Ternary Transition Metal Chalcogenides Research Articles

One-dimensional van der Waals stacked p-type crystal Ta2Pt3Se8 for nanoscale electronics.

Recently, ternary transition metal chalcogenides Ta2X3Se8 (X = Pd or Pt) have attracted great interest as a class of emerging one-dimensional (1D) van der Waals (vdW) materials. In particular, Ta2Pd3Se8 has been actively studied owing to its excellent charge transport properties as an n-type semiconductor and ultralong ballistic phonon transport properties. Compared to subsequent studies on the Pd-containing material, Ta2Pt3Se8, another member of this class of materials has been considerably less explored despite its promising electrical properties as a p-type semiconductor. Herein, we demonstrate the electrical properties of Ta2Pt3Se8 as a promising channel material for nanoelectronic applications. High-quality bulk Ta2Pt3Se8 single crystals were successfully synthesized by a one-step vapor transport reaction. Scanning Kelvin probe microscopy measurements were used to investigate the surface potential difference and work function of the Ta2Pt3Se8 nanoribbons of various thicknesses. Field-effect transistors fabricated on exfoliated Ta2Pt3Se8 nanoribbons exhibited moderate p-type transport properties with a maximum hole mobility of 5 cm2 V-1 s-1 and an Ion/Ioff ratio of >104. Furthermore, the charge transport mechanism of Ta2Pt3Se8 was analyzed by temperature-dependent transport measurements in the temperature range from 90 to 320 K. To include Ta2Pt3Se8 in a building block for modern 1D electronics, we demonstrate p-n junction characteristics using the electron beam doping method.

Band gap engineering of monolayer ZrGeTe4 via strain: A first-principles study

Modulating the bandgap of two-dimensional (2D) semiconductors is of particular importance for electronics, optoelectronics, and sensors applications in the nanoscale. Here, based on first-principles calculations, we report the modulation of electronic, mechanical, and optical properties of a ternary transition metal chalcogenide ZrGeTe4 monolayer with the applied external strain. The perfect 2D ZrGeTe4 crystal is a semiconductor with a direct bandgap of 1.21 eV, exhibiting anisotropic elastic and optical response. Both external compression and tensile strain can reduce its bandgap linearly, resulting in the modulation of its optical absorption edge. In particular, a semiconductor-to-metal transition observed in ZrGeTe4 monolayer under a compression strain. The flexibility and significantly strain-tunable electronics properties in 2D ZrGeTe4 monolayer render its great potential in the nanoscale electronic and optoelectronic applications.

Dye-sensitized photocatalytic hydrogen evolution by using copper-based ternary refractory metal chalcogenides

The exploration of photocatalytic transformation of solar energy into H2 through water splitting is an important direction towards sustainable and non-polluting energy in order to cover energy necessity partially. Ternary transition metal chalcogenides have been attracted attention among the other chalcogenides due to their potential applications in the photocatalytic and electrocatalytic hydrogen evolution. Herein, Cu2WS4 nanocubes and Cu2WSe4 nanosheets have been synthesized through a facile hot-injection method to benefit from the advantages such as minimizing the required pressure and reaction time by this technique. The photocatalytic hydrogen evolution activities of Cu2WS4 and Cu2WSe4 have been investigated under the visible light irradiation by using eosin-Y (EY) dye and triethanolamine (TEOA) as a photosensitizer and an electron donor, respectively. Cu2WS4 nanocubes have exhibited higher photocatalytic activity and stability than Cu2WSe4 nanosheets. The photocatalytic HER rates of Cu2WS4 and Cu2WSe4 have been determined as 1260 μmol g−1 h−1 and 861 μmol g−1 h−1, respectively. Photocatalytic HER activities were figured out in the order of Cu2WS4 > Cu2WSe4 which could be attributed to differences between proton reduction potential and the conduction band energy levels.

Dark and illuminated electrical characteristics of Si-based photodiode interlayered with CuCo5S8 nanocrystals

Derived from the traditional dichalcogenide CuS structure, ternary transition metal chalcogenide nanoparticles in the form of CuCo5S8 are investigated under the aim of photodiode application. In addition to the detailed analysis on material characteristics of CuCo5S8 thin-film layer, the work is focused on the electrical characteristics of Au/CuCo5S8/Si diode to investigate its current–voltage, capacitance–voltage, and conductance–voltage characteristics under dark and illuminated conditions. CuCo5S8 nanocrystals with an average size of 5 nm are obtained using hot-injection method, and they are used to form thin-film interfacial layer between metal (Au) and semiconductor (Si). Under dark conditions, the diodes show about four orders in magnitude rectification rate and diode illumination results in efficient rectification with increase in intensity. The analysis of current–voltage curve results in non-ideal diode characteristics according to the thermionic emission model due to the existence of series resistances and interface states with interface layer. The measured current–voltage values are used to extract the main diode parameters under dark and illumination conditions. Under illumination, photogenerated carriers contribute to the current flow and linear photoconductivity behavior in photocurrent measurements with illumination shows the possible use of CuCo5S8 layer in Si-based photodiodes. This characteristic is also observed from the typical on/off illumination switching behavior for the photodiodes in transient photocurrent, photocapacitance, and photoconductance measurements with a quick response to the illumination. The deviations from ideality are also discussed by means of distribution of interface states and series resistance depending on the applied frequency and bias voltage.

Amorphous CoMoS4 Nanostructure for Photocatalytic H2 Generation, Nitrophenol Reduction, and Methylene Blue Adsorption

High-performance ternary transition-metal chalcogenides (TMDs) are desired in various application fields. However, developing ternary TMDs with unique performance via an efficient and economical me...

Ternary transition metal chalcogenides decorated on rGO as an efficient nanocatalyst towards urea electro-oxidation reaction for biofuel cell application

A ternary transition metal chalcogenide, containing MoS2, NiS, and Co3S4 (MCNS), and MCNS/reduced graphene oxide (MCNS/rGO) composite were prepared as anode catalysts by a simple hydrothermal process for Urea electro-oxidation. It's expected that rGO with high specific surface area provides superior catalytic performance for MCNS/rGO than MCNS. Also, the synergic effect of Mo, Ni, and Co in the composite accelerates the urea oxidation and enhances the performance of the catalyst. The composites were characterized by field emission electron microscopy, transition electron microscopy, and X-ray diffraction spectroscopy. Electrochemical properties of composites were evaluated by cyclic voltammetry. The MCNS/rGO demonstrated superior electrocatalytic performance than the MCNS catalyst. The incorporating of rGO into MCNS creates a high electrochemical surface area for urea electro-oxidation that resulted in a higher current density (18 mA cm−2) than MCNS (3.7 mA cm−2) at the presence of 0.6 M urea and the scan rate of 20 mV s−1. The maximum current density obtained 43 mA cm−2 for MCNS/rGO at the scan rate of 70 mV s−1 in room temperature. Also, single cells based on MCNS and MCNS/rGO supplied a maximum power density of 7.7 mW cm−2 and 21.0 mW cm−2 at room temperature, respectively. Hence, MCNS/rGO can be a favorable electrocatalyst for application in the direct urea fuel cell.

Cu–Fe–Se Ternary Nanosheet-Based Drug Delivery Carrier for Multimodal Imaging and Combined Chemo/Photothermal Therapy of Cancer

Ternary transition-metal chalcogenide nanosheets have shown great potential in diverse applications owing to their intrinsically amazing properties with a broad tunable window. Direct preparation of water-soluble and biocompatible ternary chalcogenide nanosheets for theranostic application remains a challenge. In this article, we prepared Cu-Fe-Se nanosheets (CFS NSs) in an aqueous solution under ambient conditions by a sequential coprecipitation method. They were functionalized with anticancer drug doxorubin (CFS@DOX) through electrostatic interactions and labeled with radioactive isotope 99mTc through surface coordination effect. The resulting nanosheets have a size of 70 nm and a thickness of 5 nm, and can be well dispersed in water, phosphate-buffered saline, 10% fetal bovine serum, and 0.9% NaCl with an excellent colloidal stability. They also exhibit a high photothermal conversion efficiency of 78.9% for in vitro and in vivo photoacoustic imaging and photothermal therapy. The isotope-labeled nanosheets (99mTc-CFS NSs) were used for single photon emission computed tomography/computed tomography imaging to quantify their blood circulation time (∼4.7 h) and biodistributions in major organs, which follow an order of liver > bladder > lung > spleen > heart > kidney. The DOX-functionalized nanosheets (CFS@DOX) were used for chemotherapy of cancer and exhibited excellent anticancer efficacy. Our research shows the great promise of ternary metal chalcogenide nanosheets for combined imaging and therapy of cancer.

Layered Ternary and Quaternary Transition Metal Chalcogenide Based Catalysts for Water Splitting

Water splitting plays an important role in the electrochemical and photoelectrochemical conversion of energy devices. Electrochemical water splitting by the hydrogen evolution reaction (HER) is a straightforward route to producing hydrogen (H2), which requires an efficient electrocatalyst to minimize energy consumption. Recent advances have created a rapid rise in new electrocatalysts, particularly those based on non-precious metals. In this review, we present a comprehensive overview of the recent developments of ternary and quaternary 6d-group transition metal chalcogenides (TMCs) based electrocatalysts for water splitting, especially for HER. Detailed discussion is organized from binary to quaternary TMCs including, surface engineering, heterostructures, chalcogen substitutions and hierarchically structural design in TMCs. Moreover, emphasis is placed on future research scope and important challenges facing these electrocatalysts for further development in their performance towards water splitting.

(Invited) Theory and Device Concepts of Novel Electronic, Optoelectronic, and Topological 2D Materials

2D materials provide extraordinary materials platform with many interesting physical properties distinct from their bulk counterpart and offer unprecedented opportunities for ultrathin electronic and optical applications. Here I will present our recent theoretical works on novel 2D multiferroics and 2D topological materials as well as a few device concepts. First, I will highlight our discoveries on 2D topological materials including binary and ternary transition metal dichalcogenides etc. Our works show that electric field, elastic strain, and van der Waals stacking can be utilized to introduce topological phase transition [1,2]. In particular, the electric field induced topological phase transition offers a possibility for realizing topological field effect transistor, which will be fundamentally different from conventional transistors. In the second example, I will introduce the discovery of 2D multiferroics in semiconducting group IV monochalcogenide monolayers [3]. These 2D materials exhibit giant spontaneous ferroelastic lattice strain and ferroelectric polarization. Both are strongly coupled, accompanied with large anisotropic 2D excitonic responses and nonlinear optical responses [4]. Our theoretical findings indicate that these multiferroic 2D materials possess low domain wall energy and migration barrier, suggesting great opportunities for multifunctional opto-electronic-mechanical devices such as 2D ferroelectric and ferroelastic memory and 2D ferroelectric excitonic photovoltaics. Finally, relevant experimental progresses as well as some critical challenges and opportunities in 2D materials and their nanostructures will be discussed. 1. Xiaofeng Qian, Junwei Liu, Liang Fu, and Ju Li. Quantum spin Hall effect in two-dimensional transition metal dichalcogenides. Science 346, 1344-1347 (2014). 2. Junwei Liu, Hua Wang, Chen Fang, Liang Fu, and Xiaofeng Qian. van der Waals Stacking-Induced Topological Phase Transition in Layered Ternary Transition Metal Chalcogenides. Nano Letters 17, 467-475 (2017). 3. Hua Wang and Xiaofeng Qian. Two-dimensional multiferroics in monolayer group IV monochalcogenides. 2D Materials 4, 015042 (2017). 4. Hua Wang and Xiaofeng Qian. Giant Optical Second Harmonic Generation in Two-Dimensional Multiferroics. Nano Letters 17, 5027-5034 (2017).

Direct transition of a HfGeTe4 ternary transition-metal chalcogenide monolayer with a zigzag van der Waals gap

The ternary transition-metal chalcogenide HfGeTe4 is found to have a direct band gap of around 1.3 eV in its monolayer form, while it has an indirect band gap of about a half of that value in the bulk form. In contrast to the two-dimensional flat layers seen in most van der Waals solids, HfGeTe4 has zigzag shaped layers. The zigzag shape can allow a higher inter-layer cohesive energy and thus lead to better adhesion properties. The discovery of this novel transition metal ternary chalcogenide will open new avenue of materials exploration for future ultrathin electronics applications.

Structural and Optical Properties of Nickel Sulfoselenide (NiSSe) Thin Film for Photoelectrochemical Applications

The transition metal, nickel is a favourable material to create combination with chalcogenides elements (S, Se and Te) to become either binary or ternary transition metal chalcogenide such NiSe2, NiSe, NiS2 and Ni3Se. Throughout some observation from the previous research regarding the synthesis of ternary transition metal chalcogenide thin film for photoelectrochemical application, the combination of nickel with two chalcogenide elements; S and Se are rarely found due to the nature of selenium and sulphur. In this work, NiSSe thin film is being synthesis onto indium tin oxide (ITO) glass substrates using electrodeposition technique and the structural and optical properties of the films are studied. The resulted thin films are characterized using X-ray diffraction analysis and scanning electron microscope to determine the crystallographic and morphological properties. Optical are also being analysed for their bandgap values in other to determine the suitability of NiSSe thin film for photoelectrochemical properties. Results proved that nickel sulfoselenide thin films are polycrystalline in nature with a good uniformity. The intersection point for the optical analysis gave the direct bandgap. Well-adherent and dark-coloured thin films are derived from the cathodically electrodeposition by using potential in the reduction region. Experimental results proved NiSSe thin films are capable to be used in photoelectrochemical cell application.

Activation of Ternary Transition Metal Chalcogenide Basal Planes through Chemical Strain for the Hydrogen Evolution Reaction.

Catalytically inactive basal planes pose challenges for the efficient hydrogen evolution reaction (HER) in two-dimensional (2 D) transition metal chalcogenide (TMC) nanosheets. Herein, a new hybrid structure is reported in which zero-dimensional TMC nanodots (NDs) are decorated on the basal planes of 2 D nanosheets of TMCs to enhance their catalytic activity towards the HER process. A novel process is developed to fabricate a hybrid Cu2 MoS4 (2 D ternary transition metal chalcogenide Cu2 MoS4 nanosheets)/MoSe2 (0 D binary transition metal chalcogenide MoSe2 ND) nanostructure by controlling the size of the MoSe2 NDs to enhance the HER activity. In acidic media, this optimal hybrid Cu2 MoS4 /MoSe2 nanostructure achieves excellent catalytic activity for HER, which exhibits a low overpotential of 166 mV at a current density of 10 mA cm-2 , which corresponds to a Tafel slope of 74.7 mV dec-1 . In addition, the synthesized hybrid nanostructure shows excellent stability when under acidic medium for 16 h of continuous electrolysis. Therefore, it is suggested that our strategy may open a new path for the design of hybrid nanostructures by using ternary transition metal chalcogenides (TTMCs) with binary transition metal chalcogenides (BTMCs) for alternative non-noble metal catalysts towards HER.

Manifestations of Quasi-Two-Dimensional Metallicity in a Layered Ternary Transition Metal Chalcogenide Ti2PTe2

Quasi-two-dimensional (2D) metallicity in a ternary layered transition metal chalcogenide of single crystalline Ti2PTe2 is studied by transport prop-erties measurements and electronic structure analyses. The logarithmic dependence of resistivity in the low temperature region appears as a charac-teristic feature of the quasi-2D transport in a weakly disordered metallic system. A large Sommerfeld coefficient value of 6.94 mJ/mol·K2 and negative temperature dependence of the Hall coefficient indicate that electron-electron interaction is dominant in a phase-breaking mechanism originating from bipolar behavior. Angle-resolved photoemission spectroscopy combined with theoretical calculations successfully proves that quasi-2D elec-tron pockets encompassing a small three-dimensional hole pocket mainly determine the quasi-2D metallic transport properties. We also adopt an orbital character calculation to verify that Ti character is dominant in valence bands, revealing that 2D Ti-networks form quasi-2D conducting ...

Highly active and stable layered ternary transition metal chalcogenide for hydrogen evolution reaction

Layered ternary transition metal chalcogenides (TTMCs) material has great potentials that can overcome to the limitation of active sites which is challenging in binary transition metal chalcogenides (BTMC), such as MoS2, towards electrochemical hydrogen production. Here, we demonstrate TTMC material which contains two transition metals Cu and Mo with chalcogen S. The TTMC, Cu2MoS4 has been successfully synthesized by a facile solution-processed method. Moreover, by anion doping such as Se in as the synthesized Cu2MoS4, it has been found that TTMC can be exfoliated into single layer nanosheets. Furthermore, by controlling the number of layers, single layers TTMC exhibit the highest electrocatalytic activity towards hydrogen evolution reaction (HER) because the single layers can provide more catalytic active sites than multilayers and bulk. The onset potential for hydrogen generation is −96mV for single layer TTMC electrode material with corresponding Tafel slope 52mV/decade. After 1000 cycles with continuous electrolysis in acid electrolyte for 15h, the electrode material preserves its structure and robust catalytic activity perfectly. Our new TTMC materials show highly active electrocatalytic performance and high stability which overcome the intrinsic limitation of BTMC. As a result, our work can guide new strategy for the developments of real applications of TMCs in HER.

Drumhead surface states and topological nodal-line fermions inTlTaSe2

A topological nodal-line semimetal is a state of matter with one-dimensional bulk nodal lines and two-dimensional so-called drumhead surface bands. Based on first-principles calculations and an effective $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ model, we theoretically propose the existence of topological nodal-line fermions in the ternary transition-metal chalcogenide ${\mathrm{TlTaSe}}_{2}$. The noncentrosymmetric structure and strong spin-orbit coupling give rise to spinful nodal-line bulk states which are protected by a mirror reflection symmetry of this compound. This is remarkably distinguished from other proposed nodal-line semimetals such as ${\mathrm{Cu}}_{3}\mathrm{NPb}$(Zn) in which the nodal line exists only in the limit of vanishing spin-orbit coupling and thus is not as robust. In addition, we show that the drumhead surface states in ${\mathrm{TlTaSe}}_{2}$, which are associated with the topological nodal lines, exhibit an unconventional chiral spin texture and an exotic Lifshitz transition as a consequence of the linkage among multiple drumhead surface-state pockets.

Enhanced electron coherence in atomically thin Nb3SiTe6

The extraordinary properties of two dimensional (2D) materials, such as the extremely high carrier mobility in graphene and the large direct band gaps in transition metal dichalcogenides MX2 (M = Mo or W, X = S, Se) monolayers, highlight the crucial role quantum confinement can have in producing a wide spectrum of technologically important electronic properties. Currently one of the highest priorities in the field is to search for new 2D crystalline systems with structural and electronic properties that can be exploited for device development. In this letter, we report on the unusual quantum transport properties of the 2D ternary transition metal chalcogenide - Nb3SiTe6. We show that the micaceous nature of Nb3SiTe6 allows it to be thinned down to one-unit-cell thick 2D crystals using microexfoliation technique. When the thickness of Nb3SiTe6 crystal is reduced below a few unit-cells thickness, we observed an unexpected, enhanced weak-antilocalization signature in magnetotransport. This finding provides solid evidence for the long-predicted suppression of electron-phonon interaction caused by the crossover of phonon spectrum from 3D to 2D.

Characterization of magnetism and electronic properties of a ternary transition metal chalcogenide Rb 2Ni 3S 4

The process of preparing specimens of Rb 2Ni 3S 4 single crystals grown by the flux method was reconsidered to clarify the magnetic and electronic properties of this nickel sulfide. Specimens obtained by removing fluxes with water were confirmed to have a residual ferromagnetic moment, as previously reported by the present authors. Specimens peeled a surface of as-grown crystals off by taking advantage of the quadratic layer characteristic of this crystal were ascertained to be diamagnetic and to exhibit magnetic properties intrinsic to Rb 2Ni 3S 4. However, the temperature dependence of the specific resistivity of the latter sample is similar to that of the former. Through examination of the experimental results, Rb 2Ni 3S 4 was identified as a nonmagnetic semiconductor in a low spin 3d 8 configuration of Ni 2+.

Reinvestigation of magnetism and electric transport in a ternary transition metal chalcogenide Rb 2Ni 3S 4

The process of preparing specimens of Rb 2Ni 3S 4 single crystals grown by the flux method was reconsidered to clarify the magnetic and electronic properties of this nickel sulfide. Specimens obtained by removing fluxes with water were confirmed to have a residual ferromagnetic moment, as previously reported by the present authors. Specimens peeled a surface of as-grown crystals off by taking advantage of the quadratic layer characteristic of this crystal were ascertained to be diamagnetic and to exhibit magnetic properties intrinsic to Rb 2Ni 3S 4. However, the temperature dependence of the specific resistivity of the latter sample is similar to that of the former. Raman scattering measurement indicated that this system undergoes no structural phase transition. Magnetic measurements in Co-doped specimens were carried out to obtain further information on the host substance. The appropriate band structure of Rb 2Ni 3S 4 was calculated in terms of the full-potential linearized augmented plane-wave method in the local density approximation to understand the electronic properties of Rb 2Ni 3S 4. Through examination of the experimental results and the obtained band structure, Rb 2Ni 3S 4 was identified as a non-magnetic semiconductor in a low spin 3d 8 configuration of Ni 2+.

Chemical reactivity of the [Nb2S11]4− anion: selective substitution of sulfur by selenium on a molecular level

Abstract Reaction of the ternary transition metal chalcogenide K 4 Nb 2 S 11 with K 2 Se 5 leads to the formation of the new mixed sulfur selenium compound K 4 Nb 2 S 8.9 Se 2.1 . Single crystal structure determination proves that the connectivity within the molecular [Nb 2 S 11 ] 4− anion remains intact but distinct sulfur positions are partially substituted by selenium. All S 2 2− anions are selectively exchanged by selenium whereas the S 2− anions are not affected. The refinement of the site occupation factors demonstrates that the two sulfur atoms in the S 2 2− anions were non-statistically substituted by the selenium atoms. Furthermore, the partial substitution of S by Se leads to a new structural type for compounds with general formula A 4 M 2 Q 11 (A=alkali metals, M=Nb, Ta, Q=S, Se). The direct synthesis using a S/Se mixture yields a second compound with composition K 4 Nb 2 S 9.5 Se 1.5 showing an exchange pattern within the S 2 2− anions being slightly different from that found in K 4 Nb 2 S 8.9 Se 2.1 .

Evidences for the Formation of Chromium in the Unusual Oxidation State Cr(IV): I. Chemical Reactivity, Microhomogeneity, and Crystal Structures of the Nonstoichiometric Channel Compounds TlxCr5Se8(0 ≤x≤ 1)

The topotactic redox reaction between TlCr5Se8and bromine in acetonitrile leads to the formation of metastable samples with 0 ≤x< 1 of TlxCr5Se8. Preparation at elevated temperatures yields for the first time a ternary transition metal chalcogenide crystallizing in the TlV5S8type structure with a Tl contentx< 0.33. As expected the topotactic redox reaction does not follow simple kinetics but is rather explained on the basis of the superposition of at least three different fundamental steps. EDAX investigations conducted on selected single crystals reveal that dependent on the deintercalation temperature, Tl is laterally inhomogeneous distributed along the needle axis which coincides with the crystallographicbaxis. A pronounced maximum is observed at the middle of the crystals. In stoichiometric TlCr5Se8the detailed analysis of the anisotropic displacement parameters of the Tl atoms reveal that the Tl atoms are displaced from the central position by about 0.26 Å. As a consequence the Tl atoms are coordinated by seven Se atoms in an irregular coordination polyhedron. Since the positionsx0zare related by a center of symmetry they cannot be occupied simultaneously. Hence it must be assumed that TlCr5Se8has a domain structure with local symmetryCm. In the Tl poorer phases the refinement of the Tl atoms at the central position leads to unusual highU22components. The observed microinhomogenity as well as an enhanced mobility and/or static disorder of the Tl atom within the channel may be responsible for this. The value forU11decreases with decreasing Tl content whereasU33is not affected. This observation is indicative for a different displacement of the Tl atoms from the central position. With respect to the possible reaction mechanisms, according to our structural investigations, the oxidation of monovalent Tl to trivalent Tl can be excluded. With decreasing Tl content the lattice parameters exhibit very anisotropic behavior, which is a direct consequence of the large changes of the interatomic Cr–Cr distances. The average 〈Cr–Se〉 as well as the nonbonding Se–Se distances are only slightly affected. These results suggest an oxidation of the formally trivalent Cr to the unusual tetravalent state Cr(IV), rather than the formation of valence band holes.