10 research outputs found
Simple direct formation of self-assembled N-heterocyclic carbene monolayers on gold and their application in biosensing
CRL acknowledges the Engineering and Physical Sciences Research Council (UK) for the funding of his PhD studentship (EP/M506631).The formation of organic films on gold employing N-heterocyclic carbenes (NHCs) has been previously shown to be a useful strategy for generating stable organic films. However, NHCs or NHC precursors typically require inert atmosphere and harsh conditions for their generation and use. Herein we describe the use of benzimidazolium hydrogen carbonates as bench stable solid precursors for the preparation of NHC films in solution or by vapour-phase deposition from the solid state. The ability to prepare these films by vapour-phase deposition permitted the analysis of the films by a variety of surface science techniques, resulting in the first measurement of NHC desorption energy (158±10 kJ mol−1) and confirmation that the NHC sits upright on the surface. The use of these films in surface plasmon resonance-type biosensing is described, where they provide specific advantages versus traditional thiol-based films.Publisher PDFPeer reviewe
Low-Frequency Spectral Energy Distributions of Radio Pulsars Detected with the Murchison Widefield Array
We present low-frequency spectral energy distributions of 60 known radio pulsars observed with the Murchison Widefield Array telescope. We searched the GaLactic and Extragalactic All-sky Murchison Widefield Array survey images for 200-MHz continuum radio emission at the position of all pulsars in the Australia Telescope National Facility (ATNF) pulsar catalogue. For the 60 confirmed detections, we have measured flux densities in 20 × 8 MHz bands between 72 and 231 MHz. We compare our results to existing measurements and show that the Murchison Widefield Array flux densities are in good agreement
Water Oxidation Catalyzed by Iridium Complexes Containing New Donor-Flexible Nitrogen Ligands.
Enhanced Catalytic Activity of Iridium(III) Complexes by Facile Modification of C,N-Bidentate Chelating Pyridylideneamide Ligands
A set of aryl-substituted pyridylideneamide
(PYA) ligands with variable donor properties owing to a pronounced
zwitterionic and a neutral diene-type resonance structure were used
as electronically flexible ligands at a pentamethylcyclopentadienyl
(Cp*) iridium center. The straightforward synthesis of this type of
ligand allows for an easy incorporation of donor substituents such
as methoxy groups in different positions of the phenyl ring of the
C,N-bidentate chelating PYA. These modifications considerably enhance
the catalytic activity of the coordinated iridium center toward the
catalytic aerobic transfer hydrogenation of carbonyls and imines as
well as the hydrosilylation of phenylacetylene. Moreover, these PYA
iridium complexes catalyze the base-free transfer hydrogenation of
aldehydes, and to a lesser extent also of ketones. Under standard
transfer hydrogenation conditions including base, aldehydes are rapidly
oxidized to carboxylic acids rather than reduced to the corresponding
alcohol, as is observed under base-free conditions
Optimization of Synthetically Versatile Pyridylidene Amide Ligands for Efficient Iridium-Catalyzed Water Oxidation
Allograft heart valve sterilization: A six-year in-depth analysis of a twenty-five–year experience with low-dose antibiotics
Stable mixed chimerism and tolerance using a nonmyeloablative preparative regimen in a large-animal model
A search for long-timescale, low-frequency radio transients
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present a search for transient and highly variable sources at low radio frequencies (150-200 MHz) that explores long timescales of 1-3 years. We conducted this search by comparing the TIFR GMRT Sky Survey Alternative Data Release 1 (TGSS ADR1) and the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey catalogues. To account for the different completeness thresholds in the individual surveys, we searched for compact GLEAM sources above a flux density limit of 100 mJy that were not present in the TGSS ADR1; and also for compact TGSS ADR1 sources above a flux density limit of 200 mJy that had no counterpart in GLEAM. From a total sample of 234 333 GLEAM sources and 275 612 TGSS ADR1 sources in the overlap region between the two surveys, there were 99658 GLEAM sources and 38 978 TGSS ADR sources that passed our flux density cutoff and compactness criteria. Analysis of these sources resulted in three candidate transient sources. Further analysis ruled out two candidates as imaging artefacts. We analyse the third candidate and show it is likely to be real, with a flux density of 182 +/- 26 mJy at 147.5 MHz. This gives a transient surface density of rho = (6.2 +/- 6) x 10-5 deg-2 . We present initial follow-up observations and discuss possible causes for this candidate. The small number of spurious sources from this search demonstrates the high reliability of these two new low-frequency radio catalogues.Peer reviewe