Browsing by Author "Uedono, A"

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    Investigating the binding properties of porous drug delivery systems using nuclear sensors (radiotracers) and positron annihilation lifetime spectroscopy – predicting conditions for optimum performance
    (Royal Society Chemistry, 2011-01-01) Mume, E; Lynch, DE; Uedono, A; Smith, SV
    Understanding how the size, charge and number of available pores in porous material influences the uptake and release properties is important for optimising their design and ultimately their application. Unfortunately there are no standard methods for screening porous materials in solution and therefore formulations must be developed for each encapsulated agent. This study investigates the potential of a library of radiotracers (nuclear sensors) for assessing the binding properties of hollow silica shell materials. Uptake and release of Cu2+ and Co2+ and their respective complexes with polyazacarboxylate macrocycles (dota and teta) and a series of hexa aza cages (diamsar, sarar and bis-(p-aminobenzyl)-diamsar) from the hollow silica shells was monitored using their radioisotopic analogues. Coordination chemistry of the metal (M) species, subtle alterations in the molecular architecture of ligands (Ligand) and their resultant complexes (M-Ligand) were found to significantly influence their uptake over pH 3 to 9 at room temperature. Positively charged species were selectively and rapidly (within 10 min) absorbed at pH 7 to 9. Negatively charged species were preferentially absorbed at low pH (3 to 5). Rates of release varied for each nuclear sensor, and time to establish equilibrium varied from minutes to days. The subtle changes in design of the nuclear sensors proved to be a valuable tool for determining the binding properties of porous materials. The data support the development of a library of nuclear sensors for screening porous materials for use in optimising the design of porous materials and the potential of nuclear sensors for high through-put screening of materials. © 2011, Royal Society of Chemistry
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    Metal ion binding properties of novel wool powders
    (Wiley-Blackwell, 2010-02-05) Naik, R; Wen, G; Dharmaprakash, MS; Hureau, S; Uedono, A; Wang, XG; Liu, XG; Cookson, PG; Smith, SV
    Wool fibres have shown potential for the removal and recovery of toxic chemical and metal ions; however, their slow kinetics of binding has limited their widespread application. In this study three wool powders have been prepared from chopped wool fibre using various milling operations. Brunauer, Emmett, Teller analysis (BET) showed negligible change in surface area and Positron annihilation lifetime spectroscopy indicated no change in nanoporosity of the powders on processing. Binding of the transition metal ions, Co2+, Cu2+, and Cd2+ was investigated over the pH range 3-9 at ambient temperature (23°C) using their respective radioisotopes (i.e. 57Co, 64Cu, or 109Cd). The optimum pH for binding of Cu2+ and Cd2+ was in the range 6-8, while Co2+ absorption peak was sharp at pH 8. The rate of uptake of Cu2+ for each of the wool powder was dramatically faster (42 fold) than that of the wool fibre. In comparison with commercial cation exchange resins, the wool powders showed significantly higher (two to nine fold) metal ion loading capacity. Selective binding of the metal ions could be enhanced by varying pH and/or incubation times. The use of radioisotopes to monitor the metal ion binding allowed the development of a highly sensitive and rapid high-throughput analysis method for assessing wool powder binding properties. The ability to produce large quantities of wool powders and their ease of handling indicate that they have potential for application in separation and recovery of metal ions from industrial effluents and environmental waterways. © 2010, Wiley-Blackwell. The definitive version is available at www3.interscience.wiley.com
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    Role of positron annihilation lifetime studies and nuclear sensors for characterising porous materials
    (Institute of Physics, 2010-08-01) Mume, E; Uedono, A; Mizunaga, G; Lynch, DE; Smith, SV
    A series of nuclear sensors were designed to assess the chemistry within the nanopores of a porous material. The nuclear sensors of varying size, charge, and hydrophobicity were exposed to hollow silica shells (HSS) at varying pH. Uptake and release kinetics were studied over a 24 h period at room temperature. Preliminary study indicate positively charged nuclear sensors were selectively and rapidly (within 10 min) absorbed by the HSS at pH 7 to 9. PALS showed there were two types of pores (1.7 and 0.7 nm) present. The data suggest the nuclear sensors sit within the larger pore of the HSS. Both PALS and nuclear sensors are required to obtain an accurate insight into the nanoporosity of the hollow silica shells.
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    Understanding the effect of nanoporosity on optimizing the performance of self-healing materials for anti-corrosion applications
    (IOP Publishing, 2011-01-01) Sellaiyan, S; Smith, SV; Hughes, AE; Miller, A; Jenkins, DR; Uedono, A
    The chromate-based epoxy primer film was prepared on glass and metal surfaces using various graded doctor blades. The quality and consistency of the films was assessed using scanning electron microscopy and the porosity within the film characterized by positron annihilation lifetime spectroscopy. The positron lifetime (τ) distribution for the epoxy polymer matrix was resolved using the CONTIN program. The free volume was found from the ortho-positronium component. The optimum thickness for the films was established for future structure/activity studies. © 2014 IOP Publishing LTD
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    Using x-ray tomography, PALS and Raman spectroscopy for characterization of inhibitors in epoxy coatings
    (Elsevier, 2012-08) Hughes, AE; Mayo, SC; Yang, YS; Markley, T; Smith, SV; Sellaiyan, S; Uedono, A; Hardin, SG; Muster, TH
    Model paint materials were generated by adding a range of inorganic materials into an epoxy. The inorganic materials included inhibitors (Zn3(PO4)2 and SrCrO4) and a filler (rutile TiO2).The SrCrO4 system was characterized using SEM, TEM, PALS and Raman spectroscopy and found to have an even distribution of inhibitor in the polymer matrix. X-ray tomography was performed on the mixed SrCrO4/TiO2 and Zn3(PO4)2/TiO2 systems. A new technique called data constrained modelling was combined with the tomographic technique to produce a 3D distribution of the inorganic phases within the polymer matrix. © 2011 Elsevier B.V.