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Recent Trends in Compressive Raman Spectroscopy Using DMD-Based Binary Detection
摘要： The collection of high-dimensional hyperspectral data is often the slowest step in the process of hyperspectral Raman imaging. With the conventional array-based Raman spectroscopy acquiring of chemical images could take hours to even days. To increase the Raman collection speeds, a number of compressive detection (CD) strategies, which simultaneously sense and compress the spectral signal, have recently been demonstrated. As opposed to conventional hyperspectral imaging, where full spectra are measured prior to post-processing and imaging CD increases the speed of data collection by making measurements in a low-dimensional space containing only the information of interest, thus enabling real-time imaging. The use of single channel detectors gives the key advantage to CD strategy using optical filter functions to obtain component intensities. In other words, the filter functions are simply the optimized patterns of wavelength combinations characteristic of component in the sample, and the intensity transmitted through each filter represents a direct measure of the associated score values. Essentially, compressive hyperspectral images consist of 'score' pixels (instead of 'spectral' pixels). This paper presents an overview of recent advances in compressive Raman detection designs and performance validations using a DMD based binary detection strategy.
关键词： Chemometrics,multivariate data analysis,digital light processor (DLP),digital micromirror device (DMD),optimal binary filters,spatial light modulators (SLM),Raman spectroscopy,chemical imaging,compressive detection
更新于2025-09-23 15:22:29
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Photochromic properties in silver-doped titania nanoparticles
摘要： The Ag-doped TiO2 nanoparticles were synthesized at room temperature using a solution of titanium isopropoxide and silver nitrate as precursors. The inclusion of Ag in the nanocrystalline TiO2 lattice was systematically analyzed both from a morphological and a structural point of view. Raman spectroscopy, electron microscopy, electronic diffraction and x-rays allow us to testify that the dopant Ag does not modify the nanocrystalline anatase tetragonal structure of the nanoparticles, but causes a small distortion of the structure. UV–vis spectroscopy allowed to analyze the optical properties of the obtained nanoparticles. Kubelka Munk’s model allowed the interpretation of diffuse reflectance spectra. We have obtained a very different system from the hetero-system Ag-TiO2 described in the literature, but it shows an interesting photochromic behaviour. Ag-doped TiO2 nanoparticles darken and whiten under UV light and visible light, respectively, in a very fast way. A simple kinetic model has been used to process experimental data and describe the observed photochromic process and to determine the darkening and whitening constants.
关键词： photochromism,electron diffraction,nanoparticles,optical properties,Raman spectroscopy
更新于2025-09-23 15:22:29
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Temperature Dependent Electrical Transport Properties of High Carrier Mobility Reduced Graphene Oxide Thin Film Devices
摘要： We confirm variable electrical transport properties of high mobility reduced graphene oxide (RGO) thin films fabricated by pulse laser deposition. The temperature dependent (5K–350K) four terminal electrical transport property measurements range hopping and thermally activated transport mechanism of the charge carriers at low (5K–210K) and high temperature (210K–350K) regions, respectively. The calculated localization length, the density of states near the Fermi level (EF), hopping energy, and Arrhenius energy gap provide useful information to explain the excellent electrical properties of the RGO films. Hall mobility measurement confirms p-type characteristics of the thin films. The charge carrier Hall mobility can be engineered by tuning the growth parameters, and the measured maximum mobility was 1596 cm2v-1s-1. The optimization of the improved electrical property is well supported by structural properties such as the defect density, average size of sp2 clusters and degree of reduction, which were investigated by Raman spectroscopy and X-ray diffraction analysis.
关键词： PLD,variable range hopping,and Raman spectroscopy,hall mobility,Reduced graphene oxide,localization length
更新于2025-09-23 15:22:29
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Time-order Phonon Scattering Processes are Responsible for the Asymmetric G* Raman Band in Graphene
摘要： Background: While most of the prominent features in the Raman spectrum of graphene are well understood as mentioned in patents within the Double Resonance (DR) picture, the origin of the peak at 2450 cm-1 (also called the G* band) still remains unclear. Method and Objective: In this work, we performed detailed Raman studies of single- and few-layer graphene using multiple laser excitations to unravel the origin of G* band. Results: Based on our analyses, we conclude that the G* band arises from a combination of Transverse Optical (iTO) and Longitudinal Acoustic (LA) phonons, and exhibits an asymmetric peak structure due to the presence of two different time-order phonon processes. The lower (higher) frequency sub-peak is ascribed to an LA-first (iTO-first) process. We provide three strong experimental evidences for the time-ordered scattering processes: the dependence of the G* band sub-peaks with (i) increasing laser energy, (ii) increasing defects, and (iii) increasing temperature. Finally, we attribute the enhanced asymmetry of the G* band in multi-layer graphene to multiple processes between electronic sub-bands, similar to the G’ band in multi-layer graphene. Conclusion: Our study uncovered the origin and nature of the G* peak in the Raman spectrum of graphene. We believe our results have important implications for processes such as graphene-enhanced Raman scattering, where the time-ordered scattering of optical and acoustic phonons can be very useful for sensing analytes.
关键词： second order,layer stacking,G* band,defects,graphene,Raman spectroscopy
更新于2025-09-23 15:22:29
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A Rapid and Sensitive Quantitative Analysis Method for TNT using Raman Spectroscopy
摘要： Raman spectroscopy as a rapid and sensitive qualitative detection method has been applied in many fields; however, it is rarely used for the quantitative purpose due to poor reproducibility of peak area. Here, 2,4,6-trinitrotoluene (TNT) and its two byproducts, 2,4-dinitrotoluence (DNT) and 2,6-DNT, were firstly qualitatively analyzed by Raman spectroscopy and the characteristic parameters were extracted. Then, in the range of 2 %–9 % and 10 %–90 %, the standard curves were established between the area ratio of the characteristic peaks and the content of 2,4-DNT or 2,6-DNT using silver nanoflowers as the enhancing substrate. The fitting correlation for TNT/2,4-DNT or TNT/2,6-DNT system is around 0.99. The peak area ratio of the components exhibits much better data reproducibility than peak area, and the relative error does not exceed 9.3 % for at least six groups of parallel experiments.
关键词： TNT,Quantitative analysis,2,4-DNT,2,6-DNT,Raman spectroscopy
更新于2025-09-23 15:22:29
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Carbon Dots Dispersed on Graphene/SiO <sub/>2</sub> /Si: A Morphological Study
摘要： Low-dimensional carbon materials occupy a relevant role in the field of nanotechnology. Herein, the authors report a study conducted by atomic force microscopy and Raman spectroscopy on the deposition of carbon dots onto graphene surfaces. The study aims at understanding if and how the morphology and the microstructure of chemical vapor deposited graphene on Si/SiO2 may change due to the interaction with the carbon dots. Potential alteration in the graphene’s electrical properties might be detrimental for optoelectronic applications. The deposition of carbon dots dispersed in water and ethanol solvents are explored to investigate the effect of solvents with different fluidic properties. The obtained results indicate that the carbon dots do not alter the quality of graphene.
关键词： Raman spectroscopy,carbon dots,atomic force microscopy,chemical vapor deposited graphene
更新于2025-09-23 15:22:29
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Subsurface modification induced on ion-exchanged glass substrates by deposition and bombardment
摘要： Ion-exchanged glasses are widely used in optoelectronic devices due to its high strength and optical waveguide effects. The MgF2 films deposited on the ion-exchanged glasses and the ion-exchanged glasses bombarded by argon ions (100 eV) at 220 °C were investigated in the present work. The microstructure of MgF2 films and the structural and physico-chemical properties of the ion-exchanged glasses before and after deposition and bombardment were analyzed by grazing incident X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM), electron probe micro analysis (EPMA), micro-Raman spectroscopy and surface stress meter. It is shown that MgF2 films exhibit a polycrystalline and microcolumnar structure. The peak of potassium ions concentration distribution in the ion-exchanged glasses, accompanied by outward diffusion of potassium ions, decreases and moves from glass surface to the inner part to different degrees during deposition and bombardment. The potassium ions concentration in the region near the surface of argon ion-bombarded glasses is almost the same as the MgF2-coated glasses. Furthermore, the position and intensity of Raman bands in the subsurface region of the ion-exchanged glasses show obvious changes before and after deposition and bombardment. The values of compressive stress and depth of layer in the MgF2-coated ion-exchanged glasses and the argon ion-bombarded ion-exchanged glasses are far away lower than that of its values obtained in the ion-exchanged glasses. Overall results have shown that variations of chemical composition, Raman bands and surface compressive stress in the exchanged region indicate subsurface modification of the ion-exchanged glasses induced by deposition and bombardment, which provide useful information for the use of the ion-exchanged glasses in further.
关键词： Modification,Ion bombardment,Raman spectroscopy,Ion-exchanged glass,MgF2 thin film
更新于2025-09-23 15:22:29
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Surface-enhanced Raman scattering method for the identification of methicillin-resistant Staphylococcus aureus using positively charged silver nanoparticles
摘要： The article describes a SERS-based method for diagnosis of bacterial infections. Positively charged silver nanoparticles (AgNPs+) were employed for identification of methicillin-resistant Staphylococcus aureus (MRSA). It is found that AgNPs+ undergo self-assembly on the surface of bacteria via electrostatic aggregation. The assembled AgNPs+ are excellent SERS substrates. To prove the capability of SERS to differentiate between S. aureus and other microorganisms, six standard strains including S. aureus 29213, S. aureus 25923, C. albicans, B. cereus, E. coli, and P. aeruginosa were tested. To further demonstrate its applicability for the identification of MRSA in clinical samples, 52 methicillin-sensitive S. aureus (MSSA) isolates and 215 MRSA isolates were detected by SERS. The total measurement time (include incubation) is 45 min when using a 3 μL sample. The method gives a strongly enhanced Raman signal (at 730 cm?1 and 1325 cm?1) with good reproducibility and repeatability. It was successfully applied to the discrimination of the six strain microorganisms. The typical Raman peaks of S. aureus at 730, 1154, 1325, and 1457 cm?1 were observed, which were assigned to the bacterial cell wall components (730 cm?1- adenine, glycosidic ring mode, 1154 cm?1- unsaturated fatty acid, 1325 cm?1- adenine, polyadenine, and 1457 cm?1 for -COO- stretching). S. aureus was completely separated from other species by partial least squares discriminant analysis (PLS-DA). Moreover, 52 MSSA isolates and 215 MRSA isolates from clinical samples were identified by PLS-DA. The accuracy was almost 100% when compared to the standard broth microdilution method. A classification based on latent structure discriminant analysis provided spectral variability directly. Conceivably, the method offers a potent tool for the identification of bacteria and antibiotics resistance, and for studies on antibiotic-resistance in general.
关键词： S. aureus,Nanoparticles,Methicillin resistance,Antibiotics,Latent structure discriminant analysis classification (OPLS-DA),SERS,Partial least squares discriminant analysis (PLS-DA),AgNPs,Discriminant analysis,Raman spectroscopy
更新于2025-09-23 15:22:29
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Constituent substitution in hot wall deposition of Bi2S3 films by reaction with substrates
摘要： Replacement of a constituent in the overgrown layers with the materials provided by the substrates is investigated when Bi2S3 films are deposited on III-V compound semiconductors and transition metals using a hot wall epitaxy method. The substitution caused by the S atoms is stronger than that by the Se and Te atoms in deposition of Bi2Se3 and Bi2Te3 films. Mere exposure to Bi2S3 vapor of In-containing compounds (InP and InAs) and Ga-containing compounds (GaAs and GaSb) at epitaxial growth temperatures results in a capping of their surfaces by In2S3 and GaS, respectively. A temperature window is revealed to exist for the GaAs case where growth of Bi2S3 microcrystals occurs within the temperature range for the sulfide formation. The sulfurization by the material substitution is thus demonstrated to be not always identical with that using elemental sulphur. We examine furthermore the sulfides synthesized on the surfaces of Cu, Ag, Ni, Mo, and W. The sulfides produced on Cu and Ag undergo material alterations when they are irradiated by a laser light.
关键词： X-ray crystallography,Hot wall epitaxy,Material substitution,Raman spectroscopy,Bi2S3,Sulfides
更新于2025-09-23 15:22:29
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CVD diamond film detectors for α particles with a new electrode structure of reduced graphene oxide/Au
摘要： (111)-oriented poly-crystalline diamond ?lms (PCDs) have been deposited on Si substrates by MPCVD technology. The new electrode structure of reduced graphene oxide (RGO)/Au was successfully fabricated onto PCDs. Using the circular transmission line model (CTLM), the contact resistance of 6.6 Ω cm?2 was obtained for RGO/Au electrode on PCD surface, which was notably lower than that of 97.4 Ω cm?2 for Ti/Pt/Au electrode. Furthermore, two detectors with these two type electrodes were made respectively. The dark current, photocurrent and energy resolution of these two detectors under 5.5 MeV α particles irradiation from a 241Am source were observed. The results demonstrated that the fabrication of RGO/Au electrode onto PCD can realize a ?ne ohmic contact. The photocurrent of 58.7 nA for the detector with RGO/Au electrode had higher values than that of 8.8 nA for the detector with Ti/Pt/Au electrode at the bias voltage of 100 V respectively. Due to the realization of good contact on PCD surface with RGO/Au electrode, the energy resolution of 11.9% for the detector with RGO/Au electrode better than that of 24% for the detector with Ti/Pt/Au electrode can be obtained. Fabrication of the RGO/Au electrode on PCD may provide a feasible way to improve its detection performance under α particles irradiation.
关键词： α particle irradiation,Diamond ?lm,Ohmic contact,RGO/Au electrode,Raman spectroscopy
更新于2025-09-23 15:22:29