Analysis Of Absorption Spectra Research Articles

Studies of Ultrafast Molecular Dynamics by Femtosecond Extreme Ultraviolet Absorption Spectroscopy

Transient absorption spectroscopy is one of the most widely used experimental techniques for time-resolved studies of ultrafast phenomena. Recent advances in the generation of short-wavelength pulses of ultrashort duration have made transient absorption probing of atomic core level transitions possible. In this Highlight Review, we introduce our recent work on using extreme ultraviolet (XUV) transient absorption spectroscopy to investigate the ultrafast molecular dynamics induced by intense laser fields. While investigations of intense laser-molecule interaction have primarily focused on elucidating electron dynamics, it is important to understand the vibrational dynamics that are triggered by intense laser fields because of their coupling to electron dynamics. Probing the iodine 4d core level, our XUV transient absorption studies of iodoalkanes irradiated by intense laser fields elucidate ultrafast dissociative ionization dynamics and vibrational wave packet dynamics. Time-dependent XUV spectral shifts and global analysis of time-resolved XUV transient absorption spectra can be used to reconstruct C–I dissociation dynamics and identify multiple dissociation channels. In addition, XUV transient absorption spectroscopy also unravels both small- and large-amplitude coherent vibrational motion, whose origin can be identified by analyzing the phase of the oscillatory XUV transition energies. Our studies show that XUV transient absorption spectroscopy is a powerful technique for the study of ultrafast molecular dynamics.

Bis-triazole with indole pendant Organosilicon framework: Probe for recognition of Pb2+ ions

Trace lead (II) ions detection platform by adjoining an indole group, bis-triazole molecules and a silatranyl motif, has been proposed in this article. The receptor has been prepared by employing click chemistry methodology and the hybrid network was successfully identified by elemental analysis, IR and NMR (1H, 13C) spectroscopy. Absorption spectra analysis marked that the sensor exhibit an exclusively fastidious response to Pb2+ ions with a measured detection limit of 0.032µM at 1:1 stiochiometry. Further, computational studies have been carried out to get an insight into their structure and properties.

Novel lignin-based single atom catalysts as peroxymonosulfate activator for pollutants degradation: Role of single cobalt and electron transfer pathway

In this work, a facile one-pot pyrolytic strategy was employed to fabricate a nitrogen coordinated Co single-atom catalyst (SA Co-N/C catalyst) by using lignin as carbon sources. The HAADF-STEM images and X-ray absorption spectra (XAS) analysis showed the isolated Co atoms less than 2 Å throughout the entire SA Co-N/C architecture. Results showed that the single-atom Co sites served as the main active sites for naproxen (NPX) degradation via peroxymonosulfate (PMS) activation. This was confirmed by the high positive correlation (R2 = 0.9675) between the rate constants and Co amounts in all SA Co-N/C catalysts. In particular, the as-prepared SA Co-N/C catalyst with a very small Co loading (2.45 wt.%) exhibited exceptional high turnover frequency (TOF) value for NPX (4.82 min−1), which is promising for the potential application prospect. Electron transfer was induced by the single-atom Co sites, which was the dominated mechanism for the NPX degradation.

Antibodies purification from human plasma using fractionation, chromatography and gel electrophoresis assisted by multivariate analysis of complimentary absorption and fluorescence spectra

Employing simple precipitation (fractionation) using Cohn method and weak anion exchange chromatography with DEAE resin, antibodies such as Immunoglobulin G are purified from human plasma. Fractions are eluted from column in four different regions depending on washing NaCl concentrations. Absorbance and excitation-emission fluorescence spectral data are measured for separated chromatographic fractions and analyzed using Multivariate Curve Resolution- Alternating Least Squares (MCR-ALS) and Parallel Factor Analysis (PARAFAC) techniques. Resolved concentration and spectral profiles provided information about existing components in each fraction. Protein and non-protein components are distinguished considering their resolved pure spectra and information from the two applied spectroscopic techniques is complementary. A number of components displayed both fluorescence and absorbance signals. When concentration of component (protein or non-protein) in sample is low and no significant absorbance signal is observed, sensitive fluorescence is useful to recognize the component and for non-fluorescent components absorbance spectra are utilized. Electrophoresis is utilized for separation of proteins in each fraction and showed that one distinguished protein from fluorescence and/or absorbance data can be a group of proteins with similar pure spectra and retention volume. Results showed presence of two protein in the first region (IgM and IgA), a group of proteins in second region (IgM, α-globulin, and IgG), a pure protein in third region (IgG), and a group of β-globulin proteins in fifth region. It is well and clearly shown that multivariate analysis of different data sets with complementary information is necessary for better interpretation of such technically simple and biochemically complicated systems.

Computational study of IR, Raman, and NMR spectra of 4-methylmethcathinone drug.

Molecular electronic structure, IR, UV, and NMR spectra of the most popular cathinone, known as mephedrone or 4-methylmethcathinone (4-MMC), is studied thoroughly by quantum chemical calculation in terms of the density functional theory (DFT). Geometry optimization of 4-MMC and its hydrochloride complex is performed with the B3LYP functional, and all vibrational frequencies are analyzed in all details. On this background, the IR and Raman spectra are interpreted. The importance of low-frequency terahertz and Raman spectra is stressed for distinguishing of various MMC isomers. The UV spectrum is calculated by time-dependent DFT method which allows complete interpretation of intense absorption bands at 270 and 210nm as combinations of various ππ*, nπ*, and charge transfer excitations in amino-phenyl moieties. Very informative analysis of UV absorption and NMR spectra provides useful details on the structure-activity relationship for mephedrone molecule.

Functional properties of quaternary metals (1 − x)ZnMn2O4/(x)MgFe2O4 as supercapacitor electrode

Solid solutions from $$(1-x){\mathrm{ZnMn}}_{2}{\mathrm{O}}_{4}/(x){\mathrm{MgFe}}_{2}{\mathrm{O}}_{4}$$ (x = 0.0, 0.1, 0.5, 0.9, 1.0) were obtained by a simple sol–gel procedure. A single-phase tetragonal spinel zinc manganite was identified by X-ray phase analysis for the samples x = 0.0 and 0.1, whereas a single-phase cubic spinel magnesium ferrite was identified for x = 0.5, 0.9, and 1.0. The formation of these phases was confirmed by the analysis of FTIR absorption spectra measured for the obtained samples. A scanning electron microscope was used to identify the different elements in the formed solid solution. Transmission electron microscope together with Rietveld profile method emphasized the nano-nature of the obtained samples. The influence of the composition parameter (x) on the optical properties of the solid solutions was explored utilizing UV–Vis diffuse reflectance spectroscopy measurements. The magnetic measurements revealed the conversion of the paramagnetic nature of ZnMn2O4 samples into ferromagnetic nature as it couples with MgFe2O4 sample in $$(1-x){\mathrm{ZnMn}}_{2}{\mathrm{O}}_{4}/(x){\mathrm{MgFe}}_{2}{\mathrm{O}}_{4}$$ solid solution. The supercapacitor performance of all samples was examined by cyclic voltammetry and galvanostatic charge–discharge studies.

Critical Addition Point-Based Trace Sensing of Hg²+ Through Surface Plasma Polaritons Properties Analysis of Ag Nanoparticles

In this work, we synthesize and functionalize Ag nanoparticles (NPs) with Sodium tripolyphosphate in one pot. Due to $\text{P}_{3}\,\,\text{O}_{10}^{5-}$ _AgNPs aggregation in the presence of mercury, colorimetric detection with naked eye realize, the limit of detection is $1~\mu $ mol $\cdot \text{L}^{-1}$ . Based on one critical additional point with $3~\mu $ mol $\cdot \text{L}^{-1}$ of Hg2+ added, trace sensing of mercury can be performed through absorption spectra analysis, the limit of detection reaches 1nmol $\cdot \text{L}^{-1}$ . The TEM image and EDS test tell the mechanism, where the aggregating behavior of $\text{P}_{3}\text{O}_{10}^{5-}$ _AgNPs in the presence of Hg2+ is different from that of Cr3+ and Mn2+. Also, this method possesses high selectivity. This work may pave a facile way in mercury detection sensors.

Wavemeter Capable of Simultaneously Achieving Ultra-High Resolution and Broad Bandwidth by Using Rayleigh Speckle From Single Mode Fiber

Rayleigh speckle with random jagged pattern resulting from the interference of Rayleigh backscattering lightwave in a single-mode fiber contains the wavelength information of the incident lightwave. We propose an all-fiber wavemeter based on the relation between Rayleigh speckle and wavelength. The system does not suffer from the resolution-bandwidth trade-off relation and simultaneously achieves an ultra-high resolution of 40 attometers and a broad bandwidth of 80 nm covering 1520 to 1600 nm. The wavemeter could enable precise measurement of continuous-wave optical waveforms at time resolution of 100 μs. Combined with a dynamic laser, the system can be regarded as a high-resolution spectroscopy for absorption spectrum analysis. To demonstrate the broad applicability of the technique, we use a laser step-scanned over 80 nm to measure the spectral response of hydrogen cyanide absorption line, and use a continuous-wave laser to measure its nonlinear wavelength scan over 1 nm. The proposed all-fiber wavemeter provides great prospects for ultra-precise spectrum analysis with ultra-broad bandwidth and ultra-high resolution.

Multistep Changes in Amyloid Structure Induced by Cross-Seeding on a Rugged Energy Landscape

Amyloid fibrils are aberrant protein aggregates associated with various amyloidoses and neurodegenerative diseases. It is recently indicated that structural diversity of amyloid fibrils often results in different pathological phenotypes, including cytotoxicity and infectivity. The diverse structures are predicted to propagate by seed-dependent growth, which is one of the characteristic properties of amyloid fibrils. However, much remains unknown regarding how exactly the amyloid structures are inherited to subsequent generations by seeding reaction. Here, we investigated the behaviors of self- and cross-seeding of amyloid fibrils of human and bovine insulin in terms of thioflavin T fluorescence, morphology, secondary structure, and iodine staining. Insulin amyloid fibrils exhibited different structures, depending on species, each of which replicated in self-seeding. In contrast, gradual structural changes were observed in cross-seeding, and a new type of amyloid structure with distinct morphology and cytotoxicity was formed when human insulin was seeded with bovine insulin seeds. Remarkably, iodine staining tracked changes in amyloid structure sensitively, and singular value decomposition analysis of the ultraviolet-visible absorption spectra of the fibril-bound iodine has revealed the presence of one or more intermediate metastable states during the structural changes. From these findings, we propose a propagation scheme with multistep structural changes in cross-seeding between two heterologous proteins, which is accounted for as a consequence of the rugged energy landscape of amyloid formation.

Optimization of in-line near-infrared measurement for practical real time monitoring of coating weight gain using design of experiments

This study was conducted to develop an in-line near-infrared (NIR) spectroscopy approach that allows real time quantitative analysis of the coating weight gain on a moving tablet surface during a coating process where talc is used. A holder directly inserting a diffuse reflectance probe into a coating pan was designed, and the optimal measurement conditions were identified using the design of experiments (DoE). The surface of the probe was kept clean of coating droplets at a maximum distance between the probe and the holder of 272.5 mm, leading to the acquisition of accurate spectral data. Under this condition, partial least squares regression (PLSR) was developed using the spectra from 7197 to 6233 cm−1, which covers the specific peaks for the core tablet and the coating solution. Under the same conditions, least squares regression (LSR) was developed using the univariate predictive analysis of the single absorption spectrum of talc at 7181 cm−1. In a comparison of the accuracy of the two models, PLSR was found to be more accurate as a result of testing the significance of differences between these distributions in terms of the root mean square errors of prediction (RMSEP) using a randomization t-test. Additionally, it confirmed that the predicted weight gain using NIR spectroscopy was correlated with the coating thickness measured using micro-CT. In conclusion, this study developed an in-line NIR measurement approach for the real-time monitoring of the coating weight gain of tablets and optimized the conditions by evaluating the effect of various factors.

An isolated water droplet in the aqueous solution of a supramolecular tetrahedral cage

Water under nanoconfinement at ambient conditions has exhibited low-dimensional ice formation and liquid-solid phase transitions, but with structural and dynamical signatures that map onto known regions of water's phase diagram. Using terahertz (THz) absorption spectroscopy and ab initio molecular dynamics, we have investigated the ambient water confined in a supramolecular tetrahedral assembly, and determined that a dynamically distinct network of 9 ± 1 water molecules is present within the nanocavity of the host. The low-frequency absorption spectrum and theoretical analysis of the water in the Ga4L612- host demonstrate that the structure and dynamics of the encapsulated droplet is distinct from any known phase of water. A further inference is that the release of the highly unusual encapsulated water droplet creates a strong thermodynamic driver for the high-affinity binding of guests in aqueous solution for the Ga4L612- supramolecular construct.

Ameliorative Effect of Zingiber officinale on Chemical Induced DNA Damage in Rats Using PCR Analysis

Ginger rhizomes have been reportedly used in folk medicine for the management of various ailments. This study, therefore, investigates the ameliorative effect of the ethanolic extract of ginger (Zingiber officinale) rhizomes against DNA damage in rats induced with different carcinogens. Fifteen Wistar rats grouped into 3 of 5 rats per group were used for the study. The first set of blood samples was first collected before the animals were orally treated with heavy metals. After 14 days of induction, the second set of blood was collected. The third phase of blood collection was done after administering an ethanolic extract of Z. officinale for 14 days. The UV wavelength absorption spectrum and conventional PCR analysis were carried out on DNA extracts of all the animals. Cluster analysis of optical density (OD) and PCR data were carried out as well as genomic instability, similarity, and diversity using the best 3 Random Amplified Polymorphic DNA (RAPD) primers. The PCR –DNA concentration analysis showed the Z. officinale extract's ameliorative effect against lead acetate, cadmium chloride, and arsenic trioxide-induced DNA damage with a significant (p < 0.05) reduction in DNA concentration of the treated rats when compared with induced rats. The cluster analysis of optical density values revealed close similarity between the control animals' DNA, a slight similarity with treated animals' DNA, and a significant difference with the induced animal DNA. These results indicated the ameliorative properties of Z. officinale against these heavy metals induced DNA damage in rats.

Study of radiation heat transfer during combustion of liquid fuel in a rectangular channel

An experimental study of radiation heat transfer during combustion of a flammable liquid in a narrow rectangular channel is performed. The emission spectrum of combustion products and the absorption spectrum of butanol-1 are obtained. The case when the temperature of the combustible liquid is lower than the flash point is investigated. A comparative analysis of emission and absorption spectra shows that they do not intersect well, and the radiative heating of the liquid during diffusion flame propagation along the surface cannot be too large.

Symmetry Effects in Photoinduced Electron Transfer in Chlorin-Quinone Dyads: Adiabatic Suppression in the Marcus Inverted Region.

In donor–acceptor dyads undergoing photoinduced electron transfer (PET), a direction or pathway for electron movement is usually dictated by the redox properties and the separation distance between the donor and acceptor subunits, while the effect of symmetry is less recognized. We have designed and synthesized two isomeric donor–acceptor assemblies in which electronic coupling between donor and acceptor is altered by the orbital symmetry control with the reorganization energy and charge transfer exothermicity being kept unchanged. Analysis of the optical absorption and luminescence spectra, supported by the DFT and TD‐DFT calculations, showed that PET in these assemblies corresponds to the Marcus inverted region (MIR) and has larger rate for isomer with weaker electronic coupling. This surprising observation provides the first experimental evidence for theoretically predicted adiabatic suppression of PET in MIR, which unambiguously controlled solely by symmetry.

Temperature-dependent optical and vibrational properties of PtSe2 thin films

PtSe2 has received substantial research attention because of its intriguing physical properties and potential practical applications. In this paper, we investigated the optical properties of bilayer and multilayer PtSe2 thin films through spectroscopic ellipsometry over a spectral range of 0.73–6.42 eV and at temperatures between 4.5 and 500 K. At room temperature, the spectra of refractive index exhibited several anomalous dispersion features below 1000 nm and approached a constant value in the near-infrared frequency range. The thermo-optic coefficients of bilayer and multilayer PtSe2 thin films were (4.31 ± 0.04) × 10−4/K and (–9.20 ± 0.03) × 10−4/K at a wavelength of 1200 nm. Analysis of the optical absorption spectrum at room temperature confirmed that bilayer PtSe2 thin films had an indirect band gap of approximately 0.75 ± 0.01 eV, whereas multilayer PtSe2 thin films exhibited semimetal behavior. The band gap of bilayer PtSe2 thin films increased to 0.83 ± 0.01 eV at 4.5 K because of the suppression of electron–phonon interactions. Furthermore, the frequency shifts of Raman-active Eg and A1g phonon modes of both thin films in the temperature range between 10 and 500 K accorded with the predictions of the anharmonic model. These results provide basic information for the technological development of PtSe2-based optoelectronic and photonic devices at various temperatures.

Optical Properties Study of Polypyrrole doped with TiO2, WO3, Fe2O3 and SnO2 Nanoparticles

The study involves the synthesis of PPy and PPy loaded with various metal oxides TiO2, WO3, Fe2O3, and SnO2 with different ratios by polymerization procedure. The UV-Visible analysis was carried in the wavelength range (300-1100nm) to determine the optical parameters like optical energy gap and optical constants. From the analysis of absorption spectra, the band gaps of polypyrrole undoped are 1.85eV While the samples of PPy/SnO2 composite gained the highest values 2.2eV at weight Percentage (5%) but with PPy/Fe2O3 gained lowest values 1.5eV at weight Percentage (1%).

Effect of Cu, Cr, S Doped TiO2 for Transparent Plastic Bar Reinforced Concrete

In this study, after firing and powdering Cu, Cr, and S with NP-400 TiO2, an NOx removal rate test was performed according to the ISO test method to analyze the photocatalytic reactivity in visible light. The distribution of the photocatalyst and visible light reactivity on the surface of the test specimen were confirmed through SEM (Scanning electron microscope), EDS (Energy dispersive spectroscopy), XRD (X-ray diffraction), UV-visible absorption spectrum and energy band gap tests. The flowability of UHPC (Ultra high performance concrete) slightly decreased due to the increase in the photocatalyst mixing rate, but both J-Ring and L-Box test results showed that there is no problem when concrete is placed. As a result of SEM and EDS tests, good microstructure and peak values were confirmed in the test specimens doped with Cu, and as a result of the XRD test, anatase and rutile peaks were confirmed in the Cu, Cr, and S specimens. In the UV-visible absorption spectrum analysis, it was confirmed that only the specimen doped with Cu maintains a high absorption power of 0.8 up to 700 nm, and the inherent band gaps are reduced to 2.9 eV, thereby increasing the possibility of reaction in visible light. Finally, as a result of the NOx removal test by the ISO test method, about 15.8% was removed for 5 h in the specimen doped with Cu, and the removal efficiency is estimated to be possible up to about 25% when applied with the TPBRC (transparent plastic bar reinforced concrete).

Detection and Characterization of Antibacterial Siderophores Secreted by Endophytic Fungi from Cymbidium aloifolium.

Endophytic fungi from orchid plants are reported to secrete secondary metabolites which include bioactive antimicrobial siderophores. In this study endophytic fungi capable of secreting siderophores were isolated from Cymbidium aloifolium, a medicinal orchid plant. The isolated extracellular siderophores from orchidaceous fungi act as chelating agents forming soluble complexes with Fe3+. The 60% endophytic fungi of Cymbidium aloifolium produced hydroxamate siderophore on CAS agar. The highest siderophore percentage was 57% in Penicillium chrysogenum (CAL1), 49% in Aspergillus sydowii (CAR12), 46% in Aspergillus terreus (CAR14) by CAS liquid assay. The optimum culture parameters for siderophore production were 30 °C, pH 6.5, maltose and ammonium nitrate and the highest resulting siderophore content was 73% in P. chrysogenum. The total protein content of solvent-purified siderophore increased four-fold compared with crude filtrate. The percent Fe3+ scavenged was detected by atomic absorption spectra analysis and the highest scavenging value was 83% by P. chrysogenum. Thin layer chromatography of purified P. chrysogenum siderophore showed a wine-colored spot with Rf value of 0.54. HPLC peaks with Rts of 10.5 and 12.5 min were obtained for iron-free and iron-bound P. chrysogenum siderophore, respectively. The iron-free P. chrysogenum siderophore revealed an exact mass-to-charge ratio (m/z) of 400.46 and iron-bound P. chrysogenum siderophore revealed a m/z of 453.35. The solvent-extracted siderophores inhibited the virulent plant pathogens Ralstonia solanacearum, that causes bacterial wilt in groundnut and Xanthomonas oryzae pv. oryzae which causes bacterial blight disease in rice. Thus, bioactive siderophore-producing endophytic P. chrysogenum can be exploited in the form of formulations for development of resistance against other phytopathogens in crop plants.

A Universal Graphene Quantum Dot Tethering Design Strategy to Synthesize Single-Atom Catalysts.

A general graphene quantum dot-tethering design strategy to synthesize single-atom catalysts (SACs) is presented. The strategy is applicable to different metals (Cr, Mn, Fe, Co, Ni, Cu, and Zn) and supports (0D carbon nanosphere, 1D carbon nanotube, 2D graphene nanosheet, and 3D graphite foam) with the metal loading of 3.0-4.5 wt %. The direct transmission electron microscopy imaging and X-ray absorption spectra analyses confirm the atomic dispersed metal in carbon supports. Our study reveals that the abundant oxygenated groups for complexing metal ions and the rich defective sites for incorporating nitrogen are essential to realize the synthesis of SACs. Furthermore, the carbon nanotube supported Ni SACs exhibits high electrocatalytic activity for CO2 reduction with nearly 100 % CO selectivity. This universal strategy is expected to open up new research avenues to produce SACs for diverse electrocatalytic applications.

A Universal Graphene Quantum Dot Tethering Design Strategy to Synthesize Single‐Atom Catalysts

AbstractA general graphene quantum dot‐tethering design strategy to synthesize single‐atom catalysts (SACs) is presented. The strategy is applicable to different metals (Cr, Mn, Fe, Co, Ni, Cu, and Zn) and supports (0D carbon nanosphere, 1D carbon nanotube, 2D graphene nanosheet, and 3D graphite foam) with the metal loading of 3.0–4.5 wt %. The direct transmission electron microscopy imaging and X‐ray absorption spectra analyses confirm the atomic dispersed metal in carbon supports. Our study reveals that the abundant oxygenated groups for complexing metal ions and the rich defective sites for incorporating nitrogen are essential to realize the synthesis of SACs. Furthermore, the carbon nanotube supported Ni SACs exhibits high electrocatalytic activity for CO2 reduction with nearly 100 % CO selectivity. This universal strategy is expected to open up new research avenues to produce SACs for diverse electrocatalytic applications.