Surface enhanced resonance Raman and luminescence on plasmon active nanostructured cavities

Presented here are studies of the impact of excitation angle on surface enhanced Raman and luminescence spectroscopy of dye immobilised on a plasmon active nanocavity array support. Results show that both Raman and luminescence intensities depend on the angle of incidence consistent with the presence of cavity supported plasmon modes. Dependence of scattering or emission intensity with excitation angle occurs over the window of observation

Electrochemiluminescence (ECL) sensing properties of water soluble core-shell CdSe/ZnS quantum dots/Nafion composite films

Water soluble positively charged 2-(dimethylamino) ethanethiol (DAET)-protected core-shell CdSe/ZnS quantum dots (QDs) were synthesized and incorporated within negatively charged Nafion polymer films. The water soluble QDs were characterized using UV-visible and fluorescence spectroscopies. Nafion/QDs composite films were deposited on glassy carbon electrodes and characterized using cyclic voltammetry. The electrochemiluminescence (ECL) using hydrogen peroxide as co-reactant was enhanced for Nafion/QDs composite films compared to films of the bare QDs. Significantly, no ECL was observed for Nafion/QDs composite films when peroxydisulfate was used as the co-reactant, suggesting that the permselective properties of the Nafion effectively exclude the co-reactant. The ECL quenching by glutathione depends linearly on its concentration when hydrogen peroxide is used as the co-reactant, opening up the possibility to use Nafion/QDs composite films for various electroanalytical applications

High Sensitivity DNA Detection Using Gold Nanoparticle Functionalised Polyaniline Nanofibres

Polyaniline (PANI) nanofibres (PANI-NF) have been modified with chemically grown gold nanoparticles to give a nanocomposite material (PANI-NF–AuNP) and deposited on gold electrodes. Single stranded capture DNA was then bound to the gold nanoparticles and the underlying gold electrode and allowed to hybridise with a complementary target strand that is uniquely associated with the pathogen, Staphylococcus aureus (S. aureus), that causes mastitis. Significantly, cyclic voltammetry demonstrates that deposition of the gold nanoparticles increases the area available for DNA immobilisation by a factor of approximately 4. EPR reveals that the addition of the Au nanoparticles efficiently decreases the interactions between adjacent PANI chains and/or motional broadening. Finally, a second horseradish peroxidase (HRP) labelled DNA strand hybridises with the target allowing the concentration of the target DNA to be detected by monitoring the reduction of a hydroquinone mediator in solution. The sensors have a wide dynamic range, excellent ability to discriminate DNA mismatches and a high sensitivity. Semi-log plots of the pathogen DNA concentration vs. faradaic current were linear from 150 × 10−12 to 1 × 10−6 mol L−1 and pM concentrations could be detected without the need for molecular, e.g., PCR or NASBA, amplification

Synthesis, characterisation and charge transport properties of a series of osmium containing polymers

A series of metallopolymers, based on poly(4-vinylpyridine) (PVP) and poly(N-vinylimidazole) (PVI), has been prepared containing both osmium- and ruthenium-bis (2,2’-bipyridyl) centres. The polymers have been character ised using uv/vis and emission spectroscopy as well as, thermal and electrochemical methods. The results obtained are compared wi th those obtained for the metallopolymers containing only osmium or ruthenium centres as well as, model monomeric complexes. The results for mixed metal polymers suggest that there is little interact ion between the metal centres when in solution, either in the ground or excited state. The rate of homogeneous charge t ranspor t through [Os(bipy)2 (PVP)nCl]Cl films (n = 5, 10, 15, 20 and 25), has been examined using potentia l step methods and cyclic voltammetry . The effect of redox site loading, electrolyte type and concentra tion and temperature on the charge transport diffusion coefficient for homogeneous charge t rans fer wi thin the immobilised film for the Os(II/III) oxidation, has been investigated. The relevant activation parameters, enthalpy, ent ropy and free energy changes and activation energy for diffusional charge transport are presented. The results obtained suggest that at short times mass and charge transport can be decoupled, while at longer times the mass transport required to maintain electroneutrality occurs. The standard rate constant k° and transfer coefficient character is ing the heterogeneous electron transfer reaction from the under lying electrode into the modifying film have also been evaluated. The effect of variations in osmium content within the film, electrolyte type and concentration and temperature on these parameters is examined. The relevant enthalpies for the heterogeneous electron transfer reaction have been evaluated. The reaction entropy is similar for all redox site loading electrolyte concentration combinations examined suggesting that the local micro environment of the redox centre remains largely unal tered by changes in the nature of the supporting electrolyte or the active site loading. The charge t ransport properties of [Os(bipy)2 (PVI )nCl]Cl where PVI is poly(n-vinylimidazole) and n = 5, 10, 15, 20 and 25 has been explored in a range of electrolytes based on chloride, sulphate, tosylate and perchlorate anions. The effect of electrolyte and redox site loading and temperature on the homogeneous charge transport process reveals that for low redox site loading/high electrolyte concent ration segmental polymer chain motion limits Dq-j-. In contra st, for high active site/low electrolyte concent ration combinations the rate of charge transport is controlled by ion transport within the film. The effect of electrolyte and active site loading on k° is also explored. Homogeneous and heterogeneous charge t rans fer through poly(N-vinylimidazole) conta ining [Os(N)g] ' moieties has been examined as a function of the nature of the contacting electrolyte solution and of temperature . The charge transport parameters are sensitive to the nature of the electrolyte anion. In sulphur ic acid charge transport is rapid and is consistent with a swollen porous film. In perchloric acid the films appear compact. The abil ity of the [Os(bipy)2 (PVP)jgCl]Cl polymer to catalyse the reduction of Fe(III) to Fe(II) in both 0.1 M H2 SO4 and 1.0 M HCIO4 electrolytes is demonst rated. Catalysis occurs at a large por tion of the active sites wi thin the polymer in sulphur ic acid leading to three dimensional catalysis. In perchloric acid catalysis only occurs wi thin a region of molecular dimensions at the film/electroly te interface

The influence of poly (2-methoxyaniline-5-sulfonic acid) on the electrochemical and photochemical properties of a highly luminescent ruthenium complex

Immobilisation of a luminescent material on an electrode surface is well known to substantially modulate its photophysical and electrochemical properties. Here a positively charged ruthenium metal complex ([Ru(bpy)(3)](2+)) is immobilised on all electrode surface by ion paring with a sulfonated conducting polymer poly(2-methoxyaniline-5-sulfonic acid), (PMAS). Significantly, our study reveals that the electron transport between the ruthenium metal centres can be greatly enhanced due to the interaction with the conducting polymer when both are surface confined. Charge transfer diffusion rates in the present system are an order of magnitude faster than those found where the metal centre is immobilised within a non-conducting polymeric matrix. Electron transport appears to be mediated through the PMAS conjugated structure, contrasting with the electron hopping process typically observed in non-conducting metallopolymers. This increased regeneration rate causes the ruthenium-based electrochemiluminescence (ECL) efficiency to be increased. The impact of these observations on the ECL detection of low concentrations of disease biomarkers is discussed. (c) 2007 Published by Elsevier Ltd

Deactivation of the ruthenium excited state by enhanced homogeneous charge transport: Implications for electrochemiluminescent thin film sensors

peer-reviewedThe electrochemiluminescent (ECL) performance of three ruthenium-based metallopolymer platforms with different homogeneous charge transfer diffusion coefficients (DCT) is reported. Significantly, simultaneous detection of light and current in tandem with steady-state photoluminescence studies demonstrate that increasing the rate of Ru3 + production via enhanced charge transport results in a decrease in ECL intensity of up to 82% when the concentration of the co-reactant, sodium oxalate, is low, i.e., sub-mM. Spectroelectrochemical studies demonstrate that for maximum sensitivity to be obtained, the electroactive properties of the polymeric support matrix need to be considered in tandem with luminophore, analyte and co-reactant concentrations

Planar Airy beam light-sheet for two-photon microscopy

We demonstrate the first planar Airy light-sheet microscope. Fluorescence light-sheet microscopy has become the method of choice to study large biological samples with cellular or sub-cellular resolution. The propagation-invariant Airy beam enables a ten-fold increase in field-of-view with single-photon excitation; however, the characteristic asymmetry of the light-sheet limits its potential for multi-photon excitation. Here we show how a planar light-sheet can be formed from the curved propagation-invariant Airy beam. The resulting symmetric light sheet excites two-photon fluorescence uniformly across an extended field-of-view without the need for deconvolution. We demonstrate the method for rapid two-photon imaging of large volumes of neuronal tissue.Comment: 7 pages, 4 figure

Electrochemiluminescence platform for the detection of C-reactive proteins : application of recombinant antibody technology to cardiac biomarker detection

This work exploits the high-affinity of recombinant antibodies and low background electrochemiluminescence (ECL) for cardiac-biomarker detection. The developed assay is capable of fg mL-1 detection limits as well as the detection of C-Reactive Protein (CRP) over a clinically relevant range. The assay demonstrated robust reproducibility, selectivity and stability while also highlighting a novel platform for detection of cardiac biomarkers at low concentrations

Mid-Infrared Imaging of NGC 6334 I

We present high-resolution (<0.5") mid-infrared Keck II images of individual sources in the central region of NGC 6334 I. We compare these images to images at a variety of other wavelengths from the near infrared to cm radio continuum and speculate on the nature of the NGC 6334 I sources. We assert that the cometary shape of the UCHII region here, NGC 6334 F, is due to a champagne-like flow from a source on the edge of a molecular clump and not a due to a bow shock caused by the supersonic motion of the UCHII region through the interstellar medium. The mid-infrared emission in concentrated into an arc of dust that define the boundary between the UCHII region and the molecular clump. This dust arc contains a majority of the masers in the region. We discuss the nature of the four near-infrared sources associated with IRS-I 1, and suggest that one of the sources, IRS1E, is responsible for the heating and ionizing of the UCHII region and the mid-infrared dust arc. Infrared source IRS-I 2, which has been thought to be a circumstellar disk associated with a linear distribution of methanol masers, is found not to be directly coincident with the masers and elongated at a much different position angle. IRS-I 3 is found to be a extended source of mid-infrared emission coming from a cluster of young dusty sources seen in the near-infrared.Comment: Accepted for publication by the Astrophysical Journal, 27 pages, 9 figure