Spin control using chiral templated nickel

This Letter reports an original spin valve device that is based on a chiral templated nickel material. Chirality in Ni is induced by exploiting co-electrodeposition of an organic chiral template. In this specific case, the chiral templating is enantiopure tartaric acid (TA). Facile electrodeposition (co-deposition) in ambient conditions produces a nickel chiral-templated material. Z-shaped magnetoresistance curves, switching sign as a function of TA handedness, prove the peculiar ferromagnetic character induced by the presence of a chiral compound. Synchrotron measurements using circular polarized light, x-ray natural circular dichroism, confirm the chirality of the Ni in the TA/Ni composite. Density functional theory calculation proves the existence of a strong electronic delocalization involving the tartaric acid and Ni. The significant finding of this Letter is that chiral templated Ni paves the way for future spin valve, which will be able to control the spin without an external magnetic field (as indeed foreseen within the chiral induced spin selectivity-effect framework)

Chiral Magneto-Electrochemistry

Magneto-electrochemistry (MEC) is a unique paradigm in science, where electrochemical experiments are carried out as a function of an applied magnetic field, creating a new horizon of potential scientific interest and technological applications. Over time, detailed understanding of this research domain was developed to identify and rationalize the possible effects exerted by a magnetic field on the various microscopic processes occurring in an electrochemical system. Notably, until a few years ago, the role of spin was not taken into account in the field of magneto-electrochemistry. Remarkably, recent experimental studies reveal that electron transmission through chiral molecules is spin selective and this effect has been referred to as the chiral-induced spin selectivity (CISS) effect. Spin-dependent electrochemistry originates from the implementation of the CISS effect in electrochemistry, where the magnetic field is used to obtain spin-polarized currents (using ferromagnetic electrodes) or, conversely, a magnetic field is obtained as the result of spin accumulation

Ferrocene Molecular Architectures Grafted on Si(111): A Theoretical Calculation of the Standard Oxidation Potentials and Electron Transfer Rate Constant

The standard oxidation potential and the electron transfer (ET) rate constants of two silicon-based hybrid interfaces, Si(111)/organic-spacer/Ferrocene, are theoretically calculated and assessed. The dynamics of the electrochemical driven ET process is modeled in terms of the classical donor/acceptor scheme within the framework of Marcus theory. The ET rate constants, k(ET), are determined following calculation of the electron transfer matrix element, V-RP, together with the knowledge of the energy of the neutral and charge separated systems. The recently introduced Constrained Density Functional Theory (CDFT) method is exploited to optimize the structure and determine the energy of the charge separated species. Calculated ET rate constants are k(ET) = 77.8s(-1) and k(ET) = 1.3 x 10(-9) s(-1), in the case of the short and long organic-spacer, respectively

Effect of Anesthesia Gases on the Oxygen Reduction Reaction

: The oxygen reduction reaction (ORR) is of high importance, among others, because of its role in cellular respiration and in the operation of fuel cells. Recently, a possible relation between respiration and general anesthesia has been found. This work aims to explore whether anesthesia related gases affect the ORR. In ORR, oxygen which is in its triplet ground state is reduced to form products that are all in the singlet state. While this process is "in principle" forbidden because of spin conservation, it is known that if the electrons transferred in the ORR are spin-polarized, the reaction occurs efficiently. Here we show, in electrochemical experiments, that the efficiency of the oxygen reduction is reduced by the presence of general anesthetics in solution. We suggest that a spin-orbit coupling to the anesthetics depolarizes the spins. This causes both a reduction in reaction efficiency and a change in the reaction products. The findings may point to a possible relation between ORR efficiency and anesthetic action

An Integrated Experimental/Theoretical Study of Structurally Related Poly-Thiophenes Used in Photovoltaic Systems

In this work, a series of eight thiophene-based polymers (exploited as “donors” in bulk heterojunction photovoltaics cells), whose structures were designed to be suitably tuned with the electronic characteristics of the [6,6]-Phenyl C61 butyric acid methyl ester (PCBM), is considered,. The electronic properties of the mono-, di-, trimeric oligomers are reckoned (at the Hartree-Fock and DFT level of the theory) and compared to experimental spectroscopic and electrochemical results. Indeed, electrochemical and spectroscopic results show a systematic difference whose physical nature is assessed and related to the exciton (electron-hole) binding energy (Je,h). The critical comparison of the experimental and theoretical band gaps, i.e., the HOMO-LUMO energy difference, suggests that electrochemical and DFT values are the most suited to being used in the design of a polythiophene-based p-n junction for photovoltaics

Control of polymorphism in coronene by the application of magnetic fields

Coronene, a polyaromatic hydrocarbon, has been crystallized for the first time in a different polymorph using a crystal growth method that utilizes magnetic fields to access a unit cell configuration that was hitherto unknown. Crystals grown in magnetic field of 1 T are larger, have a different appearance to those grown in zero field and retain their structure in ambient conditions. We identify the new form, beta-coronene, as the most stable at low temperatures. As a result of the new supramolecular configuration we report significantly altered electronic, optical and mechanical properties.Comment: 32 pages, 17 figure

Growth Dynamics of Ultrathin Films of Benzo[1,2-b:4,5-b']dithiophene Derivatives on Au(111): A Photoelectron Spectroscopy Investigation

: Ultrathin films of a stereoisomeric mixture of benzo[1,2-b:4,5-b']dithiophene derivatives were grown by thermal evaporation in vacuum on Au(111), and they were studied in situ by photoelectron spectroscopy. X-ray photons from a non-monochromatic Mg Kα conventional X-ray source and UV photons from a He I discharge lamp equipped with a linear polarizer were used. He I photoemission results were compared with density functional theory (DFT) calculations: density of states (DOS) and 3D molecular orbital density distribution. Au 4f, C 1s, O 1s, and S 2p core-level components suggest a surface rearrangement as a function of film nominal thickness, with the variation of the molecular orientation, from flat-laying at the initial deposition to tilted toward the surface normal at coverages exceeding 2 nm. Eventually, the DFT results were exploited in assigning of the valence band experimental structures. Moreover, polarization-dependent photoemission confirmed the tilted arrangement of the molecules, starting at 2 nm. A variation of the work function of 1.4 eV with respect to the clean substrate was measured, together with a valence band offset of 1.3 eV between the organic layer and gold

Exploiting the Combination of Displacement and Chemical Plating for a Tailored Electroless Deposition of Palladium Films on Copper

Various formulations for electroless deposition, to obtain continuous nanometre-sized and micrometre-sized films of palladium on copper, were compared. We deposited ultrathin films using displacement plating formulations. We obtained continuous films with an equivalent thickness between 6 and 22 nm, measured by exploiting the K-ratio method with SEM-EDS of Pd layers. The Pd films obtained in this step of the work represent a cost-effective catalytic substrate. As a second step, we selected chemical plating as the procedure to obtain palladium films with a thickness in the micrometre range. An ammonia-based Pd chemical plating bath represent one of the most effective chemical plating formulations. To prevent copper substrates from being damaged by ammonia, displacement plating with palladium was also applied as a pre-treatment to make the use of these plating baths a viable way to obtain thicker palladium coatings. Palladium films showing good adherence, compact morphology, and a thickness over 1.5 µm were obtained, proving that the combination of two different electroless techniques was the key to develop a sustainable procedure for micrometre-sized palladium coatings, which could substitute electroplating of Pd in galvanic industry for decorative applications

On the Savéant's Concerted/Stepwise Model. The Electroreduction of Halogenated Naphthalene Derivatives as a Case Study

The electroreduction of 1-Br-2-naphthol is shown to be a not-additive process with respect to the results obtained with two structurally related chiral [1,1′-Binaphthalene]-2,2′-diol, 6,6′-dibromo and 1,1′-Binaphthalene,6,6′-dibromo-2,2′-dimethoxy compounds. The 1-Br-2-naphtol reduction is accompanied by the carbon bromine dissociation, eventually producing a film due to a fast radical-radical cross reaction. The film formation is not observed in the BINOL-like chiral halogen-derivatives