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The discovery of high-temperature superconductivity in the copper oxides in 1986 triggered a huge amount of innovative scientific inquiry. In the almost three decades since, much has been learned about the novel forms of quantum matter that are exhibited in these strongly correlated electron systems. A qualitative understanding of the nature of the superconducting state itself has been achieved. However, unresolved issues include the astonishing complexity of the phase diagram, the unprecedented prominence of various forms of collective fluctuations, and the simplicity and insensitivity to material details of the 'normal' state at elevated temperatures., The discovery of high-temperature superconductivity in the copper oxide perovskite [La.sub.2-x][Ba.sub.x]Cu[O.sub.4] (ref. 1) ranks among the major scientific events of the twentieth century. The superconducting transition temperatures in the copper [...]

The sensitivity of semiconductor sensors based on tin (Sn[O.sub.2]), tungsten (W[O.sub.3]), and zinc (ZnO) oxides and Sn[O.sub.2] with catalytic admixtures of [La.sub.2][O.sub.3] and CuO to hydrogen sulfide is studied at [H.sub.2]S concentration 50 ppm in dry air in the temperature range 100-600°C. Concentration dependences for oxides are studied in the temperature range 350-450°C and [H.sub.2]S concentration range 0.5-100 ppm at the humidity of gas media 0-80 rel. %. It is shown that, under the specified conditions, the resistance and of sensors to [H.sub.2]S in air weakly depends on humidity. It was found that sensors based on Sn[O.sub.2] with an admixture of 3% [La.sub.2][O.sub.3] working at 350°C are the best for the registration of [H.sub.2]S by the set of performance and operation characteristics. A presumable mechanism of [H.sub.2]S interaction with oxide surfaces is considered, according to which each [H.sub.2]S molecule releases seven electrons to the conductivity zone of the oxide and molecules of metal oxides in the surface layer are, possibly, partially replaced by sulfide molecules. Keywords: gas sensitivity (response) to [H.sub.2]S, metal oxide, sensor, humidity DOI: 10.1134/S1061934814020105, Among toxic and explosive gases hydrogen sulfide occupies a leading position. It accompanies processes of methane recovery from gas wells on nonassociated gas fields (for example, Astrakhan and Orenburg) and [...]

The nature of the pseudogap phase is a central problem in the effort to understand the high-transition-temperature (high-[T.sub.c]) copper oxide superconductors (1). A fundamental question is what symmetries are broken when the pseudogap phase sets in, which occurs when the temperature decreases below a value [T.sup.*]. There is evidence from measurements of both polarized neutron diffraction (2,3) and the polar Kerr effect (4) that time-reversal symmetry is broken, but at temperatures that differ significantly from one another. Broken rotational symmetry was detected from both resistivity measurements (5) and inelastic neutron scattering (6-8) at low doping, and from scanning tunnelling spectroscopy (9,10) at low temperature, but showed no clear relation to [T.sup.*]. Here we report the observation of a large in-plane anisotropy of the Nernst effect in [YBa.sub.2][Cu.sub.3][O.sub.y] that sets in precisely at T* throughout the doping phase diagram. We show that the CuO chains of the orthorhombic lattice are not responsible for this anisotropy, which is therefore an intrinsic property of the Cu[O.sub.2] planes. We conclude that the pseudogap phase is an electronic state that strongly breaks four-fold rotational symmetry. This narrows the range of possible states considerably, pointing to stripe or nematic order (11,12)., We have measured the Nernst coefficient, v(T), of the high-[T.sub.c] superconductor Y[Ba.sub.2][Cu.sub.3][O.sub.y] (YBCO) as a function of temperature up to ~300 K for a hole concentration (13) (doping) ranging from [...]

A thermal-dissolution model for reset transition in unipolar resistive-switching memory (RRAM) based on metal oxides is presented. The model based on Joule heating and dissolution of the conductive filament (CF) could be used to study the reduction of the reset current required for device application.

The thermal cycling properties of critical and return current in [Bi.sub.2][Sr.sub.2]Ca[Cu.sub.2][O.sub.x] (Bi-2212) stacks are examined. The studies have shown that the Bi-2212 stacks fabricated by the self-planarizing process have enough stability for thermal cycling.

Many theoretical models of high-temperature superconductivity focus only on the doping dependence of the Cu[O.sub.2]-plane electronic structure. However, such models are manifestly insufficient to explain the strong variations in superconducting critical temperature, [T.sub.c], among cuprates that have identical hole density but are crystallographically different outside of the Cu[O.sub.2] plane. A key challenge, therefore, has been to identify a predominant out-ofplane influence controlling the superconductivity, with much attention focusing on the distance [d.sub.A] between the apical oxygen and the planar copper atom. Here we report direct determination of how variations in interatomic distances within individual crystalline unit cells affect the superconducting energy-gap maximum of [Bi.sub.2][Sr.sub.2]Ca[Cu.sub.2][O.sub.8+[delta]]. In this material, quasiperiodic variations of unit cell geometry occur in the form of a bulk crystalline 'supermodulation.' Within each supermodulation period, we find [approximately equal to]9 [+ or -] 1% cosinusoidal variation in local A that is anticorrelated with the associated [d.sub.A] variations. Furthermore, we show that phenomenological consistency would exist between these effects and the random [DELTA] variations found near dopant atoms if the primary effect of the interstitial dopant atom is to displace the apical oxygen so as to diminish [d.sub.A] or tilt the Cu[O.sub.5] pyramid. Thus, we reveal a strong, nonrandom out-of-plane effect on cuprate superconductivity at atomic scale. apical oxygen | dopant atoms | out-of-plane influence | superconducting energy gap | supermodulation

Cu2O nanoparticles of diameter in the range 6-8.6 nm are synthesized by a chemical method. The results indicate that the interfacial amorphous phase of the nanoparticle assembly controls the electrical properties of the system.

The analysis of the electronic structure of the isolated silver copper oxide Ag2Cu2O4 is presented along with its precursor Ag2Cu2O4 and similar binary oxides, Ag2O, AgO, CuO, and NaCuO2. The results for AgCu2O4 reveal an electronic distribution in which silver and copper share a delocalized valence scheme with both metals in formal oxidation states larger than the usual Ag(super I) and Cu(super II).

A series of tetragonal zirconia-supported CuO oxide catalysts with various CuO loadings are characterized. The results indicate that the dispersion capacity of copper oxide on this support is approximately 8.6 Cu(super 2+) ions/nm(super 2) ZrO2.

Electronic structure of SrCu2O2 is examined via photoelectron and optical spectroscopy. Local density approximation method is used to compare the results.

The C-Se cross-coupling reaction catalyzed by copper oxide nanoparticles under ligand free conditions in presence of selenourea as an effective selenium surrogate is described. The protocol could also be applied for the synthesis of a variety of symmetrical diaryl selenides in good to excellent yields from the readily available aryl halides/boronic acids.

Several studies are conducted to analyzed the impact of the size and number of the BaZr[O.sub.3] nanorods on the flux pinning properties and microstructure of the Sm[Ba.sub.2][Cu.sub.3][O.sub.y] thin films. The diameter of the BZO nanorods is shown to decrease with a decrease in the substrate temperature.

Multilayered Al/CuO thermite is deposited by a dc reactive magnetron sputtering method and the process is designed to produce low stress multilayered nanoenergetic material, each layer being in the range of tens nanometer to one micron. The reaction temperature and heat of reaction are measured by using differential scanning calorimetry and thermal analysis in order to compare nanostructured layered materials to microstructured materials.

The article discusses a newly developed method, which employs a simple gas-solid reaction for the synthesis of hybrid nanopore-structured nanoporous copper oxide derived from the carbon nanotube/copper composites. The hybrid structure is shown to exhibit extremely high surface area, hence leading to faster and better adsorption rate of the permeating gases.

[Cu.sub.2]O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium t in oxide (ITO) coated glass and the effect of oxygen partial pressure on the structures and properties of [Cu.sub.2]O thin films are examined. The higher conduction band of the [Cu.sub.2]O relative to that of gallium doped ZnO (GZO) in the band alignment has shown that the heterojunctions are suitable for solar cell application based on energy levels consideration.

The impact of the electric field on the growth direction of the different CuO nanoneedles during a thermal oxidation process is analyzed. An increase in the electric field is shown to lead to a significant enhancement of the length of the CuO nanoneedles.

The article employs the different thin film sees to analyze the multiseeded melt growth of bulk Y-Ba-Cu-O compounds. An increase in the grain boundary contact angle is shown to lead to a significant decrease in the extent of residual melt deposited at the grain boundary.

First-principles calculations are used for studying the formation of native point defects in cuprous oxide, [Cu.sub.2]O, prepared from solution. The calculations have shown that both n-type and p-type [Cu.sub.2]O is obtained depending on the solution pH value.

Several studies are conducted to explain the synthesis, as well as the structural and room-temperature ferromagnetic properties of the Fe-doped CuO nanocrystals. The magnetization of these nanocrystals is shown to be completely dependent on the temperature.

A solution-based synthesis of monodisperse [Cu.sub.2]O nanocrystals with controllable sizes in the nanoscale regime is described and two types nanocrystals, cubes and rhombic dodecahedra unifaceted with either {001} or {110} crystal planes, are prepared. A greater depletion layer of carrier and a relatively small contact potential has accounted for the sensing enhancement in the sensors made from the organized [Cu.sub.2]O nanocrystals.

The incidence x-ray scattering approach is employed to explain the various layer, as well as the interface structural changes taking place in the [Co.sub.0.6][Fe.sub.0.2][B.sub.0.2]/Al[O.sub.x] multilayers because of annealing. Annealing is shown to lead to a significant decrease in the thickness of the layer.

Several studies are conducted to explain the temperature and magnetic field dependent neutron powder diffraction taking place in the [Ru.sub.0.9][Sr.sub.2]Y[Cu.sub.2.1O7.9] compounds. The antiferromagnetic order is shown to get destroyed with an increasing magnetic field.

Several studies are conducted to explain the mechanisms associated with the extended dislocation-based pinning mechanism exhibited by the superconducting Y[Ba.sub.2][Cu.sub.3][O.sub.7] films. The boundaries of the films are shown to exhibit extremely low misorientation angles.

CueO from Escherichia coli is a multicopper oxidase (MCO) that has involved in copper tolerance under aerobic conditions, where it has featured four copper atoms that have acted as electron transfer (T1) and dioxygen reduction (T2, T3, trinuclear) sites. The results have shown that CueO is a cuprous oxidase.

Numerous studies are conducted to explain the impact of the particle size on the exchange bias observed in the various Fe-doped CuO nanoparticles sintered at different temperatures. An increase in the grain size is shown to lead to a sharp transition from the paramagnetic to the ferromagnetic of the system.

The [Cu.sub.2]O nanoparticles having average crystallite diameters are prepared by a simple solvothermal method. The effects of the doping concentration and the particle size on the relaxations dynamics of the [Cu.sub.2]O nanoparticles are examined by using photoluminescence decay.

Exchange bias nanocomposites are obtained by the chemical concentration precipitation method, in which the ferrimagnetic M[Fe.sub.2][O.sub.4] (M = Cu,Ni) particles are embedded in the antiferromagnetic (AFM) CuO matrix. The continuous introduction of magnetic Ni ions has shown that the existence of domain state structure and the formation of soft magnetic phase in AFM matrix are responsible for the different behaviors of the exchange bias field and coercivity in the nanoparticles.

The article discusses a newly developed approach, which can be employed for the development of various metal-semiconductor core-shell heterostructures. The methodology is shown to be extremely efficient and effective, as it leads to exact morphological control in the heterostructures.

A study was conducted to examine the growth process of cupric oxide (CuO) nanowires by thermal oxidation. Results revealed that nanowire growth by thermal oxidation is very simple.

A combination of fixed, radio frequency (rf) capacitance measurements, and impedance spectroscopy (IS) are used to characterize the electrical behavior of copper oxide (CuO) ceramics sintered at 920 degree [Celsius]. The results obtained demonstrated an extrinsic effect associated with non-Ohmic electrode contacts which could dominate the rf capacitance spectra of leaky dielectrics/oxide semiconductors over a wide temperature and frequency range; and, manifest a dielectric response more typically associated with relaxor-ferroelectrics.

The formation of terraced hollow [Cu.sub.2]O nanorods upon oxidation of Cu(100) thin films at ~600 degree Celsius is reported. The morphological evolution of newly developed oxide structure is explained by a mechanism based on the relaxation of interfacial epitaxial stress followed by the release of the bulk stress induced by the large volume expansion accompanying the conversion of metal into oxide.

Cupric oxide (CuO) nanoparticles with different morphologies are prepared by thermal annealing of the copper hydroxide at various temperatures. The magnetic measurements have shown the presence of weak ferromagnetic interaction and the blocking behavior in the nanoparticles and the surface spins are responsible for the anomalous magnetic properties of CuO.

An all-oxide solar cell fabricated from vertically oriented zinc oxide nanowires and cuprous oxide nanoparticles is presented. The performance of the solar cell is enhanced with the addition of an intermediate oxide insulating layer between the nanowires and the nanoparticles.

The dielectric behavior in high purity CuO ceramics with two different grain sizes is examined. The resistance of grain boundaries and the dielectric constant of the CuO samples have decreased with increasing dc bias due to the decrease in grain boundaries capacitance, whereas the resistance of grains has remained constant.

[Sb.sup.5+] ions are added in the CuO-added ([Na.sub.0.5][K.sub.0.5])Nb[O.sub.3] (NKN) ceramics and their effect on the microstructure and piezoelectric properties are examined. The high piezoelectric properties are obtained from the CuO-added NK([N.sub.0.97][S.sub.0.03]) ceramics sintered at 960 degree centigrade for 8 hours.

CuO three-dimensional (3D) flowerlike nanostructures are synthesized on copper surface by a simple solution method and the CuO nanostructure is studied. The factors controlling the morphology and size of the CuO nanostructures are explored, which has shown that the reaction time and the concentration of starting regents have played vital roles in the formation of the CuO 3D nanostructures.

A new electrochemical route for the synthesis of a cuprous oxide ([Cu.sub.2]O) microcrystal without using any template or surfactant is described. The reaction is found to yield large amounts of octahedra and monodisperse colloid spheres.

An in-depth analysis, applying interwoven empirical and theoretical techniques, of many structurally defined 1:1 Cu-[O.sub.2] complexes, is done to study the nature of intermediates occupied in aerobic oxidations in synthetic and enzymatic copper-mediated catalysis. The parameters that affect the mode of oxygen coordination (end-on vs side-on) and the electronic structure, which can change between Cu (II)-superoxo and Cu(III)-peroxo extremes, are better understood.

The structural and magnetic properties of highly (111) oriented Mn doped CuO thin films, which are fabricated on thermally oxidized silicon substrate by radio-frequency magnetron sputtering, are investigated. The indirect coupling between Mn ions and Cu ions has helped in stabilizing the ferromagnetism.

The shape evolution process of Cu2O nanocrystals upon slow oxidation of Cu under ambient conditions, yielding novel hexagonal and triangular platelike morphologies is reported. The findings state that the slow oxidation process and use of crystallographic selective surfactants are essential for the appearance of anisotropic metastable shapes.

The structural and electronic properties of Cu in Ce(sub 1-x)Cu(sub x)O2 nano systems prepared by a reverse microemulsion method were characterized with synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy and density functional calculations. The reduction of the Cu in Ce(sub 1-x)Cu(sub x)O2 nanoparticles was rather reversible without the generation of a significant amount of CuO or Cu2O phases during reoxidation.

The screening of large combinatorial oxide libraries for their electric transport characteristics was described. Complete ternary composition spreads of NiO-Mn(sub 2)O(sub 3)-CuO oxide alloys were deposited onto conducting Nb-doped SrTiO(sub 3) substrates using the combinatorial pulsed laser deposition technique and resistance-temperature relations for each composition in the spread were determined using a custom-designed scanning probe.

Melt- processed samples of YBa2Cu3O(Sub 7-delta) (YBCO) doped with Li additions substituting at Cu(2) planes sites are used to study the effects of doping on the superconducting temperature, critical current density, irreversibility field, upper critical field, coherence length, and magnetic relaxation as a function of temperature and magnetic field. The pinning parameters estimated show a considerable enhancement of the critical current density in the optimally doped sample, but only an insignificant change in the effective activation energy, pointing to a weak pinning of pointlike pinning centers, created by Li additions.