Materials Chemistry Commons^™

A Highly Efficient Tio2-Xcx Nano-Heterojunction Photocatalyst For Visible-Light Induced Antibacterial Applications, Vinodkumar Etacheri, Michael Seery, Stephen Hinder, Georg Michlits, Suresh Pillai

Articles

Visible-light-induced antibacterial activity of carbon-doped anatase-brookite titania nano-heterojunction photocatalysts are reported for the first time. These heterostructures were prepared using a novel low temperature (100 °C) non-hydrothermal low power microwave (300 W) assisted method. Formation of interband C 2p states was found to be responsible for the band gap narrowing of the carbon doped heterojunctions. The most active photocatalyst obtained after 60 minutes of microwave irradiation exhibits a 2-fold higher visible-light induced photocatalytic activity in contrast to the standard commercial photocatalyst Evonik-Degussa P-25. Staphylococcus aureus inactivation rate constant for carbon-doped nano-heterojunctions and the standard photocatalyst was 0.0023 and -0.0081 min …

The Bench Synthesis Of Silver Nanostructures Of Variable Size And An Introductory Analysis Of Their Optical Properties, Aoife Power, Tony Betts, John Cassidy

Articles

A laboratory practical was designed for use by both undergraduate and second level students to demonstrate the synthesis and characterisation of tuneable silver colloids. It clearly illustrates the novel optical properties of silver nanoparticles compared to the bulk metal. The synthesis is both rapid and repeatable, and can be conducted on the laboratory bench at room temperature.

Synthesis And Modification Of Octafluoro[2.2]Paracyclophane (Parylene Af4), Craig Hicks, Brendan Duffy, Gráinne Hargaden

Articles

Parylenes are a class of organic compounds which have gained significant attention due to their application as coatings in areas such as medical devices and electronics. This review highlights the development of synthetic pathways to Octafluoro[2.2]Paracyclophane, commonly referred to as parylene AF4. Methods which have been used to functionalise AF4 are also presented.

Novel Microwave Assisted Synthesis Of Zns Nanomaterials, Suresh Pillai, Michael Seery, Damian Synnott, John Colreavy, Stephen Hinder

Articles

A novel ambient pressure microwave-assisted technique is developed in which silver and indium modified ZnS is synthesised. The as prepared ZnS is characterised by X-ray diffraction, UV-Vis spectroscopy, X-ray photoelectron spectroscopy and luminescence spectroscopy. This procedure produced crystalline materials with particle sizes below 10 nm. The synthesis technique leads to defects in the crystal which induce mid energy levels in the band gap and lead to indoor light photocatalytic activity. Increasing the amount of silver causes a phase transition from cubic blende to hexagonal phase ZnS. In a comparative study, when the ZnS cubic blende is heated in a conventional …

A Review On The Visible Light Active Titanium Dioxide Photocatalysts For Environmental Applications, Miguel Pelaez, Nicholas Nolan, Suresh Pillai, Michael Seery, Polycarpos Falaras, Athanassios G. Kontos, Patrick S.M. Dunlop, Jeremy W.J. Hamiltone, J. Anthony Byrne, Kevin O’Shea, Mohammad H. Entezari, Dionysios D. Dionysiou

Articles

Development of visible light active (VLA) titania photocatalysts

Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO 2) semiconductor mate-rials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applica-tions. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 struc-ture, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization …

Stiefel And Grassmann Manifolds In Quantum Chemistry, Eduardo Chiumiento, Michael Melgaard

Articles

We establish geometric properties of Stiefel and Grassmann manifolds which arise in relation to Slatertype variational spaces in many-particle Hartree-Fock theory and beyond. In particular, we prove thatthey are analytic homogeneous spaces and submanifolds of the space of bounded operators on the single-particle Hilbert space. As a by-product we obtain that they are complete Finsler manifolds. These geometric properties underpin state-of-the-art results on existence of solutions to Hartree-Fock type equations.

Preparation And Rapid Analysis Of Antibacterial Silver, Copper And Zinc Doped Sol–Gel Surfaces, Brendan Duffy, Swarna Jaiswal, Patrick Mchale

Articles

The colonisation of clinical and industrial surfaces with microorganisms, including antibiotic-resistant strains, has promoted increased research into the development of effective antibacterial and antifouling coatings. This study describes the preparation of metal nitrate (Ag, Cu, Zn) doped methyltriethoxysilane (MTEOS) coatings and the rapid assessment of their antibacterial activity using polyproylene microtitre plates. Microtitre plate wells were coated with different volumes of liquid sol–gel and cured under various conditions. Curing parameters were analysed by thermogravimetric analysis (TGA) and visual examination. The optimum curing conditions were determined to be 50–70C using a volume of 200ul. The coated wells were challenged with Gram-positive …

Existence Of A Minimizer For The Quasi-Relativistic Kohn-Sham Model, Carlos Argáez García, Michael Melgaard

Articles

We study the standard and extended Kohn-Sham models for quasi-relativistic N-electron Coulomb systems; that is, systems where the kinetic energy of the electrons is given by the quasi-relativistic operator (see article) . For spin-unpolarized systems in the local density approximation, we prove existence of a ground state (or minimizer) provided that the total charge Z of K nuclei is greater than N-1 and that Z is smaller than a critical charge (see article).

Preparation And Characterization Of A Composite Of Gold Nanoparticles And Single-Walled Carbon Nanotubes And Its Potential For Heterogeneous Catalysis, Anne Shanahan, James Sullivan, Mary Mcnamara, Hugh Byrne

Articles

A single-walled carbon nanotube-supported gold nanoparticle composite was prepared and characterized by X-ray diffraction, scanning transmission electron microscopy/scanning electron microscopy/transmission electron microscopy, energy-dispersive X-ray analysis, atomic absorption spectroscopy, nitrogen adsorption, Raman spectroscopy, and ultraviolet-visible spectroscopy. The Au particles were found to be crystalline, with a well-defined and narrow particle-size distribution, centered around 7 nm. The activity and selectivity of the composite for solventless aerobic oxidation of a secondary alcohol were examined, and a conversion efficiency of 95% was obtained.

A Practical Photoelectrochemical Cell Using Nonprecious Metal Electrodes, Patrick Enright, Tony Betts, John Cassidy

Articles

Abstract: Photoelectrochemical cells (PECs) can be used to harvest light from the oxidation of dissolved organic matter. Similar to fuel cells but requiring light to operate, PECs contain a light assisted electrode that oxidises electron rich materials (anode); these electrons then flow to a typically Pt cathode where O₂ is normally the electron acceptor. In this work a PEC cell containing inexpensive materials was shown to (a) mineralise typical organic compounds present in waste water and (b) produce electricity from their decomposition. The PEC cell consisted of a TiO₂ coated conducting ink anode exposed to a light source, …

A Systematic Study Of The Effect Of Silver On The Chelation Of Formic Acid To A Titanium Precursor And The Resulting Effect On The Anatase To Rutile Transformation Of Tio2, Nicholas Nolan, Michael Seery, Steve Hinder, Linda Healy, Suresh Pillai

Articles

Anatase to rutile transition in an unmodified synthetic titania usually occurs at a temperature range of 600 – 700 °C. Various methods such as addition of metallic and non-metallic dopants and modifying the precursor have previously been reported to influence the anatase to rutile transition temperature. In the current study, the effect of addition of increasing amounts of silver to the extent of chelation of a formate group to a titanium precursor and the resulting effects on the transformation of anatase to rutile has been studied. The addition of silver (0, 1, 3 and 5 mol %) on the anatase …

Dual-Action Hygienic Coatings: Benefits Of Hydrophobicity And Silver Ion Release And Surface Analysis, Niall Stobie, Brendan Duffy, John Colreavy, Patrick Mchale, Steven Hinder, Declan Mccormack

Articles

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 …

Interaction Between Langmuir And Langmuir- Blodgett Films Of 5,11,17,23-Tetra-Tert-Butyl-25,27-Diethoxycarbonyl Methyleneoxy-26,28,Dihydroxycalix[4]Arene And 5,17-(9h-Fluoren-2-Yl)Methyleneamino)-11,23-Di-Tert-Butyl-25,27-Diethoxycarbonyl Methyleneoxy-26,28-Dihydroxycalix[4]Arene With Aqueous Copper And Lithium Ions., Mary Deasy, Fintan Kelleher, Faridah L. Supian, Tim H. Richardson, James P. Ward, Vickie Mckee

Articles

The binding interactions between aqueous copper (Cu2þ ) and lithium (Li þ ) ions and Langmuir monolayers and Langmuir-Blodgett (LB) multilayers have been investigated by studying surface pressure-area (Π-A) isotherms and surface potential-area (ΔV-A) behavior in order to find the effective dipole moment, μ^, of the calixarene molecules in the uncomplexed and complexed states. The orientation of both calix[4]arenes, namely, 5,11,17,23-tetra-tert-butyl- 25,27-diethoxycarbonyl methyleneoxy-26,28-dihydroxycalix[4]arene and 5,17-(9H-fluoren-2-yl)methyleneamino)- 11,23-di-tert-butyl-25,27-diethoxycarbonyl methyleneoxy-26,28-dihydroxycalix[4]arene, is such that the plane of the calix ring is parallel with the plane of the water surface regardless of the ion content of the subphase. The Gibbs equation was used to interpret …

Corrosion Protection Properties Of Various Ligand Modified Organic Inorganic Hybrid Coating On Aa 2024-T3, Rajath Varma, John Cassidy, Mohamed Oubaha, Colette Mcdonagh, John Colreavy, Brendan Duffy

Articles

The inclusion of zirconium precursors to prepare organosilane solgel coatings improves the corrosion protection performance of the coatings on aluminium and steel. The inherent differences in the hydrolysis rates of the silane and zirconium precursors, various ligands were used to control the hydrolysis by decreasing the number of reactive alkoxide group. Hybrid sols were synthesised using 3-(trimethoxysilyl) propylmethacrylate (MAPTMS) and zirconium n-propoxide chelated with organic ligands including different organic acids, acetyl acetone and 2 2’ bipyridyl. The effects of zirconia inclusion on the properties of the coatings were compared on the aerospace alloy AA 2024-T3. Electrochemical analysis and salt spray …

Corrosion Protection Of Aa 2024-T3 Aluminium Alloys Using 3, 4-Diaminobenzoic Acid Chelated Zirconium-Silane Hybrid Sol-Gels, P.C. Rajath Varma, John Colreavy, John Cassidy, Mohamed Oubaha, Colette Mcdonagh, Brendan Duffy

Articles

Organic-inorganic polymers formed by hydrolysis/condensation reactions of alkoxide precursors, such as organically modified silanes (Ormosils) have found applications as electronic, optical and protective coatings. Such coatings possess important characteristics such as chemical stability, physical strength and scratch resistance. Further performance improvement is achieved through the incorporation of zirconium and titanium based nanoparticles, also formed through the sol-gel process. However due to the inherent difference in the reactivity of the precursors, the hydrolysis of each precursor must be carried out separately before being combined for final condensation. Zirconium precursors are commonly chelated using acetic acid or acetyl acetonate prior to hydrolysis, …

Silver Nanoparticle Polymer Composite Based Humidity Sensor, Aoife Power, Tony Betts, John Cassidy

Articles

Silver nanoparticles were synthesised by a chemical reduction process in order to produce an aqueous colloidal dispersion. The resulting colloids were then characterised by a combination of UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction and transmission electron microscopy and the nanoparticles were found to have an average diameter of 20–22 nm. The Ag/polymer nanocomposites were then applied to platinum interdigital electrodes as sensor coatings and the capability of the resulting sensor as a humidity detector investigated. With the application of 1 V, a current developed which was found to be directly proportional to humidity levels. The sensor gives a reversible, …

Spectroscopic Investigation Of The Anatase-To-Rutile Transformation Of Sol-Gel Synthesised Tio2 Photocatalysts, Nicholas Nolan, Suresh Pillai, Michael Seery

Articles

Among the three major phases in titania, anatase is reported to be a better photocatalytically active phase. Anatase to rutile transformations, under normal conditions, usually occurs at a temperatue range of 600- 700 °C. Various chemical additives have previously been employed to extend the anatase transition to higher temperatures. Effect of employing various concentrations of formic acid and water on phase transition has systematically been studied by XRD, FTIR and Raman spectroscopy. A considerably higher anatase phase (41%) has been obtained at 800 ºC and 10% anatase composition is retained after annealing the materials at 900 ºC for the optimised …

One-Pot Synthesis Of Anionic (Nitrogen) And Cationic (Sulfur) Codoped High-Temperature Stable, Visible Light Active, Anatase Photocatalysts, Suresh Pillai, Declan Mccormack, Steven Hinder, Pradeepan Periyat

Articles

No abstract provided.

Influence Of Magnesium Nitrate On The Corrosion Performance Of Sol-Gel Coated Aa2024-T3 Aluminium Alloy, Rajath Varma, Brendan Duffy, John Cassidy

Articles

Traditional anti-corrosion technology has relied heavily on using reducible metal species, predominantly hexavalent chromium (Cr(VI)), for protecting reactive metal alloys such as aluminium which is extensively used in the aerospace sector. However, the impending changes in the use of Cr(VI) in Europe and the United States have forced aerospace manufacturers to examine alternative materials for protecting aluminium. One of the most promising alternatives being investigated are organosilane based sol-gels containing anticorrosion additives. In this work the anti-corrosion properties of magnesium (II) nitrate (Mg(NO3)2) as a inhibitor was investigated at different concentrations (0.1% - 1.0 wt %) in a methyltriethoxysilane (MTEOS) …

Effect Of Organic Chelates On The Performance Of Hybrid Sol–Gel Coated Aa2024-T3 Aluminium Alloys, Rajath Varma, John Colreavy, John Cassidy, Mohamed Oubaha, Colette Mcdonagh, Brendan Duffy

Articles

Sol–gels are organic–inorganic polymers formed by hydrolysis/condensation reactions of alkoxide precursors, primarily silanes, which have found applications as electronic, optical and protective coatings. These coatings possess important characteristics such as chemical stability, physical strength and scratch resistance. Further performance improvement is achieved through the incorporation of zirconium and titanium based nanoparticles, also formed through the sol–gel process. However due to the inherent difference in the reactivity of the precursors, the hydrolysis of each precursor must be carried out separately before being combined for final condensation. Zirconium precursors are commonly chelated using acetic acids, prior to hydrolysis, to lower the hydrolysis …

One-Pot Synthesis Of Anionic (Nitrogen) And Cationic (Sulfur) Codoped High-Temperature Stable, Visible Light Active, Anatase Photocatalysts, Suresh Pillai, Declan Mccormack, Steven Hinder, Pradeepan Periyat

Articles

No abstract provided.

Localised Galvanic Corrosion Processes In Thermal Spray Coated/Cast Aluminium Alloy Systems, David Culliton, Tony Betts, David Kennedy

Conference Papers

Cast Aluminium Alloys, because of the propensity of aluminium to react with impurities and alloying elements, are prone to developing IM impurities during the solidification process. These IM phases can act, in some fluids, as initiation sites for localised corrosion processes, resulting in degradation phenomena, such as pitting. Whilst Thermal Spray coatings can improve the wear resistance of Cast Aluminium Alloys, their corrosion performance may be hampered by the presence of through porosity within the coating.

The present work details some preliminary studies of the localised corrosion processes occurring at the interface area between a Thermal Spray coating and a …

Working Report On The Status Quo Of Nanomaterials Impact On Health And Environment, Harald Krug, Margarita Apostolova, Marite Arija Bake, Gordon Chambers, Horia Chiriac, Eva Herzog, Victoria Hand, Jürgen Höck, Peter Hoet, Nicoleta Lupu, Declan Mccormack, Maja Remskar, George Robillard, Jamila Smisterova, Jan Stetkiewicz, Speranta Tanasescu, Aris Tsatsakis, David Vaughn, Peter Wick, Jörg Wörle-Knirsch

Articles

Nanotechnology is regarded as one of the key technologies of the future and associated with high expectations by politics, science and economy. Artificially produced nanosized particles and nanoscale system components have new properties which are of importance for the development of new products and applications. Such new properties of materials and substances result from the special properties of surfaces and interfaces and in part, from the geometric shape of the material. In theory nanoparticles (NPs) can be produced from nearly any chemical; however, most NPs that are currently in use today have been made from transition metals, silicon, carbon (single-walled …

Prevention Of Staphylococcus Epidermidis Biofilm Formation Using A Low-Temperature Processed Silver-Doped Phenyltriethoxysilane Sol–Gel Coating, Niall Stobie, Brendan Duffy, Declan Mccormack, John Colreavy, Martha Hidalgo, Patrick Mchale, Steven Hinder

Articles

Sol–gel coatings which elute bioactive silver ions are presented as a potential solution to the problem of biofilm formation on indwelling surfaces. There is evidence that high-temperature processing of such materials can lead to diffusion of silver away from the coating surface, reducing the amount of available silver. In this study, we report the biofilm inhibition of a Staphylococcus epidermidis biofilm using a low-temperature processed silver-doped phenyltriethoxysilane sol–gel coating. The incorporation of a silver salt into a sol–gel matrix resulted in an initial high release of silver in de-ionised water and physiological buffered saline (PBS), followed by a lower sustained …

Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond

Articles

Urea–calix[4]arenes 1 and 2 were synthesised and incorporated into ISE membranes for assessment as sensors for inorganic anions in water. 1 revealed a strong response to all anions following the Hofmeister selectivity order. For ISEs of 2, the response to a portion of the anion series was suppressed, increasing the margin of selectivity of nitrate over chloride, a common interferant of nitrate in fresh and marine water samples. The performance of ISEs containing 2 was compared to commercially available alkylammonium nitrate ion-exchange salts used for nitrate sensing. Our ISEs performed favourably in terms of sensitivity, linear range and LOD performing …

A Novel Tio2 / Pvc Layer For Use In A Photoelectrochemical Cell, Faiza Touati, John Cassidy, Kevin Mcguigan

Articles

A novel method of coating titanium dioxide on a glassy carbon electrode as a polyvinylchloride composite , is described. On illumination , there is an enhanced voltammetric current at this TiO2/PVC composite in aqueous formic acid solution. This electrode is used as the basis of a formic acid fuel cell where oxygen is reduced at a platinum cathode. The system yields 100 cm-2 for 0.01 mol dm-3 HCOOH in 0.1 mol dm-3 NaOH under illumination from a 150 W xenon lamp. The current without illumination is 0.5 cm-2.

Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond

Articles

The current work is amongst the first to examine the potential usefulness of the nitrile functional group in potentiometric analytical sensors for soft metals. Nitrile functionality has hereby been incorporated into a calix[4]arene skeleton to give a series of new cation selective hosts. The analytical sensing behaviour of these hosts was examined by Ion Selective Electrode (ISE) based potentiometry. In all cases a preference for soft metals was observed, explained primarily in terms of soft–soft compatibility between calix[4]arene nitrile hosts and metal guests in combination with a classical ‘lock and key’ best fit mechanism. Hosts 2, 3 and 4 showed …

A Chloride Selective Calix[4]Arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction, Benjamin Schazmann, Dermot Diamond

Articles

A neutral 2-site chloride selective compound has been developed (3), based on a 1,3- alternate tetrasubstituted calix[4]arene providing a preorganised supramolecular scaffold. The resultant supramolecular cavity is amongst the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signalling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion amongst a wide variety of anions tested. 3 …

Self-Assembled Arrays Of Zno Nanoparticles And Their Application As Varistor Materials, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh

Articles

Linear arrays of ZnO nanoparticles have been successfully prepared by a simple sol–gel condensation reaction involving chemical modifiers, followed by drying (80oC) and calcination (500 oC). The calcined material (nanoarray ZnO) is composed of approximately spherical nanoparticles of average diameter 21+/-3 nm, selfassembled to form arrays extending in length to 2–4 mm. The morphology of the ZnO is found to depend sensitively on the amounts of chemical modifiers present. In their absence the ZnO produced (nano-ZnO) is an unstructured agglomerate of nanoparticles. The mechanism for formation of these linear arrays has been investigated by examining the intermediates formed at 80 …

Growth Of Well-Defined Zno Microparticles By Hydroxide Ion, Ruth Mcbride, Declan Mccormack, John Kelly

Articles

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(NO3)2 (0.025 M) and sodium hydroxide (0.375 M) to 101 uC and maintaining it at that temperature for periods of up to …