Raman Spectroscopy Probe Research Articles

Validation of optimised intracranial spectroscopic probe for instantaneous in-situ monitoring and classification of traumatic brain injury

The development of an optical interface to directly distinguish the brain tissue's biochemistry is the next step in understanding traumatic brain injury (TBI) pathophysiology and the best and most appropriate treatment in cases where in-hospital intracranial access is required. Despite TBI being a globally leading cause of morbidity and mortality in patients under 40, there is still a lack of objective diagnostical tools. Further, given its pathophysiological complexity the majority of treatments provided are purely symptomatic without standardized therapeutic targets. Our tailor-engineered prototype of the intracranial Raman spectroscopy probe (Intra-RSP) is designed to bridge the gap and provide real-time spectroscopic insights to monitor TBI and its evolution as well as identify patient-specific molecular targets for timely intervention. Raman spectroscopy being rapid, label-free and non-destructive, renders it an ideal portable diagnostics tool. In combination with our in-house developed software, using machine learning algorithms for multivariate analysis, the Intra-RSP is shown to accurately differentiate simulated TBI conditions in rat brains from the healthy controls, directly from the brain surface as well as through the rat's skull. Using clinically pre-established methods of cranial entry, the Intra-RSP can be inserted into a 2-piece optimised cranial bolt with integrated focussing and correctly identify a sample in real-life conditions with an accuracy >80 %. To further validate the Intra-RSP's efficiency as a TBI monitoring device, rat brains mildly damaged from inflicted spinal cord injury were found to be correctly classified with 94.5 % accuracy. Through optimization and rigorous in-vivo validation, the Intra-RSP prototype is envisioned to seamlessly integrate into existing standards of neurological care, serving as a minimally invasive, in-situ neuromonitoring tool. This transformative approach has the potential to revolutionize the landscape of neurological care by providing clinicians with unprecedented insights into the nature of brain injuries and fostering targeted, timely and effective therapeutic interventions.

Morphological and Doping Effects on Electrical Conductivity of Aluminum Metal Substrate through Pulsed Electrodeposition Coating of Cu-MWCNT

The demand for more efficient and sustainable electrical systems has driven research in the quest for innovative materials that enhance the properties of electrical conductors. This study investigated the influence of copper (Cu) coating and multi-walled carbon nanotubes (MWCNTs) on aluminum metal substrate through the pulsed electrodeposition technique. Parameters such as the concentration of chemical elements, current, voltage, temperature, time, and electrode spacing were optimized in search of improving the nanocomposite coating. The metallic substrate underwent anodization as surface preparation for coating. Characterization techniques employed included Field Emission Gun—Scanning Electron Microscopy (FEG-SEM) for analyzing coating morphology, Energy-Dispersive X-Ray Spectroscopy (EDS), Raman spectroscopy, and Kelvin probe for obtaining surface electrical conductivity values. Homogeneous dispersion of the Cu-MWCNTs film coating was achieved across the entire surface of the aluminum plate, creating a complex morphology. The doping effect was highlighted by changes in the vibrational characteristics of the nanocomposite, which affected the Raman spectrum dispersion bands. An increase in surface electrical conductivity by ≈52.33% compared to the control sample was obtained. Therefore, these results indicate that the improvement in the material’s electrical properties is intrinsically related to the complex morphology achieved with the adopted Cu-MWCNT nanocomposite coating process.

Oxygen Functional Groups Regulate Cobalt‐Porphyrin Molecular Electrocatalyst for Acidic H2O2 Electrosynthesis at Industrial‐Level Current

AbstractElectrosynthesis of hydrogen peroxide (H2O2) based on proton exchange membrane (PEM) reactor represents a promising approach to industrial‐level H2O2 production, while it is hampered by the lack of high‐efficiency electrocatalysts in acidic medium. Herein, we present a strategy for the specific oxygen functional group (OFG) regulation to promote the H2O2 selectivity up to 92 % in acid on cobalt‐porphyrin molecular assembled with reduced graphene oxide. In situ X‐ray adsorption spectroscopy, in situ Raman spectroscopy and Kelvin probe force microscopy combined with theoretical calculation unravel that different OFGs exert distinctive regulation effects on the electronic structure of Co center through either remote (carboxyl and epoxy) or vicinal (hydroxyl) interaction manners, thus leading to the opposite influences on the promotion in 2e− ORR selectivity. As a consequence, the PEM electrolyzer integrated with the optimized catalyst can continuously and stably produce the high‐concentration of ca. 7 wt % pure H2O2 aqueous solution at 400 mA cm−2 over 200 h with a cell voltage as low as ca. 2.1 V, suggesting the application potential in industrial‐scale H2O2 electrosynthesis.

Oxygen Functional Groups Regulate Cobalt-Porphyrin Molecular Electrocatalyst for Acidic H2O2 Electrosynthesis at Industrial-Level Current.

Electrosynthesis of hydrogen peroxide (H2O2) based on proton exchange membrane (PEM) reactor represents a promising approach to industrial-level H2O2 production, while it is hampered by the lack of high-efficiency electrocatalysts in acidic medium. Herein, we present a strategy for the specific oxygen functional group (OFG) regulation to promote the H2O2 selectivity up to 92 % in acid on cobalt-porphyrin molecular assembled with reduced graphene oxide. In situ X-ray adsorption spectroscopy, in situ Raman spectroscopy and Kelvin probe force microscopy combined with theoretical calculation unravel that different OFGs exert distinctive regulation effects on the electronic structure of Co center through either remote (carboxyl and epoxy) or vicinal (hydroxyl) interaction manners, thus leading to the opposite influences on the promotion in 2e- ORR selectivity. As a consequence, the PEM electrolyzer integrated with the optimized catalyst can continuously and stably produce the high-concentration of ca. 7 wt % pure H2O2 aqueous solution at 400 mA cm-2 over 200 h with a cell voltage as low as ca. 2.1 V, suggesting the application potential in industrial-scale H2O2 electrosynthesis.

Label-Free Fiber-Optic Raman Spectroscopy for Intravascular Coronary Atherosclerosis and Plaque Detection.

The rupture of atherosclerotic plaques remains one of the leading causes of morbidity and mortality worldwide. The plaques have certain pathological characteristics including a fibrous cap, inflammation, and extensive lipid deposition in a lipid core. Various invasive and noninvasive imaging techniques can interrogate structural aspects of atheroma; however, the composition of the lipid core in coronary atherosclerosis and plaques cannot be accurately detected. Fiber-optic Raman spectroscopy has the capability of in vivo rapid and accurate biomarker detection as an emerging omics technology. Previous studies demonstrated that an intravascular Raman spectroscopic technique may assess and manage the therapeutic and medication strategies intraoperatively. The Raman spectral information identified plaque depositions consisting of lipids, triglycerides, and cholesterol esters as the major components by comparing normal region and early plaque formation region with histology. By focusing on the composition of plaques, we could identify the subgroups of plaques accurately and rapidly by Raman spectroscopy. Collectively, this fiber-optic Raman spectroscopy opens up new opportunities for coronary atherosclerosis and plaque detection, which would assist optimal surgical strategy and instant postoperative decision-making. In this paper, we will review the advancement of label-free fiber-optic Raman probe spectroscopy and its applications of coronary atherosclerosis and atherosclerotic plaque detection.

Validating the utility of heavy water (Deuterium Oxide) as a potential Raman spectroscopic probe for identification of antibiotic resistance

The impact of microbial infections is increasing over time, and it is one of the major reasons for death in both developed and developing countries. colistin is considered as the antibiotic of last choice for infections brought by major multidrug-resistant (MDR), gram-negative bacteria such as Enterobacter species, Acinetobacter species, and Pseudomonas aeruginosa. Existing approaches to diagnose these resistant species are relatively slow and take up to 2 to 3 days. In this work, we propose a novel interdisciplinary method based on Raman spectroscopy and heavy water to identify colistin-resistant microbes. Our hypothesis is based on the fact that resistant bacteria will be metabolically active in the culture medium containing antibiotics and heavy water, and these bacteria will take up deuterium instead of hydrogen to newly synthesized lipids and proteins. This effect will generate a ‘C − D’ bond-specific Raman spectral marker. Successful identification of this band in the spectral profile can confirm the presence of colistin-resistant bacteria. We have validated the efficacy of this approach in identifying colistin-resistant bacteria spiked in artificial urine and have compared sensitivity at different bacterial concentrations. Overall findings suggest that heavy water can potentially serve as a suitable Raman probe for identifying metabolically active colistin-resistant bacteria via urine under clinically implementable time and can be used in clinical settings after validation.

A new nanometre resolution method for probing densification ratio at nanoindentation sites in glass: Unravelling discrepancies in the literature

The region of permanent densification beneath a Berkovich indentation imprint in silica glass is investigated using a novel chemical dissolution technique. The use of the similitude regime in sharp indentation testing allows one to record reliable data with a good spatial resolution that makes it possible to deal with low loads (typically below 10 mN) and, more importantly, crack-free imprints. The densified zone dissolves more quickly than the non densified regions. The analysis of the results, along the vertical axis, indicates that the densification zone is rather homogeneous with a steep transition to the non densified zone. The size of the densification zone, with respect to the initial free surface, is estimated to be around two times the maximum penetration depth of the instrumented indentation test. These findings are compared with those obtained by numerical simulations using different constitutive equations from the literature. A very good concordance between Raman spectroscopy and chemical probe results is found for imprints made with no or few cracking events during indentation testing.

Probing electron–phonon coupling in magnetic van der Waals material NiPS3: A non-magnetic site-dilution study

NiPS3 is a van der Waals antiferromagnet which has been shown to exhibit spin-phonon and spin-charge coupling in the antiferromagnetically ordered state below TN = 155 K. It is also a rare Ni-based negative charge-transfer-type insulator with Ni valence in a linear superposition state ψ= αd8+ βd9L−+ γ d10L−2 , where L− is the ligand hole. Here, we study high-quality single-crystals of Ni1−x Zn x PS3 (0 < x < 0.2) using temperature-dependent specific heat and Raman spectroscopy probes. We show that in pristine NiPS3, the phonon mode at 176 cm−1 (P2), associated with the vibrations of Ni ions, exhibits a distinct Fano asymmetry. The Fano resonance is particularly pronounced in the paramagnetic phase above TN, which was further confirmed by temperature dependent Raman data on the Zn-doped crystals. In the Zn-doped crystals, while the magnetism weakens following the mean-field prediction for site-dilution in a honeycomb lattice, the Fano coupling |1/q| strengthens, increasing monotonically with increasing Zn-doping. The x-ray photoemission spectra suggest an increase in the weight of the d9 and d10 components in the Zn-doped crystals. These observations indicate the presence of strong electron–phonon coupling in Ni1−x Zn x PS3, in addition to the spin-phonon, and spin-charge coupling previously reported.

Orientation Dependent Interlayer Coupling in Organic–Inorganic Heterostructures

AbstractOrganic–inorganic 2D heterostructures combine the high optical absorption of organic molecules with exciton‐dominated optical properties in layered transition metal dichalcogenides (TMDs) such as MoS2. Critical to the interaction and the optical response in such hybrid systems is the electronic band alignment at the interface between the two species. Here, the coupling of monolayers of perylene derivatives is investigated with bilayer MoS2. In particular, variation in the perylene orientation on the MoS2 surface is identified using Raman spectroscopy and scanning probe microscopy. Low‐temperature optical spectroscopy reveals orientation‐dependent interlayer exciton formation. Furthermore, power‐dependent photoluminescence measurements provide insight into the modified interlayer charge transfer in these heterostructures. A saturation of interlayer states is found under high excitation power when the perylene molecules are in a perpendicular orientation to the surface that leads to electron accumulation in the MoS2, whereas parallel alignment of the perylene molecules leads to enhanced populations of organic–inorganic interlayer excitons. This work provides insights into the optimization of organic–inorganic heterostructures, with particular relevance to applications for optoelectronic and excitonic devices.

Explaining Color Change in Gem-Quality Andradite Garnet

The homomorphic substitution of the garnet group is common in nature. Two rare color-changing andradite garnets are studied in this paper. One color changes from yellowish-green in the presence of daylight to maroon under incandescent light; the other color changes from brownish yellow to brownish red. In this study, conventional gemological instruments, infrared (IR) spectroscopy, ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy, Raman spectroscopy, and electron probe microanalysis (EPMA) were used to explore the gemology and coloration mechanisms of color-changing garnets. Experiments revealed that the color-changing gemstones in the study are andradite garnets. There are two transmission windows in the UV–Vis spectrum: the red region (above 650 nm) and the green region (centered at 525 nm). The chemical compositional analysis indicates that the samples are very low in Cr (&lt;1 ppm) and high in Fe2+ (from 2.31 wt.% to 4.66 wt.%). The combined spectra and chemical compositional analysis show that Fe2+ is the main cause of the color change. Based on the IR spectrum (complex water peaks), UV–Vis–NIR spectrum (similar to that of Namibian andradite garnet), and chemical compositional analysis (low Cr content), it is concluded that color-changing andradite may be related to skarn rock genesis.

Gemological characteristics and inclusions of green rutilated quartz from Huanggangliang, Inner Mongolia.

Normally, various minerals exist in quartz as inclusions. In this study, methods such as gem microscopy, polarizing microscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and electron probe microanalysis (EPMA) were used to systematically study the gemological characteristics and inclusions in green rutilated quartz from Inner Mongolia. Results show that the sample appears green due to the chaotic distribution of green inclusions in the shape of hair filaments. Combined with the chemical composition, the inclusions are Ca-Fe-rich amphiboles with compositions very close to those of the end-member ferro-actinolite. According to the principle of amphibole nomenclature, the inclusions are named ferro-actinolite in the subclass of calc-alkaline amphiboles with a few named ferro-hornblende. Results suggested that the inclusions in green rutilated quartz were formed during the late stage of quartz crystallization. This work provides a new theoretical basis for the study of green rutilated quartz in Huanggangliang, Inner Mongolia.

Synchrotron-based UV resonance Raman spectroscopy probes size confinement, termination effects, and anharmonicity of carbon atomic wires

Vibrational and electronic properties and anharmonicity of sp-carbon atomic wires (i.e., polyynes) have been studied using resonance Raman spectroscopy, focusing on the confinement effects connected to their structure (length and termination). We exploited the fine tunability of the synchrotron radiation to resonantly excite short H-, CH3-, and CN-capped carbon atomic wires at their vibronic transitions in the deep UV. We report for the first time the resonance Raman spectra of size-selected CH3-capped polyynic wires (HCnCH3, n = 8–12) and CN-capped wires (HC6CN and HC12CN). We observed that the degree of π-electron conjugation increases with the wire length and is related to the specific termination. The analysis of multiple quanta Raman overtone bands shows that the anharmonic correction of the vibrational potential energy becomes increasingly relevant as the wire length increases. Finally, studying the vibronic lines of the UV absorption spectra allows the determination of an effective displacement parameter between the minima of the ground and the low-lying excited state, proving that the strong electron-phonon coupling of these systems is sensitive to chain length and termination.

Phase transformation of Cr(VI) host-mineral driven by citric acid-aided mechanochemical approach for advanced remediation of chromium ore processing residue-contaminated soil

The slow release of Cr(VI) from chromium ore processing residue-contaminated soil (COPR-soil) poses a significant environmental and health risk, yet advanced remediation techniques are still insufficient. Here, the slow-release behavior of Cr(VI) in COPR-soil is observed and attributed to the embedded Cr(VI) in the lattice of vaterite due to the isomeric substitution of CrO42- for CO32-. A citric acid-aided mechanochemical approach with FeS2/ZVI as reductive material was developed and found to be highly effective in remediating COPR-soil. Almost all Cr(VI) in COPR-soil, including Cr(VI) embedded in the minerals, are reduced with a reduction efficiency of 99.94%. Cr(VI) reduction kinetics indicate that the Cr(VI) reduction rate constant in the presence of citric acid was 4.8 times higher compared to its absence. According to the Raman spectroscopy, X-ray diffraction (XRD), and Electron Probe X-ray Micro-Analyzer (EPMA) analysis, the reduction of Cr(VI) embedded in vaterite was mainly attributed to the citric acid-induced protonation effect. That is, under the protonation effect, the embedded Cr(VI) could be released from vaterite through its phase transformation to calcite, whose affinity to Cr(VI) is low. While the reduction of released Cr(VI) could be promoted due to the complexation of citric acid with disulfide groups on FeS2/ZVI. The results of long-term stability tests demonstrated that the remediated COPR-soil exhibited excellent long-term stability, which may also be associated with improved utilization of available carbon and electron donors by the Cr(VI) reducing bacteria (Proteobacteria)-dominated microbial community in the presence of citric acid, thereby promoting to establish a stable reducing microenvironment. Collectively, these findings will further our understanding of the reduction remediation of COPR-soil, especially in the case of Cr(VI) embedded in minerals.

Fabrication and Characterization of Graphene-Barium Titanate-Graphene Layered Capacitors by Spin Coating at Low Processing Temperatures

Barium titanate, BaTiO3 (BT), materials have been synthesized by two different routes. One ball-mill-derived (BMD) nanopowder and another precursor-derived (PCD) BT synthesis method were used separately to fabricate BT thin films on stainless steel (SS) and quartz substrates by spin coating. Then thin films from both synthesis routes were characterized by Ultraviolet-Visible-Near Infrared (UV–vis-NIR) Spectroscopy, Field-Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffractometry (XRD), Raman Spectroscopy, and Four-point collinear probe; all carried out at room temperature. Our studies revealed that the PCD synthesis process did not produce the BT phase even under the 900 °C air-annealing condition. In contrast, a homogeneous BT thin film has been formed from the BMD-BT nanopowder. The optical bandgap of BMD-BT thin films was found in the 3.10–3.31 eV range. Finally, a Graphene-Barium Titanate-Graphene (G-BT-G) structure was fabricated on an SS substrate by spin coating at processing temperatures below 100 °C and characterized by two different pieces of equipment: a Potentiostat/Galvanostat (PG-STAT) and a Precision Impedance Analyzer (PIA). The G-BT-G structure exhibited a capacitance of 8 nF and 7.15 nF, a highest dielectric constant of 800 and 790, and a low dielectric loss of 4.5 and 5, investigated by PG-STAT and PIA equipment, respectively.

Surface‐enhanced Raman spectroscopy investigation of PO43− to Ag/Al2O3 nanopatterned substrates binding and its dynamics for sensitive detection of phosphate in water

AbstractWe provide fast and sensitive detection of phosphate dissolved in water using Raman spectroscopy. To this end, phosphate‐scavenging planar core/shell surface‐enhanced Raman spectroscopy (SERS) probes consisting of Al2O3‐capped Ag nanopatterned sapphire substrate were prepared and optimized. Thanks to scavenging, the probes provide enhancement sufficient to readily detect phosphate at levels occurring in water sources. In particular, the SERS probes were successfully tested for selective detection of all phosphate ions and down to 1 M phosphate concentration (30 g/L of phosphorus in the solution). The novelty of our contribution lies in real‐time SERS monitoring of the phosphate Raman markers, which allowed to study the dynamics of phosphate interaction with the nano‐structured surface of the probes. Under natural conditions (neutral to basic environment), the phosphates adsorb on the probes in form of PO in two steps.

Raman Spectroscopy Fiber Probe Based on Metalens and Multimode Fiber for Malachite Green Determination

The limit of Raman spectroscopy probe based on the traditional objective lens, such as integration difficulties, is the primary motivation to find better alternatives. Due to the potential of vertical integration and significant flexible design, a Raman spectroscopy fiber probe based on metalens at the fiber end facet is demonstrated. Using the "contact and separate" method, we successfully transferred the metalens to the end face of multimode fiber (MMF) to construct the Raman fiber probe with an ultrahigh numerical aperture (NA) of up to 0.66@air. In the case of the surface-enhanced Raman scattering (SERS) substrate composed of Au-plated anodic aluminum oxide (AAO) membrane with the same dry malachite green (MG), compared with the commercial Raman scattering light acquisition system based on an objective lens, our Raman signal intensity increases by at least 2.7 times at the Raman characteristic peak for MG. In the MG aqueous solution, the measurement with a limit of detection (LOD) of 10-9 mol/L@1616 cm-1 is realized. The proposed SERS sensing configuration based on the proposed Raman fiber probe and Au-covered AAO membrane also shows a broad application potential of real-time monitoring for other markers in the fields of food safety and environment detection.

Preclinical evaluation of Raman spectroscopy for pedicular screw insertion surgical guidance in a porcine spine model.

Orthopedic surgery is frequently performed but currently lacks consensus and availability of ideal guidance methods, resulting in high variability of outcomes. Misdirected insertion of surgical instruments can lead to weak anchorage and unreliable fixation along with risk to critical structures including the spinal cord. Current methods for surgical guidance using conventional medical imaging are indirect and time-consuming with unclear advantages. The purpose of this study was to investigate the potential of intraoperative in situ near-infrared Raman spectroscopy (RS) combined with machine learning in guiding pedicular screw insertion in the spine. A portable system equipped with a hand-held RS probe was used to make fingerprint measurements on freshly excised porcine vertebrae, identifying six tissue types: bone, spinal cord, fat, cartilage, ligament, and muscle. Supervised machine learning techniques were used to train-and test on independent hold-out data subsets-a six-class model as well as two-class models engineered to distinguish bone from soft tissue. The two-class models were further tested using in vivo spectral fingerprint measurements made during intra-pedicular drilling in a porcine spine model. The five-class model achieved accuracy in distinguish all six tissue classes when applied onto a hold-out testing data subset. The binary classifier detecting bone versus soft tissue (all soft tissue or spinal cord only) yielded 100% accuracy. When applied onto in vivo measurements performed during interpedicular drilling, the soft tissue detection models correctly detected all spinal canal breaches. We provide a foundation for RS in the orthopedic surgical guidance field. It shows that RS combined with machine learning is a rapid and accurate modality capable of discriminating tissues that are typically encountered in orthopedic procedures, including pedicle screw placement. Future development of integrated RS probes and surgical instruments promises better guidance options for the orthopedic surgeon and better patient outcomes.

Effect of low energy cesium ion irradiation on vanadium oxide: Structural and spectroscopic study

Vanadium di-oxide (VO2) and vanadium tetra oxide (V2O4) powders are exposed to cesium (Cs) ion irradiation using Pelletron accelerator. The energy of the Cs ions ranges from 0.2 keV to 5 keV. Mass spectroscopic data from the accelerator is plotted for various energy ranges. Un-irradiated samples and Cs ion irradiated samples are characterized by using x-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and four-point probe method. XRD analysis showed improved VO2 crystallinity after ion irradiation. The V2O4 sample shows amorphous behavior after ion irradiation. Dislocation density and tolerance are calculated to explore structure distortion after ion irradiation. Raman spectroscopy reveals vibrational and rotational modes of bonding with oxygen and vanadium. SEM results explain the reduction in agglomeration after Cs ion irradiation. The resistivity of un-irradiated and irradiated (VO2 and V2O4) samples is calculated by four-point probe method. The resistivity of vanadium oxide is decreased after Cs ion irradiation to make it a potential candidate for optoelectrical applications.

High-pressure phase of cold-compressed bulk graphite and graphene nanoplatelets

We have studied the high-pressure vibrational and structural behavior of bulk graphite and graphene nanoplatelets at room temperature by means of high-pressure Raman spectroscopic and x-ray diffraction probes. We have detected a clear pressure-induced structural transition in both materials, evidenced by the appearance of new Bragg peaks and Raman features, deviating from the starting hexagonal graphitic structure. The high-pressure phase is identified as a partially disordered orthorhombic structure, consisting of mixed $s{p}^{2}$- and $s{p}^{3}$-type bonding. Our experimental findings serve as direct evidence for the existence of a metastable transient modification in cold compressed carbon, lying between the $s{p}^{2}$-type graphite and ${sp}^{3}$-type diamond allotropes.

Medical image classification in breast sentinel lymph node detection

With the advent of computational imaging technologies, machine learning now provides an essential supporting modeling tool for disease detection. Breast Sentinel Lymph Node detection requires medical image classification from Raman spectral image dataset. This is achieved with a convolutional neural network, a machine learning technique. The current efforts on this literature review aim to explore a branch of deep- learning for the detection of first breast cancerous lymph node from Raman Spectroscopy Probe. With this technique, we evaluate the use of a convolutional neural network, a type of machine learning- based algorithm, used to automatically detect cancer metastases in lymph nodes with high accuracy from trained Raman Spectral Dataset.