Nanoscale PDA disassembly in ionic liquids: structure-property relationships underpinning redox tuning.

Nanoscale disassembly of mussel-inspired polydopamine (PDA) in ionic liquids (ILs) was recently shown to induce an electron paramagnetic resonance (EPR)-detectable reorganization of free radical centers in the resulting nanoparticles (NPs) in an IL-controlled manner. Herein, we report electrical impedance spectroscopy (EIS) data showing that PDA NPs produced by suspending samples obtained in Tris and bicarbonate buffer (PDA-T and PDA-C) in different ILs display different redox activity as a result of structural control combined with IL-surface interactions. In particular, susceptibility to oxidation was found to correlate closely with the spin density in an ion pair-tunable fashion in ILs. Structural control over free radical properties and redox behavior of PDA NPs in ILs opens novel perspectives for the rational design of functional nanovectors of possible interest for drug delivery and theranostic applications.

Role of direct and inverted undoped spiro-OMeTAD-perovskite architectures in determining solar cells performances: an investigation via electrical impedance spectroscopy.

The present study involved an investigation on the reasoning behind the dependence of the perovskite solar cells photovoltaic efficiencies on the relative position of the undoped spiro-OMeTAD hole-transport material with respect to the perovskite in the device. We adopted impedance spectroscopy to investigate the modification of the carrier transport mechanisms across the spiro-OMeTAD/perovskite interface constituting the active part where the main device processes occur. We investigated two interface structures, referred to as the direct (or regular, n-i-p) and the inverted (p-i-n) configuration. This work also intended to further stress the possible adoption of alternative device structures working with undoped hole-transport materials.

Hydration-controlled anisotropic and giant permittivity in TEG-functionalized eumelanin.

Although it has long been known that the peculiar electronic-ionic conductor behavior of eumelanin is critically dependent on hydration, the detailed mechanisms by which water-polymer interactions control and affect the conduction properties have remained largely obscure. In this paper, we report a remarkable anisotropy and giant polarization effect in a synthetic eumelanin (TEGMe) chemically functionalized with hydrophilic TEG residues. FT-IR analyses of water sorption isotherms and AC measurements were consistent with a microporous structure binding or hosting mainly isolated water molecules. In contrast, similar experiments on a commercial synthetic eumelanin (AMe) used as a reference were suggestive of a bulk macroporous scaffold binding or hosting liquid water. These data disclosed for the first time the differential impact on eumelanin conductivity of vapor, liquid and ice-like forms of water adsorbed onto or embedded into the polymer layer. It is thus demonstrated, for the first time, that hydration controls the conduction properties of eumelanin in a more complex manner than is commonly believed, involving, besides the reported semiquinone comproportionation equilibria, the mode of interaction of water molecules as governed by both the chemical and morphological features of the polymer.

Highly Sensitive and Practical Detection of Plant Viruses via Electrical Impedance of Droplets on Textured Silicon-Based Devices.

Early diagnosis of plant virus infections before the disease symptoms appearance may represent a significant benefit in limiting disease spread by a prompt application of appropriate containment steps. We propose a label-free procedure applied on a device structure where the electrical signal transduction is evaluated via impedance spectroscopy techniques. The device consists of a droplet suspension embedding two representative purified plant viruses i.e., Tomato mosaic virus and Turnip yellow mosaic virus, put in contact with a highly hydrophobic plasma textured silicon surface. Results show a high sensitivity of the system towards the virus particles with an interestingly low detection limit, from tens to hundreds of attomolar corresponding to pg/mL of sap, which refers, in the infection time-scale, to a concentration of virus particles in still-symptomless plants. Such a threshold limit, together with an envisaged engineering of an easily manageable device, compared to more sophisticated apparatuses, may contribute in simplifying the in-field plant virus diagnostics.

Morphometrical and Morphological Alterations of Human Leukocytes Exposed to 1.8 GHz Electromagnetic Radiations: In Vitro Protective Effects Induced by Polyphenols.

BACKGROUND: Our recent findings have demonstrated that electromagnetic radiations (EMR) (1.8 GHz radiofrequency) are able to in vitro induce morphometrical and morphological modifications of human leukocytes from normal donors. METHODS: In view of the evidence that polyphenols exert many beneficial effects on plants, animals and humans, leukocytes from human peripheral blood were pre-treated for 1 h with two polyphenol preparations from red grape before EMR exposure (1.8 GHz). RESULTS: Our data will show that polyphenol pre-treatment reverts to normality the morphology of irradiated leukocytes in comparison to irradiated cells only. Conversely, leukocyte morphometry seems to be not affected by this treatment. CONCLUSION: Here, we demonstrate that polyphenols are also able to normalize leukocyte morphology per se altered before as well as after irradiation. Finally, a working hypothesis aimed at clarifying the protective mechanisms exerted by polyphenols on irradiated leukocytes will be illustrated.

Photodetectors based on carbon nanotubes deposited by using a spray technique on semi-insulating gallium arsenide.

In this paper, a spray technique is used to perform low temperature deposition of multi-wall carbon nanotubes on semi-insulating gallium arsenide in order to obtain photodectors. A dispersion of nanotube powder in non-polar 1,2-dichloroethane is used as starting material. The morphological properties of the deposited films has been analysed by means of electron microscopy, in scanning and transmission mode. Detectors with different layouts have been prepared and current-voltage characteristics have been recorded in the dark and under irradiation with light in the range from ultraviolet to near infrared. The device spectral efficiency obtained from the electrical characterization is finally reported and an improvement of the photodetector behavior due to the nanotubes is presented and discussed.

Controlling semiconductor/metal junction barriers by incomplete, nonideal molecular monolayers.

We study how partial monolayers of molecular dipoles at semiconductor/metal interfaces can affect electrical transport across these interfaces, using a series of molecules with systematically varying dipole moment, adsorbed on n-GaAs, prior to Au or Pd metal contact deposition, by indirect evaporation or as "ready-made" pads. From analyses of the molecularly modified surfaces, we find that molecular coverage is poorer on low- than on high-doped n-GaAs. Electrical charge transport across the resulting interfaces was studied by current-voltage-temperature, internal photoemission, and capacitance-voltage measurements. The data were analyzed and compared with numerical simulations of interfaces that present inhomogeneous barriers for electron transport across them. For high-doped GaAs, we confirm that only the former, molecular dipole-dependent barrier is found. Although no clear molecular effects appear to exist with low-doped n-GaAs, those data are well explained by two coexisting barriers for electron transport, one with clear systematic dependence on molecular dipole (molecule-controlled regions) and a constant one (molecule-free regions, pinholes). This explains why directly observable molecular control over the barrier height is found with high-doped GaAs: there, the monolayer pinholes are small enough for their electronic effect not to be felt (they are "pinched off"). We conclude that molecules can control and tailor electronic devices need not form high-quality monolayers, bind chemically to both electrodes, or form multilayers to achieve complete surface coverage. Furthermore, the problem of stability during electron transport is significantly alleviated with molecular control via partial molecule coverage, as most current flows now between, rather than via, the molecules.