Efficient overall water splitting under visible-light irradiation on (Ga(1-x)Zn(x))(N(1-x)O(x)) dispersed with Rh-Cr mixed-oxide nanoparticles: Effect of reaction conditions on photocatalytic activity

The photocatalytic activity of (Ga(1-x)Zn(x))(N(1-x)O(x)) loaded with Rh-Cr mixed-oxide (Rh(2-y)Cr(y)O3) nanoparticles for overall water splitting under visible-light irradiation (lambda > 400 nm) is investigated with respect to reaction pH and gas pressure. The photocatalytic performance of the catalyst is found to be strongly dependent on the pH of the reactant solution but largely independent of gas pressure. The present photocatalyst exhibits stable and high photocatalytic activity in an aqueous solution of pH 4.5 for 72 h. The photocatalytic performance is much lower at pH 3.0 and pH 6.2, attributable to corrosion of the cocatalyst and hydrolysis of the catalyst. The dispersion of Rh(2-y)Cr(y)O3 as a cocatalyst on the (Ga(1-x)Zn(x))(N(1-x)O(x)) surface promotes hydrogen evolution, which is considered to be the rate-determining step for overall water splitting on this catalyst.     

Characterization of Rh-Cr mixed-oxide nanoparticles dispersed on (Ga(1-x)Zn(x))(N(1-x)Ox) as a cocatalyst for visible-light-driven overall water splitting

The structure of Rh-Cr mixed-oxide (Rh(2)(-)(y)Cr(y)O(3)) nanoparticles dispersed on (Ga(1)(-)(x)Zn(x))(N(1)(-)(x)O(x)) is characterized by electron microscopy and X-ray spectroscopy. The Rh(2)(-)(y)Cr(y)O(3) nanoparticle is an efficient cocatalyst for photocatalytic overall water splitting on the (Ga(1)(-)(x)Zn(x))(N(1)(-)(x)O(x)) solid solution and is loaded onto the catalyst by impregnation from an aqueous solution containing Na(3)RhCl(6).2H(2)O and Cr(NO(3))(3).9H(2)O followed by calcination in air. Impregnation of the (Ga(1)(-)(x)Zn(x))(N(1)(-)(x)O(x)) with 1 wt % Rh and 1.5 wt % Cr followed by calcination at 623 K for 1 h provides the highest photocatalytic activity. Structural analyses reveal that the activity of this photocatalyst is strongly dependent on the generation of trivalent Rh-Cr mixed-oxide nanoparticles with optimal composition and distribution.     

Soft X-ray characterization of Zn(1-x)Sn(x)O(y) electronic structure for thin film photovoltaics

Zinc tin oxide (Zn(1-x)Sn(x)O(y)) has been proposed as an alternative buffer layer material to the toxic, and light narrow-bandgap CdS layer in CuIn(1-x),Ga(x)Se(2) thin film solar cell modules. In this present study, synchrotron-based soft X-ray absorption and emission spectroscopies have been employed to probe the densities of states of intrinsic ZnO, Zn(1-x)Sn(x)O(y) and SnO(x) thin films grown by atomic layer deposition. A distinct variation in the bandgap is observed with increasing Sn concentration, which has been confirmed independently by combined ellipsometry-reflectometry measurements. These data correlate directly to the open circuit potentials of corresponding solar cells, indicating that the buffer layer composition is associated with a modification of the band discontinuity at the CIGS interface. Resonantly excited emission spectra, which express the admixture of unoccupied O 2p with Zn 3d, 4s, and 4p states, reveal a strong suppression in the hybridization between the O 2p conduction band and the Zn 3d valence band with increasing Sn concentration.     

Design of energy band alignment at the Zn(1-x)Mg(x)O/Cu(In,Ga)Se2 interface for Cd-free Cu(In,Ga)Se2 solar cells

The electronic band structure at the Zn(1-x)Mg(x)O/Cu(In(0.7)Ga(0.3))Se(2) interface was investigated for its potential application in Cd-free Cu(In,Ga)Se(2) thin film solar cells. Zn(1-x)Mg(x)O thin films with various Mg contents were grown by atomic layer deposition on Cu(In(0.7)Ga(0.3))Se(2) absorbers, which were deposited by the co-evaporation of Cu, In, Ga, and Se elemental sources. The electron emissions from the valence band and core levels were measured by a depth profile technique using X-ray and ultraviolet photoelectron spectroscopy. The valence band maximum positions are around 3.17 eV for both Zn(0.9)Mg(0.1)O and Zn(0.8)Mg(0.2)O films, while the valence band maximum value for CIGS is 0.48 eV. As a result, the valence band offset value between the bulk Zn(1-x)Mg(x)O (x = 0.1 and x = 0.2) region and the bulk CIGS region was 2.69 eV. The valence band offset value at the Zn(1-x)Mg(x)O/CIGS interface was found to be 2.55 eV after considering a small band bending in the interface region. The bandgap energy of Zn(1-x)Mg(x)O films increased from 3.25 to 3.76 eV as the Mg content increased from 0% to 25%. The combination of the valence band offset values and the bandgap energy of Zn(1-x)Mg(x)O films results in the flat (0 eV) and cliff (-0.23 eV) conduction band alignments at the Zn(0.8)Mg(0.2)O/Cu(In(0.7)Ga(0.3))Se(2) and Zn(0.9)Mg(0.1)O/Cu(In(0.7)Ga(0.3))Se(2) interfaces, respectively. The experimental results suggest that the bandgap energy of Zn(1-x)Mg(x)O films is the main factor that determines the conduction band offset at the Zn(1-x)Mg(x)O/Cu(In(0.7)Ga(0.3))Se(2) interface. Based on these results, we conclude that a Zn(1-x)Mg(x)O film with a relatively high bandgap energy is necessary to create a suitable conduction band offset at the Zn(1-x)Mg(x)O/CIGS interface to obtain a robust heterojunction. Also, ALD Zn(1-x)Mg(x)O films can be considered as a promising alternative buffer material to replace the toxic CdS for environmental safety.     

Effects of thermal annealing on the structural and optical properties of Mg(x)Zn(1-x)O nanocrystals

Mg(x)Zn(1-x)O ternary alloy nanocrystals with hexagonal wurtzite structures were fabricated by using the sol-gel method. X-ray diffraction patterns, UV-vis absorption spectra, and photoluminescence spectra were used to characterize the structural and optical properties of the nanocrystals. For as-prepared nanocrystals, the band gap increases with increasing Mg content. Weak excitonic emission with strong deep-level emission related to oxygen vacancy and interface defects is observed in the photoluminescence spectra at room temperature. Thermal annealing in oxygen was used to decrease the number of defects and to improve the quality of the nanocrystals. In terms of XRD results, the grain sizes of nanocrystals increase with increasing annealing temperature and the lattice constants of alloy are smaller than those of pure ZnO. The band gap becomes narrower with increasing annealing temperature. For Mg(x)Zn(1-x)O nanocrystals (x=0.03-0.15) annealed at temperatures ranging from 500 to 1000 degrees C, intense near-band-edge (NBE) emissions and weak deep-level (DL) emissions are observed. Consequently, the quality of Mg(x)Zn(1-x)O nanocrystals can be improved by thermal annealing.     

Correlation between the band positions of (SrTiO3)1-x.(LaTiO2N)x solid solutions and photocatalytic properties under visible light irradiation

N-doped SrTiO3 and (SrTiO3)1-x.(LaTiO2N)x samples were prepared by the thermal ammonolysis method. The photocatalytic activities of the samples were investigated in a water suspension system. Aqueous methanol solution (50 mL CH3OH + 220 mL H2O) for H2 evolution and aqueous silver nitrate solution (270 mL, 0.01 mol L(-1)) for O2 evolution were used as sacrificial reagents. The oxynitrides showed photocatalytic activities under visible light irradiation. The maximum rates of photocatalytic hydrogen and oxygen evolution under visible light irradiation (lambda > 420 nm) were 10 and 8 micromol h(-1), respectively. The samples were characterized by X-ray diffractometry, UV-Vis spectrophotometry, Fourier transform infrared spectrometry, and laser Raman spectroscopy. The unit cell edge length of (SrTiO3)1-x.(LaTiO2N)x increased linearly and their band gaps reduced from 3.18 to 2.04 eV with increasing x from 0 to 0.30. Moreover, the calculation results of (SrTiO3)0.75.(LaTiO2N)0.25 by density functional theory suggested that the band gap narrowing of the solid solutions came from the hybridization of N2p and O2p orbital. The band positions of the solid solutions were further investigated by Mott-Schottky and the onset potential method. The results suggested that the conduction band of the solid solution was lowered, which led to decrement of the hydrogen evolution rate.     

Tunable electrical and magnetic properties of half-metallic Zn(x)Fe(3-x)O4 from first principles

The electrical and magnetic properties of Zn-doped Fe(3)O(4) at different doping concentrations of Zn have been investigated using a density functional method with generalized-gradient approximation corrected for on-site Coulombic interactions. The electronic structure calculation predicts that Zn(x)Fe(3-x)O(4) (0 ≤x≤ 0.875) is half-metallic with a full spin polarization. The hopping carrier concentration of Zn(x)Fe(3-x)O(4) decreases with increasing x, which indicates a distinct increase in the resistivity. The saturation magnetization of Zn(x)Fe(3-x)O(4) increases evidently with increasing x from x = 0 to x = 0.75 (i.e. from 4.0 to 8.3 μ(B)/f.u.) and then decreases rapidly to zero at x = 1. The robust half-metallicity, large tunability of electrical and magnetic properties of a Zn doped Fe(3)O(4) system make it a promising functional material for spintronic applications.     

Alloyed (ZnSe)(x)(CuInSe2)(1-x) and CuInSe(x)S(2-x) nanocrystals with a monophase zinc blende structure over the entire composition range

Metastable zinc blende CuInSe(2) nanocrystals were synthesized by a hot-injection approach. It was found that the lattice mismatches between zinc blende CuInSe(2) and ZnSe as well as CuInSe(2) and CuInS(2) are only 2.0% and 4.6%, respectively. Thus, alloyed (ZnSe)(x)(CuInSe(2))(1-x) and CuInSe(x)S(2-x) nanocrystals with a zinc blende structure have been successfully synthesized over the entire composition range, and the band gaps of alloys can be tuned in the range from 2.82 to 0.96 eV and 1.43 to 0.98 eV, respectively. These alloyed (ZnSe)(x)(CuInSe(2))(1-x) and CuInSe(x)S(2-x) nanocrystals with a broad tunable band gap have a high potential for photovoltaic and photocatalytic applications.     

Structural and thermochemical chemisorption of CO2 on Li(4+x)(Si(1-x)Al(x))O4 and Li(4-x)(Si(1-x)V(x))O4 solid solutions

Different Li(4)SiO(4) solid solutions containing aluminum (Li(4+x)(Si(1-x)Al(x))O(4)) or vanadium (Li(4-x)(Si(1-x)V(x))O(4)) were prepared by solid state reactions. Samples were characterized by X-ray diffraction and solid state nuclear magnetic resonance. Then, samples were tested as CO(2) captors. Characterization results show that both, aluminum and vanadium ions, occupy silicon sites into the Li(4)SiO(4) lattice. Thus, the dissolution of aluminum is compensated by Li(1+) interstitials, while the dissolution of vanadium leads to lithium vacancies formation. Finally, the CO(2) capture evaluation shows that the aluminum presence into the Li(4)SiO(4) structure highly improves the CO(2) chemisorption, and on the contrary, vanadium addition inhibits it. The differences observed between the CO(2) chemisorption processes are mainly correlated to the different lithium secondary phases produced in each case and their corresponding diffusion properties.     

Vibrational modes and structural characteristics of (Ba(0.3)Sr(0.7))[(Zn(x)Mg(1-x))(1/3)Nb(2/3)]O3 solid solutions

(Ba(0.3)Sr(0.7))[(Zn(x)Mg(1-x))(1/3)Nb(2/3)]O(3) (BSZMN) (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solution ceramics were synthesized by the conventional solid-state sintering technique. Vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection spectroscopy, short for FTIR) and X-ray diffraction (XRD) were employed to evaluate the correlation between crystal structures and vibration modes of these solid solutions as a function of Mg(2+) ions replaced by Zn(2+) ions. It is verified that these ceramics present a phase transition, i.e., the crystal structure changes from hexagonal phase (P ?3m1, where x≤ 0.4) to the pseudocubic phase (I4/mcm, where x≥ 0.8) with increasing Zn(2+) content. The phase transition is a gradual process, the sample where x = 0.6 is of the transition phase, i.e., at x = 0.6, phase transition begins to appear from hexagonal phase to pseudocubic phase but is not complete. The phase transition is also verified by the FTIR spectra. Tilting of oxygen octahedra is the main reason for the phase transition. The phonon modes of the vibration spectra were assigned, the position and width were determined, and the correlation of phonon vibrations with the microstructure for the different atoms substituted in B'-site was found.     

Characterization of ruthenium oxide nanocluster as a cocatalyst with (Ga(1-x)Zn(x))(N(1-x)Ox) for photocatalytic overall water splitting

The formation and structural characteristics of Ru species applied as a cocatalyst on (Ga(1)(-)(x)()Zn(x)())(N(1)(-)(x)()O(x)()) are examined by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. RuO(2) is an effective cocatalyst that enhances the activity of (Ga(1)(-)(x)()Zn(x)())(N(1)(-)(x)()O(x)()) for overall water splitting under visible-light irradiation. The highest photocatalytic activity is obtained for a sample loaded with 5.0 wt % RuO(2) from an Ru(3)(CO)(12) precursor followed by calcination at 623 K. Calcination is shown to cause the decomposition of initial Ru(3)(CO)(12) on the (Ga(1)(-)(x)()Zn(x)())(N(1)(-)(x)()O(x)()) surface (373 K) to form Ru(IV) species (423 K). Amorphous RuO(2) nanoclusters are then formed by an agglomeration of finer particles (523 K), and the nanoclusters finally crystallize (623 K) to provide the highest catalytic activity. The enhancement of catalytic activity by Ru loading from Ru(3)(CO)(12) is thus shown to be dependent on the formation of crystalline RuO(2) nanoparticles with optimal size and coverage.     

Ce-doped ZnO (Ce(x)Zn(1-x)O) becomes an efficient visible-light-sensitive photocatalyst by co-catalyst (Cu2+) grafting

We have fabricated an efficient visible-light-sensitive Cu(2+)-grafted Ce-doped ZnO photocatalyst (Cu(2+)-Ce(x)Zn(1-x)O) by adopting a metal ion doping and co-catalyst modification. Impurity states were formed below the conduction band (CB) edge in Ce(x)Zn(1-x)O, and these impurity states induce the visible-light absorption. Ce(x)Zn(1-x)O without a Cu(2+)-co-catalyst showed negligible visible-light activity due to the low reduction power of electrons in impurity levels. Surprisingly, Cu(2+)-modification over Ce(x)Zn(1-x)O drastically increased its visible-light activity. Excited electrons in impurity states can transfer to the Cu(2+)-ions on the surface and form Cu(2+)/Cu(+) redox couples, which cause the efficient oxygen reduction through a multi-electron reduction process. One of the striking features of the present study is that the metal doped semiconductors which were inactive due to their impurity states become efficient visible-light photocatalysts upon co-catalyst modification. The successful strategy used here for designing a highly active visible-light photocatalyst would provide numerous opportunities to develop an efficient metal-ion based visible-light photocatalyst.     

Correlation of crystal structure, dielectric properties and lattice vibration spectra of (Ba(1-x)Sr(x))(Zn(1/3)Nb(2/3))O3 solid solutions

(Ba(1-x)Sr(x))(Zn(1/3)Nb(2/3))O(3) (BSZN) (x = 0.0, 0.50, 0.60, 0.65, 0.70, 1.0) solid solutions were synthesized by a conventional solid-state sintering technique. Vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection spectroscopy, FTIR) and X-ray diffraction (XRD) were employed to evaluate the crystal structures and phonon modes of these solid solutions. Dielectric constants (ε(r)) and temperature coefficient of capacitances (τ(c)) were examined to reveal the correlation of the dielectric properties and the crystal structures. The results show that with the increase in Sr(2+) content, the lattice structures of ceramics turn gradually from disordered cubic structure to ordered structure because antiphase tilting of the oxygen octahedra occurs where x≥ 0.65, which is the main reason for the phase transitions and variation of crystal structure. The appearance of the phase transitions is associated with variation of the symmetry structure, from cubic (Pm ?3m, where x = 0) to pseudocubic (I4/mcm, where 0.65 ≤x < 1.0) and then to hexagonal (P ?3ml, where x = 1.0). New phonon modes appear at around 250 cm(-1) in Raman spectra where x≥ 0.65, and there is also a different phonon mode appearing at 156 cm(-1) in the FTIR spectra at the same x range. The appearance of the new phonon modes is the characteristic of ceramics whose oxygen octahedra have tilted with Sr(2+) concentration where x≥ 0.65. The Raman shifts are related to the rigidity of the oxygen octahedra, while the widths of peaks are correlated with τ(c). The FTIR spectra were subjected to the Kramers-Kronig analysis, and the imaginary part of the dielectric constant was analyzed in detail.     

Influence of disorder-to-order transition on lattice thermal expansion and oxide ion conductivity in (Ca(x)Gd(1-x))(2)(Zr(1-x)M(x))2O7 pyrochlore solid solutions

The effect of simultaneous substitutions of Ca at A site and Nb or Ta at B site in pyrochlore-type solid solutions: (Ca(x)Gd(1-x))(2)(Zr(1-x)M(x))(2)O(7) (x = 0.1, 0.2, 0.3, 0.4, 0.5 and M = Nb or Ta) were studied by powder X-ray diffraction (XRD), FT NIR Raman spectroscopic techniques and transmission electron microscopy. The solid solutions were prepared by the conventional high-temperature ceramic route. The XRD results and Rietveld analysis revealed that the defect fluorite structure of Gd(2)Zr(2)O(7) progressively changed to a more ordered pyrochlore phase by simultaneous substitutions at A and B sites. Raman spectroscopy reveals the progressive ordering in the anion sublattice with simultaneous doping. High-resolution images and selected-area electron diffraction patterns obtained from TEM confirms the XRD and Raman spectroscopic results. High-temperature XRD studies show that the lattice expansion coefficient in these pyrochlore oxides is of the order of 10(-6) K(-1). Lattice thermal expansion coefficient increases with increase of disorder in pyrochlore oxides, and hence the variation of thermal expansion coefficient with composition is also a good indicator of disordering in pyrochlore-type oxides. The ionic conducting properties of the samples were characterised by impedance spectroscopy, and it was found that Nb-doped compositions show a considerable change in conductivity near the phase boundary of disordered pyrochlore and defect fluorite phases.     

Phase evolution, phase transition, raman spectra, infrared spectra, and microwave dielectric properties of low temperature firing (K(0.5x)Bi(1-0.5x))(Mo(x)V(1-x))O4 ceramics with scheelite related structure

In the present work, the (K(0.5x)Bi(1-0.5x))(Mo(x)V(1-x))O(4) ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO(4) scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1-0.19, a BiVO(4) scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO(4) type and the other phase is a (K,Bi)(1/2)MoO(4) type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)(1/2)MoO(4) tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)(1/2)MoO(4) monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf value above 7800 GHz were achieved in ceramic samples near the ferroelastic phase boundary (at x = 0.09 and 0.10).     

Synthesis and spectroscopic characterization of water-soluble Mn-doped ZnO(x)S(1-x) quantum dots

A non-cadmium and water-soluble Mn-doped ZnO(x)S(1-x) QDs was synthesized with denatured bovine serum albumin (dBSA) as stabilizer under nitrogen atmosphere, and the as-prepared products were characterized by X-ray powder diffraction (XRD), UV-vis absorption spectroscopy, fluorescence (FL) emission spectroscopy, high resolution transmission electronmicroscopy (HRTEM) and Raman spectrum. XRD patterns indicate that the Mn-doped ZnO(x)S(1-x) QDs have a zinc-blende structure, and that manganese emerges in the form of divalent manganese (Mn(2+)) and trivalent manganese (Mn(3+)) (the intermediate of the reaction). The size of Mn-doped ZnO(x)S(1-x) QDs is about 3.2±0.7 nm according to HRTEM imaging. The FL spectra reveal that the Mn-doped ZnO(x)S(1-x) QDs have two distinct emission bands: the defect-related emission and the Mn(2+)-related emission, which exhibit a competing process. A good FL signal of the transition of Mn(2+) ((4)T(1)-(6)A(1)) is observed when the doping amounts are 1.0% and 20% respectively, and the as-prepared solutions are stable for more than 6 months at 4°C. This method has the advantages of good stability and environment-friendly stabilizer, for involving no heavy metal ions or toxic reagents.     

Alloyed (ZnS)(x)(Cu2SnS3)(1-x) and (CuInS2)(x)(Cu2SnS3)(1-x) nanocrystals with arbitrary composition and broad tunable band gaps

Cu(2)SnS(3) nanocrystals with metastable zincblende and wurtzite structures have been successfully synthesized for the first time. Alloyed (ZnS)(x)(Cu(2)SnS(3))(1-x) and (CuInS(2))(x)(Cu(2)SnS(3))(1-x) nanocrystals with arbitrary composition (0 ≤x≤ 1) and ultra-broad tunable band gaps (3.63 to 0.94 eV) were obtained.     

DFT investigation of the tri(amino)amine N(NH(2))(3)(2+) and the tri(azido)amine N(N(3))(3)(2+) dications and related mixed amino(azido)ammonium ions (N(3))(x)N(NH(2))(4-x)(+) (x = 0-4)(1)

Structures of the tri(amino)amine N(NH(2))(3)(2+) and the tri(azido)amine N(N(3))(3)(2+) dications were calculated at the density functional theory (DFT) B3LYP/6-311+G level. The tri(amino)amine dication (NH(2))(3)N(2+) (1) was found to be highly resonance stabilized with a high kinetic barrier for deprotonation. The structures of diamino(azido)amine dication (NH(2))(2)N(N(3))(2+) (2), amino(diazido)amine dication (NH(2))N(N(3))(2)(2+) (3), and tri(azido)amine dication (N(3))(3)N(2+) (4) were also found to be highly resonance stabilized. The structures and energetics of the related mixed amino(azido)ammonium ions (N(3))(x)N(NH(2))(4-x)(+) (x = 0-4) were also calculated.     

Alloyed Zn(x)Cd(1-x)S nanocrystals with highly narrow luminescence spectral width

High-quality alloyed Zn(x)Cd(1-x)S nanocrystals have been synthesized at high temperature by the reaction of a mixture of CdO- and ZnO-oleic acid complexes with sulfur in the noncoordinating solvent octadecene system. A series of monodisperse wurtzite Zn(x)Cd(1-x)S (x = 0.10, 0.25, 0.36, 0.53) nanocrystals were obtained with corresponding particle radii of 4.0, 3.2, 2.9, and 2.4 nm, respectively. With the increase of the Zn content, their photoluminescence (PL) spectra blue-shift systematically across the visible spectrum from 474 to 391 nm, indicating the formation of the alloyed nanocrystals. The alloy structure is also supported by the characteristic X-ray diffraction (XRD) patterns of these nanoalloys with different Zn mole fractions, in which their diffraction peaks systematically shift to larger angles as the Zn content increases. The lattice parameter c measured from XRD patterns decreases linearly with the increase of Zn content. This trend is consistent with Vegard's law, which further confirms the formation of homogeneous nanoalloys. These monodisperse wurtzite Zn(x)Cd(1-x)S nanoalloys possess superior optical properties with PL quantum yields of 25-50%, especially the extremely narrow room-temperature emission spectral width (full width at half-maximum, fwhm) of 14-18 nm. The obtained narrow spectral width stems from the uniform size and shape distribution, the high composition homogeneity, and the relatively large particle radius, which is close to or somewhat larger than the exciton Bohr radius. The process by which the initial structure with random spatial composition fluctuations turns into an alloy (solid solution) with homogeneous composition is clearly demonstrated by the temporal evolution of the PL spectra during the annealing progress.     

Modulation of the intercalation properties of copper-zinc mixed-metal phosphonate materials

New layered mixed divalent metal vinylphosphonates Cu(II) (1-x)Zn(II) (x)(O(3)PC(2)H(3)).H(2)O have been prepared from a range of pre-formed copper-zinc oxides Cu(II) (1-x)Zn(II) (x)O obtained by isomorphous substitution of zinc into the tenorite-type structure of Cu(II)O. The corresponding mixed divalent copper-zinc vinylphosphonates have been characterised by powder X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. All compounds have been shown to consist of a single-phase solid solution that crystallises in an monoclinic unit cell, space group P2(1)/c with a=9.86-9.90, b=7.61-7.64, c=7.32-7.35 A and beta=95.9-96 degrees, with the exception of the pure zinc vinylphosphonate (x=1), the structure of which is comparable to other Zn(II)(O(3)PR).H(2)O materials. Studies of the intercalation of n-butylamine into the range of copper-zinc vinylphosphonates have demonstrated that significant modulation of the adsorption properties occurs; whereas one mole of amine is intercalated into the pure zinc vinylphosphonate to give Zn(II)(O(3)PC(2)H(3)).(C(4)H(9)NH(2)), for all other members of the series two moles of amine are coordinated to give intercalated compounds of composition Cu(II) (1-x)Zn(II) (x)(O(3)PC(2)H(3)).[(C(4)H(9)NH(2))(1-x)(C(4)H(9)NH(2))(x)](2) from which the amine can be sequentially removed from the different metal sites; this opens up possibilities for further applications of these materials.