http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:18358 The effect of gaseous carbon monoxide on the hydrogenation of acetylene over Ni supported on MgAl₂O₄ in the presence and absence of zinc dopants has been investigated. Both carbon monoxide and zinc inhibit activity to a considerable extent. Carbon monoxide also lowers the selectivity to ethane substantially. Zinc causes some reduction in selectivity in the absence of carbon monoxide but only at very high conversions when it is present. 2012-03-29T21:22:08.675Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:14256 Confocal laser scanning microscopy (CLSM) in combination with a fluorescently labeling enzyme dye, LavaPurple™, was demonstrated as a technique for the visualization of Thermomyces (Humicola) lanuginosa lipase (LIPHLL) and Candida antarctica lipase A (LIPCA) within a transparent latex coating. Addition of Teric Surfactants (C16 non-ionic Teric 475, 1.8% (w/w) or C10 non-ionic Teric 460, 2.0% (w/w)) significantly increased the accumulation of both LIPHLL and LIPCA to the surface of a latex coating. An α-naphthyl acetate substrate assay was used to quantify the accumulated lipase. The results derived from the acetate assay correlated with the enzyme accumulation (at the surface) observed in the CLSM images of the latex coating. This correlation demonstrated that the increased enzyme accumulation within the top 2 μm of the latex film was responsible for the increase in surface enzymatic activity. The combination of CLSM imagery and quantifiable image analysis provided a valuable tool for the optimization of surfactant concentrations for maximizing the activity of an enzyme (and potentially other additives) within a latex coating. 2011-08-01T06:23:32.968Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13870 9 page(s) 2011-06-29T06:20:59.695Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13871 The electrochemical underpotential deposition (UPD) of lead on Au(110) was investigated by XPS using a custom-built ultrahigh vacuum apparatus containing a chamber for electrochemical studies. A two-step deposition process for lead UPD was confirmed. A large increase in the surface concentration of oxygen was found in solutions containing lead. The presence of lead was detected on the gold surface at all potentials within the range investigated (−500 mV to 1500 mV vs. Ag/AgCl). Degradation of chlorine by x-rays was observed. The change in surface components with potential was investigated and linked to models of UPD and oxidation. The initial random deposition of lead from solution led to surface disordering. 2011-06-29T06:20:54.598Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13875 Manganese dioxide (MnO₂) appears to be an effective cathode material for a battery system. No studies on lithium insertion in aqueous media are known to the best of our knowledge. However, in one of our previous papers we reported that lithium could be intercalated into a MnO₂ host compound using an aqueous LiOH electrolyte; however simple chemistry suggests that it should not. It is found that a battery with LiOH electrolyte functions quite differently from the cell that uses Li₂SO₄. This paper describes the surface modifications that accompany the electrochemical behavior of MnO₂ during redox (discharge) processes in the lithium hydroxide and sulfate media. XPS and SIMS techniques were used to study the resultant surface of the MnO₂ cathode and the spectra reveal that the formation of an insoluble layer of Li₂CO₃ precedes the process of reduction. SEM was used to study the microstructure of the MnO₂ cathode. 2011-06-29T06:20:44.438Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12291 A literature proposal that the reduction of nitrous oxide by carbon monoxide over rhodium catalysts proceeds by cleavage of the Nsingle bondN bond has been tested through the use of ¹⁵N¹⁴NO as the reactant. The results disprove the suggestion in that ¹⁴N¹⁵N is the dominant product at temperatures from 336 °C to 356 °C with nitrous oxide conversions from 26% to >99%. Little, if any, ¹⁴N₂ and ¹⁵N₂ is formed, in contrast with the 25% of each expected for the model. Results for the corresponding reaction of ¹⁵N¹⁴NO with H₂ are even more clear-cut in demonstrating the absence of N-N bond cleavage. The activity of the Rh/SiO₂ used here for the N₂O/CO system fell within the rather wide of values reported in the literature for other Rh catalysts. However, activity for the reduction of N₂O by H₂ was approximately five times higher than the only previous result in the literature, that for a Rh/Al₂O₃ catalyst. Graphical abstract The reduction of ¹⁵N¹⁴NO by carbon monoxide, and also by hydrogen, over a Rh/SiO₂ catalyst yields ¹⁵N¹⁴N as the exclusive nitrogen-containing product. The result rules out a suggestion in the literature that the reduction using carbon monoxide proceeds through cleavage of the nitrogensingle bondnitrogen bond. 2011-06-24T05:11:43.713Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13417 Because highly luminescent lanthanide compounds are limited to Eu(3+) and Tb(3+) compounds with red (Eu, approximately 615 nm) and green (Tb, approximately 545 nm) emission colors, the development and application of time-resolved luminescence bioassay technique using lanthanide-based multicolor luminescent biolabels have rarely been investigated. In this work, a series of lanthanide complexes covalently bound silica nanoparticles with an excitation maximum wavelength at 335 nm and red, orange, yellow and green emission colors has been prepared by co-binding different molar ratios of luminescent Eu(3+)-Tb(3+) complexes with a ligand N,N,N(1),N(1)-(4'-phenyl-2,2':6',2''-terpyridine-6,6''-diyl)bis(methylenenitrilo) tetrakis (acetic acid) inside the silica nanoparticles. The nanoparticles characterized by transmission electron microscopy and luminescence spectroscopy methods were used for streptavidin labeling, and time-resolved fluoroimmunoassay (TR-FIA) of human prostate-specific antigen (PSA) as well as time-resolved luminescence imaging detection of an environmental pathogen, Giardia lamblia. The results demonstrated the utility of the new multicolor luminescent lanthanide nanoparticles for time-resolved luminescence bioassays. 2011-05-30T02:50:05.730Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13194 We report the use of europium chelate, 4,4′-bis(1′′,1′′,1′′,2′′,2′′,3′′,3′′-heptafluoro-4′′,6′′-hexanedion-6′′-yl)chlorosulfo-o-terphenyl-Eu³⁺(BHHCT-Eu³⁺), in silver nanostructure-enhanced luminescence and its application to bioassays and bioimaging. The highest luminescence intensity enhancement factor of BHHCT-Eu³⁺ achieved in this study was about 11 times, while the simultaneously measured luminescence lifetime was reduced 2-fold. The luminophore photostability was also improved by a factor of 3. On the basis of these experimental results, we estimated the impact of silver nanostructures on the excitation and emission enhancement factors. Luminescence enhancement was demonstrated in two geometries: on planar glass substrates and on silica beads. In the biotin-modified IgG antibody assay the bead geometry provided slightly higher enhancement factor and greater sensitivity. Subsequently, we applied such bead substrates to time-gated luminescence imaging of Giardia lamblia cells stained by BHHCT-Eu3+ where we observed improved brightness by a factor of 2. Such improved photostability and brightness of BHHCT-Eu³⁺ in the presence of metal nanostructures are highly desirable for ultrasensitive bioassays and bioimaging, especially with time gating. 2011-05-25T21:44:19.340Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:13197 We introduce a novel quantitative approach to describe ionic gating and use the Kramers equation for electrodiffusion of ions through membrane channels to construct a simple dynamical system for transient action potentials and resting potentials in giant axons of the squid on a better physicochemical basis than the Hodgkin−Huxley (HH) model and the Goldman−Hodgkin−Katz (GHK) model. Like the HH dynamical system, our present model describes many features of excitable membranes such as sharp firing thresholds, latency, refractory periods, repetitive firings with a sustained stimulating current, excitation blocking, and propagating action potentials. It differs from the HH dynamical system in having three fixed points, the first of which corresponds to the electrodiffusive resting potential. The second fixed (or saddle) point corresponds to the threshold for generation of local action potentials. It predicts monotonic rather than oscillatory decay of the membrane potential following subthreshold stimulation by microelectrodes. The ratio of sodium to potassium currents in the resting state of the membrane is set at 3:2. In the electrodiffusive “resting” state, all potassium and sodium activation gates are postulated to be closed, whereas, according to the HH model, about 32% of the potassium gates and 5.3% of the sodium activation gates are open. As our electrodiffusive “resting” state, described by a generalization of the GHK model, emerges as the stable fixed point of our dynamical system, our new model provides a unified treatment of both transient action potentials and electrodiffusive “resting” potentials in perfused axons. 2011-05-25T21:44:11.036Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:12176 Triplet-state dynamics in Chl-a/Per mixtures in organic solvent and in native H-PCP were studied by means of step-scan FTIR spectroscopy. A single decay component of 10 μs was observed for the H-PCP triplet, the spectrum of which closely matches the 13 μs component of A-PCP [Alexandre et al., Biophysical Journal 93 (2007) 2118–2128], implying that in H-PCP, as in A-PCP, the peridinin triplet state is shared with Chl-a. In a mixture of Chl-a and Per in THF, TEET from ³Chl-a to ³Per proceeds in 3.5 μs followed by ³Per decay in 7 μs. Using a target analysis procedure, ³Chl-a and ³Per infrared difference spectra were obtained. The specific carbonyl frequencies of ³Per and ³Chl-a in THF confirm our assignment of their co-existence in the infrared spectra of H-PCP and A-PCP. 2011-03-11T03:30:17.500Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9438 The title compound, C₁₅H₁₀Br₂Cl₂N₂, a 2,8-dibromo-4,10-dichloro Tröger's base analogue derived from 4-bromo-2-chloroaniline, has a dihedral angle of 110.9 (10)° between the two aryl rings, the largest yet measured for a simple dibenzo analogue. 2011-01-20T23:46:20.828Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9304 Sculpted SERS-active substrates are prepared by assembling a closed packed monolayer of uniform polystyrene colloidal particles (diameter 350 to 800 nm) onto an evaporated gold surface and then electrodepositing gold through this template to produce films with controlled thicknesses, measured as fractions of the sphere diameter, d. The resulting surfaces consist of a regular hexagonal array of interconnected spherical cross-section dishes. The role of localised plasmons in determining the SERS enhancement factor obtained for benzene thiol adsorbed onto the surfaces is then investigated by correlation of the UV-visible reflectance spectra, 400 to 900 nm, measured at the same positions on the substrate surfaces, with the SERS spectra. The results are interpreted in terms of the relative contributions of plasmons that are free to propagate across the top surface and those trapped within the dishes of the sculpted surface. 2010-08-29T09:23:03.173Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9142 In this study we report results for a systematic study of the wetting of structured gold surfaces formed by electrodeposition through monolayer templates of close-packed uniform submicrometer spheres. Removal of the template after deposition leaves a regular hexagonal array of sphere segment pores where the depth of the pores and, thus, the topography of the surface are controlled by the thickness of gold deposited through the template. We find that, as the thickness of the porous film increases up to the radius of the pores, the apparent contact angle for water on the surface increases from 70° on the flat surface to more that 130°, and then with increasing thickness above the radius of the pores the apparent contact angle decreases back toward 70°. We show that these changes in the apparent contact angle agree with the model of Cassie and Baxter for nonwetted surfaces even though the gold itself is hydrophilic. We also show that the apparent contact angle is independent of the diameter of the pores over the range 400−800 nm. This is the first reported example showing the change of a hydrophilic surface (θ < 90°) into a hydrophobic surface (θ* > 90°) purely by control of the surface topography. The role of the pore shape and size in stabilizing the nonwetting (Cassie−Baxter) droplet on the surface is discussed. 2010-08-09T09:00:22.909Z ]]>