Intoxication au monoxyde de carbone

Résumé

Lintoxication au monoxyde de carbone se produit après l'inhalation d'un gaz, le monoxyde de carbone. Le monoxyde de carbone (CO) est un produit de la combustion des matières organiques dans des conditions d'apport insuffisant en oxygène, qui empêche l'oxydation complète en dioxyde de carbone (). Le monoxyde de carbone est incolore, inodore, insipide et non irritant, ce qui le rend difficile à détecter pour les personnes exposées. Le monoxyde de carbone est un gaz particulièrement toxique, et l'intoxication au CO est la cause la plus répandue d'empoisonnement mortel dans de nombreux pays. Les symptômes de l'intoxication légère associent des maux de tête, des vertiges, et des manifestations pseudo-grippales ; une exposition plus forte peut entraîner des effets toxiques sur le système nerveux central, le cœur et même provoquer la mort. À la suite de l'intoxication, il persiste souvent des séquelles à long terme. Le monoxyde de carbone peut aussi avoir de graves effets sur le fœtus d'une femme enceinte. Le monoxyde de carbone provoque l'intoxication en se fixant sur les globules rouges (via la respiration et les poumons) et en empêchant ces globules de véhiculer correctement l'oxygène dans l'organisme. Les mécanismes par lesquels le monoxyde de carbone induit ces effets toxiques ne sont pas encore entièrement connus, mais on pense que l’hémoglobine, la myoglobine et la cytochrome oxydase mitochondriale sont impliquées. Le traitement consiste essentiellement à administrer de l’oxygène à 100 % ou encore à utiliser l’oxygénothérapie hyperbare, bien qu’il existe encore une controverse sur le point de savoir lequel de ces deux traitements est le meilleur. Les intoxications domestiques au monoxyde de carbone peuvent être évitées par une détection précoce par utilisation d’un détecteur de monoxyde de carbone ménager. Le monoxyde de carbone est un produit de la combustion incomplète des hydrocarbures. La concentration atmosphérique du monoxyde de carbone est habituellement inférieure à 0,001 %.

Source officielle

https://fr.wikipedia.org/wiki/Intoxication_au_monoxyde_de_carbone

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Grafting of Alkali Metals on Fumed Silica for the Catalytic Dehydrogenation of Methanol to Formaldehyde

Alimohammad Bahmanpour, Christophe Jean Baranowski, Jack Brandon

Water free, non-oxidative catalytic dehydrogenation of methanol to formaldehyde is an important process for the formation of anhydrous, molecular formaldehyde (FA). Sodium or sodium-containing salts were shown to catalyze the reaction, but their reaction mechanism remains unclear. In this work, we thus investigated the performance of a series of catalysts prepared by grafting of alkali metals on amorphous silica for methanol catalytic dehydrogenation. The resulting catalysts displayed an increased activity for the catalytic dehydrogenation of methanol. Variation of the electron density of the supported alkali metal cations severely affected the FA selectivity, which followed the trend: Li>Na>K>Rb>Cs. A large gap in selectivity towards FA between ions with a high (i. e., Li, Na) and low charge density (i. e., K, Rb, Cs) was observed. Also, increased metal loading adversely affected FA selectivity and resulted in a larger production of carbon monoxide. Sodium grafted on silica yielded the best combination of moderate conversion and high selectivity.

2021

We report the light-induced modification of catalytic selectivity for photoelectrochemical CO2 reduction in aqueous media using copper (Cu) nanoparticles dispersed onto p-type nickel oxide (p-NiO) photocathodes. Optical excitation of Cu nanoparticles generates hot electrons available for driving CO2 reduction on the Cu surface, while charge separation is accomplished by hot-hole injection from the Cu nanoparticles into the underlying p-NiO support. Photoelectrochemical studies demonstrate that optical excitation of plasmonic Cu/p-NiO photocathodes imparts increased selectivity for CO2 reduction over hydrogen evolution in aqueous electrolytes. Specifically, we observed that plasmon-driven CO2 reduction increased the production of carbon monoxide and formate, while simultaneously reducing the evolution of hydrogen. Our results demonstrate an optical route toward steering the selectivity of artificial photosynthetic systems with plasmon-driven photocathodes for photoelectrochemical CO2 reduction in aqueous media.

2020

Many diseases including sick building syndrome, respiratory problems and cancers can be caused by exposure to high concentrations of toxins commonly used in modern building materials, paints, glues and furniture. To minimize exposure to these toxins, it is important to have air exchange with the outside environment. However, this is usually not energy efficient because the air must be heated or cooled. The purpose of the Intasense project was to resolve this problem by creating an air quality monitor which could determine the current quality of air within the building. This information would then be used to control the ventilation system within an energy efficient building. The purpose of this Ph.D. thesis was both to build a system which could be used to test and calibrate sensors used in the air quality monitor as well as to build its final fluidic platform. During this thesis, three fluidic platforms which include a humidity buffering system were designed, tested and constructed. The first platform was used to test an electrochemical sensor or metal oxide sensor in the laboratory. The second and third platforms held three electrochemical or metal oxide sensors, respectively. They are able to deliver equal quantities of gas to the sensors simultaneously. To date, the multisensor metal oxide platform has been used to create two versions of the Intasense Demonstrator and used to calibrate novel and commercial gas sensors. In both of these applications simultaneous delivery of equal quantities of the sample gas are required for optimal gas sensor signal processing: equal quantities are required so that the amount of analyte in contact with each sensor is the same and simultaneous delivery allows all three sensors to respond concurrently. This was achieved by creating a computational model of gas flow through the system, conducting a parameter sweep and then selecting the optimal set. To confirm that the model and machine error were not significant, a Latin square design was used to test the platform. This test showed that gas delivery to each channel was equal within statistical boundaries. Another major challenge was buffering humidity fluctuations without loss of analyte gas. This was necessary because metal oxide gas sensors are also sensitive to humidity fluctuations. To prevent a false positive caused by a rapid humidity increase, a reversible adsorbent was placed upstream of the gas sensors. However, there was concern that the adsorbent may remove analyte gasses. To optimize the tradeoff between humidity buffering and loss or delay of analyte signal, a computational model of adsorption and desorption of gasses within the filtration system was developed. It was experimentally tested using benzene, carbon monoxide, formaldehyde and nitrogen dioxide. To date ten platforms have been delivered to laboratories throughout Europe. Three are being used to test and calibrate gas sensors. The rest have been used to create demonstrators of the Intasense Air Quality Monitor.

EPFL2016