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Viewing upcoming talks containing the keyword: 10
Speaker: Tim Softley (Oxford)
As temperatures are lowered below 1K, gas phase chemical processes enter a new physical regime, as they start to undergo a transition from a classical collision picture to one dominated by quantum (wave-like) behaviour. The deBroglie wavelength for translational motion gets progressively longer, becoming greater than the range of molecular interactions. Thermal averaging is lessened and thus the opportunities for precise control of chemical processes are enhanced. We aim to explore this novel physical regime for chemistry taking advantage of recently developed technology for producing cold atoms and molecules. Laser-cooled atomic ions, and sympathetically cooled molecular ions provide ideal targets for studying reactive collisions at very low temperatures when combined with sources of cold neutral atoms and molecules. We have commissioned several cold neutral sources including a Stark decelerator and buffer-gas cooled quadrupole guide, both suitable for use with dipolar molecules, and a Zeeman decelerator and a photodissociation source, suitable for paramagnetic species. Progress in developing these sources and combining them with trapped ions for studying the dynamics and kinetics of chemical processes at ultralow temperatures will be presented.
On: September 24, 2014 From: 15h30 To: 16h30View talk
Speaker: Prof Bart Jan Ravoo (University of Muenster)
Selfâ€assembly is emerging as a superior method to prepare adaptive and responsive nanomaterials. Responsive multivalent interactions are key to such versatile materials. This lecture will highlight soft material composed of cyclodextrins and/or superparamagnetic nanoparticles. It will be shown that using the hostâ€guest chemistry of cyclodextrins, we can form hydrogels as well as nanocapsules. We can also make “magnetic vesicles” that selfâ€assemble in microscale linear aggregates in aqueoussolution under the influence of a magnetic field. The metastable linear aggregates can be stabilized by a noncovalent and photoresponsive crossâ€linker, which can be photoisomerized between an adhesive and a nonadhesive configuration. Thus, the hybrid material responds to magnetic field as well as to light and a stable selfâ€assembled structure can only be obtained in a magnetic field in the presence of the noncovalent crossâ€linker. We have recently extended this strategy to superparamagnetic nanoparticles modified with cyclodextrin. These hybrid nanoparticles can befurther functionalized using host guest interaction and molecular recognition and they can be used to capture and isolate proteins.
References:1. A. Samanta, B. J. Ravoo, Angew. Chem. Int. Ed. 2014, 53, 12946–12950.2. S. Himmelein, V. Lewe, M. C. A. Stuart, B. J. Ravoo, Chem. Sci. 2014, 5, 1054â€1058.3. J. H. Schenkel, A. Samanta, B. J. Ravoo, Adv. Mater. 2014, 26, 1076–1080.
On: August 24, 2015 From: 15h30 To: 16h30View talk
Speaker: Prof Osamu Ishitani (Tokyo Institute of Technology)
Both the problems of the global warming and shortage of the fossil fuels have brought about great interest in photochemical utilization of CO2 with solar energy. Efficient photocatalysts for CO2 reduction must be necessary for development of such an important technology.
We have developed novel types of photocatalytic systems using metal complexes and/or semiconductors as a photocatalyst.1 In this presentation, I will focus on the architecture of two types of the photocatalysts using transition metal complexes:
(1) A mixed photocatalytic system including a ring-shaped Re(I) multinuclear complex as a photosensitizer2
(2) Ru(II)-Re(I) and Ru(II)-Re(I) supramolecular photocatalysts.3
The efficiency of the former photocatalytic system has been highest in the reported CO2-reduction photocatalysts (ï† = 82%), and the latter photocatalysts have been most robust (TON > 3000).
On: September 11, 2015 From: 15h30 To: 16h30View talk
Physics and Astronomy Colloquia
Speaker: Professor Isabelle Ledoux-Rak (Laboratoire de Photonique Quantique et MolÃ©culaire, Ecole Normale SupÃ©rieure de Cachan, France)
2015 Holweck Prize Lecture
Joint Physics/Chemistry Colloquium
The emergence of molecular photonics at the cross-roads of physics, chemistry and device engineering has being triggered by increasing demand in various fields such as high bitrate telecommunications, sensors, and bio-imaging. The wealth of molecular structures and the exploitation of their functional and structural flexibility opens-up new, exciting horizons for this area of research. Designing highly efficient molecules with optimised photonic properties remains a major challenge after 50 years of continuous development, based on fruitful and interdisciplinary cooperation between chemists and physicists.
In this lecture, the principles of molecular engineering for quadratic nonlinear optics will be discussed, with an emphasis on metal complexes and lanthanide derivatives, on nonlinear optical characterization methods. This will be followed by a review of intermolecular interactions and various orientation methods, in order to bridge the gap between molecules to materials, towards a wide range of applications. Finally, perspectives will be provided on molecular photonics towards device–rel.
On: September 16, 2015 From: 17h15 To: 18h30View talk
Physics and Astronomy Colloquia
Speaker: Prof James F Scott (University of St Andrews)
Multiferroics are crystals that simultaneously exhibit ferromagnetism and ferroelectricity (and usually ferroelasticity, which is hysteretic stress/strain). In some cases the ferromagnetism is actually created by the ferroelectricity, by causing the spins to cant [via Dzyaloshinskii-Moriya anisotropic exchange: P.(L x M)]. These materials have become very popular in part due to the interesting new physics, previously neglected because the effects require very low crystal symmetry, and because they offer the promise of new kinds of memory devices, including voltage-tunable magnetic tunnel junctions and four-state memories (+P,+M; +P,-M; -P,+M; -P,-M) which would be vastly superior to the usual binary (0,1) Boolean algebra. At St. Andrews I am experimentally studying GaFeO3 and Pb[Fe(1/2)Ta(1/2)]y[Ti(1/2)Zr(1/2)(1-y)]O3.
On: September 25, 2015 From: 10h00 To: 11h00View talk