Raman Spectral Measurements Research Articles

Self-powered solar-blind ultrafast UV-C diamond detectors with asymmetric Schottky contacts

Single-crystal chemical vapour deposition (CVD) diamond samples with asymmetric Schottky contacts were used for the fabrication of vertical metal-semiconductor-metal detectors for deep ultraviolet (UV–C) radiation. Spectral photoconductivity measurements, performed in the 190 ÷ 1100 nm wavelength range, returned an ultraviolet-to-visible (UV/Vis) rejection ratio of 6.8 × 103 under photovoltaic operating conditions, ensuring solar blindness and zero power consumption at the same time. When applying bias, UV/Vis rejection ratio reached excellent values (>104) even at very low electric fields (0.01 V/μm), thanks to the excellent structural quality and the superior charge transport properties of the diamond bulk, as inferred from Raman analysis and spectral photoconductivity measurements. Mobility-lifetime (μτ) product of the photogenerated carriers was indeed measured to be about 5 × 10−3 cm2/V in the case of holes, which is the highest room-temperature μτ value ever reported for CVD diamond, enabling a response speed in the nanosecond range even at zero-bias operating conditions.

Optical, electrical, and catalytic (photo-and sono-) properties of indium doped γ-Bi2O3 with Sillenite structure

The exotic structure and properties exhibited by the metastable solids are exemplified adequately in the materials chemistry area. In this report, metastable γ-Bi2O3 has been stabilized without adding any impurity by the auto-combustion method and compared with the changes in structure and optical property brought out by the inclusion of In3+ ions. Compositions doped with indium (7 and 10 mol% in place of bismuth) resulted in stoichiometric Sillenite-type structures as revealed by their powder X-ray diffraction patterns, FTIR, and Raman spectral measurements. The pale yellow γ-Bi2O3 acquired pale brown coloration on indium inclusion, and the intensities varied with varying indium content. Optical bandgap reduction from 2.63 (pure γ-Bi2O3) to 2.41 eV occurred when 10 mol% of indium was doped in place of bismuth. The formation of non-stoichiometric Sillenite structures was noticed in samples with higher indium concentrations (up to 50 mol%). The non-stoichiometric samples displayed intense brown color and showed a drastic reduction in the optical bandgap, reaching values as low as 1.57 eV (50 mol% indium doped sample). From XPS analysis and red-ox titrations, nearly 5% of oxygen excess was estimated for the non-stoichiometric samples doped with indium. The BET surface area of indium doped non-stoichiometric Sillenites (126 m2/g) was higher than indium doped stoichiometric Sillenites (74 m2/g). The oxygen ion conductivity studies of pure γ-Bi2O3 and indium doped non-stoichiometric Sillenites revealed a marginal rise in conductivity with indium inclusion.

Synthetic routes and vibrational analysis of 5-(4-Chlorophenyl) -3H-pyrazol-3-one molecule: Raman, Infrared and DFT calculations

5-(4-Chlorophenyl) -3H-pyrazol-3-one (CPP) has been synthesized by the reaction of 2-(piperidin-1-yl)acetamide, p-chlorobenzaldehyde and hydrazine hydrate. Structural characterizations were achieved by means of Mass, 1HNMR (0–20 ppm), 13CNMR (0–200 ppm), IR (3500–400 cm−1) and Raman (3500–100 cm−1) spectral measurements. In addition, the regioselectivity of the above synthetic route / mechanistic path was investigated using B3LYP/6–311++G(2d,p) DFT calculations, which is supported by frontier molecular orbital (FMO), olecular lectrostatic otential (MEP) and natural bond orbital (NBO) analysis. Good agreement between the theoretical analysis and experimental synthetic route has been achieved. Molecular interactions, charge delocalization and electrophilic/nucleophilic sites within the reactant species have been also investigated. CPP can undergo internal rotation around C-C single bond; hence it could be either planar or non-planar configurations. Aided by Density Functional Theory (DFT) optimizations implementing a tight convergence criteria, vibrational frequencies and potential energy surface scan were carried out using B3LYP/6–311++G(2d,p), in favor of planar configuration while a saddle point was obtained for the non-planar geometry. A complete vibrational interpretations were proposed herein, assisted by normal coordinate analysis (NCA) and Potential Energy Distributions (PEDs). Finally, global reactivity descriptors; ionization potential (IP), electron affinity (EA), electronegativity (χ), chemical potential (µ), chemical hardness (η), and electrophilicity index were also calculated and found well correlated to the chemical reactivity of the reactant molecules.

Intra-operative Raman spectroscopy and ex vivo Raman mapping for assessment of cartilage degradation

The development of a label-free, non-destructive and safe analytical method such as Raman spectroscopy for assessing cartilage degradation is highly desirable. Compared to non-optical imaging modalities, Raman mapping offers a more sensitive means of directly assessing the chemical composition of cartilage in three-dimensional space and the potential to monitor cartilage degeneration to inform intervention and treatment strategies. Herein, we report the application of Raman spectroscopic methods ex vivo and at arthroscopy to identify molecular alterations in cartilage specimens containing minor focal lesions characteristic of the early disease phase. Our initial ex vivo analysis, obtained by single-point Raman spectroscopy of cartilage samples, supports previous findings based on S-O stretching vibration bands associated with sulphated glycosaminoglycans (sGAGs). We extended the analyses to the high-wavenumber region where we observed that vibrational bands assigned to C-H and O-H stretching modes discriminated early cartilage alterations from healthy cartilage samples. Furthermore, we performed a proof-of-concept in-clinic study using a custom-built optical probe to acquire Raman spectral measurements for the first time in patients undergoing arthroscopy of knee joints. Spectra were obtained with adequate signal-to-noise ratios that similarly discriminated between lesion and adjacent cartilage sites and identified reductions in sGAGs in apparently healthy cartilage. Building on this, we present initial results from Raman mapping to spatially resolve the molecular constituents of cartilage through its depth and across a lesion. Mapping revealed a non-uniform and reduced sGAG distribution within the lesion and peripheral cartilage that was otherwise visually normal, similar to the in-clinic observations, showing that the degradative influence of the lesion extended beyond its border. This was accompanied by a decreased fluorescence signal intensity, which suggests that fluorescence may provide valuable information as an adjunct to the Raman signal in discriminating normal and degenerating cartilage. This work demonstrates the value of Raman mapping over single-point Raman measurements for the analysis of the anisotropy of articular cartilage and highlights the potential of the technology for in vivo articular joint arthroscopy applications.

Carbon and nitrogen co-doped WO3 as sonocatalyst

The calcination of a mixture of ammonium para tungstate and graphitic C3N4 (10:1 by weight) in flowing nitrogen atmosphere resulted in blue colored products. The powder X-ray diffraction patterns of the calcined products at 350 and 450 °C contained diffraction peaks related to hexagonal and orthorhombic WO3, respectively. The microscopy and Raman spectral measurements reaffirmed these observations. The X-ray photoelectron spectral analysis of hexagonal and orthorhombic WO3 samples indicated carbon and nitrogen-doped in them, causing the reduction of W6+ to W5+ to a smaller extent. The concentration of carbon and nitrogen in these samples were also independently verified by combustion-based elemental analysis. The hexagonal WO3 showed a higher optical bandgap (2.77 eV) than the orthorhombic WO3 (2.58 eV). Both the samples were EPR active, originating from the singly ionized oxygen (paramagnetic) vacancies. The concentration of oxygen vacancies was higher in hexagonal WO3 than orthorhombic WO3. While both these samples were mesoporous, hexagonal WO3 exhibited almost double the surface area than orthorhombic WO3. We evaluated these WO3 samples as catalysts to degrade cationic and anionic dye aqueous solutions oxidatively under ultrasonic conditions. The hexagonal WO3, in general, facilitated higher amounts of degradation of both rhodamine B and methyl orange dye solutions under the influence of sonic waves. The efficiency of orthorhombic WO3 to degrade both these dye solutions was substantially lower. There was no change in the structure of catalysts after their use. A possible mechanism operative in the oxidative degradation of dye solutions is outlined. Correlation between the higher concentrations of oxygen vacancies with higher catalytic capacity is deduced. The catalytic reactions were found to follow pseudo-first-order kinetics.

Raman spectral probed electron–phonon coupling and phonon lifetime properties of Ni-doped CuO nanoparticles

In the present report, optical and Raman spectral properties were extensively studied. Ni-doped CuO nanoparticles were prepared using the sol–gel method. X-ray diffraction patterns confirm that the prepared particles have the space group of C2h6 with monoclinic structure. Optical studies show that there is a broad absorption spectrum in the whole visible regime due to surface plasmon oscillations (SPR). Raman spectral measurements taken using 532 nm excitation found that three Raman peaks centred at 276 cm−1 (Ag), 330 cm−1 (Bg) and 616 cm−1 (Bg), respectively. Doping of Ni ions shows a redshift in Raman peak position. In the present work, the influence of Ni doping on electron–phonon coupling and phonon lifetimes has been studied extensively.

Antimony substitution leading to structural transformation (Bixbyite→ Fluorite) and altering the optical band gap in Y2O3

The transformation of ordered bixbyite structured Y2O3 to cation disordered fluorite structure is demonstrated by antimony substitution in the present work. The samples are prepared by the wet chemical method and characterized by employing various physicochemical techniques. The superstructure reflections of bixbyite were observed for samples prepared with 10 mol% of antimony, beyond which the structure transformed into a disordered fluorite structure. The diffracted peaks became broad in the powder X-ray diffraction pattern with increasing antimony concentration. The Williamson-Hall analysis indicated compressive strain in antimony substituted samples. Microscopy and Raman spectral measurements confirmed this structural transformation. The antimony existed in the III oxidation state, as revealed by XPS measurements. The optical bandgap of Y2O3 changed from 4.81 to 3.62, and 3.20 eV for 20 and 50 mol% antimony substituted samples. In the photoluminescence emission spectrum, the transitions of the excited Jahn-Teller state of Sb3+ are observed in the visible region. 50 mol% antimony substituted yttria sample catalyzed the complete degradation of aqueous rhodamine-6G (Rh-6G) in 105 min, assisted by the UV–visible radiation. The reaction followed pseudo-first-order kinetics, and the catalyst showed nearly the same efficiency up to five times of its reuse. The recovered catalyst did not undergo any change in its structure.

Raman spectroscopy study of acetonitrile at low temperature.

We report the low-temperature studies of liquid CH3CN by Raman spectral measurements at ambient pressure with decreasing the temperature from 20 to -196°C. Detailed internal modes especially the lattice modes analysis revealed that the structural phase transitions of acetonitrile from liquid to solid phase β and solid phase β to solid phase α were occurring at -50 and -60°C, respectively. Further, the Fermi resonance parameters between the fundamental ν2 and combination (ν3+ν4) of CH3CN at different temperatures were calculated based on the Bertran's equations. It is found that the Fermi resonance parameters as a function of temperature become discontinued at -50 and -60°C, which coincides with discontinuities observed in the Raman shifts of CH3CN at -50 and -60°C. The results suggest that the Fermi resonance parameters could be used as an indicator to assess the structural phase transition for CH3CN under low temperature.

Data consistency and classification model transferability across biomedical Raman spectroscopy systems

AbstractSurgical guidance applications using Raman spectroscopy are being developed at a rapid pace in oncology to ensure safe and complete tumor resection during surgery. Clinical translation of these approaches relies on the acquisition of large spectral and histopathological data sets to train classification models. Data calibration must ensure compatibility across Raman systems and predictive model transferability to allow multi‐centric studies to be conducted. This paper addresses issues relating to Raman measurement standardization by first comparing Raman spectral measurements made on an optical phantom and acquired with nine distinct point probe systems and one wide‐field imaging instrument. Data standardization method led to normalized root‐mean‐square deviations between instruments of 2%. A classification model discriminating between white and gray matter was trained with one point probe system. When used to classify independent data sets acquired with the other systems, model predictions led to >95% accuracy, preliminarily demonstrating model transferability across different biomedical Raman spectroscopy instruments.

Brush Printing Creates Polarized Green Fluorescence: 3D Orientation Mapping and Stochastic Analysis of Conductive Polymer Films.

Brush printing is a unique method used to obtain uniaxially oriented films, whereby a polymer solution is brushed onto a substrate. However, there have been only a few reports on the brush-printing method. Here, we report the preparation of a uniaxially oriented film of a green light-emitting conductive polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). The fluorescence polarization ratio of the oriented F8BT films was as high as 11.3, and the average orientation factor reached 0.74 ± 0.06. The orientation factor and the torsion angle of F8BT were visualized by two mappings of fluorescence and Raman spectral measurements by confocal spectromicroscopy, respectively. These two x-y mapping data with many pixels (∼750 pixels) were evaluated by x-y-z mapping of the film thickness at a single position and were used to reveal the three-dimensional (3D) orientation mechanism from a stochastic approach. Polarized green fluorescence originates from polymer chains uniaxially oriented along the brush direction. The high orientation for a film thickness < 100 nm is established by shear stress, faster capillary flow, and flow-induced chain extension for a thin solution film on a substrate. The high orientation factor was also demonstrated by a high brushing speed, whereas an optimized brushing speed existed. We found that this optimization is attributed to the property of a non-Newtonian fluid. By applying this brush-printing method to the fabrication of an optoelectrical device, polarized green electroluminescence was preliminarily demonstrated by the OLED assembled from an oriented F8BT film.

Oxygen-doping of ZnIn2S4 nanosheets towards boosted photocatalytic CO2 reduction

Oxygen-doped ZnI 2 S 4 nanosheets were synthesized by a one-pot solvothermal method and exhibited excellent photocatalytic activity for visible-light photocatalytic CO 2 reduction to CO. Engineering the electronic properties of semiconductor-based photocatalysts using elemental doping is an effective approach to improve their catalytic activity. Nevertheless, there still remain contradictions regarding the role of the dopants played in photocatalysis. Herein, ultrathin ZnIn 2 S 4 (ZIS) nanosheets with oxygen doping were synthesized by a one-pot solvothermal method. XRD, XPS and Raman spectral measurements support the presence of lattice oxygen in the oxygen-doped ZIS (O–ZIS) sample. With optimum doping of oxygen, the ultrathin O–ZIS nanosheets show enhanced CO 2 -to-CO conversion activity with a CO-evolving rate of 1680 μmol h −1 g −1 under visible light irradiation, which is about 7 times higher than that of the pristine ZIS. First-principle calculations support that doping of oxygen in the lattice of ZnI 2 S 4 nanosheets plays a key role in tuning its electronic properties. The remarkable photocatalytic performance of O–ZIS can be assigned to a synergistic consequence of a unique ultrathin-layered structure and an upward shift of the conduction band minimum (CBM) caused by the oxygen doping into ZIS and the quantum confinement effect (QCE) induced by the decreased particle size after doping as well as to the improved charge separation efficiency. The present work offers a simple elemental doping method to promote charge separation at atomic level and illustrates the roles played by oxygen doping in photocatalysis, giving new insights into highly efficient artificial photosynthesis.

Helix-Sense-Selective Synthesis of Right- and Left-Handed Helical Luminescent Poly(diphenylacetylene)s with Memory of the Macromolecular Helicity and Their Helical Structures.

Symmetrically substituted poly(diphenylacetylene) (PDPA) bearing carboxy pendants was found to fold into a one-handed helix upon thermal annealing with nonracemic amines in water accompanied by chiral amplification of the helicity. The induced right- or left-handed helical PDPA was retained (memorized) after complete removal of the chiral amines, thus producing a one-handed helical circularly polarized luminescent PDPA in a helix-sense-selective manner. The helical PDPA with static helicity memory is tolerant toward modification of carboxy pendants, providing functional PDPAs with an optical activity solely due to macromolecular helicity. The PDPA and its derivatives before and after the one-handed helicity induction and its subsequent memory of the helicity exhibited well-resolved very simple 1H and 13C NMR and Raman spectra whose spectral patterns are virtually identical independent of the helical sense bias. On the basis of the 1H and 13C NMR, IR, Raman, and vibrational and electronic circular dichroism spectral measurement results combined with theoretical calculations, the key structural features (cis or trans and cisoid or transoid) of the PDPA as well as its helix inversion barrier and absolute handedness (right- or left-handed helix) and helix-sense excess of the one-handed helical PDPA and its derivatives with static helicity memory were determined. As a result, almost complete right- and left-handed helical cis-transoidal PDPAs with 98% helix-sense excess were successfully obtained using noncovalent helicity induction and memory strategy.

Understanding the effects of culture conditions in bacterial growth: A biochemical perspective using Raman microscopy.

Rapid, sensitive and label-free methods to probe bacterial growth irrespective of the culture conditions can shed light on the mechanisms by which bacteria adapt to different environmental stimuli. Raman spectroscopy can rapidly and continuously monitor the growth of bacteria under varied conditions. In this study, the growth of Escherichia coli in Luria broth (nutrient rich conditions) and minimal media with either glucose or glycerol as carbon source (nutrient limiting conditions) is profiled using Raman spectroscopy. Moreover, the study also gives insights into the altered bacterial biochemistry upon exposure to low- (25°C) and high-temperature (45°C) stress. Raman spectral measurement was performed on bulk bacteria cultured under laboratory conditions. A detailed analysis of the spectra as a function of bacterial growth reveals changes in Raman band intensities/area of biomolecules such as DNA, proteins and lipids. We also report five novel ratiometric markers (I830 /I810 , I1126 /I1100 , I1340 /I1440 , I1207 /I1240 and I1580 /I1440 ) that can identify the phase of growth, independent of the culture condition. Unsupervised multivariate methods like Principal Component Analysis also corroborate the aforementioned markers of growth. Altogether, our findings highlight the potential of Raman spectroscopy in yielding universal biochemical signatures that may be indicative of stress and aging in a growth milieu.

Structural and Magnetic Properties of Gd-Ni-co-doped BiFeO₃ Nanoparticles

Single-phase (GdNi)SUBx/SUB(BiFe)SUB1-x/SUB O₃ (x = 0, 0.025, and 0.05) nanoparticles of 30-40 nm particle size on average were fabricated using a sol-gel method. Transmission electron microscopy, X-ray diffraction as well as Raman spectral measurements and analyses revealed that the (GdNi)SUBx/SUB(BiFe)SUB1-x/SUBO₃ nanoparticles undergo a structural transformation from the rhombohedral R3c structure (for x = 0 and 0.025) to the triclinic P1 (for x = 0.05). X-ray photoemission spectroscopy served to confirm that co-doping of GdSUP3+/SUP and NiSUP2+/SUP ions decreases oxygen-vacancy concentration, reflecting less FeSUP2+/SUP content in the co-doped samples compared with pure BiFeO₃. Magnetization hysteresis loops showed that the magnetization value for x = 0.05 at 50 kOe increases significantly to M = 5.32 emu/g at 300 K and to 14.47 emu/g at 5 K, representing 760 and 690 % enhancements relative to those for x = 0. Fitting of the Curie-Weiss law to the observed magnetization-versus-temperature curves indicated the presence of weak ferromagnetic coupling in the samples. We also noted the exchange bias effect in the nano-size particles, possibly originating from exchange coupling between surface spins of an uncompensated ferromagnetic nature and core spins of an antiferromagnetic nature. We ascribed these significant improvements in the Gd-Ni-co-doped BiFeO₃ nanoparticles’ magnetic properties to the rhombohedral R3c to triclinic P1 structural transformation, due to the samples’ particle size being smaller than the modulation length of the canted antiferromagnetic ordering of the FeSUP3+/SUP spins. These enhanced magnetic properties, notably, might prove useful for a variety of spintronic applications.

A calibrated database of Raman spectra for natural silicate glasses: implications for modelling melt physical properties

AbstractThe physical properties of silicate melts are of critical importance for understanding magmatic and volcanic processes on Earth and other planets. Most physical properties of melts are, ultimately, a consequence of the structural organization of the melt. Robust and fully generalizable strategies for the prediction of properties of naturally occurring melts as functions of composition, temperature, and pressure remain a challenging goal. Given the structural origin of macroscopic properties, Raman spectroscopy of glasses, which provides information on melt and glass structure, may provide a useful technique to understanding and quantify variations in macroscopic melt properties. Here, with the aim of providing a generalizable model for predicting the viscosity of silicate melts, we present the results of a Raman spectroscopy campaign performed on 30 anhydrous multicomponent silicate glasses resulting from quenching of remelted and homogenized volcanic rocks and synthetic equivalents. The sample suite comprises one of the largest databases of multicomponent melts for which (a) chemical compositions and (b) physical properties (i.e., viscosity, fragility, heat capacity, and glass transition temperature) are known. Raman spectra have been collected using green light sources at wavelengths of 532 nm. Spectra were collected on the same sample suite in four independent laboratories involving instruments from different manufacturers and, thus, using different spectrometers, detectors, and analytical conditions. Our results are also compared and integrated with published data on some of the same samples derived from two others setups using green light sources with 514.5 and 532 nm wavelegths. For the same sample, the Raman spectra acquired using different setups show different intensities and intensity ratios. However, a strategy based on the ratio between the low‐ and high‐wavenumber peaks (R) was developed to standardize the data to normalized Raman ratios (Rn) and thus to remove interlaboratory differences. Using these advances, we predict melt viscosity solely with the use of Raman spectral measurements of multicomponent silicate glasses, thus demonstrating the potential of the method in describing physical properties of silicate melts.

Nondestructive Identification and Accurate Isolation of Single Cells through a Chip with Raman Optical Tweezers.

Raman optical tweezers (ROT) as a label-free technique plays an important role in single-cell study such as heterogeneity of tumor and microbial cells. Herein we designed a chip utilizing ROT to isolate a specific single cell. The chip was made from a polydimethylsiloxane (PDMS) slab and formed into a gourd-shaped reservoir with a connected channel on a cover glass. On the chip an individual cell could be isolated from a cell crowd and then extracted with ∼0.5 μL of phosphate-buffered saline (PBS) via pipet immediately after Raman spectral measurements of the same cell. As verification, we separated four different type of cells including BGC823 gastric cancer cells, erythrocytes, lymphocytes, and E. coli cells and quantifiably characterized the heterogeneity of the cancer cells, leukocyte subtype, and erythrocyte status, respectively. The average time of identifying and isolating a specific cell was 3 min. Cell morphology comparison and viability tests showed that the successful rate of single-cell isolation was about 90%. Thus, we believe our platform could further couple other single-cell techniques such as single-cell sequencing and become a multiperspective analytical approach at the level of a single cell.

Development of a flow cell based Raman spectroscopy technique to overcome photodegradation in human blood.

Raman spectroscopy of blood offers significant potential for label-free diagnostics of disease. However, current techniques are limited by the use of low laser power to avoid photodegradation of blood; this translates to a low signal to noise ratio in the Raman spectra. We developed a novel flow cell based Raman spectroscopy technique that provides reproducible Raman spectra with a high signal to noise ratio and low data acquisition time while ensuring a short dwell time in the laser spot to avoid photodamage in blood lysates. We show that our novel setup is capable of detecting minute changes in blood lysate spectral features from natural aging. Moreover, we demonstrate that by rigorously controlling the experimental conditions, the aging effect due to natural oxidation does not confound the Raman spectral measurements and that blood treated with hydrogen peroxide to induce oxidative stress can be discriminated from normal blood with a high accuracy of greater than 90% demonstrating potential for use in a clinical setting.

Consequences of lead incorporation in fluorite structured thoria

Abstract The outcome of incorporation of lead in fluorite structured thoria in terms of structure and electrical properties have been discussed. Samples with stoichiometries Th1-xPbxO2-δ (x = 0.00 to 0.70) have been synthesized by a solution combustion route and characterized extensively. The maximum solubility limit of lead in fluorite structured thoria was deduced to be 50 mol % from powder X-ray diffraction and Raman spectral measurements. The micro strain of the fluorite lattice increased with the introduction of lead. X-ray photoelectron spectroscopy analysis of Th0·50Pb0·50O2-δ showed the existence of lead in both +2 and + 4 oxidation states. The ratio between the intensities of peaks located at 548 cm−1 and T2g mode (I548/IT2g) was found to increase with increase in lead content in the samples and quantified utilizing grain size and half width half maxima. The defect concentrations in these samples have been estimated in the range 1017-1020 cm−3. The direct band gap values shifted from the insulating regime (for thoria) to semiconducting regime (3.4–2 eV) for lead substituted samples. From the frequency dependent conductivity plots of Th1-xPbxO2-δ samples over temperature range (323–773 K), highest conductivity of 1.62 × 10−6 Scm−1 was obtained for Th0·50Pb0·50O2-δ at 773 K. From the impedance measurements of lead substituted thoria under flowing oxygen (1 atm), thermal motion of oxygen ion vacancies was found responsible for the observed conductivity.

Near-infrared-light-induced decomposition of Rhodamine B triggered by localized surface plasmon at gold square dimers with well-defined separation distance

Localized surface plasmon-induced photoreactions at metal nanostructures have become central research topics in biology, catalysis, and analytical chemistry. In particular, the decomposition of organic pollutants is a popular topic. Rhodamine B is useful in the dye industry and biology; however, it is harmful to humans and the environment. In this study, we investigated the decomposition of the Rhodamine B molecule with a structurally well-defined array of gold square dimers. The array of gold square dimers was fabricated by electron beam lithography, which provided a homogenous well-defined reaction field. Continuous Raman spectral measurements using a near-infrared laser clearly showed that while the Rhodamine B molecules were stable in the absence of the gold square dimers, they were decomposed under near-infrared-light irradiation.

Cryopreservation of proteins in aqueous DMSO solutions at cryogenic temperature: A case study of lysozyme

The glass-forming concentration and the cooling effect of aqueous DMSO solutions at various concentrations X (mol%DMSO) on protein state were investigated using Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy along with differential thermal analysis (DTA) to obtain fundamental information on storage of recombinant protein at cryogenic temperature. DTA and Raman spectral measurements showed that the aqueous DMSO solutions with lysozyme formed the glassy state at X = 15–60. Activity and structural stability of lysozyme in aqueous DMSO solutions before and after cooling exhibited small change up to X = 0–30. Thus, the DMSO concentration at X = 15–30 was found to be a suitable condition for lysozyme storage at cryogenic temperature. The cryopreservation ability of aqueous DMSO solutions for lysozyme was observed to be strongly associated with the glassy solution structure that inhibits protein unfolding and aggregation. The present findings may serve as basic information regarding the appropriate experimental conditions for DMSO solutions to be employed as a suitable cryoprotectant for various recombinant proteins.