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Makoto Shimizu, Nayuta Takemori, Daniel Guterding, Harald O Jeschke
Among iron chalcogenide superconductors, FeS can be viewed as a simple, highly compressed relative of FeSe without a nematic phase and with weaker electronic correlations. Under pressure, however, the superconductivity of stoichiometric FeS disappears and reappears, forming two domes. We perform electronic structure and spin fluctuation theory calculations for tetragonal FeS in order to analyze the nature of the superconducting order parameter. In the random phase approximation, we find a gap function with d-wave symmetry at ambient pressure, in agreement with several reports of a nodal superconducting order parameter in FeS...
September 28, 2018: Physical Review Letters
Ganghua Zhang, Jianwu Cao, Cheng Zhao, Binghui Han, Chongxian Ma, Zhipeng Gao, Tao Zeng
Layered transition-metal chalcogenides have attracted great interest due to their unique electronic and optical properties. Here, we represent two layered quaternary chalcogenides K2CoCu3S4 and K2CoCu3Se4 prepared by a convenient hydrothermal route. From powder XRD and TEM analyses, K2CoCu3Q4 possesses a tetragonal ThCr2Si2-type structure with a random arrangement of Co and Cu atoms. The phase purity of the samples was confirmed by ICP, SEM, and EDS analyses, and the oxidation states of Co and Cu atoms were determined to be +3 and +1 by XPS spectra...
October 9, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Daniele Benetti, Daling Cui, Haiguang Zhao, Federico Rosei, Alberto Vomiero
Metal chalcogenide quantum dots (QDs) are among the most promising materials as light harvesters in all-inorganic systems for applications in solar cells and production of solar fuels. The electronic band structure of composite QDs formed by lead and cadmium chalcogenides directly grafted on highly oriented pyrolytic graphite surfaces through successive ionic layer absorption and reaction is investigated. Atomic force microscopy and Kelvin probe force microscopy (KPFM) are applied to investigate PbS, CdS, and PbS/CdS QD systems...
October 7, 2018: Small
Sukanya Ramaraj, Mani Sakthivel, Shen-Ming Chen, Kuo-Chuan Ho
Metal chalcogenides with large active sites have been received great attention as an excellent catalyst due to their hierarchical structural properties. Here, we have demonstrated the synthesis of ytterbium-doped molybdenum selenide (YbMoSe2 ) in the form of two-dimensional nanosheets by using a simple ultrasonic method. The formation of the crystal phase of prepared YbMoSe2 nanosheets was studied by using the selective characterization techniques. The reported HRTEM confirmed that the introduction of heterogeneous spin of Yb with MoSe2 creates the lattice distortion...
September 21, 2018: Ultrasonics Sonochemistry
Karthik Ramasamy, Pravin S Shinde, Nariman Naghibolashrafi, Shanlin Pan, Arunava Gupta
Quaternary MIMIIIMIVXVI4 (I-III-IV-VI4) chalcogenides obtained by cross-substitution of binary and ternary compounds remain relatively unexplored. We have for the first-time synthesized wurtzite and defect chalcopyrite phases of CuMSnS4 (M = In or Ga) in the form of nanocrystals. Optical measurements show that the CuMSnS4 (M = In or Ga) nanocrystals exhibit strong visible light absorption with band gap values between 1.15 and 1.4 eV, suitable for solar energy conversion applications.
October 16, 2018: Chemical Communications: Chem Comm
Lei Wang, Wang Ren, Jing Wen, Bangshu Xiong
Phase-change electrical probe memory has recently attained considerable attention owing to its profound potential for next-generation mass and archival storage devices. To encourage more talented researchers to enter this field and thereby advance this technology, this paper first introduces approaches to induce the phase transformation of chalcogenide alloy by probe tip, considered as the root of phase-change electrical probe memory. Subsequently the design rule of an optimized architecture of phase-change electrical probe memory is proposed based on a previously developed electrothermal and phase kinetic model, followed by a summary of the state-of-the-art phase-change electrical probe memory and an outlook for its future prospects...
September 29, 2018: Nanomaterials
Nurmemet Abdukerim, Imtiaz Alamgir, Martin Rochette
We report, to the best of our knowledge, the first all-fiber frequency-resolved optical gating (FROG) device based on cross-phase modulation in chalcogenide glass. The amplitude and phase of pulses as short as 390 fs at femtojoule energy levels are accurately characterized without direction-of-time ambiguity in the retrieved pulse. A measurement sensitivity of 18  mW2 is achieved from the strong nonlinearity of a 10 cm long chalcogenide microwire.
October 1, 2018: Optics Letters
Masoud Aryanpour, Nassim Rafiefard, Seyed Hossein Hosseini-Shokouh, Somayeh Fardindoost, Azam Iraji Zad
Titanium trisulfide (TiS3), a transition metal chalcogenide, bears the potential to replace silicon, when taking the form of nanoflakes, due to its favorable band gap and optical response. In this paper, we investigate the response of TiS3 nanoflakes to gas detection through a careful quantum computational approach and a few succinct measurements. The computations are benchmarked and compared with a relevant experiment at each step, where their results/conclusions are discussed. The most stable surface of TiS3 particles is determined as (001), in agreement with the literature...
October 10, 2018: Physical Chemistry Chemical Physics: PCCP
Anne C Berends, Johannes D Meeldijk, Marijn A van Huis, Celso de Mello Donega
Colloidal 2D semiconductor nanosheets (NSs) are an interesting new class of materials due to their unique properties. However, synthesis of these NSs is challenging, and synthesis procedures for materials other than the well-known Pb- and Cd-chalcogenides are still underdeveloped. In this paper, we present a new approach to make copper indium sulfide (CIS) NSs and study their structural and optical properties. The CIS NSs form via self-organization and oriented attachment of 2.5 nm chalcopyrite CuInS2 nanocrystals (NCs), yielding triangular- and hexagonal-shaped NSs with a thickness of ∼3 nm and lateral dimensions ranging from 20 to 1000 nm...
December 26, 2017: Chemistry of Materials: a Publication of the American Chemical Society
Dominik Floess, Harald Giessen
The Faraday effect describes the phenomenon that a magnetized material can alter the polarization state of transmitted light. Interestingly, unlike most light-matter interactions in nature, it breaks Lorentz reciprocity. This exceptional behavior is utilized for applications such as optical isolators, which are core elements in communication and laser systems. While there is high demand for sub-micron nonreciprocal photonic devices, the realization of such systems is extremely challenging as conventional magneto-optic materials only provide weak magneto-optic response within small volumes...
October 1, 2018: Reports on Progress in Physics
Shalini Singh, Renu Tomar, Stephanie Ten Brinck, Jonathan De Roo, Pieter Geiregat, José C Martins, Ivan Infante, Zeger Hens
While the surface termination of quasi-spherical metal chalcogenide nanocrystals or quantum dots has been widely investigated, it remains unclear whether the ensuing surface chemistry models apply to similar nanocrystals with anisotropic shapes. In this work, we report on the surface-chemistry of 2D CdSe nanoplatelets, where we make use of an improved synthesis strategy that yields stable and aggregation free nanoplatelet suspensions with a photoluminescence quantum yield as high as 55%. We confirm that such nanoplatelets are enriched in Cd and, by means of 1 H nuclear magnetic resonance spectroscopy, we show that the Cd-rich surface is terminated by X-type carboxylate ligands...
October 5, 2018: Journal of the American Chemical Society
Jin Miao, Xiaohai Niu, Juan Jiang, Rui Peng, Binping Xie, Fei Chen, Haichao Xu, Donglai Feng
Surface potassium dosing has been proven to be an effective method in tuning the electron doping and enhancing the superconducting transition temperatures in both iron chalcogenides and electron doped iron pnictides. However, it is not clear how surface potassium dosing affects the hole doping and superconductivity in hole doped Fe-based superconductors. Here we performed K-dosing on Ba0.5 K0.5 Fe2 As2 , a prototypical hole-doped iron pnictide compound, and explored the electronic structure by in situ angle-resolved photoemission spectroscopy measurements...
September 25, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Wenzhou Chen, Xianhua Hou, Xingqiang Shi, Hui Pan
The fast development of high-performance devices for diverse applications requires nanoscale materials with multifunctional properties, motivating theoretical exploration into novel two-dimensional (2D) materials. In this work, we propose a new family of 2D nanomaterials, Janus transition metal oxides and chalcogenides MXY (M = Ti, Zr, or Hf; X = S or Se; Y = O or S; X ≠ Y) monolayers, for their versatile applications. We find that the Janus MXY monolayers are semiconductors with a wide range of band gaps ranging from 0...
October 4, 2018: ACS Applied Materials & Interfaces
Ignacio A Fernández-Coppel, Pablo Martín-Ramos, Jesús Martín-Gil, Ramón Pamies, Manuel Avella, María Dolores Avilés
Molybdenum chalcogenides present interesting properties beyond their superconducting critical temperatures and upper critical magnetic fields, making them suitable for potential applications in tribology, batteries, catalysis, or thermopower. In this study, Mo15 S19 nanoparticles with an average diameter of 10 nm were synthesized via the reaction of ammonium molybdate with hydrochloric acid and elemental sulfur as reducers at 245 °C. The oxidation to MoO₃ in air was efficiently avoided by using linseed oil as a reaction medium and dispersant...
September 19, 2018: Materials
Huajun Yang, Min Luo, Zhou Wu, Wei Wang, Chaozhuang Xue, Tao Wu
We demonstrated here a novel semiconducting metal-chalcogenide-organic framework (MCOF-89) with an optical bandgap through the unlikely assembly between a metal chalcogenide unit and carboxylic acid. The elusive metal-chalcogenide unit [Mn4 (μ4 -S)] with square-planar tetra-coordinated sulfur (sptS) is for the first time observed in MOFs.
October 14, 2018: Chemical Communications: Chem Comm
Subhajit Roychowdhury, Tanmoy Ghosh, Raagya Arora, Umesh V Waghmare, Kanishka Biswas
n-type Ge-chalcogenides with promising thermoelectric performance is urgently needed to match their p-type counterparts. However, their realization remains elusive due to intrinsic Ge vacancies which make them p-type semiconductors. GeSe crystallizes into a layered orthorhombic structure similar to the SnSe at ambient conditions. High symmetry cubic phase of GeSe is predicted to be stabilized either by applying external pressure of 7 GPa or by enhancing the entropy via increasing the temperature to 920 K. Herein, we report the stabilization of n-type cubic phase of GeSe at ambient conditions by alloying with AgBiSe2 (30-50 mol %), which enhances the entropy through solid solution mixing...
September 17, 2018: Angewandte Chemie
Moumita Rana, Sanjit Mondal, Lipipuspa Sahoo, Kaustav Chatterjee, Pitchiah E Karthik, Ujjal K Gautam
Water-based renewable energy cycle involved in water splitting, fuel cells, and metal-air batteries has been gaining increasing attention for sustainable generation and storage of energy. The major challenges in these technologies arise due to the poor kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reactions (OER), besides the high cost of the catalysts. Attempts to address these issues have led to the development of many novel and inexpensive catalysts as well as newer mechanistic insights, particularly so in the last three-four years when more catalysts have been investigated than ever before...
October 10, 2018: ACS Applied Materials & Interfaces
Sebastiano Bellani, Maria Rosa Antognazza, Francesco Bonaccorso
Hydrogen is considered a promising environmentally friendly energy carrier for replacing traditional fossil fuels. In this context, photoelectrochemical cells effectively convert solar energy directly to H2 fuel by water photoelectrolysis, thereby monolitically combining the functions of both light harvesting and electrolysis. In such devices, photocathodes and photoanodes carry out the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. Here, the focus is on photocathodes for HER, traditionally based on metal oxides, III-V group and II-VI group semiconductors, silicon, and copper-based chalcogenides as photoactive material...
September 16, 2018: Advanced Materials
Ailong Li, Yimeng Sun, Tingting Yao, Hongxian Han
Fundamentals of water electrolysis, and recent research progresses and trends in the development of earth-abundant first row transition metal (Mn, Fe, Co, Ni, Cu) based oxygen evolution reaction (OER) and hydrogen evolution (HER) electrocatalysts working in acidic, alkaline or neutral conditions are reviewed. The HER catalysts include mainly metal chalcogenides, metal phosphides, metal nitrides, and metal carbides. As for the OER catalysts, the basic principles of the OER catalysts in alkaline, acidic and neutral media are introduced, followed by the review and discussion of the Ni, Co, Fe, Mn, and perovskite type OER catalysts developed so far...
September 9, 2018: Chemistry: a European Journal
A Kandemir, F M Peeters, H Sahin
Using first principles calculations, we study the structural and phononic properties of the recently synthesized Janus type single layers of molybdenum dichalcogenides. The Janus MoSSe single layer possesses 2H crystal structure with two different chalcogenide sides that lead to out-of-plane anisotropy. By virtue of the asymmetric structure of the ultra-thin Janus type crystal, we induced the out-of-plane anisotropy to show the distinctive vertical pressure effect on the vibrational properties of the Janus material...
August 28, 2018: Journal of Chemical Physics
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