[en] The equation for a calculation of the liquidus line of the In₂Te₃-Co₃Te₄ system state diagram was derived. With this purpose, the liquidus line, consisting two branches, was accepted to be similar to branches of two parabolas, that is why the parabola equation was used for the derivation of the mathematical expression. Using the suggested equation, content values and fusion temperatures of interacting components may be calculated with high accuracy, in the broad concentration interval

No abstract available

[en] Magnetism in semiconductor two-dimensional (2D) materials is gaining popularity due to its potential applications in memory devices, sensors, spintronics, and biomedical applications. Here, 2D cobalt telluride (CoTe) has been synthesized from its bulk crystals using a simple and scalable liquid-phase exfoliation method. The ultrathin CoTe shows ~ 400 times enhancement in its magnetic saturation values compared to the bulk form. The UV-Vis absorption spectra reveal superior absorption in the high-energy region, suggesting a semiconducting nature. Furthermore, we explain the bandgap and origin of high magnetic behavior by density functional theory (DFT) calculations. The 2D CoTe shows a larger magnetism compared to bulk CoTe due to the reduced coordination number of the surface atoms, shape anisotropy, and surface charge effect. Additionally, the semiconducting nature and surface charges are fruitfully utilized for degradation of different toxic dyes under magnetic field and visible light irradiation. Therefore, atomically thin magnetic CoTe can give a new perspective to the separation of charge carriers.

[en] We investigate the electronic structures and stability for Ni/Bi₂Te₃, NiTe/Bi₂Te₃, Co/Bi₂Te₃ and CoTe₂/Bi₂Te₃ interfaces by first-principles calculations. It is found that the surface termination strongly affects the band alignment. Ni and Co are found to form Ohmic contacts to Bi₂Te₃. The interface formation energy for Co/Bi₂Te₃ interfaces is much lower than that of Ni/Bi₂Te₃ interfaces. Furthermore, we found that NiTe on Bi₂Te₃ is more stable than Ni, while the formation energies for Co and CoTe₂ on Bi₂Te₃ are comparable.

[en] Cobalt telluride, with tunable magnetism and ferromagnetism that hinged upon the stoichiometric ratio, has emerged as a new member of 2D materials in the last decade. Metallic doping by sodium (Na) and platinum (Pt) atoms below critical concentrations is found to enhance the magnetism of cobalt telluride. After thinning cobalt telluride down to few-layer, the saturation magnetism is improved by two order of magnitudes because of the oxidation state of cobalt (Co) and reduced coordination number of the surface atoms. In 2D limit, cobalt di-telluride possesses Dirac band structure with many nodal lines that correlate with quantum criticality and other fantastic physics. In this mini-review, the crystal and band structures of cobalt telluride categorized by stoichiometric ratio are overviewed after briefing the introduction. Both top-down and bottom-up methods are then discussed to offer optimum solutions for each specified application scenario. Afterward, emerging magnetic and electronic properties and credit enhancements are launched accompanied with their key advances. Beyond these, the faced challenges and possible directions of future research are also provided, attempting to boost both fundamental physics and device applications based on 2D cobalt telluride. (© 2023 Wiley‐VCH GmbH)

No abstract available

[en] Development of high-performance electrocatalysts for oxygen evolution reaction (OER) is the key to improve the efficiency of many energy conversion process. Metal telluride is a type of low-cost OER catalyst with promising activity. To improve the OER performance of metal telluride, we propose herein the design of composite metal telluride OER catalyst that fully utilizes the advantages of each component in the composite. The developed Ni₃Te₂-CoTe/CC composite electrocatalyst has a high OER performance than its Ni₃Te₂ and CoTe counterpart. The improved OER performance of the composite Ni₃Te₂-CoTe electrocatalyst can be on one hand ascribed to the high density of state near Fermi level in Ni₃Te₂ phase, as suggested by DFT analysis. On the other hand, the introduction of CoTe phase in the composite effectively enlarges the electrochemical surface area of the catalyst, thus improving the activity of the composite.

[en] Van der Waals (vdW) materials are an indispensable part of functional device technology due to their versatile physical properties and ease of exfoliating to the low-dimensional limit. Among all the compounds investigated so far, the search for magnetic vdW materials has intensified in recent years, fueled by the realization of magnetism in 2D. However, metallic magnetic vdW systems are still uncommon. In addition, they rarely host high-mobility charge carriers, which is an essential requirement for high-speed electronic applications. Another shortcoming of 2D magnets is that they are highly air sensitive. Using chemical reasoning, TaCo${}_2$Te${}_2$ is introduced as an air-stable, high-mobility, magnetic vdW material. It has a layered structure, which consists of Peierls distorted Co chains and a large vdW gap between the layers. It is found that the bulk crystals can be easily exfoliated and the obtained thin flakes are robust to ambient conditions after 4 months of monitoring using an optical microscope. Signatures of canted antiferromagntic behavior are also observed at low-temperature. TaCo${}_2$Te${}_2$ shows a metallic character and a large, nonsaturating, anisotropic magnetoresistance. Furthermore, the Hall data and quantum oscillation measurements reveal the presence of both electron- and hole-type carriers and their high mobility. (© 2021 Wiley‐VCH GmbH)

[en] Cobalt tellurides in the composition range CoTe_1.3-CoTe₂ crystallize in a CdI₂-type structure with short intra- and interslab Te-Te contacts indicating a polymeric network with multiple Te-Te bonds explaining the very low c/a values of 1.38 to 1.41 of the hexagonal cells. Single-crystal x-ray investigations performed on CoTe₂ confirm the marcasite-type structure in the centrosymmetric space group Pnnm. Experimental valence band spectra (UPS) confirm that the Co tellurides in the composition range CoTe_x (1.3 < x < 2) are metals. The emission at the Fermi level E_F decreases with the Te content and is due to Co 3d and Te 5p states. This assignment is supported by the results of the calculated density of states curve (DOS) which demonstrates that Te p states contribute about 50% in the CdI₂-type and about 35% in the marcasite-type structure. The Te d states contribute about 15% to the total Te contributions. This behaviour cannot be understood on the basis of a simple tight-binding description, ignoring d-valence states of Te. Core level spectra (XPS) suggest that all CoTe_x samples are best described as intermetallic compounds. Small chemical shifts between the different samples are mainly due to the different Madelung contributions rather than to changes of the electron density located on the Co atoms. An oxidation number for Te <-1 in all CoTe_x samples is deduced, in good agreement with the value of about -1.3 for the Te in CoTe₂ that would be deduced from the relation between the Te-Te distances versus oxidation states of the anion in (Te₂)^-11, Te^-11. The three-dimensional character of the Co tellurides deduced from the crystal structure is further confirmed by the calculated energy dispersion E(k). (author)

[en] Bisphenol A (BPA) is an environmental pollutant to disrupt endocrine system or cause cancer, thus the detection of BPA is very important. Herein, an amperometric sensor was fabricated based on immobilized CoTe quantum dots (CoTe QDs) and PAMAM dendrimer (PAMAM) onto glassy carbon electrode (GCE) surface. The cyclic voltammogram of BPA on the sensor exhibited a well-defined anodic peak at 0.490 V in 0.1 M pH 8.0 PBS. The determination conditions were optimized and the kinetic parameters were calculated. The linear range was 1.3 x 10^-8 to 9.89 x 10^-6 M with the correlation coefficient of 0.9999. The limit of detection was estimated to be 1 x 10^-9 M. The current reached the steady-state current within about 5 s. Furthermore, the fabricated sensor was successfully applied to determine BPA in real water samples.