Papers by Douglas S. Galvao
Understanding nanomechanical response of materials represents a scientific challenge. Here, we ha... more Understanding nanomechanical response of materials represents a scientific challenge. Here, we have used in-situ electron microscopy to reveal drastic for the first time changes of structural behavior during deformation of 1-nm-wide metal rods as a function of temperature. At 300 K, stretched nanowires stay defect-free, while at 150 K, elongation is associated with planar defects.
ChemInform, 1992
ABSTRACT Ellipticine and its derivatives are molecules that show antitumour and cytotoxic activit... more ABSTRACT Ellipticine and its derivatives are molecules that show antitumour and cytotoxic activity, with a multimodal mechanism of action. In this paper we report a spectroscopic intermediate neglect of differential overlap with configuration interaction study of ellipticine and some of its derivatives, in the neutral and charged states. A mechanism that could improve the antitumoural and cytotoxic activity of these compounds is proposed.
Journal of Applied Physics, 2015
We report here an atomistic study of the mechanical deformation of Au x Cu (1−x) atomic-size wire... more We report here an atomistic study of the mechanical deformation of Au x Cu (1−x) atomic-size wires (NWs) by means of high resolution transmission electron microscopy (HRTEM) experiments.
MRS Proceedings, 2013
ABSTRACT Graphyne is a generic name for a family of carbon allotrope two-dimensional structures w... more ABSTRACT Graphyne is a generic name for a family of carbon allotrope two-dimensional structures where sp2 (single and double bonds) and sp (triple bonds) hybridized states coexists. They exhibit very interesting electronic and mechanical properties sharing some of the unique graphene characteristics. Similarly to graphene, the graphyne electronic properties can be modified by chemical functionalization, such as; hydrogenation, fluorination and oxidation. Oxidation is of particular interest since it can produce significant structural damages.In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered α, β, and γ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering. These differences can be explained by the fact that for α-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of γ-graphyne structures prevent these reactions to occur. The effectiveness of β-graphyne oxidation is between the α- and γ-graphynes.
Journal of Molecular Structure: THEOCHEM, 2000
Recently we have shown that it is possible to group and identify the carcinogenic activity of the... more Recently we have shown that it is possible to group and identify the carcinogenic activity of the polycyclic aromatic hydrocarbons (PAHs) using very simple rules derived from simple Hu Èckel calculations. In this work we have carried out similar calculations using semi-empirical methods in order to investigate whether the derived rules are method dependent. We present PM3 (Parametric Method 3) and ZINDO-CI (Zerner Intermediate Neglect of Differential Overlap-Con®guration Interaction) study on the electronic structure of PAHs. Very similar rules, based on the concept of electronic local density of states over speci®c molecular regions, are derived from PM3 calculations showing that they are essentially method independent. The analysis of the ZINDO-CI results for the intensity of the threshold transitions (®rst optical transitions) and the composition of the CI contributions also show a differentiated behavior for the strong carcinogenic molecules and the inactive ones. q
Advanced materials (Deerfield Beach, Fla.), Jan 14, 2015
The morphology of graphene-based foams can be engineered by reinforcing them with nanocrystalline... more The morphology of graphene-based foams can be engineered by reinforcing them with nanocrystalline zirconia, thus improving their oil adsorption capacity; This can be observed experimentally and explained theoretically. Low zirconia fractions yield flaky microstructures where zirconia nanoparticles arrest propagating cracks. Higher zirconia concentrations possess a mesh-like interconnected structure where the degree of coiling is dependant on the local zirconia content.
Advanced Materials, 2015
Here the direct synthesis of monolayer and multilayer ReS2 by chemical vapor deposition at a low ... more Here the direct synthesis of monolayer and multilayer ReS2 by chemical vapor deposition at a low temperature of 450 °C is reported. Detailed characterization of this material is performed using various spectroscopy and microscopy methods. Furthermore initial field effect transistor characteristics are evaluated which highlight the potential in being used as an n-type semiconductor.
Materials Research
In the last years the possibility of creating new conducting polymers exploring the concept of co... more In the last years the possibility of creating new conducting polymers exploring the concept of copolymerization (different structural monomeric units) has attracted much attention from experimental and theoretical points of view. Due to the rich carbon reactivity an almost infinite number of new structures is possible and the procedure of trial and error has been the rule. In this work we have used a methodology able of generating new structures with pre-specified properties. It combines the use of negative factor counting (NFC) technique with artificial intelligence methods (genetic algorithms - GAs). We present the results for a case study for poly(phenylenesulfide phenyleneamine) (PPSA), a copolymer formed by combination of homopolymers: polyaniline (PANI) and polyphenylenesulfide (PPS). The methodology was successfully applied to the problem of obtaining binary up to quinternary disordered polymeric alloys with a pre-specific gap value or exhibiting metallic properties. It is co...
Nano Letters
Carbon nanotube scrolls (CNSs) provide an interesting form of carbon that ideally consists of a s... more Carbon nanotube scrolls (CNSs) provide an interesting form of carbon that ideally consists of a single sheet of graphite that is spiral wrapped to form a nanotube. We here use molecular dynamics simulations to investigate CNS formation, stability, and the structural effects due to charge injection. CNS formation is seen to automatically occur when a critical overlap between sheet layers is achieved for the partially curled sheet. We find that charge injection causes unwinding of the CNSs, which might be important for the application of CNSs as nanomechanical actuators.
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Papers by Douglas S. Galvao