Functionalized styryl bipyridine as a superior chelate for a ruthenium sensitizer in dye sensitized solar cells

The new sensitizer MC119 has been synthesized and the solar cell constructed with 0.25 cm(2) active area photoelectrode in combination with an electrolyte composed of 0.6 M dimethylpropyl-imidazolium iodide (DMPII), 0.05 M I(2), 0.5 M TBP and 0.1 M LiI in acetonitrile achieved a solar to electric energy conversion efficiency (η) of 8.36% under Air Mass (AM) 1.5 sunlight, while the reference N719 sensitized solar cell exhibited η-value of 7.2%.     

Syntheses, optical and intramolecular magnetic properties of mono- and di-radicals based on nitronyl-nitroxide and oxoverdazyl groups appended to 2,6-bispyrazolylpyridine cores

This paper presents the synthesis of a series of nitronyl-nitroxide (NN), oxoverdazyl (OVZ) based mono-, and bi-radicals attached to 4-phenyl-2,6-bispyrazolylpyridine coupling unit, their optical, electron spin resonance (ESR) spectroscopic studies and computational analysis. The ESR studies revealed that the axial zero-field splitting (zfs) parameter of the NN biradical (|D/hc| = 0.00719 cm(-1)) is larger than the OVZ biradical (|D/hc| = 0.00601 cm(-1)). Additionally both biradicals displayed forbidden half-field transitions (ΔM(s) = ±2; g(av) ~ 4.01) at 170 K demonstrating their triplet nature. The cryogenic ESR measurements of the two biradicals showed a Curie magnetic behaviour of the ΔM(s) = ±2 signal intensities (χ(EPR)) down to 4.2 K. A detailed comparative analysis of the strength of hyperfine coupling, spin density distribution, zfs and the spin-spin exchange coupling (J) of both NN and OVZ based biradicals showed that the ground state spin multiplicity of both biradicals is probably triplet (S = 1) or it is nearly degenerate singlet-triplet states with J(NN)?J(OVZ).     

Photoinduced energy and electron transfer in phenylethynyl-bridged zinc porphyrin-oligothienylenevinylene-C60 ensembles

Donor-bridge-acceptor triad (Por-2TV-C(60)) and tetrad molecules ((Por)(2)-2TV-C(60)), which incorporated C(60) and one or two porphyrin molecules that were covalently linked through a phenylethynyl-oligothienylenevinylene bridge, were synthesized. Their photodynamics were investigated by fluorescence measurements, and by femto- and nanosecond laser flash photolysis. First, photoinduced energy transfer from the porphyrin to the C(60) moiety occurred rather than electron transfer, followed by electron transfer from the oligothienylenevinylene to the singlet excited state of the C(60) moiety to produce the radical cation of oligothienylenevinylene and the radical anion of C(60). Then, back-electron transfer occurred to afford the triplet excited state of the oligothienylenevinylene moiety rather than the ground state. Thus, the porphyrin units in (Por)-2TV-C(60) and (Por)(2)-2TV-C(60) acted as efficient photosensitizers for the charge separation between oligothienylenevinylene and C(60).     

A quinoline based bis-urea receptor for anions: a selective receptor for hydrogen sulfate

A dipodal bis-urea receptor has been synthesized from the reaction of 8-amino quinoline and 1,4-phenylene diisocyanate in dichloromethane, and the anion binding ability of the receptor has been studied using fluoride, chloride, bromide, iodide, perchlorate, nitrate, dihydrogen phosphate and hydrogen sulfate by UV-Vis titrations in DMSO. The results show that the receptor binds each of the anions with a 1:1 stoichiometry, showing high affinity and moderate selectivity for hydrogen sulfate among the anions studied. Ab initio calculations based on density functional theory (DFT) suggest that an anion (X(-)) is bonded within the cleft formed by the two arms of the receptor through two NH...X(-) and two aromatic CH...X(-) interactions. The results from solution and theoretical studies suggest that binding is predominantly influenced by hydrogen bonding interactions and the basicity of anions.     

Photocurrent growth and decay behavior of crystal violet dye-based photoelectrochemical cell in photovoltaic mode

Crystal violet dye-doped photoelectrochemical cells (PEC) show different and unusual behavior in their electrical and optical characteristics. In this work, we have studied the photocurrent growth and decay behavior of crystal violet dye-based solid-state PEC in photovoltaic mode. Photocurrent growth and decay are studied for different intensities of illumination. They follow a power law relationship with time which is of the form I _ph?～?t ^±α , where I _ph is the photocurrent and α is a constant. The positive and negative signs are used to indicate the growth and decay of the photocurrent, respectively. This power law relation is explained by dispersive transport model which was originally developed by Scher and Montrol and subsequently modified by different workers. The constant, α is termed as dispersion parameter, and it is related to the disorder. It is observed that the value of this parameter depends on the intensity of incident illumination. Dependence of this dispersion parameter on incident intensity is studied in this work. Variations of α with intensity for growth and decay have been discussed. In our system, the value of α is 0.325?±?0.005 for decay whereas, in the growth region, its value varies from 0.55 to 0.33, when intensity varies from minimum to maximum. The value of the disorder parameter, α, decreases as the intensity of illumination increases for growth of current whereas it remains nearly constant for decay of current. This work will be helpful in understanding the charge transport mechanism of dye-based PEC cell.     

The ionic conductivity in lithium-boron oxide materials and its relation to structural, electronic and defect properties: insights from theory

We review recent theoretical studies on ion diffusion in (Li(2)O)(x)(B(2)O(3))(1-x) compounds and at the interfaces of Li(2)O :B(2)O(3) nanocomposite. The investigations were performed theoretically using DFT and HF/DFT hybrid methods with VASP and CRYSTAL codes. For the pure compound B(2)O(3), it was theoretically confirmed that the low-pressure phase B(2)O(3)-I has space group P3(1)21. For the first time, the structure, stability and electronic properties of various low-index surfaces of trigonal B(2)O(3)-I were investigated at the same theoretical level. The (101) surface is the most stable among the considered surfaces. Ionic conductivity was investigated systematically in Li(2)O, LiBO(2), and Li(2)B(4)O(7) solids and in Li(2)O:B(2)O(3) nanocomposites by calculating the activation energy (E(A)) for cation diffusion. The Li(+) ion migrates in an almost straight line in Li(2)O bulk whereas it moves in a zig-zag pathway along a direction parallel to the surface plane in Li(2)O surfaces. For LiBO(2), the migration along the c direction (E(A) = 0.55 eV) is slightly less preferable than that in the xy plane (E(A) = 0.43-0.54 eV). In Li(2)B(4)O(7), the Li(+) ion migrates through the large triangular faces of the two nearest oxygen five-vertex polyhedra facing each other where E(A) is in the range of 0.27-0.37 eV. A two-dimensional model system of the Li(2)O :B(2)O(3) interface region was created by the combination of supercells of the Li(2)O (111) surface and the B(2)O(3) (001) surface. It was found that the interface region of the Li(2)O:B(2)O(3) nanocomposite is more defective than Li(2)O bulk, which facilitates the conductivity in this region. In addition, the activation energy (E(A )) for local hopping processes is smaller in the Li(2)O :B(2)O(3) nanocomposite compared to the Li(2)O bulk. This confirms that the Li(2)O:B(2)O(3) nanocomposite shows enhanced conductivity along the phase boundary compared to that in the nanocrystalline Li(2)O.     

Facile synthesis and altered ionization efficiency of diverse Nε-alkyllysine-containing peptides

Protein lysine methylation is a biologically-important posttranslational modification. Given the increased use of alkyllysine-containing peptides to study protein methylation, we describe an efficient solid-phase synthesis to access various alkyllysine-containing peptides. As an exemplary application, we evaluated how ionization efficiency of the alkyllysine peptides affects mass spectrometric analysis.     

A practical acoustical absorption analysis of coir fiber based on rigid frame modeling

An analytical study based on rigid frame model is demonstrated to evaluate the acoustic absorption of coir fiber. Effects of different conditions such as combination of air gap and perforated plate (PP) are studied in this work. Materials used here are treated as rigid rather than elastic, since the flow resistivity of coir fiber is very low. The well-known rigid frame Johnson-Allard equivalent-fluid model is applied to obtain the acoustic impedance of single layer coir fiber. Atalla and Sgard model is employed to estimate the surface impedance of PP. Acoustic transmission approach (ATA) is utilized for adding various consecutive layers in multilayer structure. Models are examined in different conditions such as single layer coir fiber, coir fiber backed with air gap, single layer PP in combination with coir fiber and air gap. Experiments are conducted in impedance tube on normal incidence sound absorption to validate the results. Results from the measurement are found to be in well agreement with the theoretical absorption coefficients. The performance of the rigid frame modeling method is checked more specifically in all conditions, by the mean prediction error rate of normal incidence sound absorption coefficients. Comparison between the measured absorption coefficients and predicted by rigid frame method shows discrepancy lower than 20 and 15% for most of the conditions in the frequency range of 0.2?C1.5 and 1.5?C5 kHz, respectively. Moreover, acoustic absorption of various single and multilayer structures is compared with the simpler empirical methods such as Delany-Bazley and Miki model; and complicated method such as Biot-Allard Model and Allard Transfer Function (TF) method. Comparisons show that the presented method offers a better accuracy of the results than the empirical models. Subsequently, it can provide almost same absorption plot with Biot-Allard model (single layer combination) and TF method (multilayer combination) proving it to be a comprehensively easy and general analytical tool. Therefore, the rigid frame model can be implemented relatively easier than other similar models to analyze the acoustic absorption of coir fiber in most of the conditions.     

Exponential Stability in Non-linear Difference Equations

Non-negative definite Lyapunov functionals are employed to obtain sufficient conditions that guarantee exponential stability of the zero solution of a non-linear discrete system. The theory is illustrated with several examples.     

Conversion Characteristics of Some Major Cannabinoids from Hemp (Cannabis sativa L.) Raw Materials by New Rapid Simultaneous Analysis Method

This study was carried out to develop a high-performance liquid chromatography method for short-time analysis of the main cannabinoids in the inflorescence of hemp (Cannabis sativa L.). We also performed decarboxylation of the raw material using our advanced analysis technique. In this study, the UV spectrum was considered to analyze each of the four common cannabinoids, solvents, and samples, where the uniform elution of acidic cannabinoids without peak tailing and acids was tested. Optimal results were obtained when readings were taken at a wavelength of 220 nm using water and methanol containing trifluoroacetic acid as mobile phases in a solvent gradient system. The established conditions were further validated by system suitability, linearity, precision, detection limit, and quantitation limit tests. The decarboxylation index (DT₅₀) confirmed that Δ9-THCA decarboxylated faster than CBDA, and both maintained a linear relationship with time and temperature. In addition, the loss of cannabidiol was better prevented during the decarboxylation process in the natural state than in the extracted state.