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Dr Mohammed Alkhorayef


Visiting Senior Fellow

Academic and research departments

Department of Physics.

My publications

Publications

Bardi N, Jurewicz I, King A, Alkhorayef M, Bradley D, Dalton A (2017) X-ray irradiation-induced structural changes on Single Wall Carbon Nanotubes,Radiation Physics and Chemistry 140 pp. 34-37 Elsevier
Dosimetry devices based on Carbon Nanotubes are a promising new technology. In particular using devices based on single wall carbon nanotubes may offer a tissue equivalent response with the possibility for device miniaturisation, high scale manufacturing and low cost. An important precursor to device fabrication requires a quantitative study of the effects of X-ray radiation on the physical and chemical properties of the individual nanotubes. In this study, we concentrate on the effects of relatively low doses, 20 cGy and 45 cGy, respectively. We use a range of characterization techniques including scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to quantify the effects of the radiation dose on inherent properties of the nanotubes. Specifically we find that the radiation exposure results in a reduction in the sp2 nature of the nanotube bond structure. Moreover, our analysis indicates that the exposure results in nanotubes that have an increased defect density which ultimately effects the electrical properties of the nanotubes.
Garriga R, Jurewicz Izabela, Seyedin S, Bardi Niki, Totti Styliani, Matta? Domjan B, Velliou Eirini, Alkhorayef Mohammed, Cebolla VL, Razal JM, Dalton Alan, Muñoz E (2017) Multifunctional, Biocompatible and pH-Responsive Carbon Nanotube- and Graphene Oxide/Tectomer Hybrid Composites and Coatings,Nanoscale 9 pp. 7791-7804 Royal Society of Chemistry
Here we present a route for non?covalent functionalization of carboxylated multi?wall carbon nanotubes and graphene oxide with novel two?dimensional peptide assemblies. We show that self?assembled amino?terminated biantennary and tetraantennary oligoglycine peptides (referred to as tectomers) effectively coat carboxylated multi?walled carbon nanotubes and also strongly interact with graphene oxide due to electrostatic interactions and hydrogen bonding as the driving force, respectively. The resulting hybrids can be made into free?standing conducting composites or applied in the form of thin, pH?switchable bioadhesive coatings onto graphene oxide fibers. Monitoring of cell viability of pancreatic cell lines, seeded on those CNT hybrids, show that they can be used as two? and three?dimensional scaffolds to tissue engineer tumour models for studying ex vivo the tumour development and response to treatment. This highly versatile method in producing pH?responsive hybrids and coatings offers an attractive platform for a variety of biomedical applications and for the development of functional materials such as smart textiles, sensors and bioelectronic devices.
Abdul Sani S, Hammond R, Jafari S, Wahab N, Amouzad Mahdiraji G, Siti Shafiqah A, Abdul Rashid H, Maah M, Aldousari H, Alkhorayef M, Alzimami M, Bradley D (2016) Measurement of a wide-range of X-ray doses using specialty doped silica fibres,Radiation Physics and Chemistry 137 pp. 49-55 http://www.elsevier.com/
Using six types of tailor-made doped optical fibres, we carry out thermoluminescent (TL) studies of X-rays, investigating the TL yield for doses from 20 mGy through to 50 Gy. Dosimetric parameters were investigated for nominal 8 wt% Ge doped fibres that in two cases were co-doped, using B in one case and Br in the other. A comparative measurement of surface analysis has also been made for non-annealed and annealed capillary fibres, use being made of X-ray Photoelectron Spectroscopy (XPS) analysis. Comparison was made with the conventional TL phosphor LiF in the form of the proprietary product TLD-100, including dose response and glow curves investigated for X-rays generated at 60 kVp over a dose range
from 2 cGy to 50 Gy. The energy response of the fibres was also performed for X-rays generated at peak
accelerating potentials of 80 kVp, 140 kVp, 250 kVp and 6 MV photons for an absorbed dose of 2 Gy. Present results show the samples to be suitable for use as TL dosimeters, with good linearity of response and a simple glow curve (simple trap) distribution. It has been established that the TL performance of an irradiated fibre is not only influenced by radiation parameters such as energy, dose-rate and total dose but also the type of fibre.