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The combination of Raman imaging and LIBS for quantification of original and degradation materials in Cultural Heritage
摘要： Quantification with nondestructive techniques is not very well developed in the field of Cultural Heritage despite its interest. In the last decades, several works have been published using Raman spectroscopy for quantifying. However, depending on the methodology used, the information provided by this technique is not complete, and the results could lead to misunderstanding when dealing with unknown samples. In this work, a novel double quantification using Raman imaging (its representativeness would be higher than point-by-point analysis) and Laser Induce Breakdown Spectroscopy (LIBS) analyses is presented for analysis of Cultural Heritage samples. Several dolomitic marble samples, with some calcite impurities, covered or not by a calcium oxalate (whewellite, CaC2O4·H2O) layer were analysed in order to optimize the novel methodology. The agreement between the quantitative results from the independent analyses of the Raman Image data and the LIBS data is consistent within the uncertainty arising from both techniques. Further, the same methodology was applied on the same samples but using point-by-point Raman analysis with portable instruments, and portable LIBS information, showing again a great agreement between them and with the results obtained using the laboratory instruments.
关键词： hydrated salts,quantification,Cultural Heritage,LIBS,Raman imaging
更新于2025-09-23 15:23:52
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Raman Spectroscopy and Microscopy Applications in Cardiovascular Diseases: From Molecules to Organs
摘要： Noninvasive and label-free vibrational spectroscopy and microscopy methods have shown great potential for clinical diagnosis applications. Raman spectroscopy is based on inelastic light scattering due to rotational and vibrational modes of molecular bonds. It has been shown that Raman spectra provide chemical signatures of changes in biological tissues in different diseases, and this technique can be employed in label-free monitoring and clinical diagnosis of several diseases, including cardiovascular studies. However, there are very few literature reviews available to summarize the state of art and future applications of Raman spectroscopy in cardiovascular diseases, particularly cardiac hypertrophy. In addition to conventional clinical approaches such as electrocardiography (ECG), echocardiogram (cardiac ultrasound), positron emission tomography (PET), cardiac computed tomography (CT), and single photon emission computed tomography (SPECT), applications of vibrational spectroscopy and microscopy will provide invaluable information useful for the prevention, diagnosis, and treatment of cardiovascular diseases. Various in vivo and ex vivo investigations can potentially be performed using Raman imaging to study and distinguish pathological and physiological cardiac hypertrophies and understand the mechanisms of other cardiac diseases. Here, we have reviewed the recent literature on Raman spectroscopy to study cardiovascular diseases covering investigations on the molecular, cellular, tissue, and organ level.
关键词： cardiovascular disease,cardiac hypertrophy,cardiac biomarkers,vibrational spectroscopy,Raman imaging
更新于2025-09-23 15:21:21
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Superficial-Layer-Enhanced Raman Scattering (SLERS) for Depth Detection of Noncontact Molecules
摘要： Although the strength of Raman signals can be increased by many orders of magnitude on noble metal nanoparticles, this enhancement is confined to an extremely short distance from the Raman-active surface. The key to the development of Raman spectroscopy for applications in diagnosis and detection of cancer and inflammatory diseases, and in pharmacology, relies on the capability of detecting analytes that are noninteractive with Raman-active surfaces. Here, a new Raman enhancement system is constructed, superficial-layer-enhanced Raman scattering (SLERS), by covering elongated tetrahexahedral gold nanoparticle arrays with a superficial perovskite (CH3NH3PbBr3) film. Plasmonic decay is depressed along the vertical direction away from the noble metal surface and the penetration depth is increased in the perovskite media. The vertical penetration of SLERS is verified by the spatial distribution of the analytes via Raman imaging in layer-scanning mode.
关键词： perovskites,self-assembly,Raman imaging,superficial-layer-enhanced Raman scattering
更新于2025-09-23 15:21:01
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Differential response of liver sinusoidal endothelial cells and hepatocytes to oleic and palmitic acid revealed by Raman and CARS imaging
摘要： Excess circulating fatty acids contribute to endothelial dysfunction that subsequently aggravates the metabolic conditions such as fatty liver diseases. However, the exact mechanism of this event is not fully understood, and the investigation on the effect of a direct exposure to fatty acids together with their subsequent fate is of interest. In this work we employed a chemically specific and label-free techniques such as Raman and CARS microscopies, to investigate the process of lipid droplets (LDs) formation in endothelial cells and hepatocytes after exposure to oleic and palmitic acid. We aimed to observe the changes in the composition of LDs associated with metabolism and degradation of lipids. We were able to characterize the diversity in the formation of LDs in endothelium as compared to hepatocytes, as well as the differences in the formation of LDs and degradation manner with respect to the used fatty acid. Thus, for the first time the spectral characteristics of LDs formed in endothelial cells after incubation with oleic and palmitic acid is presented, including the time-dependent changes in their chemical composition.
关键词： Liver sinusoidal endothelial cells,Oleic acid,CARS microscopy,Hepatocytes,Palmitic acid,Raman imaging
更新于2025-09-23 15:19:57
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Energy transport analysis in a Ga <sub/>0.84</sub> In <sub/>0.16</sub> N/GaN heterostructure using microscopic Raman images employing simultaneous coaxial irradiation of two lasers
摘要： Anisotropic heat transport in a Ga0.84In0.16N/GaN-heterostructure on a sapphire substrate is observed from microscopic Raman images obtained by utilizing coaxial irradiation of two laser beams, one for heating (325 nm) in the GaInN layer and the other for signal probing (325 nm or 532 nm). The increase in temperatures of the GaInN layer and the underlying GaN layer is probed by the 325-nm and 532-nm lasers, respectively, by analyzing the shift in the Raman peak energy of the higher energy branch of E2 modes. The result reveals that energy diffuses across a considerable length in the GaInN layer, whereas the energy transport in the perpendicular direction to the GaN layer is blocked in the vicinity of mis?t dislocations on the heterointerface. This simultaneous irradiation of two lasers for heat generation and probing is effective in the microscopic analysis of energy transport through heterointerfaces.
关键词： coaxial laser irradiation,heat transport,Raman imaging,GaInN/GaN heterostructure
更新于2025-09-23 15:19:57
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Anharmonic Effects in Single-Walled Carbon Nanotubes Analyzed through Low-Temperature Raman Imaging
摘要： The high thermal conductivity of single-walled carbon nanotubes (SWCNT) has gained much attention for their applications in potential thermal devices. Here, we investigate anharmonic effects, originated from phonon interactions, of SWCNT bundles by temperature dependent Raman imaging using our home-built mini cryostat system. The cryostat system is small enough to be mounted on a piezo scanner that suppresses thermal drift, enabling Raman imaging at different temperatures. We obtained Raman spectral images of several SWCNT bundles with a spatial resolution of a few hundred nanometers at different temperatures. We found that different bundles show different temperature dependences of Raman peak intensity, shift, and width. The temperature dependence was further elucidated by considering the sample topography observed by atomic force microscopy, where bundle effects seem to play an important role to influence the anharmonicity. The temperature-dependent Raman analysis based on spatially resolved imaging will be a powerful tool to investigate anharmonic effects of advanced carbon nanomaterials as well as to realize in-situ visualization of thermal properties for future thermal devices.
关键词： single-walled carbon nanotubes,anharmonic effects,low-temperature,Raman imaging,thermal properties
更新于2025-09-19 17:13:59
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Polarized Raman imaging of large area aligned semiconducting single‐walled carbon nanotubes
摘要： The current method of characterizing single-walled carbon nanotube (SWCNT) alignment utilizes single-point measurements of a few hundred square nanometers of polarized Raman spectroscopy to characterize an entire substrate of SWCNTs on the order of square centimeters. In this study, we demonstrate a new polarized Raman spectroscopy analyzation technique of orientation Raman imaging that images areas as large as 1 mm2. This provides a significantly more accurate representation of the spatial distribution in the alignment of any SWCNT film by increasing the measured area by 10 orders of magnitude over previous standard characterization techniques. Furthermore, this creates an “easy-to-see” visual representation of alignment based on optical anisotropy values. Improving the efficiency of characterizing alignment in SWCNT films via polarized Raman spectroscopy is an important step toward manufacturing scalable films of aligned SWCNTs.
关键词： polarized Raman imaging,polarized Raman spectroscopy,orientation image,carbon nanotube alignment,carbon nanotubes
更新于2025-09-12 10:27:22
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Efficient Exploration of the Composition Space in Ternary Organic Solar Cells by Combining High‐Throughput Material Libraries and Hyperspectral Imaging
摘要： Organic solar cells based on ternary active layers can lead to higher power conversion efficiencies than corresponding binaries, and improved stability. The parameter space for optimization of multicomponent systems is considerably more complex than that of binaries, due to both, a larger number of parameters (e.g., two relative compositions rather than one) and intricate morphology–property correlations. Most experimental reports to date reasonably limit themselves to a relatively narrow subset of compositions (e.g., the 1:1 donor/s:acceptor/s trajectory). This work advances a methodology that allows exploration of a large fraction of the ternary phase space employing only a few (<10) samples. Each sample is produced by a designed sequential deposition of the constituent inks, and results in compositions gradients with ≈5000 points/sample that cover about 15%–25% of the phase space. These effective ternary libraries are then colocally imaged by a combination of photovoltaic techniques (laser and white light photocurrent maps) and spectroscopic techniques (Raman, photoluminescence, absorption). The generality of the methodology is demonstrated by investigating three ternary systems, namely PBDB-T:ITIC:PC70BM, PTB7-Th:ITIC:PC70BM, and P3HT:O-IDFBR:O-IDTBR. Complex performance-structure landscapes through the ternary diagram as well as the emergence of several performance maxima are discovered.
关键词： high-throughput screening,layer-by-layer deposition,organic solar cells,ternaries,Raman imaging
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Live Multi-Color Coherent Raman Imaging Enabled by Millisecond Wavelength Tuning
摘要： We present multi-color coherent Raman imaging (CRI) with a frame rate of 8 Hz and rapid wavelength tuning within only 5 ms between successive images, enabled by a novel fiber optical parametric oscillator (FOPO). In CRI the limited tuning speed of conventional laser systems (>1 s) prevents the acquisition of successive images per second at more than one vibrational resonance and is considered as a bottleneck for multi-color assessments of medical specimen and rapidly evolving samples, such as living cells. Recent approaches to CRI with wavelength switching on a timescale of (sub-) milliseconds were based on two synchronized oscillators [1], being limited to two resonances, and parallel laser amplifiers [2] or spectral focusing techniques [3], both the latter with a limited tuning bandwidth of less than 300 cm-1. In contrast, the energy difference of the pump and Stokes pulses, emitted by the here presented FOPO, is tunable across the wide spectral range between 865 and 3050 cm-1 within only 5 ms. Assuming an equal time span for tuning and acquisition, up to 100 user-selectable vibrational components could be imaged per second, when imaging with 100 frame/s. The rapid tuning was achieved by a novel tuning concept for OPOs, based on the dispersive matching of the repetition frequency change of the pump pulses to the associated repetition frequency change of the resonant signal pulses in the FOPO. No alteration of the FOPO, e.g., via a mechanical delay line [4], was required for tuning the signal wavelength and the light source could be composed of all-spliced fiber components. Compared to previously presented FOPOs, the system runs at a high repetition rate of 40 MHz. The pump and Stokes pulses exhibit equal durations of 7 ps and an average power of 500 and 200 mW, respectively. As a first proof-of concept of the CRI capabilities, Fig. 1 shows three images of a sample consisting of water, oil and beads of PMMA and PS, taken successively with an acquisition time of 125 ms for each frame, limited only by the sampling rate of our detection setup. The energy difference was tuned in a frame-by-frame manner between 2850, 2950 and 3050 cm-1 in a time of 5 ms, a negligible time span compared to the acquisition time.
关键词： vibrational resonance,living cells,medical specimen,rapid wavelength tuning,fiber optical parametric oscillator,multi-color coherent Raman imaging
更新于2025-09-12 10:27:22
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A Fast Fluorescence Background Suppression Method for Raman Spectroscopy Based on Stepwise Spectral Reconstruction
摘要： Raman spectroscopy is a rapid and non-destructive technique for detecting unique spectral fingerprints from biological samples. Raw Raman spectra often come with strong fluorescence background, which makes spectral interpretation challenging. Although fluorescence background can be suppressed experimentally, this approach requires sophisticated and costly instruments. For convenience and cost-effectiveness, numerical methods have been used frequently to remove fluorescence background. Unfortunately, many of such methods suffer from long computation time. Therefore, a fast numerical method for fluorescence suppression is highly desirable especially in Raman spectroscopic imaging where Raman measurements from many pixels need to be processed rapidly. In response to this demand, we propose a fast numerical method for fluorescence background suppression based on the strategy of stepwise spectral reconstruction that we previously developed. Compared with traditional computational methods, including polynomial fitting, wavelet transform, Fourier transform, and peak detection, our results consistently show significant advantages in both accuracy and computational efficiency when tested on Raman spectra measured from phantoms and cells as well as surfaced enhanced Raman spectra from blood serum samples. In particular, our method yields clean Raman spectra closest to the reference results generated by polynomial fitting while several orders of magnitude faster than others. Therefore, the proposed fast fluorescence suppression method is promising in Raman spectroscopic imaging or related application in which high computation efficiency is critical and a calibration dataset is available.
关键词： Raman spectroscopy,fluorescence suppression,Raman imaging,Biomedical signal processing
更新于2025-09-11 14:15:04