Nickel sulphide-reduced graphene oxide composites as counter electrode for dye-sensitized solar cells: Influence of nickel chloride concentration

Nickel sulphide-reduced graphene oxide (NiS-rGO) composite films have been prepared via modified Hummers’s method assisted with spin coating technique. The NiS-rGO samples were then employed as counter electrode in a dye-sensitized solar cell (DSSC). The main aim of this work is to investigate the relationship between the concentrations of NiCl₂ with the properties of NiS-rGO and performance parameters of the device. The dominant rGO and minor NiS phase exist in the composite. The morphology of the composite is white strips rGO and NiS agglomerate particle. The element of C, O, Ni and S present in the composite. The highest η of 1.04% and J_sc of 7.39 mA cm⁻² were obtained from the device with 0.06 M NiCl₂ resulted from the longest carrier lifetime. The photovoltaic parameters results reveal that NiS-rGO composite has potential to become as a free platinum counter electrode of DSSC.     

cis-oxypalladation complexes of a pinene derivative

4-Methoxy- and 4-acetoxy(3,2,10-η-pinene)palladium complexes prepared from dehydro-β-pinene with Na₂PdCl₄ in MeOH and Pd(OAc)₂ in AcOH, respectively, represent the first isolated cis-oxypalladation adducts.     

Influence of Pd precursors on the catalytic performance of Pd–H4SiW12O40/SiO2 in the direct oxidation of ethylene to acetic acid

The effects of palladium precursors (PdCl₂, (NH₄)₂PdCl₄, Pd(NH₃)₂Cl₂, Pd(NO₃)₂ and Pd(CH₃COO)₂) on the catalytic properties in the selective oxidation of ethylene to acetic acid have been investigated for 1.0 wt% Pd–30 wt% H₄SiW₁₂O₄₀/SiO₂. The structures of the catalysts were characterized using X-ray diffraction, N₂ adsorption, H₂-pulse chemical adsorption, infrared spectrometry of the adsorbed pyridine, H₂ temperature-programmed reduction and X-ray photoelectron spectroscopy. The present study demonstrates that the different palladium precursors can lead to the significant changes in the dispersion of palladium. It is found that Pd dispersion decreases as follows: PdCl₂ > (NH₄)₂PdCl₄ > Pd(NO₃)₂ > Pd(NH₃)₂Cl₂ > Pd(C₂H₃O₂)₂, which is nearly identical to the catalytic activity. This indicates that the dispersion of palladium plays an important role in the catalytic activity. Furthermore, density of Lewis (L) and Brönsted (B) acid sites are also strongly dependent on the palladium precursors. It is also demonstrated that an effective catalyst should possess a well combination of Brönsted acid sites with dispersion of palladium.     

New bimetallic organopalladium(II) compounds containing a PdCo or PdMo bond trans to a PdC bond

The reaction of a chelated palladium compound with Co(CO)^?₄ and [Mo(CO)₃-η-C₅H₅]^? gives new stable bimetallic PdCo and PdMo complexes in which the metal-metal bond is trans with respect to the Pd-carbon σ-bond.     

Factors determining the chemoselectivity of phosphorus-modified palladium catalysts in the hydrogenation of chloronitrobenzenes

The precursor nature effect on the state of the Pd–P surface layer in palladium catalysts and on their properties in the liquid-phase hydrogenation of chloronitrobenzenes under mild conditions has been investigated. A general feature of the Pd–P-containing nanoparticles obtained from different precursors and white phosphorus at P/Pd = 0.3 (PdCl₂ precursor) and 0.7 (Pd(acac)₂ precursor) is that their surface contains palladium in phosphide form (BE(Pd3d _5/2) = 336.2 eV and BE(Р2р) = 128.9 eV) and Pd(0) clusters (BE(Pd3d_5/2) = 335.7 eV). Factors having an effect on the chemoselectivity of the palladium catalysts in chloronitrobenzenes hydrogenation are considered, including the formation of small palladium clusters responsible for hydrogenation under mild conditions.     

Synthèse et analyse radiocristallographique de la solution solide K2PdCl4–xBrx (0 < x < 4)

Preparation and crystal structure determination (by X-ray single crystal measurements) of the K₂PdCl_2.81Br_1.19, K₂PdCl_2.64Br_1.36, K₂PdCl_2.41Br_1.59, K₂PdCl_1.73Br_2.27, and K₂PdCl_0.99Br_3.01 compounds are reported. All these compounds crystallise in the same centrosymmetric space group P4/mmm. The tetragonal cell (a ≈ 7.3 Å; c ≈ 4.2 Å) contains one Pd atom, which lies on the C4 axis. The square-planar 〚PdX₄〛^2– ions (X = Cl, Br) are disordered. The Pd–X distances (2.348(2), 2.356(2), 2.362(2), 2.383(1), and 2.422(2) Å) have intermediate values between those previously observed for Pd–Cl (2.313 Å) in the K₂PdCl₄ compound and Pd–Br (2.444 Å) in the K₂PdBr₄ compound.     

Cyclic and stripping voltammetry of Se(+4) and Se(−2) at the HMDE in acidic media

Electroreduction of Se(+4) and electrooxidation of Se(?2) were studied at mercury electrodes in acidic media and an improved mechanism of the reduction process was proposed. This mechanism takes into account the fact that the reduction path is concentration-dependent. At lower concentrations of Se(+4), mercury selenide and hydrogen selenide are formed at various potentials. At higher Se(+4) concentrations the electrode quickly becomes covered by a rigid deposit of mercury selenide and then the reduction starts to proceed to elemental selenium. Another form of selenium was formed in the vicinity of the mercury surface due to a chemical reaction between H₂SeO₃ and H₂Se. Oxidation of hydrogen selenide proceeds similarly, in the sense that after coverage of the electrode surface by a deposit of mercury selenide the oxidation starts to proceed to elemental selenium. The cathodic stripping peak of mercury selenide can be obtained down to 2 × 10^?8M of Se(+4), but this peak is often split and therefore the determination of traces of Se(+4) by the cathodic stripping technique is cumbersome.     

Effect of organic dye on the performance of dye-sensitized solar cell utilizing TiO2 nanostructure films synthesized via CTAB-assisted liquid phase deposition technique

This work is concerned with the growth of TiO₂ nanostructures as photovoltaic materials of dyesensitized solar cell (DSSC) via phase liquid deposition technique treated with CTAB surfactant. This work investigates the influence of organic dyes, N719, N3 and Z907 as photosensitizer on the photovoltaic parameters of TiO₂ nanostructures dye-sensitized solar cells (DSSCs). It also highlights the effect of the concentration of the best dye, N719 on the performance of the cell. The platinum films as counter electrode of the DSSC were prepared by sputtering platinum pellet on ITO substrate. The redox couple of the electrolyte utilized in the DSSC was iodide/triiodide. The cell sensitized with N719 dye demonstrated the best performance compared with the cell sensitized with another two dyes, N3 and Z907. This is due to N719 dye possess the highest optical absorption in visible region. The cell sensitized with 0.8 mM N719 dye performs the highest short-circuit current density, J _sc and power conversion efficiency, η since it posses the highest absorption in visible region. The DSSC utilizing 0.8 mM N719 dye demonstrated the highest J _sc and η of 6.48 mA cm^?2 and 1.69%, respectively.     

Spectroscopic,biological activity studies,and DFT calculations,of Pd(II) and Pt(II) complexes of 4-Methylene-3-phenyl-3,4-dihydroquinazoline-2(1H)-thione

Four palladium (II) and platinum(II) complexes with the formula [MCl₂(HPhqS)₂] and [M(PhqS)₂] (M^II = Pd and Pt), were synthesized by treating Na₂PdCl₄ or K₂PtCl₄ with 2 mol of 4-Methylene-3-phenyl-3,4-dihydroquinazoline-2(1H)-thione (HPhqS) with or without the present base. The geometry around the Pd(II) and Pt(II) ions was a square planner and the HPhqS ligand was bonded as monodentate through the sulfur atom in complexes (1) and (2), while as bidentate chelating ligand through the nitrogen and sulfur atoms in complexes (3) and (4) as revealed by the data collection from spectroscopic studies. The prepared compounds were fully characterized by different physicochemical and spectroscopic methods. Furthermore, the free HPhqS ligand and its complexes were evaluated in vitro in regard to their antimicrobial activity against five bacteria species (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, staphylococcus epidermidis and staphylococcus aureus). Moreover, the cytotoxic activity of the compounds was examined against breast (MCF-7) and lung (A549) cancer cell lines, and the [PdCl₂(LH)₂] (1) and [PtCl₂(LH)₂] (2) appeared a highest inhibitory effect against MCF-7 cell lines with IC₅₀ = 4.291 ± 0.181 μM and 3.479 ± 0.162 μM, respectively, in comparison to the standard control and other complexes. The prepared ligand accompanied by the synthesized complexes were optimized using B3LYP method and 6–311++G(d,p) biases sets for the ligand and SDD basis set for the central metal. Different quantum parameters including electron affinity, ionization energy, dipole moment, hardness and vibrational frequencies were calculated for the ligand and its complexes. The total energy calculated for the two tautomeric structures of the ligand HPhqS showed a slightly higher value of the thione form over the thiol form. In addition, the trans-[PdCl₂(HPhqS)₂] complex possessed the highest dipole moment values while the cis-[PtCl₂(HPhqS)₂] showed non. In general, the obtained theoretical results showed a good match to the experimental findings.     

Liquid-liquid extraction and spectrophotometric determination of palladium with 2-mercaptobenz-amide

2-Mercaptobenzamide (MBA) was investigated as a reagent for the extraction of palladium. The palladium complex of MBA was extracted into tributyl phosphate (TBP). The pK_a of the ligand was 5.45 with the stability constant of the palladium complex β₂=10^7.1. The composition of the complex in TBP was Pd:MBA:TBP=1:2:2. Addition of sodium chloride accelerated the rate of extraction. Various interfering ions could be masked with EDTA; Ag(I), Au(III), Os(VIII), Se(IV), Te(IV) etc. interfered. The molar absorptivity was 1.59×10⁴ l mol^?1 cm^?1; 1–35 μg Pd could be determined at pH 6.0.     

Use of INAA to study the effect of selenium on uranium accumulation in cells of saccharomyces cerevisiae

Differences in the effects of seleno-cystine (CySe)₂ and inorganic Se(IV) and Se(VI) compounds on uranium(VI) uptake by yeast cells, Saccharomyces cerevisiae have been studied. The Se, U, Zn and Co levels of the yeast cells were measured by neutron activation analysis. An increase in the concentration of U cells within the first 2 hours of incubation was produced by the presence of SeO₂ (2·10^–4–5·10^–4M) and (CySe)₂ (1·10^–4M) in the yeast medium. Moreover, the highest SeO₂ concentration (5·10^–4M) and (CySe)₂ more efficiently enhanced the U content of the cells than SeO₂ at the low concentration end (2·10^–4M). However, the effect of SeO₂ and (CySe)₂ on U uptake diminishes with incubation time (from 2 to 48 hours). Se(VI) [as (NH₄)₂SeO₄] leads to a marked decrease in the content of uranium in Saccharomyces cerevisiae (an antagonistic interaction). As expected, uranium uptake by the yeast influence the retention of selenium in the cells. Uranium significantly increased the uptake yield of Se by Saccharomyces cerevisiae when the yeast was incubated in the medium containing (CySe)₂. Furthermore, during the initial 24 hours of the incubation an increase of the Se content of the cells in the presence of U was observed when Se(VI) was in the culture medium. Selenium and uranium dosages affected the Zn and Co contents of cells.     

Acyclic tetrachalcogenoether ligands tethered with bulky substituents: Their syntheses and coordination chemistry

New o-phenylene-bridged tetrachalcogenoether ligands tethered with an extremely bulky substituent, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) group, [TbtE(o-phenylene)Se]₂(o-phenylene) (3: E = S, 4: E = Se), were synthesized. Complexation reactions of 3 and 4 with Na₂PdCl₄ gave the corresponding dichloropalladium(II) complexes 7 and 8. X-ray structural analysis of 7 and 8 indicated that the central palladium metals are in a distorted octahedral environment, where the two inner selenium atoms and the two chlorine atoms form a square planar arrangement around the palladium metal and the two terminal chalcogen atoms weakly coordinate to the palladium center at the axial positions. The AIM calculations also supported the existence of the interaction between the palladium and the terminal chalcogen atoms in the crystalline state. On the other hand, the ⁷⁷Se NMR spectra suggested that there are no or very weak interactions between the palladium and the terminal chalcogen atoms in solution. The UV/Vis spectra of 7, 8, and related compounds imply the possibility of weak interaction between the terminal selenium atoms and the palladium center in solution.     

A highly efficient electric additive for enhancing photovoltaic performance of dye-sensitized solar cells

N-cetylpyridinium iodide (N-CPI) as a new electric additive for enhancing photovoltaic performance of the dye-sensitized solar cell (DSSC) was studied. It showed high efficiency for enhancing both the open-circuit voltage and the short-circuit current density of DSSC when the suitable amount of N-CPI as 0.02 M was added in liquid electrolyte. The energy conversion efficiency of DSSC increased from 4.429% to 6.535%, with 47.55% enhancement. Therefore, it is a highly efficient electric additive for DSSC. The intrinsic reason is owing to the special molecular structure of N-CPI, which contains two different polarity groups. As a surfactant, N-CPI could form ordered arrangement in liquid electrolyte, which affects the diffusing ability and the redox reaction of I^?/I ₃ ^? , and further affects the photovoltaic performance of DSSC.     

Aromatic polycarbonates by direct synthesis from bisphenol a and carbon monoxide

Oxidative carbonylation of bisphenol A to polycarbonates has been studied using mixtures of carbon monoxide and oxygen in the presence of a host of catalytic systems. Catalysts containing palladium compounds and selenium, as well as PdCl₂/Fe/I₂ and Pd/Fe/I₂ catalytic systems, exhibit different selectivity and activity towards the products obtained. This revised version was published online in June 2006 with corrections to the Cover Date.     

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

We report a simple and efficient procedure for Suzuki–Miyaura reactions in aqueous media catalysed by amidophosphine‐stabilized palladium complexes trans‐{L³PPh₂}₂PdCl₂ ( 3 ), trans‐{L³PPhtBu}₂PdCl₂ ( 4 ), [Pd(η³‐C₃H₅)(L³PPh₂)Cl] ( 5 ) and {Pd[2‐(Me₂NCH₂)C₆H₄](L³PPh₂)Cl} ( 6 ). The acidity of the NH proton in complexes 3 , 4 , 5 , 6 plays an important role in their catalytic activity. In addition, the palladium complexes cis‐{L¹PPh₂}PdCl₂ ( 1 ) and trans‐{L²PPh₂}₂PdCl₂ ( 2 ) stabilized by phosphines containing Y,C,Y‐chelating ligands L^1,2 have also been found to be useful catalysts for Suzuki–Miyaura reactions in aqueous media. The method can be effectively applied to both activated and deactivated aryl bromides yielding high or moderate conversions. The catalytic activity of couplings performed in pure water increases when utilizing a Pd complex with more acidic NH protons. A decrease of palladium concentration from 1.0 to 0.5 mol% does not lead to a substantial loss of conversion. In addition, Pd complex 1 can be efficiently recovered using two‐phase system extraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Palladium complexes of P,P and P,S type bidentate ligands: Implication in Suzuki–Miyaura cross-coupling reaction

New palladium complexes of the type [PdCl₂(η²–P∩P)] (1a,1b) and [PdCl₂(η²–P∩S)] (1c,1d) have been synthesised by the reaction of PdCl₂ with P,P and P,S type bidentate ligands in 1:1 mol ratio, where, P∩P = 9,9–dimethyl-4,5-bis(diphenylphosphanyl) xanthene {Xantphos}(a) or bis(2-diphenylphosphanylphenyl)ether{DPEphos}(b); P∩S = 9,9-dimethyl-4,5-bis(diphenyl -phosphanyl) xanthenemonosulfide {Xantphos(S)}(c) or bis(2-diphenylphosphanyl phenyl) ether monosulfide {DPEphos(S)}(d). The complexes are characterized by elemental analyses, mass spectrometry, ¹H, ¹³C and ³¹P NMR spectroscopy together with the single crystal X-ray structure determination of 1a and 1d. The palladium atom in all the complexes occupies the centre of a slightly distorted square planar environment formed by a P atom, a P/S atom and two Cl atoms. The catalytic activities of 1a–1d investigated for Suzuki–Miyaura cross-coupling reactions at room temperature exhibit higher yield of the coupling products than catalysed by PdCl₂ itself. Among 1a–1d, the palladium complexes of bidentate phosphine (1a, 1b) show higher efficacy than their monosulfide analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected coupling reaction between 4-bromobenzonitrile and phenylboronic acid exhibit that 1c and 1d are more efficient than 1a and 1b, which may be due to the donor effect of the P,S ligands during catalytic reaction.     

Palladium complexes of P,P and P,S type bidentate ligands: Implication in Suzuki–Miyaura cross-coupling reaction

New palladium complexes of the type [PdCl₂(η²–P∩P)] (1a,1b) and [PdCl₂(η²–P∩S)] (1c,1d) have been synthesised by the reaction of PdCl₂ with P,P and P,S type bidentate ligands in 1:1 mol ratio, where, P∩P = 9,9–dimethyl-4,5-bis(diphenylphosphanyl) xanthene {Xantphos}(a) or bis(2-diphenylphosphanylphenyl)ether{DPEphos}(b); P∩S = 9,9-dimethyl-4,5-bis(diphenyl -phosphanyl) xanthenemonosulfide {Xantphos(S)}(c) or bis(2-diphenylphosphanyl phenyl) ether monosulfide {DPEphos(S)}(d). The complexes are characterized by elemental analyses, mass spectrometry, ¹H, ¹³C and ³¹P NMR spectroscopy together with the single crystal X-ray structure determination of 1a and 1d. The palladium atom in all the complexes occupies the centre of a slightly distorted square planar environment formed by a P atom, a P/S atom and two Cl atoms. The catalytic activities of 1a–1d investigated for Suzuki–Miyaura cross-coupling reactions at room temperature exhibit higher yield of the coupling products than catalysed by PdCl₂ itself. Among 1a–1d, the palladium complexes of bidentate phosphine (1a, 1b) show higher efficacy than their monosulfide analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected coupling reaction between 4-bromobenzonitrile and phenylboronic acid exhibit that 1c and 1d are more efficient than 1a and 1b, which may be due to the donor effect of the P,S ligands during catalytic reaction.     

Synthesis and applications of novel acceptor-donor-acceptor organic dyes with dithienopyrrole- and fluorene-cores for dye-sensitized solar cells

Four novel symmetrical organic dyes (S1-S4) configured with acceptor-donor-acceptor (A-D-A) structures containing electron donating fluorene (S1 and S2) and N-alkyl dithieno[3,2-b:2′,3′-d]pyrrole (DTP) (S3 and S4) cores terminated with two anchoring cyanoacrylic acids (as electron acceptors) were synthesized and applied to dye-sensitized solar cells (DSSCs). The DSSC device based on S2 dye showed the best photovoltaic performance among S1-S4 dyes: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 76%, a short circuit current (J_SC) of 12.27 mA/cm², an open circuit voltage (V_OC) of 0.61 V, a fill factor (FF) of 0.63, and an overall power conversion efficiency (η) of 4.73%. Besides, the utilization of chenodoxycholic acid (CDCA) as a co-adsorbent in the DSSC device based on S3 dye showed a significant improvement in its η value (from 3.70% to 4.31%), which is attributed to the suppression of dye aggregation on TiO₂ surface and thus to increase the J_SC value eventually.     

Synthesis and characterization of binuclear palladium complexes of isocyanides with novel bridging η3-indenyl ligands. Crytal structure of [Pd2(μ-η3-indenyl)2(RNC)2] (R = 2,6-dimethylphenyl)

The reaction of PdCl₂(RNC)₂ (RNC = isocyanide) with indenyl lithium (InLi) gave a binuclear palladium complex, [Pd₂(μ-η³-In)₂(RNC)₂], in which the Pd₂(RNC)₂ unit is sandwiched between two μ-η³-indenyl groups in a syn arrangement.