Observation of different charge transport regimes and large magnetoresistance in graphene oxide layers

We report a systematic study on charge transport properties of thermally reduced graphene oxide (rGO) layers, from room temperature to 2 K and in presence of magnetic fields up to 7 T. The most conductive rGO sheets follow different transport regimes: at room temperature they show an Arrhenius-like behavior. At lower temperature they exhibits a thermally activated behavior with resistance R following a R = R0exp(T0/T)p law with p = 1/3, consistently with 2D Mott Variable Range Hopping (VRH) transport mechanism. Below a given temperature Tc, we observe a crossover from VHR to another regime, probably due to a shortening of the characteristic lengths of the disordered 2D system. The temperature Tc depends on the reduction grade of the rGO. Magnetoresistance DR/R of our rGO films shows as well a crossover between positive and negative and below liquid He temperature DR/R reaches values larger than 60%, surprisingly high for a \u2013 nominally \u2013 non magnetic material

Circular economy and integrated supply chains for exploitation of the waste biomass coffee silverskin to polyphenols responsible for the antioxidant activity

Coffee is one of the most consumed drinks all over the world with a production higher than 10 million tons in 2018, generating, every year, the largest amount of wastes during the coffee beans processing. Among these by-products, coffee silverskin (CS) is one of the most interesting compounds generated as a waste of the roasting process. Today, it has been estimated that for 100 tons of coffee as final product, 0.8 tons of CS are produced. Up to now, these residues have no special use, being mostly discharged in landfill or burned. On the other hand, in the last years, CS has attracted great attention as a promising source of bioactive compounds, including polyphenols and caffeine. However, in order to valorize them, they should be isolated from the starting matrix through suitable extraction processes. On this basis, the aim of the present research is the investigation and the optimization of the solid-liquid extraction from CS of polyphenols responsible for the antioxidant activityadopting microwave irradiation. The influence of the main reaction parameters, such as temperature, extraction time and composition of the solvent, a binary mixture of water/ethanol, has been assessed, also employing statistical modeling. The achieved polyphenols yields are higher than those reported in the literature and this study represents a step forwardin the perspective of recycling and circular economy

Una funzione in R per la categorizzazione 'ottima' di una variabile continua

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Multiscale Charge Transport in van der Waals Thin Films: Reduced Graphene Oxide as a Case Study

Large area van der Waals (vdW) thin films are assembled materials consisting of a network of randomly stacked nanosheets. The multiscale structure and the two-dimensional (2D) nature of the building block mean that interfaces naturally play a crucial role in the charge transport of such thin films. While single or few stacked nanosheets (i.e., vdW heterostructures) have been the subject of intensive works, little is known about how charges travel through multilayered, more disordered networks. Here, we report a comprehensive study of a prototypical system given by networks of randomly stacked reduced graphene oxide 2D nanosheets, whose chemical and geometrical properties can be controlled independently, permitting to explore percolated networks ranging from a single nanosheet to some billions with room-temperature resistivity spanning from 10-5 to 10-1 ω\ub7m. We systematically observe a clear transition between two different regimes at a critical temperature T*: Efros-Shklovskii variable-range hopping (ES-VRH) below T∗ and power law behavior above. First, we demonstrate that the two regimes are strongly correlated with each other, both depending on the charge localization length ζ, calculated by the ES-VRH model, which corresponds to the characteristic size of overlapping sp2 domains belonging to different nanosheets. Thus, we propose a microscopic model describing the charge transport as a geometrical phase transition, given by the metal-insulator transition associated with the percolation of quasi-one-dimensional nanofillers with length ζ, showing that the charge transport behavior of the networks is valid for all geometries and defects of the nanosheets, ultimately suggesting a generalized description on vdW and disordered thin films

Impact of invasive aspergillosis occurring during first induction therapy on outcome of acute myeloid leukaemia (SEIFEM‐12B study)

Acute myeloid leukemia (AML) patients are at high risk of invasive aspergillosis (IA) after first induction chemotherapy (CHT). Although IA risk factors have been identified, few data are available on impact of IA, occurring during induction phase, on overall AML outcome