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- 实验方案
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Residual stress in underlying silicon at the fixed end of SiO <sub/>2</sub> microcantilevers?— A micro-Raman study
摘要： In this work, nature of the residual stress developed in the convex corners created in underlying Si at the fixed end of SiO2 microcantilevers (MCs) fabricated by wet chemical etching method was investigated using micro-Raman spectroscopy with visible excitation. It revealed the presence of tensile stress near the sharp edge of the convex corner and is attributed to the localized stress generated in the neighborhood of the discontinuities, acting as stress concentration region. Residual stress estimated by micro-Raman technique across the convex corner was also validated by FEM simulations. Micro-Raman also revealed the presence of tensile stress on the etched Si surface, which is explained on the basis of stress induced by native oxide shells covering the etched features.
关键词： SiO2 microcantilever,convex corner in Si,micro-Raman spectroscopy using visible excitation,residual stress
更新于2025-09-04 15:30:14
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Cavity-enhanced absorption sensor for carbon monoxide in a rapid compression machine
摘要： A sensor based on cavity-enhanced absorption spectroscopy (CEAS) was implemented for the first time in a rapid compression machine (RCM) for carbon monoxide concentration measurements. The sensor consisted of a pulsed quantum cascade laser (QCL) coupled to a low-finesse cavity in the RCM using an off-axis alignment. The QCL was tuned near 4.89 μm to probe the P(23) ro-vibrational line of CO. The pulsed mode operation resulted in rapid frequency down-chirp (6.52 cm ?1 / μs) within the pulse as well as a high time resolution (10 μs). The combination of rapid frequency down-chirp and off-axis cavity alignment enabled a near complete suppression of the cavity coupling noise. A CEAS gain factor of 133 was demonstrated in experiments, resulting in a much lower noise-equivalent detection limit than a single-pass arrangement. The sensor thus presents many opportunities for measuring CO formation at low temperatures and for studying kinetics using dilute reactive environments; one such application is demonstrated in this work using dilute n-heptane/air mixtures in the RCM. The formation of CO during first-stage ignition of n-heptane was measured over 802–899 K at a nominal pressure of 10 bar. These conditions correspond to the NTC region of n-heptane and such results provide useful metrics to test and compare the predictions of low-temperature heat release by different kinetic models.
关键词： n-heptane,Low-temperature heat release,Cavity-enhanced absorption spectroscopy,Rapid compression machine,Carbon monoxide
更新于2025-09-04 15:30:14
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Rapid determination of phytosterols by NIRS and chemometric methods
摘要： Phytosterols have been extensively studied because it plays essential roles in the physiology of plants and can be used as nutritional supplement to promote human health. We use a rapid method by coupling near-infrared spectroscopy (NIRS) and chemometric techniques to quickly and efficiently determine three essential phytosterols (β-sitosterol, campesterol and stigmasterol) in vegetable oils. Continuous wavelet transform (CWT) method was adopted to remove the baseline shift in the spectra. The quantitative analysis models were constructed by partial least squares (PLS) regression and randomization test (RT) method was used to further improve the models. The optimized models were used to calculate the phytosterol contents in prediction set in order to evaluate their predictability. We have found that the phytosterol contents by the optimized models and Gas Chromatography/Mass Spectrometry (GC/MS) analysis are almost consistent. The root mean square error of prediction (RMSEP) and ratio of prediction to deviation (RPD) for the three phytosterols are 525.7590, 212.2245, 65.1611 and 4.0060, 4.7195 and 3.5441, respectively. The results have proved the feasibility of the proposed method for rapid and non-destructive analysis of phytosterols in edible oils.
关键词： phytosterol,vegetable oil,near-infrared spectroscopy,partial least squares,wavelength selection
更新于2025-09-04 15:30:14
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Micro-Raman Spectroscopy in Self-Catalyzed Indium Phosphide Nanostructures: Morphology and Substrate Effects
摘要： We report the effect of morphology and substrate of self-catalyzed indium phosphide (InP) nanostructures on phonon vibration modes. Using liquid indium as a catalyst, we grew self-catalyzed InP nanocones and nanopillars on single crystal substrates of InP(111)B, Si(111), and Si(100) via metal-organic chemical vapor epitaxy. Due to crystal symmetry breaking in one-dimensional nanostructure, longitudinal-optical (LO) and transverse-optical (TO) phonon modes are clearly resolved with the strong anisotropic behavior. Broadening and downshift of LO phonon modes are found to be sensitive to the morphology (i.e., aspect ratio and surface-to-volume ratio) and crystal structure (i.e., Wurtzite and Zinc Blende) of the as-grown nanostructures. This work demonstrated that Raman spectroscopy provides statistical insights on the quality of as-grown nanostructures (i.e., growth orientation, crystal structures, and the presence of structural defects) without destroying samples.
关键词： VLS Process,MOVPE,InP Nanowire,Raman Spectroscopy,Self-Catalyst
更新于2025-09-04 15:30:14
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Upconversion Properties of BaY2(MoO4)4:Er3+/Yb3+ Green Phosphors Synthesized via Cyclic Microwave-Modified Sol-Gel Route
摘要： The double molybdate BaY2(MoO4)4:Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (Er3+ = 0.05, 0.1, 0.2 and Yb3+ = 0.2, 0.45) have been successfully synthesized by a cyclic microwave-modified sol-gel process and their upconversion properties have been investigated. Well-crystallized particles were formed after heat treatment at 900 °C for 12 h, showing a fine and homogeneous morphology. Under excitation at 980 nm, BaY2(MoO4)4:Er3+/Yb3+ particles exhibited a strong 525 nm emission band and a weak 550 nm emission band in the green region and a very weak 655 nm emission band in the red region. The Raman spectra of the particles indicated the strong peaks at higher frequencies and weak peaks at lower frequencies.
关键词： Raman Spectroscopy,Upconversion properties,Green phosphors,Microwave-modified sol-gel
更新于2025-09-04 15:30:14
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Crystallographic, optical, and electronic properties of (Cu, Li)GaS2
摘要： We synthesized chalcopyrite-type (Cu1-xLix)GaS2 solid solution samples with a composition of 0.00 ≤ x ≤ 0.20 by mechanochemical process and sequential heating at 550oC in 5% H2S/N2 gas atmosphere. The X-ray powder diffraction (XRD) peaks of (Cu1-xLix)GaS2 shifted by substitution of Li atoms for Cu atoms in CuGaS2. Their crystallographic parameters were refined by Rietveld analysis using XRD data. The lattice constant a of the (Cu1-xLix)GaS2 solid solution increased with increasing Li content, x, while the lattice constant c decreased with increasing Li content, x. We determined band-gap energies of (Cu1-xLix)GaS2 solid solution by diffuse reflectance spectra. The band-gap energy of the (Cu1-xLix)GaS2 solid solution increased from 2.44 eV of CuGaS2 (x = 0.0) to 2.54 eV of (Cu0.8Li0.2)GaS2 (x = 0.2). To understand the band diagram of (Cu1-xLix)GaS2 solid solution, the energy level of the valence band maximum (VBM) was estimated from the ionization energy, which was measured by photoemission yield spectroscopy. The energy level of the conduction band minimum (CBM) was also determined by adding the band-gap energy to the VBM level. The VBM level of the (Cu1-xLix)GaS2 solid solution decreased with increasing Li content, x. On the other hand, the CBM level was approximately constant. Li-doping in CuGaS2 is effective for decreasing the VBM level without increasing the CBM level.
关键词： Mechanochemical process,Band-gap energy,(Cu1-xLix)GaS2,Chalcopyrite-type,Photoemission yield spectroscopy
更新于2025-09-04 15:30:14
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Simultaneous determination of furosemide and spironolactone in pharmaceutical formulations by spectrophotometric method using principal component regression
摘要： The combination of furosemide (furo) and spironolactone (spiro) is very effective in the treatment of heart failure. In that case, maintaining good quality of these drugs in commercial tablets is must. Therefore, a simple, economical, precise and accurate method, i.e; chemometric assisted UV spectroscopy, for simultaneous determination of furosemide and spironolactone in combined dosage form has been developed. In this study, principal component regression (PCR) has been reported for this purpose. A calibration set of 36 mixture solutions containing furosemide and spironolactone in methanol in the concentration range of 2.0-12.0 μg/ml and 5.0-30.0 μg/ml respectively has been prepared by means of an orthogonal experimental design. The absorbance data for the concentration set have been obtained by direct measurement in UV spectrophotometer at 101 wavelength points in the spectral region of 200-300 nm for the zero order spectra. The chemometric technique is also successfully applied to available pharmaceutical formulations, tablets, with no interference from excipients. The analytical performances of principal component regression are characterized by relative prediction errors and recoveries (%). The good recoveries obtained in this case proved that the proposed chemometric technique could be applied efficiently in the quality control of the studied drugs simultaneously in their mixture as well as in the commercial dosage form with satisfactory precision and accuracy as alternative analysis tools.
关键词： Spironolactone,Principal component regression,UV spectroscopy,Chemometric,Furosemide
更新于2025-09-04 15:30:14
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Electrochromic effect of indium tin oxide in lithium iron phosphate battery cathodes for state of charge determination
摘要： In this paper, we discuss the origin of an optical effect in lithium iron phosphate (LFP) battery cathodes, which depends on the electrical charge transferred into the battery. Utilizing indium tin oxide (ITO) as an electrode additive, we were able to observe a change in reflectivity of the cathode during charging and discharging with lithiation and delithiation being clearly visible in the form of lithiation fronts. Further investigations using in situ video microscopy and in situ Raman spectroscopy on test cells with an optical window indicates that ITO additionally acts as an electrochromic marker within the LFP cathode. This enhances the optical effect due to local potentials around the lithiation fronts, which enables the voltage-dependent reflectivity of the ITO to be visible in the LFP cathode. Structural analysis with scanning electron microscopy (SEM) and X-ray crystallography (XRD) are presented as well. The observed effect allows for novel battery research methods and for a possible commercial application as a sensor for state of charge (SOC) estimation similar to the optical fiber approach reported by Ghannoum et al. for a graphite anode.
关键词： lithium ion batteries,battery state determination,lithium iron phosphate,raman spectroscopy,indium tin oxide,electrochromic marker,video microscopy,state of charge
更新于2025-09-04 15:30:14
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<i>In Situ</i> IR Spectroscopy of Mesoporous Silica Films for Monitoring Adsorption Processes and Trace Analysis
摘要： Adsorption of molecules on high-surface-area materials is a fundamental process critical to many fields of basic and applied chemical research; for instance, it is among the simplest and most efficient principles for separating and remediating polluted water. However, established experimental approaches for investigating this fundamental process preclude in situ monitoring and thus obtaining real-time information about the ongoing processes. In this work, mid-infrared attenuated total reflection (ATR) spectroscopy is introduced as a powerful technique for quantitative in situ monitoring of adsorption processes and thus enrichment of traces of organic pollutants from aqueous solution in ordered mesoporous silica films. The synthesis, functionalization, and characterization of two silica films with 3D hexagonal and cubic pore structure on silicon ATR crystals are presented. Benzonitrile and valeronitrile as model compounds for aromatic and aliphatic water pollutants are enriched in hydrophobic films, while the matrix, water, is excluded from the volume probed by the evanescent field. Enrichment times of <5 s are observed during in situ measurements of benzonitrile adsorbing onto the film from aqueous solution. The sensing system is calibrated using the Freundlich adsorption equation as a calibration function. Enrichment factors of benzonitrile and valeronitrile within the film were determined to be >200 and >100, respectively, yielding detection limits in the low ppm range. Furthermore, fast and complete desorption of the analyte, ensuring reliable regeneration of the sensor, was verified. Lastly, we derive and experimentally validate equations for ATR spectroscopy with thin film adsorption layers to quantify the absolute mass of adsorbed pollutant in the film. The excellent agreement between recorded absorptions at target wavenumbers of the target analytes and corresponding simulations corroborates the validity of the chosen approach.
关键词： infrared spectroscopy,functional coatings,sensor,porous materials,thin film
更新于2025-09-04 15:30:14
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Recent Progress and Developments in Imaging Spectroscopy
摘要： The Special Issue (SI) on “Recent Progress and Developments in Imaging Spectroscopy” is a collection of contributions presented at the 10th Workshop of the European Association of Remote Sensing Laboratories (EARSeL) Special Interest Group on Imaging Spectroscopy (SIG IS), which took place at the University of Zurich, Zurich, Switzerland, between 19 and 21 April 2017. Moreover, the SI was equally open to the global research community actively involved in imaging spectroscopy. EARSeL’s Special Interest Group on Imaging Spectroscopy aims at encouraging interdisciplinary discussions among specialists working with innovative Earth observation methods and technologies. With its 10th workshop in April 2017, the EARSeL SIG IS workshop series celebrated its 20th anniversary, building on the legacy of nine successful previous workshops, whereas the ?rst one took place at the University of Zurich back in 1998.
关键词： Remote Sensing,Imaging Spectroscopy,Earth Observation,EARSeL SIG IS
更新于2025-09-04 15:30:14