micro-Raman Spectroscopy Techniques Research Articles

Unveiling the potential of high-temperature chemical vapour deposition growth of boron carbide: Investigating physicochemical, mechanical and electrical properties

Chemical vapour deposition (CVD) is a widely utilized technique in industry, particularly venerated for its precision and reliability in producing hard ceramic materials. In this study, a gas mixture comprising BCl3-CH4-H2 was employed to deposit boron carbide (B4C) onto a graphite substrate to investigate the substrate temperature-dependent physicochemical, mechanical, and electrical properties of the B4C. The phase compositional and vibrational characteristics of the B4C were thoroughly assessed using X-ray diffraction (XRD) and micro-Raman spectroscopy techniques, respectively. The field-emission scanning electron microscopy (FE-SEM) images reveal a morphological transition from murataite to triangular flakes, accompanied by noticeable grain expansion with growing substrate temperature. Additionally, energy-dispersive X-ray spectroscopy (EDS) indicates a consistent trend of increasing boron concentration and decreasing carbon concentration with rising substrate temperature. Consequently, variations in substrate temperature notably tune the deposition rate, mechanical and electrical properties of B4C. The deposition rate at 1200 °C was 1476 μm/h. Whereas, the material hardness and electrical conductivity of the CVD deposited B4C were found to be 3166 HV and 18.358 Ω-1cm-1, respectively. The present study highlights the importance of high-temperature CVD growth of the B4C for industrial applications.

Correlative Raman Imaging: Development and Cancer Applications.

Despite extensive research efforts, cancer continues to stand as one of the leading causes of death on a global scale. To gain profound insights into the intricate mechanisms underlying cancer onset and progression, it is imperative to possess methodologies that allow the study of cancer cells at the single-cell level, focusing on critical parameters such as cell morphology, metabolism, and molecular characteristics. These insights are essential for effectively discerning between healthy and cancerous cells and comprehending tumoral progression. Recent advancements in microscopy techniques have significantly advanced the study of cancer cells, with Raman microspectroscopy (RM) emerging as a particularly powerful tool. Indeed, RM can provide both biochemical and spatial details at the single-cell level without the need for labels or causing disruptions to cell integrity. Moreover, RM can be correlated with other microscopy techniques, creating a synergy that offers a spectrum of complementary insights into cancer cell morphology and biology. This review aims to explore the correlation between RM and other microscopy techniques such as confocal fluoresce microscopy (CFM), atomic force microscopy (AFM), digital holography microscopy (DHM), and mass spectrometry imaging (MSI). Each of these techniques has their own strengths, providing different perspectives and parameters about cancer cell features. The correlation between information from these various analysis methods is a valuable tool for physicians and researchers, aiding in the comprehension of cancer cell morphology and biology, unraveling mechanisms underlying cancer progression, and facilitating the development of early diagnosis and/or monitoring cancer progression.

Probing the structure of water in individual living cells

Water regulates or even governs a wide range of biological processes. Despite its fundamental importance, surprisingly little is known about the structure of intracellular water. Herein we employ a Raman micro-spectroscopy technique to uncover the composition, abundance and vibrational spectra of intracellular water in individual living cells. In three different cell types, we show a small but consistent population (~3%) of non-bulk-like water. It exhibits a weakened hydrogen-bonded network and a more disordered tetrahedral structure. We attribute this population to biointerfacial water located in the vicinity of biomolecules. Moreover, our whole-cell modeling suggests that all soluble (globular) proteins inside cells are surrounded by, on average, one full molecular layer (about 2.6 Angstrom) of biointerfacial water. Furthermore, relative invariance of biointerfacial water is observed among different single cells. Overall, our study not only opens up experimental possibilities of interrogating water structure in vivo but also provides insights into water in life.

Mussels (Mytilus spp.) in Svalbard contain microplastic particles in tissues: Implications for monitoring

We examined the presence of microplastics in blue mussels Mytilus spp. from the intertidal zone of western Spitsbergen in Arctic Svalbard. The optical microscopy technique detected a total of 148 microplastics, with the highest concentration per mussel being 24 particles. Microplastics were found in 84% of the examined mussels. The microplastics ranged in size from <0.5 mm to 5 mm and consisted of fibers (83%), fragments (13%), plates (3%), and spherules (1%). The micro-Raman spectroscopy technique revealed four different types of polymers: polyethylene (67%), nylon-12 (17%), low-density polyethylene (11%), and polypropylene (5%). Our research shows that Arctic coastal waters are polluted with microplastics notwithstanding their remoteness. These findings suggest that microplastic contamination may harm marine life and coastal ecosystems and require further research into long-term environmental effects. We also indicate that intertidal mussels may be beneficial for monitoring microplastics because they can be collected without involving diving.

Long-term corrosion of copper alloys in the soil: new aspects of corrosion morphology in archaeological vessels from south-western Iran

A group of copper-based objects excavated at Deh Dumen cemetery, in south-western Iran, was studied and analysed to examine the long-term corrosion morphology and mechanism in the soil burial environment. For this purpose, twenty-two samples from twenty-one copper-based vessels were studied and analysed using X-ray diffraction, scanning electron microscopy—energy dispersive X-ray spectroscopy, micro-Raman spectroscopy and metallography techniques. The results of the analyses showed that the majority of vessels are made of tin bronze, along with two arsenical copper samples. The extent of corrosion observed ranges from very thin corrosion crusts to thick crusts and entirely corroded structures. These three identified corrosion morphologies display a multi-layered corrosion stratigraphy as well as the preserved limit of the original surface. The corrosion crusts include internal tin-rich and external copper-rich layers, and the main corrosion mechanism for the formation of multi-layered corrosion crusts is decuprification or selective dissolution of copper during the long-term burial time in a moderately Cl-contaminated soil. The three identified corrosion morphologies are similar to the previously published morphologies, but some clear deviations are apparent and are discussed here.

Modeling versatile and dynamic anaerobic metabolism for PAOs/GAOs competition using agent-based model and verification via single cell Raman Micro-spectroscopy

Side-stream enhanced biological phosphorus removal process (S2EBPR) has been demonstrated to improve performance stability and offers a suite of advantages compared to conventional EBPR design. Design and optimization of S2EBPR require modification of the current EBPR models that were not able to fully reflect the metabolic functions of and competition between the polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) under extended anaerobic conditions as in the S2EBPR conditions. In this study, we proposed and validated an improved model (iEBPR) for simulating PAO and GAO competition that incorporated heterogeneity and versatility in PAO sequential polymer usage, staged maintenance-decay, and glycolysis-TCA pathway shifts. The iEBPR model was first calibrated against bulk batch testing experiment data and proved to perform better than the previous EBPR model for predicting the soluble orthoP, ammonia, biomass glycogen, and PHA temporal profiles in a starvation batch testing under prolonged anaerobic conditions. We further validated the model with another independent set of anaerobic testing data that included high-resolution single-cell and specific population level intracellular polymer measurements acquired with single-cell Raman micro-spectroscopy technique. The model accurately predicted the temporal changes in the intracellular polymers at cellular and population levels within PAOs and GAOs, and further confirmed the proposed mechanism of sequential polymer utilization, and polymer availability-dependent and staged maintenance-decay in PAOs. These results indicate that under extended anaerobic phases as in S2EBPR, the PAOs may gain competitive advantages over GAOs due to the possession of multiple intracellular polymers and the adaptive switching of the anaerobic metabolic pathways that consequently lead to the later and slower decay in PAOs than GAOs. The iEBPR model can be applied to facilitate and optimize the design and operations of S2EBPR for more reliable nutrient removal and recovery from wastewater.

Vibrational spectroscopies for biochemical investigation of X-ray exposure effects on SH-SY5Y human neuroblastoma cells.

Neuroblastoma is the most recurring cancer in childhood and adolescence. The SH-SY5Y neuroblastoma cell line is generally adopted for elaborating new therapeutical approaches and/or elaborating strategies for the prevention of central nervous system disturbances. In fact, it represents a valid model system for investigating in vitro the effects on the brain of X-ray exposure using vibrational spectroscopies that can detect early radiation-induced molecular alterations of potential clinical usefulness. In recent years, we dedicated significant efforts in the use of Fourier-transform and Raman microspectroscopy techniques for characterizing such radiation-induced effects on SH-SY5Y cells by examining the contributions from different cell components (DNA, proteins, lipids, and carbohydrates) to the vibrational spectra. In this review, we aim at revising and comparing the main results of our studies to provide a wide outlook of the latest outcomes and a framework for future radiobiology research using vibrational spectroscopies. A short description of our experimental approaches and data analysis procedures is also reported.

Investigation of deep defects and their effects on the properties of NiO/β-Ga2O3 heterojuncion diodes

In this study, the effect of rapid thermal annealing (RTA) on the electrical and optical properties of NiO/ β-Ga2O3 heterojunction diodes was investigated using capacitance-voltage, current-voltage, Deep Level Transient Spectroscopy (DLTS), Laplace DLTS, photoluminescence and micro-Raman spectroscopy techniques, and SILVACO-TCAD numerical simulator. The NiO is designed to be lowly-doped, allowing for the NiO full depletion at zero bias and the study of properties of β-Ga2O3 and its interface with NiO. Micro-Raman results revealed good agreement with the theoretical and experimental results reported in the literature. The photoluminescence intensity of the sample after RTA is five times higher than the fresh sample due to a rise in the density of gallium and oxygen vacancies (VGa + VO) in the annealed β-Ga2O3 samples. The current-voltage characteristics showed that annealed devices exhibited a lower ideality factor at room temperature and higher barrier height compared with fresh samples. The DLTS measurements demonstrated that the number of electrically active traps were different for the two samples. In particular, three and one electron traps were detected in fresh samples and annealed samples, respectively. SILVACO-TCAD was used to understand the distribution of the detected electron E2 trap (Ec-0.15 eV) in the fresh sample and the dominant transport mechanisms. A fairly good agreement between simulation and measurements was achieved considering a surface NiO acceptor density of about 1 × 1019 cm−3 and E2 trap depth into the surface of β-Ga2O3 layer of about 0.220 µm and the effect of the most observed Ec-0.75 eV trap level in β-Ga2O3. These results unveil comprehensive physics in NiO/β-Ga2O3heterojunction and suggest that RTA is an essential process for realizing high-performance NiO/β-Ga2O3devices.

Brillouin–Raman micro-spectroscopy and machine learning techniques to classify osteoarthritic lesions in the human articular cartilage

In this study, Brillouin and Raman micro-Spectroscopy (BRamS) and Machine Learning were used to set-up a new diagnostic tool for Osteoarthritis (OA), potentially extendible to other musculoskeletal diseases. OA is a degenerative pathology, causing the onset of chronic pain due to cartilage disruption. Despite this, it is often diagnosed late and the radiological assessment during the routine examination may fail to recognize the threshold beyond which pharmacological treatment is no longer sufficient and prosthetic replacement is required. Here, femoral head resections of OA-affected patients were analyzed by BRamS, looking for distinctive mechanical and chemical markers of the progressive degeneration degree, and the result was compared to standard assignment via histological staining. The procedure was optimized for diagnostic prediction by using a machine learning algorithm and reducing the time required for measurements, paving the way for possible future in vivo characterization of the articular surface through endoscopic probes during arthroscopy.

Microplastics contamination in the fishes of selected sites in Pasig River and Marikina River in the Philippines

Microplastics (MPs), <5 mm in size, are a concerning pollutant in bodies of water because they can be ingested by biological organisms, posing risks to humans and the environment. This study assessed the extent of MPs contamination in various fish species (Oreochromis niloticus, Arius manillensis, and Pterygoplichthys spp.) in selected sites along two major river systems in the Philippines – Pasig and Marikina Rivers. An optimized Raman microspectroscopy technique was used for imaging and identification of MPs using a mean laser spot size of about 1 μm, which is advantageous in the identification of fibers which have small diameters (<50 μm). It also allowed the simultaneous identification of MPs and their pigment additives, which in turn enabled the tracing of possible sources of these MPs. This is important because the fate and accumulation of MPs in rivers systems, as well as its toxicity is dependent on various factors including polymer type and surface chemistry. Majority of the MPs identified from all the fish species were composed of polypropylene and polyethylene in the form of fragments, which reflects both the widespread use of these polymers for packaging and their environmental fate as riverine plastic debris. Moreover, the detection of MPs in the fish species may affect the food chain and eventually pose health risks for humans. The study could provide guidance on waste and environmental water management in the surrounding region.

A micro-Raman spectroscopy study of inflammatory condition of human cervix: Probing of tissues and blood plasma samples

The present study explores the application of the micro-Raman spectroscopy technique to discriminate normal and cervicitis condition from cervical malignancy by analyzing the Raman signatures of tissues and plasma samples of the same subjects. The Raman peaks from tissue samples at 1026 cm−1,1298 cm−1 and 1243 cm−1 are attributed to glycogen, fatty acids and collagen and are found to be reliable signatures capable of identifying cervicitis and normal condition from cervical cancer. The Raman signatures from plasma samples belonging to carbohydrates (578 cm−1), lipids (1059 cm−1) and nucleic acids (1077 cm−1,1341 cm−1 and 1357 cm−1) are quite useful to classify various pathological conditions of cervix at par with tissue based diagnosis. The PCA-SVM based classification of the spectral data indicates the potential of Raman spectroscopy based liquid biopsy to rule out false diagnosis of cervicitis as cervical malignancy.

Influence of Concentration Levels of β-Tricalcium Phosphate on the Physical Properties of a Dental Adhesive.

Our study assessed the influence of integrating 5% and 10% tricalcium phosphate (β-TCP-Ca3(PO4)2.) nanoparticles into a dental adhesive on the adhesive’s bonding. To evaluate the filler nanoparticles, scanning electron microscopy (SEM), Energy Dispersive X-Ray (EDX) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and micro-Raman spectroscopy techniques were used. Shear Bond strength (SBS) testing, degree of conversion (DC) analysis, investigation of the adhesive–dentin interface, and biofilm experiments were conducted. The SEM micrographs revealed non-uniform agglomerates, while the EDX demonstrated the existence of oxygen ‘O’ (24.2%), phosphorus ‘P’ (17.4%) and calcium ‘Ca’ (60.1%) in the β-TCP nanoparticles. The FTIR and micro-Raman spectra indicated characteristic bands for β-TCP containing materials. The 10 wt.% β-TCP adhesive presented the highest SBS values (NTC-10 wt.% β-TCP: 33.55 ± 3.73 MPa, TC-10 wt.% β-TCP: 30.50 ± 3.25 MPa), followed by the 5 wt.% β-TCP adhesive (NTC-5 wt.% β-TCP: 32.37 ± 3.10 MPa, TC-5 wt.% β-TCP: 27.75 ± 3.15 MPa). Most of the detected failures after bond strength testing were adhesive in nature. The β-TCP adhesives demonstrated suitable dentin interaction by forming a hybrid layer (with few or no gaps) and resin tags. The β-TCP adhesives (10 wt.%) revealed lower DC values compared to control. The incorporation of 5 and 10 wt.% concentrations of β-TCP particles resulted in an increase in SBS values. A linear decline in DC values was witnessed when the nanoparticle concentration was increased. Further research focusing on exploring the influence of higher filler concentrations on adhesive’s properties is recommended.

Raman spectroscopic investigation of the wear effect on the titanium carbonitride/aluminum oxide/titanium nitride coated cutting tool

In this study, micro-Raman spectroscopy technique in combination with multivariate statistical analysis was carried out to investigate the worn surfaces and metallurgical changes in the wear land of chemical vapor deposition—applied titanium carbonitride/aluminum oxide/titanium nitride-coated cutting inserts. To understand the wear process, detailed scanning electron microscopy analysis was also performed. The structural change at the molecular level of the coating due to the wear of the cutting-edge layers was investigated. Tool life was determined at 0.5 mm flank wear of the cutting tool. Thirty-four Raman spectra recorded from the different points of the worn parts of nine cutting inserts were investigated in comparison with the seven spectra of the different points of three unused cutting inserts. The principal component analysis followed by linear discriminant analysis performed on 41 Raman spectral data, clearly separated the samples as worn and unworn cutting inserts, and showed the wear effects. The comparison of the mean Raman spectrum of worn and unworn (unused) cutting inserts showed that the intensities of the aluminum oxide and titanium nitride bands were decreased, whereas the titanium carbide band at 672 cm−1 was increased, as a result of the wear effect. Moreover, the relative intensity of disordered carbon (D band) band to the graphitic sp2 bonded carbon (G band) band was found to increase, due to wear.

Application of reverse engineering in the field of pharmaceutical tablets using Raman mapping and chemometrics

Raman micro-spectroscopy technique offers a combination of relatively high spatial resolution with identification of components or mixtures of components in different sample areas, e.g. on the surface or the cross-section of a sample. This study is focused on the analysis of the tablets from pharmaceutical development with different technological parameters: (1) the manufacturing technology, (2) the particle size of the input API (active pharmaceutical ingredient) and (3) the quantitative composition of the individual excipients.These three mentioned parameters represent the most frequently solved problems in the field of reverse engineering in pharmacy. The investigation aims to distinguish tablets with the above-described technological parameters with limited subjective steps by Raman microscopy. Furthermore, non-subjective methods of Raman data analysis using advanced statistical analysis have been proposed, namely Principal Component Analysis, Soft Independent Modelling of Class Analogy and Linear Discriminant Analysis. The methods successfully distinguished and identified even very small differences in the analysed tablets within our study and provided objective statistic evaluation of Raman maps. The information on component and particle size distribution including their small differences, which is the critical parameter in the development of the original and generic products, was obtained due to combination of these methods. Even though each of these chemometric methods evaluates the data set from a different perspective, their mutual application on the problem of Raman maps evaluation confirmed and specified results on level that would be unattainable with the use of only one them.

To the Question on the Use of Multivariate Analysis and 2D Visualisation of Synchrotron ATR-FTIR Chemical Imaging Spectral Data in the Diagnostics of Biomimetic Sound Dentin/Dental Composite Interface.

In this short communication, we provide information on the use of the hierarchical cluster analysis of synchrotron ATR-FTIR 2D chemical imaging spectral data as a useful and powerful approach to the microspectroscopic diagnostics of molecular composition in the hybrid sound dentin/dental composite interfaces and materials, including ones developed with the use of biomimetic strategies. The described diagnostic approach can be successfully transferred to the analysis and visualisation of 2D spectral data, collected using laboratory Raman and FTIR microspectroscopy techniques.

Imaging of Oral SCC Cells by Raman Micro-Spectroscopy Technique.

We used Raman micro-spectroscopy technique to analyze the molecular changes associated with oral squamous cell carcinoma (SCC) cells in the form of frozen tissue. Previously, Raman micro-spectroscopy technique on human tissue was mainly based on spectral analysis, but we worked on imaging of molecular structure. In this study, we evaluated the distribution of four components at the cell level (about 10 μm) to describe the changes in protein and molecular structures of protein belonging to malignant tissue. We analyzed ten oral SCC samples of five patients without special pretreatments of the use of formaldehyde. We obtained cell level images of the oral SCC cells at various components (peak at 935 cm−1: proline and valine, 1004 cm−1: phenylalanine, 1223 cm−1: nucleic acids, and 1650 cm−1: amide I). These mapping images of SCC cells showed the distribution of nucleic acids in the nuclear areas; meanwhile, proline and valine, phenylalanine, and amide I were detected in the cytoplasm areas of the SCC cells. Furthermore, the peak of amide I in the cancer area shifts to the higher wavenumber side, which indicates the α-helix component may decrease in its relative amounts of protein in the β-sheet or random coil conformation. Imaging of SCC cells with Raman micro-spectroscopy technique indicated that such a new observation of cancer cells is useful for analyzing the detailed distribution of various molecular conformation within SCC cells.

Evaluation of Physical-Mechanical properties of different Bulk-Fill composites / Avaliação das propriedades Físico-Mecânicas de diferentes compósitos Bulk-Fill

The aim of the study was to assess the degree of conversion (DC), microhardness, polymerization shrinkage stress (PSS) and volumetric contraction of two bulk-fill composites (SonicFill, Kerr Corporation, Orange, CA, USA - (SF) and Filtek BulkFill, 3M ESPE, St Paul, MN, USA - (FB)) and one conventional nanofiller resin composite (Z350XT – 3M ESPE, St Paul, MN, USA) inserted incrementally (Z350I) or in bulk (Z350B). Micro-Raman spectroscopy, Knoop microhardness, PSS test and micro-computed tomography technique (?CT) were used to evaluate the resin composites. Data were analyzed with one-way ANOVA followed by Tukey’s post hoc test (? = 0.05). DC was not affected by the type of the composite, excepted when conventional resin composite was inserted in a single increment (p = 0.002). FB and Z350I showed higher microhardness values than Z350B (p = 0,003), while SF showed no statistically significant difference to the other resin composites. No statistical differences were found among the composites regarding to PSS (p = 0.104) and volumetric shrinkage (p = 0.258). Therefore, it can be concluded that bulk-fill and conventional resin composites tested present similar properties. Thus, shorter time required for the use associated with simplified operative technique are considered clinical advantages of bulk-fill composites.

Field-Induced Assembly of sp-sp2 Carbon Sponges.

The formation of macroscale carbon structures characterised by an sp-sp-hybridization is realised by self-assembly in colloidal solutions under an effect of laser irradiation and electromagnetic fields. The sponge-like morphology, sculptured with gold nanoparticles (NPs) was revealed by Scanning Electron Microscopy (SEM) imaging. Full structural and defect characterization of the self-assembled sponges was provided using the micro-Raman spectroscopic technique. The synthesized clusters manifest themselves in the presence of a strong spectral band in the visible range of the photoluminescence spectra that is quite unusual for ordered sp-carbon systems.

Micro-Raman spectroscopy and complementary techniques applied for the analysis of rock art paintings at the archaeological locality La Angostura, lower valley of Chubut River (Patagonia, Argentina)

In this paper, we characterized for the first time the painting materials in rock art panels of the Patagonian archaeological locality La Angostura using a methodological approach that combined micro-Raman spectroscopy, attenuated total reflection Fourier Transform infrared spectroscopy, and X-ray fluorescence spectroscopy. In this way, we obtained detailed information on the red, green, and black pigments as well as on accessory minerals present in the paints. Hematite was the chromophore in the red paintings while celadonite and glauconite were identified in the green motifs. A manganese oxide, presumably pyrolusite, was characterized as the black pigment. The pigment compositions were also compared to those of natural sediments collected along the valley of the Chubut River, but the components of the red and green sediment samples differed from those present in the rock art paints. In the red motifs of two of the rock art panels, a relevant finding was the presence of gypsum and anhydrite as a priming layer of the corrugated rock support onto which the red paints were applied. This revealed a different painting technique in comparison to that at the other analyzed panels of La Angostura where paints were applied as thin layers on a smooth surface of the rock support. As far as we know, this is the first report on the identification of gypsum and anhydrite as components of a preparation layer in Patagonian rock art. This result contributes to the open discussion on the origin and function of calcium sulfate in rock art.

Characterization of contemporary artworks made on photosensitized canvas by means of optical microscopy and micro-Raman spectroscopy techniques

Contemporary artists experimented with a wide range of techniques as it is photography, combined with other materials so as to create images on various surfaces. Nikos Kessanlis (1930–2004), an eminent Greek artist, used photographic and mechanical techniques, involving the application of a photosensitive emulsion on different supports for his artistic creations. This photomechanical technique is called alternative printing.The present study examines a series made by Kessanlis in 1999–2000, composed of eleven panels of photosensitized canvases with the scope to identify the materials used by the artist (canvas, primer, photographic emulsion, protective layer), to understand the artist’s technique and to document the panels overall condition. The series is examined using non-invasive techniques (portable digital optical microscope) and analysis of micro-samples by–micro-Raman spectrometry.Micro-Raman analysis results identified the support, as canvas made by cotton and jute, the primer layer as a combination of titanium white and calcium carbonate and finally the photosensitized layer, as a gelatin silver chloride emulsion. Also further compounds are detected such is silver sulfide, related to the photosensitized emulsion deterioration and soot and lignin, related to the impure environment (air flow inside the metro station) where the series are on display for the last twenty years (Athens metro station).Finally, measurements of air temperature and relative humidity are also performed for a short period near the panels so as to evaluate the environmental conditions of the area. The results have shown extreme daily fluctuations of both factors, characterized by “cycling” that could be related to mechanical and chemical deterioration factors affecting the artwork condition.