Van der Waals epitaxy growth of 2D ferromagnetic Cr_(1+δ)Te₂ nanolayers with concentration-tunable magnetic anisotropy

Cr(1+δ)Te2 are pseudo-layered compounds consisting of CrTe2 transition metal dichalcogenide (TMD) layers with additional (δ) self-intercalated Cr atoms. The recent search for ferromagnetic 2D materials revived the interest into chromium tellurides. Here, Cr(1+δ)Te2 nanolayers are epitaxially grown on MoS2 (0001), forming prototypical van der Waals heterostructures. Under optimized growth conditions, ultrathin films of only two TMD layers with a single intercalated Cr-layer are achieved, forming a 2D sheet with van der Waals surfaces. Detailed compositional and structural characterization by scanning tunneling microscopy, grazing incidence x-ray diffraction, and high-resolution Rutherford backscattering indicate the layer-by-layer growth and that the δ can be tuned by post-growth annealing in a range between ∼0.5 and 1. X-ray magnetic circular dichroism and magnetometry measurements demonstrate that all self-intercalated Cr(1+δ)Te2 nanolayers exhibit strong ferromagnetism with magnetic moments larger than 3μB per Cr-atom. The magnetic properties are maintained in the ultrathin limit of a material with a single intercalation layer. Interestingly, the magnetic anisotropy can be tuned from close to isotropic (δ = 1) to a desirable perpendicular anisotropy for low δ values. Thus, the bottom-up growth of these 2D Cr(1+δ)Te2 sheets is a promising approach for designing magnetic van der Waals heterostructures

Nitrogen doping of TiO2 photocatalyst forms a second eg state in the Oxygen (1s) NEXAFS pre-edge

Close inspection of the pre-edge in oxygen near-edge x-ray absorption fine structure spectra of single step, gas phase synthesized titanium oxynitride photocatalysts with 20 nm particle size reveals an additional eg resonance in the VB that went unnoticed in previous TiO2 anion doping studies. The relative spectral weight of this Ti(3d)-O(2p) hybridized state with respect to and located between the readily established t2g and eg resonances scales qualitatively with the photocatalytic decomposition power, suggesting that this extra resonance bears co-responsibility for the photocatalytic performance of titanium oxynitrides at visible light wavelengths

Structurally driven one-dimensional electron confinement in sub-5-nm graphene nanowrinkles

Graphene-based carbon materials such as fullerenes, carbon nanotubes, and graphenes have distinct and unique electronic properties that depend on their dimensionality and geometric structures. Graphene wrinkles with pseudo one-dimensional structures have been observed in a graphene sheet. However, their one-dimensional electronic properties have never been observed because of their large widths. Here we report the unique electronic structure of graphene nanowrinkles in a graphene sheet grown on Ni(111), the width of which was small enough to cause one-dimensional electron confinement. Use of spatially resolved, scanning tunnelling spectroscopy revealed bandgap opening and a one-dimensional van Hove singularity in the graphene nanowrinkles, as well as the chemical potential distribution across the graphene nanowrinkles. This observation allows us to realize a metallic-semiconducting-metallic junction in a single graphene sheet. Our demonstration of one-dimensional electron confinement in graphene provides the novel possibility of controlling its electronic properties not by chemical modification but by 'mechanical structuring'.open

Nanocomposite ZnO–SnO2 Nanofibers Synthesized by Electrospinning Method

We report the characterization of mixed oxides nanocomposite nanofibers of (1 − x) ZnO-(x)SnO2 (x ≤ 0.45) synthesized by electrospinning technique. The diameter of calcined nanofibers depends on Sn content. Other phases like SnO, ZnSnO3, and Zn2SnO4 were absent. Photoluminescence studies show that there is a change in the blue/violet luminescence confirming the presence of Sn in Zn-rich composition. Present study shows that the crystalline nanocomposite nanofibers with stoichiometry of (1 − x)ZnO-(x)SnO2 (x ≤ 0.45) stabilize after the calcination and possess some morphological and optical properties that strongly depend on Sn content

CVD-Enabled Graphene Manufacture and Technology.

Integrated manufacturing is arguably the most challenging task in the development of technology based on graphene and other 2D materials, particularly with regard to the industrial demand for “electronic-grade” large-area films. In order to control the structure and properties of these materials at the monolayer level, their nucleation, growth and interfacing needs to be understood to a level of unprecedented detail compared to existing thin film or bulk materials. Chemical vapor deposition (CVD) has emerged as the most versatile and promising technique to develop graphene and 2D material films into industrial device materials and this Perspective outlines recent progress, trends, and emerging CVD processing pathways. A key focus is the emerging understanding of the underlying growth mechanisms, in particular on the role of the required catalytic growth substrate, which brings together the latest progress in the fields of heterogeneous catalysis and classic crystal/thin-film growth.Funding from the ERC (Grant No. 279342, InSituNANO) and EPSRC (Grant No. EP/K016636/1, GRAPHTED) is acknowledged. R.S.W. acknowledges a research fellowship from St. John’s College, Cambridge.This is the final version of the article. It first appeared from ACS via http://dx.doi.org/10.1021/acs.jpclett.5b0105

Palladium nanoparticles supported on fluorine-doped tin oxide as an efficient heterogeneous catalyst for Suzuki coupling and 4-nitrophenol reduction

Immobilization of palladium nanoparticles onto the fluorine-doped tin oxide (FTO) as support Pd/FTO, resulted in a highly active heterogeneous catalyst for Suzuki-Miyaura cross-coupling reactions and 4-nitrophenol reduction. The Pd/FTO catalyst has been synthesized by immobilization of palladium nanoparticles onto FTO via a simple impregnation method. ICP-MS analysis confirmed that there is 0.11 mmol/g of palladium was loaded successfully on FTO support. The crystallinity, morphologies, compositions and surface properties of Pd/FTO were fully characterized by various techniques. It was further examined for its catalytic activity and robustness in Suzuki coupling reaction with different aryl halides and solvents. The yields obtained from Suzuki coupling reactions were basically over 80%. The prepared catalyst was also tested on mild reaction such as reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Pd/FTO catalyst exhibited high catalytic activity towards 4-NP reduction with a rate constant of 1.776 min(-1) and turnover frequency (TOF) value of 29.1 hr(-1). The findings revealed that Pd/FTO also maintained its high stability for five consecutive runs in Suzuki reactions and 4-NP reductions. The catalyst showed excellent catalytic activities by using a small amount of Pd/FTO for the Suzuki coupling reaction and 4-NP reduction