Structure and Reactivity of Alkyl Ethers Adsorbed on CeO2(111) Model Catalysts

The effect of surface hydroxyls on the adsorption of ether on ceria was explored. Adsorption of dimethyl ether (DME) and diethyl ether (DEE) on oxidized and reduced CeO₂(111) films was studied and compared with Ru(0001) using RAIRS and sXPS within a UHV environment. On Ru(0001) the ethers adsorb weakly with the molecular plane close to parallel to the surface plane. On the ceria films, the adsorption of the ethers was stronger than on the metal surface, presumably due to stronger interaction of the ether oxygen lone pair electrons with a cerium cation. This interaction causes the ethers to tilt away from the surface plane compared to the Ru(0001) surface. No pronounced differences were found between oxidized (CeO₂) and reduced (CeOx) films. The adsorption of the ethers was found to be perturbed by the presence of OH groups on hydroxylated CeOx. In the case of DEE, the geometry of adsorption resembles that found on Ru, and in the case of dimethyl ether DME is in between that one found on clean CeOx and the metal surface. Decomposition of the DEE was observed on the OH/CeOx surface following high DEE exposure at 300 K and higher temperatures. Ethoxides and acetates were identified as adsorbed species on the surface by means of RAIRS and ethoxides and formates by s-XPS. No decomposition of dimethyl ether was observed on the OH/CeOx at these higher temperatures, implying that the dissociation of the C?CO bond from ethers requires the presence of ??-hydrogen.     

New approach for batch microfabrication of silicon-based micro fuel cells

This paper reports a novel and straightforward approach to the development of a compact micro direct methanol fuel cell. The device consists of a hybrid polymer membrane as a feasible microintegrable electrolyte to be used together with silicon current collectors. These current collectors consist in microfabricated silicon chips that incorporate a fine electrode grid. The membrane combines two polymers with different functionalities, Nafion^® as a proton conducting material and PDMS as a flexible mechanical support. The compatibility of this membrane with MEMS fabrication processes lies in the acknowledged bonding capabilities of the PDMS polymer to materials typically used in microsystems technologies—such as silicon, silicon dioxide and glass—as well as its ability to withstand variations of the Nafion^® volume. The compatibility of all the components with microfabrication processes will permit the application of batch fabrication techniques for the whole device, so contributing to a significant lowering of the fabrication costs.     

6th San Luis Conference on Surfaces,Interfaces and Catalysis

Topics in Catalysis -     

Retinal Toxicity Induced by Chemical Agents

Vision is an important sense for humans, and visual impairment/blindness has a huge impact in daily life. The retina is a nervous tissue that is essential for visual processing since it possesses light sensors (photoreceptors) and performs a pre-processing of visual information. Thus, retinal cell dysfunction or degeneration affects visual ability and several general aspects of the day-to-day of a person’s lives. The retina has a blood–retinal barrier, which protects the tissue from a wide range of molecules or microorganisms. However, several agents, coming from systemic pathways, reach the retina and influence its function and survival. Pesticides are still used worldwide for agriculture, contaminating food with substances that could reach the retina. Natural products have also been used for therapeutic purposes and are another group of substances that can get to the retina. Finally, a wide number of medicines administered for different diseases can also affect the retina. The present review aimed to gather recent information about the hazard of these products to the retina, which could be used to encourage the search for more healthy, suitable, or less risky agents.