ΔThe effect of co-doping on the yttrium local environment and ionic conductivity of yttria-stabilised zirconia

The effect of co-doping yttria-stabilised zirconia with calcia and scandia has been investigated. Changes in the yttrium ion local environment have been monitored using solid-state magic angle sample spinning ⁸⁹Y nuclear magnetic resonance. The effect on the low-temperature (below 320 °C) bulk ionic conductivity has been observed using AC impedance spectroscopy. It was found that the number of oxygen vacancies in the nearest-neighbour sites to yttrium ions decreased on co-doping with scandia, correlating with an increase in conductivity, but increased on co-doping with calcia, correlating with a decrease in conductivity. This behaviour can be explained by proposing the trapping of oxygen vacancies in the nearest-neighbour yttrium ion sites so that they no longer contribute to the conduction mechanism.

The photoelectron spectra of methyl-substituted allenes and of tetramethyl-bisallenyl

The split Δ = 0.6 eV of the first band at 10.5 eV in the photoelectron spectrum of allene (1) has been ascribed to a Jahn—Teller distortion by Baker and Turner. The influence of alkyl substitution on Δ and on the band position has been investigated by recording the photoelectron spectra of all methyl-substituted allenes 2 to 6, of 1,1-di-tert. butyl-allene (7) and of 1,2-cyclononadiene (8). It is shown that the dependence of Δ on substitution can be rationalized by assuming that it is due to a (pseudo) Jahn—Teller effect in 1 and in the symmetrically substituted derivatives and to the combined influence of this effect and a differential, inductive destabilization in the other cases.The photoelectron spectrum of tetramethyl-bisallenyl 9 can be explained on the basis of known parameters for semi-localized π-orbitals and for their through-space and through-bond coupling.     

The photoelectron spectra of methyl-substituted allenes and of tetramethyl-bisallenyl

The split Δ = 0.6 eV of the first band at 10.5 eV in the photoelectron spectrum of allene (1) has been ascribed to a Jahn—Teller distortion by Baker and Turner. The influence of alkyl substitution on Δ and on the band position has been investigated by recording the photoelectron spectra of all methyl-substituted allenes 2 to 6, of 1,1-di-tert. butyl-allene (7) and of 1,2-cyclononadiene (8). It is shown that the dependence of Δ on substitution can be rationalized by assuming that it is due to a (pseudo) Jahn—Teller effect in 1 and in the symmetrically substituted derivatives and to the combined influence of this effect and a differential, inductive destabilization in the other cases.The photoelectron spectrum of tetramethyl-bisallenyl 9 can be explained on the basis of known parameters for semi-localized π-orbitals and for their through-space and through-bond coupling.     

First principle simulations of the surface diffusion of Si and Me adatoms on the Si(111)3×3-Me surface,Me= Al,Ga, In,Pb

The intriguing but yet still unexplained experimental results of Hibino and Ogino [Phys. Rev. B 54, 5763 (1996); Surf. Sci. 328, L547 (1995)], who have observed single defect movement on an Me induced Si(111)$\sqrt{3}\times \sqrt{3}$ surface, have been revived and theoretically analysed. Using Nudged Elastic Band (NEB) optimization, the minimal energy path for an Si adatom moving on the ideal and vacancy defected surfaces has been obtained and the most probable mechanism of the vacancy mediated single defect diffusion has been established. This mechanism is shown to be responsible for the experimentally observed Si adatom movement and predicts a far easier movement of the Me adatom on vacancy defected Me induced Si(111)$\sqrt{3}\times \sqrt{3}$ surfaces.     

p-Type and n-type quaterthiophene based semiconductors for thin film transistors operating in air?

The solution and solid-state properties as well as the organic thin film transistor (OTFT) behavior of α,ω-perfluorohexyl-quaterthiophene (DFH-4T) are presented and compared to those of quaterthiophene (4T) and α,ω-hexyl-quaterthiophene (DH-4T). UV/visible and fluorescence data showed the same weak effect of hexyl and perfluorohexyl substitutions on the optical properties of 4T core. Growth mechanism of DFH-4T based thin films deposited by vacuum deposition on heated Si/SiO₂ substrates has been investigated in details and demonstrated to be identical to that of DH-4T. The characterization in air of the charge transport properties of thin films based on DH-4T and DFH-4T revealed a switch from p- to n-type, respectively, depending on the nature of alkyl chains. A qualitative Schottky-type charge injection barrier model, based on HOMO and LUMO energy levels estimated from cyclic voltammograms and optical absorption spectra of DFH-4T relative to those of 4T and DH-4T, was introduced to explain such change in semiconducting properties observed under ambient conditions (temperature, light, air). In an attempt to answer to the question of “are p-type and n-type quaterthiophene derivatives appropriate semiconductors for thin film transistors operating in air?” we investigated the influence of the nature of the dielectrics to obtain OTFTs operating in air and showing environmentally stable mobility.     

A novel fluorometric determination of melamine using cucurbit[7]uril

Melamine is a toxic compound to both animals and human beings, and is connected to various diseases, such as kidney stones and bladder cancer. For the efficient detection of melamine, we have developed a novel sensitive cucurbit[7]uril (CB7) sensor with a detection limit at 0.20 μg mL⁻¹, and applied it to detect melamine in tainted milk. Fluorescence studies indicate that CB7 forms complex with melamine in a 1:1 mole ratio. The binding constant at various temperatures has been calculated and the interaction mechanism has been discussed based on molecular modeling result.     

Complexing equilibria of Ag(I) ion in the presence of heterocyclic amines in DMSO. Comparison with other solvents

The stability constants of Ag(I) complexes with aromatic heterocyclic amines: pyridine (py), 2,2′-bipyridine (bipy), 1,10-phenantroline (phen), 2,2′-bipyridil-6′-phenyl (bpp) and 2,2′:6′,2″-terpyridine (tp) as well as with saturated cyclic amines: piperidine (ppd), piperazine (ppz), 1,4-diazacycloheptane (dach), 1,4,7-triazacyclononane (tacn) and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (tmtact) have been determined in DMSO using potentiometry. The polarizability and dipole moments of the investigated amines have been calculated by means of AM1 and PM3 methods (from the MOPAC 6 packet). The role of the Ag(I) ion and ligand solvation in thermodynamics of the complex formation process in four solvents (H₂O, AN, PC, DMSO) has been discussed.     

Study of surface morphology of ferrofluid deposited etched ion tracks in dielectric layers

An AFM study is reported on swift heavy irradiated Si/SiO₂ substrates which have been etched by aqueous hydrofluoric acid solution leading to ion tracks in which ferrofluids have been deposited leading to tunable electronic materials with pores in oxide on silicon (TEMPOS) structure. Two ferrofluids with different carrier fluids (aqueous and non-aqueous) have been deposited in the tracks. Atomic force microscopy has been used to study the empty as well as filled tracks. Since the ferrofluids contain iron oxide particles, there is a possibility of agglomeration of these particles inside and outside the tracks. Surface area and pore volume of the tracks have been measured by Brunauer-Emmett-Teller (BET) method. The track properties (empty and filled) as observed by AFM have been correlated with BET measurements.     

Commensurate ordering of iron phthalocyanine on Ag(1 1 1) surface

Epitaxial growth of iron phthalocyanine on a silver (1 1 1) surface has been studied with scanning tunneling microscopy in ultrahigh vacuum. While several structures were observed, this report concentrates on what appeared to be the most stable phase. This phase has commensurate two-dimensional ordering with oblique unit vectors (b₁, b₂) where b₁ = 5a₁ + 2a₂ and b₂ = 5a₂, where a₁ and a₂ are unit vectors of Ag(1 1 1) surface. The rotation angle of iron phthalocyanine relative to the silver [1 0 ] direction was determined to be 16.63° from the high-resolution image analysis. The oblique structure is more commensurate than that of iron phthalocyanine on graphite and of copper phthalocyanine on the Ag(1 1 1) surface. The observed FePc on Ag(1 1 1) structure is similar to that of FePc on Au(1 1 1), but has significantly higher surface density. Bias dependence of the images was observed and is consistent with the expected small HOMO–LUMO gap.     

Application of ultrasound to the synthesis of a new nanostructured Mn(II) supramolecular compound: A precursor for γ-Mn2O3 nanoparticles

A new nanostructured Mn(II) supramolecular compound [Mn(hpydcH₂)₂(H₂O)₄] (1) (hpydcH₃ = 4-hydroxy-2,6-pyridinedicarboxylic acid) has been synthesized using a sonochemical process. The structure of compound 1 was determined by single crystal X-ray diffraction and it was revealed that each hpydcH₂⁻ anionic ligand has been coordinated to Mn(II) ion in a novel monodentate fashion leaving another functional carboxylic acid group intact. Compound 1 was also characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analysis. Thermal stability of compound 1 was studied by thermal gravimetric (TG) analysis and compared to that of its crystalline analogue. Subsequently, the role of concentration of the initial reactants on the size of nanostructures of compound 1, has been investigated. Compound 1 was proved to be a precursor for γ-Mn₂O₃ nanoparticles.     

Photoelektronenspektren und konformationsverhalten von hydroxylamin und methylhydroxylaminen

Gas-phase He(I) photoelectron spectra of hydroxylamine (1) and the methyl hydroxylamines (2–6) have been measured. From 1 a He(II) spectrum has also been obtained. To study the interactions of the n(N) and n(O) orbitals, MINDO/2 calculations have been performed for various conformations of 1–6. The findings are consistent with trans- forms being the most stable conformations of 1–6, but additional cis- conformers cannot be excluded.     

Specific features of the thermal electromotive force in Bi quantum wires in transverse magnetic and electric fields

The thermal electromotive force (emf) in Bi quantum wires has been calculated in the model of potential in the form of a paraboloid of revolution in a uniform magnetic field H, which is normal to the axis of the studied nanostructure, and in a direct-current (dc) electric field E ‖ H. It has been shown that, with an increase in E, the thermal emf α _xx is described by a nonmonotonic function at different values of H. A physical interpretation of this behavior of α _xx as a function of E is proposed with account for the interaction between carriers and the rough surface of the nanowire.     

The photoelectron spectra of cyclooctatetraene and its hydrogenated derivatives

The photoelectron spectrum of cyclooctatetraene (COT; 1) has been re-examined. Correlation with the spectra of the dihydro- (2, 3), tetrahydro- (4, 5, 6), hexahydro- (7) and octahydro- (8) derivatives confirms the orbital sequence originally proposed by Eland, namely 5a₁ (π), 7e (π), 4b₂ (π), σ. It is shown that the positions and the relative spacing of the π-orbitals are the result of a competition between through-space and through-bond interactions.The photoelectron spectroscopic results for the hydrogenated derivatives of COT yield information about their conformation; in particular about the twist angles between consecutive π-bonds. The spectrum of 1,5-cyclooctadiene (6) confirms that this molecule preferentially adopts the boat conformation.An empirical rule is proposed which yields estimates for the orbital energies of basis π-orbitals in monocyclic hydrocarbons.     

North-South asymmetry of some solar parameters: A study based on the dominance of hemispheric sunspot activity during the solar cycles 18–24

Solar activity indices differ over the solar disk, and different activity parameters are not considered to be symmetric between the northern and southern solar hemispheres. In the present paper, the daily data of a set of solar parameters (solar radio flux F10.7, total solar irradiance TSI, plage area PA, coronal index CI, solar flare index SFI, and solar mean magnetic field ǀBǀ) as well as the daily hemispheric sunspot areas (SSAs) and sunspot numbers (SSNs) during a timeframe 1945–2017 (covering almost the last seven solar cycles, 18 ̶ 24) have been employed to investigate the north-south (N-S) asymmetry of the considered solar parameters based on the dominance of hemispheric distributions of SSAs and SSNs. The N-S asymmetry for each solar parameter has been investigated and the results revealed that it is a significant aspect through different years in the entire period. The grand average of each solar parameter for the northern and southern groups over each solar activity cycle has been calculated to investigate the statistical significance of N-S asymmetry of each solar parameter in each solar activity cycle. The solar cycles 19 and 24 displayed the dominance of the southern F10.7 and PA over the northern one. However, the solar cycle 23 showed the reverse. The grand average of CI displayed the southern preference in the solar cycle 19 while, the northern dominance of CI is revealed for the solar cycle 23. The grand averages of CI demonstrated nearly symmetric distribution in solar cycles 18, and 20–22. The N-S asymmetry of the grand averages of SFI exhibited a southern dominance during solar cycles 21 and 24. On the other hand, the northern preference is observed for the grand average of SFI through the solar cycle 23. The asymmetry of the grand averages of ǀBǀ obviously has the same dominance (sign) of hemispheric sunspot activity indices for the solar cycles 21–24. The periodic behavior of the N-S asymmetry of SSAs, SSNs, F10.7, and ǀBǀ has been investigated using Fast Fourier Transformation. Many mid- and long term periodicities have been detected. We present our results and discuss their possible explanations.     

Ultrasound-assisted synthesis of water-soluble monosubstituted diruthenium compounds

The elusive monosubstituted diruthenium complexes [Ru₂Cl(DAniF)(O₂CMe)₃] (1), [Ru₂Cl(DPhF)(O₂CMe)₃] (2), [Ru₂Cl(D-p-CNPhF)(O₂CMe)₃] (3), [Ru₂Cl(D-o-TolF)(O₂CMe)₃] (4), [Ru₂Cl(D-m-TolF)(O₂CMe)₃] (5), [Ru₂Cl(D-p-TolF)(O₂CMe)₃] (6) and [Ru₂Cl(p-TolA)(O₂CMe)₃] (7) have been synthesized using for the first time ultrasound-assisted synthesis to carry out a substitution reaction in metal–metal bonded dinuclear compounds (DAniF⁻ = N,N′-bis(4-anisyl)formamidinate; DPhF⁻ = N,N′-diphenylformamidinate; D-p-CNPhF⁻ = N,N′-bis(4-cyanophenyl)formamidinate; D-o/m/p-TolF⁻ = N,N′-bis(2/3/4-tolyl)formamidinate; p-TolA⁻ = N-4-tolylamidate). This is a simpler and greener method than the tedious procedures described in the literature, and it has permitted to obtain water-soluble complexes with good yields in a short period of time. A synthetic study has been implemented to find the best experimental conditions to prepare compounds 1–7. Two different types of ligands, formamidinate and amidate, have been used to check the generality of the method for the preparation of monosubstituted complexes. Five new compounds (2–6) have been obtained using a formamidinate ligand, the synthesis of the previously described compound 1 has been improved, and an unprecedented monoamidate complex has been achieved (7). The crystal structures of compounds 3 and 7 have been solved by single crystal X-ray diffraction. These compounds show the typical paddlewheel structure with three acetate ligands and one formamidinate (3) or amidate (7) bridging ligand at the equatorial positions. The axial positions are occupied by the chloride ligand giving rise to one-dimensional polymer structures that were previously unknown for monosubstituted compounds.     

Optical absorption band edge in single-crystal GeS

The absorption band edge of single-crystal orthorhombic GeS has been measured in all three polarizations at 4.2, 77 and 300°K. Strong excitonic absorption is observed for E ∥ a, and the transitions in this direction are identified as direct-allowed. Transitions in the E ∥ b and E ∥ c polarizations are tentatively identified as direct forbidden and direct allowed, respectively, with values for E_g similar to those found for E ∥ a. Evidence for the partially two-dimen?ional character of GeS is discussed.     

New results on the Zeeman effect of phosphorus in silicon

We report variational calculations of the quadratic Zeeman effect of phosphorus impurity in silicon, which are compared to our experimental data for B⊥E and B⊥E. It is shown that a small variation of the ratio γ of the transverse and effective masses can lead to a good agreement between theory and experiment for the 2p₀ line. The shift of the central component of the 2p_± line has been found to depend on the polarization of the incident radiation and this fact has not yet been explained. It is also shown that the shift observed for the line ascribed previously to a 1s(A₁)→3d₀ transition can be consistent with this attribution, giving experimental evidence of its electronic nature.     

Unsymmetrically Substituted Nickel Triazatetra-Benzcorrole and Phthalocynanine Complexes: Conjugation to Quantum Dots and Applications as Fluorescent “Turn ON” Sensors

We report on the design and application of fluorescent nanoprobes based on the covalent linking of _L-glutathione-capped CdSe@ZnS quantum dots (QDs) to newly synthesized unsymmetrically substituted nickel mercaptosuccinic acid triazatetra-benzcorrole (3) and phthalocyanine (4) complexes. Fluorescence quenching of the QDs occurred on conjugation to complexes 3 or 4. The nanoprobes were selectively screened in the presence of different cations and Hg²⁺ showed excellent affinity in “turning ON” the fluorescence of the nanoprobes. Experimental results showed that the sensitivity of QDs-4 towards Hg²⁺ was much higher than that of QDs-3 nanoprobe. The mechanism of reaction has been elucidated based on the ability of Hg²⁺ to coordinate with the sulphur atom of the Ni complex ring and apparently “turn ON” the fluorescence of the linked QDs.     

Electronic and high pressure elastic properties of RECd and REHg (RE=Sc,La and Yb) intermetallic compounds

Structural, electronic, elastic and mechanical properties of Cd and Hg based rare earth intermetallics (RECd and REHg; RE=Sc, La and Yb) have been investigated using the full-potential linearized augmented plane-wave (FP-LAPW) method within the density-functional theory (DFT). The ground state properties such as lattice constant (a₀), bulk modulus (B) and its pressure derivative (B′) have been obtained using optimization method and are found in good agreement with the available experimental results. The calculated enthalpy of formation shows that LaHg has the strongest alloying ability and structural stability. The electronic band structures and density of states reveal the metallic character of these compounds. The structural stability mechanism is also explained through the electronic structures of these compounds. The chemical bonding between rare earth atoms and Cd, Hg is interpreted by the charge density plots along (1 1 0) direction. The elastic constants are predicted from which all the related mechanical properties like Poisson’s ratio (σ), Young’s modulus (E), shear modulus (G_H) and anisotropy factor (A) are calculated. The ductility/brittleness of these intermetallics is predicted. Chen’s method has been used to predict the Vicker’s hardness of RECd and REHg compounds. The pressure variation of the elastic constants is also reported in their B₂ phase.     

Three-dimensional organometallic thallium(I) supramolecular polymer nanostructures synthesized with sonochemical process

A new three-dimensional thallium(I) supramolecular polymer, [Tl₂(μ₂-ATA)]_n (1), [H₂ATA = 2-aminoterephthalic acid]_, has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows one type of Tl^I ion with a low coordination number. Compound 1 was self-assembled from Tl⋯C, Tl⋯O and Tl⋯N secondary interactions in thallium(I) coordination and the active lone pair on Tl^I in this compound may be involved in donor bonding. Two sides of the aromatic ring of ATA²⁻ anion have been involved in two types of secondary Tl⋯C approaches. Three samples of 1 were synthesized with three different concentrations of initial reagents under ultrasonic irradiation. The thermal stability of compound 1 samples were studied by thermo gravimetric (TG) and differential thermal analyses (DTA). These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).