arXiv subjects

Maria Caporali

Publications and source records attributed to Maria Caporali.

7 recordsLinked to original sources

arXiv2019

Enhanced ambient stability of exfoliated black phosphorus by passivation with nickel nanoparticles

Since its discovery, the environmental instability of exfoliated black phosphorus (2D bP) has emerged as a challenge that hampers its wide application in chemistry, physics, and materials science. Many studies have been carried out to overcome this drawback. Here we show a relevant enhancement of ambient stability in few-layer bP decorated with nickel nanoparticles as compared to pristine bP. In detail, the behavior of the Ni-functionalized material exposed to ambient conditions in the dark is accurately studied by TEM (Transmission Electron Microscopy), Raman Spectroscopy, and high resolution X-ray Photoemission and Absorption Spectroscopy. These techniques provide a morphological and quantitative insight of the oxidation process taking place at the surface of the bP flakes. In the presence of Ni NPs, the decay time of 2D bP to phosphorus oxides is more than three time slower compared to pristine bP, demonstrating an improved structural stability within twenty months of observation.

physics.chem-ph↗

arXiv2019

A Perspective on Recent Advances in Phosphorene Functionalization and its Application in Devices

Phosphorene, the 2D material derived from black phosphorus, has recently attracted a lot of interest for its properties, suitable for applications in material science. In particular, the physical features and the prominent chemical reactivity on its surface render this nanolayered substrate particularly promising for electrical and optoelectronic applications. In addition, being a new potential ligand for metals, it opens the way for a new role of the inorganic chemistry in the 2D world, with special reference to the field of catalysis. The aim of this review is to summarize the state of the art in this subject and to present our most recent results in preparation, functionalization and use of phosphorene and its decorated derivatives. In particular, we discuss several key points, which are currently under investigation: the synthesis, the characterization by theoretical calculations, the high pressure behaviour of black phosphorus, as well as decoration with nanoparticles and encapsulation in polymers. Finally, device fabrication and electrical transport measurements are overviewed on the basis of recent literature and new results collected in our laboratories.

cond-mat.mes-hall↗

arXiv2019

Black Phosphorus/Palladium Nanohybrid: Unraveling the Nature of P-Pd Interaction and Application in Selective Hydrogenation

The burgeoning interest in 2D black phosphorus (bP) contributes to expand its applications in countless fields. In the present study, 2D bP is used as a support for homogeneously dispersed palladium nanoparticles directly grown on it by a wet chemical process. EELS-STEM analysis evidences a strong interaction between palladium and P atoms of bP nanosheets. A quantitative evaluation of this interaction comes from XAS measurements that find out a very short Pd-P distance of 2.26 Å proving for the first time the existence of an unprecedented Pd-P coordination bond of covalent nature. Additionally, the average Pd-P coordination number of about 1.7 reveals that bP acts as a polydentate phosphine ligand towards the surface Pd atoms of the nanoparticles, thus preventing their agglomeration and inferring structural stability. These unique properties result in a superior performance in the catalytic hydrogenation of chloronitroarenes to chloroaniline, where a higher chemoselectivity in comparison to other heterogeneous catalyst based on palladium has been observed.

physics.chem-ph↗

arXiv2018

Non-Classical Longitudinal Magneto-Resistance in Anisotropic Black Phosphorus

Resistivity measurements of a few-layer black phosphorus (bP) crystal in parallel magnetic fields up to 45 T are reported as a function of the angle between the in-plane field and the source-drain (S-D) axis of the device. The crystallographic directions of the bP crystal were determined by Raman spectroscopy, with the zigzag axis found within 5° of the S-D axis, and the armchair axis in the orthogonal planar direction. A transverse magneto-resistance (TMR) as well as a classically-forbidden longitudinal magneto-resistance (LMR) are observed. Both are found to be strongly anisotropic and non-monotonic with increasing in-plane field. Surprisingly, the relative magnitude (in %) of the positive LMR is larger than the TMR above $\sim$32 T. Considering the known anisotropy of bP whose zigzag and armchair effective masses differ by a factor of approximately seven, our experiment strongly suggests this LMR to be a consequence of the anisotropic Fermi surface of bP.

cond-mat.mes-hall↗

arXiv2017

Decoration of exfoliated black phosphorus with nickel nanoparticles and application in catalysis

Nickel nanoparticles were dispersed on the surface of exfoliated black phosphorus and the resulting nanohybrid Ni/2DBP showed an improved stability respect to pristine 2D BP when kept in ambient conditions in the darkness. Ni/2DBP was applied as catalyst in the semihydrogenation of phenylacetylene and exhibited high conversion and selectivity towards styrene. These features were preserved after recycling tests revealing the high stability of the nanohybrid.

cond-mat.mes-hall↗

arXiv2017

Novel polystyrene-based nanocomposites by phosphorene dispersion

Polystyrene-based phosphorene nanocomposites were prepared by a solvent blending procedure allowing the embedding of black phosphorus (BP) nanoflakes in the polymer matrix. Raman spectroscopy, X Ray Diffraction and TEM microscopy were employed to characterize the structural and the morphological characteristics of the achieved hybrids, with the aim to evaluate the dispersion level of black phosphorus layers. TGA, DSC analysis as well as thermal oxidation and photo-degradation techniques were employed to investigate the thermal- and the photo-stability of the samples. The collected results evidenced better thermal and photostability of both polymer matrix and dispersed layered phosphorus, suggesting really interesting polymer-nanofiller synergic effects ascribable to the presence and the good dispersion of the 2D-nanomaterial.

physics.chem-ph↗

arXiv2015

The role of water in the preparation and stabilization of high quality phosphorene flakes

Water is believed to be harmful for the stability of phosphorene.On the contrary, the presence of small amount of water allows the synthesis of high-quality material in liquid exfoliation of black phosphorus using dimethylsulfoxide as solvent. A phosphorus/water molar ratio between 1.5 and 14 maximizes the quality of the phosphorene flakes and their stability.

cond-mat.mes-hall↗