Julieta I. Paez

Preparation of controlled gold nanoparticle aggregates using a dendronization strategy

In this work, a dendronization strategy was used to control interparticle spacing and the optical properties of gold nanoparticle (NP) aggregates in aqueous media. To achieve this goal, two dendritic disulfides bearing different functionalities on their periphery were synthesized and used as ligands to dendronize gold NPs. The dendronized NPs then undergo aggregation; this process was followed by UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electronic microscopy (TEM) measurements and correlated with Generalized Mie Theory electrodynamics calculations. For comparison, NP functionalization was also studied using a nondendritic ligand. It was found that the use of dendritic disulfides allows for the preparation of controlled NP aggregates. This study demonstrates how different dendronization parameters, such as disulfide concentration, temperature, time and nature of the ligand (dendritic vs nondendritic), determine the control exerted over the size and stability of the NP aggregates.

Work Function Maps and Surface Topography Characterization of Nitroaromatic-Ended Dendron Films on Graphite

Surface topography and work function maps were simultaneously obtained for carbon surfaces modified by a dendritic molecule: 3,5-Bis (3,5-dinitrobenzoylamino) benzoic acid. The dendrons were spontaneously assembled onto highly ordered pyrolytic graphite samples, exhibiting an increase in the surface potential. This fact is consistent with the incorporation of an electron-acceptor functional group that remains electroactive on the surface.

Effect of the molecular structure on the reactivity in a family of tetra-amine compounds derived from Jeffamines

AbstractThe effect of the molecular structure on the reactivity of four first-generation linear-dendritic block copolymers derived from Jeffamines and bearing amine end groups is presented and discussed. Different parameters were investigated via chemical modifications and nuclear magnetic resonance analysis, showing that chain length, hydrophilic/hydrophobic character, and flexibility of the central oligoether block did not produce any change in the amine moiety reactivity. In contrast, the type of branches and the nature of the amine end groups strongly affected the reactivity in an unusual manner. In fact, the copolymer bearing aromatic amine end groups showed better reactivity than those based on aliphatic counterparts.