Ligand conversion in nanocrystal synthesis: the oxidation of alkylamines to fatty acids by nitrate

Ligands are a fundamental part of nanocrystals. They control and direct nanocrystal syntheses and provide colloidal stability. Bound ligands also affect the nanocrystals’ chemical reactivity and electronic structure. Surface chemistry is thus crucial to understand nanocrystal properties and functionality. Here, we investigate the synthesis of metal oxide nanocrystals (CeO2-x, ZnO, and NiO) from metal nitrate precursors, in the presence of oleylamine ligands. Surprisingly, the nanocrystals are capped exclusively with a fatty acid instead of oleylamine. Analysis of the reaction mixtures with nuclear magnetic resonance spectroscopy revealed several reaction byproducts and intermediates that are common to the decomposition of Ce, Zn, Ni, and Zr nitrate precursors. Our evidence supports the oxidation of alkylamine and formation of a carboxylic acid, thus unraveling this counterintuitive surface chemistry.Postprint (published version

Assessment of static nonlinear approaches for earthquake-resistant design of tall reinforced concrete buildings

The simplified nonlinear static procedures (conventional pushover) have become a useful tool to assess the seismic performance of buildings. Beyond their inherent static character, such methods include two major inaccuracies: poor consideration of the higher-mode effects and lack of consideration of the changes in the modal characteristics of the structure (mainly, the modal shapes) as the damage progresses; both issues are particularly relevant for tall buildings. To cope with these two subjects, the modal and adaptive pushover strategies have been proposed, respectively. The objective of this paper is to evaluate the suitability of these procedures for high-rise buildings. The research approach consists in selecting two representative prototype buildings with 30 and 45 stories and carrying out a number of nonlinear static and dynamic analyses and comparing their results. Preliminary results show that current pushover methods cannot predict with enough accuracy the response of high-rise buildings under dynamic seismic action.Postprint (published version

Assessment of static nonlinear approaches for earthquake-resistant design of tall reinforced concrete buildings

The simplified nonlinear static procedures (conventional pushover) have become a useful tool to assess the seismic performance of buildings. Beyond their inherent static character, such methods include two major inaccuracies: poor consideration of the higher-mode effects and lack of consideration of the changes in the modal characteristics of the structure (mainly, the modal shapes) as the damage progresses; both issues are particularly relevant for tall buildings. To cope with these two subjects, the modal and adaptive pushover strategies have been proposed, respectively. The objective of this paper is to evaluate the suitability of these procedures for high-rise buildings. The research approach consists in selecting two representative prototype buildings with 30 and 45 stories and carrying out a number of nonlinear static and dynamic analyses and comparing their results. Preliminary results show that current pushover methods cannot predict with enough accuracy the response of high-rise buildings under dynamic seismic action