Antonio Ramírez

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Lithium diisopropylamide (LDA) is a prominent reagent used in organic synthesis. In this Review, rate studies of LDA-mediated reactions are placed in the broader context of organic synthesis in three distinct segments. The first section provides a tutorial on solution kinetics, emphasizing the characteristic rate behavior caused by dominant solvation and(More)
Crystalline properties of synthetic nanostructured hydroxyapatite (n-HA) were studied using high-resolution transmission electron microscopy. The focal-series-restoration technique, obtaining exit-plane wavefunction and spherical aberration-corrected images, was successfully applied for the first time in this electron-beam-susceptible material. Multislice(More)
Metal-insulator-metal (MIM) structures based on titanium dioxide have demonstrated reversible and non-volatile resistance-switching behavior and have been identified with the concept of the memristor. Microphysical studies suggest that the development of sub-oxide phases in the material drives the resistance changes. The creation of these phases, however,(More)
This work reports a detailed characterization of an anomalous oriented attachment behaviour for SnO(2) nanocrystals. Our results evidenced an anisotropic growth for two identical <110> directions, which are equivalent according to the SnO(2) crystallographic structure symmetry. A hypothesis is proposed to describe this behaviour.
In this work, we describe a kinetically controlled crystallization process assisted by an oriented attachment (OA) mechanism based on a nonaqueous sol-gel synthetic method (specifically, the reaction of titanium(IV) chloride (TiCl(4)) with n-octanol) to prepare re-crystallized anatase TiO(2) mesocrystals (single crystal). The kinetics study revealed a(More)
Modeling of nanocrystals supported by advanced morphological and chemical characterization is a unique tool for the development of reliable nanostructured devices, which depends on the ability to synthesize and characterize materials on the atomic scale. Among the most significant challenges in nanostructural characterization is the evaluation of crystal(More)
The dipeptidyl peptidase-IV inhibitor saxagliptin (Onglyza) can undergo a thermodynamically favored cyclization to form the corresponding cyclic amidine. The kinetics and mechanism of this conversion were examined to develop a commercial synthesis that afforded saxagliptin with only trace levels of this key byproduct. Important findings of this work are the(More)
This work reports the analysis of the distribution of Gd atoms and the quantification of O vacancies applied to individual CeO2 and Gd-doped CeO2 nanocrystals by electron energy-loss spectroscopy. The concentration of O vacancies measured on the undoped system (6.3±2.6 %) matches the expected value given the typical Ce(3+) content previously reported for(More)
The development of reliable nanostructured devices is intrinsically dependent on the description and manipulation of materials' properties at the atomic scale. Consequently, several technological advances are dependent on improvements in the characterization techniques and in the models used to describe the properties of nanosized materials as a function of(More)