Fast and Highly Sensitive Ionic‐Polymer‐Gated WS2–Graphene Photodetectors

The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer‐scale electronic devices. Presently, long‐lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate‐voltage pulses, have been employed to achieve bandwidths suitable for applications such as video‐frame‐rate imaging. Here, atomically thin graphene–WS₂ heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 10⁶. Highly mobile ions and the nanometer‐scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS₂. Responsivity R = 10⁶ A W^?1 and detectivity D* = 3.8 × 10¹¹ Jones are observed, approaching that of single‐photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video‐frame‐rate imaging applications.     

Washcoating of low surface area cerium oxide on complex geometry substrates

ABSTRACT

An acid-free formulation based on water, glycerol, and polyvinyl alcohol (PVA) was studied to disperse and stabilize, via steric-like interaction, low surface area cerium oxide powders. A dispersion route that implies a milling process and a proper ratio among the components was experienced. PVA was used as viscosity modulator, to enhance viscosity and system stability. Newtonian fluids, suitable for foams dip-coating, were obtained in the application shear range. Foams with different porosities (20, 30, and 40 pore per inch density) were coated. It was found that withdrawal velocity did not affect deposition: a constancy in coating load was obtained once rheology was fixed, while multiple dipping was effective to enhance load. An optimal flash drying temperature (350°C) was identified to consolidate the coated layer and to decompose the organic additives. Good loads, homogeneous coverage, and no pore clogging were obtained after calcination at 900°C. Even though acceptable weight losses were obtained, further investigations need to be accomplished to understand data scattering after adhesion tests.     

Historical profiles of chlorinated paraffins and polychlorinated biphenyls in a dated sediment core from Lake Thun (Switzerland)

A dated sediment core from Lake Thun covering the last 120 years was analyzed to get an overview of the historical trend of the chlorinated paraffin (CP) and polychlorinated biphenyl (PCB) deposition, because CPs and PCBs have/had similar applications as plasticizers and flame retardants. Total CP concentrations (sum of short chain (SCCP), medium chain (MCCP), and long chain CPs (LCCP)) showed a steep increase in the 1980s and a more-or-less stable level of 50 ng g(-1) dry weight (dw) since then. The concentration-time profile is in good agreement with the available information on global production data. The quantification of higher chlorinated SCCPs using electron capture negative ionization low resolution mass spectrometry (ECNI-LRMS) revealed an increase in recent years. In addition, the degree of chlorination of SCCPs has strongly increased during the past 40 years, which may indicate its use as an additive for plastics, paints, and coatings. Furthermore, PCBs were analyzed in dated sediment slices. The PCB concentrations (sum of the six indicator congeners) peaked around 1969 (18 ng g(-1) dw) and decreased to 1.3 ng g(-1) dw in the surface layer corresponding to 2004. The peak level of CPs exceeded those of PCBs by about a factor of 3.     

Assessing the origin and fate of Cr, Ni, Cu, Zn, Pb, and V in industrial polluted soil by combined microspectroscopic techniques and bulk extraction methods

The major geochemical forms of Cr, Ni, Cu, Zn, Pb, and V in a soil from an industrial polluted site in the south of Italy were determined by means of synchrotron X-ray microanalytical techniques such as coupled micro-X-ray fluorescence/micro-X-ray diffraction and micro-X-ray absorption near edge structure spectroscopy in combination with bulk extraction methods (sequential extraction procedures, EDTA extractions, and toxicity leaching characteristic procedure tests). Cr, Ni, Zn, and Cu were found in spinel-type geochemical forms (chromite, trevorite, franklinite, zincochromite, and cuprospinel) and often in association with magnetite and hematite. Vwas mainly present as V(V) associated with iron-oxides or in the form of volborthite [Cu3(OH)2V2O7.2H2O]. Pb was speciated as minium (Pb3O4), lanarkite [Pb2O(SO4)], and, in association with Cr(VI), as crocoite (PbCrO4). In general, despite a high total concentration, metals appear to be speciated for the most part as rather insoluble geochemical forms. However, particular attention should be paid to Zn, Cu, V, and Pb that show non-negligible mobilizable fractions. On the basis of the geochemical forms identified, among others, two major former industrial activities were tentatively ascribed as being responsible for the observed major pollution: polyvinyl chloride and cement-asbestos productions.     

Scouting around 1,2,3,4-Tetrahydrochromeno[3,2-c]pyridin-10-ones for Single- and Multitarget Ligands Directed towards Relevant Alzheimer's Targets

A number of 1,2,3,4-tetrahydrochromeno[3,2-c]pyridin-10-one derivatives have been synthesized and screened against different targets involved in the onset and progression of Alzheimer's disease (AD), such as acetyl- and butyrylcholinesterase (AChE and BChE), monoamine oxidases A and B (MAO A and B), aggregation of β-amyloid (Aβ) and reactive oxygen species (ROS) production. Derivatives 1 c , 3 b , 4 and 5 a showed multifaceted profiles of promising anti-AD features and returned well-balanced multitargeting inhibitory activities. Moreover, compound 1 f , a potent and selective human MAO B inhibitor (IC₅₀=0.89 μM), proved to be a safe neuroprotectant in a human neuroblastoma cell line (SH-SY5Y) by improving viability impaired by Aβ_1–42 and pro-oxidant insult. Furthermore, structure–activity relationships (SARs) and docking models were derived in order to assist further hit-to-lead optimization stage.     

Coupling a Stirling engine with a fluidized bed combustor for biomass

The paper deals with the integration between a kinematic Stirling engine and a fluidized bed combustor for micro-scale cogeneration of renewable energy. A pilot-scale facility integrating a 40 kW_t combustor and a γ-type Stirling engine (0.5 kW_e) was set up and tested to demonstrate the feasibility of this solution. The Stirling engine was installed at a lateral wall of the combustor in direct contact with the fluidized bed region. An experimental campaign was executed to assess the performance of the innovative integrated system. The experimental results can be summarized in: (a) very high combustion efficiency with biomass feeding, (b) elevated heat transfer rate to the engine, (c) a relatively small share (about 2 kW_t) transferred to the engine from the thermal power generated by the combustor (around 13 kW_t), (d) conversion to electric power close to the upper limit of the engine, (e) limited impact of the Stirling engine on the fluidized bed behavior, for example, temperature. From the analysis of measured variables, the dynamics is dominated by the fast response of the Stirling engine, which rapidly reacts to the slow changes of the fluidized bed combustor regime: the dynamic response of the tested facility as a thermal system was slow, the time constant being of the order of 10 minutes.     

The use of Raman spectroscopy in the analysis of UHMWPE uni-condylar bearing systems after run on a force and displacement control knee simulators

The complications associated with prosthetic failure and revision surgery still constitute the main clinical problem. The objective of wear evaluation is to determine the wear rate and its dependence on the test conditions. To obtain realistic results, a wear test can be performed to reproduce in vivo working conditions and compare the wear characteristics of various total knee prostheses designs.Two knee wear simulators with different input control mechanisms, displacement and force controlled, were used to assess the wear behavior of ultra-high molecular weight polyethylene uni-condylar knee prostheses. The differences in wear behavior were assessed using a state-of-art coordinate measuring machine; Raman spectroscopy was used to evaluate the possible crystallinity changes on the uni-condylar menisci induced by mechanical stress. These results were compared with available uni-condylar retrievals.Scratches were visible along the anterior-posterior direction emphasizing that the motion was constant during the movements under the displacement control simulation. On the contrary, different kinematics schemes were observed under the force controlled simulation. The structural Raman markers showed a good correlation with the coordinate measuring machine data, and in particular with the depth of the concavity formed upon in vitro testing or in vivo service. With regards to the in vitro tested components, the specimens tested under force controlled simulator, which underwent a higher volumetric loss, showed a higher increase of the amorphous content. At a molecular level, the wear mechanism did not appear significantly different for the three sets of specimens, with the exception of the amorphous content which, upon wear, increased in the in vitro tested components, while decreased in the retrievals.