Grafting of Quinones on Carbons as Active Electrode Materials in Electrochemical Capacitors

The electrochemical performance of electrochemical capacitors can be improved with electroactive quinone molecules. Systems based on redox active electrolyte as well as physisorbed and chemically grafted molecules have been investigated. In all these cases, carbon materials were used as substrate and electrode material. This short review will mainly describe work related to these systems and materials from the authors’ laboratories. Nonetheless, some important studies from other research groups will be discussed

Conception et caractérisation d’une batterie organique obtenue par greffage direct de molécules électroactives sur carbone activé

Date du colloque : 07/2013</p

Effect of the porous texture of activated carbons on the electrochemical properties of molecule-grafted carbon products in organic media

Two commercial activated carbons, different from their texture, were grafted with electroactive molecules and tested for determining what texture is well-suited for the grafting. Microporous and mesoporous carbons, having approximately the same BET surface area, were selected. The electroactive molecule consists in a naphthalimide compound having an amine as surface attachment group. The present work was divided in two parts. In a first part, the modified carbons were characterized by thermal gravimetric analysis, X-ray photoelectron spectroscopy, elemental chemical analysis and nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the textural properties of carbons. In a second part, the electrochemical properties of the modified carbons were studied in propylene carbonate +1 M Bu4NBF4. Results show that the grafting ruins the performances of the microporous carbon, while the mesoporous carbon appears well-suited for the grafting, showing a good compromise between electrolyte-accessibility and ionic transportation

Nouvelles stratégies de production in situ de sels de diazonium pour la modification éléctrochimique de surfaces

Date du colloque : 07/2011</p

Toward fully organic rechargeable charge storage devices based on carbon electrodes grafted with redox molecules

Activated carbon powders modified with naphthalimide and 2,2,6,6-tetramethylpiperidine-N-oxyl were assembled into a hybrid electrochemical capacitor containing an organic electrolyte. The fully organic rechargeable system demonstrated an increase in specific capacitance up to 51%, an extended operating voltage of 2.9 V in propylene carbonate, compared to 1.9 V for the unmodified system, and a power 2.5 times higher

Strong spin-photon coupling in silicon

We report the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. This result opens the way to the realization of large networks of quantum dot based spin qubit registers, removing a major roadblock to scalable quantum computing with spin qubits

Direct introduction of redox centers at activated carbon substrate based on acid-substituent-assisted diazotization

Redox properties have been imparted to activated carbon with a high degree of functionalization by chemical grafting of 2-amino-4,5-dimethoxybenzoic add in situ diazotized. The diazotization reaction was accomplished in the presence or in the absence of HCl for estimating the positive or negative effect of the carboxylic acid substituent on the grafting yield. Thermal gravimetric analysis, X-ray photoelectron spectroscopy and cyclic voltammetry experiments show that when the carboxylic acid group participates to the diazotization reaction. the grafting yield is improved and becomes even better than when the carboxylic group is not present, increasing the capacitance of pristine carbon electrode from 120 to 200 F/g

ifCNV: A novel isolation-forest-based package to detect copy-number variations from various targeted NGS datasets

Copy-number variations (CNVs) are an essential component of genetic variation distributed across large parts of the human genome. CNV detection from next-generation sequencing data and artificial intelligence algorithms have progressed in recent years. However, only a few tools have taken advantage of machine-learning algorithms for CNV detection, and none propose using artificial intelligence to automatically detect probable CNV-positive samples. The most developed approach is to use a reference or normal dataset to compare with the samples of interest, and it is well known that selecting appropriate normal samples represents a challenging task that dramatically influences the precision of results in all CNV-detecting tools. With careful consideration of these issues, we propose here ifCNV, a new software based on isolation forests that creates its own reference, available in R and python with customizable parameters. ifCNV combines artificial intelligence using two isolation forests and a comprehensive scoring method to faithfully detect CNVs among various samples. It was validated using targeted next-generation sequencing (NGS) datasets from diverse origins (capture and amplicon, germline and somatic), and it exhibits high sensitivity, specificity, and accuracy. ifCNV is a publicly available open-source software (https://github.com/SimCab-CHU/ifCNV) that allows the detection of CNVs in many clinical situations

Covalent vs. non-covalent redox functionalization of C-LiFePO4 based electrodes

During high rate utilization of porous Li battery, Li+ refuelling from the electrolyte limits the discharge kinetics of positive electrodes. In the case of thick electrodes a strategy to buffer the resulting sharp drop of Li+ concentration gradient would be to functionalize the electrode with anionic based redox molecules (RMR) that would be therefore able to relay intercalation process. The occurrence of these RMR in the electrode should not however, induce adverse effect on Li intercalation processes. In this respect, this work studies the effect of functionalizing LFPC based electrodes by either covalent or non-covalent chemistry, on Li intercalation kinetics. To do so, model molecules containing a nitro group were introduced at the surface of both carbon conducting additives and active material (C-LiFePO4). It is shown that presumably due to formation of sp(3) defects, covalent anchoring using diazonium chemistry inhibits the intercalation kinetics in C-FePO4. On the contrary, if molecules such as pyrene derivatives are immobilized by pi-staking interactions, Li intercalation is not impeded. Therefore non-covalent functionalization of pyrene based RMR appears as a promising route to relay Li intercalation reaction during high power demand. The framework for future development of this strategy is discussed. (C) 2013 Elsevier B.V. All rights reserved

High-resolution regional modeling of urban moisture island: mechanisms and implications on thermal comfort

The urban moisture island (UMI) can aggravate the thermal stress due to the urban heat island (UHI) in subtropical and tropical cities. In this study, we investigated the spatiotemporal variation patterns of UMI in Hong Kong, a subtropical coastal city, using the fine-resolution mesoscale Weather Research and Forecasting (WRF) model by integrating local climate zone (LCZ) maps based on the World Urban Database and Access Portal Tools (WUDAPT). Our results show that at regional scale, the UMI phenomenon tends to occur in coastal areas, possibly owing to rich moisture sources from sea breeze and inhibited moisture penetration due to barrier effects of mountains. Specifically, an all-day UMI effect was found in coastal low-density low-rise areas (LCZ5&8&10), while a nocturnal UMI effect and a daytime urban dry island (UDI) effect were found in coastal high-density high-rise areas (LCZ1&2). The UDI effect at daytime can be attributed to strong vertical moisture convection associated with intensive surface sensible heat fluxes in a strongly mixed urban boundary layer (UBL). The UMI effect at night can be attributed to blocked ventilation aisle, inhibited dewfall due to UHI, and weakened upward motion in a stable UBL. On the other hand, UMI can increase regional heat risks with additional 37.5% neighbourhoods in Extreme caution level and additional 6.1% neighbourhoods in Danger level. In addition, the impact of UMI on human thermal stress was found to be dominant at daytime in coastal low-density low-rise areas (LCZ5&8&10) and at nighttime in coastal high-density high-rise areas (LCZ1&2)