Chiesa M.,Masdar Institute of Science and Technology |
Gadelrab K.,Masdar Institute of Science and Technology |
Stefancich M.,Masdar Institute of Science and Technology |
Armstrong P.,Masdar Institute of Science and Technology |
And 8 more authors.
Journal of Physical Chemistry Letters | Year: 2012
Multifrequency atomic force microscopy holds promise as a method to provide qualitative and quantitative information about samples with high spatial resolution. Here, we provide experimental evidence of the excitation of subharmonics in ambient conditions in the regions where capillary interactions are predicted to be the mechanism of excitation. We also experimentally decouple a second mechanism for subharmonic excitation that is highly independent of environmental conditions such as relative humidity. This implies that material properties could be mapped. Subharmonic excitation could lead to experimental determination of surface water affinity in the nanoscale whenever water interactions are the mechanism of excitation. © 2012 American Chemical Society.
Chiesa M.,Masdar Institute of Science and Technology |
Gadelrab K.R.,Masdar Institute of Science and Technology |
Verdaguer A.,Catalan Institute of Nanoscience and Nanotechnology |
Segura J.J.,Catalan Institute of Nanoscience and Nanotechnology |
And 5 more authors.
EPL | Year: 2012
Amplitude modulation atomic force microscopy allows quantifying energy dissipation in the nanoscale with great accuracy with the use of analytical expressions that account for the fundamental frequency and higher harmonics. Here, we focus on the effects of sub-harmonic excitation on energy dissipation and its quantification. While there might be several mechanisms inducing sub-harmonics, a general analytical expression to quantify energy dissipation whenever sub-harmonics are excited is provided. The expression is a generalization of previous findings. We validate the expression via numerical integration by considering capillary forces and provide experimental evidence of sub-harmonic excitation for a range of operational parameters. © Copyright EPLA, 2012.
Lu M.,Physical and Theoretical Chemistry Laboratory |
Toghill K.E.,Physical and Theoretical Chemistry Laboratory |
Phillips M.A.,Asylum Research UK Ltd |
Compton R.G.,Physical and Theoretical Chemistry Laboratory
International Journal of Environmental Analytical Chemistry | Year: 2013
Antimony is an element of significant environmental concern, yet has been neglected relative to other heavy metals in electroanalysis. As such very little research has been reported on the electroanalytical determination of antimony at unmodified carbon electrodes. In this paper we report the electrochemical determination of Sb(III) in HCl solutions using unmodified carbon substrates, with focus on non-classical carbon materials namely edge plane pyrolytic graphite (EPPG), boron doped diamond (BDD) and screen-printed electrodes (SPE). Using differential pulse anodic stripping voltammetry, EPPG was found to give a considerably greater response towards antimony than other unmodified carbon electrodes, allowing highly linear ranges in nanomolar concentrations and a detection limit of 3.9 nM in 0.25 M HCl. Furthermore, the sensitivity of the response from EPPG was 100 times greater than for glassy carbon (GC). Unmodified GC gave a comparable response to previous results using the bare substrate, and BDD gave an improved, yet still very high limit of detection of 320 nM compared to previous analysis using an iridium oxide modified BDD electrode. SPEs gave a very poor response to antimony, even at high concentrations, observing no linearity from standard additions, as well as a major interference from the ink intrinsic to the working electrode carbon material. Owing to its superior performance relative to other carbon electrodes, the EPPG electrode was subjected to further analytical testing with antimony. The response of the electrode for a 40 nM concentration of Sb(III) was reproducible with a mean peak current of 1.07 μA and variation of 8.4% (n = 8). The effect of metals copper, bismuth and arsenic were investigated at the electrode, as they are common interferences for stripping analysis of antimony. © 2013 Copyright Taylor and Francis Group, LLC.
Toghill K.E.,University of Oxford |
Xiao L.,University of Oxford |
Phillips M.A.,Asylum Research UK Ltd. |
Compton R.G.,University of Oxford
Sensors and Actuators, B: Chemical | Year: 2010
A nickel modified boron-doped diamond (Ni-BDD) electrode or nickel foil electrode were used in the non-enzymatic determination of glucose in alkaline solutions. The Ni-BDD electrode was electrodeposited from a 1 mM Ni(NO3)2 solution (pH 5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)2/NiOOH redox couple to electrocatalyse the oxidation of glucose. Glucose was determined to limits of 2.7 μM with a sensitivity of 1.04 μA μM-1 cm-2 at the Ni-BDD electrode. The foil electrode was comparably sensitive achieving a limit of 1.8 μM but a relatively lower sensitivity of 0.67 μA μM-1 cm-2. SEM analysis of the electrodes found the Ni-BDD to be modified by a quasi-random microparticle assembly, with approximately 7.6 μg cm-2 of nickel present on the surface. © 2010 Elsevier B.V. All rights reserved.
Marsden A.J.,University of Warwick |
Phillips M.,Asylum Research UK Ltd |
Wilson N.R.,University of Warwick
Nanotechnology | Year: 2013
At a single atom thick, it is challenging to distinguish graphene from its substrate using conventional techniques. In this paper we show that friction force microscopy (FFM) is a simple and quick technique for identifying graphene on a range of samples, from growth substrates to rough insulators. We show that FFM is particularly effective for characterizing graphene grown on copper where it can correlate the graphene growth to the three-dimensional surface topography. Atomic lattice stick-slip friction is readily resolved and enables the crystallographic orientation of the graphene to be mapped nondestructively, reproducibly and at high resolution. We expect FFM to be similarly effective for studying graphene growth on other metal/locally crystalline substrates, including SiC, and for studying growth of other two-dimensional materials such as molybdenum disulfide and hexagonal boron nitride. © 2013 IOP Publishing Ltd.
Seah M.P.,National Physical Laboratory United Kingdom |
Mulcahy C.P.A.,Cascade Scientific Ltd. |
Mulcahy C.P.A.,Asylum Research UK Ltd. |
Biswas S.,Cascade Scientific Ltd.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2010
An analysis is made of the sputter depth profiling of ultrathin silicon dioxide layers on silicon to evaluate the variation in the sputtering rate in the first few nanometers. Such changes in sputtering rate are important for the development of the analysis of nanoparticles. Cs+ ions are chosen as an example of a metal ion popular in secondary ion mass spectrometry (SIMS) studies that provide excellent depth resolution. It is found that, if it is assumed that the signal is linear with oxygen content, the sputtering rate falls rapidly by a factor of 4.8, with an exponential decay near 1.2 nm when using 600 eV Cs+ ions at 60° incidence angle. The interface may be described by the integral of the response function of Dowsett developed for SIMS depth profiling of delta layers with λu =0.5 nm, λd =0.7 nm, and σ=0.4 nm, showing the excellent depth resolution. However, if published data for the nonlinearity of the signal with oxygen content are used, the rapid change is still seen but with an initial sputtering rate that is reduced from the above 4.8 to 3.5 times that at equilibrium. © 2010 American Vacuum Society.
Hancox I.,University of Warwick |
Chauhan K.V.,University of Warwick |
Sullivan P.,University of Warwick |
Hatton R.A.,University of Warwick |
And 3 more authors.
Energy and Environmental Science | Year: 2010
We report a ∼60% increase in open circuit voltage (Voc) and power conversion efficiency in a chloroaluminium phthalocyanine (ClAlPc)/fullerene (C60) planar heterojunction photovoltaic device after insertion of a MoO3 hole-extracting layer at the interface between the indium tin oxide (ITO) electrode and the ClAlPc donor layer, with an associated improvement in device stability. A similar improvement was observed in heterojunction devices based on mixed ClAlPc/C60 layers. We propose that the improvements in device performance are due to the pinning of the ITO Fermi level to the valance band of the MoO3 interlayer, where the latter is closely aligned with the highest occupied molecular orbital of ClAlPc. © 2010 The Royal Society of Chemistry.
Grant C.A.,University of Bradford |
Phillips M.A.,Asylum Research UK Ltd. |
Thomson N.H.,University of Leeds
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2012
Low frequency (0.1-2 Hz) dynamic mechanical analysis on individual type I collagen fibrils has been carried out using atomic force microscopy (AFM). Both the elastic (static) and viscous (dynamic) responses are correlated to the characteristic axial banding, gap and overlap regions. The elastic modulus (~5 GPa) on the overlap region, where the density of tropocollagen is highest, is 160% that of the gap region. The amount of dissipation on each region is frequency dependent, with the gap region dissipating most energy at the lowest frequencies (0.1 Hz) and crossing over with the overlap region at ~0.75 Hz. This may reflect an ability of collagen fibrils to absorb energy over a range of frequencies using more than one mechanism, which is suggested as an evolutionary driver for the mechanical role of type I collagen in connective tissues and organs. © 2011 Elsevier Ltd.
Agency: GTR | Branch: EPSRC | Program: | Phase: Training Grant | Award Amount: 4.28M | Year: 2014
Condensed matter physics is a major underpinning area of science and technology. For example, the physics of electrons in solids underpins much of modern technology and will continue to do so for the foreseeable future. We propose to create a Centre for Doctoral Training (CDT) which will address the national need to develop researchers equipped with the skill sets and perspective to make worldwide impact in this area. The research themes covered address some very fundamental questions in science such as the physics of superconductors, novel magnetic materials, single atomic layer crystals, plasmonic structures, and metamaterials, and also more applied topics in the power electronics, optoelectronics and sensor development fields. There are strong connections between fundamental and applied condensed matter physics. The goal of the Centre is to provide high calibre graduates with a focussed but comprehensive training programme in the most important physical aspects of these important materials, from intelligent design (first principles electronic structure calculations and modelling), via cutting-edge materials synthesis, characterisation and sophisticated instrumentation, through to identification and realisation of exciting new applications. In addition programme development will emphasise transferable skills including business & enterprise, outreach and communication. As stated in the impact section, physics-dependent businesses are of major importance to the UK economy.
Agency: GTR | Branch: Innovate UK | Program: | Phase: Collaborative Research & Development | Award Amount: 270.54K | Year: 2011
The overall aim of this project is to develop prototype low cost, lightweight organic photovoltaic (OPV) cells, exploiting our patented multi-junction cell technology which will enable power conversion efficiencies of >8% and accelerated lifetimes equivalent to at least 3 years in the field. New transparent conducting electrodes will be incorporated into the cells, eliminating the requirement for Indium Tin Oxide (ITO) and enabling the technology to overcome one of the key obstacles to low cost manufacture. New thin film deposition technology will also be developed, allowing more efficient use of materials in the fabrication process and consistent with the need to reduce costs. The prototypes will demonstrate performance characteristics compatible with subsequent scale-up to product manufacture and commercialisation in the medium term for markets such as portable solar chargers for consumer electronics and auxiliary power for automotive and building integrated applications.