Elemental Tellurium Research Articles

Characteristics of the Te-based chalcogenide films dependently on the parameters of the PECVD process

Recently in Mochalov et al. (Opt Quant Electron 49(8):274–276, 2017; Plasma Chem Plasma Process 37(5):1417–1429, 2017; Superlattices Microstruct 111:173–180, 2017; Spectrochim Acta Part A Mol Biomol Spectrosc 191:211–216, 2018; New generation of materials for the near-mid IR sensors based on lead chalcogenides. In: 21st international conference on transparent optical networks (ICTON), 2019) the possibility of preparation of telluride films of different stoichiometry and phase composition by plasma deposition where the high-pure elemental arsenic, lead and tellurium were utilized as the starting materials have been shown. This manuscript generalizes the results of investigations of main characteristics of Te-based binary AsxTe100−x and PbTe chalcogenide films prepared in low-temperature non-equilibrium RF (40.68 MHz) argon plasma discharge at low pressure (0.1 Torr). The surface morphology, structure and thermal crystallization behavior of the films obtained were studied in dependence on the plasma parameters of the deposition process and compared.

Tellurium as the saturable absorber for the passively Q-switched laser at 1.34 µm.

The novel two-dimensional (2D) elementary tellurium is currently of great interest in optoelectronic and photonic applications. In this contribution, 2D tellurium nanosheets were successfully created by using the liquid-phase exfoliation method. With the as-prepared tellurium nanosheets as the saturable absorber (SA), we realized a passively $ Q $Q-switched ${\rm Nd} \text:{{\rm YVO}_4}$Nd:YVO4 laser operating at 1342 nm with a pulse width of 947 ns and single pulse energy of 2.25 µJ. Our work indicated the tellurium SA could be an efficient $ Q $Q-switcher for a near-infrared solid-state laser.

Scattering Mechanisms and Compositional Optimization of High‐Performance Elemental Te as a Thermoelectric Material

Abstractp‐Type elemental tellurium (Te) has been found to be a promising thermoelectric (TE) material due to its high band degeneracy near the valence band maximum, and has exhibited a high zT ≈ 1.0 above 600 K. However, when forming Te1−xSex solid solutions, the maximal zTs are reduced because of the severely decreased carrier concentration. It is demonstrated that Se alloying is beneficial for enhancing TE performance of elemental Te provided the carrier concentration is optimized. Through Se alloying, the lattice thermal conductivity is remarkably suppressed by the induced large mass and strain field fluctuation, while the power factor can be maintained at a relatively high value as a result of the moderate alloying scattering potential, the unchanged density‐of‐state effective mass, and the optimized carrier concentration in Te1−xSex alloys. Notably, a positive temperature dependence of carrier mobility is observed near room temperature in Te1−xSex, which is proven to be caused by grain boundary scattering. A maximal zT ≈ 1.05 at 625 K is realized in Te0.93Se0.04As0.03 alloys, about 9% higher than the Se‐free Te. The conversion efficiency between 300 and 625 K is also improved ≈18% via Se alloying.

Rongalite‐Promoted on Water Synthesis of Functionalised Tellurides and Ditellurides

AbstractThe on water reaction of sodium telluride with electrophiles has been explored. Na2Te, generated in situ through the rongalite (sodium hydroxymethanesulfinate)‐promoted reduction of elemental tellurium, reacts with a wide variety of electrophiles, including strained heterocycles, haloalkanes, Michael acceptors, and aryl diazonium salts, providing simple and rapid access to a broad range of novel functionalised symmetrical tellurides. The methodology well tolerated the presence of versatile functional groups such as alchohols, amines, esters, nitriles, and sulfones and allowed the incorporation of tellurium atoms into biologically relevant natural‐derived products. Furthermore, in the case of the nucleophilic ring opening of epoxides and aziridines, a judicious tuning of the reaction conditions enabled the synthesis of unreported β‐hydroxy‐ and β‐amino‐ditellurides, which were further employed as precursors of new functionalised unsymmetrical dialkyl tellurides. The thiol−peroxidase catalytic activity of hydroxy‐ditellurides has also been investigated in order to compare their antioxidant properties with those of homologous tellurides.magnified image

Freestanding ultra-thin silica

Silica (SiOx) thin films are promising for a wide range of applications, including catalysis, separation technology, biomedicine, or transparent super-hydrophilic films. Here, we present a study demonstrating a unique way of producing ultra-thin, freestanding silica films via silicon etching. This method utilizes silicon wafers with thermally oxidized surfaces and two common inorganic elements (sulfur and tellurium), which leads to high-rate chemical etching of the Si substrate, leaving behind freestanding silica layers. Thermodynamic calculations of the tellurium–silicon–sulfur (Te–Si–S) ternary phase diagram suggest that the removal of the Si substrate from the silica layers is due to chemical reactions that result in liquid/vapor formation of Si–S and Si–Te phases. Importantly, the chemical and physical properties of the silica film post-etch are comparable to those of the starting material. The process described here provides a route to produce large area, flexible glass substrates with widely tunable thicknesses from tens to thousands of nanometers.

Optimization of Tellurium and Antimony Extraction from Residue Generated in Alkaline Sulfide Leaching of Tellurium-Bearing Alkaline Skimming Slag Using Central Composite Design

A possible process for extracting tellurium and antimony from a residue generated in alkaline sulfide leaching of tellurium-bearing alkaline skimming slag was proposed. The central composite design was employed to define the optimal leaching conditions for tellurium and antimony extractions from the residue sample. Using a 23 factorial matrix, the best performance for tellurium and antimony extractions (96.36% and 99.64%) were obtained at 175 g L−1 Na2S concentration for 80 °C during 60 min. The notable degree for influencing tellurium and antimony extractions was leaching temperature, Na2S concentration, and leaching time. The analysis of variance results indicated that the regression model was significant and suitable to be used for the optimization of independent variables within the range. The model was validated under optimal operating conditions based on the experimental design results. Antimony and tellurium in the leach liquor were separated and recovered by H2O2 oxidation followed by Na2S-Na2SO3 reduction. 98.93% of antimony was precipitated selectively during H2O2 oxidation, while 95.06% of tellurium was precipitated during Na2S-Na2SO3 reduction. NaSb(OH)6 and elemental tellurium was obtained as the product.

Symmetry-enforced band crossings in trigonal materials: Accordion states and Weyl nodal lines

Nonsymmoprhic symmetries, such as screw rotations or glide reflections, can enforce band crossings within high-symmetry lines or planes of the Brillouin zone. When these band degeneracies are close to the Fermi energy, they can give rise to a number of unusual phenomena: e.g., anomalous magnetoelectric responses, transverse Hall currents, and exotic surface states. In this paper, we present a comprehensive classification of such nonsymmorphic band crossings in trigonal materials with strong spin-orbit coupling. We find that in trigonal systems there are two different types of nonsymmorphic band degeneracies: (i) Weyl points protected by screw rotations with an accordion-like dispersion, and (ii) Weyl nodal lines protected by glide reflections. We report a number of existing materials, where these band crossings are realized near the Fermi energy. This includes Cu2SrSnS4 and elemental tellurium (Te), which exhibit accordion Weyl points; and the tellurium-silicon clathrate Te16Si38, which shows Weyl nodal lines. The ab-initio band structures and surface states of these materials are studied in detail, and implications for experiments are briefly discussed.

Pressure-induced topological phase transition in noncentrosymmetric elemental tellurium

Recent progress in understanding the electronic band topology and emergent topological properties encourage us to reconsider the band structure of well-known materials including elemental substances. Controlling such a band topology by external field is of particular interest from both fundamental and technological viewpoints. Here we report possible signatures of the pressure-induced topological phase transition from a semiconductor to a Weyl semimetal in elemental tellurium probed by transport measurements. Pressure variation of the periods of Shubnikov-de Haas oscillations, as well as oscillation phases, shows an anomaly around the pressure theoretically predicted for topological phase transition. This behavior is consistent with the pressure-induced band deformation and resultant band-crossing effect. Moreover, effective cyclotron mass is reduced toward the critical pressure, potentially reflecting the emergence of massless linear dispersion. The present result paves the way for studying the electronic band topology in well-known compounds and topological phase transition by the external field.

Plasma-prepared arsenic telluride films: relationship between physico-chemical properties on the parameters of the deposition process

Previously, we demonstrated the principal possibility to synthesize arsenic telluride films of different chemical and phase composition by PECVD when we directly use elemental arsenic and tellurium as the precursors. This paper presents the results of systematic study of physicochemical properties of As-Te films prepared in low-temperature non-equilibrium RF (40 MHz) argon plasma discharge at low pressure (0.1 Torr) as well. The surface morphology, structure and thermal crystallization behavior of the films obtained were studied in dependence on the plasma parameters of the deposition process. The characteristics of stationary and transitional photoconductivity of the films have been studied as well.

Extreme Environments and High-Level Bacterial Tellurite Resistance.

Bacteria have long been known to possess resistance to the highly toxic oxyanion tellurite, most commonly though reduction to elemental tellurium. However, the majority of research has focused on the impact of this compound on microbes, namely E. coli, which have a very low level of resistance. Very little has been done regarding bacteria on the other end of the spectrum, with three to four orders of magnitude greater resistance than E. coli. With more focus on ecologically-friendly methods of pollutant removal, the use of bacteria for tellurite remediation, and possibly recovery, further highlights the importance of better understanding the effect on microbes, and approaches for resistance/reduction. The goal of this review is to compile current research on bacterial tellurite resistance, with a focus on high-level resistance by bacteria inhabiting extreme environments.

Diphenyl Ditelluride: Redox-Modulating and Antiproliferative Properties.

Tellurium is a rare element that has been regarded as a toxic, nonessential element, and its biological role is not clearly established. In addition, the biological effects of elemental tellurium and some of its organic and inorganic derivatives have been studied, leading to a set of interesting and promising applications. Diphenyl ditelluride (DPDT), an organic tellurium derivate, showed antioxidant, antigenotoxic, antimutagenic, and anticancer properties. The antioxidant and prooxidant properties of DPDT are complex and depend on experimental conditions, which may explain the contradictory reports of these properties. In addition, DPDT may exert its effects through different pathways, including distinct ones to those responsible for chemotherapy resistance phenotypes: transcription factors, membrane receptors, adhesion, structural molecules, cell cycle regulatory components, and apoptosis pathways. This review aims to present recent advances in our understanding of the biological effects, therapeutic potential, and safety of DPDT treatment. Moreover, original results demonstrating the cytotoxic effects of DPDT in different mammalian cell lines and systems biology analysis are included, and emerging approaches for possible future applications are inferred.

Dietary Estimated Intake of Trace Elements: Risk Assessment in an Italian Population

Dietary intake to trace elements may represent the most relevant source of exposure for the general, non-occupationally population, but some of them have been rarely evaluated. We measured content of fifteen trace elements (antimony, barium, beryllium, boron, cobalt, lithium, molybdenum, nickel, silver, strontium, tellurium, thallium, titanium, uranium, and vanadium) in 908 food and beverage samples through inductively coupled plasma mass spectrometry. We estimated their dietary intake using a validated semi-quantitative food frequency questionnaire collected from a population of the Emilia-Romagna Region in Northern Italy. We compared our estimates with tolerable upper intake levels reported by international agencies and we assessed the non-carcinogenic risk through calculation of total hazard quotient for each trace element according to the US-EPA approach. Overall, estimates of their dietary intake were substantially similar to those reported from other countries, and they fell below the tolerable upper intake levels provided by international agencies. The total hazard quotient for each trace element was below 1. Our findings provide updated estimates of food levels and dietary intake of trace elements far frequently evaluated in a sample of Italian adult consumers. They also suggest that any non-carcinogenic risk associated with intake of investigated trace elements may be ruled out in our population.

A Modular Approach to Phosphorescent π-Extended Heteroacenes.

A modular route to previously inaccessible classes of ring-fused π-extended heteroacenes bearing the heavy inorganic element tellurium (Te) is presented. These new materials can be viewed as n-doped analogs of molecular graphene subunits that exhibit color tunable visible light phosphorescence in the solid state and in the presence of air. The general mechanism of phosphorescence in these systems was probed experimentally and computationally via time-dependent density functional theory (TD-DFT). The incorporation of Te into π-extended oligoacene frameworks was achieved by an efficient Zr/Te transmetalation protocol; related zirconium-element exchange reactions have been used to prepare both electron-rich and electron-deficient heterocycles containing different elements from throughout the p-block. Therefore, the current study provides a clear path to incorporate inorganic elements into heteroacenes of greater complexity and side group selectivity compared to existing synthetic routes.

Bacterially synthesized tellurium nanostructures for broadband ultrafast nonlinear optical applications

Elementary tellurium is currently of great interest as an element with potential promise in nano-technology applications because of the recent discovery regarding its three two-dimensional phases and the existence of Weyl nodes around its Femi level. Here, we report on the unique nano-photonic properties of elemental tellurium particles [Te(0)], as harvest from a culture of a tellurium-oxyanion respiring bacteria. The bacterially-formed nano-crystals prove effective in the photonic applications tested compared to the chemically-formed nano-materials, suggesting a unique and environmentally friendly route of synthesis. Nonlinear optical measurements of this material reveal the strong saturable absorption and nonlinear optical extinctions induced by Mie scattering over broad temporal and wavelength ranges. In both cases, Te-nanoparticles exhibit superior optical nonlinearity compared to graphene. We demonstrate that biological tellurium can be used for a variety of photonic applications which include their proof-of-concept for employment as ultrafast mode-lockers and all-optical switches.

The tellurite-reducing bacterium Alteromonas macleodii from a culture of the toxic dinoflagellate Prorocentrum foraminosum

The Alteromonas macleodii strain 2328 was isolated from a clonal culture of the toxic dinoflagellate Prorocentrum foraminosum. The strain exhibits a resistance to high K2TeO3 concentrations (2500 μg/mL). A study of the growth dynamics of the strain exposed to K2TeO3 has shown a longer lag phase and a reduced stationary phase compared to those during cultivation with no toxicant. The fatty acids profile is dominated by 16:1 (n-7), 16:0, 17:1, 15:0, 18:1 (n-7), and 17:0. The 2328 strain belongs to the Gammaproteobacteria and is related to the genus Alteromonas with 99–100% sequence similarity to some intra-genome allele variants (paralogues) of 16S rRNA from A. macleodii. A phylogenetic reconstruction (ML and NJ), based on HyHK amino acid sequences, has revealed that the analyzed 2328 strain forms a common cluster with A. macleodii strains. In the presented work, the ability of A. macleodii to reduce potassium tellurite to elemental tellurium has been recorded for the first time. Bacteria reduce potassium tellurite to Te (0), nanoparticles of which become distributed diffusely and in the form of electron-dense globules in cytoplasm. Large polymorphous metalloid crystals are formed in the extracellular space. Such feature of the A. macleodii strain 2328 makes it quite attractive for biotechnological application as an organism concentrating the rare metalloid.

(Invited) Scalably-Nanomanufactured Tellurene: An Emerging 2-D Multifunctional Material

The reliable production of atomically-thin crystals with tailored properties is essential for exploring new science and implementing novel technologies in the 2-D limit. However, ongoing efforts are limited by the vague potential in scaling-up, restrictions on growth substrates and conditions, small sizes and instability of synthesized materials. In this talk, I will discuss our recent progress in the discovery and production of tellurene (2-D form of elemental tellurium) with an intriguing chiral-chain structure. The solution-synthesized tellurene crystals exhibit process-tunable thickness from a monolayer to tens of nanometers, lateral sizes ~ 100 mm, and can be transferred to designer substrates. I will further discuss our findings in 2-D tellurene’s material properties, as well as our efforts in the prototypical device explorations with the acquired fundamental understandings of tellurene’s properties. Our results show that the air-stable tellurene, as an emerging 2-D material, exhibits a plethora of intriguing physical properties appealing for applications in electronics, optoelectronics, energy, sensors, and quantum devices.

Removal of toxic tellurium (IV) compounds via bioreduction using flucloxacillin in aqueous acidic medium: A kinetic and mechanistic approach

This paper describes a novel method for the removal of potassium tellurite (TeIV), a toxic tellurium (IV) compound, via its bioreduction using the drug flucloxacillin (Flx) in an aqueous sulfuric acid solution. The kinetics of the bioreduction process were monitored using UV–Vis absorption spectra at an ionic strength of 2.0 mol dm−3 and 298 K. The reaction between TeIV and Flx was set at a 1:1 stoichiometry. The reduction reaction followed first-order kinetics for [Flx] and fractional-first-order kinetics for [TeIV] and [H+]. The effects of ionic strength and relative permittivity of the reaction medium were also explored. Supplementation with divalent transition metal ions enhanced the reduction rate. The reaction products were identified, in order of their stoichiometric results, spot tests and FT-IR spectra as 3-(2-chloro-6-fluorophenyl)-5-methylisoxazol-4-carbocylic acid, 5,5-dimethyl-thiazolidine-2,4-dicarboxlic acid, ammonium ion, carbon dioxide and elemental tellurium (Te0). The reaction rate dependence on temperature was studied, and the activation and thermodynamic parameters were assessed and discussed. The derived rate-law expression was found to be in excellent accordance with the acquired investigational outcomes. A conceivable reaction mechanism has been provided, which includes a reaction between the protonated flucloxacillin (Flx+) and tellurous acid (H2TeO3) as the essential reactive species, resulting in the construction of an intermediate complex. Such complex decays in the rate-determining step to yield the final reaction products.

Fungal formation of selenium and tellurium nanoparticles

The fungi Aureobasidium pullulans, Mortierella humilis, Trichoderma harzianum and Phoma glomerata were used to investigate the formation of selenium- and tellurium-containing nanoparticles during growth on selenium- and tellurium-containing media. Most organisms were able to grow on both selenium- and tellurium-containing media at concentrations of 1 mM resulting in extensive precipitation of elemental selenium and tellurium on fungal surfaces as observed by the red and black colour changes. Red or black deposits were confirmed as elemental selenium and tellurium, respectively. Selenium oxide and tellurium oxide were also found after growth of Trichoderma harzianum with 1 mM selenite and tellurite as well as the formation of elemental selenium and tellurium. The hyphal matrix provided nucleation sites for metalloid deposition with extracellular protein and extracellular polymeric substances localizing the resultant Se or Te nanoparticles. These findings are relevant to remedial treatments for selenium and tellurium and to novel approaches for selenium and tellurium biorecovery.

Low Thermal Conductivity and Optimized Thermoelectric Properties of p-Type Te-Sb2Se3: Synergistic Effect of Doping and Defect Engineering.

Elemental tellurium exhibits a promising thermoelectric performance, largely due to the optimization of the carrier concentration stemming from effective chemical doping. In this study, we demonstrate a novel approach to realize the collaborative manipulation of the electrical and thermal transport properties in the Te system via introduction of Sb2Se3. A series of p-type Te1-x(Sb2Se3)x (0 ≤ x ≤ 0.2) samples were fabricated through the melting method followed by spark plasma sintering. Electrically, antimony as a successful dopant enables a remarkable improvement of the carrier concentration, from ∼1018 to ∼1019 cm-3, thus resulting in a desired power factor across the entire temperature range. Thermally, utilization of defects engineering containing point defects, grain boundaries, dislocations, and secondary phase precipitates effectively reduces the lattice thermal conductivity. The coexistence of multi-frequency phonon scattering centers derived from the addition of Sb2Se3 leads to a minimum lattice thermal conductivity of 0.5 W m-1 K-1, approaching the amorphous limit. As a result, Te0.95(Sb2Se3)0.05 shows the highest figure of merit ZT ∼1 at 600 K, comparable to that of the toxic Te(As) thermoelectrics. This work not only points out that synergistic effects of both doping and defect engineering play a vital role in decoupling the thermoelectric parameters in the Te1-x(Sb2Se3)x system but also gives a referential strategy for a higher thermoelectric performance in other Te-based materials.

Microbial tellurite reduction and production of elemental tellurium nanoparticles by novel bacteria isolated from wastewater

Two highly tellurite-resistant bacteria were isolated from wastewater. Both bacteria could perform tellurite reduction under an initial pH of 5–9, temperature of 20–37°C, and salinity conditions lower than 5%. The maximum reduction rate of strain WYA (Vmax=20.45μMh−1) was much higher than that of strain WYS (Vmax=11.49μMh−1). Both bacteria produced tellurium nanorods that were accumulated intracellularly or extracellularly. Strain WYA is a new strain belonging to the Raoultella genus, whereas strain WYS belongs to the Escherichia genus. This study indicated that both these bacteria are potential microorganisms for green synthesis of tellurium nanorods, which have a wide application in environmental remediation and the nanotechnology industry.