Effect of mesoscopic inhomogeneities on local tunnelling density of states

We carry out a theoretical analysis of the momentum dependence of the Fourier-transformed local density of states (LDOS) in the superconducting cuprates within a model considering the interference of quasiparticles scattering on quenched impurities. The impurities introduce an external scattering potential, which is either nearly local in space or it can acquire a substantial momentum dependence due to a possible strong momentum dependence of the electronic screening near a charge modulation instability. The key new effect that we introduce is an additional mesoscopic disorder aiming to reproduce the inhomogeneities experimentally observed in scanning tunnelling microscopy. The crucial effect of this mesoscopic disorder is to give rise to point-like spectroscopic features, to be contrasted with the curve-like shape of the spectra previously calculated within the interfering-quasiparticle schemes. It is also found that stripe-like charge modulations play a relevant role to correctly reproduce all the spectral features of the experiments.Comment: 11 pages and 5 figure

. Microwave-assisted solvothermal controlled synthesis of Fe-Co

Syntheses of bimetallic cobalt-iron-based nanoparticles starting from Co(acac)2 and Fe(acac)3 (acac = acetylacetonate) were carried out by microwave-assisted solvothermal process, using ethylene glycol as the solvent and (polyvinylpyrrolidone) PVP, as the stabilizer. Indeed, the reaction mechanism in the presence of ethylene glycol is well understood [1] with the role of PVP being the inhibition of nanoparticles growth [2]. However, the control of the morphology of the synthetized nanoparticles is still a great challenge. Herein, we demonstrated that by adding amines to the reaction mixture, it is possible to control the morphology of the prepared bimetallic cobalt-iron materials. Thus, different Co-Fe micro-composites were synthetized by an innovative microwave assisted solvothermal synthesis, which allows to considerably reduce reaction time from 12 h to 15 min, with respect to classical thermal methods. The procedure was optimized by varying several parameters, such as: amount of PVP, in the presence or in the absence of amines, reaction temperature. The dark brown obtained powders were characterized by scanning electron microscopy, infrared spectroscopy and thermogravimetric analysis, confirming the beneficial effect of the presence of the amine in the morphology of the obtained composites. The obtained results open a new scenario for further studies on the possibility to control the morphology of bimetallic composite materials. [1] Fievet F, Lagier J P and Figlarz M Mater. Res. Soc. Bull. 24 (1989) 29–34 [2] Teranishi T, Kurita R and Miyake M J. Inorg. Organometall. Polym. 10 (2000) 145–5

The dynamical structure factor in topologically disordered systems

A computation of the dynamical structure factor of topologically disordered systems, where the disorder can be described in terms of euclidean random matrices, is presented. Among others, structural glasses and supercooled liquids belong to that class of systems. The computation describes their relevant spectral features in the region of the high frequency sound. The analytical results are tested with numerical simulations and are found to be in very good agreement with them. Our results may explain the findings of inelastic X-ray scattering experiments in various glassy systems.Comment: Version to be published in J. Chem. Phy

Synthesis and activity of -Fe2O3 nanoparticles in the catalytic reduction of halonitroarenes under sustainable conditions

Abstract. The catalytic reduction of nitroarenes towards anilines is an important reaction from both academic and industrial points of view, being the resulting products important intermediates to produce dyes, agrochemicals, pigments, and pharmaceuticals. In addition, removal of nitroarene pollutants from water by reducing them into anilines is a valuable method to purify contaminated matrices. Such reductive reactions are frequently carried out by using noble metal catalysts [1], which are usually very active and recyclable in some cases. Recently, the use of earth abundant metal catalysts has gained great interest especially for economic reasons, as these materials are generally cheap and easy to be reached [2]. In this framework, iron oxides catalysts are very attractive because they are cheap and not toxic. Herein, we report on the synthesis of α-Fe2O3 nanoparticles (NPs) of size ranging from 50 to 80 nm starting from a porous organic polymer (POP) containing Fe(III) sites, which was in turn annealed at 400°C. The obtained NPs were characterized by SEM-EDX, XRPD, IR and TXRF and were employed as active and recyclable catalysts in the reduction of p-bromonitrobenzene into p-bromo-aniline, using hydrazine hydrate in ethanol, taken as the model reaction. [1] Dell’Anna, M.M.; Intini, S.; Romanazzi, G.; Rizzuti, A.; Leonelli, C.; Piccinni, F.; Mastrorilli, P. J. Mol. Catal. A: Chem. 2014, 395, 307–314. [2] Romanazzi, G.; Fiore, A.M.; Mali, M.; Rizzuti, A.; Leonelli, C.; Nacci, A.; Mastrorilli, P.; Dell'Anna, M. M. Mol. Catal., 2018, 446, 31–3

Microwave-Assisted Treatment of Waste Wood Biomass with Deep Eutectic Solvents

Abstract. The increasing depletion of fossil feeds and the environmental concerns linked to the use of traditional energy sources have stimulated both academic and industrial worlds in exploiting new sustainable and renewable suppliers of raw materials [1]. In this framework, lignocellulosic biomass can play an important role, acting as the starting material of a biorefinery leading to biofuels, chemicals, and other value-added products, commonly obtained from petroleum. Recently, numerous protocols for processing lignocellulosic biomass of selected plants have been reported. However, developing an environment-friendly method is still a big goal. This challenge becomes more interesting if lignocellulosic biomass coming from wood wastes could be efficiently treated. Deep eutectic solvents (DESs) are new sustainable and cheap reaction media, combining the features of ionic liquids and organic solvents. They are made by association of hydrogen-bond donors and hydrogen-bond acceptors, and they can promote the hydrolysis of lignocellulosic bonds [2]. Herein, we report on the microwave-assisted treatment of waste wood flours with DESs formed by choline chloride and oxalic acid to get a cellulosic residue separated from lignin degradation products, identified by NMR spectroscopy. The insoluble deposit was characterized by SEM, TGA, DSC, FTIR-ATR and 13C CP/MAS NMR techniques and could be available for further uses such as nanocellulose production. [1] Haldar D., Purkait M.K. Chemosphere 2021, 128523. [2] Liu S., Zhang Q., Gou S., Zhang L., Wang Z. Carbohydr. Polym. 2021, 251, 11701

Superconducting non-equilibrium transport through a weakly interacting quantum dot

We study the out-of-equilibrium current through an interacting quantum dot modelled as an Anderson impurity contacted by two BCS superconductors held at fixed voltage bias. In order to account for multiple Andreev reflections, we develop a Keldysh Green's function scheme perturbative in the dot's interaction strength. We find an unexpected enhancement of the current due to repulsive interactions for small lead-to-dot couplings.Comment: 6 pages, 6 figures, replaced with published versio

How calcination affects the morphology and the catalytic activity of polymer supported Nickel

A nickel containing monomer, Ni(AAEMA)2 (AAEMA = deprotonated form of 2-(acetoacetoxy) ethyl methacrylate) was co-polymerized with ethyl methacrylate (co-monomer) and ethylene glycol dimethacrylate (cross-linker) [1]. The obtained polymer was a green methacrylic resin containing Ni(II) centers homogeneously dispersed in the catalyst, which resulted insoluble in all common organic solvents and in water. The material can be described as an amphiphilic resin, air and moisture stable, with the peculiarity to swell in halogenated solvents, acetone and water and to shrink in diethyl ether and petroleum ether. The polymer was calcined under reductive conditions (dihydrogen with initial pressure of 5 bar) following two procedures, differing from each other for the cooling conditions. In the first procedure the calcined material was cooled under dihydrogen gas, while in the second one the cooling step occurred under air. After calcination, the green Ni(II) based co-polymer turned into black resins, Ni-res1 (obtained with hydrogen cooling) and Ni-res2 ((obtained with air cooling). TEM analyses showed that both Ni-res1 and Ni-res2 supported Ni nanoparticles with different morphologies, being the metal nanoparticles onto Ni-res1 smaller than the ones dispersed in Ni-res2, that had an urchin-like shape. Both Ni based co-polymers were tested as catalysts in the reduction of nitrobenzene with NaBH4 [2]. Ni-res1 resulted more active and selective towards aniline, with respect to Ni-res2. [1] M.M. Dell’Anna, G. Romanazzi, P. Mastrorilli, Curr. Org. Chem. 17 (2013) 1236 [2] A.M. Fiore, G. Romanazzi, M.M. Dell’Anna, M. Latronico, C. Leonelli, A. Rizzuti, M. Mali, P. Mastrorilli, Mol. Catal. 476 (2019) 11050

Critical temperature of non-interacting Bose gases on disordered lattices

For a non-interacting Bose gas on a lattice we compute the shift of the critical temperature for condensation when random-bond and onsite disorder are present. We evidence that the shift depends on the space dimensionality D and the filling fraction f. For D -> infinity (infinite-range model), using results from the theory of random matrices, we show that the shift of the critical temperature is negative, depends on f, and vanishes only for large f. The connections with analogous results obtained for the spherical model are discussed. For D=3 we find that, for large f, the critical temperature Tc is enhanced by disorder and that the relative shift does not sensibly depend on f; at variance, for small f, Tc decreases in agreement with the results obtained for a Bose gas in the continuum. We also provide numerical estimates for the shift of the critical temperature due to disorder induced on a non-interacting Bose gas by a bichromatic incommensurate potential.Comment: 18 pages, 8 figures; Fig. 8 improved adding results for another value of q (q=830/1076

Multiple Andreev reflections in a quantum dot coupled to superconducting leads: Effect of spin-orbit coupling

We study the out of equilibrium current through a multilevel quantum dot contacted to two superconducting leads and in the presence of Rashba and Dresselhaus spin-orbit couplings, in the regime of strong dot-lead coupling. The multiple Andreev reflection (MAR) subgap peaks in the current-voltage characteristics are found to be modified (but not suppressed) by the spin-orbit interaction in a way that it strongly depends on the shape of the dot confining potential. In a perfectly isotropic dot the MAR peaks are enhanced when the strength αR and αD of Rashba and Dresselhaus terms are equal. When the anisotropy of the dot confining potential increases, the dependence of the subgap structure on the spin-orbit angle $theta=arctan(alpha_D/αlpha_R)$ decreases. Furthermore, when an in-plane magnetic field is applied to a strongly anisotropic dot, the peaks of the nonlinear conductance oscillate as a function of the magnetic-field angle and the location of the maxima and minima allows for a straightforward read-out of the spin-orbit angle $theta

Observation of Umklapp processes in non-crystalline materials

Umklapp processes are known to exist in cristalline materials, where they control important properties such as thermal conductivity, heat capacity and electrical conductivity. In this work we report the provocative observation of Umklapp processes in a non-periodical system, namely liquid Lithium. The lack of a well defined periodicity seems then not to prevent the existence of these scattering processes mechanisms provided that the local order of the systems i.e. the maxima of the static structure factor supply the equivalent of a reciprocal lattice vector in the case of cristalline materials.Comment: 13 pages P