130 research outputs found
Recommended from our members
Controlling palladium morphology in electrodeposition from nanoparticles to dendrites via the use of mixed solvents
By changing the mole fraction of water (χwater) in the solvent acetonitrile (MeCN), we report a simple procedure to control nanostructure morphology during electrodeposition. We focus on the electrodeposition of palladium (Pd) on electron beam transparent boron-doped diamond (BDD) electrodes. Three solutions are employed, MeCN rich (90% v/v MeCN, χwater = 0.246), equal volumes (50% v/v MeCN, χwater = 0.743) and water rich (10% v/v MeCN, χwater = 0.963), with electrodeposition carried out under a constant, and high overpotential (−1.0 V), for fixed time periods (50, 150 and 300 s). Scanning transmission electron microscopy (STEM) reveals that in MeCN rich solution, Pd atoms, amorphous atom clusters and (majority) nanoparticles (NPs) result. As water content is increased, NPs are again evident but also elongated and defected nanostructures which grow in prominence with time. In the water rich environment, NPs and branched, concave and star-like Pd nanostructures are now seen, which with time translate to aggregated porous structures and ultimately dendrites. We attribute these observations to the role MeCN adsorption on Pd surfaces plays in retarding metal nucleation and growth
Atomic level termination for passivation and functionalisation of silicon surfaces
Chemical treatments play an essential role in the formation of high quality interfaces between materials, including in semiconductor devices, and in the functionalisation of surfaces. We have investigated the effects of hydrogen and fluorine termination of (100)-orientation silicon surfaces over a range of length scales. At the centimetre scale, lifetime measurements show clean silicon surfaces can be temporarily passivated by a short treatment in both HF(2%) : HCl(2%) and HF(50%) solutions. The lifetime, and hence surface passivation, becomes better with immersion time in the former, and worse with immersion time in the latter. At the nanometre scale, X-ray photoelectron spectroscopy and atomic force microscopy show treatment with strong HF solutions results in a roughened fluorine-terminated surface. Subsequent superacid-derived surface passivation on different chemically treated surfaces shows considerably better passivation on surfaces treated with HF(2%) : HCl(2%) compared to HF. Lifetime data are modelled to understand the termination in terms of chemical and field effect passivation at the centimetre scale. Surfaces passivated with Al2O3 grown by atomic layer deposition behave similarly when either HF(2%) : HCl(2%) or HF(50%) are used as a pre-treatment, possibly because of the thin silicon dioxide interlayer which subsequently forms. Our study highlights that chemical pre-treatments can be extremely important in the creation of high quality functionalised surfaces
Tracking Systems in Team Sports: A Narrative Review of Applications of the Data and Sport Specific Analysis.
Seeking to obtain a competitive advantage and manage the risk of injury, team sport organisations are investing in tracking systems that can quantify training and competition characteristics. It is expected that such information can support objective decision-making for the prescription and manipulation of training load. This narrative review aims to summarise, and critically evaluate, different tracking systems and their use within team sports. The selection of systems should be dependent upon the context of the sport and needs careful consideration by practitioners. The selection of metrics requires a critical process to be able to describe, plan, monitor and evaluate training and competition characteristics of each sport. An emerging consideration for tracking systems data is the selection of suitable time analysis, such as temporal durations, peak demands or time series segmentation, whose best use depends on the temporal characteristics of the sport. Finally, examples of characteristics and the application of tracking data across seven popular team sports are presented. Practitioners working in specific team sports are advised to follow a critical thinking process, with a healthy dose of scepticism and awareness of appropriate theoretical frameworks, where possible, when creating new or selecting an existing metric to profile team sport athletes
The relationship between sustained inattentional blindness and working memory capacity
High Temperature Superconductivity: the explanation
Soon after the discovery of the first high temperature superconductor by
Georg Bednorz and Alex Mueller in 1986 the late Sir Nevill Mott answering his
own question "Is there an explanation?" [Nature v 327 (1987) 185] expressed a
view that the Bose-Einstein condensation (BEC) of small bipolarons, predicted
by us in 1981, could be the one. Several authors then contemplated BEC of real
space tightly bound pairs, but with a purely electronic mechanism of pairing
rather than with the electron-phonon interaction (EPI). However, a number of
other researchers criticized the bipolaron (or any real-space pairing) scenario
as incompatible with some angle-resolved photoemission spectra (ARPES), with
experimentally determined effective masses of carriers and unconventional
symmetry of the superconducting order parameter in cuprates. Since then the
controversial issue of whether the electron-phonon interaction (EPI) is crucial
for high-temperature superconductivity or weak and inessential has been one of
the most challenging problems of contemporary condensed matter physics. Here I
outline some developments in the bipolaron theory suggesting that the true
origin of high-temperature superconductivity is found in a proper combination
of strong electron-electron correlations with a significant finite-range
(Froehlich) EPI, and that the theory is fully compatible with the key
experiments.Comment: 8 pages, 2 figures, invited comment to Physica Script
Large-Area Electrodeposition of Few-Layer MoS2 on Graphene for 2D Material Heterostructures
Heterostructures involving two-dimensional (2D) transition metal
dichalcogenides and other materials such as graphene have a strong potential to
be the fundamental building block of many electronic and opto-electronic
applications. The integration and scalable fabrication of such heterostructures
is of essence in unleashing the potential of these materials in new
technologies. For the first time, we demonstrate the growth of few-layer MoS2
films on graphene via non-aqueous electrodeposition. Through methods such as
scanning and transmission electron microscopy, atomic force microscopy, Raman
spectroscopy, energy and wavelength dispersive X-ray spectroscopies and X-ray
photoelectron spectroscopy, we show that this deposition method can produce
large-area MoS2 films with high quality and uniformity over graphene. We reveal
the potential of these heterostructures by measuring the photo-induced current
through the film. These results pave the way towards developing the
electrodeposition method for the large-scale growth of heterostructures
consisting of varying 2D materials for many applications.Comment: 11 pages and 6 figure
Theory of Extrinsic and Intrinsic Tunnelling in Cuprate Superconductors
A theory capable of explaining intrinsic and extrinsic tunnelling conductance
in underdoped cuprates has been devised that accounts for the existence of two
energy scales, their temperature and doping dependencies. The asymmetry and
inhomogeneity seen in extrinsic (normal metal - superconductor (NS)) tunnelling
and the normal-state gapped intrinsic (SS) conductance is explained, as well as
the superconducting gap and normal state pseudogap and the temperature
dependence of the full gap.Comment: 14 pages, 10 figures, misprints correcte
Atomic-scale investigation of the reversible α- to ω-phase lithium ion charge – discharge characteristics of electrodeposited vanadium pentoxide nanobelts
Using an electrochemical potential pulse methodology in a mixed solvent system, electrochemical deposition of amorphous vanadium pentoxide (V2O5) nanobelts is possible. Crystallisation of the material is achieved using in air annealing with the temperature of crystallisation identified using in situ heating transmission electron microscopy (TEM). The resulting α-phase V2O5 nanobelts have typical thicknesses of 10–20 nm, widths and lengths in the range 5–37 nm (mean 9 nm) and 15–221 nm (mean 134 nm), respectively. One-cycle reversibility studies for lithium intercalation (discharge) and de-intercalation (charge) reveal a maximum specific capacity associated with three lithium ions incorporated per unit cell, indicative of ω-Li3V2O5 formation. Aberration corrected scanning TEM confirm the formation of ω-Li3V2O5 across the entirety of a nanobelt during discharge and also the reversible formation of the α-V2O5 phase upon full charge. Preliminary second cycle studies reveal reformation of the ω-Li3V2O5, accompanied with a morphological change in the nanobelt dimensions. Achieving α-V2O5 to ω-Li3V2O5 to α-V2O5 reversibility is extremely challenging given the large structural rearrangements required. This phenomenon has only been seen before in a very limited number of studies, mostly employing nanosized V2O5 materials and never before with electrodeposited material
- …