Manchester, United Kingdom
Manchester, United Kingdom

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Cant D.J.H.,Photon Science Institute | Syres K.L.,Photon Science Institute | Syres K.L.,University of Nottingham | Lunt P.J.B.,Photon Science Institute | And 12 more authors.
Langmuir | Year: 2015

Nanocrystalline thin films of PbS are obtained in a straightforward reaction by precipitation at the interface between toluene (containing a Pb precursor) and water (containing Na2S). Lead thiobiuret [Pb(SON(CNiPr2)2)2] and lead diethyldithiocarbamate [Pb(S2CNEt2)2] precursors are used. The films are characterized by X-ray diffraction and electron microscopy, revealing typical particle sizes of 10-40 nm and preferred (200) orientation. Synchrotron-excited depth-profiling X-ray photoelectron spectroscopy (XPS) is used to determine the depth-dependent chemical composition as a function of surface aging in air for periods of up to 9 months. The as-synthesized films show a 1:1 Pb/S composition. Initial degradation occurs to form lead hydroxide and small quantities of surface-adsorbed -SH species. A lead-deficient Pb1-xS phase is produced as the aging proceeds. Oxidation of the sulfur occurs later to form sulfite and sulfate products that are highly localized at the surface layers of the nanocrystals. These species show logarithmic growth kinetics, demonstrating that the sulfite/sulfate layer acts to passivate the nanocrystals. Our results demonstrate that the initial reaction of the PbS nanocrystals (forming lead hydroxide) is incongruent. The results are discussed in the context of the use of PbS nanocrystals as light-harvesting elements in next-generation solar technology. © 2015 American Chemical Society.

Ahmed N.,Photon Science Institute | Vaughan J.,Photon Science Institute | Scully P.,Photon Science Institute | Stanmore E.,University of Manchester
24th International Conference on Plastic Optical Fibers, POF 2015 - Conference Proceedings | Year: 2015

Improved uptake and adherence to balance and strength exercises has been demonstrated to significantly improve functionality and reduce falls by 40%, helping people to remain independent and maintain their quality of life. Achieving this reduces the burden of illnesses such as osteoarthritis on the healthcare system. We propose a portable, inexpensive balance and lower limb strength rehabilitation device for home use with remote clinical connectivity based on polymer optical fibre (POF) technology. The device will measure balance and adherence to rehabilitation exercise, and ensure that the exercises are carried out correctly and effectively - even in the patient's own home. Measurement of pressure, using POF technology, enables simultaneous and independent monitoring of the ball and heel of each foot forming four quadrants. This economical system displays postural balance and sway analysis as a stabilogram, which combines pressures exerted on all four zones to formulate Centre of Pressure (COP) and Centre of Gravity.

Thomas A.G.,Photon Science Institute | Jackman M.J.,Photon Science Institute | Jackman M.J.,University of Manchester | Wagstaffe M.,Photon Science Institute | And 6 more authors.
Langmuir | Year: 2014

The adsorption of p-aminobenzoic acid (pABA) on the anatase TiO2(101) surface has been investigated using synchrotron radiation photoelectron spectroscopy, near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT). Photoelectron spectroscopy indicates that the molecule is adsorbed in a bidentate mode through the carboxyl group following deprotonation. NEXAFS spectroscopy and DFT calculations of the adsorption structures indicate the ordering of a monolayer of the amino acid on the surface with the plane of the ring in an almost upright orientation. The adsorption of pABA on nanoparticulate TiO2 leads to a red shift of the optical absorption relative to bare TiO2 nanoparticles. DFT and valence band photoelectron spectroscopy suggest that the shift is attributed to the presence of the highest occupied molecular orbitals in the TiO2 band gap region and the presence of new molecularly derived states near the foot of the TiO2 conduction band. © 2014 American Chemical Society.

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