Efficient stabilization of in situ fabrication of PtxPd1-x nanostructures for electro-oxidation of methanol in alkaline medium

Different binary Pt_xPd_1-x alloys supported on Vulcan carbon XC-72R were synthesized by the displacement of ligands from organometallic compounds to be used as anodic electrode for methanol electro-oxidation in alkaline medium. The influence of the Pd addition during the synthesis of Pt_xPd_1-x alloys in presence of octylamine as stabilizer was analyzed in terms of structure, chemical composition and electroactivity in the methanol oxidation reaction. The X-ray photoelectron spectroscopy analysis showed that the surface of the electrodes consisted of a metallic mixture and oxide states, which confirmed the change in the electronic properties during the alloy formation. The current density of Pt₃₀Pd₇₀/C during CV measurements was about 2.1 times higher than the one observed with Pt/C electrodes. The CO tolerance was also slightly improved under similar conditions. The work findings indicate that stabilized Pt₃₀Pd₇₀/C binary alloys can be used to design highly active anodic catalysts with potential applications in direct methanol fuel cells (DMFCs).     

In situ X-ray studies of metal organic chemical vapor deposition of PbZrxTi1 − xO3

In situ synchrotron X-ray scattering and fluorescence techniques were used to simultaneously observe the evolution of the strain and composition of a growing crystal surface in real time. Control of the X-ray incidence angle allows us to obtain high surface sensitivity. We studied metal organic chemical vapor deposition (MOCVD) of epitaxial PbZr_xTi_1 − xO₃ (PZT) onto SrTiO₃ (001) substrates under various growth conditions. We observe a strong increase in Zr incorporation as strain relaxation occurs, consistent with the effect of compositional strain on the thermodynamic driving force for growth.     

压裂液用有机钛螯合物交联剂

本文介绍了有机钛整合物交联剂的化学组成、性质、交联机理,比较了TiTE、TiLA和TiAA三种不同类型的有机钛螯合物及七种商品有机钛交联剂的耐温能力。三种有机钛螯合物中,以TiTE螯合物的耐温能力最强,国内五种商品有机钛交联剂中,以万庄1号及万庄2号耐温能力最高,但比国外的DX-500耐温能力要低。在现场试验中观测到的万庄1号有机钛交联剂的耐温能力,与实验室实测结果一致。     

Synthesis and electroluminescence characterization of a new aluminium complex, [8- Hydroxyquinoline] Bis [2,2’Bipyridine] Aluminium Al(Bpy)2q

We have synthesized and characterized a new electroluminescent material, [8-Hydroxyquinoline] Bis [2,2’Bipyridine] aluminium. Solution of this material Al(Bpy)₂q in toluene showed absorption maxima at 380nm which was attributed to the moderate energy (π – π*) transitions of the aromatic rings. The photoluminescence spectrum of Al(Bpy)₂q in toluene solution showed peak at 518 nm.This material shows thermal stability up to 300₀C. The structure of the device is ITO/F4-TCNQ(1nm)/α-NPD(35nm)/Al(Bpy)₂q(35nm)/ BCP(6nm)/Alq₃(28nm)/LiF(1nm)/Al(150nm). This device exhibited a luminescence peak at 515 nm (CIE coordinates, x=0.32,y=0.49). The maximum luminescence of the device was 214 Cd/m₂ at 21V. The maximum current efficiency of OLED was 0.12 Cd/A at 13V and maximum power efficiency was 0.03 lm/W at 10 volt.     

Iron-mediated reversible deactivation controlled radical polymerization

Metal-mediated reversible deactivation radical polymerization (RDRP) is now a cornerstone of functional polymer synthesis, dominated by copper complexes and the Atom Transfer Radical Polymerization (ATRP) moniker. A limitation of this approach is the contamination of the resultant polymers by the coloured copper complexes, thus requiring further purification, although protocols to reduce the amount of copper catalyst have been developed. Iron is an interesting alternative because of its low cost, low toxicity and reduced intensity of its optical absorption spectrum. Use of this metal in RDRP began in the late 90s and has continuously intensified. This review comprehensively covers all the work reported so far on RDRP mediated by iron complexes, organized according to ligand type, and discusses the specificities of this metal in terms of the multitude of accessible spin states and the interplay of different equilibria: atom transfer vs. direct radical trapping, associative vs. dissociative exchange, chain transfer by direct β-H atom transfer vs. β-H elimination from the dormant alkyl species.     

VC3H3 organometallic compound: A possible hydrogen storage material

This work reports the hydrogen uptake capacity of V-capped and V-inserted VC₃H₃ organometallic complexes using density functional theory (DFT) with different exchange and correlation functionals. Maximum of five and three H₂ molecules are adsorbed on V-capped and V-inserted VC₃H₃ structures, respectively. This corresponds to the hydrogen uptake capacity of 10.07 and 6.66 wt% for the former and the latter, respectively. The first added hydrogen molecule is adsorbed in dihydride form on V-capped as well as V-inserted VC₃H₃ complex. A complex with a dissociated hydrogen molecule adsorbed has higher binding energy than that of molecular hydrogen adsorbed. The nature of interactions between H₂ molecules and organometallic complex is studied using many-body analysis approach. Thermo-chemistry calculations are performed to see whether H₂ adsorption on V-capped complex is energetically favorable or not for room temperature hydrogen storage.     

Optoelectronic Properties of Quasi‐Linear,Self‐Assembled Platinum Complexes: Pt–Pt Distance Dependence

Charge‐carrier mobilities of various self‐assembled platinum complexes were measured by time‐resolved microwave conductivity techniques in the temperature range –80 to +100 °C. Eight compounds were investigated in the present study, including the original Magnus' green salt ([Pt(NH₃)₄][PtCl₄]) and derivatives with the general structure [Pt(NH₂R)₄][PtCl₄], where R denotes an alkyl side chain. In one instance, the chlorines were substituted with bromines. For these complexes, which all consist of a linear backbone of platinum atoms with Pt–Pt distances, d, varying from 3.1 to ≥ 3.6 Å, a strong, inverse correlation was found between d and the one‐dimensional charge‐carrier mobility, Σμ_1D. The highest value of Σμ_1D at room temperature was observed for R = (S)‐3,7‐dimethyloctyl (dmoc) with Σμ_1D ≥ 0.06 cm² V^–1 s^–1. Almost all materials exhibited a charge‐carrier mobility that was relatively independent of the temperature over the range studied. One exceptional compound (R = (R)‐2‐ethylhexyl) showed a pronounced negative temperature dependence of the charge‐carrier mobility; upon decreasing the temperature from +100 °C to –80 °C the charge‐carrier mobility increased by a factor of about ten.     

Morphology, surface-induced orientational properties and phase transition peculiarities of lyotropic nematic mesophases in pentadecane solutions of tetranuclear platinum mesogens

We have investigated the surface-induced orientational properties and peculiarities of the phase transitions of a lyotropic system, composed of a sheet-shaped tetranuclear platinum organyl in pentadecane, and exhibiting two different lyotropic nematic mesophases (N₁ and N₂). Corrugated YBa₂Cu₃O_7−x surfaces with a sinusoidal profile have been used to induce planar orientation of these two nematic lyomesophases, which differ significantly with their orientational behavior. We have also measured the birefringence of these nematic mesophases. Based on high-accuracy determinations of the transition temperatures, we are discussing some peculiarities of the phase transitions between the two nematic mesophases and between N₂ mesophase and isotropic liquid, in particular, the width of the heterophase regions between them.     

Investigation on the effect of Tb(dbm)3phen on the luminescent properties of Eu(dbm)3phen-containing mesoporous silica nanoparticles

Eu(dbm)₃phen and Tb(dbm)₃phen complexes (tris(dibenzoylmethane) mono(1,10-phenantroline) Ln(III)) were impregnated in ordered mesoporous silica nanoparticles (MSNs) with an average size of 50–70 nm and a pore diameter centred at 2.8 nm, with the aim of increasing the luminescence by avoiding concentration quenching and having mainly in mind the application as down-shifter for multi-crystalline solar cells. The morphological, structural, textural and luminescent properties of the synthesized samples were characterized by N₂ adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–visible spectroscopy and photoluminescence measurements. It is demonstrated that inclusion in the MSNs allows one to use much higher loadings (23 wt%) of the Eu-complex than in other matrices, and that co-doping with Tb(dbm)₃phen improves luminescence for samples with Eu(dbm)₃phen content lower than about 10 wt%. Results are interpreted by using a simple sphere of action model adapted to the case of a pore-limited system.     

Electronic structure calculations and molecular dynamics simulations of hydrogen adsorption on Beryllium doped complexes

Interaction of molecular hydrogen with Be and Be₂ decorated acetylene is studied using first principles calculations and molecular dynamics simulations. C₂H₂Be and C₂H₂Be₂ complex can interact with maximum of two and four H₂ molecules respectively thereby showing respective H₂ uptake capacity of 10.3 and 15.5 wt % and is well above the target set by U.S. department of energy. Temperature dependent Gibbs free energy corrected adsorption energy shows that H₂ adsorption on C₂H₂Be is energetically favorable below 250 and 200 K and 1 atm. pressure at MP2/6-311++G** and CCSD(T)/6-311++G** level whereas it is energetically favorable on C₂H₂Be₂ at entire temperature and pressure range considered here from 50 K to 400 K and 50 atm to 400 atm. The desorption temperature obtained for C₂H₂Be(2H₂) and C₂H₂Be₂(4H₂) complexes at MP2/6-311++G** level using van't Hoff equation is 281 and 638 K respectively. Molecular dynamics simulations performed at different temperature show that all the adsorbed H₂ molecules remain adsorbed during the simulations on a complex at temperature T only if Gibbs free energy corrected H₂ adsorption energy at that temperature T is positive. H₂ adsorption on Be decorated ethylene is also studied and the results are compared with Be decorated acetylene.