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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Surface-Enhanced Infrared Absorption Spectroscopy
摘要： It has been well established that infrared (IR) spectroscopy is a very useful tool for the investigation of gas–solid interfaces, which provides molecular and geometrical information of adsorbed species. Such information obtained for electrode–electrolyte interfaces would be invaluable for understanding electrochemical processes. However, to record IR signals of species in the proximity of an electrode surface, a problem concerning strong IR absorption by the solvent, especially very strong absorption by water, has to be overcome. A way to do so is to minimize the path length which the IR beam has to travel through the solution.
关键词： metal film preparation,Surface-Enhanced Infrared Absorption Spectroscopy,electrochemical processes,SEIRAS,IR spectroscopy
更新于2025-09-23 15:21:01
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Application of Nanostructured Tungsten Fabricated by Helium Plasma Irradiation for Photoinduced Decolorization of Methylene Blue
摘要： The dendritic nanostructure was fabricated on a surface of tungsten plate by helium plasma irradiation. The nanostructure consisting of W metal was partially oxidized to form WO3 on exposure to air, and the resulting surface exhibited a broad photoabsorption in the range from 1 to 5 eV. We examined photoinduced reaction of methylene blue (MB) on the material. It was found that the partially and fully oxidized surface nanostructures were able to promote a decolorization of MB under photoirradiation even with the near-infrared light (< 1:55 eV), whose energy is lower than the band gap of WO3. The reaction rate was varied with the fraction of W and WO3 on the surface layers, that is, the partially oxidized sample promoted the reaction at a higher rate than the fully oxidized one. It is also found that the reaction rate decreased with time, which would be caused by the products accumulation on the surface and the surface oxidation.
关键词： Scanning electron microscopy (SEM),Tungsten oxide,Surface photochemistry,Plasma processing,Nano-wires, quantum wires, and nanotubes,Visible/ultraviolet absorption spectroscopy, X-ray photoelectron spectroscopy
更新于2025-09-23 15:21:01
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Two dimensional temperature measurement characteristics in pulverized coal combustion field by computed tomography-tunable diode laser absorption spectroscopy
摘要： Two dimensional temperature and concentration distributions are important parameters for pulverized coal combustion used for power plant to understand the combustion field and develop the high efficient combustion technologies. However, it is difficult to measure two dimensional temperature and concentration in pulverized coal combustion field using conventional measurement technologies because pulverized coal combustion produces lots of dust and strong emission from its flame. This paper focused on the application of two dimensional temperature measurement method based on the combination of computed tomography and tunable diode laser absorption spectroscopy using absorption spectra of water vapor at 1388nm and 1343nm for each laser scanning using direct absorption spectroscopy, which show the better characteristics of spatial-temporal resolution, fast response, high sensitivity, self-calibration and optical accessibility. Accuracy of temperature measurement using tunable diode laser absorption spectroscopy was improved by applying the corrected spectroscopic database. Computed tomography reconstruction accuracy of 16 laser-paths configuration was evaluated using sum of squared difference (0.001) and zero-mean normalized cross-correlation (over 0.991), which presented the consistent temperature between assumed and reconstructed distributions. This developed computed tomography-tunable diode laser absorption spectroscopy was successfully applied to pulverized coal flame for two dimensional temperature measurement with 1 ms temporal resolution for time-series two dimensional temperature measurement in the range of 300K-2500K. The rationality was demonstrated by comparison of pulverized coal flame and Methane-Air flame temperature distributions due to the main heat release produced by methane fuel. Its applicability to pulverized coal combustion field will be benefit for optimal operation control and combustion efficiency improvement by combustion organization or new design of combustion system.
关键词： Power plant,Pulverized coal combustion,Computed tomography (CT),Tunable diode laser absorption spectroscopy (TDLAS),Two dimensional temperature measurement
更新于2025-09-23 15:21:01
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Strongly Coupled Coherent Phonons in Single-Layer MoS <sub/>2</sub>
摘要： We present a transient absorption setup combining broadband detection over the visible-UV range with high temporal resolution (～20fs) which is ideally suited to trigger and detect vibrational coherences in different classes of materials. We generate and detect coherent phonons (CPs) in single layer (1L) MoS2, as a representative semiconducting 1L-Transition Metal Dichalcogenide (TMD), where the confined dynamical interaction between excitons and phonons is unexplored. The coherent oscillatory motion of the out-of-plane A'1 phonons, triggered by the ultrashort laser pulses, dynamically modulates the excitonic resonances on a timescale of few tens fs. We observe an enhancement by almost two orders of magnitude of the CP amplitude when detected in resonance with the C exciton peak, combined with a resonant enhancement of CP generation efficiency. Ab Initio calculations of the change in 1L-MoS2 band structure induced by the A'1 phonon displacement confirm a strong coupling with the C exciton. The resonant behavior of the CP amplitude follows the same spectral profile of the calculated Raman susceptibility tensor. These results explain the CP generation process in 1L-TMDs and demonstrates that CP excitation in 1L-MoS2 can be described as a Raman-like scattering process.
关键词： exciton-phonon interaction,Coherent phonons,transient absorption spectroscopy,transition metal dichalcogenides,ab-initio calculation
更新于2025-09-23 15:21:01
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Strong pH-Dependent Near-Infrared Fluorescence in a Microbial Rhodopsin Reconstituted with a Red-Shifting Retinal Analogue
摘要： Near-infrared (NIR)-driven rhodopsins are of great interest in optogenetics and other optobiotechnological developments such as artificial photosynthesis and deep-tissue voltage imaging. Here we report the proton pump proteorhodopsin (PR) containing a NIR-active retinal analogue (PR:MMAR) exhibits intense NIR fluorescence at a quantum yield of 3.3%. This is 130 times higher than native PR (Lenz, M. O.; et al. Biophys J. 2006, 91, 255?262) and 3?8 times higher than the QuasAr and PROPS voltage sensors (Kralj, J.; et al. Science 2011, 333, 345?348; Hochbaum, D. R.; et al. Nat. Methods 2014, 11, 825?833). The NIR fluorescence strongly depends on the pH in the range of 6?8.5, suggesting potential application of MMAR-binding proteins as ultrasensitive NIR-driven pH and/or voltage sensors. Femtosecond transient absorption spectroscopy showed that upon near-IR excitation, PR:MMAR features an unusually long fluorescence lifetime of 310 ps and the absence of isomerized photoproducts, consistent with the high fluorescence quantum yield. Stimulated Raman analysis indicates that the NIR-absorbing species develops upon protonation of a conserved aspartate, which promotes charge delocalization and bond length leveling due to an additional methylamino group in MMAR, in essence providing a secondary protonated Schiff base. This results in much smaller bond length alteration along the conjugated backbone, thereby conferring significant single-bond character to the C13C14 bond and structural deformation of the chromophore, which interferes with photoinduced isomerization and extends the lifetime for fluorescence. Hence, our studies allow for a molecular understanding of the relation between absorption/emission wavelength, isomerization, and fluorescence in PR:MMAR. As acidification enhances the resonance state, this explains the strong pH dependence of the NIR emission.
关键词： stimulated Raman analysis,fluorescence,voltage sensor,rhodopsins,optogenetics,artificial photosynthesis,proteorhodopsin,femtosecond transient absorption spectroscopy,pH sensor,Near-infrared,voltage imaging
更新于2025-09-23 15:21:01
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Attosecond transient-absorption spectroscopy of polar molecules
摘要： We apply attosecond transient absorption spectroscopy (ATAS) to explore the effects of a nonzero permanent dipole on electron dynamics at the subfemtosecond scale, exemplified in the polar LiF molecule. In contrast with nonpolar systems, a familiar feature of the ATA spectra—the light-induced structures—are observed adjacent to a bright state. Moreover, a previously unobserved ladder structure is identified. The observations are analyzed in the context of a model based on fixed-nuclei adiabatic states, supported by full numerical simulations. Analytic calculations originating in the adiabatic model shed light on the nature and origins of the findings.
关键词： LiF molecule,attosecond transient absorption spectroscopy,electron dynamics,polar molecules,ladder structure,light-induced structures
更新于2025-09-23 15:21:01
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EXPRESS: Influence of Line Pair Selection on Flame Tomography Using Infrared Absorption Spectroscopy
摘要： We report the influence of absorption line selection on the tomographic results for high-temperature flames by numerical and experimental methods. Different combinations of infrared H2O absorption transitions are utilized with the Tikhonov-regularized Abel inversion to reconstruct the radial distribution of temperature and H2O concentration in a flat flame. It is shown that besides using the mathematical algorithm such as regularization, selecting a line pair with a large ΔE″ (> 1390 cm–1) also reduces the reconstruction uncertainty at 300–2000 K. In this study, a proper selection of absorption line pairs reduces the reconstruction uncertainty by 25% at the same level of noise. The line pair of H2O transitions at 4029.524 cm–1 and 4030.729 cm–1 is recommended for the tomography of high-temperature flames at 1000–3000 K, whereas the line pair of 7185.597 cm–1 and 7444.352 cm–1 can be used at 300–1000 K.
关键词： tunable diode laser absorption spectroscopy,TDLAS,Tomography,high-temperature flame,line selection
更新于2025-09-23 15:21:01
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Time-resolved Element-selective Probing of Charge Carriers in Solar Materials
摘要： We review our recent results on the implementation of picosecond (ps) X-ray absorption spectroscopy to probe the electronic and geometric structure of centres formed by photoexcitation of solar materials such as polymorphs and inorganic Cs-based perovskites. The results show electron localization at Ti defects in TiO2 anatase and rutile and small hole polaron formation in the valence band of CsPbBr3, all within 80 ps. This method is promising for the study of the ultrafast time scales of such processes, especially with the advent of the Swiss X-ray Free Electron Laser (SwissFEL).
关键词： Solar materials,Ultrafast,Perovskites,X-ray absorption spectroscopy,TiO2
更新于2025-09-23 15:21:01
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Experimental observation of the vibration-rotation radiation curves of <sup>12</sup> C <sup>16</sup> O <sub/>2</sub> and <sup>13</sup> C <sup>16</sup> O <sub/>2</sub> absorption constants ranging from 4860 to 4880 sm <sup>a??1</sup> by the tunable diode laser absorption spectroscopy method
摘要： We report the experimental observation of the absorption constant values of 12C16O2 and 13C16O2 using the tunable diode laser absorption spectroscopy method ranging from 4860 to 4880 sm?1 within the pressure limits of 8–240 mbar for the absorption curves (lines) R(18), R(20), R(22), R(24), R(26), R(28), R(30), R(32), R(34) and R(36) of the 20013–00001 molecule 12C16O2 vibration band, and within the pressure limits of 0.06–1.7 mbar for the absorption curves P(10), P(12), P(14), P(16), P(18), P(20) and P(22) of the 20012–00001 molecule 13C16O2 vibration band. In the work, as a mixture under analysis, a mixture of the isotopes 13C16O2 and 12C16O2 at the ratio of 1:140 was used. The results have been compared with the data of the HITRAN spectroscopic database.
关键词： tunable diode laser absorption spectroscopy,carbon dioxide,absorption coefficients
更新于2025-09-23 15:19:57
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Absolute density measurement of hydrogen atom in inductively coupled Ar/H2 plasmas using vacuum ultraviolet absorption spectroscopy
摘要： The absolute density measurement of atomic species such as hydrogen is crucial for plasma processing because of their strong chemical reactivity. In this work, to measure the hydrogen atom density in Ar/H2 inductively coupled plasmas (ICP), the self-absorption-applied vacuum ultraviolet absorption spectroscopy (VUVAS) is studied with a micro-hollow cathode H2/He discharge lamp (MHCL) emitting VUV light (Lyman alpha line; Lα 121.56 nm). The absolute density of hydrogen atoms in the ICP is investigated for various powers (50 W–850 W) in the low pressure region (30 mTorr–50 mTorr). The hydrogen density in remote plasma region is shown to vary from 2.1 × 1011 cm?3 to 1.25 × 1012 cm?3 with respect to plasma power.
关键词： VUV absorption spectroscopy,Low-pressure,Self-absorption,Hydrogen atom density,inductively coupled plasma
更新于2025-09-23 15:19:57