Journals
2014 EN
Barella Silvia · Gruttadauria Andrea · Mapelli Carlo
+5 more
This study is focused on the sensitivity of ultra‐sonic test (UT) performed on special carbon steel as a function of their microstructure. UTs was carried out on several samples divided into two families and featured by different process‐histories. The estimation of the attenuation of the ultrasonic signals as a function of the microstructural features was performed. The samples underwent different thermal treatments to modify their parent austenite grain size and the associated martensite islands by re‐austenitization process and by the following grain growth. The difference of UT results mainly depends upon the wave scattering and the energy absorption due to the difference in the grain size and in the crystal lattice orientation.
Journals
2014 EN
Henderson Hunter B. · Rios Orlando · Bryan Zachary L.
+5 more
Magneto‐acoustic mixing technology is evaluated as a method for manufacturing metal‐matrix nanocomposites. This technology relies on the interaction of two magnetic fields to produce high‐intensity acoustic waves suitable for melt processing of liquid metals, inducing sonic cavitation and dispersing nanoparticles. Considerations for alignment of particles in the system are also considered.
Journals
2014 EN
Bussetti Gianlorenzo · Campione Marcello · Riva Michele
+10 more
A major challenge in molecular electronics is to develop logic devices based on a truly intramolecular switching mechanism. Recently, a new type of molecular device has been proposed where the switching characteristic is mediated by the bistability in the position of the two hydrogen atoms which can occupy different, energetically equivalent positions (tautomerization) in the inner cavity of porphyrins and naphthalocyanines. Up to now, such a reaction has only been exploited at low temperatures and induced or detected through atomic scale manipulation. In addition, the unpredictability of the tautomer orientation currently excludes molecular interconnection to functional electronic circuits. Here, full evidence is provided that, following a newly proposed growth strategy, 2D layers of metal‐free tetraphenylporphyrins (H 2 TPP) show frozen tautomerization even at room temperature on macroscopic domains, with the H atoms aligned along a direction settled a priori. This behavior is ascribed to the buckling of the molecule, anchored to the substrate, which removes the degeneracy between the two tautomer alignments. On this basis, a new way to exploit uniaxially oriented H 2 TPP tautomers in a first elementary logic device is proposed.
Journals
2014 EN
Pilia Luca · Serri Michele · Matsushita Michio M.
+3 more
The magnetic, thin‐film structural, conductivity, and magnetoresistance properties of [Ni(quinoline‐8‐thiolate) 2 ] ([Ni(qt) 2 ]) are studied. The conducting and magnetoresistance properties are studied in single crystals and in evaporated thin films through deposition on an interdigitated electrode array. Non‐linear conductivity interpreted through a space‐charge limited conduction mechanism with charges injected from the electrodes is observed. Under applied magnetic field, the material displays giant negative magnetoresistance above 50% at 2 K in both single crystals and in evaporated thin films. The effect can still be observed at 200 K and is interpreted in terms of a double exchange mechanism with the shape of the curve determined by the magnetic anisotropy. The unique observation of giant magnetoresistance (GMR) as an intrinsic effect in an evaporated thin film of paramagnetic molecules opens up new possibilities in organic spintronics.
Journals
2014 EN
Aresti Mauro · Saba Michele · Piras Roberto
+12 more
Among solution‐processed nanocrystals containing environmentally benign elements, bismuth sulfide (Bi 2 S 3 ) is a very promising n‐type semiconductor for solar energy conversion. Despite the prompt success in the fabrication of optoelectronic devices deploying Bi 2 S 3 nanocrystals, the limited understanding of electronic properties represents a hurdle for further materials developments. Here, two key materials science issues for light‐energy conversion are addressed: bandgap tunability via the quantum size effect, and photocarrier trapping. Nanocrystals are synthesized with controlled sizes varying from 3 to 30 nm. In this size range, bandgap tunability is found to be very small, a few tens of meV. First principles calculations show that a useful blueshift, in the range of hundreds of meV, is achieved in ultra‐small nanocrystals, below 1.5 nm in size. Similar conclusions are envisaged for the class of pnictide chalcogenides with a ribbon‐like structure [Pn 4 Ch 6 ] n (Pn = Bi, Sb; Ch = S, Se). Time‐resolved differential transmission spectroscopy demonstrates that only photoexcited holes are quickly captured by intragap states. Photoexcitation dynamics are consistent with the scenario emerging in other metal–chalcogenide nanocrystals: traps are created in metal‐rich nanocrystal surfaces by incomplete passivation by long fatty acid ligands. In large nanocrystals, a lower bound to surface trap density of one trap every sixteen Bi 2 S 3 units is found.
Journals
2014 EN
Bussetti Gianlorenzo · Campione Marcello · Riva Michele
+10 more
In an ordered porphyrin molecular array, the tautomerism reaction is frozen at room temperature. In particular, G. Bussetti et al. use the H‐H tautomer alignment as a logic device (1/0 states) on page 958 by perturbing the inner cavity of the molecule. The state flip is readable by an optical probe.
Journals
2014 EN
Benfenati Valentina · Martino Nicola · Antognazza Maria Rosa
+5 more
Astroglial ion channels are fundamental molecular targets in the study of brain physiology and pathophysiology. Novel tools and devices intended for stimulation and control of astrocytes ion channel activity are therefore highly desirable. The study of the interactions between astrocytes and biomaterials is also essential to control and minimize reactive astrogliosis, in view of the development of implantable functional devices. Here, the growth of rat primary neocortical astrocytes on the top of a light sensitive, organic polymer film is reported; by means of patch‐clamp analyses, the effect of the visible light stimulation on membrane conductance is then determined. Photoexcitation of the active material causes a significant depolarization of the astroglial resting membrane potential: the effect is associated to an increase in whole‐cell conductance at negative potentials. The magnitude of the evoked inward current density is proportional to the illumination intensity. Biophysical and pharmacological characterization suggests that the ion channel mediating the photo‐transduction mechanism is a chloride channel, the ClC‐2 channel. These results open interesting perspectives for the selective manipulation of astrocyte bioelectrical activity by non‐invasive, label‐free, organic‐based, photostimulation approaches.
Journals
2014 EN
Benfenati Valentina · Martino Nicola · Antognazza Maria Rosa
+5 more
On page 392, Valentina Benfenati, Maria Rosa Antognazza, Michele Muccini, and colleagues show how the photostimulation of a semiconducting polymer blend modulates the ion channel conductance of astrocytes cultured on top of the device. The device can be used as a selective tool to study ion channel conductances in non‐excitable cells.
Journals
2014 EN
Miele Ermanno · Malerba Mario · Dipalo Michele
+3 more
Tailored hydrophobic and oleophobic surfaces are exploited for controlling the wetting behaviour and evaporation process of solution dropped on them. This enables molecules and nano‐objects that are dissolved in water or organic solvents to be delivered and arranged in a well‐defined 2D layout.
Journals
2014 EN
Sessolo Michele · Rivnay Jonathan · Bandiello Enrico
+2 more
Ion‐selective organic electrochemical transistors with sensitivity to potassium approaching 50 μA dec −1 are demonstrated. The remarkable sensitivity arises from the use of high transconductance devices, where the conducting polymer is in direct contact with a reference gel electrolyte and integrated with an ion‐selective membrane.