Why surface hydrophobicity promotes CO2 electroreduction: a case study of hydrophobic polymer N-heterocyclic carbenes

We report the use of polymer N-heterocyclic carbenes (NHCs) to control the microenvironment surrounding metal nanocatalysts, thereby enhancing their catalytic performance in CO2 electroreduction. Three polymer NHC ligands were designed with different hydrophobicity: hydrophilic poly(ethylene oxide) (PEO–NHC), hydrophobic polystyrene (PS–NHC), and amphiphilic block copolymer (BCP) (PEO-b-PS–NHC). All three polymer NHCs exhibited enhanced reactivity of gold nanoparticles (AuNPs) during CO2 electroreduction by suppressing proton reduction. Notably, the incorporation of hydrophobic PS segments in both PS–NHC and PEO-b-PS–NHC led to a twofold increase in the partial current density for CO formation, as compared to the hydrophilic PEO–NHC. While polymer ligands did not hinder ion diffusion, their hydrophobicity altered the localized hydrogen bonding structures of water. This was confirmed experimentally and theoretically through attenuated total reflectance surface-enhanced infrared absorption spectroscopy and molecular dynamics simulation, demonstrating improved CO2 diffusion and subsequent reduction in the presence of hydrophobic polymers. Furthermore, NHCs exhibited reasonable stability under reductive conditions, preserving the structural integrity of AuNPs, unlike thiol-ended polymers. The combination of NHC binding motifs with hydrophobic polymers provides valuable insights into controlling the microenvironment of metal nanocatalysts, offering a bioinspired strategy for the design of artificial metalloenzymes

Informe de sostenibilidad a la escuela de estudios superiores de policía

Tablas, graficasEste informe evalúa algunos de los indicadores GRI aplicados por La Policía Nacional, se pretende enfatizar en los que en la actualidad existen falencias operativas ó administrativas con relación a los StakesHolders Externos. Cabe resaltar que la Institución para el año 2009 esta en el ciclo de Mantenimiento de un proyecto de Fortalecimiento del Sistema de Gestión Integral, que fue implementado desde el año 2008. La información recopilada en este trabajo se obtuvo de fuentes confiables de la Policía Nacional y a través de la Dirección Nacional; sumado a esto pretendemos socializar la información obtenida para dar a conocer que Indicadores merecen reevaluarse por parte de la Institución, toda vez que el Sistema de Gestión Integral que el ente viene trabajando para el presente año en el proceso de mantenimiento debe conseguir la obligatoriedad de dar cumplimiento a las reformas transversales del estado.No Abstrac

Smelling Sulfur: Copper and Silver Regulate the Response of Human Odorant Receptor OR2T11 to Low-Molecular-Weight Thiols

Mammalian survival depends on ultrasensitive olfactory detection of volatile sulfur compounds, since these compounds can signal the presence of rancid food, O₂ depleted atmospheres, and predators (through carnivore excretions). Skunks exploit this sensitivity with their noxious spray. In commerce, natural and liquefied gases are odorized with <i>t</i>-BuSH and EtSH, respectively, as warnings. The 100-million-fold difference in olfactory perception between structurally similar EtSH and EtOH has long puzzled those studying olfaction. Mammals detect thiols and other odorants using odorant receptors (ORs), members of the family of seven transmembrane G-protein-coupled receptors (GPCRs). Understanding the regulator cofactors and response of ORs is particularly challenging due to the lack of X-ray structural models. Here, we combine computational modeling and site-directed mutagenesis with saturation transfer difference (STD) NMR spectroscopy and measurements of the receptor response profiles. We find that human thiol receptor OR2T11 responds specifically to gas odorants <i>t</i>-BuSH and EtSH requiring ionic copper for its robust activation and that this role of copper is mimicked by ionic and nanoparticulate silver. While copper is both an essential nutrient for life and, in excess, a hallmark of various pathologies and neurodegenerative diseases, its involvement in human olfaction has not been previously demonstrated. When screened against a series of alcohols, thiols, sulfides, and metal-coordinating ligands, OR2T11 responds with enhancement by copper to the mouse semiochemical CH₃SCH₂SH and derivatives, to four-membered cyclic sulfide thietane and to one- to four-carbon straight- and branched-chain and five-carbon branched-chain thiols but not to longer chain thiols, suggesting compact receptor dimensions. Alcohols are unreactive