Browsing by Author "Gomez, Virginia"

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    Bi-Phasic photocatalytic particles prepared by sequential layer depositions for water cleaning and purification
    (One Central Press, 2016) Gomez, Virginia; Rome, Bertrand; Barron, Andrew R.; Dunnill, Charles W.
    Bi-phasic photocatalyic particles have been prepared in the form of Janus-like structures (bi-phasic materials with two distinct properties on opposing sides of the particle) using a new synthetic procedure consisting of the sequential layer depositions of semiconductor oxide materials onto soluble substrates. A number of different systems have to date been investigated with an aim of photocatalytic applications. A general synthetic regime consists of utilising simple sol-gel chemistry to deposit sequential layers of photocatalytic material on top of a soluble substrate. The substrate can subsequently be removed yielding extremely fragile disks that fracture into bi-phasic powders of Janus like particles. These particles have two unique sets of properties contained in different faces of the same particle, aimed at the simultaneous reduction and oxidation of toxic species in water. This new synthetic technique is investigated for photocatalyic applications with an eye to efficient water purification, utilising the synergistic effect of the two materials to create highly effective photocatalysts. The photocatalytic activity of anatase/rutile (TiO2) bi-phasic nanoparticle composites enhanced with platinum and deposited on the surface of polycarbonate filters has been successfully demonstrated. Deposition of the photocatalyst on filters overcomes expensive and time consuming recycling processes, adds porosity to the set up and reduces the scattering of nanoparticle dispersions.
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    Carboxylation and Decarboxylation of Aluminum Oxide Nanoparticles Using Bifunctional Carboxylic Acids and Octylamine
    (Hindawi, 2016) Alexander, Shirin; Gomez, Virginia; Barron, Andrew R.
    The carboxylation of alumina nanoparticles (NPs), with bifunctional carboxylic acids, provides molecular anchors that are used for building more complexed structures via either physisorption or chemisorption. Colloidal suspensions of the NPs may be prepared by covalently bonding a series of carboxylic acids with secondary functional groups (HO2C-R-X) to the surface of the NPs: lysine (X = NH2), p-hydroxybenzoic acid (X = OH), fumaric acid (X = CO2H), and 4-formylbenzoic acid (X = C(O)H). Subsequent reaction with octylamine at either 25°C or 70°C was investigated. Fourier transform IR-attenuated reflectance spectroscopy (FTIR-ATR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) along with energy dispersive X-ray (EDX) analysis were used to characterize the bifunctionalized monolayers and/or multilayer corona surrounding the alumina NPs and investigate the reaction mechanism of octylamine with the functional groups (X) of the NPs. Except for the fumaric functionalized NPs, addition of octylamine to the functionalized NPs leads to removal of excess carboxylic acid corona from the surface via an amide formation. The extent of the multilayer is dependent on the strength of the acid⋯acid interaction.
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    Surface-initiated growth of copper using isonicotinic acid-functionalized aluminum oxide surfaces
    (Springer, 2016) Gowenlock, Cathren E.; Gomez, Virginia; McGettrick, James D.; Andreoli, Enrico; Barron, Andrew R.
    Isonicotinate self-assembled monolayers (SAM) were prepared on alumina surfaces (A) using isonicotinic acid (iNA). These functionalized layers (iNA-A) were used for the seeded growth of copper films (Cu-iNA-A) by hydrazine hydrate-initiated electroless deposition. The films were characterized by scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and advancing contact angle measurements. The films are Cu0 but with surface oxidation, and show a faceted morphology, which is more textured (Rq = 460 ± 90 nm) compared to the SAM (Rq = 2.8 ± 0.5 nm). In contrast, growth of copper films by SnCl2/PdCl2 catalyzed electroless deposition, using formaldehyde (CH2O) as the reducing agent, shows a nodular morphology on top of a relatively smooth surface. No copper films are observed in the absence of the isonicotinate SAM. The binding of Cu2+ to the iNA is proposed to facilitate reduction to Cu0 and create the seed for subsequent growth. The films show good adhesion to the functionalized surface.