Appearance Of New Absorption Band Research Articles

Влияние алюмосиликатных ценосфер на структуру и свойства эластомерных композиционных материалов на основе этилен-пропилен-диеновых эластомеров

The use of industrial waste to develop new value-added materials and reduce their environmental impact is one of the most important tasks of science and industry, which can largely solve the problem of waste pollution. This work is aimed at studying the effect of different concentrations of fly ash aluminosilicate cenospheres on the structure and properties of elastomeric composites. In this work, using laboratory rollers, composite materials based on ethylene-propylene-diene rubber (EPDM-40) with different mass fractions of fly ash (10, 20 and 30 %) were obtained. Using the method of optical microscopy, the microstructure of mixtures of EPDM and aluminosilicate cenospheres was studied and it was shown that the filler content of more than 30% increases the content of larger cenosphere agglomerates in the structure, which indicates interfacial separation in mixtures, probably due to the fact that mechanical mixing on mixing equipment does not allow to achieve a uniform distribution of the filler throughout the elastomeric matrix. The IR spectra show the appearance of new absorption bands in the region. 1400 – 800 cm–1, corresponding to Si – O – Si stretching vibrations present in aluminosilicate cenospheres. According to the thermogravimetry data of the studied compositions, the introduction of aluminosilicate cenospheres contributed to a slight increase in the thermal stability of the tested composition with a cenosphere content of more than 30%. The influence of the concentration of aluminosilicate cenospheres on the resistance of composites to aggressive media was analyzed and it was found that the introduction of a cenosphere filler in an amount of 10 to 30 % in a mixture based on EPDM can increase the oil and petrol resistance of materials.

Complexes of transition metal carbonyl clusters with tin(II) phthalocyanine in neutral and radical anion states: methods of synthesis, structures and properties.

Coordination of tin(II) phthalocyanine to transition metal carbonyl clusters in neutral {SnII(Pc2-)}0 or radical anion {SnII(Pc˙3-)}- states is reported. Direct interaction of Co4(CO)12 with {SnII(Pc2-)}0 yields a crystalline complex {Co4(CO)11·SnII(Pc2-)} (1). There is no charge transfer from the cluster to phthalocyanine in 1, which preserves the diamagnetic Pc2- macrocycle. The Ru3(CO)12 cluster forms complexes with one or two equivalents of {SnII(Pc˙3-)}- to yield crystalline {Cryptand[2.2.2](Na+)}{Ru3(CO)11·SnII(Pc˙3-)}- (2) or {Cryptand[2.2.2](M+)}2{Ru3(CO)10·[SnII(Pc˙3-)]2}2-·4C6H4Cl2 (3) (M+ is K or Cs). Paramagnetic {SnII(Pc˙3-)}- species in 2 are packed in π-stacking [{SnII(Pc˙3-)}-]2 dimers, providing strong antiferromagnetic coupling of spins with exchange interaction J/kB = -19 K. Reduction of Ru3(CO)12, Os3(CO)12 and Ir4(CO)12 clusters by decamethylchromocene (Cp*2Cr) and subsequent oxidation of the reduced species by {SnIVCl2(Pc2-)}0 yield a series of complexes with high-spin Cp*2Cr+ counter cations (S = 3/2): (Cp*2Cr+){Ru3(CO)11·SnII(Pc˙3-)}-·C6H4Cl2 (4), (Cp*2Cr+){Os3(CO)10Cl·SnII(Pc˙3-)}-·C6H4Cl2 (5) and (Cp*2Cr+){Ir4(CO)11·SnII(Pc˙3-)}2- (6). It is seen that reduced clusters are oxidized by SnIV, which is transferred to SnII, whereas the Pc2- macrocycle is reduced to Pc˙3-. In the case of Os3(CO)12, oxidation of the metal atom in the cluster is observed to be accompanied by the formation of Os3(CO)10Cl with one OsI center. Rather weak magnetic coupling is observed between paramagnetic Cp*2Cr+ and {SnII(Pc˙3-)}- species in 4, but this exchange interaction is enhanced in 5 owing to Os3(CO)10Cl clusters with paramagnetic OsI (S = 1/2) also being involved in antiferromagnetic coupling of spins. The formation of {SnII(Pc˙3-)}- with radical trianion Pc˙3- macrocycles in 2-5 is supported by the appearance of new absorption bands in the NIR spectra and essential Nmeso-C bond alternation in Pc (for 3-5). On the whole, this work shows that both diamagnetic {SnII(Pc2-)}0 and paramagnetic {SnII(Pc˙3-)}- ligands substitute carbonyl ligands in the transition metal carbonyl clusters, forming well-soluble paramagnetic solids absorbing light in the visible and NIR ranges.

Sulfation of arabinogalactan with sulfamic acid under homogeneous conditions in dimethylsulfoxide medium.

Sulfation of larch wood arabinogalactan (AG) with sulfamic acid in dimethylsulfoxide (DMSO) medium in the presence of urea was studied for the first time. The use of DMSO as a solvent instead of more toxic 1,4-dioxane allows to sulfate AG under homogeneous conditions. The sulfated AG with a high sulfur content (12.0–12.5 wt %) was produced by sulfation at a temperature of 85–90 °C, the molar ratio of AG / sulfating agent equal to 1:0.85 during 2–3 h. The introduction of sulfate groups into the structure of arabinogalactan was confirmed by the appearance of new absorption bands in FTIR and FT Raman spectra, characteristic for the vibrations of the sulfate groups. It was proved by 13C NMR spectroscopy that the predominant substitution of the primary hydroxyl groups at C6 carbon atoms of the terminal galactose units of main and side chains of arabinogalactan takes place. Simultaneously, the hydroxyl groups associated with C2 and C4 carbon atoms of galactose unit of the main chain are only partially sulfated. According to results of GPC study, the sulfated AG is characterized by a narrow molecular weight distribution with an average molecular weight of 18.8 kDa and a polydispersity of 1.3.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00226-021-01341-2.

Determination of Surface Acidity on The Natural and Synthetic Montmorillonite Clays by Titration Method

Determination of surface acidity on the natural and synthetic montmorillonite clays has been carried out using the acid-base titration method to count the number of bound acid sites per gram of clay. The total acidity of natural and synthetic montmorillonite surfaces obtained was 4.67 and 5.33 mmol/g, respectively. FTIR analysis results indicate the presence of functional groups from the tetrahedral and octahedral constituents. Both samples have similar absorption patterns. The similarity of absorption patterns was followed by a decrease in intensity and shift in some absorption bands, and the appearance of new absorption bands.

Preparation of Chemically Modified Lignin-Reinforced PLA Biocomposites and Their 3D Printing Performance.

Using a simple esterification reaction of a hydroxyl group with an anhydride group, pristine lignin was successfully converted to a new lignin (COOH-lignin) modified with a terminal carboxyl group. This chemical modification of pristine lignin was confirmed by the appearance of new absorption bands in the FT-IR spectrum. Then, the pristine lignin and COOH-lignin were successfully incorporated into a poly(lactic acid) (PLA) matrix by a typical melt-mixing process. When applied to the COOH-lignin, interfacial adhesion performance between the lignin filler and PLA matrix was better and stronger than pristine lignin. Based on these results for the COOH-lignin/PLA biocomposites, the cost of printing PLA 3D filaments can be reduced without changing their thermal and mechanical properties. Furthermore, the potential of lignin as a component in PLA biocomposites adequate for 3D printing was demonstrated.

Synthesis, characterization and fuel parameters analysis of linseed oil biodiesel using cadmium oxide nanoparticles

Linseed oil biodiesel (LSOB) was synthesized from linseed oil by cadmium oxide nanoparticles applying transesterification reaction of oil with methanol. Cadmium oxide nanoparticles were synthesized through the hydrothermal method using cadmium acetate as precursor, sodium hydroxide for precipitation and urea as capping agent. The main analytical tools such as FT-IR, powder XRD and SE microscope were used to characterize newly prepared cadmium oxide nanoparticles. The appearance of new absorption band at 670 cm−1 has been assigned to Cd–O stretching vibration. XRD pattern indicate the purity and gave average particle size of 52 nm by Debye-Scherer formula. SEM images show granular shape of cadmium oxide nanoparticles with average particle size of 43 nm. The formation of linseed oil biodiesel was investigated using FT-IR and proton & carbon-13 NMR. GC-MS analysis of linseed oil biodiesel indicated six types of fatty acid methyl esters ranging from C16–C22 (mixture of both saturated and unsaturated). The fuel properties such as density, viscosity, cloud, pour and flash point were determined and compared with both ASTM standards for biodiesel and diesel.

Optical and thermal studies of modified terephthaldehyde–acetone polymer

Terephthaldehyde–acetone polymer was synthesized in an attempt to study its different structural and spectroscopic aspects along with thermal stability. The effect of modification was studied by introducing 4,5-dihydro-1 H-pyrazole ring in the polymer chain and silver nano particles (Ag NPs). The structural features of the polymer are supported by scanning electron microscope (SEM), Fourier transform infrared, and X-ray diffraction (XRD) studies. The modification of the polymer is indicated by the appearance of new absorption bands in infrared spectra, due to the formation of dihydropyrazole ring and the interaction of Ag NPs with the main chain of the polymer. XRD revealed the amorphous polymer with an improved degree of crystallinity in the case of nanocomposites. The polymer was found thermally stable up to 210°C, and the stability improved by the addition of 4,5-dihydro-1 H-pyrazole (325°C) and Ag NPs (up to 360°C). The polymer looks fibrous in SEM micrographs and a decrease in this character is observed on modification. The optical and fluorescence properties warrant its use in LEDs and as an ultraviolet absorber.

IR absorption spectra of high-pressure polyethylene modified by fish scales

We study polymeric-based composite materials with nanostructured metal filler and bio-filler; they protect the material from environmental influences, including oxidation, and give the required flexibility to the composite, subject to biocompatibility. Composites were obtained from a homogeneous mixture of the powders of the matrix components and the filler using a heated press at a temperature of 420 K and a pressure of 15 MPa. The quenching crystallization mode is the rapid cooling of samples in a water–ice mixture. The results of a study of IR spectra taken with a Fourier spectrometer Varian 640 FT-IR, high-pressure polyethylene composites modified with biological filler, and LDPE [Formula: see text] vol.% FS [Formula: see text] vol.% Fe bio-nanocomposites in the frequency range 4000–400 cm[Formula: see text] were presented. It was revealed that the introduction of modifiers from fish scales (FS) and metallic nanoparticles (Fe) in LDPE in an optimal amount does not contribute to the appearance of new absorption bands, i.e. it practically does not change the shape of their IR spectrum. This means that the modifier of biological origin is technologically compatible with LDPE. The introduction of fish scale filler to LDPE contributes to a noticeable decrease in the intensity of the formation of C–O groups (1720 cm[Formula: see text]), which is a measure of the oxidative degradation of polymer chains. The results show that the introduction of FS into the structures of high-pressure polyethylene contributes to the formation of an optimal and stable structure, which, in turn, interferes with the intensive development of the photooxidative process caused by UV irradiation.

Enacting Two-Electron Transfer from a Double-Triplet State of Intramolecular Singlet Fission.

A simulation-led strategy enacts two-electron transfer between an intramolecular singlet fission chromophore (tetracyanomethylene quinoidal bithiopehene with β,β'-solubilizing groups) and multielectron acceptor (anthraquinone). The thermodynamic plausibility of multielectron transfer from a double-triplet state and the absorption spectra of electron transfer (ET) products were predicted using quantum chemical simulations. These predictions are consistent with experimental observations of reduced lifetimes in time-resolved fluorescence spectroscopy, changes in transmission profile, and appearance of new absorption bands in transient absorption spectroscopy, all of which support multi-ET in the QOT2/AQ mixture. The analysis suggests 2ET is favored over 1ET by a 2.5:1 ratio.

Spectral analysis and DFT computations of the hydrogen bonded complex between 2,6-diaminopyridine with 2,6-dichloro-4-nitrophenol in different solvents

New hydrogen bonded complex between 2,6-dichloro-4-nitrophenol (DCNP), proton donor with the proton acceptor 2,6-diaminopyridine (DAP) has been synthesized and characterized in solution and solid state by different spectroscopic techniques. Electronic spectra were used to identify the novel proton transfer complex through appearance of new absorption bands in acetonitrile (CH3CN), methanol (CH3OH) and mixture composed from 1:1 methanol and acetonitrile (AN-Me). The complex stoichiometry was determined to be 1:1 by job's method and photometric titrations. The formation constant was determined by applying minimum-maximum absorbances method where it reached high values confirming the complex high stability. A spectroscopic method for determining DAP was presented and validated statistically. The solid complex was characterized by elemental analysis, infrared and 1H NMR studies where the hydrogen bonded reaction occurs between the phenolic OH with the pyridine ring nitrogen as well as one amino group of DNP. The density functional theory DFT (B3LYP) method has been used to energy optimization of the reactants and complex in the ground state using two basis sets 6-31G(d) and 6–31 G+(d,p). The first one led to energy optimized structure through bifurcated hydrogen bond between OH of DCNP with the ring nitrogen and one amino group of DAP with optimization energy −1998.7 Hartree. The second one gave an optimized structure thought hydrogen bonding between OH and one amino group with lowered optimization energy −2018.1 Hartree. Hence, the experimental results will be simulated with the most stable one at DFT/B3LYB 6-31G+ (d,p). The most reactive electrophilic and nucleophilic sites of DCNP and DAP were predicted using the molecular electrostatic potential. The theoretical electronic spectra in the gas phase and the investigated solvents were calculated at TD-DFT/B3LYP 6-31G+ (d,p) and compared with measured electronic spectra where a satisfactory results have been obtained. An important aim of this work is analysis of the interaction energies between the filled natural bond orbitals (NBOs) and the empty ones in order to shed the light on the ease of electron delocalization among bonds in the novel hydrogen bonded complex.

Glutathione binding to dirhodium tetraacetate: a spectroscopic, mass spectral and computational study of an anti-tumour compound.

Glutathione (γ-l-glutamyl-l-cysteinyl-glycine) is a ubiquitous tripeptide found in all plants and animals. Glutathione has key roles as a metallochaperone and as a cellular thiol involved in metabolism. Little is known about how glutathione interacts with organometallic compounds in vivo. Here, we report the reactions of glutathione in vitro with dirhodium(ii) tetraacetate (tetrakis(μ-acetato)dirhodium(ii), Rh2(OAc)4), a compound with anti-tumour properties. Electrospray ionization mass spectrometry, UV-Visible absorption and circular dichroism spectroscopic methods were used to determine the stoichiometries and optical properties of the final conjugate. Computational analyses were used to predict the binding modes of glutathione to the Rh2(OAc)4, and report on the orbital assignments for the resulting products. We explored the competition by GSH for methionine-bound axial sites on Rh2(OAc)4 to investigate the use of weak thioether to protect its cellular-based anti-cancer activity. Our study highlights the important role that axial ligation would play in deactivating or significantly decreasing the efficacy of this bimetallic anti-tumor drug. The computational data explain the stability of the mono-adduct and the appearance of new absorption bands in the UV region including retention of the Rh-Rh single bond. Additionally, these data show that glutathione can effectively disable the potency of these metallo-drugs through orbital overlap of the entire Rh-Rh core as a result of the strong binding. Electronic absorption spectroscopy, mass spectrometry and computational analysis are a powerful combination in understanding possible chemical reactions in vivo and this information can be used to synthetically tune dirhodium complexes for use in the fight against cancer.

Spectroscopic analysis of aluminum chloride phthalocyanine in binary water/ethanol systems for the design of a new drug delivery system for photodynamic therapy cancer treatment

This study evaluated the behavior of aluminum chloride phthalocyanine in a binary water/ethanol mixture using electronic absorption spectroscopy and static and time-resolved fluorescence spectroscopy. The electronic absorption spectra, resonance light scattering and fluorescence quenching of aluminum chloride phthalocyanine in water/ethanol mixtures were studied at several concentrations. The electronic absorption spectra and fluorescence quenching changed significantly at approximately 50% water (v/v). Below 50% water, the dimerization constant values were negative (−2609.2M−1 and −506.5M−1 at 30% and 40% of water, respectively), indicating that the formation of aggregates under these conditions is not favored. However, at 50% water, the dimerization constant value was estimated to be 559.7M−1, which indicates the presence of dimers. Above 60% water, the aggregation process was responsible for the balance between large complexes (such as trimers, tetramers or oligomers) formed in the medium under these conditions. The appearance of new absorption bands at 387nm and 802nm and their bathochromic shift relative to the monomer bands suggested that some J-type aggregates form. These results are relevant to understanding the behavior and use of aluminum chloride phthalocyanine in the design of new drug delivery systems for clinical application in photodynamic therapy as a new approach to treat skin cancer.

A Mechanistic Study of Perfluorosulfonic Acid Membrane Water Permeance Degradation in Air

Chemical degradation of perfluorosulfonic acid (PFSA) membranes of proton exchange membrane (PEM) fuel cells is a well-known process which can limit PEM fuel cell lifetimes (1, 2). Chemical degradation can weaken membranes to the point where they no longer provide an effective barrier to reactant gas permeation or electrical shorting. PEM chemical degradation is the result of a complex interplay between mechanical and chemical degradation processes, both of which are strong functions of operating conditions. In particular, hot and dry operating conditions induce high rates of chemical degradation whereas relative humidity cycling between wet and dry states challenges the mechanical integrity of the membranes. Because chemical degradation of PEMs is accelerated under low humidity operating conditions, membrane lifetimes are significantly enhanced by providing humidified inlet gas streams to the fuel cell stack. In addition, fuel cell performance is improved with the use of humidified input streams. An efficient method of humidifying the cathode inlet stream employs a passive water vapor transfer (WVT) device that delivers water vapor from the wet cathode exhaust to the cathode inlet stream (Figure 1). The key component of a WVT device is a highly water permeable, but gas impermeable membrane. Not surprisingly, ionomeric membranes such as PFSAs function as excellent WVT materials. Ideally, WVT membrane materials will maintain adequate durability and performance characteristics to provide necessary stack humidification throughout the target operational life of an automotive fuel cell system (>10years />8000 operational hours). Several general pathways known to reduce water permeance values include cation contamination, mechanical degradation and chemical degradation. We have observed during in-situ and ex-situ testing of WVT materials in air that the water permeance values of PFSA-based WVT membranes can degrade by 75% over time. This degradation of water permeance is associated with a physical and chemical change of the membrane. The extent of ionomer transformation is readily monitored using transmission FTIR spectroscopy by the appearance of new absorption bands centered at 3200 and 1434 cm-1 and also by the decreases in water stretching and bending bands centered near 2800 and 1700 cm-1, respectively (Figure 2). In addition to water permeance, other membrane properties including proton conductivity and ion exchange capacity decrease as a function of this degradation reaction. The fully reversible, deuterium exchanged FTIR spectrum proves that the degradation product is not the cross-linked sulfonic acid anhydride as previously suggested (3). Through an extensive series of kinetic studies and analytical characterization, we have determined that the membrane degradation product results from a reaction between the ionomer and a trace atmospheric gas. We will demonstrate that the definitive structural assignment is fully consistent with all known properties and behaviors of the degraded membrane. The revelation of the PFSA degradation product and its formation mechanism will aid in development of highly durable fuel cell systems. References R. Borup, J. Meyers, B. Pivovar, Y. Kim, R. Mukundan, N. Garland, D. Meyers, M. Wilson, F. Garzon, D. Wood, P. Zelenay, K. More, K. Stroh, T. Zawodzinski, J. Boncella, J. McGrath, M. Inaba, K. Miyatake, M. Hori, K. Ota, Z. Ogumi, S. Miyata, A. Nishikata, Z. Siroma, Y. Uchimoto, K Yasuda, K. Kimijima, N. Iwashita, Chem. Rev. 107, 3904, (2007)C. S. Gittleman, F. D. Coms, Y-H. Lai, Membrane Durability: Physical and Chemical Degradation, in Polymer Electrolyte Fuel Cell Degradation, pp 15-88, M. M. Mench, E. C. Kumbur, T. N. Veziroglu, eds, Academic Press, 2012F. M. Collette, C. Lorentz, G. Gebel, F. Thominette, J. Mem. Sci. 330, 21-29, (2009) Figure 1

Thermodynamic aspects of aurophilic hydrogelators.

The complexes [Au(4-pyridylethynyl)(phosph)] (phosph = PTA (1), DAPTA (2)) are known to produce supramolecular aggregates and gels in water. We studied the impact of these aggregation processes in the absorption spectra, (1)H NMR (at different temperatures and concentrations), and DLS and estimated the equilibrium constant for a single step aggregation of the molecule (K = 26760 and 2590 M(-1) for 1 and 2, respectively, at 25 °C). We present spectroscopic evidence for the presence of Au···Au contacts in the aggregates: the recorded changes on (1)H NMR and the appearance of new absorption bands assigned to (σ*Au···Au-π*) have been attributed to the short (Au···Au) average distances in the aggregates. Relativistic density functional theory computations support the existence of short Au···Au distances and reveal charge-transfer in the aurophilic interactions. The free energy for a single step aggregation was calculated from the experimental data, and the value obtained (ΔG ∼ -20 kJ/mol) is in good agreement with the expected values in the order of the energies found for hydrogen bonds. The DFT computations confirm the experimental findings that aggregation of monomer 1 is stronger than the aggregation of monomer 2 and the existence of aurophilic interactions.

Absorption Spectroscopy Study of Acid-Base and Metal-Binding Properties of Flavanones

We have used absorption spectroscopy to study the acid-base and metal-binding properties of two structurally similar flavanones: taxifolin and naringenin. We have determined the acid dissociation constants for taxifolin (pKa1 = 7.10 ± 0.05, pKa2 = 8.60 ± 0.09, pKa3 = 8.59 ± 0.19, pKa4 = 11.82 ± 0.36) and naringenin (pKa1 = 7.05 ± 0.05, pKa2 = 8.85 ± 0.09, pKa3 = 12.01 ± 0.38). The appearance of new absorption bands in the visible wavelength region let us determine the stoichiometric composition of the iron (II) complexes of the flavanones. We show that at pH 5, in solution there is a mixture of complexes between taxifolin and iron (II) ions in stoichiometric ratio 2:1 and 1:2, while at pH 7.4 and pH 9, we detect a 1:1 taxifolin:Fe(II) complex. We established that at these pH values, naringenin forms a 2:1 complex with iron (II) ions. We propose structures for the complexes formed. Comprehensive study of the acid-base properties and the metal-binding capability of the two structurally similar flavanones let us determine the structure-properties relation and the conditions under which antioxidant activity of the polyphenols appears, via chelation of variable-valence metal ions.

Spectroscopic studies and molecular orbital calculations on the charge transfer reaction between DDQ and 2-aminopyridine

Charge transfer complex formation between 2-aminopyridine (donor, 2AP) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (acceptor, DDQ) has been studied spectrophotometrically in acetonitrile (CH3CN). The newly formed CT-complex has reddish brown color and is characterized by the appearance of new absorption bands in the 375–650nm regions where acceptor and donor do not have any absorption. Maximum and constant absorbance of the complex was obtained after 10min at 20°C with 1mL 5×10−3M DDQ in CH3CN. Based on photometric titration method, the stoichiometry of the formed CT-complex was found to be 1:1 [(2AP)(DDQ)]. Minimum–maximum absorbances method has been applied to estimate the formation constant of the complex where it recorded large value confirming its high stability. Molecular orbital calculations utilizing GAMESS computations were carried out in order to record changes in the electronic structure and molecular geometry of the formed CT-complex. In addition, the infrared vibrational frequencies of the complex were computed and compared with experimental results.

Colorimetric sensing of cyanide anion in aqueous media with a fluorescein–spiropyran conjugate

A fluorescein–spiropyran conjugate ( 2) behaves as a receptor for colorimetric sensing of cyanide anion (CN −) in aqueous media under irradiation of UV light. The compound 2, which exists as a spirocycle-closed (SP) form in the dark condition, is isomerized to the spirocycle-opened merocyanine (MC) form upon irradiation of UV light and shows absorption bands at 467 and 568 nm. Addition of CN − to the solution leads to a decrease in these bands and an appearance of new absorption band at 512 nm, via a nucleophilic interaction between CN − and the spirocarbon of MC form. This absorption change occurs selectively with CN − and enables ratiometric quantification of CN − by absorption analysis.

Core-functionalized dendritic oligothiophenes—novel donor–acceptor systems

Novel core-functionalized dendritic oligothiophenes (DOT) bearing pyridine or methylpyridinium acceptors have been synthesized up to the third generation. A bathochromic shift in the absorption of the functionalized dendritic oligothiophenes and the appearance of new absorption bands were noticed issuing from an intramolecular charge transfer process. These novel donor–acceptor systems are, due to their broad absorption, promising materials for optoelectronic applications such as organic solar cells. By electrochemical measurements HOMO/LUMO energy levels have been determined and two compounds could be identified with almost ideal energy levels for application in bulk heterojunction solar cells (BHJSC) with fullerene PC61BM as acceptor.

Cyclopalladated ethylenediamine complexes on the basis of 4-phenylpyrimidine and 4,6-diphenylpyrimidine

Mono-and binuclear cyclopalladated complexes [Pd(ppm)En]ClO4, [Pd(Hdphpm)En]ClO4, and [(PdEn)2(μ-dphpm)]ClO4 (ppm− is the deprotonated form of 4-phenylpyridine, Hdphpm− and dphpm2− are the mono-and bisdeprotonated forms of 4,6-diphenylpyrimidine, En is 1,2-diaminoethane) were prepared and characterized by means of 1H NMR and electronic absorption and emission spectroscopy, and cyclic voltammetry. It was shown that cyclopalladation leads to a bathochromic shift of intraligand absorption and phosphorescence bands, appearance of new absorption band associated with metal-to-ligand charge transfer, and an anodic potential shift of the ligand-centered electroreduction Hppm ≈ H2dphpm < [Pd(ppm)En]+ ≈ [Pd(Hdphpm)En]+ < [(PdEn)2(μ-dphpm)]2+.

Photocatalytic degradation of Orange G on nitrogen-doped TiO 2 catalysts under visible light and sunlight irradiation

In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO 2 photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO 2 nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO 2, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H 2O 2 was 5.0 and 15.0 mmol/l, respectively.