The Experts below are selected from a list of 14166 Experts worldwide ranked by ideXlab platform
Gunnar A Niklasson - One of the best experts on this subject based on the ideXlab platform.
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Ion Trapping and deTrapping in amorphous tungsten oxide thin films observed by real time electro optical monitoring
Chemistry of Materials, 2016Co-Authors: Miguel A Arvizu, Claesgoran Granqvist, M Moralesluna, Gunnar A NiklassonAbstract:Several technologies for energy saving and storage rely on Ion exchange between electrodes and electrolytes. In amorphous electrode materials, a detailed knowledge of Li-Ion intercalatIon is hamper ...
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eliminating degradatIon and uncovering Ion Trapping dynamics in electrochromic wo3 thin films
Nature Materials, 2015Co-Authors: Ruitao Wen, Claesgoran Granqvist, Gunnar A NiklassonAbstract:There is keen interest in the use of amorphous WO3 thin films as cathodic electrodes in transmittance-modulating electrochromic devices1–4. However, these films suer from Ion-Trapping-induced degra ...
Iryna Glushchenko - One of the best experts on this subject based on the ideXlab platform.
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nano objects and Ions in liquid crystals Ion Trapping effect and related phenomena
Crystals, 2015Co-Authors: Yuriy Garbovskiy, Iryna GlushchenkoAbstract:The presence of Ions in liquid crystals is one of the grand challenges that hinder the applicatIon of liquid crystals in various devices, which include advanced 3-D and flexible displays, tunable lenses, etc. Not only do they compromise the overall performance of liquid crystal devices, Ions are also responsible for slow response, image sticking, and image flickering, as well as many other negative effects. Even highly purified liquid crystal materials can get contaminated during the manufacturing process. Moreover, liquid crystals can degrade over time and generate Ions. All of these factors raise the bar for their quality control, and increase the manufacturing cost of liquid crystal products. A decade of dedicated research has paved the way to the solutIon of the issues mentIoned above through merging liquid crystals and nanotechnology. Nano-objects (guests) that are embedded in the liquid crystals (hosts) can trap Ions, which decreases the Ion concentratIon and electrical conductivity, and improves the electro-optical response of the host. In this paper, we (i) review recently published works reporting the effects of nanoscale dopants on the electrical properties of liquid crystals; and (ii) identify the most promising inorganic and organic nanomaterials suitable to capture Ions in liquid crystals.
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Ion Trapping by means of ferroelectric nanoparticles and the quantificatIon of this process in liquid crystals
Applied Physics Letters, 2015Co-Authors: Yuriy Garbovskiy, Iryna GlushchenkoAbstract:Nanoparticles embedded in liquid crystals can trap mobile Ions and decrease their concentratIon. In this paper, we generalize the nanoparticles-based approach and, through the quantitative analysis, identify the ferroelectric micro- and nanomaterials as the most promising “Ion traps” that ensure close to 100% liquid crystal purificatIon. We demonstrate that the treatment of liquid crystals with ferroelectric materials leads to a two-order of magnitude decrease in their electrical conductivity. This value exceeds previous data reported for similar systems by a factor of 10. Ferroelectric nanoparticles, when dispersed and stabilized in liquid crystals, act as highly efficient permanent Ion traps, solve the problem of uncontrolled Ionic contaminatIons, and eliminate the negative effects caused by Ions.
Zheng Ouyang - One of the best experts on this subject based on the ideXlab platform.
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Ion neutral collisIon effects on Ion Trapping and pseudopotential depth in Ion trap mass spectrometry
Journal of the American Society for Mass Spectrometry, 2019Co-Authors: Xinwei Liu, Xiaoyu Zhou, Zheng OuyangAbstract:Ion Trapping using radio-frequency (RF) devices has been widely used in mass spectrometry (MS). The pseudopotential well (PW) model enables the use of a pseudopotential depth, D, to evaluate the Ion Trapping capability of the RF devices in the pure electric field. It remains unclear how gas pressures regulate the Ion Trapping and D. Here, we calculated the D of a linear Ion trap (LIT) from 1 mTorr to 2 Torr, a pressure range critical for the operatIon of the RF devices, through Ion cloud simulatIons. Compared with the case of pure electric field, Ion-neutral collisIon effects at pressures of 1 to 100 mTorr were beneficial for the Ion Trapping and revealed an optimal Trapping depth, D, at around 10 mTorr. We explained the mechanism and validated the observatIon via Ion Trapping experiments performed in a home-made dual LIT mass spectrometer. We also showed that near the stability boundary, the RF heating became comparable with the D, which led to the decrement of Ion Trapping capability characterized by the available D.
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rectilinear Ion trap concepts calculatIons and analytical performance of a new mass analyzer
Analytical Chemistry, 2004Co-Authors: Zheng Ouyang, Yishu Song, Wolfgang R Plass, Graham R CooksAbstract:A mass analyzer based on a rectilinear geometry Ion trap (RIT) has been built, and its performance has been characterized. Design concepts for this type of Ion trap are delineated with emphasis on the effects of electrode geometry on the calculated electric field. The Mathieu stability regIon was mapped experimentally. The instrument can be operated using mass-selective instability scans in both the boundary and resonance ejectIon versIons. Comparisons of performance between different versIons of the device having different dimensIons allowed selectIon of an optimized geometry with an appropriate distributIon of higher-order electric fields. Comparisons made under the same conditIons between the performance of a conventIonal cylindrical Ion trap and a RIT of 4 times greater volume show an improvement of 40 times in the signal-to-noise ratio resulting from the higher Ion Trapping capacity of the RIT. The demonstrated capabilities of the RIT include tandem mass spectrometry, a mass resolutIon in excess of 1...
Paolo Melchiorre - One of the best experts on this subject based on the ideXlab platform.
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Studies on the Enantioselective Iminium Ion Trapping of Radicals Triggered by an Electron-Relay Mechanism.
Journal of the American Chemical Society, 2017Co-Authors: Ana Bahamonde, John Murphy, Marika Savarese, Éric Brémond, Andrea Cavalli, Paolo MelchiorreAbstract:A combinatIon of electrochemical, spectroscopic, computatIonal, and kinetic studies has been used to elucidate the key mechanistic aspects of the previously reported enantioselective iminium Ion Trapping of photochemically generated carbon-centered radicals. The process, which provides a direct way to forge quaternary stereocenters with high fidelity, relies on the interplay of two distinct catalytic cycles: the aminocatalytic electron-relay system, which triggers the stereoselective radical trap upon iminium Ion formatIon, and the photoredox cycle, which generates radicals under mild conditIons. Critical to reactIon development was the use of a chiral amine catalyst, bearing a redox-active carbazole unit, which could rapidly reduce the highly reactive and unstable intermediate generated upon radical interceptIon. The carbazole unit, however, is also involved in another step of the electron-relay mechanism: the transiently generated carbazole radical catIon acts as an oxidant to return the photocatalyst i...
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Asymmetric catalytic formatIon of quaternary carbons by iminium Ion Trapping of radicals
Nature, 2016Co-Authors: John Murphy, David Bastida, Suva Paria, Maurizio Fagnoni, Paolo MelchiorreAbstract:An important goal of modern organic chemistry is to develop new catalytic strategies for enantioselective carbon-carbon bond formatIon that can be used to generate quaternary stereogenic centres. Whereas considerable advances have been achieved by exploiting polar reactivity, radical transformatIons have been far less successful. This is despite the fact that open-shell intermediates are intrinsically primed for connecting structurally congested carbons, as their reactivity is only marginally affected by steric factors. Here we show how the combinatIon of photoredox and asymmetric organic catalysis enables enantioselective radical conjugate additIons to β,β-disubstituted cyclic enones to obtain quaternary carbon stereocentres with high fidelity. Critical to our success was the design of a chiral organic catalyst, containing a redox-active carbazole moiety, that drives the formatIon of iminium Ions and the stereoselective Trapping of photochemically generated carbon-centred radicals by means of an electron-relay mechanism. We demonstrate the generality of this organocatalytic radical-Trapping strategy with two sets of open-shell intermediates, formed through unrelated light-triggered pathways from readily available substrates and photoredox catalysts--this method represents the applicatIon of iminium Ion activatIon (a successful catalytic strategy for enantioselective polar chemistry) within the realm of radical reactivity.
David E Clemmer - One of the best experts on this subject based on the ideXlab platform.
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Ion Trapping for Ion mobility spectrometry measurements in a cyclical drift tube
Analytical Chemistry, 2013Co-Authors: Rebecca S Glaskin, Michael A Ewing, David E ClemmerAbstract:A new Ion Trapping technique, involving the accumulatIon of Ions in a cyclical drift tube, as a means of enhancing Ion signals for scanning Ion cyclotron mobility measurements has been modeled by computatIonal simulatIons and demonstrated experimentally. In this approach, multiple packets of Ions are periodically released from a source regIon into the on ramp regIon of the cyclical drift tube and these pulses are accumulated prior to initiatIon of the mobility measurements. Using this Ion Trapping approach, it was possible to examine Ions that traversed between 1.83 and 182.86 m (from 1 to 100 cycles). Overall, we observe that instrumental resolving power improves with increasing cycle numbers; at 100 cycles, a resolving power in excess of 1000 can be achieved. The utility of this method as a means of distinguishing between analytes is demonstrated by examining the well-characterized model peptides substance P, angiotensin II, and bradykinin.
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evidence for unfolding and refolding of gas phase cytochrome c Ions in a paul trap
Journal of the American Society for Mass Spectrometry, 2005Co-Authors: Ethan R Badman, Sunnie Myung, David E ClemmerAbstract:The folding pathways of gas-phase cytochrome c Ions produced by electrospray IonizatIon have been studied by an Ion Trapping/Ion mobility technique that allows conformatIons to be examined over extended timescales (10 ms to 10 s). The results show that the +9 charge state emerges from solutIon as a compact structure and then rapidly unfolds into several substantially more open structures, a transitIon that requires 30–60 ms; over substantially longer timescales (250 ms to 10 s) elongated states appear to refold into an array of folded structures. The new folded states are less compact than those that are apparent during the initial unfolding. Apparently, unfolding to highly open conformatIons is a key step that must occur before +9 Ions can sample more compact states that are stable at longer times.
