Sensitization of luminescence of antimony(III) in complexes with 6-methylquinoline in the spectral region of the <Emphasis Type="Italic">A</Emphasis> band

The luminescence properties of complexes of antimony (III) halides with 6-methylquinoline: (C₁₀H₉NH)₄Sb₂Cl₁₀ (I), (C₁₀H₉NH)₃SbBr₆ (II), and (C₁₀H₉NH)₄Sb₂I₁₀ (III) are studied. From analysis of data obtained by UV, photoelectron, and luminescence spectroscopy, it is concluded that the decrease in the energy gap between the highest occupied and lowest unoccupied molecular orbitals of the 6-methylquinoline molecules and antimony (III) halides is responsible for quenching of the luminescence of the 6-methylquinolinium cations and for occurrence of intrinsic luminescence of the antimony (III) ions in going from complex I to complexes II and III.     

Recombination-assisted creation of cation excitons and cross-luminescence quenching in CsCl crystals at high excitation densities

At high excitation densities, recombination-assisted creation of cation excitons, which transfer energy efficiently to the anion sublattice to initiate the luminescence of anion excitons and impurity centers, has been observed in CsCl crystals. At the same time, the creation of cation excitons competes with the electron recombination with cation holes and quenches the cross-luminescence. The intensity ratio of the cross-luminescence to exciton-impurity luminescence is different for crystal irradiation with γ rays and heavy particles.     

Evolution of Anion and Cation Excitons in Alkali Halide Crystals

The manifestations of the existence of free anion excitons, the processes of their self-trapping, and the coexistence of mobile and self-trapped excitons (STEs) in wide-gap alkali halide crystals are reviewed. The radiative channel of decay of anion excitons, yielding luminescence, and a particular type of nonradiative channel with the creation of elementary Frenkel defects (FDs) are considered. We analyzed the criteria for the efficiency of this channel for defect formation, possible mechanisms for the decay of self-trapped excitons with the production of neutral and charged anion Frenkel defects, and the processes of multiplication of electronic excitations in alkali halide crystals. Particular attention is paid to the decay of cation excitons, including from the point of view of the possibility of the low-temperature creation of elementary Frenkel defects in the cation sublattice of alkali halide crystals.     

The kinetics of exciton photoluminescence in mercuric iodide

Time-resolved photoluminescence (TRPL) of red mercuric iodide single crystal is measured at low temperatures and its two-photon luminescence is measured at room temperature. Sharp near band-gap luminescence is observed around 530 nm and was ascribed to radiative annihilation of free and bound excitons; the phonon replica of exciton luminescence are found between 533 and 540 nm at low temperatures. TRPL experiment reveals that near band-gap luminescence comprises fast and slow decay components and shows the different relaxation processes between free and bound exciton annihilation. Luminescence of bound excitons steeply lowers with increasing temperature and disappears about 40 K. A luminescence tail band is observed around 540 nm that is ascribed to defects in the anion sublattice. The temporal behavior of the tail band is described by rate equations very well. A broad luminescent band appears at 630 nm. The decay curves suggest that the luminescence is ascribed to the radiative recombination of donor-acceptor pairs and there are two kinds of mechanisms to control the decay. At room temperature, a luminescent band appears at the band-gap region, which shows the band-gap at room temperature is about 2.125 eV.     

掺Sb对PbWO_4晶体发光性能的改善

首次报道了ＰｂＷＯ４：Ｓｂ的光谱特性,包括透射谱和Ｘｅ灯光源激发的发射谱与激发谱．掺Ｓｂ具有增强绿光带、抑制红光带并大幅度提高光产额的效果．通过与空气退火ＰＷＯ发光的比较,对绿光带的起因、Ｓｂ掺杂的作用也进行了简要的讨论．     

Effect of dopant polarizability on oxygen sublattice order in phase-stabilized cubic bismuth oxides

Bismuth oxide doped with isovalent rare earth cations retains the high temperature defective fluorite structure upon cooling down to room temperature. However, these doped materials undergo an order-disorder transition of the oxygen sublattice at about 600 °C. When annealed at temperatures less than the transition temperature the oxygen sublattice continues to order, and consequently oxygen ion conductivity undergoes a decay. Modeling of ordered structures based on TEM diffraction patterns indicates a 〈111〉 vacancy ordering in the anion sublattice. Neutron diffraction studies show additional structural changes in the oxygen sublattice due to ordering. These studies indicate that the ionic conductivity is dependent on the distribution of oxygen ions between the regular 8c sites and the interstitial 32f sites in the fluorite structure. Earlier neutron diffraction studies indicate that short range ordering of the anion sublattice is related to the polarizability of the cations. In this study we relate the stability of the disordered structure and the formation of long range order to the polarizability of the dopant cations, in terms of the time constant for conductivity decay and the dielectric constant. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Ion Effects on the Performance of the Single-Layer Organic Light-Emitting Devices Based on Adding Salt Additives

The single-layer organic light-emitting devices provide a promising way for low-cost, large-area displays. Iridium (III) complex may play an important role to achieve this target due to its unique ionic characteristics. To achieve high-performance single-layer devices, blending the salt additives into the active layer is an effective strategy. However, the effects of different cation and anion additives on the device's performance are still unclear. Herein, the single-layer light-emitting devices are fabricated by using solution-processed iridium (III) complex mixed with various molecular salts. It is implied in the results that the improvement of the device luminescence and recombination efficiency is owing to the enhanced carrier injection and improved carrier balance in the emitting layer by the ion-additive-induced electrical double layer at the interface. The smaller cation can improve the carrier injection of the device more efficiently due to the stronger ion mobility and the anion with the smaller association coefficient shows a better device performance since the stronger dissociation ability of the ions can lead to a better ion migration ability. In addition, the introduction of poly (methyl methacrylate) into the active film can improve the single-layer device performances by reducing leak current in bulk.     

Photoluminescence, optical absorption and hypersensitivity in mono- and dinuclear lanthanide (Tb and Ho) β-diketonate complexes with diimines and bis-diimine bridging ligand

The photoluminescence properties of three Tb(III) complexes of the form [Tb₂(fod)₆(μ-bpm)], [Tb(fod)₃(phen)] and [Tb(fod)₃(bpy)] and optical absorption properties of their Ho(III) analogues (fod=anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, bpm=2,2′-bipyrimidine, phen=1,10-phenanthroline and bpy=2,2′-bipyridyl) in a series of solvents are presented. The luminescence of the complexes is sensitive to changes in environment (ligand/solvent) around Tb(III) and co-sensitization of the ancillary ligands. The enhancement of the luminescence intensity in coordinating solvents is attributed to the transformation of eight-coordination into less symmetric nine-coordination structure around Tb(III). Among phen and bpy, the phen is better co-sensitizer while bpm has been observed as poor co-sensitizer. The enhancement of the oscillator strength of ⁵G₆←⁵I₈ hypersensitive transition in the 4f-4f absorption in some coordinating solvents is attributed to decrease in the symmetry of the field around Ho(III) ion. The [Ho(fod)₃(phen)] is inert towards the solvents and retains its bulk structure and composition in solution. The transformation of the holmium complexes in DMSO into [Ho(fod)₃(DMSO)₂] species is found. The results reveal that the luminescence and 4f-4f absorption properties of lanthanide complexes in solution can be modulated by tuning the coordination structure through ancillary ligands and donor solvents.     

Energy Levels in the Forbidden Band of the Bi4Ge3O12 Ceramics

Thermally stimulated luminescence in the Bi₄Ge₃O₁₂ ceramics and also in the ceramics of the parent components Bi₂O₃ and GeO₂ is investigated. The similarity of the curves of the thermally stimulated luminescence in bismuth germanate with the structure of eulytine Bi₄Ge₃O₁₂ and sillenite Bi₁₂GeO₂₀ is explained. The relation of the thermally stimulated luminescence band in Bi₄Ge₃O₁₂ (with a maximum at 143 K) to the disruptions in the germanium sublattice and of the thermally stimulated band (with a maximum at 187 K) to the recombination processes in the bismuth sublattice is shown. It has been established that the light sum in the Bi₄Ge₃O₁₂ ceramics is stored most effectively upon excitation by light in an energy region of 4.4 eV.     

超声波辅助提取-HG-ICP-AES法测定中草药雷公藤中可溶态Sb(Ⅲ)和Sb(Ⅴ)

本文建立了用超声波辅助提取,氢化物发生-电感耦合等离子体原子发射光谱法测定中草药雷公藤中可溶态Sb(Ⅲ)和Sb(Ⅴ)的分析方法。研究了超声波辅助提取的影响因素、锑形态分离的最佳pH值、仪器工作条件对锑氢化物发生的影响及五价锑的还原条件,探讨了共存离子对锑测定的干扰及消除方法。Sb(Ⅲ)和Sb(Ⅴ)的检出限分别为0.3和2.4 μg·L-1, 相对标准偏差分别为3.9%和4.5%,样品加标回收率为93%～105%。     

Sensitization of Luminescence of Europium Compounds on Solid Matrices by Terbium (III) Ions

The conditions of sensitization of the luminescence of Eu(III) by Tb(III) ions in complexes with inorganic (Na₂WO₄) and organic (nalidixic acid) ligands in sorbates on solid matrices (zeolite CaX and crystalline zirconium phosphate (ZrP)) and in coprecipitation with CaWO₄ have been investigated. It has been established that the maximum sensitization of the europium luminescence is attained in the case where Eu and Tb are present in a 1:0.5 ratio. In this case, the integral intensity of luminescence of Eu(III) (the band with _max = 612 nm) in the sorbate of its complex with nalidixic acid on ZrP accounts for more than 60% of the luminescence intensity of the industrial photoluminophor Y₂O₃:Eu (FL-612) possessing red luminescence, and the intensity of Tb(III) luminescence (the band with _max = 545 nm) accounts for about 40% of the luminescence intensity of the photoluminophor Gd₂O₂S:Tb possessing green luminescence.     

Influence of Oxygen Vacancies on the Luminescence Spectra of Y2O3 Thin Films

Luminescence spectra of Y₂O₃ thin films annealed in air and in vacuum are investigated. It is established that the presence of oxygen vacancies leads to a decrease in the intensity of the luminescence band with a maximum at 3.4 eV (related to emission of selflocalized Frenkel excitons describing the excited state of a molecular ion (YO₆)^9–) and of the luminescence band with a maximum at 2.9 eV (related to the anion sublattice). It is revealed that the oxygen vacancies also lead to a decrease in the luminescence intensity in the 2.60, 2.35, 2.10. 1.90, and 1.70 eV bands that are related to radiative recombination in the donor–acceptor Y³⁺–O^2– pairs. The donor–acceptor distances are calculated.     

Metal-insulator transition by isovalent anion substitution in Ga1-xMnxAs: implications to ferromagnetism

We have investigated the effect of partial isovalent anion substitution in Ga1-xMnxAs on electrical transport and ferromagnetism. Substitution of only 2.4% of As by P induces a metal-insulator transition at a constant Mn doping of x=0.046 while the replacement of 0.4% As with N results in the crossover from metal to insulator for x=0.037. This remarkable behavior is consistent with a scenario in which holes located within an impurity band are scattered by alloy disorder in the anion sublattice. The shorter mean free path of holes, which mediate ferromagnetism, reduces the Curie temperature T_{C} from 113 to 60 K (100 to 65 K) upon the introduction of 3.1% P (1% N) into the As sublattice.     

Electronic relaxations of radiative defects of the anion sublattice in caesium bromide crystals and exoemission of electrons

The thermostimulated exoelectron emission (TSEE) is applied for investigation of the processes of radiative defects recombination in the nearsurface layer. Results of TSEE studies of radiatively excited CsBr crystals are presented. Dose dependences of the decay kinetics, TSEE spectrum structure and exosums were studied. Concentration of exoemission-active centres (EAC) and TSEE kinetics parameters have been calculated on the base of the bulk thermoactivated anion sublattice defect recombination. The attained result correlate with the electron centres concentration for irradiated crystals. In the framework of the Auger-like anion defects recombinational bulk model of exoemission from irradiated wide-band-gap crystals, the energy spectra of the exoelectrons excited on the F-centres are attained.     

A.C. electrical conductivity of pure and doped potassium perchlorate

A.C. electrical conductivity of potassium perchlorate (KP) has been measured in the temperature range 25–325°C at frequencies ranging from 50–500 Hz using an automated technique. The results are interpreted in terms of a novel mechanism involving Schottky defects in the anion sublattice and Frenkel defects in the cation sublattice. The conductivity behavior of KP is compared with literature data on similar low-symmetry systems containing polyatomic ions.     

Tin--antimony oxide oxidation catalysts

Tin--antimony oxide catalysts for the selective oxidation of hydrocarbons have been made by precipitation techniques. The dehydration of the amorphous dried precipitate by calcination at increasingly higher temperatures induces the crystallisation of a rutile-related tin dioxide-type phase and the segregation of antimony oxides which volatilise at elevated temperatures. The rutile-related tin dioxide-type phase contains antimony(V) in the bulk and antimony(III) in the surface. Specific catalytic activity for the oxidative dehydrogenation of butene to butadiene is associated with materials with large concentrations of antimony(III) in the surface. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hypersensitivity in the Luminescence and 4f?C4f Absorption Properties of Mono- and Dinuclear EuIII and ErIII Complexes Based on Fluorinated ??-Diketone and Diimine/ Bis-Diimine Ligands

The results of our investigation on the sensitized luminescence properties of three Eu(III) ??-diketonate complexes of the form [Eu₂(fod)₆(??-bpm)], [Eu(fod)₃(phen)] and [Eu(fod)₃(bpy)] and 4f?C4f absorption properties of their Er(III) analogues ( fod = anion of 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione, bpm = 2,2??-bipyrimidine, phen = 1,10-phenanthroline and bpy = 2,2??-bipyridyl) in a series of non-aqueous solvents are presented. The Eu(III) complexes are highly luminescent and their luminescence properties (intensity and band shape) are sensitive to the changes in the inner coordination sphere of the Eu(III) ion. The luminescence intensity of the mononuclear complexes in pyridine is drastically decreased. The coordination structure of the complexes in pyridine is transformed into a more symmetrical one which results into a slow radiative rate of the emission from the complexes. The ancillary ligands, phen and bpy are found better co-sensitizers as compared to the bpm to sensitize Eu(III)-luminescence. The 4f?C4f absorption properties (oscillator strength and band shape) of the Er(III) complexes demonstrate that ⁴G_11/2 ?? ⁴I_11/2 and ²H_11/2 ?? ⁴I_15/2 hypersensitive transitions of Er(III) are very sensitive in some coordinating solvents which reflects complex?Csolvent interaction in solution. The hypersensitive transitions of [Er(fod)₃(phen)] remain unaffected in any of the solvents and this complex retains its bulk composition in solution. The erbium complexes as well as the Er(fod)₃ chelate are invaded by DMSO. This solvent enters the inner coordination sphere by replacing heterocyclic ligand and the complexes acquire similar structure [Er(fod)₃(DMSO)₂] in this solvent. The results reveal that the luminescence and absorption properties of lanthanide complexes in solution can be controlled by tuning the coordination structure through ancillary ligands and donor solvents. This work shall prove useful in designing new biological applications with such probes.     

Atomic structure of InSb(001) and GaAs(001) surfaces imaged with noncontact atomic force microscopy

Noncontact atomic force microscopy (NC-AFM) has been used to study the c(8x2) InSb(001) and the c(8x2) GaAs(001) surfaces prepared by sputter cleaning and annealing. Atomically resolved tip-surface interaction maps display different characteristic patterns depending on the tip front atom type. It is shown that representative AFM maps can be interpreted consistently with the most recent structural model of A(III)B(V)(001) surface, as corresponding to the A(III) sublattice, to the B(V) sublattice, or to the combination of both sublattices.     

Use of Terbium(III) as a Probe for the Ion-Binding Properties of Tactic Polyacids and Triacidic Model Compounds

The binding properties of Tb(III) ions in configurationally different environments were investigated using luminescence intensity and lifetime measurements. The emission intensity of Tb(III) (⁵D₄–⁷F₅ transition) is directly dependent upon the number of coordinated water molecules (quenchers) bound in the inner coordination sphere. The more efficiently a ligand coordinates to Tb(III) ion, the more water molecules are expelled from the coordination sphere, thereby enhancing the luminescence intensity and lifetime of the ion. Isotactic and syndiotactic poly(methacrylic acids) (PMAs) were neutralized and complexed with Tb(III) ions in aqueous solutions. The luminescence intensities and lifetimes were monitored with _exc = 265, the hypersensitive excitation band at 286 and 370 nm. The isotactic PMA/Tb(III) complex exhibited a six times greater luminescence intensity than the syndiotactic PMA complex. Lifetime measurements showed 2.4 water molecules coordinated to Tb(III) ion in the isotactic PMA complex, while 3.4 water molecules were found to remain in the syndiotactic complex. Similar studies were also conducted on small organic model compounds such as Kemp's triacid and its configurational isomer. These data supported the polymeric results where the isotactic model, Kemp's triacid, exhibited a higher luminescence intensity and a longer lifetime than the Kemp's isomer. Lifetime results showed the Kemp's molecule retained approximately 2.7 water molecules, compared to four water molecules for the isomer. The validity of using the Kemp's molecules as polymeric models is also discussed.     

Luminescence and circularly polarized luminescence of macrocyclic Eu(III) and Tb(III) complexes embedded in xerogel and sol–gel SiO2 glasses

Luminescence, time-resolved luminescence, circularly polarized luminescence (CPL) and decay profiles of Ln(III)(15-crownether-5) (Ln=Ce, Sm, Eu, Tb) and Tb(III)-(R),(S)-cyclen derivative complexes doped in xerogel and sol–gel silica glasses are measured at temperatures down to 10 K to characterize luminescence properties and the electronic structure in the excited states. Luminescence spectral profiles and calculation of crystal field parameters (B₀⁽²⁾,B₂⁽²⁾) in the ⁵D₀→⁷F_J(J=1,2) transition give evidence of the fact that the pentagonal and planar structure of Eu(III) (15-crownether-5) does hold in xerogel and sol–gel glasses prepared at temperatures below 100°C. As annealing temperatures are increased from 80°C to 750°C, Eu(III) complexes in sol–gel glasses are found to decompose gradually to SiO₂:Eu³⁺. Tb(III)-(R) and (S)-cyclen derivative complexes in xerogel reveal at room temperature and 10 K sharp CPL spectra with luminescence dissymmetry factors g_lum=−0.1 and 0.1, respectively. These complexes doped in sol–gel glasses represent luminescence characteristics of rare earth ions encapsulated in the nano-porous host.