Raman Peak Intensity Research Articles

High-precision analysis of carbon isotopic composition for individual CO2 inclusions via Raman spectroscopy to reveal the multiple-stages evolution of CO2- bearing fluids and melts

The carbon isotopic composition of CO2 inclusions trapped in minerals reflects the origin and evolution of CO2-bearing fluids and melts, and records the multiple-stages carbon geodynamic cycle, as CO2 took part in various geological processes widely. However, the practical method for determination isotope composition of individual CO2 inclusion is still lacking. Developing a microanalytical technique with spatial resolution in micrometers to precisely determinate the δ13C value of individual CO2 inclusion, will make it possible to analyze a tiny portion of a zoning mineral crystal, distinguish the differences in micro-scale, and possible to find many useful information that could not be obtained with the bulk extraction and analysis techniques. In this study, we systematically collected Raman spectra of CO2 standards with different δ13C values (−34.9 ‰ to 3.58 ‰) at 32.0 °C and from ∼7.0 MPa to 120.0 MPa, and developed a new procedure to precisely determinate the δ13C value of individual CO2 inclusion. We investigated the relationship among the Raman peak intensity ratio, δ13C value, and CO2 density, and established a calibration model with high accuracy (0.5 ‰−1.5 ‰), sufficient for geological application to distinguish different source of CO2 with varying δ13CO2. As a demonstration, we measured the δ13C values and the density of CO2 inclusions in the growth zones of alkali basalt-hosted corundum megacrysts from Changle, Shandong Province. We found the significant differences of density and δ13C between the CO2 inclusions in the core of corundum and those inclusions in the outer growth zones, the δ13C value decreases from core to rim with decreasing density: δ13C values are from −7.5 ‰ to −9.2 ‰ for the inclusions in the core, indicating the corundum core was crystallized from mantle-derived magmas; from −13.5 ‰ to −18.5 ‰ for CO2 inclusions in zone 1 and from −16.5 ‰ to –22.0 ‰ for inclusions in zone 2, indicating the outer zones of corundum grew in a low δ13C value environment, resulted from an infilling of low δ13C value fluid and/or degassing of the ascending basaltic magma.

Integration of a fused silica capillary and in-situ Raman spectroscopy for investigating CO2 solubility in n-dodecane at near-critical and supercritical conditions of CO2

To determine the solubility of CO 2 in n -dodecane at T = 303.15–353.15 K, P ≤ 11.0 MPa, an integrated fused silica capillary and in-situ Raman spectroscopy system was built. The Raman peak intensity ratio ( I CO 2 / I C - H ) between the upper band of CO 2 Fermi diad ( I CO 2 ) and the C–H stretching band of n -dodecane ( I C - H ) was employed to determine the solubility of CO 2 in n -dodecane based on the calibrated correlation equation between the known CO 2 molality in n -dodecane and the I CO 2 / I C - H ratio with R 2 = 0.9998. The results indicated that the solubility of CO 2 decreased with increasing temperature and increased with increasing pressure. The maximum CO 2 molality (30.7314 mol/kg) was obtained at 303.15 K and 7.00 MPa. Finally, a solubility prediction model ( ln S = ( P − A ) / B ) based on the relationship with temperature ( T in K) and pressure ( P in MPa) was developed, where S is CO 2 molality, A = − 8 × 10 − 6 T 2 + 0.0354 T − 8.1605 , and B = 0.0405 T − 10.756 . The results indicated that the solubilities of CO 2 derived from this model were in good agreement with the experimental data.

Solar-thermal cold-wall chemical vapor deposition reactor design and characterization for graphene synthesis

Manufacturing processes are often highly energy-intensive, even when the energy is primarily used for direct heating processes. The required energy tends to derive from local utilities, which currently employ a blend of sources ranging from fossil fuels to renewable wind and solar photovoltaics, among others, when the end manufacturing need is thermal energy. Direct solar-thermal capture provides a compelling alternative that utilizes renewable energy to reduce greenhouse gas emissions from industrial processes, but one that has rarely been employed to date. In this study, a 10 kWe custom-built high flux solar simulator (HFSS) that closely approximates the solar spectrum produces a heat flux distribution with an adjustable peak between 1.5 and 4.5 MW/m2. The HFSS system is coupled to a cold-wall chemical vapor deposition (CVD) system that is equipped to automate graphene synthesis while providing safe operation, precise control, and real-time monitoring of process parameters. A numerical heat transfer model of a thin copper substrate is derived and validated to compute the substrate’s temperature profile prior to the synthesis process. The peak substrate temperature is correlated to the HFSS supply current and vacuum pressure, as it serves as a critical design parameter during graphene synthesis. We report the synthesis of high-quality graphene films on copper substrates with an average Raman peak intensity ratio ID/IG of 0.17. Backscattered electron microscopy reveals a characteristic grain size of 120 μm, with an area ratio of 16 when compared to that of low-quality graphene on copper. The reported solar-thermal CVD system demonstrates the ability to produce a high-value product, namely, graphene on copper, directly from a renewable energy resource with process control and automation that enables synthesis under a variety of conditions.

Bismuth oxybromide based novel substrate for surface enhanced Raman spectroscopy

Bi24O31Br10 powders were prepared through calcination at 500 ⁰C by chemical precipitation method. Relative Raman peak intensity enhancement after annealing at different temperature was observed along with new characteristic feature that confirm the phase stability of Bi24O31Br10 powders. The as-synthesized sample exhibited excellent SERS activity with rhodamine B (RhB), 4-nitrophenol (4-NP) and methyl orange (MO) as probe molecules. The minimum detectable concentration was 20 µM for RhB, 100 µM for 4-NP and 100 µM for MO. Moreover, the remarkable enhancement was obtained with the ethanol solvent as compared to water for the SERS detection of RhB with 785 nm laser excitation. Multi-molecular detection was also successfully carried out.

Electrical and optical properties and defects of (100)- and (001)-oriented V-doped β-Ga2O3 crystals grown by EFG

Altering the n-type conductivity and optical properties of ultra-wide bandgap β-Ga2O3 by impurity doping has been a topic of research interest in the semiconductor field. Simultaneously, β-Ga2O3 with a monoclinic structure has exhibited interesting anisotropy. In this study, (100) and (001) V-doped β-Ga2O3 crystals were synthesized by the edge-defined film-fed growth (EFG) method, and their structural, electrical and optical properties, and defects were systematically investigated. V-doped β-Ga2O3 crystals with a (100) plane have a better crystalline quality and flatter surface than those with a (001) plane. Compared with undoped crystals (∼1016 cm−3), the carrier concentration of the (100) and (001) V-doped β-Ga2O3 substrates only increased to 4.30 × 1017 cm−3 and 1.92 × 1017 cm−3, respectively, which was related to the VxOy clusters formed by excess V as trapping traps and the carbon DX center as an electron capture trap formed by the relaxation of C atoms in the direction opposite to that of the C–O bond. The generation of absorption peaks and flat regions in the transmittance spectra was attributed to the introduction of V doping. The etch pit morphology and Raman peak intensity on the surfaces of the (100) and (001) V-doped β-Ga2O3 substrates were different owing to the anisotropy of the monoclinic lattice structure. These results contribute to the understanding of the influence of V and anisotropy on β-Ga2O3 crystals and expand their applications in electrical and optical fields.

Enhancement in structural, morphological, and optical properties of copper oxide for optoelectronic device applications

AbstractIn this study, copper oxide (CuO) specimens were successfully prepared by the hydrothermal process at altered calcination temperatures; 350, 450, and 550°C. The synthesized samples were analyzed through X-ray powder diffraction (XRD), scanning electron microscope (SEM), Raman, Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy to analyze the impact of calcination temperature on the structural, morphological, vibration spectra, functional group, and optical properties of CuO for optoelectronic device applications. XRD confirms the pure single-phase monoclinic structure of synthesized samples with no impurity phases and has good crystallinity with the development in calcination temperature. The average crystalline size, lattice constant, and porosity were found in the range of 3.98–5.06 nm;a= 3.4357 Å,b= 3.9902 Å,c= 4.8977 Å – a= 3.0573 Å,b= 3.9573 Å,c= 4.6892 Å; and 3.37–1.03%, respectively. SEM exhibited a variation in morphology by increasing calcination temperature. Raman spectra revealed that the CuO sample calcinated at 550°C with a stone-like shape having a large grain size of 3.25 μm exhibited that Raman peak intensity and the multiphonon band became stronger and sharper and exhibited higher intensity compared to the samples calcinated at 350 and 450°C. FTIR spectra confirmed that these synthesized specimens exhibited the peaks associated with the typical stretching vibrations of the Cu–O bond between 400 and 500 cm−1exhibiting the formation of CuO. The energy bandgap was slightly reduced from 1.61 to 1.43 eV with the increase in the calcination temperature. The optical studies revealed that the calcination temperature of 550°C improves the optical properties of CuO by tuning its optical bandgap. The modified structural, morphological, and optical characteristics of the prepared CuO samples make them an appropriate candidate for optoelectronic device applications.

Oxidation of Cu3N thin films obtained from Cu annealed under NH3:O2 flow: A Raman and N-K-edge NEXAFS study

Cu3N layers prepared by annealing, under NH3:O2 flow, of Cu sputtered on Si, fused SiO2, and soda-lime-glass were studied by Raman and N-K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The annealing temperatures were ranging from 300° to 800°C. Benefiting from resonance effects on the Raman peak intensities when different excitation wavelengths are used, the contribution in the Raman signal of copper oxides, which provide peaks lying close to those of Cu3N, is more easily discriminated. The formation of Cu2O surface oxide is observed in almost all the samples even for annealing at low temperatures. CuO is generally formed at higher temperatures with the onset depending on the amount of O2 in the NH3:O2 mixture. However, high temperature is necessary to grow larger crystallites, as it is deduced from the decrease in the width of the high-frequency Raman peak (at ca. 650 cm−1) of Cu3N, in accordance with Scanning Electron Microscopy observations. The formation of CuO is accompanied by the creation of N2 trapped in the sample, which is directly detected by the NEXAFS measurements. N2 is most probably formed by the N atoms originating from the dissociation of the Cu-N bonds.

Increase the Surface PANI Occupancy of Electrospun PMMA/PANI Fibers: Effect of the Electrospinning Parameters on Surface Segregation.

For preparing high-performance electrospun fibers with functional molecules that cannot cross-entangle themselves, such as conductive polymers, promoting the aggregation of functional molecules on the surface by surface segregation is a promising approach. In the present study, electrospun polymethyl methacrylate/polyaniline (PMMA/PANI) fibers were prepared under various conditions, including solution composition, applied voltage, tip-to-collector distance, temperature, humidity, and gas-phase solvent concentration, to examine the effects of the parameters on fiber morphology and surface segregation. The changes in fiber morphology and variations in the intensity of PANI and PMMA’s characteristic bands were investigated with scanning electron microscopy (SEM) and Raman spectroscopy. The results demonstrated that by changing the saturation difference and the viscosity, the amount of PMMA and PANI added significantly influenced whether surface segregation could occur. The effect of other investigated parameters on surface segregation was concluded to alter the molecular migratable time by affecting the jet flight time and the solvent volatilization rate. Among them, increasing the solvent concentration could significantly promote surface segregation without sacrificing morphological advantages. When the solvent concentration increased from 1.4 to 158 mg/m3, the Raman peak intensity ratio of PANI and PMMA increased from 2.91 to 5.05, while the fiber diameter remained essentially constant.

Deciphering the Heterogeneity of the Internal Environment of Hippocampal Neurons during Maturation by Raman Spectroscopy.

Hippocampal neurons are sensitive to changes in the internal environment and play a significant role in controlling learning, memory, and emotions. A remarkable characteristic of the aging brain is its ability to shift from a state of normal inflammation to excessive inflammation. Various cognitive abilities of the elderly may suffer from serious harm due to the change in the neural environment. Hippocampal neurons may have various subsets involved in controlling their internal environment at different stages of development. Developmental differences may eventually result from complex changes in the dynamic neuronal system brought on by metabolic changes. In this study, we used an in vitro hippocampal neuron model cultured in C57BL/6J mice in conjugation with Raman spectroscopy to examine the relative alterations in potential biomarkers, such as levels of metabolites in the internal environment of hippocampal neurons at various developmental stages. The various differentially expressed genes (DEGs) of hippocampal neurons at various developmental stages were simultaneously screened using bioinformatics, and the biological functions as well as the various regulatory pathways of DEGs were preliminarily analyzed, providing an essential reference for investigating novel therapeutic approaches for diseases that cause cognitive impairment, such as Alzheimer’s disease. A stable hippocampal neuron model was established using the GIBCO C57BL/6J hippocampal neuron cell line as a donor and in vitro hippocampal neuron culture technology. The Raman peak intensities of culture supernatants from the experimental groups incubated for 0, 7, and 14 days in vitro(DIV) were examined. The GEO database was used to screen for different DEGs associated with various developmental stages. The data was then analyzed using a statistical method called orthogonal partial least squares discriminant analysis (OPLS-DA). The levels of ketogenic and glycogenic amino acids (such as tryptophan, phenylalanine, and tyrosine), lipid intake rate, glucose utilization rate, and nucleic acid expression in the internal environment of hippocampal neurons were significantly different in the 14 DIV group compared to the 0 DIV and 7 DIV groups (P < 0.01). The top 10 DEGs with neuronal maturation were screened, and the results were compared to the OPLS-DA model’s analysis of the differential peaks. It was found that different genes involved in maturation can directly relate to changes in the body’s levels of ketogenic and glycogenic amino acids (P < 0.01). The altered expression of the maturation-related genes epidermal growth factor receptor, protein tyrosine kinase 2-beta, discs large MAGUK scaffold protein 2, and Ras protein-specific guanine nucleotide releasing factor 1 may be connected to the altered uptake of ketogenic and glycogenic amino acids and nucleic acids in the internal environment of neurons at different developmental stages. The levels of ketogenic, glycogenic amino acids, and lipid intake increased while glucose utilization decreased, which may be related to mature neurons’ metabolism and energy use. The decline in nucleic acid consumption could be connected to synaptic failure. The Raman spectroscopy fingerprint results of relevant biomarkers in conjugation with multivariable analysis and biological action targets suggested by differential genes interpret the heterogeneity of the internal environment of mature hippocampal neurons in the process of maturation, open a new idea for exploring the dynamic mechanism of the exchange energy metabolism of information molecules in the internal environment of hippocampal neurons, and provide a new method for studying this process.

The role of Os substitution on structural, magnetic, and optical features of LuFeO3

The powders of LuFeO3 and LuFe1-xOsxO3 (x = 0.05 and 0.10) were fabricated by using solid-state technique. The presence of particle agglomeration as well as the porosity of the analyzed materials have been shown via scanning electron microscope (SEM) studies. The oxidation states of the constituted elements in the fabricated samples have been determined with X-ray photoelectron spectroscopy (XPS) studies. It has been realized that the Lu has 3+, Fe accommodates both 2+ and 3+ valence stated in three samples. In addition, the oxidation state of Os has been identified as 4+ in the Os doped samples. It has been demonstrated that the Raman peak intensity of the Os substituted samples declines with Os presence. Furthermore, it has been seen that the peaks shift to lower wavenumber values in the Os doped specimens. Magnetic studies performed via vibrating sample magnetometer (VSM) found that the Os doping increases not only Hc but also Mr values at 10 K and 100 K, yet Hc and Mr values for undoped LFO at 300 K are higher than the Os doped samples. This rise in Hc and Mr values might be attributed to 1) deviations in the tilted angles of Fe3+ moments and 2) the evolution of energy of magnetocrystalline anisotropy. Moreover, the influence of Os doping on the optical band gap of LFO was determined. It exhibited that the optical band gap of LFO increases as the Os doping ratio elevates from 2.19 eV to 2.22 eV.

Raman Effect Studies of Electrochemical Synthesized Quartz Crystal of Poly-O-Phenylenediamine for Piezoelectric Application

Microelectronics arose from the desire for miniaturization of electrical devices, while Nano-electronics arose from subsequent study. Researchers have developed and modeled energy harvesting technologies based on the conservation law of energy over the last two decades to produce an alternative power source for small size electronics (nano-electronics) and low power electronic devices that can replace traditional power sources like batteries. The ambient energy, which is typically in the form of solar, thermal, vibrational, and other types, can be converted into a variety of different forms. Electrical energy can be harvested from vibrational energy in materials and other man-made materials using piezoelectric, electromagnetic, electrostatic, and nano-electric generators. Poly-o-phenylenediamine (PoPD) Quartz (silicon dioxide) Crystals were electrochemically produced at varied percentage ratios of silicon dioxide and Poly-O-Phenylenediamine samples in this study (sample A represents 20:80 percent, sample B with 50:50 percent, and sample C has 60:40 percent respectively). The Raman Effect and Scanning Electron Microscopic (SEM) analysis were used to characterize the material and forecast its Piezoelectric effect. All of the samples have their maximum peak record at Raman shift of 2872cm-1, however the Raman intensity varies. Sample A produced a peak intensity of 1250, Sample B produced a peak intensity of 1700, and Sample C produced a peak intensity of 2700. As the doping concentration of silicon dioxide increases, the Raman peak intensity for Poly-o-Phenylenediamine doped with silicon dioxide increases. The SEM images show that Sample A forms a fine cluster with little or no distinctive morphology, Sample B is ball-shaped with grain-like structure, and Sample C shows a flat, thin leaf-like shape. From sample A to C, the intra-particle separation rises, which corresponds to an increase in SiO2 concentration.

Micro-Raman spectroscopy study of blood samples from myocardial infarction patients

Acute myocardial infarction (MI) is found to be a major causative factor for global mortality and morbidity. This situation demands necessity of developing efficient and rapid diagnostic tools to detect acute MI. Raman spectroscopy is a non-destructive optical diagnostic technique, which has high potential in probing biochemical changes in clinical samples during initiation and progress of diseases. In this work, blood was taken as the sample to examine inflammation in acute MI patients using Raman spectroscopy. Ratio of Raman peak intensities that corresponds to phenylalanine (1000 cm−1) and tyrosine (825 cm−1) can facilitate indirect information about tetrahydrobiopterin (BH4) availability, which can indicate inflammatory status in patients. This ratio obtained was higher for MI patients in comparison with control subjects. The decrease in phenylalanine and tyrosine ratio (Phe-Tyr ratio) is attributed to the prognosis of standard of care (medications like antiplatelets including aspirin, statin and revascularisation) leading to inflammation reduction. Phe-Tyr ratio estimated from the Raman spectra of blood can be exploited as a reliable method to probe inflammation due to MI. The method is highly objective, require only microliters of sample and minimal sample preparation, signifying its clinical utility.

Evolution of the Raman 2D’ mode in monolayer graphene during electrochemical doping

Effective charge doping and control of the Fermi level shift is a crucial aspect in graphene device fabrication. Raman spectroscopy is extensively used for primary characterization of such samples, however, quantification of carrier concentration using the known G-2D vector analysis can pose problems when more sources of phonon renormalization are present, for example lattice deformation or disorder. In such cases, analysis of another Raman mode can provide the needed missing information. In this study, chemical vapor-deposition-grown single-layer graphene was monitored by in-situ Raman spectroelectrochemistry with the focus on the behavior of the 2D’ mode upon the application of electrochemical potential. We analyzed the changes of the Raman peak intensity, frequency and linewidth of the 2D’ mode as a function of electrode potential in detail and compared the obtained results with well-known behavior of the G and 2D modes during electrochemical doping.

Evaluating the performance of multilayer perceptron algorithm for tuberculosis disease Raman data

In spite of developments in various molecular approaches, major challenges remain in rapidly diagnosing infectious diseases triggered by bacteria. Identification of such causative pathogens at an earlier stage and with an acceptable degree of sensitivity and specificity would play a major role in initiating proper treatment. In this study the performance of multilayer perceptron (MLP) algorithm on the Raman Spectroscopic data of tuberculosis disease have been evaluated. Blood sera samples of TB positive (active patients), TB negative (recovered) and control (healthy) are analyzed in current study. Classifications among the data sets are based on the differences/similarities in Raman peak intensity. The analysis has been carried out by using MLP, a class of artificial neural network algorithm. The results of these classifications are built on intensities of most dominated Raman peaks i.e. 1001, 1152, 1282, 1430, 1475, and 1690cm−1. These Raman shifts are attributed to biomolecules concentration such as phenylalanine, β-carotene, amide III and C=O of amide-I band of protein etc. The performance of the proposed model is evaluated using 5-fold cross validation method for the data sets i.e. control vs. TB positive, control vs. TB negative and TB positive vs. TB negative. The sensitivity and specificity predicted by the model is in the range of 62-92% and 81-88%, respectively. Once trained on known data set, Raman spectroscopy together with statistical algorithms can provide real time prediction for unknown samples.

Co substituted Ni–Zn ferrites with tunable dielectric and magnetic response for high-frequency applications

Microwave ferrites are the most promising materials for high frequency and high-power devices. In this work, Co substituted Ni–Zn ferrites (Ni0.5-xZn0.5CoxFe2O4; x = 0–0.4) are synthesized, and the structural, morphology, dielectric, magnetic response are systematically investigated. The X-ray diffraction pattern (XRD) pattern confirmed the formation of pristine cubic phase alone without any secondary phase in all the samples. Substitution of Co2+ resulted in increased crystallite size and lattice constant. Raman peak intensity is suppressed, and a shift towards a lower wavenumber is observed with Co substitution. The change in position and intensity is analyzed and attributed to the change in cationic distribution in tetrahedral and octahedral positions by deconvoluting the Raman peaks. The Energy-dispersive X-ray spectroscopy (EDAX) analysis confirms the stoichiometry of compounds. The real permittivity and tan δ are decreased with the dilution of Co (x = 0: ε' = 24, tan δ = 0.015; x = 0.4: ε' = 11, tan δ = 0.035 @ 1 MHz). Further, permeability initially increased in the X band frequency range and decreased with increasing Co concentration. An increase in the saturation magnetization was observed initially with increased Co content and a decrease after x = 0.2. A maximum saturation magnetization (Ms = 63.3 emu/g) observed for x = 0.2 composition. Interestingly, a giant coercivity and high effective magnetocrystalline anisotropy are observed with the incorporation of Co at low temperatures (5 K). The low dielectric loss, high saturation magnetization, and low coercivity at room temperature of Co substituted Ni–Zn ferrites suggest that these compounds are potential candidates for high-frequency devices (circulators).

Nanomaterial-Embedded DNA Films on 2D Frames.

Recently, 3D printing has provided opportunities for designing complex structures with ease. These printed structures can serve as molds for complex materials such as DNA and cetyltrimethylammonium chloride (CTMA)-modified DNA that have easily tunable functionalities via the embedding of various nanomaterials such as ions, nanoparticles, fluorophores, and proteins. Herein, we develop a simple and efficient method for constructing DNA flat and curved films containing water-soluble/thermochromatic dyes and di/trivalent ions and CTMA-modified DNA films embedded with organic light-emitting molecules (OLEM) with the aid of 2D/3D frames made by a 3D printer. We study the Raman spectra, current, and resistance of Cu2+-doped and Tb3+-doped DNA films and the photoluminescence of OLEM-embedded CTMA-modified DNA films to better understand the optoelectric characteristics of the samples. Compared to pristine DNA, ion-doped DNA films show noticeable variation of Raman peak intensities, which might be due to the interaction between the ion and phosphate backbone of DNA and the intercalation of ions in DNA base pairs. As expected, ion-doped DNA films show an increase of current with an increase in bias voltage. Because of the presence of metallic ions, DNA films with embedded ions showed relatively larger current than pristine DNA. The photoluminescent emission peaks of CTMA-modified DNA films with OLEMRed, OLEMGreen, and OLEMBlue were obtained at the wavelengths of 610, 515, and 469 nm, respectively. Finally, CIE color coordinates produced from CTMA-modified DNA films with different OLEM color types were plotted in color space. It may be feasible to produce multilayered DNA films as well. If so, multilayered DNA films embedded with different color dyes, ions, fluorescent materials, nanoparticles, proteins, and drug molecules could be used to realize multifunctional physical devices such as energy harvesting and chemo-bio sensors in the near future.

In-situ characterization of porcine fibroblasts in response to silver ions by Raman spectroscopy and liquid scanning transmission electron microscopy

Since silver ion is known for its antimicrobial function, most of the research has focused mainly on toxicity effects rather than the role of silver ion in general biology and the behind mechanism of actions of silver ion in mammalian cells. Moreover, a conventional in vitro approach to estimate the effects of silver ion on cells does not provide information about the biochemical changes and might accompany artifacts due to invasive and destructive sample preparation processes. In the present study, in-situ real time approaches were applied to evaluate the impact of silver ion (0.57, 1.34, 1.96, 2.33 mg/L) on fibroblast cells. Raman spectroscopy analysis showed that Raman peak intensities of proteins and nucleic acids significantly increased in the cells after exposure to silver ion for 21 h, especially at relatively higher levels 1.34, 1.96, and 2.33 mg/L. Raman peak at 1585 cm−1 and liquid scanning transmission electron microscopy energy-dispersive x-ray spectroscopy (STEM-EDS) analysis revealed the fate of silver ion that was taken up by the cell and reduced into metallic silver accumulating in the cell as silver nanoparticles. These results suggest cells were undergoing different activities such as enhanced metabolic activities rather than cell apoptosis or cell death. Additionally, Raman spectroscopy predicted the level of silver ion exposed to the cell at 2.11 ± 0.38 and 1.73 ± 0.26 mg/L by the PLS prediction model, compared with the results measured by inductively coupled plasma mass spectrometry (ICP-MS), 2.14 ± 0.07 and 1.87 ± 0.07 mg/L respectively, suggesting Raman spectroscopy can provide a new and fast approach to determine and measure the concentration of silver ion or probably other tested molecules treated to the cell for the future research.

Punicalagin inhibits biofilm formation and virulence gene expression of Vibrioparahaemolyticus

Vibrio parahaemolyticus is a major food-borne pathogen and the leading cause of seafood-associated enteric infections worldwide. In addition, imprudent use of antibiotics has contributed to increasing antibiotic resistance in V. parahaemolyticus. Therefore, there is an urgent need to develop novel control strategies to reduce V. parahaemolyticus contamination and infection. V. parahaemolyticus could form biofilm on different surfaces and contains several virulence factors, which together contribute to its persistence and pathogenicity. In this study, anti-biofilm and potential anti-virulence effects of punicalagin against V. parahaemolyticus were investigated. Punicalagin at sub-inhibitory concentrations (3.125–12.5 μg/mL) exerted significant anti-biofilm activity (20.9–74.4% reduction). It decreased bacterial motility, and attenuated metabolic activity of cells inside biofilm. Meanwhile, punicalagin inhibited EPS production and caused reduction of exopolysaccharides in biofilms, and decreased Raman peak intensities of different biofilm components. Moreover, punicalagin significantly inhibited V. parahaemolyticus adhesion to Caco-2 cells (23.8–68.1% reduction) and downregulated expression of genes involved in V. parahaemolyticus biofilm formation and virulence. These findings suggest that punicalagin could be potentially developed as an alternative strategy to control V. parahaemolyticus biofilms in food industry and mitigate diseases caused by this pathogen.

2D scanning SERS probe for early biofilm boundary determination

Surface-enhanced Raman scattering (SERS) enables the biofilm detection by the characteristic Raman spectrum of extracellular polymeric substance (EPS). However, its clinical application in wound biofilm delineation is hindered by long sampling time and unpredictable sampling errors. To overcome these limitations, we propose a two dimensional (2D) scanning SERS probe that combines the advantages of galvo mirrors and a custom designed SERS active substrate. In this design, the SERS active substrate with dendritic nano-silver structure is fixed on the focal plane of the scan lens to maintain not only the required distance of the sampling plane but also the stable sampling condition as the excitation laser beam driven by the galvo mirrors scans quickly over the region of interest (ROI). Our benchtop study shows that the ± 3.75 mm offset between the sampling plane and the focal plane results in less than 10% change in both laser spot size and fluctuation in Raman peak intensity for the 2D scanning SERS probe, superior to the commercial Raman probe where 1700% change in laser spot size and 95% fluctuation in Raman peak intensity. Our in vitro study in two typical biofilms shows that the 2D SERS scanning probe can detect the biofilm as early as 4 h of cultivation and delineate the biofilm boundary with accuracy at 8 h of cultivation. Furthermore, this substrate is disposable, antibacterial, and capable of enhancing Raman intensity with consistency. Our studies imply the clinical potential of using the 2D SERS scanning probe for biofilm delineation in chronic wound management.

Silver nanostructure on ablated silicon wafer prepared via pulsed laser ablation for surface enhanced Raman spectroscopy

AbstractWe propose and develop a simple and cost‐effective method to fabricate surface enhanced Raman scattering (SERS) substrates for the trace detection of antibiotics. A nanostructured silicon (Si) surface is prepared by the pulsed laser ablation (PLA) of a Si wafer in distilled water. Silver nanoparticles (AgNPs) synthesized via PLA in distilled water are deposited on the ablated Si surface to form a SERS substrate (AgNP/aSi). Malachite green (MG) is used as a probe analyte to examine the SERS activity of the AgNP/aSi substrate. The AgNP/aSi substrate can yield an SERS spectrum of MG with high resolution at a minimum concentration of 0.01 ppm. Using the AgNP/aSi substrate, we investigate its capacity for detecting tetracycline (TC) residue in shrimp. The Raman peak intensities at 1320 cm−1 for TC concentrations from 10 to 0.1 ppm show a linear relationship with the corresponding logarithmic concentrations. Our simple and efficient method can be used for the trace detection of MG, TC, and other antibiotics in various applications via SERS.