24,974 research outputs found
Electrodeposition of arrays of Ru, Pt, and PtRu Alloy 1D metallic nanostructures
No full textArrays of Ru, Pt, and PtRu one dimensional 1D nanowires NWs and nanotubes NTs were prepared by electrodeposition through the porous structure of an anodic aluminum oxide AAO membrane. In each case, micrometer-long NW and NT were formed with an outer diameter of ca. 200 nm, close to the interior diameter of the porous AAO membrane. Arrays of NW and NT can be formed by varying the metallic salt concentration, the applied potential, and the conductivity of the electrolyte. The Ru and Pt deposition rates were measured in the various deposition conditions, using an electrochemical quartz crystal microbalance. The mechanisms responsible for the formation of Ru and Pt NW and NT are discussed based on the observed deposition rates and models found in the literature. Finally, it is shown that arrays of PtRu alloy NT and NW can be readily prepared and their compositions can be varied over the whole compositional range by changing the metallic salt concentration of the electrodeposition bath
Quaterpyridine Ligands for Panchromatic Ru(II) Dye Sensitizers
No full textA new general synthetic access to carboxylated quaterpyridines (qpy), of interest as ligands for panchromatic dyesensitized solar cell organometallic sensitizers, is presented. The strategic step is a Suzuki−Miyaura cross-coupling reaction,
which has allowed the preparation of a number of representative unsubstituted and alkyl and (hetero)aromatic substituted qpys.
To bypass the poor inherent stability of 2-pyridylboronic acid derivatives, we successfully applied N-methyliminodiacetic acid
(MIDA) boronates as key reagents, obtaining the qpy ligands in good yields up to (quasi)gram quantities. The structural,
spectroscopic (NMR and UV−vis), electrochemical, and electronic characteristics of the qpy have been experimentally and
computationally (DFT) investigated. The easy access to the bis-thiocyanato Ru(II) complex of the parent species of the qpy
series, through an efficient route which bypasses the use of Sephadex column chromatography, is shown. The bis-thiocyanato
Ru(II) complex has been spectroscopically (NMR and UV−vis), electrochemically, and computationally investigated, relating its
properties to those of previously reported Ru(II)−qpy complexes.“This document is the Accepted Manuscript version of a Published Work that appeared in final form in [The Journal of Organic Chemistry], copyright © American Chemical Society after peer review and technical editing by the publisher
Photochemical ligand ejection from non-sterically promoted Ru(ii)bis(diimine) 4,4′-bi-1,2,3-triazolyl complexes
No full textComplexes of the form [Ru(diimine)2(btz)]2+ (btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl) are observed to undergo photochemical ejection of the btz ligand in the absence of any promotion through steric congestion to generate cis-bis(solvent) complexes [Ru(diimine)2(solvent)2]2+.
Graphical abstract: Photochemical ligand ejection from non-sterically promoted Ru(ii)bis(diimine) 4,4′-bi-1,2,3-triazolyl complexe
EXAFS, DFT, light-induced nucleobase binding, and cytotoxicity of the photoactive complex cis-[Ru(bpy)2(CO)Cl]+
No full textThe aqueous photochemistry of cis-[Ru(bpy)2(CO)Cl]+ (1) was investigated at 310 K and under visible light (white) irradiation by NMR and ESI-HR-MS. Complex 1 releases a Cl ligand, coordinates a solvent molecule, and forms the complex cis-[Ru(bpy)2(CO)(H2O)]2+ (2). Also, irradiation experiments were performed in the presence of the nucleobase derivatives 9-ethylguanine (9-EtG) and 9-ethyladenine (9-EtA). Formation of Ru-9-EtG adducts was observed after 3 h irradiation by NMR and HR-MS, while only very small amounts of a Ru-9-EtA adduct could be detected by HR-MS. Solution structural data were obtained by X-ray absorption spectroscopy (XAS) for both 1 and 2. EXAFS gave a Ru−Cl distance of 2.416(7) Å for 1 and a Ru−OH2O distance of 2.102(6) Å for 2. DFT and TDDFT were employed to study the photophysical and photochemical properties of 1. Calculations show that dissociative metal-centered states can be related to the light-induced release of a Cl ligand and subsequent coordination of a solvent molecule. The compound showed no antiproliferative activity in three human carcinoma cell lines (lung, bladder, pancreas) under the testing conditions, either with or without irradiation with UV light
白金微粒/Ru錯合物/高分子薄磨修飾電極之製備及其電催化應用
No full text[[abstract]]Membrane-metal modified cells are usually applied to the field of membrane cells, such as fuel cells, light cells… etc. Some hydrogen evolution catalysts, for example Pt metal, are used as the cathodes in these cells. Therefore, in this research, we try to dose a series of Ru complexes into the intervals between the cathode and the thin film electrode to improve the hydrogen evolution efficiency of the membrane-metal modified cells.
Ru complex (chosen from Ru(bpy)2phenNH2, Ru(dmb)2 phenNH2, Ru(tmb)2phenNH2, Ru(bpy)2Cl2, Ru(dmb)2Cl2, Ru(tmb)2Cl2) doped Nafion solution was drop-coated onto glassy carbon (GC) electrode and formed a thin film after drying. Then, the GC electrode was immersed into H2PtCl6 solution, and the Pt/Ru complex/polymer modified electrode was obtained by reducing Pt with a DPTB method. Different amount of Pt was electroplated on the GC electrode even at the same conditions (the same potential, the same time interval) when different consistency or kinds of Ru complexes were used, suggesting the influence of the ligands on the red-ox property of Ru complexes. The effective surface area (estimated by CV method) of Pt in the modified electrode is also varied with different species of Ru complexes, which in turn affect on the efficiency of hydrogen evolution.
Furthermore, from the information obtained by SEM and EDS, the alignment and the density of Pt particles growing on the GC electrode are figured out. From the fluorescence lifetime and luminescence spectra, a good electron-transfer is considered to have occurred between D series Ru complexes and Pt modified electrode that explained why a high hydrogen evolution efficiency has been obtained. The modified electrodes are still stable one month after fabricated and their hydrogen evolution efficiency was as good as a newly prepared one.
Modeling and interpreting element ratios in water and sediments: A sensitivity analysis of post-Chernobyl Ru : Cs ratios.
No full textWhen elements are simultaneously added to lakes, experimentally or by accident, their ratios in the water phase and in bottom sediments can change with time due to differential partitioning between solution and suspended particles or sediments. A number of equations are developed to show the change of ratio with time in water and sediments assuming simultaneous pulse inputs followed by a range of combinations of loss processes from solution (i.e. hydraulic losses, sorption to particles followed by settling, and diffusion into the sediments). The pattern of events is discussed both for pulse events with specific limiting assumptions and for combined continuous and pulse inputs. The models show that elemental ratios in sediments are generally less sensitive indicators of differential partitioning than are elemental ratios in water. For lakes with long residence times, the long-term elemental ratio in the sediments does not differ from that in the initial spike to the water column, but for short residence times, it is directly dependent on the ratio of either partition or diffusion coefficients. The models are used to interpret Ru : Cs ratios measured in the water and sediments of Esthwaite Water subsequent to the pulse input of Chernobyl fallout. The ratios can be explained by assuming nuclides were lost either by flushing and sorption or by flushing, sorption, and diffusion. The process combination of flushing and diffusion is incompatible with the observed constant ratios
Reprogramming of mesenchymal stem cells and adult fibroblasts following nuclear transfer in rabbits
No full textThe main aim of this thesis was to find out which donor cells would be most suitable for production of cloned rabbits with a targeted modification of their genome, and their corresponding patterns of reprogramming hetero- and euchromatic histone modifications (H3K4m2/3 and H3K27m3). For these purposes, we carried out NT with rabbit mesenchymal stem cells (MSCs) and adult fibroblasts (RAFs). As totally 13 cell lines of MSCs have been tested, they didn’t show stably higher development potential than RAFs, even though the blastocyst rate of embryos cloned from MSC A/B reached to 76%. Finally two cloned rabbits were produced from meschnymal stem cells. H3K27m3 was undetectable in all stages of nuclear transfer embryos except for one cell stage and blastocysts. It seems that H3K27m3 is faithfully reprogrammed in transferred nuclei of all donor cell types, with minor differences in zygotes and blastocysts. Strong signals for H3K4m2/3 were detected at the one to two-cell stages of in vivo embryos with a slight decrease at the 4-cell stage, followed by a more drastic decrease at the 8-cell stage, where the signal minimum was reached. In 16-cell embryos signals slightly increased and then reached in morulae and blastocysts the levels observed in one-two cell embryos. In all types of nuclear transfer embryos fluorescence intensity ratios differed from that of in vivo embryos. The minimum was not reached at the 8-cell stage but at the 4-cell stage. Reprogramming of H3K4m2/3 modification occurred quite differently with either type of cells irrespective of the cell origin or type and no close similarities in the patterns of this reprogramming was observed between in vivo and nuclear transfer embryos. Embryos cloned from MSC A/B differed from all others in the way that H3K4m2/3 was generally lower and remained in the range of the donor cells. This suggests that reprogramming of H3K4m2/3 modification is more aberrant with MSC A/B cells than with any other cell type used in this study. However, with MSC A/B cells, a significantly higher or similar proportion of cloned embryos developed to blastocysts indicating that reprogramming of H3K4m2/3 modification does not correlate with developmental potential of donor cells. In conclusion, our study provides evidence that histone modifications for heterochromatin are faithfully reprogrammed during NT of rabbit somatic cells, while patterns of epigenetic reprogramming of euchromatic histone modifications differ between individual cell lines irrespective of their origin or type and are not correlated with their developmental potential. Although MSCs were not superior to RAFs in respect to the criteria tested in our study they may be suitable nuclear donors for generating transgenic cloned rabbits due to their high developmental plasticity
The application of antibodies in optical and electrochemical transduction processes
No full textChapter 1 relates the background information of the structure of antibodies, the nature of their interaction with antigen and their production as polyclonal antibodies. Examples of antibodies which have been produced against luminescent molecules are given and it is illustrated how the specific interaction of antibodies with luminescent complexes can be used to gain information on the structure, function and rotational dynamics of antibodies. The principle features of immunoassays are outlined with a focus on amperometric immunosensing including some areas of active research within amperometric immunosensing. This serves as a general introduction to Chapter 4; the development of an amperometric immunosensor based on single wall carbon nanotubes.
Chapter 2 begins with a review of the fundamental chemical, photochemical and electrochemical properties of Ru(II) and Os(II) polypyridyl complexes. It is shown how their photophysical properties can be modulated by the interaction of the complexes with biomolecules such as proteins, nucleic acids and antibodies. The synthesis and characterisation of [Os(bpy)2dcbpy] and some related Os(II) and Ru(II) complexes is described. The production and characterisation of a [Os(bpy)2dcbpy]-thyroglobulin conjugate which was used as the immunogen is described, as well as the purification and characterisation of the resulting polyclonal antibody. Competition ELISA served to confirm the cross-reactivity of the antibody with the Os and Ru complexes synthesised.
Chapter 3 describes the effect of antibody binding on the spectrochemical properties of the complexes. Changes in the emission spectra and lifetimes were examined. Association constants were derived from emission titrations. The extent that the antibody binding site protects the complexes from excited state deactivation via interaction with solvent was investigated. The possibility of energy transfer from [Ru(bpy)2dcbpy] to [Os(bpy)2dcbpy] when both were bound to the same antibody was investigated, as were the effects of antibody binding to a self-assembled layer of [Os(bpy)2(p2 p)2]2+.
Chapter 4 begins with an introduction to the structure and properties of CNTs and outlines their application thus far in biosensing. The assembly of oxidatively shortened SWNTs onto Nafion/iron oxide coated pyrolytic graphite electrodes is described and characterised by both AFM and resonance Raman spectroscopy. The immunosensing strategy investigated involved the adsorption of anti-biotin antibody to the carbon nanotube surface. The presence of HRP-labelled biotin was determined via the reduction of hydrogen peroxide in the presence of the soluble mediator hydroquinone. A short investigation is also presented on the ability of HRP-modified SWNT forest electrodes to detect H2O2 produced by a mutant catalase negative E. coli bacteria which was co-immobilised with the HRP. Recommendations for future work arising from this thesis are given in Chapter 5
Single-atom Ru catalyst for selective synthesis of 3-pentanone via ethylene hydroformylation
No full textA Ru single-atom (Ru SA) catalyst supported on activated carbon was adopted to synthesize 3-pentanone with 83.3% selectivity via heterogeneous ethylene hydroformylation, while 52.1% ethane selectivity was obtained for Ru nanoparticles (Ru NPs). The atomically dispersed Ru species with oxidation state (Ruδ+) and Ru-C4O coordination structure were identified as the active sites for efficient C-C coupling to generate 3-pentanone, while metallic Ru nanoparticles exhibited high activity for ethylene hydrogenation to ethane. Density functional theory (DFT) calculation revealed that the energy barrier of the direct coupling of C2H5CO∗ with C2H5∗ to form 3-pentanone on Ru SA was much lower than that on Ru NPs. As a result, the formation of 3-pentanone over Ru SA was more favourable than propanal, which was admittedly generated via coupling of C2H5CO∗ and H∗. This strategy may provide a potential green route for the one-pot synthesis of 3-pentanone with high atomic economy.No Full Tex
Photophysical Characterization of Ru Nanoclusters on Nanostructured TiO<sub>2</sub> by Time-Resolved Photoluminescence Spectroscopy
No full textDespite the promising performance of Ru nanoparticles or nanoclusters on nanostructured TiO2 in photocatalytic and photothermal reactions, a mechanistic understanding of the photophysics is limited. The aim of this study is to uncover the nature of light-induced processes in Ru/TiO2 and the role of UV versus visible excitation by time-resolved photoluminescence (PL) spectroscopy. The PL at a 267 nm excitation is predominantly due to TiO2, with a minor contribution of the Ru nanoclusters. Relative to TiO2, the PL of Ru/TiO2 following a 267 nm excitation is significantly blue-shifted, and the bathochromic shift with time is smaller. We show by global analysis of the spectrotemporal PL behavior that for both TiO2 and Ru/TiO2 the bathochromic shift with time is likely caused by the diffusion of electrons from the TiO2 bulk toward the surface. During this directional motion, electrons may recombine (non)radiatively with relatively immobile hole polarons, causing the PL spectrum to red-shift with time following excitation. The blue-shifted PL spectra and smaller bathochromic shift with time for Ru/TiO2 relative to TiO2 indicate surface PL quenching, likely due to charge transfer from the TiO2 surface into the Ru nanoclusters. When deposited on SiO2 and excited at 532 nm, Ru shows a strong emission. The PL of Ru when deposited on TiO2 is completely quenched, demonstrating interfacial charge separation following photoexcitation of the Ru nanoclusters with a close to unity quantum yield. The nature of the charge-transfer phenomena is discussed, and the obtained insights indicate that Ru nanoclusters should be deposited on semiconducting supports to enable highly effective photo(thermal)catalysis.QN/Afdelingsburea
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