Spectroscopic Characters Research Articles

Electron tunneling spectroscopy of an anisotropic Kitaev quantum spin liquid sandwiched between superconductors

We present the electron tunneling transport and spectroscopic characters of a superconducting (SC) Josephson junction with a barrier of a single anisotropic Kitaev quantum spin liquid (QSL) layer. We find that the dynamical spin-correlation features are well reflected in the direct-current differential conductance $d{I}^{c}/dV$ of single-particle tunneling, including the unique spin gap and dressed itinerant Majorana dispersive band, in addition to an energy shift $2\mathrm{\ensuremath{\Delta}}$ from the two-SC-lead gap. From the spectral characters, we identify different topological quantum phases of the anisotropic Kitaev QSL. We also present the zero-voltage Josephson current ${I}^{s}$, which displays residual features of the anisotropic Kitaev QSL. These results pave a new path to measurement of dynamical spinon or Majorana fermion spectroscopy of Kitaev and other spin-liquid materials.

New Insights into Coloration Mechanism in Violet-Red Pyrope-Almandine

The most common type of garnet is pyrope-almandine, whose color varies from red to violet. In this study, 36 faceted gem-quality samples are used for electron microprobe, infrared spectrum, and UV-Visible spectrum test to find the coloration mechanism and spectroscopic characters in red-violet pyrope-almandine. The gradually increasing content of Mg2+ at the X position in the lattice is connected to the variation in the infrared spectrum. The wavenumber increases with the decrease of cationic radius, which makes the distance between C and D bands further. The color mechanism is mainly affected by Fe2+, and Mn2+. We discuss the change in colors with the assumption of a certain MnO content. When it is above or below the standard of 1 wt%, the absorption intensity of the UV-Visible spectrum is completely different in the purple zone, which determines the color to be red or violet. Therefore, the effect of Mn2+ and Fe2+ should be combined instead of being considered respectively. The results show that the MnO content can be quickly inferred by the light purple/fancy purple color. To avoid harming the value, this new insight makes it possible to quickly classify the gem quality in mining as well as in the market.

Seasonal and diurnal variation of PM2.5 HULIS over Xi'an in Northwest China: Optical properties, chemical functional group, and relationship with reactive oxygen species (ROS)

Humic-like substances (HULIS) in particulate matter (PM) play critical roles in the atmospheric changes in our environment. In this study, high time resolution PM2.5 samples were collected to insight the abundances, spectroscopic characters, chemical groups, and oxidative potential of HULIS in Xi'an, China. The average mass concentrations of HULIS in term of carbon (HULIS-C) was 11.55 ± 5.85 and 8.28 ± 2.23 μg C m−3 in winter and summer, respectively. The diurnal variations of HULIS displayed three peaks (03:00–07:00, 10:00–14:00, and 18:00–21:00 LT) in winter, but a single peak (08:00–12:00 LT) in summer. The optical parameters show obvious difference between winter and summer. Fourier Transform infrared (FT-IR) spectra revealed that the HULIS mainly consisted of aliphatic chains, aromatic rings, and carboxylic groups. The FT-IR spectra proved that the aromatic compounds and carboxylic acids dominated the diurnal variation in winter, while carboxylic acids were responsible for that in summer. The normalized oxidative potential of HULIS exhibited an inverse trend with the HULIS-C concentration measured by the DCFH assay. The diurnal reactive oxygen species (ROS) productions from HULIS presents three valleys (03:00–07:00, 10:00–14:00, and 18:00–21:00 LT) in winter but only a single valley (08:00–12:00 LT) in summer. In addition, a positive correlation (R2 ≈ 0.6, p＜0.01) between the oxidative potential and specific ultraviolet absorbance at a wavelength of 254 nm (SUVA254) in winter suggested that the oxidative power of HULIS could be more related to the compounds with high light absorbance, high aromaticity, and molecular weight. The results of this study offer more solid knowledge on the spectral and chemical characteristics and oxidative potential of the HULIS in PM2.5 of the typical city in northwest China.

Nigella Sativa-Coated Hydroxyapatite Scaffolds: Synergetic Cues to Stimulate Myoblasts Differentiation and Offset Infections.

At present osteoporosis has come into view as a major health concern. Skeletal diseases typified by weak and fragile bones have imposed threats of fissure. Hydroxyapatite (HAP) is known to induce osteoblast like differentiation and provide mechanical strength, hence, used in bone tissue engineering; whereas, Nigella sativa has also demonstrated potential to treat bone and muscle diseases. This study was aimed to develop potential orthopedic scaffold exploiting natural resources of Saudi Arabia which can be used as prospective tissue engineering implant. The bone scaffold was developed by grafting biogenic HAP with N. sativa essential oil. N. sativa was applied for boosting osteogenesis and to stimulate antimicrobial potential. Antimicrobial potential was investigated utilizing S. aureus bacteria. Spectroscopic and surface characters of N. sativa grafted HAP scaffolds were analyzed using Fourier-transform infrared spectroscopy, X-ray crystallography and Scanning electron microscopy. To ensure biocompatibility of scaffolds; we selected C2C12 cell-lines; best model to study mechanistic pathways related to osteoblasts and myoblasts differentiation. Grafting of HAP with N. sativa did not affect typical spherical silhouette of nanoparticles. Characteristically; protein loaded polynucleated myotubes are result of in vitro myogenesis of C2C12 myoblasts in squat serum environment. It is first study of unique combination of N. sativa and HAP scaffold as a possible candidate of implantation for skeletal muscles regeneration. Outcome of this finding revealed N. sativa grafted HAP enhance differentiation significantly over that of HAP. The proposed scaffold will be an economical natural material for hard and soft tissue engineering and will aid in curing skeletal muscle diseases. Our findings have implications for treatment of muscular/bone diseases.

Preparation of yeast mediated semiconductor nanoparticles by Candida albicans and its bactericidal potential against Salmonella typhi and Staphylococcus aureus

Biosynthesis of nanoparticles using microorganism is widely used in biological applications due to its eco-friendly nature and lower cost. The present study aimed to investigate the yeast, Candida albicans for the synthesis of nano cadmium sulfide is a semiconductor nanoparticle. The yeast synthesized nanoparticles tested for its spectroscopic and microscopic characters. The peak at 420 nm identified by UV-Vis spectrophotometer confirms the Cadmium sulfide (CdS) nanoparticles synthesis preliminarily. Further, the nanoparticles were characterized using X-ray diffraction assay, scanning electron microscope, and elemental dispersive analysis. Finally, the synthesized Cadmium sulfide (CdS) nanoparticles were tested for its antibacterial activity against disease-causing pathogens such as Salmonella typhi and Staphylococcus aureus. The maximum zone of inhibition shows 15mm at the concentration of 100µl of CdS nanoparticle. Thus a promising antibacterial activity of yeast mediated synthesized Cadmium sulfide (CdS) nanoparticles was described.

Photoinduced relaxation dynamics of nitrogen-capped silicon nanoclusters: a TD-DFT study

ABSTRACTHerein we have developed and implemented a TD-DFT-based surface-hopping dynamics simulation method with a recently proposed numerical algorithm capable of efficiently computing nonadiabatic couplings, a semiclassical spectrum simulation method, and an excited-state character analysis method based on one-electron transition density matrix. With the use of these developed methods, we have studied the spectroscopic properties, excited-state characters, and photoinduced relaxation dynamics of three silicon nanoclusters capped with different chromophores (Cl@SiQD, Car@SiQD, Azo@SiQD). Spectroscopically, the main absorption peak is visibly red-shifted from Cl@SiQD via Car@SiQD to Azo@SiQD. In contrast to Cl@SiQD and Car@SiQD, there are two peaks observed in Azo@SiQD. Mechanistically, the excited-state relaxation to the lowest S1 excited singlet state is ultrafast in Cl@SiQD, which is less than 190 fs and without involving excited-state trapping. In comparison, there are clear excited-state trappings in Car@SiQD and Azo@SiQD. In the former, the S2 state is trapped more than 300 fs; in the latter, the S3 excited-state trapping is more than 615 fs. These results demonstrate that the interfacial interaction has significant influences on the spectroscopic properties and excited-state relaxation dynamics. The knowledge gained in this work could be helpful for the design of silicon nanoclusters with better photoluminescence performance.

A new size-expanded RNA alphabet: Computational design of benzo-homologated (xtz-) isothiazole RNA and comparisons to the x-thieno RNA

Fluorescent nucleobase analogs are of great interest because of their widespread applications in nucleic acids research. In the present work, a new benzo-homologated RNA alphabet comprising xtzA, xtzG, xtzC, and xtzU was computationally designed based on the isomorphic tz-bases. The structural, electronic, and photophysical properties are studied by means of DFT and TDDFT calculations, and the effects of water solution, ribose, and base pairing on the singlet excited transitions were examined. The results are compared with those for tz-bases and xth-bases. These new base analogs can form stable Watson-Crick base pairs with natural counterparts as tz-bases and xth-bases do. Their ionization potentials and HOMO-LUMO gaps are in the middle of tz-bases and xth-bases: xth-base < xtz-base < tz-base. Furthermore, all xtz-bases are predicted to have smaller IPs and HOMO-LUMO gaps than natural bases and tz-bases, they are suggested to be candidates for applications in nanowire technology. The S1 states for all xtz-bases are revealed to be ππ* dominated by the configuration HOMO→LUMO. In water solution, compared with tz- or xth-bases, the lowest ππ* states are about 20.06–21.91kcal/mol red-shifted or 0.92–4.15kcal/mol blue-shifted, respectively. Linking to ribose has negligible effects on the S1 excitation energies, but it owns a larger impact on the corresponding oscillator strengths. Base pairing and water solution as a whole has very little effects on the S1 transition energies of xtzA and xtzC, but it will red-shift those for xtzG and xtzU by 6.69 and 5.30kcal/mol, respectively. All xtz-bases are expected to display visible fluorescence with the wavelengths predicted to be 540, 585, 524, and 506nm for xtzA, xtzG, xtzC and xtzU, respectively, in water solution. Though structurally very similar, the excitation maxima and fluorescence emissions of xtz- and xth-bases show distinct differences, allowing them to be distinguished from each other by their spectroscopic characters

Temperature-Dependent Self-Assembly/Disassembly of Gold Nanoparticles Oligomers.

Precisely controlling Au plasmonic coupling aggregates is of fundamental importance for tuning spectroscopic characters, and also is an effective way of access to practical devices. In our present study, we report a new type of amphiphilic gold nanoparticles (AuNPs) with the surfaces modified by thermo-responsive polymer brushes via sequential "grafting to" and "grafting from" reactions. This novel AuNPs can spontaneously self-assemble into AuNPs oligomers such as dimmers and trimmers by taking advantage of the molecular chain reorganization of polymer brushes. Interestingly, AuNPs oligomers can be reversibly disassembled into individually isolated AuNPs by changing temperature. These smart, temperature dependent reversible AuNPs oligomers have great potential applications of plasmonic coupling based sensors and optical imaging.

Absorption and emission spectroscopic characteristics of dipterex and its molecularly imprinted recognition: A TD-DFT investigation

By using G09 program package, the absorption and fluorescence/phosphorescence spectra of dipterex were explored, and its spectroscopic characters were altered by methacrylic acid (MAA) as the imprinted molecule. The TD-DFT results revealed that: (1) All absorption and emission excitations of dipterex are assigned to the nσ∗ transition; (2) without MAA as imprinted molecule, one of the dipterex CCl bonds is extended significantly and dipterex is almost destroyed in transition states; (3) dipterex is connected to methacrylic acid via two hydrogen bonds; (4) for the dipterex–MAA complex, the electronic excitation (ππ∗ excitation) in absorption spectra is dominated by the configuration HOMO→LUMO.

Spectroscopic and electrical characters of SBD plasma excited by bipolar nanosecond pulse in atmospheric air

In this paper, an atmospheric surface barrier discharge (SBD) generated by annular electrodes in quartz tube is presented through employing bipolar nanosecond pulse voltage in air. The discharge images, waveforms of pulse voltage and discharge current, and optical emission spectra emitted from the discharges are recorded and calculated. A spectra simulation method is developed to separate the overlap of the secondary diffraction spectra which are produced by grating in monochromator, and N2 (B3Πg→A3Σu+) and O (3p5P→3s5S2o) are extracted. The effects of pulse voltage and discharge power on the emission intensities of OH (A2Σ+→X2Пi), N2+ (B2Σu+→X2Σg+), N2 (C3Πu→B3Πg), N2 (B3Πg→A3Σu+), and O (3p5P→3s5S2o) are investigated. It is found that increasing the pulse peak voltage can lead to an easier formation of N2+ (B2Σu+) than that of N2 (C3Πu). Additionally, vibrational and rotational temperatures of the plasma are determined by comparing the experimental and simulated spectra of N2+ (B2Σu+→X2Σg+), and the results show that the vibrational and rotational temperatures are 3250±20K and 350±5K under the pulse peak voltage of 28kV, respectively.

Mistic-fused expression of algal rhodopsins in Escherichia coli and its photochemical properties

BackgroundSince algal rhodopsins, the eukaryotic seven-transmembrane proteins, are generally difficult to express in Escherichia coli, eukaryotic cells have been used for heterologous expression. Mistic, a membrane-associated protein that was originally discovered in Bacillus subtilis, has been shown to improve the expression levels of many foreign integral membrane proteins in E. coli when used as a fusion partner linked to the N-terminus of cargo proteins. MethodsHere, we expressed two algal rhodopsins with N- and C-terminal Mistic domains in E. coli–Acetabularia rhodopsin I (ARI) and Chlamydomonas sensory rhodopsin B (CSRB, channel rhodopsin 2). UV/VIS spectroscopy, pH titration of proton acceptor residue, laser-induced photolysis and electrophysiological measurement were used for investigating important residues in proton transport and spectroscopic characters of the proteins. ResultsProtein yield of two algal rhodopsins was enhanced, obtaining 0.12mg of Mistic-ARI and 0.04mg of Mistic-CSRB per liter of culture. Spheroplast expression Mistic-ARI had outward proton-pumping activity, indicating protein functionality. Asp89 of ARI changed its protonation state by light absorption, and Asp100 was important for O600 formation. Electrophysiology revealed that both residues took part in proton transport. The spectroscopic analyses of Mistic-CSRB revealed its characteristics. ConclusionsFusion to the membrane-integrating protein Mistic can enhance overexpression of eukaryotic type I rhodopsins in E. coli. General SignificanceThese findings indicate that Mistic fusion and E. coli expression method could be an effective, low cost technique for studying eukaryotic membrane proteins. This may have useful implications, for example, in studying structural characteristics and optogenetics for rhodopsins.

Preparation and Characterization of Tourmaline/ZnO Composite Thin Films by a Facile Wet-Chemical Route

A series of tourmaline/ZnO composite thin films were prepared by the facile route of low-temperature wet chemical method. X-ray diffraction (XRD) and Raman Spectroscopy analyses showed the hybrid spectroscopic characters of tourmaline and ZnO. With adding the different amount of tourmaline powder, ZnO tended to exhibit the different peak intensity of X-ray diffraction and Raman vibration. ZnO deposited into bending nanosheets and intersected to upstanding nanostucture on the surface of tourmaline particles in SEM images. The optical adsorption properities obtained by the UV-Vis spectra indicated that the addition of tourmaline had enhanced the maximum absorption strength, and had shifted the absorption wavelength and the absorption range of ZnO crystals.

Theoretical study of hydrated Ca2+-amino acids (glycine, threonine and phenylalanine) clusters

The hydrated clusters of complexes formed by calcium ion and three different zwitterionic amino acids, glycine (Gly), threonine (Thr) and phenylalanine (Phe) have been studied in the gas phase at MP2/6-311++G(d,p), considering the coordination numbers 6–8 for Ca2+. The clusters with the first hydration shell around calcium ion exhibiting the 8-coordination configuration were found to be most preferred for all the three hydrated systems. The relative stabilities of Gly-, Thr- and Phe-Ca2+ decrease in the order Thr-Ca2+(H2O)n>Phe-Ca2+(H2O)n>Gly-Ca2+(H2O)n upon hydration in contrast to the order without water Phe-Ca2+>Thr-Ca2+>Gly-Ca2+. It may demonstrate that the nature of side chain has remarkable influence on the stability of hydrated calcium–amino acid clusters. The NBO charges were analyzed to understand the bonding characteristics between the calcium ion and the amino acids. Spectroscopic characters of the most stable hydrated clusters can be assigned based on researching the calculated spectra.

Radical-Involved Photosynthesis of AuCN Oligomers from Au Nanoparticles and Acetonitrile

We show here the first radical route for the direct photosynthesis of AuCN oligomers with different sizes and shapes, as evidenced by TEM observations, from an Au nanoparticle/benzaldehyde/CH(3)CN ternary system in air under UV-light irradiation. This photochemical route is green, mild, and universal, which makes itself distinguishable from the common cyanidation process. Several elementary reaction steps, including the strong C-C bond dissociation of CH(3)CN and subsequent •CN radical addition to Au, have been suggested to be critical in the formation of AuCN oligomers based on the identification of •CN radical by in situ EPR and the radical trapping technique, and other reaction products by GC-MS and (1)H NMR, and DFT calculations. The resulting solid-state AuCN oligomers exhibit unique spectroscopic characters that may be a result of the shorter Au-Au distances (namely, aurophilicity) and/or special polymer-like structures as compared with gold cyanide derivatives in the aqueous phase. The nanosized AuCN oligomers supported on mesoporous silica showed relatively good catalytic activity on the homogeneous annulation of salicylaldehyde with phenylacetylene to afford isoflavanones employing PBu(3) as the cocatalyst under moderate conditions, which also serves as evidence for the successful production of AuCN oligomers.

Analysis of Cross-Section Structure of a Polymer Wrapping Film Using Infrared Attenuated Total Reflection Imaging Technique with an Aid of Chemometrics

Infrared microscopic imaging techniques with an aid of augmented alternative least-squares (ALS) regression analysis have been employed for analyzing the interface structure involved in two wrapping films that have a common layered structure with different adhesive intermixing between the adjacent layers. A conventional single-band mapping technique exhibited a problem that the imaging results responded to the selection of an analytical band. On the other hand, the augmented ALS technique has proved to powerfully decompose the collection of spectra into spectroscopically independent spectra and quantity variations in the mapping area. Regardless, the chemometric analysis could not commonly be applied to the two films, and different pretreatments were necessary for analysis of the two films. As a result, the concentration profiles across the boundaries have readily revealed that the two films have largely different adhesive structures. In addition, the structural difference was found to be a reason an identical analytical technique cannot be employed for analysis of the two films. This study shows an appropriate pretreatment and selection of a chemometric technique considering the samples that have different spectroscopic characters are of great importance for effectively draw map images and pure-component spectra of the constituents.

Ultrafast Photophysics of Star-Like Molecules with Benzene and Triazine Core

Static and transient spectroscopic characters of newly synthesized start-like molecules, 1,3,5-tri(10-butyl-3-propenyl-10H-phenothiazine)-benzene (TP3B) and 2,4,6-tri(10-butyl-3-propenyl-10H-phenothiazine)-[1,3,5]triazine (TP3T), are studied using static, picosecond fluorescence and femtosecond transient absorption spectroscopy. The results show that when the benzene group is in the center, a large conjugation system is formed, while a fast electron-transfer process happens when the center group is triazine.

Absorption and fluorescence emission spectroscopic characters of naphtho‐homologated yy‐DNA bases and effect of methanol solution and base pairing

A comprehensive theoretical study of electronic transitions of naphtho-homologated base analogs, namely, yy-T, yy-C, yy-A, and yy-G, was performed. The nature of the low-lying excited states is discussed, and the results are compared with those from experiment and also with those of y-bases. Geometrical characteristics of the lowest excited singlet pipi* and npi* states were explored using the CIS method, and the effects of methanol solution and paring with their complementary natural bases on the relevant absorption and emission spectra of these modified bases were examined. The calculated excitation and emission energies agree well with the measured data, where experimental results are available. In methanol solution, the fluorescence from yy-A and yy-G would be expected to occur around 539 and 562 nm, respectively, suggesting that yy-A is a green-colored fluorophore, whereas yy-G is a yellow-colored fluorophore. The methanol solution was found to red-shift both the absorption and emission maxima of yy-A, yy-T, and yy-C, but blue-shift those for yy-G. Generally, though base pairing has no significant effects on the absorption and fluorescence maxima of yy-A, yy-C, and yy-T, it blue-shifts those for yy-G.

Absorption and Fluorescence Emission Spectroscopic Characters of Size-Expanded yDNA Bases and Effect of Deoxyribose and Base Pairing

We present an ab initio study of the optical absorption and emission spectra of size-expanded nucleic acid base analogues (yA, yT, yT-m, yG, yG-t2, and yC) obtained by benzo homologation (see Krueger, A. T.; Lu, H.; Lee, A. H. F.; Kool, E. T. Acc. Chem. Res. 2007, 40, 141 and references therein). Also examined were the effects of linking to deoxyribose and hydrogen bonding to their natural complementary bases (T, A, C, and G, respectively). The calculated excitation and emission energies are in good agreement with the measured data where experimental results are available. The geometries corresponding to the first excited singlet state of yA and yT are found to be quasi-planar, while those for yG and yC are nonplanar. In general, binding to deoxyribose will red shift the absorbance and fluorescence emission maxima of the y-bases. The ground-state geometries of the Watson-Crick analog base pairs (yAT, yTA, yGC, and yCG) are found to be planar, and the calculated interaction energies are very close to those of natural base pairs, indicating that the y-bases can pair with their natural complementary partners to generate stable base pairs. The base pairing has no significant effects on the fluorescence emission of yA, yC, and yT, but blue shifts the fluorescence emission of yG by 22 nm.

Structural and functional characterization of novel G-quadruplexed DNA-heme coordination complex

We analyzed the coordination structure of G-quadruplexed DNA-heme complex which exhibits remarkably similar spectroscopic characters to hemoprotein such as myoglobin. We found that some exogenous ligands can be accommodated at the 6th coordination site of heme in the G-quadruplexed DNA-heme complex with a DNA base coordinated to the 5th site. The G-quadruplexed DNA-hemin complex is expected to play a role as a novel DNAzyme. These findings provide novel insights into molecular design for creating artificial heme enzymes using spontaneous assembly between G-quadruplexed DNA and heme.

Structure and Function Relationships of a Redox-Sensor Protein, Heme-Regulated Phosphodiesterase

Heme-regulated phosphodiesterase from Escherichia coli (Ec DOS) is a novel PAS heme-sensor enzyme. Ec DOS is active in the Fe2+ heme-bound form, whereas it is inactive in the Fe3+ heme-bound form. To elucidate the mechanism of the redox-dependent heme-regulated catalysis, we examined spectroscopic and functional characters of site-directed and deletion mutant proteins. We also determined crystal structures of the wild type enzyme under various conditions. In this review, we summarized findings about heme-sensor proteins, PAS domain and phosphodiesterase in general and structure and function relationships of Ec DOS specifically.