Te Clusters Research Articles

Ionic Liquids for Lanthanide and Actinide Chemistry A Bismuth‐Stabilized Metal‐Rich Telluride Lu9Bi≈1.0Te≈1.0 – Synthesis and CharacterizationMonazite and Zircon Type LaVO4:Eu Nanocrystals – Synthesis, Luminescent Properties, and Spectroscopic Identification of the Eu3+ SitesAlMe3, GaMe3 and InMe3 Adducts of N,N‐Bis(2‐{pyrid‐2‐yl}ethyl)hydroxylaminato Rare‐Earth Metal Complexes and Their Molecular Dynamics (Eur. J. Inorg. Chem. 18/2010)

AbstractThe cover picture highlights a few of the fine collection of articles assembled in this Cluster Issue on f elements, based on presentations at the 7th International Conference on f Elements held in Cologne (23–27 August 2009). The individual graphics making up the composite design are set against a background depicting Cologne, with the Cathedral barely visible in the mist. Just as the sun clears the mist to bring about a beautiful view, the knowledge that stems from the f elements is far reaching. The diversity of f‐element chemistry is reflected in the contributions shown on the cover. The solid‐state chemistry of Lu–Bi–Te clusters is highlighted by J. D. Corbett et al. (p. 2620ff), and the importance of ionic liquids in f‐element chemistry, as illustrated by the response of the lanthanide ionic liquid to an externally applied magnetic field, is reviewed by A. V. Mudring et al. (p. 2569ff). The binding mode in rare‐earth metal complexes with donor‐functionalised hydroxylaminato ligands is featured by N. W. Mitzel et al. (p. 2774ff), and the luminescence behaviour of LaVO4:Eu nanocrystals is revealed by C.‐H. Yan et al. (p. 2626ff). A hearty thanks to the authors for their valuable contributions to the cover.

Graphical Abstract: Eur. J. Inorg. Chem. 18/2010

AbstractThe cover picture highlights a few of the fine collection of articles assembled in this Cluster Issue on f elements, based on presentations at the 7th International Conference on f Elements held in Cologne (23–27 August 2009). The individual graphics making up the composite design are set against a background depicting Cologne, with the Cathedral barely visible in the mist. Just as the sun clears the mist to bring about a beautiful view, the knowledge that stems from the f elements is far reaching. The diversity of f‐element chemistry is reflected in the contributions shown on the cover. The solid‐state chemistry of Lu–Bi–Te clusters is highlighted by J. D. Corbett et al. (p. 2620ff), and the importance of ionic liquids in f‐element chemistry, as illustrated by the response of the lanthanide ionic liquid to an externally applied magnetic field, is reviewed by A. V. Mudring et al. (p. 2569ff). The binding mode in rare‐earth metal complexes with donor‐functionalised hydroxylaminato ligands is featured by N. W. Mitzel et al. (p. 2774ff), and the luminescence behaviour of LaVO4:Eu nanocrystals is revealed by C.‐H. Yan et al. (p. 2626ff). A hearty thanks to the authors for their valuable contributions to the cover.

SPIN-ORBIT AND SOLVENT EFFECTS IN THE LUMINESCENT [Re6Q8(NCS)6]4-, Q=S, Se, Te CLUSTERS: MOLECULAR SENSORS AND MOLECULAR DEVICES

Relativistic time-dependent density functional (TDDFT) calculations including spin orbit interactions via the zero order regular approximation (ZORA) and solvent effects using the COSMO model were carried out on the [Re 6 Q 8 (NCS) 6 ]4-, (Q = S, Se, Te) clusters. These calculations indicate that the lowest energy allowed electronic transitions are characterized by being of LMCT type. The calculated absorption maximum tends to shift to longer wavelengths as the face-capping chalcogenide ligand becomes heavier. Thus our calculations predict that the [Re 6 Te 8 (NCS) 6 ]4- cluster might be also luminescent. Due to the unusual properties exhibited by these and other isoelectronic and isostructural hexarhenium (III) chalcogenide clusters, hexamolybdenum halide clusters and hexatungsten halide clusters, we propose here the design of nanodevices, such as, molecular sensors and molecular nanocells for molecular electronics.

Towards a quantum-chemical simulation of the cadmium chalcogenide nanoclusters linked with biomolecules: An effect of terminating group upon the core geometry

Ab initio calculations of cadmium chalcogenide nanoclusters with terminating groups (H, O, N, and C atoms bound to the surface sulfur) are considered as a simulation for the species produced in typical synthesis of bio-conjugates with luminescent quantum dots. The Hartree–Fock (HF) method and density functional theory (DFT) are used assuming geometry optimization keeping the tetrahedral symmetry of cadmium chalcogenide cores. The geometry and electronic structure of CdX (X = S, Se, Te) clusters with size up to Cd17 (HF) and Cd4 (DFT) bound with hydrogen and –OH, –NH2, –CH3, and –CH2CH3 groups are calculated and the effects of the terminating groups upon core clusters are discussed.

Synthesis of Tellurium Sorption Complexes in Fully Dehydrated and Fully Ca2+-exchanged Zeolites A and X and their Single-crystal Structures

Single crystals of fully dehydrated and fully Ca 2+ -exchanged zeolites A (|Ca 6 |[Si 12 Al 12 O 48 ]-LTA) and X (|Ca 46 | [Si 100 Al 92 O 384 ]-FAU) were brought into contact with Te in fine pyrex capillaries at 623 K and 673 K, respectively, for 5 days. Crystal structures of Te-sorbed Ca 2+ -exchanged zeolites A and X have been determined by single-crystal X-ray diffraction techniques at 294 K in the cubic space group Pm3m (a = 12.288(2) A) and Fd 3 (a = 25.012(1) A), respectively. The crystal structures of pale red-brown |Ca 6 Te 3 |[Si 12 A 12 O 48 ]-LTA and black coloured |Ca 46 Te 8 | [Si 100 Al 92 O 384 ]-FAU have been refined to the final error indices of R 1 /wR 2 = 0.1096/0.2768 and R 1 /wR 2 = 0.1054/ 0.2979 with 204 and 282 reflections for which F o > 4σ(F o ), respectively. In the structure of |Ca 6 Te 31 |[Si 12 Al 12 O 48 ]-LTA, 6 Ca 2+ ions per unit cell were found at one crystallographic positions, on 3-fold axes equipoints of opposite 6-rings. In |Ca 46 Te 8 |[Si 100 Al 92 O 384 ]-FAU, 46 Ca 2+ ions per unit cell were found at four crystallographically distinct positions: 3 Ca 2+ ions at Ca(1) fill the 16 equivalent positions of site I, 21 Ca 2+ ions at Ca(2) fill the 32 equivalent positions of site I', 10 and 12 Ca 2+ ions at Ca(3) and Ca(4), respectively, fill the 32 equivalent positions of site II. The Te clusters are stabilized by interaction with cations and framework oxygen. In sodalite units, Te-Te distances of 2.86(10) and 2.69(4) A in zeolites A and X, respectively exhibited strong covalent properties due to their interaction with Ca 2+ ions. On the other hand, in large cavity and supercage, those of 2.99(3) and 2.76(11) A in zeolites A and X, respectively, showed ionic properties because alternative ionic interaction was formed through framework oxygen at one end and Ca 2+ cations at the other end.

Novel compounds based on [Re6Q8(L)6]4− (Q = S, Se, Te; L = CN, OH) and their applications

[Re6Q8L6]4− (Q = S, Se, Te) clusters can serve as promising “building blocks” for the creation of new porous framworks, nanoparticles and mesoporous materials. Since [Re6Q8L6]4−clusters have multi-anchoring sites for transition metals, metal–organic complexes, polymers, and multidentated metal complexes, they could be assembled to form various inorganic or organic–inorganic hybrid solids with new various spatial and chemical functions. Because of the controllable architectures and multi-anchoring sites of clusters together with their photoluminescence, rhenium cluster complexes are promising potential candidates as catalysts, chemical color sensors, magnetic materials, gas storage materials, optoelectronic, diagnostic agents, and gene/drug carriers. A new type of mesoscale material comprising [Re6Q8(CN)6]4− and various divalent transition metals in the presence of a liquid crystal template are obtained in 3D cubic, 2D hexagonal, and lamellar phases. The hexahydroxo complexes [Re6Q8(OH)6]4− (Q = S, Se) with high reactivities and a unique rhenium sulfido–cyanide compound, K8[Re12CS17(CN)6] with a C-centered {Re12} cluster unit were discovered and still many more new rhenium metal cluster complexes at various reaction conditions remain to be explored.

Two Routes of Electrophilic Addition and Unexpected Cluster Core Transformation in the Reactions of the K2[Fe3(μ3‐Q)(CO)9] (Q = Se, Te) Clusters with iPr2PCl

AbstractThe reactions of the K2[Fe3(μ3‐Q)(CO)9] (Q = Se (K2[1a]), Te (K2[1b])) clusters with iPr2PCl in THF lead to the formation of mixtures of two products: [{Fe2(CO)6(μ‐PiPr2)}2(μ4,η2‐Q2)] (2a, 2b) and [Fe3(μ3‐Q)(μ‐PiPr2)2(CO)7] (3a, 3b). The compounds 3a and 3b are the products of addition of two {PiPr2}+ units to two Fe‐Fe edges of the initial cluster accompanied by the elimination of two CO‐ligands. The compounds 2a and 2b are the products of the initial cluster core fragmentation followed by assembling of the diiron fragments via Q–Q bond formation.In contrast to that the reaction of K2[1a] with iPr2PCl in CH2Cl2 leads mostly to the electrophilic insertion of {PiPr2}+ into the Se–Fe bond and formation of [(μ‐H)Fe3(μ3,η2‐SePiPr2)(CO)9] (4a). Reaction of K2[1b] with iPr2PCl in CH2Cl2 leads primarily to unstable unidentified products, although 2b and 3b in minor amounts present in the reaction solution. The crystal structures of 2a, 2b, 3a and 4a were determined by single‐crystal X‐ray diffraction.

Reply to the comment on ‘ [formula omitted] ( n = 1–4) clusters in the gas phase’ by Z. Špalt, M. Alberti, and J. Havel

Recently we reported the existence of TeS clusters, Te n S 4 + ( n = 1–4) in the gas phase. The ions were detected in the laser desorption mass spectrum of bulk TeS powder. Špalt et al. have commented that there was ambiguity in that assignment and suggested that the peaks reported by us are due to Te clusters and not due to TeS clusters. Here in this reply, we show that there are unique features for the Te n S 4 clusters which are manifested in the mass spectra, although most of the intense peaks do overlap with the Te n clusters at the instrumental resolution investigated. The presence of Te S 4 + can be confirmed on the basis of its unique features.

IR laser co-pyrolysis of (CH 3) 2Te and (CH 3) 4Sn: Gas-phase formation and deposition of nanostructured SnTe

The first example on the gas phase synthesis of a metal chalcogenide through reactions between clusters of the metal and chalcogene is reported. Pulsed CO 2 laser-induced and SF 6-photosensitized homogeneous co-pyrolysis of gaseous (CH 3) 4Sn and (CH 3) 2Te results in chemical vapour deposition of nanostructured SnTe as proved by Raman and X-ray photoelectron spectroscopy and electron microscopy. The proposed mechanism of SnTe formation is explained by an intermediacy of Sn and Te clusters that are generated from pyrolysis of (CH 3) 4Sn and (CH 3) 2Te and that react in a hot reaction zone to SnTe.

Recombination kinetics of Te isoelectronic centers in ZnSTe

The recombination kinetics of Te isoelectronic centers in ZnS1−xTex (0.0065⩽x⩽0.85) alloys is studied by time-resolved photoluminescence (TRPL) at low temperature. The measured radiative recombination lifetimes of different Te bound exciton states are quite different, varying from a few nanoseconds to tens of nanosecond. As the bound exciton state evolves from a single Te impurity (Te1) to larger Te clusters (Ten,n=2,3,4), the recombination lifetime increases. It reaches maximum (∼40ns) for the Te4 bound states at x=0.155. The increase of the exciton lifetime is attributed to the increasing exciton localization effect caused by larger localization potential. In the large Te composition range (x>0.155), the exciton recombination lifetime decreases monotonically with Te composition. It is mainly due to the hybridization between the Te localized states and the host valence band states. The composition dependences of the exciton binding energy and the photoluminescence (PL) line width show the similar tendency that further support the localization picture obtained from the TRPL measurement.

Time-resolved photoluminescence of Te isoelectronic center in ZnS

The recombination dynamics of localized exciton in ZnS1-xTex ternary alloys has been investigated by time-resolved photoluminescence (PL) in a large Te concentration range from 0005 to 085. It is found that the radiativ e recombination lifetimes of different Te isoelectronic centers show a significa nt difference, varying from a few nanoseconds to tens of nanosecond. The lifetim e reaches a maximum of ～ 40 ns in the sample of x=015. The present result s could be understood in terms of the exciton localization effect. When the Te c oncentration is small, the Te isoelectronic centers evolve gradually from a sing le Te impurity (Te1) to the Te clusters (Ten). The exciton localization is enhanced, resulting in the increase of exciton recombination lifetime. When t he Te concentration is further increased, the Te clusters (Ten) becom e lar ge enough to hybridize the Te localized states and the host valence band states. Therefore, the excitons bound to Te isoelectronic centers become more or less d elocalized, resulting in a shorter lifetime. Furthermore, the concentration depe ndence of the exciton binding energy and the PL intensity variation with tempera ture have been mearsured. The results further confirm the above conclusion.

New Facets of CdTe Electrodeposition in Acidic Solutions with Higher Tellurium Concentrations

Cathodic electrodeposition of cadmium telluride has been investigated in acidic aqueous solutions (pH 1-2) to explore the effect of the tellurium (IV) concentration at values higher than in classical conditions (typically a few This concentration was increased to The effects of the deposition potential and the hydrodynamic regime have been studied in a systematic way. The composition of the films, as well as their optical and structural properties, have been determined as a function of deposition parameters. The deposition of stoichiometric CdTe is obtained in a potential domain, positive with respect to the cadmium deposition potential, whose width decreases from about 0.5 V to a few millivolts when the current density increases, i.e., for higher growth rates (up to 10 μm per h). A composition-potential diagram has been established. The results are explained by analysis of a general deposition mechanism of CdTe, which enables for the first time an equation of the boundary lines of the stoichiometric domain. Outside this stoichiometric window, surprisingly, the variation of the composition is not continuous between CdTe and pure Te, but presents a large domain where the atomic ratio Cd/Te of the films is fixed at 0.5. This indicates the formation of a definite compound with an apparent composition which can be explained by extending Kröger’s theory to metastable compounds, as a result of an intermediate step in the deposition mechanism revealed by working under higher rates conditions. An optical bandgap of 1.3 eV and an amorphous structure are found for this compound. Upon thermal treatment, a phase separation takes place between Te clusters and the CdTe matrix. The formation of cadmium ditelluride, which has not been reported yet for other deposition methods, illustrates the interest of electrodeposition for obtaining low-temperature metastable phases. © 2004 The Electrochemical Society. All rights reserved.

125Te NMR tomography of [Re 6] cluster in Re 6Te 15 and related cluster compounds

The static and magic angle spinning NMR solid-state spectra of Re 6Te 15 and a series of Re 6–Te cluster compounds demonstrate the positive and negative 125Te NMR chemical shifts indicating that the [Re 6] cluster distorts strongly magnetic field at the neighboring Te sites. The local magnetic field is decreased at the facial tellurium sites (Te face) and enhanced at the apexial tellurium sites (Te apex). The facial and sagittal sections of the Re 6–Te clusters were reconstructed from analysis of Te face and Te apex NMR spectra, respectively.

Room temperature luminescence from ZnSe1−xTex (x<1%) epilayers grown on (001) GaAs

Photoluminescence experiments have been performed to systematically study the effect of thermal processing on ZnSe1−xTex (x<1%) epilayers. Our results show that, a ZnSeTe epilayer under proper post growth thermal annealing can emit light in the visible range of 5500–7000 Å at room temperature. Thus by systematically processing these samples, they could be used for II–VI laser diodes that can operate at room temperature. The results from hydrogen passivation study done on these samples are consistent with the previous reports that the broadband emission is related to an isoelectronic defect, i.e., excitons bound to the Te clusters.

Ta97Te60: A Crystalline Approximant of a Tantalum Telluride Quasicrystal with Twelvefold Rotational Symmetry.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Heavily p-type doped ZnSe using Te and N codoping

We have studied photoluminescence (PL) of ZnSe samples codoped with Te and N in δ-layers. We have concluded that Te clusters are involved in the PL. We also compared the PL data of samples with lower Te concentrations to those with higher Te concentrations; the results corroborate the Te-cluster conclusion.

Ta97Te60: a crystalline approximant of a tantalum telluride quasicrystal with twelvefold rotational symmetry.

The crystal structure of a rational approximant of an unprecedented dodecagonal quasicrystal is reported. The atomic arrangement of the tantalum-rich telluride Ta(97)Te(60) has been determined from 30 458 symmetrically independent X-ray intensities of a crystal twinned by metric merohedry: a=2767.2(2), b=2767.2(2), c=2061.3(2) pm, space group P2(1)2(1)2(1), Pearson symbol oP628, 1415 variables, R(F)=0.059. A dodecagonal-shaped, vaulted Ta(151)Te(74) cluster with maximum symmetry 6mm can be seen as a characteristic motif of the structure. Each cluster measures about 2.5 nm across and consists of nineteen concentrically condensed hexagonal antiprismatic Ta(13) clusters which are capped with Te atoms. The Ta(151)Te(74) clusters can cover the plane distinctly in different ways, thereby forming a series of phases which are closely related both structurally and compositionally. In Ta(97)Te(60) the buckled clusters decorate the vertices of a square tiling at a 2 nm length scale to result in corrugated (infinity)(2)[Te(30)Ta(41)Ta(15)Ta(41)Te(30)] each about 1 nm thick. The lamellae are stacked along the c axis, corresponding to the direction of the pseudo-twelvefold axis of symmetry. Symmetry arguments are proposed that the twinning of the structure may be associated with a fine-tuning of weak interlayer Te-Te interactions which are reflected in a minimization of the deviation from the mean distance <d(Te-Te)> and a doubling of the stacking vector c.

Optical characterization of bulk ZnSeTe solid solutions

Optical characterization was performed on wafers sliced from crystals of ZnSe, ZnTe, and ZnSe1−xTex(0&amp;lt;x&amp;lt;0.4) grown by physical vapor transport. Energy band gaps at room temperature were determined from optical transmission measurements on 11 wafers. A best fit curve to the band gap versus composition x data gives a bowing parameter of 1.45. This number lies between the value of 1.23 determined previously on ZnSeTe bulk crystals and the value of 1.621 reported on ZnSeTe epilayers. Low-temperature photoluminescence (PL) spectra were measured on six samples. The spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for each of the ZnSe1−xTex samples, 0.09&amp;lt;x&amp;lt;0.39. For x=0.09, this emission energy is about 0.2 eV lower than the band gap energy measured at low temperature. As x increases the energy discrepancy gradually decreases and reduces to almost zero at x=0.4. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted as being associated with the exciton bound to Te clusters because of the high Te content in these samples.

Pseudo hysteresis current loop and negative differential resistance in cluster superlattice of tellurium in zeolite

We study electron transport properties of tellurium (Te) cluster superlattice in Linde type-A zeolite. Applying a constant voltage, current–voltage ( I– V) curve shows a hysteresis loop with a pseudo negative differential resistance (PNDA). The current loop and the current peak are history dependent. Under the same experimental conditions, we find that the current peak position moves to a higher voltage when the sample temperature is increased. Applying a variable voltage, I– V curve can be both monotonic and non-monotonic, depending on the frequency of the source. If a biased source is applied on the sample, the I– V curve will change with time, and eventually reach a stable state at which the current is a monotonical function of voltage. We clarify that both the current loop and peak are transient phenomena. The main transport mechanism is identified as non-resonant electron tunneling. The observed I– V characteristics can be attributed to the structure change of Te clusters inside the zeolite cages under an external electric field. The current peak can be understood as the effect of the finite transient time during which the Te cluster structure changes from one to another under an applied voltage. The temperature dependence of the peak position can be well described by many small collision assumption. With a simple mean-field-type approximation, the peak position is found to be proportional to the square root of the temperature.

Structure and electronic properties of the novel semiconductor alloy Cd1−xCuxTe

In this work an investigation of the structural and electronic properties of the novel semiconductor alloy Cd1−xCuxTe is presented. The samples were prepared as thin films by rf sputtering on substrates made of Corning glass. X-ray diffraction patterns showed that the incorporation of Cu into CdTe did not significantly affect the lattice parameters and that the incorporation of copper favors the growth of films preferentially oriented parallel to the (111) planes of cubic CdTe. Due to its sensitivity to local atomic order, the samples were studied by micro-Raman spectroscopy. The transverse and longitudinal optic modes regularly observed in CdTe were also found in the Cd1−xCuxTe samples with frequencies variations of less than 2 cm−1. The appearance of second and third harmonics of the longitudinal optic mode is indicative of high crystalline quality. The Raman bands become broader as a consequence of the disorder induced by the random incorporation of copper. From the Raman experiments it was also determined that the incorporation of Cu precluded the formation of Te clusters, which are commonly detected in CdTe thin films and bulk samples. The band gap of the alloys measured by optical transmission and photoreflectance spectroscopies tends to decrease with increasing copper content. The smallest band gap values were lower by approximately 60 meV compared to those of pure CdTe.