A. Cricenti

Chirality Transfer from a Single Chiral Molecule to 2D Superstructures in Alaninol on the Cu(100) Surface

The formation of 2D chiral monolayers obtained by self-assembly of chiral molecules on surfaces has been widely reported in the literature. Control of chirality transfer from a single molecule to surface superstructures is a challenging and important aspect for tailoring the properties of 2D nanostructures. However, despite the wealth of investigations performed in recent years, how chiral transfer takes place on a large scale still remains an open question. In this paper we report a coupling of scanning tunneling microscopy and low energy electron diffraction measurements with an original theoretical approach, combining molecular dynamics and essential dynamics with density functional theory, to investigate self-assembled chiral structures formed when alaninol adsorbs on Cu(100). The peculiarity of this system is related to the formation of tetrameric molecular structures which constitute the building blocks of the self-assembled chiral monolayer. Such characteristics make alaninol/Cu(100) a good candidate to reveal chiral expression changes. We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage or when geometrical confinement prevents long-range order. Conversely, a rotation of 14° with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. An insight to the process leading to a 2D globally chiral surface has been obtained by monitoring molecular assemblies as they grow from the early stages of adsorption, suggesting that the distinctive orientation of the self-assembled monolayer originates from a balance of cooperating forces which start acting only when tetramers pack together to form small clusters.

Detection of Nanostructured Metal in Meteorites: Implications for the Reddening of Asteroids

The association between the most abundant population of meteorites, the ordinary chondrites, and their parent bodies is one of the main topics in the quest to understand the evolution of the solar system. This association is mainly inferred from spectra in visible and near-infrared wavelengths, where many of the asteroids show reddened reflected light curves. The analysis of lunar soils attributed the reddening of the spectra to the presence of nanometer-size metallic particles, and a simulation of micrometeoroid impacts with laser irradiation experiments on terrestrial samples has reproduced this effect and tied it to the vaporization of Fe-bearing silicates. Recently, spacecraft observations have revealed a new mystery in the interpretation of the reddening of S-type asteroids. We have identified an alternative process for surface alteration of airless bodies that can be invoked to solve this mystery through a shock-induced phase transformation of Fe-Ni alloys. These metal phases are usually reported in meteorites but have never been associated with the reddening of the spectra. Here we show, for the first time, atomic force microscopy observations of diffuse nanostructured metal in ordinary chondrites. We also show that the corresponding spectra are unambiguously redder.

Scanning probe microscopy in material science and biology

A review of the activity of scanning probe microscopy at our Institute is presented, going from instrumentation to software development of scanning tunnelling microscopy, atomic force microscopy and scanning near-field optical microscopy (SNOM). Some of the most important experiments in material science and biology performed by our group through the years with these SPM techniques will be presented. Finally, infrared applications by coupling a SNOM with a free electron laser will also be presented.

Optical Detection of core-gold nanoshells inside biosystems

Abstract Metal nanoshells having a dielectric core with a thin gold layer are generating new interest due to the unique optical, electric and magnetic properties exhibited by the local field enhancement near the metal – dielectric core interface. These nanoshells possess strong, highly tunable local plasmon resonances with frequencies dependent upon the nanoshell shape and core material. These unique characteristics have applications in biosensing, optical communication and medicine. In this paper, we developed a theoretical, numerical and experimental approach based on a scanning near optical microscope to identify nanoshells inside mouse cells. Taking advantage of the characteristic near-infrared transparency window of many biological systems, i.e. the low light absorption coefficient of biological systems between 750−1100 nm, we were able to identify a 100−150 nm diameter barium titanate-gold nanoshell inside the h9c2 mouse cells.

Electronic and optical properties of ZnO between 3 and 32 eV

. Electronic transitions involving Zn-3d and O-2s bands are detected.Ab-initio band structure calculations performed at the DFT-LDA level help tointerpret the observed transitions. The calculations are also extended to theGW approximation in order to determine the electronic bandgap. Finally, theplasmon frequency is found to be ~!

AFM-based robust image analysis to contrast reversal effects in cell-cerium oxide nanoparticles interactions

Atomic force microscopy is gaining interest as a technique to quantitatively study biological samples in native environment. However, the measuring principles behind may cause the presence of different sources of artifacts and image degradations. In this work, we present an AFM image analysis tool able to recognize morphological alterations in human leukemia cells after 3 h incubation with the antioxidant cerium oxide nanoparticles. To demonstrate the robustness of the approach to a particular artifact called contrast reversal (CR) effect, consisting in an unexpected switching between repulsive and attractive tip regime during scanning, we present a technique to artificially inject the artefact on the image and then apply the tool. Maximum area under the ROC (AUC) curve results of 0.91 (0.11) in the discrimination between exposed and unexposed cells confirm the validity of the approach and its applicability in AFM-based cell studies.