Ion Irradiation Inducing Oxygen Vacancy-Rich NiO/NiFe2 O4 Heterostructure for Enhanced Electrocatalytic Water Splitting.

Oxygen evolution reaction (OER) is an obstacle to the electrocatalytic water splitting due to its unique four-proton-and-electron-transfer reaction process. Many methods, such as engineering heterostructure and introducing oxygen vacancy, have been used to improve the catalytic performance of electrocatalysts for OER. Herein, the above two kinds of regulation are simultaneously realized in a catalyst by using unique ion irradiation technology. A nanosheet structured NiO/NiFe2 O4 heterostructure with rich oxygen vacancies converted from nickel-iron layered double hydroxides by Ar+ ions irradiation shows significant enhancement in both OER and hydrogen evolution reaction performance. Density functional theory (DFT) calculations reveal that the construction of NiO/NiFe2 O4 can optimize the free energy of O* to OOH* process during OER reaction. The oxygen vacancy-rich NiO/NiFe2 O4 nanosheets have an overpotential of 279 mV at 10 mA cm-2 and a low Tafel slope of 42 mV dec-1 . Moreover, this NiO/NiFe2 O4 electrode shows an excellent long-term stability at 100 mA cm-2 for 450 h. The synergetic effects between NiO and NiFe2 O4 make NiO/NiFe2 O4 heterostructure have high conductivity and fast charge transfer, abundant active sites, and high catalytic reactivity, contributing to its excellent performance.

Synthesis of Allenyl-Bdan via the Cu(I)-Catalyzed Borylation of Propargylic Alcohols with the Unsymmetric Diboron Reagent (Bpin-Bdan).

The synthesis of allenyl-Bdan has been realized via the Cu(I)-catalyzed borylation of propargylic alcohols. This methodology offers a facile and efficient pathway toward allenyboronates with diverse functional groups due to the simple access to the substrates. The substrates bearing ester groups are well-tolerated in the synthesis of allenyl-Bdan under the Lewis acidic conditions. The structures of two allenyl-Bdan were further confirmed via single-crystal X-ray diffraction.

Molybdenum Disulfide Nanosheet/Quantum Dot Dynamic Memristive Structure Driven by Photoinduced Phase Transition.

MoS2 2D nanosheets (NS) with intercalated 0D quantum dots (QDs) represent promising structures for creating low-dimensional (LD) resistive memory devices. Nonvolatile memristors based 2D materials demonstrate low power consumption and ultrahigh density. Here, the observation of a photoinduced phase transition in the 2D NS/0D QDs MoS2 structure providing dynamic resistive memory is reported. The resistive switching of the MoS2 NS/QD structure is observed in an electric field and can be controlled through local QD excitations. Photoexcitation of the LD structure at different laser power densities leads to a reversible MoS2 2H-1T phase transition and demonstrates the potential of the LD structure for implementing a new dynamic ultrafast photoresistive memory. The dynamic LD photomemristive structure is attractive for real-time pattern recognition and photoconfiguration of artificial neural networks in a wide spectral range of sensitivity provided by QDs.

Small Al cluster ion implantation into Si and 4H-SiC.

RATIONALE: Continuously downscaling integrated circuit devices requires fabrication of shallower p-n junctions. The ion implantation approach at low energy is subject to low beam current due to the Coulomb repulsion. To overcome this problem cluster ions can be used for implantation. In comparison with single ions, cluster ions possess lower energy per atom and reduced Coulomb repulsion resulting in high equivalent current. METHODS: In this study to carry out low-energy implantation into single crystalline silicon and 4H-SiC samples we employ Aln - (n = 1-5) clusters with energy in the range of 5-20 keV. The Al clusters are obtained by Cs sputtering of Al rod. Time-of-flight secondary ion mass spectrometry (TOF-SIMS; IONTOF TOF.SIMS-5) is used to study aluminum and oxygen sputter depth profiles for different cluster sizes and implantation energies before and after annealing treatment. RESULTS: A distinguishable effect of the energy per atom in the cluster on reduction of the projected range Rp is revealed. The lowest Rp of 3 ± 1 nm has been achieved in SiC samples at the energy per atom of 1.66 keV. After annealing of Si samples, a considerable change in the Al profiles due to redistribution of Al atoms during motion of the front of recrystallization is observed. The influence of the number of atoms in the cluster at the same energy per atom within the experimental uncertainty is not observed. CONCLUSIONS: The transient effects of the sputtering by the primary ion beam distort the shape of the Al profiles in Si samples. In the case of SiC, due to its relatively lower surface chemical activity, more informative TOF-SIMS depth profiling of the shallow cluster implantation is feasible.

Identification of SSTR5 Gene Polymorphisms and Their Association With Growth Traits in Hulun Buir Sheep.

The aim of this study was to locate SSTR5 polymorphisms and evaluate their association with growth traits in Hulun Buir sheep. The study followed up 884 Hulun Buir sheep from birth to 16 months of age, which were born in the same pasture and the same year, and a consistent grazing management strategy was maintained. The birth weight (BRW) was recorded at birth, and body weight (BW), body height (BH), body length (BL), chest circumference (ChC), chest depth (ChD), chest width (ChW), hip width (HW), and cannon circumference (CaC) were measured at 4 and 9 months of age. BW, BH, BL, ChD, HW, and CaC were also recorded at 16 months of age. Based on the growth traits, 233 sheep were selected as experimental animals. Sanger sequencing was performed, and seven single-nucleotide polymorphisms (SNPs) were identified. Association analyses of the SNPs and the growth traits were then conducted. Seven SNPs of the SSTR5 exhibited moderate polymorphism (0.25

Geometry-asymmetric photodetectors from metal-semiconductor-metal van der Waals heterostructures.

The functional diversities of two-dimensional (2D) material devices with simple architectures are ultimately limited by immature doping techniques. An alternative strategy is to use geometry-asymmetric metal-semiconductor-metal (GA-MSM) structures, which enable the basic functions of semiconductor junctions such as rectification and photovoltaics. Here, the mixed-dimensional van der Waals heterostructures (MDvdWHs) based on the separation and self-assembly of p-type SnS layered nanosheets (NSs) and n-type SnS2 nanoparticles (NPs) are obtained using an aqueous phase exfoliation (APE) method. Due to the surface charge transfer doping, the carrier transport mechanism of devices based on MDvdWHs turns from thermionic field emission (TFE) to thermionic emission (TE), with the rectification factor (Iforward/Ireverse) changing from 0.7 to 3. To further illustrate the experimental results, the generic current transport models of GA-MSM devices have been established based on the TE and TFE mechanisms in which the TE and TFE mechanisms lead to opposite rectification phenomena in good agreement with the experimental results. The GA-MSM devices show a photovoltaic effect with a high responsivity of 35 A W-1 and detectivity of 3.4 × 1011 cm Hz1/2 W-1. This study not only provides a novel strategy to design photovoltaic devices with MDvdWHs, but more importantly, we have established fundamental models for the rectification behavior of GA-MSM devices.

Formation of nanoripples on ZnO flat substrates and nanorods by gas cluster ion bombardment.

In the present study Ar+ cluster ions accelerated by voltages in the range of 5-10 kV are used to irradiate single crystal ZnO substrates and nanorods to fabricate self-assembled surface nanoripple arrays. The ripple formation is observed when the incidence angle of the cluster beam is in the range of 30-70°. The influence of incidence angle, accelerating voltage, and fluence on the ripple formation is studied. Wavelength and height of the nanoripples increase with increasing accelerating voltage and fluence for both targets. The nanoripples formed on the flat substrates remind of aeolian sand ripples. The ripples formed at high ion fluences on the nanorod facets resemble well-ordered parallel steps or ribs. The more ordered ripple formation on nanorods can be associated with the confinement of the nanorod facets in comparison with the quasi-infinite surface of the flat substrates.

Electrophoretic Deposited Black Phosphorus on 3D Porous Current Collectors to Regulate Li Nucleation for Dendrite-Free Lithium Metal Anodes.

Li metal is considered a highly desirable anode for next-generation high-energy-density rechargeable lithium batteries. However, irregular Li dendrite formation and infinite relative volume changes prevent the commercial adoption of Li-metal anodes. Here, electrophoretic deposition of black phosphorus (BP) on commercial Cu foam (BP@Cu foam) is reported to regulate Li nucleation for the first time. First-principles calculations reveal that the unique two-dimensional (2D) structure of BP is beneficial to Li intercalation and propagation. Compared with the random Li nucleation and growth on bare Cu foam, Li ions are preferably confined into the BP layers, which induces uniform Li nucleation at the early stage of the Li deposition and guides the following lateral Li growth on BP@Cu foam. In addition, the three-dimensional (3D) porous and conductive framework of Cu foams further mitigate the volume change and dissipate the current density. Attributing to these merits, the BP@Cu foam exhibits significantly enhanced Coulombic efficiency and cycling stability compared with bare Cu foam. In the full-cell configuration paired with a Li4Ti5O12 or LiFePO4 cathode, the BP@Cu foam also boosts the battery performances. This work provides new insights into the development of BP and other elaborate 2D materials for achieving dendrite-free Li-metal anodes.

Synthesis of ternary oxide Zn2GeO4 nanowire networks and their deep ultraviolet detection properties.

Ternary oxide Zn2GeO4 with a wide bandgap of 4.84 eV, as a candidate for fourth generation semiconductors, has attracted a great deal of attention for deep ultraviolet (DUV) photodetector applications, because it is expected to be blind to the UV-A/B band (290-400 nm) and only responsive to the UV-C band (200-290 nm). Here, we report on the synthesis of Zn2GeO4 nanowire (NW) networks by lower pressure chemical vapor deposition and investigate their corresponding DUV detection properties. We find that pure Zn2GeO4 NWs could be obtained at a growth pressure of 1 kPa. The DUV detection tests reveal that growth pressure exerts a significant effect on DUV detection performance. The Zn2GeO4 NW networks produced under 1 kPa show an excellent solar-blind photoresponsivity with fast rise and decay times (t rise ≈ 0.17 s and t decay ≈ 0.14 s).

Sputtering of silicon nanopowders by an argon cluster ion beam.

In this work an Ar+ cluster ion beam with energy in the range of 10-70 keV and dose of 7.2 × 1014-2.3 × 1016 cluster/cm2 was used to irradiate pressed Si nanopowder targets consisting of particles with a mean diameter of 60 nm. The influence of the target density and the cluster ion beam parameters (energy and dose) on the sputtering depth and sputtering yield was studied. The sputtering yield was found to decrease with increasing dose and target density. The energy dependence demonstrated an unusual non-monotonic behavior. At 17.3 keV a maximum of the sputtering yield was observed, which was more than forty times higher than that of the bulk Si. The surface roughness at low energy demonstrates a similar energy dependence with a maximum near 17 keV. The dose and energy dependence of the sputtering yield was explained by the competition of the finite size effect and the effect of debris formation.

Side extraction: A novel method of filtering ions or macro-particles for vacuum arc ion sources.

A novel ion-extraction method named side extraction, i.e., extracting ions from the direction perpendicular to that of plasma expansion, is proposed in this paper, which can be used to filter ions or macro-particles for vacuum arc ion sources. Particle-in-cell simulations were performed to study filtering effects of side extraction on ions with different mass, different charges, and different initial kinetic energies. The results indicate that side extraction can separate ions by their charge states or initial kinetic energies and the extracting efficiency for different ion species is identical. Influences of extraction voltages, extraction interval, and the aspect ratio of the extraction aperture on ion filtering effects were also studied, which suggests that lower extraction voltages and longer extraction interval are beneficial for ion filtering and a high-aspect-ratio aperture contributes to the increase in the ratio of lighter ions in extracted beams. A theoretical analysis on the deflected distance of beams in the y direction was made and shows good agreement with the simulation results.

Studies of La- and Pr-driven reverse distortion of FeO6 octahedral structure, magnetic properties and hyperfine interaction of BiFeO3 powder.

The Bi1-x-y La x Pr y FeO3 (x = 0 and 0.05; y = 0, 0.10, 0.15 and 0.20) (BLPFO) powders were prepared using a hydrothermal method. The lattice structure of the samples was characterized by X-ray diffraction, which revealed an increase in the lattice constant of the doped samples evidencing the substitution of Bi by La and Pr ions. Raman spectroscopy was used to further analyse the structural distortion in the samples. Scanning electron microscopy was used to characterize the morphology of the samples. The atomic concentrations (%) of La and Pr elements in the samples were detected by Energy Dispersive X-ray spectroscopy. The ferromagnetism of the samples increased with the increase in La and Pr co-doping concentration as observed by vibrating sample magnetometry at room temperature. The evidence of reverse distortion of FeO6 octahedral structure in the La and Pr co-doped samples was revealed by the Mössbauer spectra parameters: Is, Qs, H, Γ, χ 2 and area ratio (A 1/A 2) of two sextets.

Self-assembled MoS2/rGO nanocomposites with tunable UV-IR absorption.

MoS2/reduced graphene oxide (rGO) nanocomposites were synthesized using an ultrasonic pretreatment with a single-stage hydrothermal and reduction process. Self-assembled MoS2 layers in the rGO matrix were obtained. The effect of quantum confinement in the structure, controlled by the degree of reduction of graphene oxide and the size of the 2D MoS2 nanocrystals, made it possible to obtain tunable optical absorption. MoS2/rGO layered nanocomposites exhibit a wide UV-IR absorption in the wavelength range from 280 nm to 973 nm, which is attractive for highly efficient multiband solar cells and advanced photonics.

Enhanced visible light photodegradation activity of RhB/MB from aqueous solution using nanosized novel Fe-Cd co-modified ZnO.

A series of novel Fe-Cd co-doped ZnO nanoparticle based photocatalysts are successfully synthesized by sol-gel route and characterized using scanning electron microscopy (SEM), energy dispersive X-ray emission (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) techniques. The photocatalytic activity of ZnO nanoparticles doped with various atomic weight fraction of Fe and Cd has been investigated under visible light irradiation using the Methylene Blue and Rhodamine B dye in aqueous solution. The FeCd (2%):ZnO (ZFC-1) exhibit the highest photocatalytic activity in terms of rate constant as KMB = 0.01153 min-1 and KRhB = 0.00916 min-1). Further, the re-usability of the ZFC-1 photocatalyst is studied which confirms that it can be reused up to five times with nearly negligible loss of the photocatalytic efficiency. Moreover, the role of photoactive species investigated using a radical scavenger technique. The present investigations show that the doping concentration plays significant role in photocatalytic performance. The visible light absorption shown by Fe-Cd co-doped ZnO nanoparticles is much higher than that of undoped body probably due to co-doping, and the charge carrier recombination is decreased effectively which yields a higher photocatalytic performance. The mechanism for the enhancement of photocatalytic activity under visible light irradiation is also proposed.

RBS Depth Profiling Analysis of (Ti, Al)N/MoN and CrN/MoN Multilayers.

(Ti, Al)N/MoN and CrN/MoN multilayered films were synthesized on Si (100) surface by multi-cathodic arc ion plating system with various bilayer periods. The elemental composition and depth profiling of the films were investigated by Rutherford backscattering spectroscopy (RBS) using 2.42 and 1.52 MeV Li2+ ion beams and different incident angles (0°, 15°, 37°, and 53°). The microstructures of (Ti, Al)N/MoN multilayered films were evaluated by X-ray diffraction. The multilayer periods and thickness of the multilayered films were characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) and then compared with RBS results.

MoS2 memristor with photoresistive switching.

A MoS2 nanosphere memristor with lateral gold electrodes was found to show photoresistive switching. The new device can be controlled by the polarization of nanospheres, which causes resistance switching in an electric field in the dark or under white light illumination. The polarization charge allows to change the switching voltage of the photomemristor, providing its multi-level operation. The device, polarized at a voltage 6 V, switches abruptly from a high resistance state (HRSL6) to a low resistance state (LRSL6) with the On/Off resistance ratio of about 10 under white light and smooth in the dark. Analysis of device conductivity in different resistive states indicates that its resistive state could be changed by the modulation of the charge in an electric field in the dark or under light, resulting in the formation/disruption of filaments with high conductivity. A MoS2 photomemristor has great potential as a multifunctional device designed by using cost-effective fabrication techniques.

A preparation approach of exploring cluster ion implantation: from ultra-thin carbon film to graphene.

Based on the extensive application of 2 × 1.7MV Tandetron accelerator, a low-energy cluster chamber has been built to explore for synthesizing graphene. Raman spectrum and atomic force microscopy (AFM) show that an amorphous carbon film in nanometer was deposited on the silicon by C4 cluster implantation. And we replaced the substrate with Ni/SiO2/Si and measured the thickness of Ni film by Rutherford backscattering spectrometry (RBS). Combined with suitable anneal conditions, these samples implanted by various small carbon clusters were made to grow graphene. Results from Raman spectrum reveal that few-layer graphene were obtained and discuss whether I G/I 2D can contribute to explain the relationship between the number of graphene layers and cluster implantation dosage.

A novel gas ionization sensor using Pd nanoparticle-capped ZnO.

A novel gas ionization sensor using Pd nanoparticle-capped ZnO (Pd/ZnO) nanorods as the anode is proposed. The Pd/ZnO nanorod-based sensors, compared with the bare ZnO nanorod, show lower breakdown voltage for the detected gases with good sensitivity and selectivity. Moreover, the sensors exhibit stable performance after more than 200 tests for both inert and active gases. The simple, low-cost, Pd/ZnO nanorod-based field-ionization gas sensors presented in this study have potential applications in the field of gas sensor devices.