Presence Of Tellurium Research Articles

Defect Engineering of MoTe2 via Thiol Treatment for Type III van der Waals Heterojunction Phototransistor.

Molybdenum ditelluride (MoTe2) nanosheets have displayed intriguing physicochemical properties and opto-electric characteristics as a result of their tunable and small band gap (Eg ∼ 1 eV), facilitating concurrent electron and hole transport. Despite the numerous efforts devoted to the development of p-type MoTe2 field-effect transistors (FETs), the presence of tellurium (Te) point vacancies has caused serious reliability issues. Here, we overcome this major limitation by treating the MoTe2 surface with thiolated molecules to heal Te vacancies. Comprehensive materials and electrical characterizations provided unambiguous evidence for the efficient chemisorption of butanethiol. Our thiol-treated MoTe2 FET exhibited a 10-fold increase in hole current and a positive threshold voltage shift of 25 V, indicative of efficient hole carrier doping. We demonstrated that our powerful molecular engineering strategy can be extended to the controlled formation of van der Waals heterostructures by developing an n-SnS2/thiol-MoTe2 junction FET (thiol-JFET). Notably, the thiol-JFET exhibited a significant negative photoresponse with a responsivity of 50 A W-1 and a fast response time of 80 ms based on band-to-band tunneling. More interestingly, the thiol-JFET displayed a gate tunable trimodal photodetection comprising two photoactive modes (positive and negative photoresponse) and one photoinactive mode. These findings underscore the potential of molecular engineering approaches in enhancing the performance and functionality of MoTe2-based nanodevices as key components in advanced 2D-based optoelectronics.

Accessing the environmental impact of tellurium metal

Abstract Tellurium is gaining technical significance because of being a vital constituent for the growth of green-energy products and technologies. Owing to its unique property of interchangeable oxidation states it has a tricky though interesting chemistry with basically unidentified environmental effects. The understanding of environmental actions of tellurium has significant gaps for instance, its existence and effects in various environmental sections related to mining, handling and removal and disposal methods. To bridge this gap it is required to assess its distinctive concentrations in the environment together with proper knowledge of its environmental chemistry. This in turn significantly requires developing systematic diagnostic schemes which are sensitive enough to present statistics in the concentrations which are environmentally relevant. The broad assessment of available statistics illustrates that tellurium is being found in a very scarce concentrations in various environmental sections. Very less information is available for the presence and effects of tellurium in air and natural water resources. Various soil and lake sediment analysis statistics indicate towards the presence of tellurium in soil owing to release of dust, ash and slag during mining and manufacturing practices. Computing the release and behavior of tellurium in environment needs a thorough assessment of its anthropogenic life cycle which in turn will facilitate information about its existing and prospective release in the environment, and will aid to handle the metal more sensibly.

Tin Selenide Molecular Precursor for the Solution Processing of Thermoelectric Materials and Devices.

In the present work, we report a solution-based strategy to produce crystallographically textured SnSe bulk nanomaterials and printed layers with optimized thermoelectric performance in the direction normal to the substrate. Our strategy is based on the formulation of a molecular precursor that can be continuously decomposed to produce a SnSe powder or printed into predefined patterns. The precursor formulation and decomposition conditions are optimized to produce pure phase 2D SnSe nanoplates. The printed layer and the bulk material obtained after hot press displays a clear preferential orientation of the crystallographic domains, resulting in an ultralow thermal conductivity of 0.55 W m-1 K-1 in the direction normal to the substrate. Such textured nanomaterials present highly anisotropic properties with the best thermoelectric performance in plane, i.e., in the directions parallel to the substrate, which coincide with the crystallographic bc plane of SnSe. This is an unfortunate characteristic because thermoelectric devices are designed to create/harvest temperature gradients in the direction normal to the substrate. We further demonstrate that this limitation can be overcome with the introduction of small amounts of tellurium in the precursor. The presence of tellurium allows one to reduce the band gap and increase both the charge carrier concentration and the mobility, especially the cross plane, with a minimal decrease of the Seebeck coefficient. These effects translate into record out of plane ZT values at 800 K.

Electrodeposition of Tellurium Thin Films from Citric Acid Bath

Tellurium is a very interesting element which exhibits intermediate properties of metals and non-metals. Semiconducting properties of tellurium allow for a number of its applications in many industry branches. Physicochemical properties of thin tellurium layers are more and more frequently exploited in many electronic devices like infrared photoconductive detectors, holographic recording materials, sensors, thermoelectric, piezoelectric and optoelectronic devices. Recently, high interest has been focused on gas sensors constructed on the basis of thin tellurium layers whose sensitivity and selectivity significantly depend on the thickness of semiconducting coatings. Moreover, this element, when combined with d-block metals, allows for obtaining advanced optical materials used in constructing solar cells, diodes and radiation emitters of different wave length. The leading methods of thin tellurium coatings production are physical and chemical vapour deposition methods, which enable production of coatings with different thickness. However, one of the alternative ways to obtain tellurium coatings can be the electrochemical method. The process of electrochemical tellurium deposition can be performed both from acidic and alkaline aqueous solutions. However, it is difficult to achieve it due to electrochemical properties of tellurium and its very low solubility in acidy aqueous solutions. It results in conducting deposition of tellurium under conditions of diffusion control, which means that the rate of the coating growth is very low and it results in amorphous or fine-crystalline structure. Moreover, there is a risk of obtaining coatings of dendritic structure or even powders. Additionally, due to the mechanism of tellurium reduction from aqueous solutions, a competitive reaction leading to the reduction of deposited tellurium to Te-2 may occur causing dissolution of the tellurium coating and a decrease of the electrolysis process efficiency. This work presents the description of the electrochemical process of formation thin tellurium layers from citrate acidic solution. The suggested methodology consists in the preparation of stable acidic baths with high content of tellurium, and with the addition of citrate acid. In order to analyse the mechanism of the process of tellurium deposition, the electroanalytical tests were conducted. The tests of cyclic voltammetry and hydrodynamic ones were performed with the use of polycrystalline gold disk electrode. The range of potentials in which deposition of tellurium in direct four-electron process is possible was determined as well as the reduction of deposited Te0 to Te2- and its re-deposition as a result of the comproportionation reaction. On the basis of the obtained results, the deposition of tellurium was conducted by the potentiostatic method. The influence of a deposition potential and a concentration of TeO2 in the solution on the rate of tellurium coatings deposition was examined. The presence of tellurium was confirmed by X-ray spectrofluorometry and electron probe microanalysis. In order to determine the phase composition and the morphology, the obtained coatings were analysed with the use of x-ray diffraction and scanning electron microscopy. This work was supported by the Polish National Center of Science under grant 2011/01/D/ST5/05743.

Analysis of tellurium thin films electrodeposition from acidic citric bath

This work presents the description of the electrochemical process of formation thin tellurium layers from citrate acidic solution. The suggested methodology consists in the preparation of stable acidic baths with high content of tellurium, and with the addition of citrate acid. In order to analyse the mechanism of the process of tellurium deposition, the electroanalytical tests were conducted. The tests of cyclic voltammetry and hydrodynamic ones were performed with the use of polycrystalline gold disk electrode. The range of potentials in which deposition of tellurium in direct four-electron process is possible was determined as well as the reduction of deposited Te° to Te2− and its re-deposition as a result of the comproportionation reaction. On the basis of the obtained results, the deposition of tellurium was conducted by the potentiostatic method. The influence of a deposition potential and a concentration of TeO2 in the solution on the rate of tellurium coatings deposition was examined. The presence of tellurium was confirmed by X-ray spectrofluorometry and electron probe microanalysis. In order to determine the phase composition and the morphology, the obtained coatings were analysed with the use of x-ray diffraction and scanning electron microscopy.

Reduction Mechanism of Tellurium Species from Copper Electrowinning Solutions

ABSTRACTThe presence of tellurium in copper–nickel sulfide ores results in downstream contamination of leach solutions and electrolytes. Tellurium must be removed from leach solutions before electrowinning to prevent contamination of copper cathodes. Cuprous ion is industrially used as a reductant to remove tellurium ions. However, the reduction kinetics of tellurium ions with cuprous is not well known. In this study, the slow TeVI reduction step with cuprous was identified and a plausible TeVI reduction mechanism was suggested. The rate‐determining step was investigated by studying the kinetics of the coupled reaction of TeVI and TeIV with cuprous. The rate law suggested for the reduction of TeIV with cuprous and the coupled kinetics equation for consecutive reduction reactions of TeIV and TeVI were derived. It was shown that the rate constant of the coupled reaction is very close to the rate constant calculated based on the assumption that TeVI reduction is a rate‐determining step.

Electrowinning Of Tellurium From Acidic Solutions

AbstractThe process of electrochemical deposition of tellurium was studied. Preliminary researches embrace the voltammetry and microgravimetric measurements. According to the results the electrolysis of tellurium was conducted under potentiostatic conditions. There was no deposition of tellurium above potential −0.1 vs. Ag/AgCl electrode in 25°C. The process of deposition is observed in the range of potentials −0.1 to −0.3 V vs. Ag/AgCl. The presence of tellurium was confirmed by XRF and XRD. The obtained deposits were homogenous and compact. Below potential −0.3 V vs. Ag/AgCl the Faradaic efficiency of the tellurium deposition decreased due to reduction of Te to H2Te and hydrogen evolution.

Modification of Polyethylene and Polypropylene Composites with Different Rubbers in the Presence of Tellurium

To improve the service and physicomechanical characteristics of polyolefins, a composite based on LDPE + isotactic PP has been produced with the use of butadiene–styrene and butadiene–acrylonitrile elastomers as modifiers. Tellurium was selected as the antioxidant. It was established that the composite obtained possesses high strength and deformation properties, and also a high Vicat softening point and cracking resistance.

Preparation of PbTe-based materials through thermal decomposition of lead acetate

This paper examines the possibility of producing microstructured lead telluride with a high grain-boundary density through the thermal decomposition of lead acetate in the presence of tellurium under a reducing atmosphere, followed by cold compaction of the powder and hot pressing of the green compacts. The formation of fine lead telluride particles was followed using differential thermal analysis and thermogravimetry. Electron microscopy, X-ray microanalysis, and specific surface area measurements were used to assess the conductivity and size of the powder particles and the structure and composition of the grains in the hot-pressed samples in relation to the preparation conditions and starting-mixture composition.

Synthesis and Crystal Structure of >Bis(tetrapropylammonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [NnPr4]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

AbstractDark brown crystals of [NnPr4]2[TeBr6(SeBr2)2] (1) were obtained when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and tetrapropylammonium bromide. The salt 1 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 14.7870(3) Å, b = 9.5523(3) Å, c = 16.7325(3) Å, β = 110.56(10)° (at 123(2) K). In the solid state the [TeBr6(SeBr2)2]2– anion contains a nearly regular [TeBr6] octahedron in which the four equatorial bromo ligands have developed bonds to SeII atoms of the SeBr2 molecules. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are 3.0000(4) and 3.0561(4) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV–Br distances are in the range 2.6816(3)–2.7131(3) Å and the SeII–Br bond lengths in the coordinated SeBr2 molecules are 2.3548(4) and 2.3725(4) Å.

Photopolymerization of n-Butyl Methacrylate in Solutions Initiated by Diphenyl Ditelluride

Radical photopolymerization of n-butyl methacrylate (BMA) with diphenyl ditelluride [DPDT] as a photoinitiator has been carried out by visible light excitation at room temperature for 24 h. The system followed non-ideal kinetics, i.e., R p ∝ [DPDT]2.00[BMA]1.75. The FT-IR spectrum showed a band at 1721 cm−1 due to acrylate C=O Str. The 1H-NMR spectrum showed a peak at 3.9 δ due to –O–CH2– of acrylate. The 13C-NMR spectrum showed resonance signals at δ 175.55–178.20 ppm due to carbonyl carbon. The presence of tellurium in polymer is confirmed by qualitatively, as well as with ICP-MS. The ESR showed the free radical mode of polymerization and the gyromagnetic constant g has been computed as 2.2203.

Studies on the radical polymerization of N-vinyl 2-pyrrolidone initiated by diphenyl ditelluride

N-vinyl pyrrolidone (NVP) was polymerized in dioxan at 60 ± 0.1°C for 1 h using diphenyl ditelluride as radical initiator. The system follows ideal kinetics i.e. R p α [DPDT]0.5[NVP]. The activation energy and dissociation constant is computed as 46 kJ mol−1 and 1.1 × 10−11 s−1, respectively. The polymer was characterized with the help of FTIR, 1H-NMR, 13C-NMR, ESR spectroscopy. The FT-IR spectrum showed bands at 1660–1680 cm−1 due to combination of >C = O and C–N stretching. The gyromagnetic constant ‘g’ has been computed as 2.2203. The main product of this reaction were poly(N-vinylpyrrolidone)s with phenyl tellanyl ends. The presence of tellurium in polymer is confirmed by ICP analysis. The DSC shows the T g of poly(N-vinylpyrrolidone) is 168°C due to rigid pyrrolidane group. The TGA showed that polymer was stable up to 380°C.The GPC studies showed that the weight average molecular weight decreases with increase of [DPDT].

Diphenyl-ditelluride-initiated alternating co-polymerization of N-vinyl-2-pyrrolidone with methyl methacrylate

The free radical co-polymerization of N-vinyl-2-pyrrolidone and methyl methacrylate was carried out at 60°C in the presence of diphenyl ditelluride using 1,4-dioxane as the solvent. The kinetic expression is R p ∝ [DPDT]0.5 [MMA][NVP]. The energy of activation has been computed as 50 kJ/mol. The presence of tellurium in the co-polymer has been confirmed by qualitatively, as well as induced coupled plasma mass spectroscopy (ICP-MS). The FT-IR spectrum of the co-polymer shows the bands at 1728 cm−1 and 1680 cm−1 due to ester and ketonic stretching of MMA and NVP, respectively. The monomer sequence distribution has been given by 13C-NMR spectroscopy. The co-monomer feed composition was observed to have a strong effect on the overall co-polymerization rate. The reactivity ratio of the binary system was determined, using the Kelen–Tüdos method, to be r (MMA) = 0.043 and r (NVP) = 0.016, indicating an alternating tendency in the formed co-polymer.

Synthesis of tellurium containing syndiotactic polymethyl methacrylate using diphenyl ditelluride as a novel initiator

The synthesis of syndiotactic polymethyl methacrylate containing tellurium by using diphenyl ditelluride in the dioxan at (60 ± 0.1)°C for 2 h has been carried out. The presence of tellurium in the polymer has been confirmed qualitatively as well as by induced coupled plasma mass spectroscopy (ICP-MS). The electron spin resonance spectrum shows the presence of TėPh, and value of gyromagnetic constant g has been calculated as 2.2203. The Tg of the polymer, measured by DSC, is 105°C. The syndiotactic nature has been confirmed by FTIR and NMR spectroscopy and DSC. The system follows ideal kinetics with activation energy 66 kJ mol−1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1017–1022, 2006

Synthesis and Crystal Structure of Bis(methyltriethylammonium) Hexabromotellurate(IV)‐tris{dibromodiselenate(I)}, [NMeEt3]2n[TeBr6(Se2Br2)3]n, Containing a Chain‐Polymeric Mixed‐valence Bromotellurate(IV)‐Selenate(I) Anion

AbstractRed crystals of [NMeEt3]2n[TeBr6(Se2Br2)3]n (1) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr6(Se2Br2)3]2— anions contain nearly regular octahedral [TeBr6]2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se2Br2 molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the SeI atoms of the Se2Br2 molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se2Br2 as acceptors. The TeIV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se2Br2 molecules are: SeI—SeI = 2.267(2) and 2.281(2) Å, SeI—Br = 2.340(1), 2.353(1) and 2.337(1) Å.

Synthesis and Crystal Structure of Bis(methyltriphenylphosphonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [PMePh3]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

AbstractBrown crystals of [PMePh3]2[TeBr6(SeBr2)2] (1) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr6(SeBr2)2]2— anion contains a nearly regular [TeBr6] octahedron where the four equatorial bromo ligands each have developed a bond to the SeII atom of a SeBr2 molecule. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV—Br distances are in the range 2.67—2.72Å, and the SeII—Br bond lengths in coordinated SeBr2 molecules in the range 2.33—2.34Å.

Assay of Vancomycin and Dobutamine Using Sodium Metaperiodate

Three simple and sensitive visible spectrophotometric methods (A–C) are described for the assay of vancomycin (VCM) and dobutamine (DB) (in pure form and in pharmaceutical formulations). These methods are based on the oxidation of vancomycin or dobutamine with excess sodium metaperiodate. Either the products formed (liberated aldehyde with 3-methyl-2-benzothiazolinone hydrazone (MBTH), method A; iodate with p-methylaminophenol sulphate (PMAP), sulphanilamide, in the presence of Mo (VI), method B) or the amount of periodate consumed (celestine blue in the presence of tellurium (IV), method C) are estimated. In this paper the reaction mechanism is presented and all the variables are optimized. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2.5–30, 0.6–6.0; 2–24, 0.8–9.6 and 2–24, 0.76–6.0 µg ml−1 for methods A, B and C of VCM and DB respectively. The validity of the proposed methods was tested by analyzing pharmaceutical formulations containing drug (VCM, DB) and the relative standard deviations were within 1.0%. Recoveries are 99.55–99.94%.

Investigation of thallium hydride generation using in situ trapping in graphite tube by atomic absorption spectrometry

Thallium hydride was generated from aqueous solutions by merging sample and sodium tetrahydroborate reductant in a batch system. In situ preconcentration of volatile thallium hydride in a preheated graphite furnace coated with palladium, which was used as both the collection medium and atomizer, greatly improved the sensitivity for the determination of thallium by hydride generation atomic absorption spectrometry. The presence of tellurium can increase the generation efficiency of thallium hydride. The operating conditions were optimized. The calibration graph is linear up to 100 ng and the characteristic mass for thallium was 0.92 ng which is seventeen times lower than that obtained with the heated quartz tube atomizer.

Tellurium(IV) tetrachloride catalysed facile knoevenagel reaction

Abstract Non-enolisable aldehydes (I) and active methylene compounds (II) react in the presence of tellurium(IV) tetrachloride (catalytic) to give the corresponding α, β-unsaturated carbonyl compounds (III) in excellent yields and high purity.

Electrochemical deposition and characterization of CdTe polycrystalline thin films

CdTe thin films have been prepared by potentiostatic electrodeposition from acidic solutions containing CdSO 4 and TeO 2, or CdCl 2 and TeO 2. The films were characterized by X-ray diffraction and scanning electron microscopy. The influence of the deposition potential and bath temperature on the presence of tellurium and crystallite size was studied. The effect of annealing treatment on the increase in grain size of the electrochemically deposited CdTe films has been investigated.