Andrea Cadeddu - Academia.edu (original) (raw)

Papers by Andrea Cadeddu

Small (Weinheim an der Bergstrasse, Germany), Jan 24, 2015

A joint experimental and computational study is reported on the concentration-dependant self-asse... more A joint experimental and computational study is reported on the concentration-dependant self-assembly of a flat C3 -symmetric molecule on a graphite surface. As a model system a tripodal molecule, 1,3,5-tris(pyridin-3-ylethynyl)benzene, has been chosen, which can adopt either C3h or Cs symmetry when planar, as a result of pyridyl rotation along the alkynyl spacers. Density functional theory (DFT) simulations of 2D nanopatterns with different surface coverage reveal that the molecule can generate different types of self-assembled motifs. The stability of fourteen 2D patterns and the influence of concentration are analyzed. It is found that ordered, densely packed monolayers and 2D porous networks are obtained at high and low concentrations, respectively. A concentration-dependent scanning tunneling microscopy (STM) investigation of this molecular self-assembly system at a solution/graphite interface reveals four supramolecular motifs, which are in perfect agreement with those predict...

Advances in Intelligent Systems and Computing, 2015

ABSTRACT

Angewandte Chemie, 2014

Methods of computational linguistics are used to demonstrate that a natural language such as Engl... more Methods of computational linguistics are used to demonstrate that a natural language such as English and organic chemistry have the same structure in terms of the frequency of, respectively, text fragments and molecular fragments. This quantitative correspondence suggests that it is possible to extend the methods of computational corpus linguistics to the analysis of organic molecules. It is shown that within organic molecules bonds that have highest information content are the ones that 1) define repeat/symmetry subunits and 2) in asymmetric molecules, define the loci of potential retrosynthetic disconnections. Linguistics-based analysis appears well-suited to the analysis of complex structural and reactivity patterns within organic molecules.

2014 23rd International Conference on Robotics in Alpe-Adria-Danube Region (RAAD), 2014

The home automation system to control the climatic health in confined environments is the subject... more The home automation system to control the climatic health in confined environments is the subject of this article. The standard UNI EN ISO 7730:2006 classifies the conditions of moderate confined environments by three categories according to the PMV index. The comfort sensation is mainly affected by four variables: air temperature, mean radiant temperature, air velocity, relative humidity. They are all mechanical and thermal quantities therefore they are measured through the same measurement method. In evaluating the PMV index two more variables are taken into account: metabolism and clothing insulation. They can be evaluated by different accuracy levels. Their indirect measure is subjected to more uncertainty than the above four measuring parameters and the distribution is typically non-Gaussian. The paper analyses the uncertainty in PMV measuring through the Monte Carlo simulation. The proposed study identifies the different weight of independent variables showing as their uncertainty, particularly those referred to metabolism and clothing insulation, affects considerably the final values for classifying the moderate environments.

Journal of the American Chemical Society, 2013

We report a joint computational and experimental study on the concentration-dependent self-assemb... more We report a joint computational and experimental study on the concentration-dependent self-assembly of a flat C3-symmetric molecule at surfaces. As a model system we have chosen a rigid molecular module, 1,3,5-tris(pyridine-4-ylethynyl)benzene, which can undergo self-association via hydrogen bonding (H-bonding) to form ordered 2D nanostructures. In particular, the lattice Monte Carlo method, combined with density functional calculations, was employed to explore the spontaneous supramolecular organization of this tripod-shaped molecule under surface confinement. We analyzed the stability of different weak H-bonded patterns and the influence of the concentration of the starting molecule on the 2D supramolecular packing. We found that ordered, densely packed monolayers and 2D porous networks are obtained at high and low concentrations, respectively. A concentration-dependent scanning tunneling microscopy investigation of the molecular self-assembly at a graphite-solution interface revealed supramolecular motifs, which are in perfect agreement with those obtained by simulations. Therefore, our computational approach represents a step forward toward the deterministic prediction of molecular self-assembly at surfaces and interfaces.

Chemical Communications, 2011

Dedicated to Professor Roeland J. M. Nolte on the occasion of his 65th birthday Nanoscale control... more Dedicated to Professor Roeland J. M. Nolte on the occasion of his 65th birthday Nanoscale control over mechanical movement of molecules has been intensely investigated in this decade, aiming at the development of molecular machines that can be implemented in miniaturized systems based on single or few molecules. [1] Molecular movement in such systems can be used directly to create nanocavitands or nanotweezers that can capture/release host molecules [2] or indirectly in order to alter the electronic or optical properties of the systems, for example for the creation of nanoswitches or fluorescence sensors. [4] In this context it is crucial to design molecular systems able to undergo large conformational changes as a result of external stimuli such as light irradiation, [5] metal complexation or change in pH. Among them, pH represents a prototypical biological stimulus and is ideally suited for studies performed in solution or at the solid-liquid interface. A related approach has been already used to trigger conformational switching of molecular grippers [6] that can open or close, or in dynamic chemical devices, [7] where the change of pH can preferentially lead to the complexation or release of metal ions by the system, enabling the reversible contraction/extension of the molecule. However, to exploit such molecular motions the individual building blocks have to be organized into larger functional arrays on meso-and macroscopic length scales at interfaces. This can be accomplished by making use of self-assembly, which is a reliable bottomup approach for the fabrication of functional surfaces. [8] Nevertheless, in view of the development of future applications, there is a need for developing solutions to integrate such a type of switchable system on a given solid substrate and to achieve control of conformational switching over large areas in order to take advantage of collective effects. [5c,e] We describe herein the two-dimensional ordering of molecules adsorbed on surfaces at the solid-liquid interface, that are capable to undergo large conformational changes upon the application of an external chemical stimulus, which can be either a change of pH or the addition of metal ions. As a model system we have chosen a 2,6-bis(1-aryl-1,2,3-triazol-4yl)pyridine (BTP) derivative (Scheme 1), which incorporates a tridentate coordination site consisting of two triazole moieties bridged by a central pyridine ring. [9] The BTP core is decorated with three alkoxy side chains providing enhanced solubility as well as improved propensity to physisorption on highly oriented pyrolitic graphite (HOPG) at the solidliquid interface. We have focused on two BTP derivatives, differing only in the length of their respective alkoxy chains (R 2 = n-C 10 H 21 vs. n-C 18 H 37 ) to modulate the strength of the interaction with the HOPG surface. Due to favorable electrostatic interactions, the "kinked" anti,anti conformation of the BTP core dominates in solution at neutral pH, whereas the repulsive interactions between the lone pair of the nitrogen atoms destabilize the alternative "extended" syn,syn conformation. [9] This repulsive interaction can be switched into an attractive one by the addition of acids or metal ions to the solution, causing either protonation or metalation of the BTP core followed by a large structural change from the "kinked" to its corresponding "extended" conformation. In this paper we provide the first scanning tunneling microscopy (STM) visualization, recorded on the single molecule [a] Dr.

Nanoscale, 2011

One of the greatest challenges in 2D self-assembly at interfaces is the ability to grow spatially... more One of the greatest challenges in 2D self-assembly at interfaces is the ability to grow spatially controlled supramolecular motifs in the third dimension, exploiting the surface as a template. In this manuscript a concentration-dependent study by scanning tunneling microscopy at the solid-liquid interface, corroborated by Molecular Dynamics (MD) simulations, reveals the controlled generation of mono-or bilayer self-assembled Kagom e networks based on a fully planar tetracarboxylic acid derivative. By programming the backbone of the molecular building blocks, we present a strategy to gain spatial control over the adlayer structure by conferring self-templating capacity to the 2D self-assembled network.