283 research outputs found
Insights from a Theoretical Approach on the Weak Intermolecular Forces: the Transition from Van Der Waals to Chemical Bond
No full textBickelhaupt, F.M. [Promotor]Tarantelli, F. [Promotor]Fonseca Guerra, C. [Copromotor]Nunzi, F. [Copromotor
Nanotubes and Peapods
No full textThe author report an updated review of the recent progress in the characterization of inorganic nanotubes and in the chemistry of tubular structures carried out by theoretical investigations, based on DFT methods, with particular emphasis devoted to the description of the novel hybrid nanopeapod structures
DFT Investigations of Formic Acid Adsorption on Single-Wall TiO<sub>2</sub> Nanotubes: Effect of the Surface Curvature
No full textWe carried out a theoretical study based on DFT calculations to provide a detailed characterization of the structural, electronic, and adsorption properties of single-walled TiO2 anatase nanotubes. We nanotube models of increasing diameter, formally obtained by rolling a TiO2 anatase monolayer around the [(1) over bar 01] and [010] directions, giving rise to (n,0) and (0,m) nanotubes, respectively. We considered finite cluster models for both (n,0) and (m,0) TiO2 nanotubes, with diameters ranging from 5 to 30 angstrom, thus' approaching realistic nanotube dimensions. Our results show that (n,0) tubes are lower in energy with respect to (0,m) tubes. For (n,0) tubes with diameters greater than 23 angstrom, the electronic energy and the band gap are almost converged with respect to the diameter length. We then investigated the adsorption of formic acid on the TiO2 nanotube sidewalls, as the simplest model of photosensitizers binding to the TiO2 surface, relevant to dye-sensitized solar cells. Adsorption of formic acid was investigated on (12,0) and (0,4) TiO2 nanotubes, optimizing two monodentate modes and one bidentate adsorption mode, and comparing the results to those obtained for a planar TiO2 surface. We find that while for a planar surface a bridged bidentate configuration is the more stable, the effect of the curvature in TiO2 nanotubes leads a monodentate configuration to be the more stable structure. These results are interpreted in terms of the peculiar electronic properties of TiO2 nanotubes and their implications for use of nanotubes in dye-sensitized solar cells are discussed
Charge Displacement Analysis-A Tool to Theoretically Characterize the Charge Transfer Contribution of Halogen Bonds
No full textTheoretical bonding analysis is of prime importance for the deep understanding of the various chemical interactions, covalent or not. Among the various methods that have been developed in the last decades, the analysis of the Charge Displacement function (CD) demonstrated to be useful to reveal the charge transfer effects in many contexts, from weak hydrogen bonds, to the characterization of σ hole interactions, as halogen, chalcogen and pnictogen bonding or even in the decomposition of the metal-ligand bond. Quite often, the CD analysis has also been coupled with experimental techniques, in order to give a complete description of the system under study. In this review, we focus on the use of CD analysis on halogen bonded systems, describing the most relevant literature examples about gas phase and condensed phase systems. Chemical insights will be drawn about the nature of halogen bond, its cooperativity and its influence on metal-ligand bond components
A density functional study of the dissociative adsorption of aromatic molecules on the Si(100) surface: on the way from benzene to larger polycyclic hydrocarbons
No full textDermatobia hominis infestation
No full textA patient is reported who, after leaving Venezuela, developed some boils on the left upper limb inhabited by Dermatobia hominis larvae. The curious life-cycle of this tropical fly is described with some considerations about the diagnostic problem. A simple unreported way of larvae extraction is suggested
Complexes of helium with neutral molecules: Progress toward a quantitative scale of bonding character
No full textThe complexes of helium with nearly 30 neutral molecules (M) were investigated by various techniques of bonding analysis and symmetry-adapted perturbation theory (SAPT). The main investigated function was the local electron energy density H(r), analyzed, in particular, so to estimate the degree of polarization (DoP) of He in the various He(M). As we showed recently (Borocci et al., J. Comput. Chem., 2019, 40, 2318–2328), the DoP is a quantitative index that is generally informative about the role of polarization (induction plus charge transfer [CT]) and dispersion in noncovalent noble gas complexes. As further evidence in this regard, we presently ascertained quantitative correlations between the DoP(He) of the He(M) and indices based on the electron density ρ(r), including the molecular electrostatic potential at the HeM bond critical point, as well as the percentage contributions of induction and dispersion to the SAPT binding energies. Based also on the explicit evaluation of the CT, accomplished through the study of the charge-displacement function, we derived a quantitative scale that ranks the He(M) according to their dispersive, inductive, and CT bonding character. Our taken approach could be conceivably extended to other types of noncovalent complexes
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