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Viewing upcoming talks containing the keyword: 3
Tailoring the Photophysics of First-row Transition Metal-based Chromophores for Light Capture and Conversion: Challenges and Opportunities
Speaker: Jim McCusker (Michigan State)
Figure 1. P lot of the ground state recovery dynamics of [Fe(bpy) 3 ](PF 6 ) 2 in CH 3 CN solution as a function of temperature following 1 A 1 ® 1 MLCT excitation . The solid line corresponds to a fit of the data to an Arrhenius mod el, indicating an activation energy of 310 ± 15 cm -1 and an intercept (i.e., the rate constant in the limit of no barrier) of 230 ± 20 ps -1 . An analysis of these data in the context of semiclassical non - radiative decay theory is providing new insights into the factors controlling ultrafast dynamics in such systems. Tailoring the Photophysics of First - row Transition Metal - based Chromophores for Light Capture and Conversion: Challenges and Opportunities James K. McCusker Department of Chemistry, Michigan State University
The conversion of light to chemical energy is one of the most fundamental processes on Earth. It is the basis of photosynthesis, in which light absorption results in the separation of charge that ultimately creates the chemical potential needed to drive ATP synthesis; an advantageous by - product of th is process is, of course, O 2 production. Ironically, photosynthesis is also the source of the biomass from which the fossil fuels that constitute the basis of society’s energy infrastructure are derived. The overwhelming majority of climate scientists are in agreement that it is the burning of these fossil fuels – in effect the re - release of what was sequestered carbon into the atmosphere – that is driving global climate change. Options for shifting away from fossil fuels as our primary energy source genera lly revolve around renewables such as wind, solar, biomass, nuclear, geothermal, and hydro: of these, the only renewable energy source that is limitless and carbon - free (at least in principle) is solar. The energy flux hitting the Earth is 120,000 TW: inte grated over a 24 - hour period, this translates to humankind’s total energy budget for an entire year. Despite the progress that has been made in the implementation of solar energy (due primarily to reductions in the cost of silicon), the intermittent nature of solar energy, the balance of systems costs that continue to represent a significant economic obstacle, combined with the fact that electricity constitutes only ~30% of the global energy footprint all underscore the need for continued research in solar energy conversion science. Fundamental research on solar energy conversion – which will ultimately lead to the next generation of solar energy technologies – has sought to replicate Nature’s solution through the creation of artificial constructs that mimic va rious aspect of photosynthesis. When considering large - scale (i.e., global) implementation of any solar energy conversion scheme, material availability becomes a critically important consideration in the light - capture part of the problem, particularly w hen one considers the projected two - to three - fold increase in energy de mand over the next 30 - 40 years. Unfortunately, virtually all of the molecule - based approaches for solar energy conversion that have been proven successful rely on some of the least abu ndant elements on earth. An obvious alternative is to employ chromophores based on earth - abundant materials: for transition metal - based approaches, this means moving away from the second - and third - row transition series elements (e.g., ruthenium) and devel op photoredox - active chromophores based on first - row, widely available metals like iron and copper. As our group first demonstrated in 2000, the central problem with this approach is that the charge - transfer excited states that lie at the heart of photo - in duced electron transfer chemistry exhibit sub - picosecond lifetimes (as compared to the microsecond lifetimes of their 2 nd - and 3 rd - row congeners). Our research program therefore focuses on understanding the factors that determine the dynamics associated wi th the excited states of first - row transition metal - based chromophores, with the ultimate goal of circumventing and/or redefining their intrinsic photophysical properties in order to make feasible their use as light - harvesting components in solar energy co nversion schemes . This seminar will describe the key experimental results establishing this paradigm, as well as survey several approaches that we are pursuing in an effort to broaden the utility of this class of chromophores for a wide range of solar ener gy and chemical transformations . Download PDF
On: March 4, 2019 From: 13h00 To: 14h00View talk
Speaker: Veronique Gouverneur (Oxford)
The impact of fluorine chemistry in the life sciences is enormous. As many as 30−40% of agrochemicals and 20% of pharmaceuticals on the market are estimated to contain fluorine. 19F - and 18F -labelled compounds are also finding increasing applications in i maging such as Magnetic Resonance Imaging [MRI] or Positron Emission Tomography [PET]. As a result, there is an increasing demand for facile methods allowing for the fluorination using 19F and the radioisotope 18F of a large variety of structurally complex and functionalised small molecules as well as biologics. This lecture will discuss our recent contributions to the field of late stage fluorination with an emphasis on the challenges associated with the use of alkali metal fluoride, and how these can be o vercome. Download PDF
On: March 11, 2019 From: 14h00 To: 15h00View talk
Speaker: Timothy Noel (Eindhoven)
Innovation in synthetic methodology through use of flow T i m o t h y N o ë l E i n d h o v e n U n i v e r s i t y o f T e c h n o l o g y , D e p a r t m e n t o f C h e m i c a l E n g i n e e r i n g & C h e m i s t r y , M i c r o F l o w C h e m i s t r y & S y n t h e t i c M e t h o d o l o g y , E i n d h o v e n , T h e N e t h e r l a n d s E-m a i l : t . n o e l @ t u e . n l ; w e b s i t e : w w w . N o e l R e s e a r c h G r o u p . c o m ; T w i t t e r : @ N o e l G r o u p T U E
Until recently, many reactions have been exclusively performed in co nventional batch LabWare. With the advent of microreactor technology, significant effort has been devoted to develop a wide variety of continuous -flow techniques to facilitate organic synthesis. Microreactor technology offers several advantages compared to traditional batch reactors, such as, enhanced heat - and mass -transfer, improved irradiation, safety of operation and the possibility to integrate several reaction steps and subsequent separations in a single streamlined process. 1 My group has taken a grea t interest in assisting chemists by developing automated and flow -based reaction technologies capable of reducing manual labor, increasing the reproducibility of the results and accelerating reaction discovery. In this presentation, we will give an overvie w of our synthetic methodology development, exemplified by photoredox catalysis 2, C –H activation chemistry 3 and electrochemistry 4 and how these synthetic methods were impacted by continuous -flow microreactor technology. Furthermore, we will discuss the dev eloped technology and reaction models in detail.
1. (a) H. P. L. Gemoets, Y. Su, M. Shang, V. Hessel, R. Luque, T. Noel, Chem. Soc. Rev. 2016 , 45 , 83 -117. (b) D. Cambie, C. Bottecchia, N. J. W. Straathof, V. Hessel, T. Noel, Chem. Rev. 2016 , 116 , 10276 -10341.
2. (a) X. -J. Wei, W. Boon, V. Hessel, T. Noel, ACS Catal. 2017 , 7, 7136 -7140. (b) C. Bottecchia, M. Rubens, S. Gunnoo, V. Hessel, A. Madder, T. Noel, Angew. Chem. Int. Ed. 2017 , 56 , 12701 -12707. (c) D. Cambie, F. Zhao, V. Hessel, M. G. Debije, T. Noel, Angew. Chem. Int. Ed. 2017 , 56 , 1050 -1054. (d) N. J. W. Straathof, S. E. Cramer, V. Hessel, T. Noel, Angew. Chem. Int. Ed. 2016 , 55 , 15549 -15553.
3. (a) G. Laudadio, S. Govaerts, Y. Wang, D. Ravelli, H. F. Koolman, M. Fagnoni, S. W. Djuric, T. Noel, Angew. Chem. Int. Ed. 2018 , 57 , 4078 -4082.. (b) H. P. L. Gemoets, G. Laudadio, K. Verstraete, V. Hessel, T. Noel, Angew. Chem. Int. Ed. 2017 , 56 , 7161 -7165. (c) U. K. Sharma, H. P. L. Gemoets, F. Schoeder, T. Noel, E Van der Eycken, ACS Catal. 2017 , 7, 3818 -3823.
4. (a) G. Laudadio, W. De Smet, L. Struik, Y. Cao, T. Noel, J. Flow Chem. 2018 , 8, 157 -165. (b) G. Laudadio, N. J. W. Straathof, M. D. Lanting, B. Knoops, V. Hessel, T. Noel, Green Chem. 2017 , 19 , 4061 -4066.
med and being readable. Download PDF
On: March 13, 2019 From: 14h00 To: 15h00View talk
Cond Mat Seminars
Speaker: Pablo Burset (Aalto University, Finland)
In superconducting spintronics, it is essential to generate spin-triplet Cooper pairs on demand. Up to now, proposals to do so concentrate on hybrid structures in which a superconductor (SC) is combined with a magnetically ordered material (or an external magnetic field). We, instead, identify a novel way to create and isolate spin-triplet Cooper pairs in the absence of any magnetic ordering . This achievement is only possible because we drive a system with strong spin-orbit interaction--the Dirac surface states of a strong topological insulator (TI)--out of equilibrium. In particular, we consider a bipolar TI-SC-TI junction, where the electrochemical potentials in the outer leads differ in their overall sign. As a result, we find that nonlocal singlet pairing across the junction is completely suppressed for any excitation energy. Hence, this junction acts as a perfect spin triplet filter across the SC generating equal-spin Cooper pairs via crossed Andreev reflection.In this talk, I will first describe how spin-triplet pairing can be induced on the surface state of a three-dimensional TI . An additional magnetic element, either a ferromagnet or an external field, results in a rich subgap structure with two effective gaps that depend on the orientation of the magnetization. Then, I will review a recent experiment where the proximity-induced superconducting state in the three-dimensional TI HgTe was studied using electronic transport of a normal metal-superconducting point contact as a spectroscopic tool . Finally, I will describe our proposal for engineering spin-triplet Cooper pairs at a bipolar TI-SC-TI hybrid junction without any magnetic element .  D. Breunig, P. Burset, B. Trauzettel. Phys. Rev. Lett. 120, 037701 (2018).  P. Burset, B. Lu, G. Tkachov, Y. Tanaka, E.M. Hankiewicz, B. Trauzettel. Phys. Rev. B 92, 205424 (2015).  J. Wiedenmann, E. Liebhaber, J. Kübert, E. Bocquillon, P. Burset, C. Ames, H. Buhmann, T. M. Klapwijk, L. W. Molenkamp. Phys. Rev. B 96, 165302 (2017).
On: March 13, 2019 From: 13h00 To: 14h00View talk
Speaker: Muriel Hissler (Rennes)
Advances in P - based Molecular Materials for Opto -electronic Application Pr Muriel HISSLER Université de Rennes1, CNRS, UMR 6226, Institut des Sciences Chimiques de Rennes, Campus de Beaulieu, 35042 Rennes, France Since the pioneering work of Shirakawa , Heeger and McDiarmid in the 1970’s, the interest for organic -conjugated systems has grown tremendously. Indeed organic materials offer the possibility to process light -weight, flexible electronic devices, however, they have to satisfy a large number of technical requirements in order to be stable and efficient in the device. The insertion of a heteroelement into the backbone has appeared as an appealing way to tune the properties of the materials. Heterocycles like thiophene , pyrrole, and their derivatives are now widely used to modify chemical and physical properties of -conjugated systems. Interestingly, while organophosphorus derivatives have been investigated for decades, their insertion into devices has only been achiev ed recently. The high reactivity and toxicity of many P -derivatives is one of the reason but the ability of chemists to stabilize and protect the P -atom allowed the introduction of organophosphorus derivatives into opto -electronic devices. Here, we will re port on phosphorus based molecular materials: their synthesis, their unique properties useful for organic electronic materials, and the devices that they have been incorporated in so far. For example, we have shown that phosphorus heterocycles (phospholes, phosphetes, phosphepines…) are appealing building blocks for the construction of - conjugated systems. Effectively, the reactivity of the P -center allows a straightforward HOMO - LUMO gap tuning as evidence by photophysical and electrochemical studies. The coordination ability of the P - center allows unprecedented coordination -driven assembly of -systems onto transition metals. All these physical properties make phosphorus heterocycles valuable building blocks for the development of material for optoelectron ic applications.
Keywords: Heterochemistry, Phosphorus heterocycles, Aromaticity, -systems, Organic Optoelectronics References:  D. J oly, D.; P. A. Bouit, M. Hissler, J. Mater. Chem. C 2016 , 4, 3686.  M. P. Duffy, W. Delaunay, P.A. Bouit, M. Hissler, Chem. Soc. Rev. 2016 , 45, 5296. Optoelectronic Applications OLEDs, Solar cells, OFETs… P Oligomers, Polymers, Polycycles … Organophosphorus -conjugated systems P -chemistry / Heterochemistry / Organometallics Download PDF
On: March 20, 2019 From: 14h00 To: 15h00View talk
Speaker: Sebastian Schulz (School of Physics and Astronomy)
Nonlinear effects hold great potential for a wide range of applications - all-optical signal processing, beam shaping and steering, optical computing, sensing, detection and general meteorology, to name a few. However, typically non-linear effects are weak; a typical non-linear index change is on the order of 0.01% or less and therefore they typically require high-power, short-pulse lasers, as well as long interaction length or resonant enhancement. Here, we show that a thin metasurface (50 nm total thickness), consisting of metal antennas on an epsilon-near-zero (ENZ) film, can produce a giant non-linear response with the refractive index change, Δn , exceeding 2 across a broad spectral range in the near-infrared wavelength region.
On: March 26, 2019 From: 13h00 To: 14h00View talk