, we show the synthesis of graphene oxide (GO) micro-ribbons fabricated by chemical assisted-laser ablation method. In order to confirm the formation of GO, UV-visible spectroscopy (UV-vis) and Raman spectroscopy are used to observe the surface morphological feature and structural details. In addition, a possible mechanism for the growth of GO nanoribbon is discussed. This work indicates a new method to develop GO nanostructures and related nanomaterials.

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Liu, Yongliang, et Yud-Ren Chen. « Two-dimensional visible/near-infrared correlation spectroscopy study of thawing behavior of frozen chicken meats without exposure to air ». Meat Science 57, n^o 3 (mars 2001) : 299–310. http://dx.doi.org/10.1016/s0309-1740(00)00106-6.

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Ksiksi, R., I. Jendoubi, H. Chebbi, M. Graia et M. F. Zid. « Synthesis, characterization, and crystal structure of a novel decavanadate Mg(H2O)6(C6H14N2)2V10O28·8H2O ». Журнал структурной химии 62, n^o 8 (2021) : 1331–38. http://dx.doi.org/10.26902/jsc_id78500.

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A novel decavanadate salt Mg(H2O)6(C6H14N2)2V10O28·8H2O is obtained by the reaction of vanadium oxide and 1,4-diazabicyclo [2.2.2] octane (DABCO). The title compound is characterized by infrared (IR) spectroscopy and powder X-ray diffraction (XRD). The spectroscopic characterization confirms the presence of the different groups in the structure. Powder XRD confirms the purity of the phase. Optical properties are recorded at room temperature using UV-visible spectroscopy in the spectral range of 250—800 nm. According to the single crystal XRD analysis, the structure of the compound is orthorhombic: a = 17.927(6) Å, b = 15.798(6) Å, c = 15.723(5) Å, V = 4452.8(7) Å3, and Z = 4. The formula unit of Mg(H2O)6(C6H14N2)2V10O28·8H2O is formed by a decavanadate group, the Mg(H2O)62+ polyhedron, two organic (C6H14N2)2+ cations, and eight water molecules. In the crystal, molecules are linked by O—H…O and N—H…O hydrogen bonds, forming a three-dimensional network.

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Shin, Kyujin, Yo Song, Yeongchang Goh et Kang Lee. « Two-Dimensional and Three-Dimensional Single Particle Tracking of Upconverting Nanoparticles in Living Cells ». International Journal of Molecular Sciences 20, n^o 6 (21 mars 2019) : 1424. http://dx.doi.org/10.3390/ijms20061424.

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Lanthanide-doped upconversion nanoparticles (UCNPs) are inorganic nanomaterials in which the lanthanide cations embedded in the host matrix can convert incident near-infrared light to visible or ultraviolet light. These particles are often used for long-term and real-time imaging because they are extremely stable even when subjected to continuous irradiation for a long time. It is now possible to image their movement at the single particle level with a scale of a few nanometers and track their trajectories as a function of time with a scale of a few microseconds. Such UCNP-based single-particle tracking (SPT) technology provides information about the intracellular structures and dynamics in living cells. Thus far, most imaging techniques have been built on fluorescence microscopic techniques (epifluorescence, total internal reflection, etc.). However, two-dimensional (2D) images obtained using these techniques are limited in only being able to visualize those on the focal planes of the objective lens. On the contrary, if three-dimensional (3D) structures and dynamics are known, deeper insights into the biology of the thick cells and tissues can be obtained. In this review, we introduce the status of the fluorescence imaging techniques, discuss the mathematical description of SPT, and outline the past few studies using UCNPs as imaging probes or biologically functionalized carriers.

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Yashima, Masatomo, Masato Kakihana, Ryosuke Shimidzu, Hirotaka Fujimori et Masahiro Yoshimura. « Ultraviolet 363.8-nm Raman Spectroscopic System for in Situ Measurements at High Temperatures ». Applied Spectroscopy 51, n^o 8 (août 1997) : 1224–28. http://dx.doi.org/10.1366/0003702971941791.

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A new ultraviolet (UV) Raman spectroscopic system to measure the Raman scattering from materials at high temperatures up to 1500 °C has been designed. This system is based on a CW (continuous-wave) ultraviolet argon-ion laser (363.8 nm), a spatial filter, a single monochromator coupled to a double-grating rejection filter, and a two-dimensional charge-coupled device (CCD) detector. The plasma lines from the laser are almost completely rejected by a Pellin—Broca prism combined with apertures. In situ Raman measurements for a zirconia (ZrO2) specimen at various high temperatures have been performed by using the UV excitation as well as the conventional visible 488.0-nm excitation for comparison. In the case of visible excitation, thermal emission obstructs the observation of the Raman scattering from zirconia even at 900 °C; it becomes rapidly pronounced between 900 and 1100 °C, and finally it is impossible to observe Raman spectra at temperatures higher than 1200 °C. In sharp contrast to the visible excitation, the UV excitation provides good-quality Raman spectra with practically flat backgrounds for the Raman signal of tetragonal zirconia in the spectral region of 20–1100 cm−1 even at 1500 °C, and it enables clear observation of the monoclinic-tetragonal phase transformation of zirconia occurring between 1100 and 1200 °C.

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Mullins, Oliver C., G. Todd Ventura, Robert K. Nelson, Soraya S. Betancourt, Bhavani Raghuraman et Christopher M. Reddy. « Visible–Near-Infrared Spectroscopy by Downhole Fluid Analysis Coupled with Comprehensive Two-Dimensional Gas Chromatography To Address Oil Reservoir Complexity ». Energy & ; Fuels 22, n^o 1 (janvier 2008) : 496–503. http://dx.doi.org/10.1021/ef7003738.

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Wang, Huan, Dong Mei Liu, Peng Wang et Fu Yi Cui. « Structural Characteristics of Intracellular and Extracellular Organic Matter from Microcystis aeruginosa ». Applied Mechanics and Materials 675-677 (octobre 2014) : 163–66. http://dx.doi.org/10.4028/www.scientific.net/amm.675-677.163.

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Algogenic organic matters (AOM) generate from two parts, that are extracellular organic matters (EOM) and intracellular organic matters (IOM). This paper compared the structural characteristics of IOM and EOM originated from Microcystis aeruginosa using techniques including ultra violet-visible spectrum (UV-VIS), Fourier infrared spectrum (FT-IR) and three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy. The results demonstrated that concentrations of the organic matter in EOM were less than that in IOM. EOM has less characteristic absorption peaks. There were more aromatic ring compounds, more protein and amino acids in IOM than EOM.

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Hosseini, Seyedali, Azam Iraji zad, Seyed Mohammad Mahdavi et Ali Esfandiar. « Tunable Gain SnS2/InSe Van der Waals Heterostructure Photodetector ». Micromachines 13, n^o 12 (25 novembre 2022) : 2068. http://dx.doi.org/10.3390/mi13122068.

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Due to the favorable properties of two-dimensional materials such as SnS2, with an energy gap in the visible light spectrum, and InSe, with high electron mobility, the combination of them can create a novel platform for electronic and optical devices. Herein, we study a tunable gain SnS2/InSe Van der Waals heterostructure photodetector. SnS2 crystals were synthesized by chemical vapor transport method and characterized using X-ray diffraction and Raman spectroscopy. The exfoliated SnS2 and InSe layers were transferred on the substrate. This photodetector presents photoresponsivity from 14 mA/W up to 740 mA/W and detectivity from 2.2 × 108 Jones up to 3.35 × 109 Jones by gate modulation from 0 V to +70 V. Light absorption and the charge carrier generation mechanism were studied by the Silvaco TCAD software and the results were confirmed by our experimental observations. The rather high responsivity and visible spectrum response makes the SnS2/InSe heterojunction a potential candidate for commercial visible image sensors.

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Huang, Xiaoguang, Heechul Woo, Daseul Lee, Peinian Wu, Myungkwan Song et Jin Woo Choi. « High-Efficiency Photon-Capturing Capability of Two-Dimensional SnS Nanosheets for Photoelectrochemical Cells ». Catalysts 11, n^o 2 (10 février 2021) : 236. http://dx.doi.org/10.3390/catal11020236.

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Cost-effective, abundant, and non-toxic SnS nanosheet semiconductors can be used as water-splitting cells. Herein, a photoanode based on high-purity and highly crystalline SnS nanosheets was fabricated. We used sodium thiosulfate (Na2S2O3·5H2O) and stannous chloride (SnCl2·2H2O) as the tin and sulfur source materials, in place of SnCl4 and H2S gas, respectively, which have been used in previous studies. This gas-free fabrication process represents a new, environment-friendly fabrication method that can reduce the manufacturing cost of SnS nanosheets. The fabricated samples were characterized via X-ray diffraction, ultraviolet-visible spectroscopy, XPS, scanning electron microscopy, and Raman analyses. The XPS result indicated no Sn0 or Sn4+ in the S3 nanosheet; the nanosheet was SnS. These results with XRD show that the SnS nanosheet has high phase purity and crystallinity. Its direct optical band gap is 1.31 eV, and its lattice parameters are similar to those of standard SnS. The SnS nanosheet-based photoanode exhibited a maximum saturation photocurrent of 6.86 mA cm−2 at 0.57 V versus Ag/AgCl, with high stability. The most effective photocurrent for the photocatalytic water-splitting cell is attained with an increase in the surface area and developed electrical conduction. This is attributed to thermal annealing, which eliminates nanoparticle imperfections. This study confirms that SnS nanosheets are excellent candidates for water-splitting applications.

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Zulick, Calvin, Nagapratima Kunapareddy et Jacob Grun. « Isotope Identification Mechanisms Enabled by Swept-Wavelength Raman Spectroscopy ». Applied Spectroscopy 74, n^o 1 (11 novembre 2019) : 97–107. http://dx.doi.org/10.1177/0003702819878232.

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Swept-wavelength Raman signatures have been measured for isotopic variants of polyethylene, acetic acid, and potassium sulfates. The swept-wavelength measurements produce two-dimensional Raman signatures which enable identification techniques based on changes in Raman peak amplitudes as a function of wavelength. In addition to the typical Raman peak energy shifts, which results from the change in isotope mass, three wavelength dependent mechanisms for isotope identification have been identified. Changes in the shape of the Raman signal, the presence and absence of Raman peaks over specific wavelength ranges, and changes in absorption of the Raman signal were observed as a result of isotopic substitution. These features provide additional specificity in the isotopic Raman signatures which suggests swept-wavelength Raman signatures will facilitate the identification of isotopes in complex and dirty mixtures. Measurements in the visible range suggest that the identification mechanisms are primarily evident in the ultraviolet, or resonance Raman, region.

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Kitagawa, K., N. Konishi, N. Arai et A. K. Gupta. « Temporally Resolved Two-Dimensional Spectroscopic Study on the Effect of Highly Preheated and Low Oxygen Concentration Air on Combustion ». Journal of Engineering for Gas Turbines and Power 125, n^o 1 (27 décembre 2002) : 326–31. http://dx.doi.org/10.1115/1.1520155.

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Spontaneous emission spectroscopy has been applied to measure the time-resolved temperature profiles of gaseous fuel flames using high temperature and low oxygen concentration combustion air. Two emission peaks of C2 radical species have been observed at visible wavelengths from propane-air flames. The ratio of these two peaks depends on the flame temperature. The relationship between the ratios of these peaks was correlated with the thermocouple output using a premixed flat flame burner and a multichannel CCD spectrometer. Using this relationship, the flame temperature was determined from the ratio of the C2 peaks. Time-resolved emission intensity profiles of the two C2 bands (two-wavelength image) were observed simultaneously with a high sensitivity video camera fitted with an optical system. The time-resolved temperature profiles were constructed from these intensity profiles by utilizing the previously determined relationship at each pixel. To evaluate fluctuations of flame temperatures, the standard deviation profiles for the temperature profiles have been constructed. This spectroscopic diagnostic technique has been used to measure the profiles of mean flame temperature and temperature fluctuation produced from a concentric diffusion flame using propane as the fuel and high temperature and low oxygen concentration combustion air. In this study, the effect of air-preheat and low oxygen concentration in the combustion air on the subsequent flame temperature and temperature fluctuations has been determined by analyzing the spectra of spontaneous emission from the C2 radicals.

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Assimiadis, Manolis K., Petros A. Tarantilis et Moschos G. Polissiou. « UV-Vis, FT-Raman, and 1H NMR Spectroscopies of cis-trans Carotenoids from Saffron (Crocus sativus L.) ». Applied Spectroscopy 52, n^o 4 (avril 1998) : 519–22. http://dx.doi.org/10.1366/0003702981944058.

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Stigmata of Crocus sativus L. were extracted in water, and the extract was analyzed by using a high-pressure liquid chromatography (HPLC) method. The carotenoids of saffron [ cis and trans glycosyl esters of crocetin or crocins (CRCs)] were isolated, and the two major isomer compounds (all- trans-digentiobiosyl crocetin and 13- cis-digentiobiosyl crocetin) were characterized spectroscopically with ultraviolet-visible (UV-vis), Fourier transform (FT)-Raman, and 1H NMR spectroscopies. The 13 -cis compound showed in a UV-vis spectrum an additional peak at 330 nm, in an FT-Raman spectrum the presence of a peak at 1138 cm−1, and in the 1H NMR downfield shifts of protons 12 and 15 and an uptield shift of proton 14, with respect to the all-trans isomer, according to differences in their skeletal structures. These features are shown also by the profile of their two-dimensional spectra.

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Wang, Shifang, Xu Cheng, Decong Zheng, Haiyan Song, Ping Han et Peter Yuen. « Prediction of the Soil Organic Matter (SOM) Content from Moist Soil Using Synchronous Two-Dimensional Correlation Spectroscopy (2D-COS) Analysis ». Sensors 20, n^o 17 (26 août 2020) : 4822. http://dx.doi.org/10.3390/s20174822.

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This paper illustrates a simple yet effective spectroscopic technique for the prediction of soil organic matter (SOM) from moist soil through the synchronous 2D correlation spectroscopy (2D-COS) analysis. In the moist soil system, the strong overlap between the water absorption peaks and the SOM characteristic features in the visible-near infrared (Vis-NIR) spectral region have long been recognised as one of the main factors that causes significant errors in the prediction of the SOM content. The aim of the paper is to illustrate how the tangling effects due to the moisture and the SOM can be unveiled under 2D-COS through a sequential correlogram analysis of the two perturbation variables (i.e., the moisture and the SOM) independently. The main outcome from the 2D-COS analysis is the discovery of SOM-related bands at the 597 nm, 1646 nm and 2138 nm, together with the predominant water absorbance feature at the 1934 nm and the relatively less important ones at 1447 nm and 2210 nm. This information is then utilised to build partial least square regression (PLSR) models for the prediction of the SOM content. The experiment has shown that by discarding noisy bands adjacent to the SOM features, and the removal of the water absorption bands, the determination coefficient of prediction (Rp2) and the ratio of prediction to deviation (RPD) for the prediction of SOM from moist soil have achieved Rp2 = 0.92 and the RPD = 3.19, both of which are about 5% better than that of using all bands for building the PLSR model. The very high RPD (=3.19) obtained in this study may suggest that the 2D-COS technique is effective for the analysis of complex system like the prediction of SOM from moist soil.

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