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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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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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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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Fast discrimination of bacteria using a filter paper–based SERS platform and PLS-DA with uncertainty estimation
摘要： Rapid and reliable identification of bacteria is an important issue in food, medical, forensic, and environmental sciences; however, conventional procedures are time-consuming and often require extensive financial and human resources. Herein, we present a label-free method for bacterial discrimination using surface-enhanced Raman spectroscopy (SERS) and partial least squares discriminant analysis (PLS-DA). Filter paper decorated with gold nanoparticles was fabricated by the dip-coating method and it was utilized as a flexible and highly efficient SERS substrate. Suspensions of bacterial samples from three genera and six species were directly deposited on the filter paper–based SERS substrates before measurements. PLS-DA was successfully employed as a multivariate supervised model to classify and identify bacteria with efficiency, sensitivity, and specificity rates of 100% for all test samples. Variable importance in projection was associated with the presence/absence of some purine metabolites, whereas confidence intervals for each sample in the PLS-DA model were calculated using a resampling bootstrap procedure. Additionally, a potential new species of bacteria was analyzed by the proposed method and the result was in agreement with that obtained via 16S rRNA gene sequence analysis, thereby indicating that the SERS/PLS-DA approach has the potential to be a valuable tool for the discovery of novel bacteria.
关键词： Chemometrics, partial least squares discriminant analysis,Surface-enhanced Raman spectroscopy,Reliability estimation,16S rRNA gene sequence analysis,Gold nanoparticles
更新于2025-09-04 15:30:14
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Integrated spectral and spatial information extraction in Raman spectroscopy
摘要： Raman spectroscopy has been widely used to analyze various substances quantitatively. Conventional studies are primarily focused on the spectral characteristics of Raman scattering. The spatial distribution is always ignored, which can be used to observe the physical properties, such as the particle size. In this article, the spatial information has been extracted from the Raman spectra of barium nitrate, demonstrating that the evident spatial width broadening varied with the particle size. The numerical result shows that the spatial width has a better linear correlation with the particle size, while the Raman intensity has a poor linear correlation. The integrated spectral and spatial information extracted in Raman spectroscopy has a potential application in the quantitative analysis of physical properties.
关键词： spatial distribution,Raman spectroscopy,Particle size
更新于2025-09-04 15:30:14
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Structural, Linear and Third Order Nonlinear Optical Properties of Sol-Gel Grown Ag-CdS Nanocrystalline Thin Films
摘要： Pure and Ag doped CdS nanocrystalline ?lms with different Ag doping concentrations were successfully grown on glass substrates by a sol-gel spin coating method. Ag doping was performed using silver acetate aqueous solution with 0.01, 0.02 and 0.03 M concentrations via ion exchange. The in?uences of Ag doping on structural, vibrational, morphological, linear and third order nonlinear optical properties of CdS nanocrystalline ?lms were studied. The x-ray diffraction patterns of the ?lms exhibited a broad peak centered at an angle 2h = 26.5(cid:2) along the (111) plane, which con?rms the cubic structure and formation of nanocrystalline ?lms. Raman spectra of ?lms demonstrate a shift in longitudinal optical phonon vibrations as compared to the bulk counterpart. Pure CdS ?lm shows high transmittance (83%) in the visible and near infrared (NIR) regions. With Ag doping, a signi?cant red shift in the band edge and reduction in the transmittance of the ?lms in visible and NIR regions were observed. However, the ?lms doped with Ag showed appreciable transmittance in visible region for window layer applications. A signi?cant effect on optical parameters such as absorption index, refractive index, and optical dielectric constant was observed after Ag doping. The nonlinear optical properties of ?lms were enhanced with incorporation of Ag atoms into the CdS binary system. The values of nonlinear optical susceptibility v(3) and refractive index n2 were found to increase with increasing Ag concentration and were estimated to be in the range of 2.92 9 10(cid:2)10 (cid:2) 1910(cid:2)7 esu and 1.00 9 10(cid:2)9 2.00 9 10(cid:2)7 esu, respectively. These values suggest that these ?lms can be potential candidates for nonlinear optical device applications.
关键词： structural properties,optical properties,surface morphology,Ag-CdS,Raman spectroscopy
更新于2025-09-04 15:30:14
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Corrosion Inhibition of Aluminium Alloy AA6063-T5 by Vanadates: Local Surface Chemical Events Elucidated by Confocal Raman Micro-Spectroscopy
摘要： Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V+4 and V+5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V+5 species are first reduced to V+4 or V+3 species above cathodic IMPs, and then oxidized to mixed-valence V+5/V+4 polymerized compounds.
关键词： B. XPS,B. Raman Spectroscopy,C. Vanadate Inhibitor,A. Aluminium,B. SEM,A. Alloy
更新于2025-09-04 15:30:14
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Label-free characterization of exosome via surface enhanced Raman spectroscopy for the early detection of pancreatic Cancer
摘要： Pancreatic cancer is a highly lethal malignancy. Lack of early diagnostic markers makes timely detection of pancreatic cancer a highly challenging endeavor. Exosomes have emerged as information-rich cancer specific biomarkers. However, characterization of tumor-specific exosomes has been challenging. This study investigated the proof-of principal that exosomes could be used for the detection of pancreatic cancer. Label-free analysis of exosomes purified from normal and pancreatic cancer cell lines was performed using surface enhanced Raman Spectroscopy (SERS) and principal component differential function analysis (PC-DFA), to identify tumor-specific spectral signatures. This method differentiated exosomes originating from pancreatic cancer or normal pancreatic epithelial cell lines with 90% accuracy. The cell line trained PC-DFA algorithm was next applied to SERS spectra of serum-purified exosomes. This method exhibited up to 87% and 90% predictive accuracy for HC and EPC individual samples, respectively. Overall, our study identify utility of SERS spectral signature for deciphering exosomal surface signature.
关键词： surface enhanced Raman spectroscopy,liquid biopsy,Pancreatic cancer,exosome,label-free
更新于2025-09-04 15:30:14
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Incipient Anion Intercalation of HOPG Close to the Oxygen Evolution Potential. A Combined X-ray Photoemission and Raman Spectroscopy Study
摘要： In the present work we used two different electrochemical (EC) techniques, namely cyclic voltammetry (CV) and normal pulsed voltammetry (NPV), applied to a highly oriented pyrolytic graphite (HOPG) electrode for anion intercalation in two different aqueous electrolytes (i.e. perchloric and sulphuric acid). We performed comparative X-ray photoemission (XPS) and Raman spectroscopy studies at various EC potentials. The chemical analysis obtained by XPS and Raman, the latter applied in-situ and in real-time during the electrochemical processes, indicates that at oxygen evolution potential (i.e. before reaching the well-known intercalation stage potentials) the HOPG intercalation process is already active. These results suggest that the intercalated compound is efficiently obtained before reaching higher potentials, which usually cause a detriment of the graphite crystal.
关键词： HOPG,Raman spectroscopy,X-ray photoemission,anion intercalation,normal pulsed voltammetry,cyclic voltammetry
更新于2025-09-04 15:30:14