RESUMO
Gold and silver subnanoclusters with few atoms are prominent candidates for catalysis-related applications, primarily because of the large fraction of lower-coordinated atoms exposed and ready to interact with external chemical species. However, an in-depth energetic analysis is necessary to characterize the relevant terms within the molecular adsorption process that can frame the interactions within the Sabatier principle. Herein, we investigate the interaction between Agn and Aun subnanoclusters (clu, n = 2-7) and N2 , NO, CO, and O2 molecules, using scalar-relativistic density functional theory calculations within van der Waals D3 corrections. The onefold top site is preferred for all chemisorption cases, with a predominance of linear (≈180°) and bent (≈120°) molecular geometries. A larger magnitude of adsorption energy is correlated with smaller distances between molecules and clusters and with the weakening of the adsorbates bond strength represented by the increase of the equilibrium distances and decrease of molecular stretching frequencies. From the energetic decomposition, the interaction energy term was established as an excellent descriptor to classify subnanoclusters in the adsorption/desorption process concomitant with the Sabatier principle. The limiting cases: (i) weak molecular adsorption on the subnanoclusters, which may compromise the reaction activation, where an interaction energy magnitude close to 0 eV is observed (e.g., physisorption in N2 /Ag6 ); and (ii) strong molecular interactions with the subnanoclusters, given the interaction energy magnitude is larger than at least one of the individual fragment binding energies (e.g., strong chemisorption in CO/Au4 and NO/Au4 ), conferring a decrease in the desorption rate and an increase in the possible poisoning rate. However, the intermediate cases are promising by involving interaction energy magnitudes between zero and fragment binding energies. Following the molecular closed-shell (open-shell) electronic configuration, we find a predominant electrostatic (covalent) nature of the physical interactions for N2 â¯clu and CO â¯clu (O2 â¯clu and NOâ¯clu), except in the physisorption case (N2 /Ag6 ) where dispersive interaction is dominant. Our results clarify questions about the molecular adsorption on subnanoclusters as a relevant mechanistic step present in nanocatalytic reactions.
RESUMO
Este trabalho trata a esperança como uma disposição da alma ao mesmo tempo ativa e passiva, orientada à realização de um fim e ao acolhimento de um futuro desconhecido, mas já presente enquanto potencialidade. Relaciona a esperança à posição de ativa passividade da condição de gravidez, na qual existe uma espera voltada a uma hospitalidade absoluta e, ao mesmo tempo, à posição de passiva atividade da condição intrauterina, experiência primária do infinito no finito, na qual o conteúdo transforma o continente quando somos esperados antes de saber esperar. Formas verbais latinas e hebraicas, assim como verbos e substantivos do hebraico bíblico referentes ao ato de ter esperança, vislumbram esta direção sugestiva. Por outro lado, surge a experiência de desespero em relação à condição de exílio e ao nascimento enquanto expulsão do continente uterino. Para que seja superada, exige a intervenção de um socorrista que, com a sua presença, ajuda a reorganizar a esperança e, através dela, encontrar a possibilidade de ação vital. A esperança, que sustenta a responsabilidade, leva à colaboração livre e criativa para a vida (AU)
This work treats hope as an active and at the same time passive mood of the soul, focused in accomplishing something and welcoming an unknown future, yet present as potentiality. It places hope close to the position of the active passivity in pregnancy, in which there is an expectation of absolute hospitality. At the same time, it also brings it close to the position of passive activity of the intrauterine condition, the primary experience of infinity in the finite, in which the contained transforms the container, and it is expected before having learned to expect. Latin and Hebrew verbal forms, as well as verbs and nouns of Biblical Hebrew referring to the act of hoping, seem to reveal this suggestive direction. The experience of despair is instead connected to the condition of exile, to birth as being expelled of the uterine container. To be overcome, it requires the intervention of a rescuer who helps with its presence to reorganize hope and, through it, to find the possibility of vital action. Hope, which sustains responsibility, leads to free and creative collaboration in life.
Este trabajo vincula la esperanza a un estado de ánimo activo y pasivo al mismo tiempo, dirigido a lograr un objetivo y acoger un futuro que no se conoce, pero que ya está presente como potencialidad. La acerca a la posición de pasividad activa de la condición del embarazo, en la que hay una espera orientada para la hospitalidad absoluta. Al mismo tiempo, también la acerca a la posición de actividad pasiva de la condición intrauterina, la experiencia primaria del infinito en lo finito, en la que el contenido transforma el contenedor y en la que uno espera antes de saber esperar. Formas verbales latinas y hebraicas, así como los verbos y sustantivos del hebraico bíblico que se refieren al acto de tener esperanza, parecen vislumbrar esta sugerente dirección. En cambio, la experiencia de la desesperación está relacionada con la condición del exilio, con el nacimiento como expulsión del contenedor uterino. Eso requiere, para ser superado, la intervención de un socorrista que ayude con su presencia a reorganizar la esperanza y, a través de ella, encontrar la posibilidad de una acción vital. La esperanza, que sustenta la responsabilidad, conduce a una colaboración libre y creativa en la vida.
Assuntos
Acolhimento , Afeto , Parto , EsperançaRESUMO
Here we report the use of ß-cyclodextrin polyurethane nanosponges cross-linked with 1,6-hexamethylene diisocyanate as a template for the preparation of Aun quantum clusters, by the core-etching of glutathione-capped Au nanoparticles. The study of temporal evolution of the core-etching process using different Au concentrations indicated that formation of Aun clusters embedded in the nanosponge is favored by the use of lower Au concentrations, since it began at shorter times and lead to higher cluster loading. An estimation of the number of Au atoms based on the maximum photoluminescence wavelength suggested that, depending on the Au concentration and the core etching time, clusters with 11-15 atoms were formed. After excluding the possibility of an inclusion complex formation, evaluation of the catalytic activity of nanosponge-loaded Aun clusters toward the reduction of 4-nitrophenol has shown that the reaction is catalyzed by the Aun clusters with no induction time, following the Langmuir-Hinshelwood kinetic model.