Se Nanosheets Research Articles

Alloy engineered cryotronically stable polymorphic strained photo detector functionalized by palladium enriched tin diselenide nanosheets

Scientists experience formidability in developing an advanced materials capable to withstand extreme environmental circumstances without sacrificing its fundamental properties. In this realm, solid-state devices utilizing 'metal dichalcogenide' materials offer significant advantages for cryogenic purposes, but rarely explored. In this study, thin film photodetectors (TFPDs) based on meta-materials of PdxSn1−xSe2 (x=0.0, 0.2, 0.5) nanosheets are introduced. Nanosheets are extracted from bulk via sonochemical exfoliation to fabricate TFPDs. Novel material Pd0.5Sn0.5Se2 grown by 50 % palladium enrichment in SnSe2 exhibits polymorphism comprising structural duality of hexagonal-orthorhombic phases. TFPDs based on PdxSn1−xSe2 (x=0.0, 0.2, 0.5) nanosheets display substantial photoresponse in which TFPD functionalised by Pd0.5Sn0.5Se2 nanosheets portrays superior photodetection. Raman peak demonstrates notable thermal-sensing through blue-shifting and sharpening under cryogenic-temperatures. Surprisingly, Pd0.5Sn0.5Se2 nanosheets based TFPD reveals considerable photodetection, achieving 0.52 mAW−1 responsivity at 10 K cryogenic-temperature. To the best of our knowledge, present investigation surpasses previous reports, highlighting a thin film-based photo detector that represents exceptional responsivity at 10 K cryogenic-temperature reported by us for the first time. As an outcome of present study, a TFPD based on Pd0.5Sn0.5Se2 nanosheets emerges as advanced cryotronic material for designing next-generation cryogenic photonic devices due to its higher steadiness, excellent reproducibility and operational efficiency at cryogenic-temperature of 10 K.

Enhanced visible-light photocatalytic activity of direct Z-scheme g-C3N/MX2 (M = Mo, W and X = S, Se) nanosheets from theoretical insights

Since the discovery of graphene, two-dimensional (2D) layered materials have attracted extensive research interest. The synergistic effects of two different 2D semiconductors forming a heterostructure may enhance the intrinsic properties. Here, the photoelectric properties of g-C3N/MX2 (M = Mo, W and X = S, Se) heterostructures and the effect of their interface interaction on photocatalytic activity have been systematically studied. Different stacking structures of g-C3N/MX2 exhibit similar stability and electronic properties. g-C3N/MoS2 is metallic, while the other systems retain semiconductor properties. The interface dipole moment and work function confirm the intrinsic electric field direction from g-C3N to MX2, which reduces the coulomb interaction of carriers and promotes carrier separation. Moreover, the synergistic effect of the band offset and the intrinsic electric field induces the charge transfer to follow a direct Z-scheme in g-C3N/MoSe2, g-C3N/WS2, and g-C3N/WSe2, such that the conduction band (CB) of g-C3N becomes a reduction center and the valence band (VB) of MX2 becomes an oxidation center. Meanwhile, the hydrogen evolution reaction (HER) can occur in either acidic, alkaline, or neutral solutions, and g-C3N/WS2 has the smallest potential-determining step. The oxygen evolution reaction (OER) can occur in solutions at most pH levels, and g-C3N/WSe2 has the smallest potential-determining step. Electrons mainly migrating in the g-C3N layer have higher mobility, which facilitates the HER process. All three g-C3N/MX2 have similar light-absorption strengths, with the absorption edge being red-shifted compared to g-C3N or MX2. Therefore, heterostructure construction does indeed effectively improve the photoelectric performance and photocatalytic activity.

Bandgap regulation and doping modification of Ga2-x Cr x Se3 nanosheets.

Ga2Se3, an important direct wide bandgap semiconductor with excellent optoelectronic properties, has wide application potential in the fields of photodetectors, photoelectric sensors and solar cells. Herein, we describe the synthesis of Ga2Se3 semiconductor nanoparticles using a high temperature organic liquid phase method. Post-annealing treatment at different temperatures can not only improve the crystallinity of Ga2Se3 nanoparticles, but also regulate its optical band gap ranging from 2.50 to 2.80 eV. We further synthesized Ga2-x Cr x Se3 nanosheets by doping CrCl3·6H2O in the reaction process. By adjusting the Cr doping concentration, Ga2-x Cr x Se3 nanosheets can achieve a continuously tunable band gap in the range of 2.23 eV to 2.42 eV. Both Ga2-x Cr x Se3 nanosheets and Ga2Se3 nanoparticles exhibit excellent and stable photoelectric switching performance. With Cr doping, Ga2-x Cr x Se3 exhibits reduced Nyquist impedance and enhanced electrocatalytic activity, which is attributed to its ultrathin nanosheet morphology and large specific surface area. In addition, the diamagnetic behavior of pure Ga2Se3 changes to ferromagnetism with different Cr doping concentrations, and its magnetization is as high as 18.0 emu g-1 at x = 0.4. These findings demonstrate that Ga2-x Cr x Se3 nanosheets have significant potential in future optoelectronic and magnetoelectric applications.

Multi-layered heterogeneous interfaces created in Co0.85Se@Ni3S4/NF to enhance supercapacitor performances by multi-step alternating electrodeposition.

Heterogeneous interface construction is of far-reaching significance to optimize the electrochemical performance of electrodes. Herein, a multi-step alternating electrochemical deposition (MAED) method is proposed to alternately deposit Co0.85Se and Ni3S4 nanosheets on a nickel foam (NF), forming a special alternate layer-by-layer structure with multi-layered heterogeneous interfaces. The creation of the multi-layered heterogeneous interfaces provides a large interfacial area for redox reactions with optimum interstitials facilitating ion diffusion, thus greatly improving the electrochemical energy storage efficiency. With the increase in the layer number, the material exhibits increasingly better energy storage performance, and 8L-Co0.85Se@Ni3S4/NF exhibits the highest specific capacitances of 2508 F g-1 and 1558 F g-1 at a scan rate of 2 mV s-1 and a current density of 1 A g-1. The 8L-Co0.85Se@Ni3S4/NF//polypyrrole (PPy)/NF asymmetric supercapacitor provides a maximum operation potential window of 1.55 V and energy densities of 76.98 and 35.74 W h kg-1 when the power densities are 775.0 and 15 500 W kg-1, respectively, superior to most of the related materials reported. Through MAED, the deposited phase and the layer number can be accurately controlled, thus providing an efficient strategy for interface construction so as to increase the electrochemical activity of the energy storage materials.

Stability and electronic, phononic, thermal and optical properties of SrX (X = S, Se) nanosheets based on AIMD and DFT computations.

We study the electronic structure, stability, and thermal and optical properties of hexagonal SrS and SrSe monolayers using first-principles calculations. PBEsol generally improves the calculated equilibrium properties of solids and their surfaces, predicting a wider band gap of the monolayers, which is closer to the results obtained with HSE06. Phonon dispersion relations and the ab initio molecular dynamics (AIMD) method confirm the dynamic and thermal stability of both structures. The phonon modes of a SrSe monolayer are lower in energy than those of SrS, and the gap between the acoustic and optical modes is larger, leading to weaker thermal properties such as heat capacity. Additionally, both SrS and SrSe monolayers show an active optical response in the far-visible light region, with some differences in how they behave optically depending on the direction of polarization. SrS exhibits a slightly higher static dielectric constant than that of SrSe, and the primary optical conductivity also follows the same trend. Another important finding is that an SrS monolayer exhibits plasmonic excitations, but SrSe does not.

One-Step Solvothermal Synthesis of (Mn, In) (S, Se) Nanosheets with Porous Structure for Water Splitting Without Sacrificial Agents

One-Step Solvothermal Synthesis of (Mn, In) (S, Se) Nanosheets with Porous Structure for Water Splitting Without Sacrificial Agents

Cation Defect-Engineered Boost Fast Kinetics of Two-Dimensional Topological Bi2 Se3 Cathode for High-Performance Aqueous Zn-Ion Batteries.

The challenge with aqueous zinc-ion batteries (ZIBs) lies in finding suitable cathode materials that can provide high capacity and fast kinetics. Herein, two-dimensional topological Bi2 Se3 with acceptable Bi-vacancies for ZIBs cathode (Cu-Bi2-x Se3 ) is constructed through one-step hydrothermal process accompanied by Cu heteroatom introduction. The cation-deficient Cu-Bi2-x Se3 nanosheets (≈4nm) bring improved conductivity from large surface topological metal states contribution and enhanced bulk conductivity. Besides, the increased adsorption energy and reduced Zn2+ migration barrier demonstrated by density-functional theory (DFT) calculations illustrate the decreased Coulombic ion-lattice repulsion of Cu-Bi2-x Se3 . Therefore, Cu-Bi2-x Se3 exhibits both enhanced ion and electron transport capability, leading to more carrier reversible insertion proved by in situ synchrotron X-ray diffraction (SXRD). These features endow Cu-Bi2-x Se3 with sufficient specific capacity (320mAhg-1 at 0.1Ag-1 ), high-rate performance (97mAhg-1 at 10Ag-1 ), and reliable cycling stability (70mAhg-1 at 10Ag-1 after 4000 cycles). Furthermore, quasi-solid-state fiber-shaped ZIBs employing the Cu-Bi2-x Se3 cathode demonstrate respectable performance and superior flexibility even under high mass loading. This work implements a conceptually innovative strategy represented by cation defect design in topological insulator cathode for achieving high-performance battery electrochemistry.

Cactus-like (Ni,Co)Se2 nanosheets with 3D structure decorated on the conductive substrate for efficient hydrogen evolution reaction

Transition metal selenides are a fascinating class of substitute for traditional noble metal electrocatalysts for hydrogen evolution reaction (HER). However, the monometallic selenides still have the disadvantages of low electroactive sites and electrical conductivity. To address such drawbacks, three-dimensional (3D) hierarchical nanostructures composed of bimetallic compounds have aroused great attention. In this study, cactus-like bimetallic nickel–cobalt nanosheets with a 3D nanostructure are successfully prepared on the surface of conductive substrate by a one-step hydrothermal reaction. Then a high-efficiency bimetallic catalyst ((Ni,Co)Se2/CFP) is obtained by a facile chemical vapor deposition. Benefiting from bimetallic components and the unique 3D structure, the cactus-like (Ni,Co)Se2/CFP only requires a low overpotential of 154 mV to reach the current density of 10 mA cm−2. The Tafel slope of (Ni,Co)Se2/CFP (67 mV dec−1) further shows that (Ni,Co)Se2/CFP has faster HER kinetics. Besides, the long-term stability test demonstrates the excellent durability of (Ni,Co)Se2/CFP in 0.5 M H2SO4. This research offers a useful technique and guide for improving the structure of bimetallic selenides based on transition metals to design high-efficient HER electrocatalysts.

Tunable Contacts of Bi2 O2 Se Nanosheets MSM Photodetectors by Metal-Assisted Transfer Approach for Self-Powered Near-Infrared Photodetection.

Owing to the Fermi pinning effect arose in the metal electrodes deposition process, metal-semiconductor contact is always independent on the work function, which challenges the next-generation optoelectronic devices. In this work, a metal-assisted transfer approach is developed to transfer Bi2 O2 Se nanosheets onto the pre-deposited metal electrodes, benefiting to the tunable metal-semiconductor contact. The success in Bi2 O2 Se nanosheets transfer is contributed to the stronger van der Waals adhesion of metal electrodes than that of growth substrates. With the pre-deposited asymmetric electrodes, the self-powered near-infrared photodetectors are realized, demonstrating low dark current of 0.04 pA, high Ilight /Idark ratio of 380, fast rise and decay times of 4 and 6ms, respectively, under the illumination of 1310nm laser. By pre-depositing the metal electrodes on polyimide and glass, high-performance flexible and omnidirectional self-powered near-infrared photodetectors are achieved successfully. This study opens up new opportunities for low-dimensional semiconductors in next-generation high-performance optoelectronic devices.

Hierarchical Co0.6Mn0.4Se@CoMo layered double hydroxide ultra-thin nanosheet for high performance hybrid supercapacitor

Designing the novel electrode materials with compositing diverse active components and unique microstructures is an effective strategy to enhance the energy storage capacity of supercapacitors. In this work, the hierarchical composite Co0.6Mn0.4Se@CoMo-LDH, which consists of Co0.6Mn0.4Se nanosheets and CoMo-LDH, is grown directly on nickel foam by hydrothermal reaction, solvothermal selenization reaction and electrodeposition. The prepared material has unique hierarchical interconnected nanosheets, which not only increases the contact area with the electrolyte and enhances the electron transfer ability, but also enables the high capacity through the interaction between active materials. Benefiting from these advantages, the prepared material shows a high specific capacity of 1405.2 C g−1 (at current density of 1 A g−1) and an excellent capacity retention of 88.2% after 10000 cycles. Moreover, the hybrid supercapacitor assembled by Co0.6Mn0.4Se@CoMo-LDH and active carbon achieves a high energy density of 71.4 Wh kg−1 at the power density of 1.13 kW kg−1. Meanwhile, the device shows a cycle performance of 106.2% over 10000 cycles. Because of the superior electrochemical performance, Co0.6Mn0.4Se@CoMo-LDH composites electrode has a tremendous potential in upcoming energy storage technologies.

Controllable synthesis of MnSe2/Co0.85Se nanosheets as a binder-free electrode for high-performance asymmetric supercapacitors

With the increasingly serious environmental pollution and depletion of natural resources, it is necessary to develop efficient and environmentally friendly energy storage equipments to alleviate the problem of resource shortage. In this study, a novel MnSe2/Co0.85Se (MCSe) electrode was successfully prepared using a simple, green and environmentally friendly electrodeposition method. The MCSe electrode exhibited good electrochemical performance, and possesses a high specific capacity (Cs) of 1380C/g at a current density (CD) of 1 A/g. An asymmetric supercapacitor (ASC) assembled using a positive electrode (the MCSe electrode) and a negative electrode (active carbon (AC) electrode) delivered a high specific energy density (Es) of 49.63 Wh/kg at a specific power density (Ps) of 750 W/kg. Hence, this study provides a new approach for designing metal selenides for energy storage and conversion.

Atomic Ru-Doped Ni0.85Se Nanosheets as Efficient Electrocatalysts toward Simulated Seawater Hydrogen Evolution

Atomic Ru-Doped Ni_0.85Se Nanosheets as Efficient Electrocatalysts toward Simulated Seawater Hydrogen Evolution

Ni0.85Se@CoFe LDH heterostructure nanosheet arrays on Ni foam as efficient electrocatalysts for enhanced oxygen evolution

Exploring high-efficient, earth-abundant and stable electrocatalyst for oxygen evolution reaction (OER) is of vital importance for large-scale implementation of energy converting and storing. Thus, we fabricated a free-standing hierarchical heterostructure electrode of Ni0.85Se@CoFe LDH/NF via a rational combination of hydrothermal, selenization and electrodeposition process, among which the ultrathin CoFe LDH nanosheets intimately assembled onto the vertical aligned Ni0.85Se nanosheets supported on Ni foam. The constructed core-shell nanosheet arrays hold the plentiful hetero-interfaces and intimate interactions through metal-oxygen bonds between two individuals, which guarantee the fast OER kinetic processes. Additionally, CoFe LDH with crystalline/amorphous hybrid structure favors providing more reaction sites. Remarkably, the optimal Ni0.85Se@CoFe LDH/NF binary composites possess outstanding OER activity with a low overpotential of ∼223 and 280 mV at 10 mA cm−2 and 100 mA cm−2 in alkaline solution as well as good durability. This research offers an alternative approach for improving electrocatalytic water splitting through constructing 3D hierarchical heterostructures.

Excellent ultraviolet optical limiting properties of Se nanosheets

Selenium (Se) is located in the fourth period of the periodic table in group VIA (element 34). In this experiment, three different solvents (isopropyl alcohol, N-methyl-2-pyrrolidone, and ethanol) were used to prepare the two-dimensional Se nanosheets, which were manufactured by the liquid phase exfoliation method with a thickness of 3.35–4.64 nm and a transverse scale of several hundred nanometers. The nonlinear absorption properties at 355, 532, and 1064 nm were studied using the open aperture Z-scan technique. Final results showed that Se nanosheets exhibited optical limiting (OL) effect in all three wavebands and three solvents, and had large two-photon absorption coefficients, especially in ultraviolet (UV) waveband. Which proved that Se nanosheets had great potential application as excellent OL materials in UV waveband. Our research broadens the path for the semiconductor field of Se, inspires the application of Se in nonlinear optics field.

Ultrasimple synthesis of (Ni,Co)Se2 nanosheets with superior pseudocapacitance capacity as anode for sodium ion battery

Ultrasimple synthesis of (Ni,Co)Se2 nanosheets with superior pseudocapacitance capacity as anode for sodium ion battery

An Ultrasensitive Plasmonic Sensor Based on 2D Ferroelectric Bi2 O2 Se.

Plasmonic biosensing is a label-free detection method that is commonly used to measure various biomolecular interactions. However, one of the main challenges in this approach is the ability to detect biomolecules at low concentrations with sufficient sensitivity and detection limits. Here, 2D ferroelectric materials are employed to address the issues with sensitivity in biosensor design. A plasmonic sensor based on Bi2 O2 Se nanosheets, a ferroelectric 2D material, is presented for the ultrasensitive detection of the protein molecule. Through imaging the surface charge density of Bi2 O2 Se, a detection limit of 1 fM is achieved for bovine serum albumin (BSA). These findings underscore the potential of ferroelectric 2D materials as critical building blocks for future biosensor and biomaterial architectures.

An Ab Initio Study of Two Dimensional SnX2 and Janus SnXY (X = S, Se) Nanosheets as Potential Photocatalysts for Water Splitting

Discriminating appropriate two-dimensional (2D) photocatalysts for hydrogen generation is among the most prospective schemes to tackle with environmental contaminations. Unfortunately, the inferior capability to harvest solar light together with fast recombination of photoexcited carriers can severely reduce the catalytic ability with consequent limited commercial applications. In this work, a series of single-layer MXY (M = Ge, Sn; X, Y = S, Se, and Te) containing T- and H-phases about photocatalytic capabilities are systematically explored by first-principles calculations. First, the T- and H-MXY monolayers possess transformable band gaps of 0–2.37 and 0–1.49 eV, respectively. Astonishingly, the values of T-GeS2, T-SnS2, T-SnSe2, T-SnSSe, and H-SnS2 monolayers are higher than the threshold of redox potential difference (1.23 eV). Also, importantly, the carrier mobilities of anisotropic T-MXY monolayers can reach ∼1 × 104 cm2 V–1 s–1, which can rapidly transfer and accelerate the separation of the photoexcited carriers during photocatalytic reactions. Inspired by these significant benefits, the T-MXY monolayers have been built for photocatalytic water-splitting. Significantly, the driving force of photoexcited carriers in T-SnX2 and Janus T-SnSSe monolayers can greatly promote during the redox reactions. Furthermore, the hydrogen reduction and water oxidation reactions of T-SnX2 and T-SnXY monolayers can proceed spontaneously under irradiation. In addition, the few-layer and even monolayer T-SnS2 and T-SnSe2 have been experimentally synthesized in the literature. The potential photocatalysts of single-layer T-MXY have the 0.25–0.29 J m–2 cleavage energies, and ab initio molecular dynamics simulations further validate their stability. Our results provide support for 2D group-IV–VI chalcogenides for photocatalytic water splitting.

Insights into the selective bactericidal activity of W(Mo)Se2 nanosheets for therapy of pathogenic bacterial infections

The abuse and misuse of broad-spectrum antibiotics cause drug resistance in bacteria, which compromises their benefits and thereby increases the demand for new bactericidal mechanisms to reduce the emergence of multidrug-resistant pathogenic bacteria. Herein, ultrathin WSe2 and MoSe2 nanosheets are exfoliated and functionalized with poly(acrylic acid) (PAA) (PAA-WSe2 and PAA-MoSe2) in an aqueous solution as narrow-spectrum or species-specific antibiotics for the treatment of bacterial infections. PAA-WSe2 nanosheets exhibit narrow-spectrum bactericidal activity with low minimum inhibitory concentrations only for gram-positive bacteria, including multidrug-resistant S. aureus, and PAA-MoSe2 displays species-specific antimicrobial activity against S. aureus without external stimuli. Mechanistic studies have revealed that the redox reactions of PAA-WSe2 nanosheets mediated by lipoteichoic acid of gram-positive bacteria to produce a more active element Se4+ are responsible for their narrow-spectrum bactericidal activity against gram-positive bacteria. Finally, the PAA-WSe2 nanosheets effectively eradicate the bacteria in S. aureus-infected mice, leading to excellent therapeutic efficacy in infected wounds. This strategy, based on narrow-spectrum transition metal dichalcogenide antibiotics, can provide an alternative route for the effective treatment of various bacterial infections.

Efficient Electrocatalytic Reduction of CO2 to Ethanol Enhanced by Spacing Effect of CuCu in Cu2‐xSe Nanosheets

AbstractIt is highly desired yet challenging to strategically steer carbon dioxide (CO2) electroreduction reaction (CO2ER) toward ethanol (EtOH) with high activity, which provides a promising way for intermittent renewable energy reservation. Controlling spatial distance between the adjoining active centers and promoting the CC coupling progress are crucial to realize this purpose. Herein, ultrathin 2D Cu2‐xSe is prepared with abundant Se vacancies, where the spatial distance between the CuCu around the Se vacancies is effectively shortened because of the lattice stress. Besides, the moderate spatial distance induced by Se vacancies can significantly decrease the Gibbs free energy of asymmetric *CO*CHO coupling progress, effectively change the local charge distribution, decrease the valence state of Cu atoms and increase the electron‐donating capacity of the dual active sites. Combining experimental observations and density functional theory simulations, the CuCu dual sites with spatial distance of 2.51 Å in VSe‐Cu2‐xSe sample can catalyze CO2ER to EtOH with high selectivity in a potential range from −0.4 to −1.6 V, and reach the highest faradaic efficiency of 68.1% at −0.8 V. This work reveals the influence of spacing effect on ethanol selectivity, and provides a new idea for future design of catalysts with chain elongation reaction, which can bring extensive attention.

MoxTa(1-x)Se2 as saturable absorber for ultrafast photonics

Two-dimension ternary transition metal dichalcogenides have drawn great interests from both the fields of nanotechnology and materials science, due to their extraordinary physical performance, and great potential applications in nanodevice. Here, the applications of MoxTa(1-x)Se2 nanosheets in ultrafast photonics are discussed. The MoxTa(1-x)Se2 nanosheets are prepared by liquid phase exfoliation method. A MoxTa(1-x)Se2-based saturable absorber is fabricated by depositing these nanosheets onto the side surface of d-shaped fiber, which is inserted into a Er-doped fiber laser cavity. By adjusting polarization state and pump power, both harmonic mode-locking and large energy mode-locking operations are realized, respectively. In the former state, a 56th harmonic mode-locking is obtained, which corresponds to a repetition rate of 312.5 MHz. For the later state, the maximum average output power of 12.24 mW and single pulse energy of 2.19 nJ are obtained when the pump power is 500mW. The results demonstrate that MoxTa(1-x)Se2 can be widely used in ultrafast photonics and nonlinear optics.