EA Spectra Research Articles

Spectroscopic Identification of the Charge Transfer State in Thiophene/Fullerene Heterojunctions: Electroabsorption Spectroscopy from GW/BSE Calculations.

Creation of charge transfer (CT) states in bulk heterojunction systems such as C60/polymer blends is an important intermediate step in the creation of carriers in organic photovoltaic systems. CT states generally have small oscillator strengths in linear optical absorption spectroscopy owing to limited spatial overlap of electron and hole wave functions in the CT excited state. Electroabsorption spectroscopy (EA) exploits changes in wave function character of CT states in response to static electric fields to enhance detection of CT states via nonlinear optical absorption spectroscopies. A 4 × 4 model Hamiltonian is used to derive splittings of even and odd Frenkel (FR) excited states and changes in wave function character of CT excited states in an external electric field. These are used to explain why FR and CT states yield EA lineshapes which are first and second derivatives of the linear optical absorption spectrum. The model is applied to ammonia-borane molecules and pairs of molecules with large and small B-N separations and CT or FR excited states. EA spectra are obtained from differences in linear optical absorption spectra in the presence or absence of a static electric field and from perturbative sum over states (SOS) configuration interaction singles χ(2) and χ(3) nonlinear susceptibility calculations. Good agreement is found between finite field (FF) and SOS methods at field strengths similar to those used in EA experiments. EA spectra of three C60/oligothiophene complexes are calculated using the SOS method combined with GW/BSE methods. For these C60/oligothiophene complexes, we find several CT states in a narrow energy range in which charge transfer from the thiophene HOMO level to several closely spaced C60 acceptor levels yields an EA signal around 10% of the signal from oligothiophene.

Theoretical design, prediction and synthesis of a magenta dye SCFX-AYRL for sustainable coloration of natural fibers in SCF-CO2

A special magenta dye SCFX-AYRL with dichlorotriazine as reactive group, designed as one of supercritical trichromatic dyes, was successfully synthesized for sustainable coloration of natural fibers in supercritical fluid of carbon dioxide (SCF-CO2). The products were characterized and tested by FT-IR, 1H NMR, LC-MS, EA and Uv-Vis spectra. Moreover, Gaussian software was also employed to assist a theoretical design of the dye and its precursor, such as the optimization of structure conformations, the calculation of frontier molecular orbitals and parameters, and the prediction of characteristic absorption wavelength. The obtained results show that the molecular structure and color characteristics of the synthesized dye well met the expected theoretical design and calculations. Particularly, the powerfully excited molecular orbitals facilitated the first electron transition from the highest occupied orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) by contributing characteristic singlet absorption bands for the precursor and its target dye. Moreover, an energy gap (ΔE) calculation between the LUMO and the HOMO was performed to predict color hue shift, and was well consistent with experimental detects. A successful application of the special dye on natural protein fibers was observed for eco-friendly coloration in SCF-CO2 with high color strength, fixation efficiency over 90.0 %, as well as high brilliant color and fastness.

Electronic States of Tris(bipyridine) Ruthenium(II) Complexes in Neat Solid Films Investigated by Electroabsorption Spectroscopy.

We present the electric field-induced absorption (electroabsorption, EA) spectra of the solid neat films of tris(bipyridine) Ru(II) complexes, which were recently functionalized in our group as photosensitizers in dye-sensitized solar cells, and we compare them with the results obtained for an archetypal [Ru(bpy)3]2+ ion (RBY). We argue that it is difficult to establish a unique set of molecular parameter values by discrete parametrization of the EA spectra under the Liptay formalism for non-degenerate excited states. Therefore, the experimental EA spectra are compared with the spectra computed by the TDDFT (time-dependent density-functional theory) method, which for the first time explains the mechanism of electroabsorption in tris(bipyridine) Ru complexes without any additional assumptions about the spectral lineshape of the EA signal. We have shown that the main EA feature, in a form close to the absorption second derivative observed in the spectral range of the first MLCT (metal-to-ligand charge transfer) absorption band in Ru(bpy)3(PF6)2, can be attributed to a delocalized and orbitally degenerate excited state. This result may have key implications for the EA mechanism in RBY-based systems that exhibit similar EA spectra due to the robust nature of MLCT electronic states in such systems.

Enhanced organics degradation by three-dimensional (3D) electrochemical activation of persulfate using sulfur-doped carbon particle electrode: The role of thiophene sulfur functional group and specific capacitance

For further enhancing the electrochemical oxidation performance, sulfur-doped carbon particle electrode was employed in the three-dimensional (3D) electro-assisted activation of persulfate process (ACS/PS/EC). Herein, an in situ S-doped activated carbon (ACS) was prepared and applied as the particle electrode as well as catalyst in ACS/PS/EC system. Several carbon particle electrodes with different annealing temperature were prepared and characterized via EA, BET, XPS and Raman spectra. Cyclic voltammetry (CV) was perform to obtain the specific capacitance and investigate the interfacial electron transfer of ACS particle. The results of comparative experiments showed significant synergy between electric and catalytic activations of PS. Especially, the as-prepared sample treated at 850 °C (ACS-850) exhibited an outstanding catalytic performance, and the phenol degradation rate was greatly improved by nearly 100% with the application of electric field. By comparing of several carbon particle electrodes with different functional groups and specific capacitances, it is revealed that thiophene sulfur functional group is the mainly active site for both electric and catalytic activation of PS, and the specific capacitance acts as assistant factor. Quenching experiments proved that the 3D electro-assisted activation of PS proceeded through both radical and non-radical pathway. Possible mechanism for ACS/PS/EC electrochemical process was proposed.

Soft-Mode Parameter as an Indicator for the Activation Energy Spectra in Metallic Glass.

The activation energy (EA) spectra of the potential energy landscape (PEL) provide a convenient perspective for interpreting complex phenomena in amorphous materials; however, the link between the EA spectra and other physical properties in metallic glasses is still mysterious. By systematically probing the EA spectra for numerous metallic glass samples with distinct local geometric ordering, which correspond to broad processing histories, we found that the shear moduli of the samples are strongly correlated with the arithmetic mean of the EA spectra rather than with the local geometrical ordering. Furthermore, we studied the correlation of the obtained EA spectra and various well-established physical parameters. The outcome of our research clearly demonstrates that the soft-mode parameter Ψ and the EA spectrum are correlated; therefore, this could be a good indicator of metallic glass properties and sheds important light on the structure-property relationship in metallic glass through the medium of the PEL.

Study on the oxidation transformation of diethylamine in a confined region of ZSM-22

ZSM-22 zeolite has been synthesized using diethylamine (DEA) as structure directing agent. The crystal obtained was characterized by XRD, IR, TG/DTA, elemental analysis, ICP and 13C MAS NMR spectroscopy. It is found that DEA is incorporated intact in its protonated form in TON. Furthermore, the oxidation of DEA restricted in the TON by H2O2 and HIO4 has been studied. Based on the IR, TG/DTA, EA and 13C NMR spectra data, it has been found that the oxidation products were saturated hydrocarbons and some other amines by H2O2, whereas saturated hydrocarbons, other amines and ethyleneimine produced by HIO4. These oxidation products are different from the bulk reaction. This work opens new opportunities for further research of molecular reactions on the inorganic hybrids.

Transformations of lead 1,3-propylenediaminetetraacetate to its MOF products for the selective adsorption of methanol

Water soluble coordination polymer of potassium lead 1,3-propylenediaminetetraacetate {K4[Pb2(1,3-pdta)2]·6H2O}n (1) and its insoluble products {[Pb(1,3-H2pdta)(H2O)]·2H2O}n (2), {[Pb2(1,3-pdta)(H2O)4]·4H2O}n (3) and [Pb2(1,3-pdta)(H2O)2]n (4) were obtained from the direct reactions of lead nitrate with 1,3-propylenediaminetetraacetic acid in different conditions (1,3-H4pdta=1,3-propylenediaminetetraacetic acid). The former 1 could be converted to the insoluble products of {[Pb2(1,3-pdta)(H2O)4]·4H2O}n (3) and [Pb2(1,3-pdta)(H2O)2]n (4) in weak acidic solution. The complexes have been full characterized by EA, FT-IR, solution and solid state 13C NMR spectra, thermogravimetric and structural analyses. Interestingly, 3 contains a unique (H2O)26 cluster and a 5.2Å pore after eliminating the guest water molecules, which exhibits reversible adsorption for methanol. This is confirmed by PXRD and solid state 13C NMR analyses. Nano-confined methanol in microporous structure has been observed based on the large downfield shift of 13C NMR signal (Δδ 9.72ppm), attributing to the methyl group in methanol.

Demographic characteristics in patients with short-gap and long-gap esophageal atresia

Patients and methods Medical records of all patients managed for EA spectrum in our department between 2003 and 2012 were evaluated, retrospectively. Demographic data included the maternal age, the number of parities and deliveries, the presence of polyhydramnios and the prenatal diagnosis, sex, the gestational age and prematurity, the type of delivery and the birth weight, age at the time of diagnosis and treatment, the presence of associated anomalies including VACTERL-type and nonVACTERL-type anomalies, the type of EA according to Gross classification, and discrepancies between the diameters of atretic esophageal ends. SGEA and LGEA were defined as a gap of less than three vertebral bodies or three or more vertebral bodies in length between the atretic esophageal ends, respectively.

Synthesis and Characterization of New Mixed Rare Earth Triple-Decker Complexes With Tetra(tert-butyl)phthalocyaninato and Meso-Tetrakis(4-pyridyl)porphyrinato Ligands

Four new mixed 3(4), 12(13), 21(22), 30(31)-tetra(tert-butyl)phthalocyaninato tetrakis(4-pyridyl)porphyrinato rare earth triple-decker complexes M2(TPyP)(TBPc)2 (M˭Ce, Sm, Tb, and Tm) have been prepared by treating M(acac)(TPyP) with corresponding homoleptic substituted bis(phthalocyaninato) rare earth complexes M(TBPc)2 in refluxing 1,2,4-trichlorobenzene (TCB), typical for the light, middle, and heavy rare earths, respectively. Typical IR marker bands of the substituted phthalocyanine dianion Pc(TBPc)2− show strong bands at ca. 1323 cm−1, and are attributed to pyrrole C˭C stretchings. The TPyP2− IR marker band at ca. 1270–1300 cm−1 was not observed for these compounds. A very strong band at 1500 cm−1 with contributions from both pyrrole C˭C and aza C˭N stretchings and also isoindole stretching was the marker Raman band of (TBPc)2−. Their electrochemical properties were investigated by cyclic voltammetry and differential pulse voltammetry. The four complexes were also characterized by EA, MS, and UV-vis spectra.

Electroabsorption studies of organic p-i-n solar cells: evaluating the built-in voltage

ABSTRACTWe investigate the built-in voltage in organic bulk heterojunction solar cells using electroabsorption spectroscopy based on the Stark effect, i.e. the variation of the absorption energies of a material caused by an electric field. Due to spectral contributions of permanent dipoles, a novel approach for evaluating the EA spectra is required. We use a fitting routine analyzing a broad spectral range instead of using only a single wavelength. A reliable quantitative determination of the built-in voltage is achieved.

On the mass composition of primary cosmic rays in the energy region 1015–1016 eV

A method to determine the primary cosmic ray mass composition is presented. Data processing is based on the theoretical model representing the integral muon multiplicity spectrum as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. In the first stage, the permissible intervals of primary nuclei fractions fi are determined on the basis of the EAS spectrum versus the total number of muons (Eμ ⩾ 235 GeV). In the second stage, the permissible intervals of fi are narrowed by the fitting procedure. We use the experimental data on high multiplicity muon events (nμ ⩾ 114) collected at the Baksan underground scintillation telescope. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 1015–1016 eV has been defined: fp = 0.235 ± 0.02, fHe = 0.290 ± 0.02, fH = 0.475 ± 0.03. The average logarithmic mass is lnA ≃ 1.93 and it is in good agreement with results before the knee energy obtained by JACEE, RUNJOB, ATIC. At energies above the knee (1015–1016 eV) our analysis supports KASCADE results and contradicts to CASA-BLANCA and DICE data.

On the mass composition of primary cosmic rays in the energy region 1015 – 1016 eV

The method of the determination of Primary Cosmic Ray mass composition is presented. Data processing is based on the theoretical model representing the EAS spectrum vs the total number of muons as the superposition of the spectra corresponding to different kinds of primary nuclei. The method consists of two stages. At the first stage, the permissible intervals of primary nuclei fractions fi are determined on the base of the EAS spectrum vs the total number of muons (Eμ ≥ 235 GeV). At the second stage, the permissible intervals of fi are narrowed by fitting procedure. Within the framework of three components (protons, helium and heavy nuclei), the mass composition in the region 1015 – 1016 eV has been defined: fp = 0.235 ± 0.02, fHe = 0.290 ± 0.02, fH = 0.475 ± 0.03.

Sulfonated copolymers with SO3H and COOH groups for the hydrolysis of polysaccharides

The well-defined sulfonated block copolymer poly(acrylic acid)-block-poly(styrene sulfonic acid) (PAA-b-PSSH) and the random copolymer poly(acrylic acid)-random-poly(styrene sulfonic acid) (PAA-r-PSSH) were prepared by direct thermolysis of the precursor copolymers poly(tert-butyl acrylate)-block-poly(neopentyl styrenesulfonate) (PtBA-b-PNSS) and poly(tert-butyl acrylate)-random-poly(neopentyl styrenesulfonate) (PtBA-r-PNSS), which were synthesized by living radical polymerization (MWD < 1.10) catalyzed with CuBr. GPC, EA, 1H NMR and FT-IR spectra were employed to characterize the structure of the synthesized acid polymers. The catalytic performance of the acid polymers was evaluated for the hydrolysis of starch and cellulose in aqueous solution under microwave irradiation. With the same effective acid concentration, the random copolymer PAA-r-PSSH gave the highest glucose yield among the prepared catalysts. It is believed that the good results were caused by the synergic effect of the SO3H and COOH groups in the polymer chain. In addition, microwave irradiation led to better glucose yields in the hydrolysis of polysaccharides than the conventional heating method with acid polymers as catalysts.

Synthesis and crystal structure of 2-D silver coordination polymers containing aminopyrazine

Two supramolecules of Ag(I), [Ag(NO3)(APZ)] n (1) and {[Ag(APZ)2][CF3COO] · H2O} n (2) (APZ = aminopyrazine) have been prepared by self-assembly of Ag(I) salts with APZ in MeOH/H2O. EA, IR, and TGA spectra have been recorded and the complexes have been structurally characterized by X-ray crystallography, confirming that 1 and 2 are 2-D pleated rectangular grid coordination polymers. The in 1 is coordinated to Ag+, bidentate, and μ2,η1-, while CF3COO− in 2 is not coordinated. Ag ··· O interactions, hydrogen bonds, and π ··· π stacking interactions support the supramolecular structures.

Electroabsorption in vacuum-evaporated films of bathocuproine

Electric field modulated absorption (EA) spectra were measured in vacuum evaporated films of bathocuproine (BCP), the phenanthroline derivative commonly used in organic light emitting diodes. The EA spectra are interpreted in terms of the standard Stark spectroscopy analysis using a comparison of the EA spectrum with first and second absorption derivatives. The dipole moment and polarizability changes upon photoexcitation were calculated for the lowest energy singlet excited states in BCP films. The excited states are recognized as Frenkel excitons carrying intramolecular charge transfer (CT) character. Full text: PDF

Synthesis, DNA Binding, and DNA Photocleavage of the Cobalt(III) Complexes [Co(bpy)2MDPPZ]3+, [Co(dmb)2MDPPZ]3+, and [Co(phen)2MDPPZ]3+and their Antimicrobial Activity

The ligand 7-methyl dipyrido[3,2-a:2′-3′-c]phenazine (MDPPZ) and its complexes [Co(bpy)2MDPPZ]3+(1) (bpy = 2,2′-bipyridine), [Co(dmb)2MDPPZ]3+ (2), (dmb = 4,4′-dimethyl-2,2′-bipyridine), and [Co(phen)2MDPPZ]3+(3) (phen = 1,10-phenanthroline) have been synthesized and characterized by UV-VIS, IR, EA, 1H, and 13C-NMR and mass spectra. The interactions of the three complexes with CT-DNA have been investigated by absorption and emission spectroscopy, DNA melting, viscosity measurements, and DNA cleavage assay. The experimental results suggested that these complexes bind to CT-DNA through an intercalative mode. Three complexes have also been found to promote the photo cleavage of plasmid pBR-322 DNA under irradiation. The inhibition studies suggest that the oxygen species are mainly responsible for the photocleavage by these complexes. Further, all the three Co(III) complexes synthesized were screened for their antimicrobial activity.

Stark Effect of Intrinsic and Extrinsic Charge-Transfer Excitons in a Linear Donor−Acceptor Stack: Anthracene−Pyromellitic Dianhydride

Anthracene-PMDA single crystals display at 2K about 70 meV below a well-known intrinsic charge-transfer exciton three narrow absorption lines, which are attributed to CT excitons bound to defects of a few 10(-5) concentration. All excitons respond very sensitively to electric fields along the molecular stack because of the large dipole moment, about 2 eA, of an ionized donor-acceptor pair, but only intrinsic excitons observe an optical selection rule. Although the triclinic unit cell contains only one pair of molecules, excitons appear in field-modulated spectra as near-degenerate doublets of different parity with very small splitting. The line shape of the EA spectra and selection rules with respect to the polarization of light and orientation of the field are consistent with the inversion symmetry of the lattice and the molecules. The simple crystal structure enables identification of the defects that are responsible for extrinsic excitons. Symmetry consideration based on translation invariance lead to a new interpretation of intrinsic excitons as true crystal states with charge transfer from the donor to the acceptor sublattice.

Classification of protein fold classes by knot theory and prediction of folds by neural networks: A combined theoretical and experimental approach

We present different means of classifying protein structure. One is made rigorous by mathematical knot invariants that coincide reasonably well with ordinary graphical fold classification and another classification is by packing analysis. Furthermore when constructing our mathematical fold classifications, we utilize standard neural network methods for predicting protein fold classes from amino acid sequences. We also make an analysis of the redundancy of the structural classifications in relation to function and ligand binding. Finally we advocate the use of combining the measurement of the VA, VCD, Raman, ROA, EA and ECD spectra with the primary sequence as a way to improve both the accuracy and reliability of fold class prediction schemes.

On EAS spectrum with extremely low content of hadrons in the primary-energy range ∼1014−1015 eV

The distribution of energy fluxes of the hadron component of extensive air showers through an ion-ization calorimeter in the primary-energy range ∼3 × 1013−1016 eV is considered. Extensive air showers with zero and minimum energy fluxes of the hadron component are selected. It is concluded that the primary-energy range E 0 ≈ 1 × 1014−2 × 1015 eV contains isotropic γ radiation with a spectrum close to bell-shaped, having a maximum near E 0 ≈ 2.2 × 1014 eV and an additional peak near E 0 ≈ 1.6 × 1015 eV.

Synthesis, Crystal Structure, and Biological Activities of 2-Oxo-2-aryl-1-(1,2,4-triazol-1-yl) ethyl phenylcarbamodithioate

The two title compounds, 2-oxo-2- p-tolyl-1-(1,2,4-triazol-1-yl) ethyl phenylcarbamodithioate(compound 3a) and 2-oxo-2- p-biphenyl-1-(1,2,4-triazol-1-yl) ethyl phenylcarbamodithioate(compound 3b), were synthesized and identified by IR, EA and 1H NMR spectra. The crystal structure of compound 3b was determined by X-ray diffraction analysis. The compound crystallized in a monoclinic system of space group P2 1/ c with M r = 398.47(C 23H 18N 4OS), a = 0.8769(2) nm, b = 1.1924(2) nm, c = 2.0440(6) nm, β = 109.66(3) °, V = 2.0126(8) nm 3, Z = 4, D c = 1.315 g/cm 3, F(000) = 832, μ = 0.183 mm -1, final R 1 = 0.0819. The biological test result shows that the two title compounds exhibit certain fungicidal activities.