Centre d’Élaboration de Matériaux et d’Etudes Structurales (UPR 8011)

Accueil > Recherche > SINanO : Surfaces, Interfaces et Nano-Objets > Thématiques de Recherche

Interaction between a surface and an atom, a molecule or an organic medium

SINanO Highlights

On the role of intermolecular interactions in stabilizing AuNP@Ampicillin nano-antibiotics

Xavier Fenouillet, Magali Benoit and Nathalie Tarrat

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The fight against antibiotic resistance has become a major public health issue in recent years. In this context, nano-antibiotics composed of gold nanoparticles with antibiotics grafted on their surface often exhibit outstanding properties, sometimes even bypassing bacterial resistance mechanisms. Among these nano-antibiotics, gold nanoparticles/ampicillin hybrid systems (AuNPs@Ampicillin) are very effective. However, despite their very promising antibacterial properties, very little information concerning their atomic-scale structure is reported in the literature. In the present paper, the structure and energetics of AuNPs@Ampicillin nano-antibiotics have been investigated using first-principles numerical simulations through the study of the ampicillin adsorption on the three low Miller index facets Au(111), Au(100) and Au(110) of the AuNPs as a function of both the antibiotics coverage and its protonation state. Intermolecular interactions were found to be very stabilizing for coverages compatible with experimental data. An optimal coverage zone has been determined, in which the combination of a favorable gold surface-antibiotics interaction and of stabilizing intermolecular interactions can lead to an overall stabilization of the nano-antibiotics. As regards the mechanism of action of the nano-antibiotics, this study has confirmed that the active site of the free antibiotic is exposed to the solvent when the antibiotic is grafted onto the gold nanoparticle.


Adsorption energy of small molecules on core-shell Fe@Au nanoparticles  : tuning by shell thickness

Magali Benoit, Nathalie Tarrat and Joseph Morillo

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The adsorption of several small molecules on different gold surfaces, Au(001), strained Au(001) and Au(001) epitaxied on Fe(001), has been characterized using density functional theory. The surface strain leads to a less energetically favourable adsorption for all studied molecules. Moreover, the presence of the iron substrate induces an additional decrease of the binding energy, for 1 and 2 Au monolayers. For carbon monoxide CO, the structural and energetic variations with the number of Au monolayers deposited on Fe have been analyzed and correlated with the distance between the carbon atom and the gold surface. The effect of the subsurface layer has been evidenced for 1 and 2 monolayers. The other molecules show different quantitative behavior depending on the type of their interaction with the gold surface. However, the iron substrate weakens the interaction, either for the chemisorbed species or for the physisorbed ones. 2 Au monolayers seems like the best compromise to decrease the reactivity of the gold surface towards adsorption while preventing the Fe oxidation.

The gold/ampicillin interface at the atomic scale

N. Tarrat, M. Benoit, M. Giraud, A. Ponchet and M. J. Casanove

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In the fight against antibiotic resistance, gold nanoparticles (AuNP) with antibiotics grafted on their surfaces have been found to be potent agents. Ampicillin-conjugated AuNPs have been thus reported to overcome highly ampicillin-resistant bacteria. However, the structure at the atomic scale of these hybrid systems remains misunderstood. In this paper, the structure of the interface between an ampicillin molecule AMP and three flat gold facets Au(111), Au(110) and Au(100) has been investigated with numerical simulations (dispersion-corrected DFT). Adsorption energies, bond distances and electron densities indicate that the adsorption of AMP on these facets goes through multiple partially covalent bonding. The stability of the AuNP/AMP nanoconjugates is explained by large adsorption energies and their potential antibacterial activity is discussed on the basis of the constrained spatial orientation of the grafted antibiotic.