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Articles 211 - 234 of 234
Full-Text Articles in Physical Sciences and Mathematics
A Novel Tio2 / Pvc Layer For Use In A Photoelectrochemical Cell, Faiza Touati, John Cassidy, Kevin Mcguigan
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.
An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan
An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan
Articles
Work in photochemistry work peaked in the 1980’s where there was the prospect of using sunlight shining on suspensions of titanium dioxide in order to catalytically cleave water into hydrogen and oxygen [1-5]. In this way a clean and efficient method of producing hydrogen as a fuel was envisaged. However, there was a requirement to use a rather high energy light to achieve the splitting and it was not as efficient with visible light[5]. Doped TiO2 layers have been used in a three electrode system for formic acid degradation[6]. In this work, the system uses an electrode coated with TiO2 …
Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond
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 …
Use Of The Mitsunobu Reaction In The Synthesis Of Orthogonally Protected A,B-Diaminopropionic Acids, Fintan Kelleher, Keith Ó Proinsias
Use Of The Mitsunobu Reaction In The Synthesis Of Orthogonally Protected A,B-Diaminopropionic Acids, Fintan Kelleher, Keith Ó Proinsias
Articles
Orthogonally protected a,b-diaminopropionic acids have been synthesised in good yields by the reaction of N-trityl L-serine esters with N-substituted sulfonamides under Mitsunobu reaction conditions (DEAD, PPh3, THF). The best isolated yields were obtained when N-Boc p-toluenesulfonamide was used as the nitrogen nucleophile precursor in the Mitsunobu reaction. Subsequently, the N-trityl group was efficiently replaced with the more stable allyloxycarbonyl (alloc) group.
Synthesis And Characterisation Of Tetra-Tetrazole Macrocycles, Andrew Bond, Adrienne Fleming, Fintan Kelleher, John Mcginley, Vipa Prajapati, Signe Skovsgaard
Synthesis And Characterisation Of Tetra-Tetrazole Macrocycles, Andrew Bond, Adrienne Fleming, Fintan Kelleher, John Mcginley, Vipa Prajapati, Signe Skovsgaard
Articles
The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of one previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl chain linker, the relative orientation of the tetrazole rings on the benzene ring, and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene …
Newly Identified Vitamin K-Producing Bacteria Isolated From The Neonatal Faecal Flora, Gordon Cooke, John Behan, Mary Costello
Newly Identified Vitamin K-Producing Bacteria Isolated From The Neonatal Faecal Flora, Gordon Cooke, John Behan, Mary Costello
Articles
Fat-soluble vitamin K is an essential component of the blood clotting process. Menaquinones are the naturally occurring form of vitamin K identified in bacteria. Lipid extracts were made from three bacteria originally isolated from the human neonatal gut and identified as Enterobacter agglomerans, Serratia marcescens and Enterococcus faecium. Following preparative thin layer chromatography (TLC), the lipid extracts were subjected to liquid chromatography-mass spectrometry (LC-MS) analysis. Peak analysis of the LC-MS data showed that the three bacteria produce various forms of menaquinone.
Implications Of Mass Education On Chemistry Higher Education, Christine O'Connor
Implications Of Mass Education On Chemistry Higher Education, Christine O'Connor
Articles
The following paper discusses the implications of government policy for widening access and participation in third level institutes. The increase in ‘non-traditional’ students has been widely recognised on an international scale; however, some issues of inequality still exist. The ‘struggles’ associated with widening participation and the creation of a ‘new’ student type are discussed, with particular reference to chemistry education. A change is needed with regard to the pedagogical approach taken by staff in order to cater for a diverse student body comprising a broad range of learner types, and this must be supported both at departmental and institutional levels. …
A Chloride Selective Calix[4]Arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction, Benjamin Schazmann, Dermot Diamond
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 …
Spirobicyclic Diamines 2: Synthesis Of Homochiral Diastereoisomeric Proline Derived [4,4]-Spirolactams, Fintan Kelleher, Sinead Kelly
Spirobicyclic Diamines 2: Synthesis Of Homochiral Diastereoisomeric Proline Derived [4,4]-Spirolactams, Fintan Kelleher, Sinead Kelly
Articles
L-Proline derived diastereoisomeric [4.4]-spirolactams have been prepared by a reductive-amination reaction of (R)- or (S)-alanine methyl ester followed by thermal cyclisation of the resulting amine onto the proline ester group in refluxing toluene. Under similar conditions (R)- or (S)-phenylalanine methyl ester gave no cyclisation products, while R- or S-a-methylbenzylamine required treatment with NaNH2 in refluxing toluene to induce cyclisation giving diastereoisomeric [4.4]-spirolactams
Spirobicyclic Diamines 1: Synthesis Of Proline-Derived Spirolactams Via Thermal Intramolecular Ester Aminolysis, Fintan Kelleher, Sinead Kelly
Spirobicyclic Diamines 1: Synthesis Of Proline-Derived Spirolactams Via Thermal Intramolecular Ester Aminolysis, Fintan Kelleher, Sinead Kelly
Articles
Proline derived [4.4]-spirolactams have been synthesised in good yields by a reductive-amination reaction followed by thermal cyclisation of the resulting amine onto the proline ester group in refluxing toluene. The synthesis of the corresponding [4.5]-spirolactams by the same method gave much reduced yields.
Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond
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 …
Photocontrol Of Upper And Lower Rim Complexation Of Neutral And Cationic Species By P-Tert-Butylcalix[4]Arene Tetraethyl Ester, Mary Deasy, Bernadette Creaven, Brian A. Murray, Catherine Mckenna, Darren Tobin
Photocontrol Of Upper And Lower Rim Complexation Of Neutral And Cationic Species By P-Tert-Butylcalix[4]Arene Tetraethyl Ester, Mary Deasy, Bernadette Creaven, Brian A. Murray, Catherine Mckenna, Darren Tobin
Articles
A number of sodium salt complexes of p-tert-butylcalix[4]arene tetraethyl ester, 1, were isolated both with and without upper-rim encapsulated solvent. Selective decomplexation of lower rim bound sodium cations and upper rim encapsulated solvent molecules could be successfully achieved using low pressure light sources. Oxidation of the counter anion at the lower rim of p-tert-butylcalix[4]arene tetraethyl ester triggered both the upper and lower rim decomplexation process. The extent of decomplexation at both rims is controlled both by the nature of the counter-anionic species at the lower rim and by the fate of the photoproducts generated. The calixarene host …
Identification And Recovery Of An Asymmetric Calix[4]Arene Tetranitrile Derivative Using Liquid Chromatography And Mass Spectrometry, Benjamin Schazmann, Dermot Diamond
Identification And Recovery Of An Asymmetric Calix[4]Arene Tetranitrile Derivative Using Liquid Chromatography And Mass Spectrometry, Benjamin Schazmann, Dermot Diamond
Articles
A simple analytical LC-MS (Liquid Chromatography Mass Spectrometry) method and associated instrumentation has been adapted for use by the organic chemist to yield mg quantities of target compound from a reaction mixture. Calix[4]arene 3 was identified as representing 51% of total peak area of a reaction mixture containing no less than 10 components, using LC-MS. This peak corresponded to a mass of 878.8, equivalent to a complex of 3 and an ammonium cation. Molecular models further rationalise this observation by showing that the asymmetric binding cavity of 3 is suitable for binding tetrahedral guests like the ammonium ion. By scaling …
Self-Assembled Arrays Of Zno Nanoparticles And Their Application As Varistor Materials, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh
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 …
Increased Frequency Of The Mthfr A1298c Mutation In An Irish Population, Cathal Mccarthy, Fergus Ryan, Joseph Vaughan
Increased Frequency Of The Mthfr A1298c Mutation In An Irish Population, Cathal Mccarthy, Fergus Ryan, Joseph Vaughan
Articles
No abstract provided.
A Novel Tiq2-Assisted Solar Photocatalytic Batch-Process Disinfection Reactor For The Treatment Of Biological And Chemical Contaminants In Domestic Drinking Water In Developing Countries, E. F. Duffy, F. Al Touati, S. C. Kehoe, O. A. Mcloughlin, L. W. Gill, W. Gernjak, I. Oller, M. I. Maldonado, S. Malato, John Cassidy, R. H. Reed, K. G. Mcguigan
A Novel Tiq2-Assisted Solar Photocatalytic Batch-Process Disinfection Reactor For The Treatment Of Biological And Chemical Contaminants In Domestic Drinking Water In Developing Countries, E. F. Duffy, F. Al Touati, S. C. Kehoe, O. A. Mcloughlin, L. W. Gill, W. Gernjak, I. Oller, M. I. Maldonado, S. Malato, John Cassidy, R. H. Reed, K. G. Mcguigan
Articles
he technical feasibility and performance of photocatalytic Ti02 coatings in batch-process solar disinfection (SODIS) reactors to improve potability of drinking water in developing countries have been studied. Borosilicate glass and PET plastic SODIS reactors fitted with flexible plastic inserts coated with Ti02 powder were shown to be 2(Jt1o and 25% more effective, respectively, than standard SODIS reactors for the inactivation of E. coli K12. Isopropanol at 100 ppm concentration levels was observed to be completely photodegraded after 24 h continuous exposure to lOG mW/cm2 simulated sunlight in a similar solar photocatalytic disinfector (SPC-DIS) reactor. The technique for p roducing the …
Growth Of Well-Defined Zno Microparticles By Hydroxide Ion, Ruth Mcbride, Declan Mccormack, John Kelly
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 …
Simulation Of Dynamic Electrochemical Processes, John Cassidy
Simulation Of Dynamic Electrochemical Processes, John Cassidy
Articles
This work is designed to introduce electrochemists in a tutorial manner to the basics of modeling of electrochemical systems based primarily on diffusion equations. There is an introduction to analytical and numerical methods with examples taken from typical electrochemical experiments. The Laplace transform is used to derive the Cottrell equation and chronopotentiometry. The response of an electrode to a Gaussian concentration profile is detailed. Laplace’s equation is solved for a simple cell to determine the potential distribution. Discrete methods are employed to calculate the current time behavior following a potential step using the explicit finite difference method. Cyclic voltammetry is …
Enantioselective Complexation Of Amino Acids By 6a-Deoxy-6a-Hydroxyethylamino- Β -Cyclodextrin And Its Metallo-Derivatives In Aqueous Solution, Nicole Van Hoof, Noel Russell, Mary Mcnamara, Raphael Darcy
Enantioselective Complexation Of Amino Acids By 6a-Deoxy-6a-Hydroxyethylamino- Β -Cyclodextrin And Its Metallo-Derivatives In Aqueous Solution, Nicole Van Hoof, Noel Russell, Mary Mcnamara, Raphael Darcy
Articles
Enantioselectivity towards several amino acids by metallo-6A-deoxy-6A-hydroxyethylamino-β-cyclodextrins (metallo- β CDea’s) was investigated by potentiometric titration of the various amino acid/metallo- β CDea systems with NaOH solution. It was shown that the cyclodextrin derivative is capable of distinguishing between enantiomers of amino acid species in the presence of certain metal ions (Co, Ni, Cu and Zn). Ni- β CDea complexes show the most enantioselectivity,whereas for Cu and Co2C-_CDea complexes less selectivity is observed. As expected, Zn- β CDea complexes exhibit no enantioselectivity. Stability and selectivity, however, do not go hand in hand, since the most stable complexes are formed …
Note On The Voltammetry Of Ferrocene Carboxylate In Aqueous Solution, John Cassidy, John O'Gorman, M. Ronane, Enda Howard
Note On The Voltammetry Of Ferrocene Carboxylate In Aqueous Solution, John Cassidy, John O'Gorman, M. Ronane, Enda Howard
Articles
Cyclic voltammetry of ferrocene dicarboxylate in aqueous solutions at high pH, in the presence of oxygen, showed evidence of an EC' mechanism where the oxidised form of ferrocene dicarboxylate reacts with H02- , which had been produced at a lower potential. However, an analogous experiment with ferrocene carboxylate yielded a cyclic voltammogram with a post peak: following the anodic peak: for ferrocene carboxylate. The reason for the post peak: is not clear but may be due to a delay in the reaction between the oxidised form of ferrocene carboxylate and H02-.
Use Of Excel To Obtain Voltammetric Information On Microelectrodes, Enda Howard, John Cassidy
Use Of Excel To Obtain Voltammetric Information On Microelectrodes, Enda Howard, John Cassidy
Articles
The use of curve fitting for the analysis and interpretation of voltammetric data obtained while working with micro electrodes is discussed as a useful exercise for introducing students to the principle of problem solving using least-squares curve-fitting techniques. The advantages associated with this approach to data processing over the approach where the limiting current (i L) alone is used are discussed and its limitations are highlighted. This technique was applied to the determination of unknown concentrations of ferrocyanide and the most satisfactory recovery of concentrations was found when both the va1ues of the formal potential (EO') and concentration ( C) …
Electroanalysis Using Differential Pulse Methods At A Microelectrode, Enda Howard, John Cassidy, John O'Gorman
Electroanalysis Using Differential Pulse Methods At A Microelectrode, Enda Howard, John Cassidy, John O'Gorman
Articles
This communication characterises the differential pulse voltammetric response of ultramicroelectrodes in connection with two different models
Rotating Disk Ion Selective Electrodes, John Cassidy, David Mullen, Karen Casey, Patrick Cullen
Rotating Disk Ion Selective Electrodes, John Cassidy, David Mullen, Karen Casey, Patrick Cullen
Articles
A simulation was undertaken to predict the transient potential response following a concentration step at a rotating disk electrode comprised of an ion selective layer. A basis for this simulation was that the potential response would be independent of rotation rate since the diffusion layer is larger than the double layer at the electrode. In practice it was found that the potential response does vary with rotation rate. The response was such that the apparent concentration of the analyte in solution decreased with increased rotation rate. The reason for this behavior is due to the disruption of the double layer …
Cyclic Voltammetry Of Polypyrroledodecylbenzenesulfonate Layers, T. Mccormac, W. Breen, A. Mcgee, John Cassidy, M. E.G. Lyons
Cyclic Voltammetry Of Polypyrroledodecylbenzenesulfonate Layers, T. Mccormac, W. Breen, A. Mcgee, John Cassidy, M. E.G. Lyons
Articles
Polypyrrole was deposited from solutions of NaCIO. and NaDBS, where DBS is dodecylbenzenesulfonate in aqueous solu\ion and characterizcd by voltammetry. It is found that the absence of the so-called 'double laver charging current' during cyclic voltammetry of the layers formed from solutions with surfactant is not because of' the" order in morphology of the layer, but irreversible incorporation of' the surfactant anion.