Browsing by Author "Clark, M."

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    Highly sensitive optical fibre long period grating biosensor anchored with silica core gold shell nanoparticles
    (Elsevier, 2015-08-22) Marques, L.; Hernandez, F. U.; James, Stephen W.; Morgan, S. P.; Clark, M.; Tatam, Ralph P.; Korposh, Sergiy
    An optical fibre long period grating (LPG), modified with a coating of silica core gold shell (SiO2:Au) nanoparticles (NPs) deposited using the layer-by-layer method, was employed for the development of a biosensor. The SiO2:Au NPs were electrostatically assembled onto the LPG with the aid of a poly(allylamine hydrochloride) (PAH) polycation layer. The LPG sensor operates at the phase matching turning point to provide the highest sensitivity. The SiO2:Au NPs were modified with biotin, which was used as a ligand for streptavidin (SV) detection. The sensing mechanism is based on the measurement of the refractive index change induced by the binding of the SV to the biotin. The effect on sensitivity of increasing the surface area by virtue of the SiO2:Au nanoparticles’ diameter and film thickness was studied. The lowest measured concentration of SV was 2.5 nM, achieved using an LPG modified with a 3 layer (PAH/SiO2:Au) thin film composed of SiO2 NPs of 300 nm diameter with a binding constant of View the MathML sourcek=1.7(pM)-1, sensitivity of View the MathML source6.9nm/ng/mm2 and limit of detection of 19 pg/mm2.
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    Novel highly sensitive protein sensors based on tapered optical fibres modified with Au-based nanocoatings
    (Hindawi Publishing Corporation, 2016-08-08) Urrutia, Aitor; Bojan, Kartheka; Marques, L.; Mullaney, Kevin; Goicoechea, Javier; James, Stephen W.; Clark, M.; Tatam, Ralph P.; Korposh, Sergiy
    In this work, novel protein sensors based on tapered optical fibres modified with Au coatings deposited using two different procedures are proposed. Au based coatings are deposited onto a non-adiabatic tapered optical fibre using: (i) a novel facile method composed of layer-by-layer deposition consisting of polycation (poly(allylamine hydrochloride), PAH) and negatively charged SiO2 nanoparticles (NPs) followed by the deposition of the charged Au NPs; and (ii) the sputtering technique. The Au NPs and Au thin film surfaces are then modified with biotin in order to bind Streptavidin (SV) molecules and detect them. The sensing principle is based on the sensitivity of the transmission spectrum of the device to changes in the refractive index of the coatings induced by the SV binding to the biotin. Both sensors, showed high sensitivity to SV, with the lowest measured concentration levels below 2.5 nM. The calculated binding constant for the biotin-SV pair was 2.2 x10-11 M-1 when a tapered fibre modified with the LbL method was used, with a Limit of Detection (LoD) of 271 pM. The sensor formed using sputtering had a binding constant of 1.01x10-10 M-1 with a LoD of 806 pM. These new structures and their simple fabrication technique could be used to develop other bio-sensors.
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    A review of literature and computer models on exposure assessment
    (Taylor & Francis, 2009-12-31T00:00:00Z) Butt, T. E.; Clark, M.; Coulon, Frederic; Oduyemi, K. O. K.
    At the present time, risk analysis is an effective management tool used by environmental managers to protect the environment from inevitable anthropogenic activities. There are generic elements in environmental risk assessments, which are independent of the subject to which risk analysis is applied. Examples of these elements are: baseline study, hazard identification, hazards' concentration assessment and risk quantification. Another important example of such generic elements is exposure assessment, which is required in a risk analysis process for landfill leachate as it would in any other environmental risk issue. Furthermore, computer models are also being developed to assist risk analysis in different fields. However, in the review of current computer models and literature, particularly regarding landfills, the authors have found no evidence for the existence of a holistic exposure assessment procedure underpinned with a computational method for landfill leachate. This paper, with reference to the relevant literature and models reviewed, discusses the extent to which exposure assessment is absent in landfill risk assessment approaches. The study also indicates a number of factors and features that should be added to the exposure assessment system in order to render it more strategic, thereby enhancing the quantitative risk analysis.
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    Sensitive protein detection using an optical fibre long period grating sensor anchored with silica core gold shell nanoparticles
    (SPIE, 2014-12-31) Marques, L.; Hernandez, F. U.; Korposh, Sergiy; Clark, M.; Morgan, S. P.; James, Stephen W.; Tatam, Ralph P.
    An optical fibre long period grating (LPG), modified with a coating of silica gold (SiO2:Au) core/shell nanoparticles (NPs) deposited using the layer-by-layer (LbL) method, was employed for the development of a bio-sensor. The SiO2:Au NPs were electrostatically assembled onto the LPG with the aid of a poly(hydrochloride ammonium) (PAH) polycation layer. The LPG sensor operates at the phase matching turning point to provide the highest sensitivity. The SiO2:Au NPs were modified with biotin, which was used as a ligand for streptavidin (SV) detection. The sensing mechanism is based on the measurement of the refractive index change induced by the binding of the SV to the biotin. The lowest detected concentration of SV was 19 nM using an LPG modified with a 3 layer (PAH/SiO2:Au) thin film.