Raman Microscope System Research Articles

Development of a cost-effective confocal Raman microscopy with high sensitivity

Confocal Raman microscopy is a powerful technique for identifying materials and molecular species; however, the signal from Raman scattering is extremely weak. Typically, handheld Raman instruments are cost-effective but less sensitive, while high-end scientific-grade Raman instruments are highly sensitive but extremely expensive. This limits the widespread use of Raman technique in our daily life. To bridge this gap, we explored and developed a cost-effective yet highly sensitive confocal Raman microscopy system. The key components of the system include an excitation laser based on readily available laser diode, a lens-grating-lens type spectrometer with high throughput and image quality, and a sensitive detector based on a linear charge-coupled device (CCD) that can be cooled down to −30 °C. The developed compact Raman instrument can provide high-quality Raman spectra with good spectral resolution. The 3rd order 1450 cm−1 peak of Si (111) wafer shows a signal-to-noise ratio (SNR) better than 10:1, demonstrating high sensitivity comparable to high-end scientific-grade Raman instruments. We also tested a wide range of different samples (organic molecules, minerals and polymers) to demonstrate its universal application capability.

Expanding the horizons: Raman probe development and spectra preprocessing evaluation for recognition of large hydroxyapatite‐based samples

AbstractThis paper addresses the challenge posed by the size of certain objects that do not conform to the constraints of microscope‐coupled Raman spectrometers, making sample collection impossible due to their inherent value or nature. Specifically, materials like hydroxyapatite‐based substances used in artistic and ornamental carvings, such as bone or ivory, fall within this problematic category. The focus of this study is the enhancement of analytical capabilities in the context of large objects using a Raman microscope system. The study details the innovation involving a remote probe integrated with fiber optics, elaborating on the design and performance aspects, and emphasizing the appropriateness of chosen components in the analysis of ivory artifacts belonging to private collectors. In order to assess the robustness of our discriminative approaches, an archaeological bone and the exposed dentine in a human tooth were also evaluated and compared. Results showed that using an 805‐nm longpass dichroic mirror successfully directed the near‐infrared laser onto the samples and significantly suppressed the Rayleigh scattering contribution to the spectrum. Regarding the preprocessing methods to spectra evaluation essayed, the most promising approach was the use of principal component analysis for dimension reduction followed by k‐means cluster analysis. By leveraging the complementary strengths of PCA and k‐means clustering, the robustness and interpretability of clustering analyses are enhanced.

Stress Component Decoupling Analysis Based on Large Numerical Aperture Objective Lens, an Impractical Approach.

Micro Raman spectroscopy is an effective method to quantitatively analyse the internal stress of semiconductor materials and structures. However, the decoupling analysis of the stress components for {100} monocrystalline silicon (c-Si) remains difficult. In the work outlined, physical and simulation experiments were combined to study the influence of the objective lens numerical aperture (NA) on the Raman stress characterization. The physical experiments and simulation experiments show that the spectral results obtained by using lenses with different NAs can accurately obtain the principal stress sum but cannot decouple the components of the in-plane stress. Even if the spectral resolution of the simulated experiment is ideal (The random errors of the polarization directions of less than ±1° and the systematic random errors of less than ±0.02 cm−1). The analysis based on the theoretical model demonstrates that the proportion of the principal stress sum in the Raman shift obtained in an actual experiment exceeded 98.7%, while the proportion of the principal stress difference part was almost negligible. This result made it difficult to identify the variable effects of different stress states from the experimental results. Further simulation experiments in this work verify that when the principal stress sum was identical, the differences in the Raman shifts caused by different stress states were much smaller than the resolution of the existing Raman microscope system, which was hardly possible to identify in the experimental results. It was proven that decoupling analysis of stress components using the large-NA objective lens lacked actual practicability.

Development of Effectual Substrates for SERS by Nanostructures-on flexible surfaces

The current study examines recent advancements in surface-enhanced Raman scattering (SERS), a technique that employs flexible surfaces as an active substrate, this surfaces consist from two-dimensional thermo-plasmonic grating. With 53 nm Au layer (was deposited on the 2D grating structure of the PDMS by the PVD method). The explosive wire technique was used to preparing Ag nanoparticles that were used for the purpose of SERS. The effect of the plasmonic nanostructures on the absorption spectra and Surface - Enhanced Raman Scattering (SERS) activities was examined. Rhodamine 6G dye was used as a probe molecule. X-Ray diffraction (XRD) was used to examine the structural characteristics of the nanoparticles. The morphology was assessed using Field Emission Scanning Electron Microscopy(FESEM). A twin beam UV-Vis Spectrophotometer was used to measure the absorption of the combined Rh6G dye (concentration 1×10“–6M) with the nanostructures. a Sunshine Raman microscope system and a 50mm objective lens, used for investigating the Raman spectra of the Rh6G combined with nanostructures. The results showed that the enhancement factor (EF) for SERS of R6G (1×M) reached to (2.2×10 3) When using Ag nanoparticles and (0.08 × 103) when R6G deposited directly on the flexible substrates without nanostructures at the wave number (1650 cm−1), we produced a recyclable, homogeneous, and highly sensitive SERS substrate with dependable reproducibility. For the SERS substrate, a surface made up of two-dimensional (2D) flexible grating substrates was chosen to provide multiple modalities in electrical and medicinal applications.

An organic crystalline state in ageing atmospheric aerosol proxies: spatially resolved structural changes in levitated fatty acid particles

Abstract. Organic aerosols are key components of the Earth's atmospheric system. The phase state of organic aerosols is known to be a significant factor in determining aerosol reactivity, water uptake and atmospheric lifetime – with wide implications for cloud formation, climate, air quality and human health. Unsaturated fatty acids contribute to urban cooking emissions and sea spray aerosols. These compounds, exemplified by oleic acid and its sodium salt, are surface-active and have been shown to self-assemble into a variety of liquid-crystalline phases upon addition of water. Here we observe a crystalline acid–soap complex in acoustically levitated oleic acid–sodium oleate particles. We developed a synchrotron-based simultaneous small-angle and wide-angle X-ray scattering (SAXS and WAXS)–Raman microscopy system to probe physical and chemical changes in the proxy during exposure to humidity and the atmospheric oxidant ozone. We present a spatially resolved structural picture of a levitated particle during humidification, revealing a phase gradient consisting of a disordered liquid crystalline shell and crystalline core. Ozonolysis is significantly slower in the crystalline phase compared with the liquid phase, and a significant portion (34 ± 8 %) of unreacted material remains after extensive oxidation. We present experimental evidence of inert surface layer formation during ozonolysis, taking advantage of spatially resolved simultaneous SAXS–WAXS experiments. These observations suggest that atmospheric lifetimes of surface-active organic species in aerosols are highly phase-dependent, potentially impacting climate, urban air quality and long-range transport of pollutants such as polycyclic aromatic hydrocarbons (PAHs).

In Situ Water Quantification in Natural Deep Eutectic Solvents Using Portable Raman Spectroscopy

Raman spectroscopy is a label-free, non-destructive, non-invasive analytical tool that provides insight into the molecular composition of samples with minimum or no sample preparation. The increased availability of commercial portable Raman devices presents a potentially easy and convenient analytical solution for day-to-day analysis in laboratories and production lines. However, their performance for highly specific and sensitive analysis applications has not been extensively evaluated. This study performs a direct comparison of such a commercially available, portable Raman system, with a research grade Raman microscope system for the analysis of water content of Natural Deep Eutectic Solvents (NADES). NADES are renewable, biodegradable and easily tunable “green” solvents, outcompeting existing organic solvents for applications in extraction from biomass, biocatalysis, and nanoparticle synthesis. Water content in NADES is, however, a critical parameter, affecting their properties, optimal use and extraction efficiency. In the present study, portable Raman spectroscopy coupled with Partial Least Squares Regression (PLSR) is investigated for rapid determination of water content in NADES samples in situ, i.e., directly in glassware. Three NADES systems, namely Betaine Glycerol (BG), Choline Chloride Glycerol (CCG) and Glucose Glycerol (GG), containing a range of water concentrations between 0% (w/w) and 28.5% (w/w), were studied. The results are directly compared with previously published studies of the same systems, using a research grade Raman microscope. PLSR results demonstrate the reliability of the analysis, surrendering R2 values above 0.99. Root Mean Square Errors Prediction (RMSEP) of 0.6805%, 0.9859% and 1.2907% w/w were found for respectively unknown CCG, BG and GG samples using the portable device compared to 0.4715%, 0.3437% and 0.7409% w/w previously obtained by analysis in quartz cuvettes with a Raman confocal microscope. Despite the relatively higher values of RMSEP observed, the comparison of the percentage of relative errors in the predicted concentration highlights that, overall, the portable device delivers accuracy below 5%. Ultimately, it has been demonstrated that portable Raman spectroscopy enables accurate quantification of water in NADES directly through glass vials without the requirement for sample withdrawal. Such compact instruments provide solvent and consumable free analysis for rapid analysis directly in laboratories and for non-expert users. Portable Raman is a promising approach for high throughput monitoring of water content in NADES that can support the development of new analytical protocols in the field of green chemistry in research and development laboratories but also in the industry as a routine quality control tool.

Temporal Imaging of Live Cells by High-Speed Confocal Raman Microscopy.

Label-free live cell imaging was performed using a custom-built high-speed confocal Raman microscopy system. For various cell types, cell-intrinsic Raman bands were monitored. The high-resolution temporal Raman images clearly delineated the intracellular distribution of biologically important molecules such as protein, lipid, and DNA. Furthermore, optical phase delay measured using quantitative phase microscopy shows similarity with the image reconstructed from the protein Raman peak. This reported work demonstrates that Raman imaging is a powerful label-free technique for studying various biomedical problems in vitro with minimal sample preparation and external perturbation to the cellular system.

Surface Molecular Imprinting with Bacteria: Visualizing Re-Binding and Selectivity

Introduction Surface molecular imprinting [1,2] is one of the preferred techniques when it comes to generating biomimetic recognition for sensing bioanalytes. Limiting oneself to the surface of the respective molecularly imprinted polymer (MIP) usually is no problem, because biospecies are usually large enough that few binding events lead to measurable sensor responses, e.g. for mass-sensitive bacteria detection [3]. However, the detection limits of quartz crystal microbalances (QCM) do usually not meet the needs for detecting contamination of real-life samples when it comes to pathogen detection. The (geometrical) limitation of surface MIP in that regard makes it necessary to think about suitable systems for pre-concentration prior to the sensor measurement. Herein, we report Raman Microscopy studies on bacteria surface MIP aiming at visualizing different areas of the polymer and distinguishing between different species bound to the surface. Furthermore, we assess the binding properties of MIP resulting from Pickering emulsion polymerization [4] as a possible approach to selectively pre-concentrate bacteria. Experimental For molecular imprinting, we chose a non-pathogenic strain of Escherichia coli (E. coli) as a model species. We prepared surface MIP of two different morphologies based on polystyrenes cross-linked with divinyl benzene utilizing azo-bisisobutyronitrile (AIBN) as a radical initiator. For MIP thin films, we prepared respective mixtures of monomer and crosslinker, pre-polymerized at 70°C, and then spin-coated onto the respective devices. In parallel, we prepared stamps comprising E. coli on their surfaces. Then, we pressed the stamp into the oligomer thin films on the respective surface and cured the system at 80°C over night. We took all spectra on a confocal Raman Microscopy system (WiTec alpha300RAS) at an excitation wavelength of l=532nm. Chemometric data evaluation relied on the software package Solo&Mia by Eigenvector. For Pickering emulsion, we prepared mixtures of styrene and divinylbenzene and used bacteria to emulsify them in either distilled water, or a suitable buffer system (e.g. 10mM PBS) and polymerized the bacteria stabilized droplets at 37°C. Then, we removed E. coli cells from the polymer surface via solvent extractions in acetic acid + SDS, water and methanol. Results and Discussion In a first step it was essential to clarify if one can use the Raman spectra of different bacteria species and polymer, to differentiate between those, respectively. Polymer and bacteria spectra obviously differ from each other enough to distinguish them by the naked eye. However, this is not the case for the Raman emission spectra of different bacteria species, because they all contain nucleic acids, proteins, and lipids. Therefore it is necessary to rely on chemometric strategies – modified partial least squares discriminant analysis (PLS-DA) in the concrete case – to achieve such goal. This is indeed possible: Fig. 1A shows the outcome for four different bacteria species, namely Escherichia coli, Lactococcus lactis, Bacillus cereus and Staphylococcus epidermidis that clearly demonstrates separation of the species according to their spectral properties. Knowing the specific spectral ranges also allows for generating false-color images showing which areas of a bacteria MIP surfaces reveal pure polymer and which parts contain bacteria of different species. It is even possible to go one step further: Comparing AFM and false color so-called RamanTV images (see Fig. 1B) for an example of the latter) demonstrates that the Raman microscope is even useful for distinguishing polymer surface and imprinted cavities. For such micrometer-sized analytes, the combination of Raman microscopy and AFM hence allows for generating maps showing all possible types of surfaces, i.e. polymer matrix as well as both unoccupied cavities and different bacteria species present at the polymer surface. This opens the perspective of directly visualizing occupancy and selectivity of the respective MIP.AFM turned out useful to visualize such imprints not only on flat surfaces, but also on curved ones: Figure 1C) and 1D) reveal an imprinted site on the surface of a miroparticle resulting from emulsion polymerization, Fig. 1E) an SEM image showing occupied and empty cavities. One can generate such cavities in different polymer matrices, for instance when replacing divinyl benzene as a cross-linker by trimethyolylpropane trimethacrylate (TRIM), or ethylene glycol dimethacrylate (EGDMA). In both cases, the respective imprinted surface reveal cavities that fit the size and shape of the template bacteria. Scanning electron microscopy also revealed that bacteria re-occupy those cavities if one exposes the particles to to bacteria suspensions. This leads to two conclusions: first, one can tune polymer properties without destroying the emulsion structure necessary for Pickering emulsion. This is of interest for bringing the artificial system closer to physiological conditions. Second, those particles are inherently suitable for selectively pre-concentrating those species from larger samples. Figure 1

Signature of Plasmonic Nanostructures Synthesised by Electrical Exploding Wire Technique on Surface-Enhanced Raman Scattering

This work aims to fabricate two types of plasmonic nanostructures by electrical exploding wire (EEW) technique and study the effects of the different morphologies of these nanostructures on the absorption spectra and Surface-Enhanced Raman Scattering (SERS) activities, using Rhodamine 6G as a probe molecule. The structural properties of these nanostructures were examined using X-Ray diffraction (XRD). The morphological properties were examined using field emission scanning electron microscopy (FESEM) and scanning transmission electron microscopy (STEM). The absorption spectra of the mixed R6G laser dye (concentration 1×10-6 M) with prepared nanostructures were examined by double beam UV-Vis Spectrophotometer. The Raman spectra of the R6G mixed with the prepared nanostructures were examined using a Horiba HR Evolution 800 Raman microscope system with an objective lens (50 ×). The FESEM and STEM images indicated that the Ag nanoparticles (AgNPs) with 35 nm average particle sizes were decorated on the surface of the AgNWs and the PDA layer by EEW technique, forming AgNW@AgNPs and AgNW@PDA@AgNPs nanostructures. The results indicated that the increased intensities of the absorption spectra peaks and the SERS arise from the hot spots and the roughness of the surface of nanostructures. The SERS enhancement factor of R6G (1×10-6 M) was reached at 2.3×107 and 2.5×107, at the wave number of 1650 cm-1, for the AgNW@AgNPs and AgNW@PDA@AgNPs nanostructures, respectively, after being excited by (λexc. = 532 nm) laser source. It can be concluded that the AgNW@AgNPs and AgNW@PDA@AgNPs nanostructures were fabricated with an easy and simple way without the need for additional chemical compounds. These nanostructures attained a reliable and sensitive detection and can be utilized in a variety of SERS applications, such as chemical and biological sensors.

Surface Molecular Imprinting with Bacteria: Visualizing Re-Binding and Selectivity

Introduction Surface molecular imprinting [1,2] is one of the preferred techniques when it comes to generating biomimetic recognition for sensing bioanalytes. Limiting oneself to the surface of the respective molecularly imprinted polymer (MIP) usually is no problem, because biospecies are usually large enough that few binding events lead to measurable sensor responses, e.g. for mass-sensitive bacteria detection [3]. However, the detection limits of quartz crystal microbalances (QCM) do usually not meet the needs for detecting contamination of real-life samples when it comes to pathogen detection. The (geometrical) limitation of surface MIP in that regard makes it necessary to think about suitable systems for pre-concentration prior to the sensor measurement. Herein, we report Raman Microscopy studies on bacteria surface MIP aiming at visualizing different areas of the polymer and distinguishing between different species bound to the surface. Furthermore, we assess the binding properties of MIP resulting from Pickering emulsion polymerization [4] as a possible approach to selectively pre-concentrate bacteria. Experimental For molecular imprinting, we chose a non-pathogenic strain of Escherichia coli (E. coli) as a model species. We prepared surface MIP of two different morphologies based on polystyrenes cross-linked with divinyl benzene utilizing azo-bisisobutyronitrile (AIBN) as a radical initiator. For MIP thin films, we prepared respective mixtures of monomer and crosslinker, pre-polymerized at 70°C, and then spin-coated onto the respective devices. In parallel, we prepared stamps comprising E. coli on their surfaces. Then, we pressed the stamp into the oligomer thin films on the respective surface and cured the system at 80°C over night. We took all spectra on a confocal Raman Microscopy system (WiTec alpha300RAS) at an excitation wavelength of l=532nm. Chemometric data evaluation relied on the software package Solo&Mia by Eigenvector. For Pickering emulsion, we prepared mixtures of styrene and divinylbenzene and used bacteria to emulsify them in either distilled water, or a suitable buffer system (e.g. 10mM PBS) and polymerized the bacteria stabilized droplets at 37°C. Then, we removed E. coli cells from the polymer surface via solvent extractions in acetic acid + SDS, water and methanol. Results and Discussion In a first step it was essential to clarify if one can use the Raman spectra of different bacteria species and polymer, to differentiate between those, respectively. Polymer and bacteria spectra obviously differ from each other enough to distinguish them by the naked eye. However, this is not the case for the Raman emission spectra of different bacteria species, because they all contain nucleic acids, proteins, and lipids. Therefore it is necessary to rely on chemometric strategies – modified partial least squares discriminant analysis (PLS-DA) in the concrete case – to achieve such goal. This is indeed possible: Fig. 1A shows the outcome for four different bacteria species, namely Escherichia coli, Lactococcus lactis, Bacillus cereus and Staphylococcus epidermidis that clearly demonstrates separation of the species according to their spectral properties. Knowing the specific spectral ranges also allows for generating false-color images showing which areas of a bacteria MIP surfaces reveal pure polymer and which parts contain bacteria of different species. It is even possible to go one step further: Comparing AFM and false color so-called RamanTV images (see Fig. 1B) for an example of the latter) demonstrates that the Raman microscope is even useful for distinguishing polymer surface and imprinted cavities. For such micrometer-sized analytes, the combination of Raman microscopy and AFM hence allows for generating maps showing all possible types of surfaces, i.e. polymer matrix as well as both unoccupied cavities and different bacteria species present at the polymer surface. This opens the perspective of directly visualizing occupancy and selectivity of the respective MIP.AFM turned out useful to visualize such imprints not only on flat surfaces, but also on curved ones: Figure 1C) and 1D) reveal an imprinted site on the surface of a miroparticle resulting from emulsion polymerization, Fig. 1E) an SEM image showing occupied and empty cavities. One can generate such cavities in different polymer matrices, for instance when replacing divinyl benzene as a cross-linker by trimethyolylpropane trimethacrylate (TRIM), or ethylene glycol dimethacrylate (EGDMA). In both cases, the respective imprinted surface reveal cavities that fit the size and shape of the template bacteria. Scanning electron microscopy also revealed that bacteria re-occupy those cavities if one exposes the particles to to bacteria suspensions. This leads to two conclusions: first, one can tune polymer properties without destroying the emulsion structure necessary for Pickering emulsion. This is of interest for bringing the artificial system closer to physiological conditions. Second, those particles are inherently suitable for selectively pre-concentrating those species from larger samples.

Au@Ag nanorod horizontal arrays: Self-assembly preparation and in situ monitoring SERS of plasmonic catalytic reaction

Abstract Here, we successfully synthesized silver-coated gold nanorods (Au@Ag NRs) via a facile wet chemical method. The catalytic property of Au@Ag NRs in water solution was much better than that of Au NRs in water solution. To obtain high catalytic properties, we self-assembled a single-layer Au@Ag NR array by evaporation on a silicon wafer. The catalytic activity of the Au@Ag NR array was probed using the reduction of 4-nitrothiophenol. The reaction processes were monitored and identified through in situ surface-enhanced Raman spectroscopy based on the confocal Raman microscope system. This study provides a simple and fast method to improve the catalytic property of the noble nanoparticles.

Evaluation of Lateral Resolution for Confocal Raman Microscopy Using Gold Nano‐Lines Made by Electron Beam Lithography

Assessing the instrumental resolution of confocal Raman microscopy is a key aspect in 2D or 3D imaging in various applications. An important issue in this regard is the experimental measurement of a lateral resolution for the Raman microscope system. Several methods have been proposed for the resolution measurement in fluorescence microscopy; however, these methods have rather limited applications. In this paper, we demonstrate an experimental approach for evaluating the lateral resolution with well‐defined nano‐patterns in confocal Raman microscopy and discuss the factors that can improve estimation of instrumental resolution. This study contributes to the further understanding of the assessment of instrumental resolution in confocal scanning Raman microscopy.

Load Transfer Behavior of 3D Aerogels Fabricated with Halloysite Nanotubes

AbstractNanofibrous network aerogels as an important class of porous material have received enormous attention in materials research. However, the fabrication of nanofibrous network aerogels with short fiber as building blocks is extremely challenging, since it is difficult for them to build 3D network structures spontaneously from the topological point of view. Here the synthesis and load transfer behavior of 3D aerogels composed of halloysite nanotube (HNT) short fibers are described. The resulting aerogels take inorganic materials as the skeleton, elastic organic materials as the connection point, and exhibit inorganic/organic phase interfaces. Confocal Raman microscopy system is utilized to investigate the structural‐dynamic profile of halloysite clay aerogels (HCAs) under applied load. The results indicate that the deformation mainly occurs in the polysiloxane (PSO) molecular chain connected with the HNT skeleton. HCAs have a certain load transfer capability, and the PSO chains between tubes are strong enough to support the HCA skeleton.

Diagnosis of chagas disease from human blood serum using surface-enhanced Raman scattering (SERS) spectroscopy and chemometric methods

Surface-Enhanced Raman Scattering (SERS) spectroscopic technique and chemometric methods were combined to make a first noninvasive diagnosis of Chagas disease in human blood serum samples. We worked with 110 samples of patients; 45 of them healthy, and 65 infected which were separated into asymptomatic and symptomatic samples. Because of the biological samples exhibiting the Raman signals, the SERS effect was achieved using concentrated silver nanoparticles synthesized previously and attached prior to data collection. SERS spectra of each sample were acquired in the range from 400 to1700 cm−1 using a Raman microscope system. Both, Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were used for the data analysis.The results obtained had an accuracy of 96.3% for the classification of the samples into three groups (healthy, symptomatic, and asymptomatic patients).

Preparation of SERS Substrates for the Detection of Organic Molecules at Low Concentration

In this paper, we present the results of the preparation of Surface Enhanced Raman Spectroscopy (SERS) substrates by depositing silver nanoparticles (Ag NPs) onto a porous silicon wafer that is produced by the chemical etching process. The influences of the preparation parameters such as resistivity of the silicon wafer, the anodizing current density, etching time to the size of pores were systematically investigated. The SERS substrates prepared were characterised by using appropriate techniques: the morphology and pores size by scanning electron microscope (SEM), the SERS activity by Raman scattering measure of organic molecules malachite green (MG) embedded into the substrate at room temperature. Our experimental results show that a home-made Raman microscope system could be efficiently used to detect the MG molecules at the concentration lower than 10-7 M with the prepared SERS substrates which have Ag NPs in the obtained pores of 10 – 40 nm.

Investigating Effects of Proteasome Inhibitor on Multiple Myeloma Cells Using Confocal Raman Microscopy.

Due to its label-free and non-destructive nature, applications of Raman spectroscopic imaging in monitoring therapeutic responses at the cellular level are growing. We have recently developed a high-speed confocal Raman microscopy system to image living biological specimens with high spatial resolution and sensitivity. In the present study, we have applied this system to monitor the effects of Bortezomib, a proteasome inhibitor drug, on multiple myeloma cells. Cluster imaging followed by spectral profiling suggest major differences in the nuclear and cytoplasmic contents of cells due to drug treatment that can be monitored with Raman spectroscopy. Spectra were also acquired from group of cells and feasibility of discrimination among treated and untreated cells using principal component analysis (PCA) was accessed. Findings support the feasibility of Raman technologies as an alternate, novel method for monitoring live cell dynamics with minimal external perturbation.

Loads transfer across static electrical phase interfaces in silica aerogel/polymethyl methacrylate composites

Silica aerogel (SA)/polymethyl methacrylate (PMMA) composites with static electrical phase interfaces were prepared to investigate loads transfer across the interfaces. Preparations of SA/polymer hybrid composites were based on the interaction between the positive charges in SA and negative charges in polymer. Characterizations of the SA, polymers, and composites were performed by scanning electron microscopy (SEM), Raman spectroscopy, thermogravimetric analysis (TGA), and so on. A Raman microscope system was employed for the investigation of loads transfer across phase interfaces. The results indicated that the SA/PMMA composites with static electrical phase interfaces and nanoporous structure were obtained. Based on the Raman mapping results, the composite with covalent bonding phase interfaces got the most efficient load transfer ability. The load transfer through the static electrical phase interfaces in composites is also effective. The static electrical phase interfaces that are physical interactions between the silica phase and polymer phase are with high interfacial thermal resistances, and the heat flux could be held in silica phase. It could be achieved with minimal changes to the overall thermal conductivity of the material as possible.

Improving spatial resolution of confocal Raman microscopy by super-resolution image restoration.

A new super-resolution image restoration confocal Raman microscopy method (SRIR-RAMAN) is proposed for improving the spatial resolution of confocal Raman microscopy. This method can recover the lost high spatial frequency of the confocal Raman microscopy by using Poisson-MAP super-resolution imaging restoration, thereby improving the spatial resolution of confocal Raman microscopy and realizing its super-resolution imaging. Simulation analyses and experimental results indicate that the spatial resolution of SRIR-RAMAN can be improved by 65% to achieve 200 nm with the same confocal Raman microscopy system. This method can provide a new tool for high spatial resolution micro-probe structure detection in physical chemistry, materials science, biomedical science and other areas.

High-speed line-focus Raman microscopy with spectral decomposition of mouse skin

Line-focus Raman microscope system was designed and constructed for high speed quantitative analysis of Raman spectral maps. Laser line generator lens was used for formation of homogeneous laser power distribution thought the line. Three-dimensional Raman maps of mouse skin were obtained using point and line illumination modes. It was shown that laser line illumination can provide Raman spectrum with signal to noise ratio comparable to point illumination mode. The speed of scanning in line-focus mode achieved is two orders of magnitude faster compared to the point illumination mode, which enables ex vivo measurements of large areas of skin surface during a few minutes. Non-negative least squares (NNLS) decomposition of mouse skin spectral maps was done using keratin, lipids, water, lactate, urea and natural moisture factor (NMF) components as library spectra. Fluorescence background of measured spectra was corrected using the fluorescence profile obtained from time-lapse Raman skin measurements, which was used as additional component in NNLS decomposition procedure. The lateral and depth distribution of major skin components obtained from Raman maps mainly correlates with histological information. High-quality line-focus Raman maps from large sample area expand the possibilities of studying skin chemical components distribution.

骨アパタイト・コラーゲンの力学的挙動とラマンシフトの関係

Bone is often regarded as a composite material consisting of mineral particles and organic matrix of mainly Type I collagen in microscopic scale. The mechanical properties of bone tissues in macroscopic scale depend on the structural organization and properties of constituents in the microscopic scale. Raman spectroscopy is known as useful tool for the analysis of material at ultra-structural level. The aim of this study are to observe the mechanical behaviors of mineral and collagen phases in bone tissues by using Raman imaging system and to investigate the effect of structural anisotropy of cortical bone on the mechanical responses. Cortical bone of bovine femoral diaphyses were used for specimen, where the longer edges of specimens were aligned to the parallel or perpendicular to the femoral axis. Raman microscope system was used for the analysis of mechanical response of bone tissue under tensile loading by the micro-tensile device. Imaging area was 30×30 μm and measurement points were 21×21 at 1.5 μm intervals. Raman shifts of specific Raman peaks were calculated from apatite crystal and collagen molecule in bone matrix. As the results, Raman shift decreased with increasing tensile stress. It was confirmed that the Raman shift was correlated to the lattice strain of apatite crystal measured by X-ray diffraction.