Declan McCormack - Academia.edu (original) (raw)

Papers by Declan McCormack

Journal of Coatings Technology and Research, 2016

Applied Surface Science, 2016

An efficient, rapid and straightforward method for the preparation of nitrogen and fluorine (N, F... more An efficient, rapid and straightforward method for the preparation of nitrogen and fluorine (N, F) codoped high temperature stable anatase using a microwave pre-treatment is reported. Using a single source, ammonium fluoride (NH4F) for both nitrogen and fluorine, effective doping of the precursor titanium isopropoxide (TTIP) was possible. These samples were characterised for their structural and optical properties using X-ray diffraction (XRD), Fourier transform IR (FTIR), Raman spectroscopy and UV-vis spectroscopy. In terms of the anatase to rutile transition enhancement using a novel microwave assisted technique, the sample prepared in a composition Fagan et al, Applied Surface Science 371, 2016, 447-452 of 1:8 TiO2: NH4F at 1200 °C was seen to be most effective, having stable anatase present at 57.1 % compared to undoped TiO2 being 100 % rutile from 900 °C. This method involves the production of ammonium oxofluorotitanates (NH4TiOF3) at low temperatures. The inclusion of these intermediates greatly reduces the particle size growth and delays the anatase to rutile transition. The photocatalytic activity of these materials was studied by analysing the degradation of an organic dye, rhodamine 6G as a model system and the rate constant was calculated by pseudo-first-order kinetics. These results showed that the doped sample (0.0225 min-1) was three times more active than the undoped sample (0.0076 min-1) and over seven times faster than the commercial TiO2 photocatalyst standard Degussa P-25 calcined at 1200 °C (0.0030 min-1). The formation of intermediate compounds, oxofluorotitanates, was identified as the major reason for a delay in the anatase to rutile transition.

Materials, 2016

Graphitic carbon nitride (g-C 3 N 4) and titanium dioxide (TiO 2) were chosen as a model system t... more Graphitic carbon nitride (g-C 3 N 4) and titanium dioxide (TiO 2) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g-C 3 N 4 has been shown to be effective in the reduction in recombination through the interaction between the two interfaces of TiO 2 and g-C 3 N 4. A simple method of preparing g-C 3 N 4 through the pyrolysis of melamine was employed, which was then added to undoped TiO 2 material to form the g-C 3 N 4-TiO 2 system. These materials were then fully characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), and various spectroscopic techniques including Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), diffuse absorbance, and photoluminescence analysis. Photocatalysis studies were conducted using the model dye, rhodamine 6G utilizing visible and UV light irradiation. Raman spectroscopy confirmed that a composite of the materials was formed as opposed to a mixture of the two. Using XPS analysis, a shift in the nitrogen peak to that indicative of substitutional nitrogen was detected for all doped samples. This is then mirrored in the diffuse absorbance results, which show a clear decrease in band gap values for these samples, showing the effective band gap alteration achieved through this preparation process. When g-C 3 N 4-TiO 2 samples were analyzed under visible light irradiation, no significant improvement was observed compared that of pure TiO 2. However, under UV light irradiation conditions, the photocatalytic ability of the doped samples exhibited an increased reactivity when compared to the undoped TiO 2 (0.130 min´1), with 4% g-C 3 N 4-TiO 2 (0.187 min´1), showing a 43.9% increase in reactivity. Further doping to 8% g-C 3 N 4-TiO 2 lead to a decrease in reactivity against rhodamine 6G. BET analysis determined that the surface area of the 4% and 8% g-C 3 N 4-TiO 2 samples were very similar, with values of 29.4 and 28.5 m 2 /g, respectively, suggesting that the actual surface area is not a contributing factor. This could be due to an overloading of the system with covering of the active sites resulting in a lower reaction rate. XPS analysis showed that surface hydroxyl radicals and oxygen vacancies are not being formed throughout this preparation. Therefore, it can be suggested that the increased photocatalytic reaction rates are due to successful interfacial interactions with the g-C 3 N 4-doped TiO 2 systems.

Coatings that demonstrate reduced attachment of crystalline precipitates and the medical device c... more Coatings that demonstrate reduced attachment of crystalline precipitates and the medical device colonising Staphylococcus epidermidis were prepared by the immobilisation of silver doped perfluoropolyether-urethane siloxane thin films on glass substrates. The presence of stratified hydrophobic perfluoropolyether groups protects the coating surface from the attachment of crystalline hydrophilic species such as chlorides and phosphates, whilst silver ion release inhibited attachment of S. epidermidis and subsequent biofilm formation in vitro. The release of silver ions protects the perfluoro groups from the hydrophobic interactions of S. epidermidis cells, which can reduce the hydrophobicity of the protective coating. These coatings also exhibited significant antibacterial activity against planktonic Acinetobacter baumannii and S. epidermidis bacterial strains. Detailed elemental and chemical surface analysis obtained using X-ray photoelectron spectroscopy (XPS) provided useful information on the effect of bacterial incubation on key indicator hydrophobic and hydrophilic functional groups. XPS analysis indicated preferential adsorption of S. epidermidis cells at the hydrophobic sites along the polymeric chain. These dual-action hygienic coatings can be employed to protect against contamination environmental surfaces and bacterial colonisation on implanted medical devices.

Journal of Hazardous Materials, 2015

Key Engineering Materials, 1992

Materials Science and Technology, 2004

ZnO nanoparticles were prepared by a solid state pyrolysis reaction of zinc acetate dihydrate and... more ZnO nanoparticles were prepared by a solid state pyrolysis reaction of zinc acetate dihydrate and oxalic acid dihydrate at 500uC. The course of reaction at various temperatures was followed by XRD. Subsequently varistors were fabricated from this nano-ZnO material by solid state mixing with various oxide additives and sintering to 1050uC. The microstructure of the sintered material was studied using XRD, field emission SEM (FESEM), and EDX, and ZnO grains, bismuth rich regions and spinel phases were identified. Discs made from oxide doped nano-ZnO show considerably higher breakdown voltage (656¡30 V mm 21) compared to those prepared from micrometre sized ZnO (410¡30 V mm 21) and commercial varistors (454¡30 V mm 21). However, varistors made from the nano-ZnO show very low densification and high leakage current, making them unsuitable for device fabrication. MST/6097

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1991

Faraday Discussions of the Chemical Society, 1989

Analytical expressions quantifying the transport and kinetics in polymer-modified electrodes cont... more Analytical expressions quantifying the transport and kinetics in polymer-modified electrodes containing a homogeneous distribution of spherical microparticulate catalysts are presented. In particular the dependence of the flux on the number of catalytic particles per unit ...

Analytical Proceedings, 1991

... Michael EG Lyons, Cormac H. Lyons, Declan E. McCormack,&amp;quot; Thomas J. McCabe an... more ... Michael EG Lyons, Cormac H. Lyons, Declan E. McCormack,&amp;quot; Thomas J. McCabe and William Breen* Physical Chemistry Laboratory, University of Dublin, Trinity College, Dublin 2, Ireland John F. Cassidy Chemistry Department, Dublin Institute of Technology, Kevin Street ...

Journal of Materials Chemistry C, 2013

ZnO based varistors are widely used for overvoltage protection in many electrical and electronic ... more ZnO based varistors are widely used for overvoltage protection in many electrical and electronic circuits, at voltages ranging from a few to over a million volts. By careful control of the microstructure, through nanostructuring by chemical routes, it should be possible to produce varistors with high breakdown voltage (V c), as this is proportional to the number of active grain boundaries in the sintered body. This property is particularly important for the production of the small-sized varistors needed for modern electronic instruments such as tablet computers and mobile phones. The current review will outline the recent advances in the chemical processing (e.g. sol-gel, combustion synthesis plasma pyrolysis, micro-emulsion synthesis and precipitation routes) of varistors from ZnO nanomaterials and the properties of these materials. Uncontrolled grain growth at higher temperature is highlighted as a major challenge for obtaining desirable electrical properties for nano-varistors. Various novel sintering techniques such as step-sintering, spark plasma and microwave sintering methods are expected to deliver a varistor with controlled grain growth and optimum electrical characteristics.

Smart Materials and Structures, 2007

The synthesis of zinc oxide through the decomposition of a solid oxalate precursor was investigat... more The synthesis of zinc oxide through the decomposition of a solid oxalate precursor was investigated. It was found that the rate of preparation of the precursor had a quantitative effect on the morphology and extent of surface ligation of particles produced; contrary to our expectations, it was found that the slow combination of reagents led to a less pure product. It has been determined that this time dependence mimics the variation of reactant ratios. Zinc oxide particles were produced from a number of reactant ratios, and were characterised by TEM, XRD, FT-IR and DSC. It was found that the size of the crystallites produced was not affected, but that the nature of their surface ligation did rely upon these parameters.

Polymer, 1990

Absorption spectra, luminescence spectra and excited-state lifetimes of uranyl ions (UO 2 +) inco... more Absorption spectra, luminescence spectra and excited-state lifetimes of uranyl ions (UO 2 +) incorporated in Nation or Flemion membranes have been studied as a function of hydration. Marked changes in the nature of the spectra and emission lifetime are observed. Thus at 291 K the lifetime changes from 2.0#s in a water-swollen Nation membrane to 640#s in a thoroughly dried sample. The lifetime of the dried sample is temperature-invariant, whereas those of heavily hydrated samples show activation energies of 30 + 2 kJ mol-a, suggesting that water plays a key role in the excited-state deactivation. A changeover in the decay mechanism is found for samples of intermediate water content. Energy transfer from excited UO 2+ to Eu 3 + is observed, the effect being enhanced by membrane dehydration and being much more pronounced for Flemion membranes than for Nation. Treatment of the UO 2 ÷-containing membranes with aqueous KOH causes the formation of products concentrated near the membrane surface. The absorption spectra, luminescence spectra and X-ray diffraction of these materials have been compared with those of the oxides and uranates formed in solutions of various pH. Transmission electron microscopy reveals particles of less than 1 pm in size.

Materials Letters, 2014

In this work, the antimicrobial properties of vertically aligned nano-tubular Cu arrays (NT-Cu) f... more In this work, the antimicrobial properties of vertically aligned nano-tubular Cu arrays (NT-Cu) fabricated via a template-based electrodeposition approach were investigated. The NT-Cu display good bactericidal activity against S.aureus and bacteriostatic properties against E.coli, S.sonnei, S.enterica and C.albicans. In contrast, Cu-foil electrodeposited from the same solution

Journal of Materials Chemistry, 2010

The fabrication of paper quality electrochromic displays based on the viologen modified TiO 2 ele... more The fabrication of paper quality electrochromic displays based on the viologen modified TiO 2 electrodes (Vio 2+ /TiO 2) requires a cost-effective, energy efficient and rapid synthesis of mesoporous TiO 2 with high yield in short reaction time. A straightforward and industrially viable process for the preparation of mesoporous nanocrystalline titania (meso-nc-TiO 2) for NanoChromicsÔ display device applications by the use of microwave synthesis is presented here. Spherical aggregates of meso-nc-TiO 2 were rapidly achieved using titanium butoxide, deionised water and common alcohols (isopropanol, ethanol and butanol) at comparatively low microwave power intensity (300 W) for 2 min irradiation. The material has been characterised by a range of different techniques such as XRD, Raman spectroscopy, SEM and BET surface area analysis. These materials possess surface areas up to 240 m 2 g À1 , which is significantly higher than similar traditional sol-gel or commercial samples. This meso-nc-TiO 2 prepared was used as the working electrode for an electrochromic display device with Sb doped SnO 2 as the counter electrode material on an ITO coated conducting glass. A working prototype of a NanoChromicsÔ display was successfully fabricated using this approach.

Journal of Materials Chemistry, 2008

An industrially viable solution-based processing route using minimal amounts of solvent has been ... more An industrially viable solution-based processing route using minimal amounts of solvent has been used to prepare bulk quantity nanopowders (average particle size 15 AE 3 nm) for the fabrication of ZnO varistors. The xerogels, calcined powders and sintered materials were fully characterised. The preparation of varistors from nanopowders has been optimised by studying the effect of temperature on grain growth, densification and breakdown voltage. The varistors are prepared by sintering at 1050 C for 2 hours, a temperature that is significantly lower than that used in the current industrial process. Highly dense varistor discs prepared from the sintered material produce devices, with a breakdown voltage 85% higher than that of commercial varistors, making them suitable for use in miniaturised electronic circuitry. Improved performance of these materials has been attributed to the small grain size and better dispersion of additives on ZnO grains.

Journal of Materials Chemistry, 2007

Journal of Materials Chemistry, 2009

The microwave (MW)-assisted formation of ZnO micro-javelins from zinc nitrate and urea in aqueous... more The microwave (MW)-assisted formation of ZnO micro-javelins from zinc nitrate and urea in aqueous solution is described. The particles (named as 'micro-javelins' because of their high aspect ratio and needle-like tips) grow hexagonally with well-defined facets in the h01 10i direction and pointed tips in (0001) direction. Powder X-ray diffraction patterns show the appearance of a strikingly dominant (1000) orientation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations reveal the morphological evolution of these hexagonal ZnO particles with time. The effect of precursor concentrations, counterion type and MW irradiation power and their consequent influence on pH and Zn 2+ ion concentration are investigated. A mechanism for the formation of the micro-javelins is postulated. The microwave induced supersaturation of Zn(OH) + species under the weakly basic pH condition and the initial growth through the (000 1) direction (oxygen-rich face) are proposed to be the key factors that dictate the formation of these ZnO micro-javelins. The present one-step microwave process is a straightforward and a reproducible method for the bulk synthesis of defect-free ZnO micro-javelins, which would find potential applications in microelectronic devices (e.g. lasers, cantilevers in surface probing equipment, etc.).

Journal of Materials Chemistry, 2003

The morphology of the microcrystalline zinc oxide formed by reaction of zinc salts with sodium hy... more The morphology of the microcrystalline zinc oxide formed by reaction of zinc salts with sodium hydroxide depends critically on the reaction conditions. To understand this, the nature of the solid product has been probed by scanning electron microcopy (SEM) and X-ray diffraction (XRD) and the concentration of zinc remaining in the solution has been determined at regular intervals throughout the reaction. Two general preparative procedures have been followed. The first, which involves simply heating an aqueous solution containing Zn(NO 3) 2 (0.025 M) and sodium hydroxide (0.375 M) to 101 uC and maintaining it at that temperature for periods of up to 8 hours, produces star-like microcrystals. The star-like morphology is apparently caused by multiple crystal twinning at the onset of growth, and the size and shape of the microcrystals have been found to be affected by both the reaction stoichiometry and the type of zinc salt counterion. In the second method, which produces needles of zinc oxide (lengths up to 6 mm ;-aspect ratio w6), the reagents are stirred at room temperature for two hours before heating the mixture to 101 uC and maintaining it at that temperature for up to 24 hours. Pre-stirring allows the formation of Zn(OH) 2 , which is shown by XRD and SEM to transform to ZnO upon heating.