Viewing upcoming talks containing the keyword: 8
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ScotCHEM ColloquiaDihydrogen and Polyfunctional Ligands: Coordination Chemistry and Catalysis
Speaker: Sylviane Sabo-Etienne (Toulouse)
Dihydrogen and Polyfunctional L igands: Coordination Chemistry and Catalysis
More than 30 years ago, the proof by neutron diffraction that dihydrogen could be coordinated to a metal center without H -H bond breaking was published by Gregory Kubas and collaborators . The sigma dihydrogen complexes were born. Nearly at the same time, the concept of agostic interactions was established by Maurice Brookhart and Malcolm Green. Since then, many new complexes displaying agostic interactions or sigma coordination modes have been prepared, and applications in energy and catalysis have emerge d. If we want to control activity and selectivity issues, it is necessary to gain knowledge on the properties of this unique class of complexes which involves one (or in some cases two) three -centers, two -electron bonds. In this context, t his lecture will provide a few answers to the following points . How far can we define the hydrogen interaction with the metal center? Nowadays, we have access to a large variety of characterization techniques. Some of them might require sophisticated levels and be cost or/ and time expensive. Can we bypass them? How can we combine catalytic in situ monitoring , stoichiometric experiments , and various techniques to decipher the mechanism of a complex catalytic system? Download PDFOn: March 9, 2018 From: 12h00 To: 13h00
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Physics and Astronomy ColloquiaOrganohalide Perovskite Photodetectors
Speaker: Prof Paul Meredith (University of Swansea)
The light harvesting performance and tunability of organohalide perovskite semiconductors demonstrated in photovoltaic applications, leads to the obvious question as to whether they can be deployed as the junction in photodetectors. Indeed, these materials should in principle be able to rival other solution processed semiconductors such as the organics and inorganic quantum dots [1-3]. In my talk, I will describe recent progress to create a family of organohalide perovskite photodetectors based upon a simple thin film diode architecture. Applications include high detectivity broad-band photodiodes for the UV-Visible [4], single crystal NIR detectors [5], and narrow-band red, green, blue (RGB) systems [6] which deliver truly colour discriminative performance without the need for input optical filtering. The latter represent a completely new photodiode platform which could ultimately deliver the type of illuminant-independent imaging needed for machine and artificial vision.
[1] Solution-processed semiconductors for next-generation photodetectors”, F.P. García de Arquer, A. Armin, P. Meredith & E.H. Sargent, Nature Reviews Materials, 2, 16100 (2017).
[2] Thick junction broadband organic photodiodes, A. Armin, M. Hambsch, I.K. Kim, P.L. Burn, P. Meredith & E.B. Namdas, Laser and Photonics Reviews, 8(6), 924-932 (2014).
[3] Narrowband light detection via internal quantum efficiency manipulation of organic photodiodes, A. Armin, R. D. Jansen-van Vuuren, N. Kopidakis P. L. Burn & P. Meredith, Nature Communications, 6, 6343 (2015).
[4] Low noise, IR-blind organohalide perovskite photodiodes for visible light detection and imaging, Q. Lin, A. Armin, D.M. Lyons, P.L. Burn & P. Meredith, Advanced Materials, 27(12), 2060-2064 (2015);
[5] Near infrared photodetectors based on sub-gap absorption in organohalide perovskite single crystals, Q. Lin, A. Armin, P.L. Burn & P. Meredith, Laser and Photonics Reviews, 10(6), 1047-1053 (2016);
[6] Filterless, narrowband RGB photodetectors, Q. Lin, A. Armin, P.L. Burn & P. Meredith, Nature Photonics, 9, 687-694 (2015).
On: March 9, 2018 From: 10h00 To: 11h00
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EaStCHEM ColloquiaGuest binding and catalysed reactions in the cavity of a coordination cage
Speaker: Michael D Ward (Warwick)
Self -assembled coordination cages (hollow metal/ligand capsules) have the ability to encapsulate small molecule guests in the central cavity. In this talk is presented a coordination cage with a very well developed host guest chemistry, for which the factors responsible for guest binding have been dissected in detail to the extent that guest binding can be quantitatively predicted. The combination of b inding of hydrophobic guests in the cage cavity in water, and accumulation of anions around the positively -charged cage surface by ion -pairing, has led to his catalytic rate enhancements for reactions of cavity -bound guests with surface -bound anions. As g uest binding and ion -pairing are based on orthogonal interactions, this affords a system capable in principle of quite general bimolecular catalysis of reactions of electrophiles with anions. Download PDFOn: March 14, 2018 From: 15h30 To: 16h30
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EaStCHEM ColloquiaFrom Organometallic Chemistry to Colloidal Catalysts: The Case of Zinc and Copper Nanomaterials
Speaker: Charlotte Williams (Oxford)
The controlled synthesis of colloidal inorganic nanomaterials will be discussed, with a focus on the development of low temperature, solution processes using organ ometallic reagents. The controlled hydrolysis of organo -zinc reagents can be used to deliver either small, monodisperse colloidal zinc oxide nanoparticles or exfoliated 2 -D layered zinc hydroxide (LZH) nanosheets depending on the reaction conditions. The lecture will highlight how the relative stoichiometry of hydrolysable vs. non -hydrolysable ligands (i.e. ethyl vs. carboxylate) is used to control the product speciation and surface coverage. Characterization data on the nanomaterials will be presented, including various diffraction, spectroscopic and microscopy methods. Furthermore, recent studies to address the mechanism by which discrete organo -zinc reagents are converted to nanoparticles will be discussed, with a particular focus on the isolation of small zinc - oxide/hydroxide cluster compounds and the use of NMR spectroscopy to understand the hydrolysis reaction in more detail. The use of copper inorganic/organometallic compounds and the low pressure (3 bar) hydrogenation process or hydrolysis reac tion are used to prepare ultra -small, colloidal nanoparticles of Cu(0) or Cu2O. The synthesis method and redox cycling between the two copper redox states will be discussed, particularly in terms of the influence on nanoparticle size and speciation. The potential to apply the ZnO, Cu and Cu2O nanoparticles as catalysts for carbon dioxide hydrogenation reactions will be described, using a CSTR slurry reactor configuration. Download PDFOn: March 21, 2018 From: 15h30 To: 16h30
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EaStCHEM Colloquia
Phosphaborenes, RP : BR
Speaker: Michael Cowley (Edinburgh)
Phosphaborenes, RP=BR, are alkyne analogues which are also isoelectronic with iminoboranes, RNBR. In contrast to iminoboranes, phosphaborenes are unknown as sta ble compounds. Nevertheless, they are important synthetic targets because of their potential in small -molecule activation, as precursors for inorganic materials, and as ’synthons’ for the introduction of P/B units into organic compounds. I will present our recent results in obtaining stable phosphaborenes, generating transient (and highly reactive) phosphaborenes in solution, results in small -molecule activation, and the use of phosphaborenes to prepare new P/B isosteres of archetypal unsaturated organic co mpounds. Download PDFOn: March 28, 2018 From: 15h30 To: 16h30
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EaStCHEM ColloquiaChirality in flatland: intermolecular recognition, spin filtering and molecular machines at surfaces
Speaker: Karl-Heinz Ernst (Zurich)
Chirality in flatland: intermolecular recognition, spin filtering and molecular machines at surfaces
Karl -Heinz Ernst 1,2
1Nanoscale Materials Science, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH -8600 Dübendorf, Switzerland 2Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH -8057 Zürich, Switzerland
Molecular recognition among chiral molecules on surfaces is of paramount importa nce in biomineralization, enantioselective heterogeneous catalysis, and for the separation of chiral molecules into their two mirror -image isomers (enantiomers) via crystallization or chromatography. Understanding the principles of molecular recognition in general, however, is a difficult task and calls for investigation of appropriate model systems. One popular approach is thereby studying intermolecular interactions on well -defined solid surfaces, which allows in particular the use of scanning tunneling m icroscopy (STM). Examples of chiral amplification via the so -called ‘sergeant -and -soldiers’ effect as well as manipulation of chiral adsorbates via inelastic electron tunneling will be presented. In a Pasteur -type experiment at the nanoscale, molecules tha t constitute a dimer are spatially separated with a molecular STM tip and their absolute handedness is determined with submolecular resolution STM. Moreover, we report spin -dependent filtering of electrons by monolayers of these helical molecules. Finally the first successful electrical current -driven, unidirectional motion of a synthetic molecule will be presented (Fig. 1) . Fig. 1 : Sketch of the ‘nanocar’ on a surface . © DPA Ein win ziges N ano-Auto , da s elek trisch a ngetr ieben wir d: Da fü r ga b es den C hemie- Nobelpr eis 2 016. W arum N obe lpr eise so e in gr oße s D ing s ind ht tp: //www.faz.ne t/akt ue ll/feui lleton/ fam ilie/wie-erkl aere-ich- s-... 2 von 7 10/ 8/ 16, 5: 07 P M Download PDFOn: April 4, 2018 From: 15h30 To: 16h30
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