arXiv subjects

Filippo Fabbri

Publications and source records attributed to Filippo Fabbri.

22 records · Page 2Linked to original sources

arXiv2019

Scanning tunneling microscopy and Raman evidences of silicene nanosheets intercalated into graphite surface at room temperature

Highly oriented pyrolitic graphite (HOPG) is an inert substrate with a structural honeycomb lattice, well suited for the growth of two-dimensional (2D) silicene layer. It was reported that when Si atoms are deposited on HOPG surface at room temperature, they arrange in two configurations: silicene nanosheets and three dimensional clusters. In this work we demonstrate, by using scanning tunneling microscopy (STM) and Raman spectroscopy, that a third configuration stabilizes in the form of Si 2D nanosheets intercalated below the first top layer of carbon atoms. The Raman spectra reveal a structure located at 538 cm$^{-1}$ which we ascribe to the presence of sp$^2$ Si hybridization. Moreover, the silicon deposition induces several modifications in the graphite D and G Raman modes, which we interpret as an experimental evidence of the intercalation of the silicene nanosheets. The Si atom intercalation at room temperature takes place at the HOPG step edges and it detaches only the outermost graphene layer inducing a strong tensile strain mainly concentrated on the edges of the silicene nanosheets. Theoretical calculations of the structure and energetic viability of the silicene nanosheets, of the strain distribution on the outermost graphene layer and its influence on the Raman resonances support the STM and Raman observations.

cond-mat.mtrl-sci↗

arXiv2019

A sensitive calorimetric technique to study energy (heat) exchange at the nano-scale

Every time a chemical reaction occurs, an energy exchange between reactants and environment exists, which is defined as the enthalpy of the reaction. In the last decades, research has resulted in an increasing number of devices at the micro- or nano-scale. Sensors, catalyzers, and energy storage systems are more and more developed as nano-devices which represent the building blocks for commercial "macroscopic" objects. A general method for the direct evaluation of the energy balance of such systems is not available at present. Calorimetry is a powerful tool to investigate energy exchange, but it usually needs macroscopic sample quantities. Here we report on the development of an original experimental setup able to detect temperature variations as low as 10 mK in a sample of 10 ng using a thermometer device having physical dimensions of 5x5 mm2. The technique has been utilized to measure the enthalpy release during the adsorption process of H2 on a titanium decorated monolayer graphene. The sensitivity of these thermometers is high enough to detect a hydrogen uptake of 10^(-10) moles, corresponding to 0.2 ng, with an enthalpy release of about 23 uJ. The experimental setup allows, in perspective, the scalability to even smaller sizes.

physics.chem-ph↗

arXiv2018

Low-defectiveness exfoliation of MoS2 nanoparticles and their embedment in hybrid light-emitting polymer nanofibers

Molybdenum disulfide (MoS2) has been attracting extraordinary attention for its intriguing optical, electronic and mechanical properties. Here we demonstrate hybrid, organic-inorganic light-emitting nanofibers based on MoS2 nanoparticle dopants obtained through a simple and inexpensive sonication process in N-methyl-2-pyrrolidone and successfully encapsulated in polymer filaments. Defectiveness is found to be kept low, and stoichiometry preserved, by the implemented, gentle exfoliation method that allows the MoS2 nanoparticles to be produced. So-achieved hybrid fibers are smooth, uniform, flawless, and exhibit bright and continuous light emission. Moreover, they show significant capability of waveguiding self-emitted light along their longitudinal axis. These findings suggest the use of emissive MoS2 fibers enabled by gentle exfoliation methods as novel and highly promising optical material for building sensing surfaces and as components of photonic circuits.

cond-mat.mtrl-sci↗

arXiv2015

A Closer Look at the Light Induced Changes in the Visco-elastic Properties of Azobenze-Containing Polymers by Statistical Nanoindentation

The mechanical properties of azobenzene-containing polymer films are statistically measured by instrumented nanoindentation experiment in the dark and under illumination in the absorption band of the azobenzene molecules, with special emphasis on the creep behavior and recoverability. We use Dispersed Red 1 azobenzene derivatives, which remain in the stable trans isomer state in the dark and form a dynamical photo-stationary state between cis and trans isomer under illumination. Light induces a higher change in the film hardness than in the elastic stiffness, revealing the occurrence of a visco-plastic behavior of the film under illumination. Creep experiments performed at a constant load show a striking dissipative effect linked to the mass flowing under polarized illumination.

cond-mat.mtrl-sci↗