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Over the past two decades, the chirality-induced spin selectivity (CISS) effect was reported in several experiments disclosing a unique connection between chirality and electron spin. Recent theoretical works have highlighted time-resolved Electron Paramagnetic Resonance (trEPR) as a powerful tool to directly detect the spin polarisation resulting from CISS. Because of the absence of interfaces with conducting electrodes, such spectroscopic evidence could provide a clear understanding of how CISS works at the intramolecular level. Experimental results have demonstrated the potential of this approach for detecting a spin-polarised photoinduced electron transfer (ET) in hybrid systems comprising a CdSe quantum dot as an electron donor (D) connected by a chiral linker (χ) to a fullerene derivative as an electron acceptor (A). However, the study of the ET process in fully organic D-χ-A dyads holds tremendous potential for the unambiguous detection of CISS. Here, we report a first attempt performed using novel D-χ-A dyads, comprising pyrene (D) and fullerene (A) connected by chiral saturated peptide bridges (χ) of different length and electric dipole moment. The dyads are investigated by an array of techniques, including cyclic voltammetry, optical spectroscopies, and trEPR. Despite the promising energy alignment of the electronic levels and the evidence of luminescence quenching, trEPR does not detect a significant ET highlighting the challenges of spectroscopic detection of CISS. However, the analysis allows the formulation of guidelines for the design of chiral organic model systems suitable to directly probe CISS-polarised ET.

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.TOC

The electronic properties of a charge-transfer (donor-acceptor) semiconducting organic co-crystal, Perylene:F4-TCNQ (PE:F4) (the donor, D, is PE and the acceptor, A, is 2,3,5,6-tetrafluoro-7,7,8,8 tetracyanoquinodimethane (F4)) in its 3 : 2 stoichiometry, are experimentally and theoretically studied. This is performed by means of electron paramagnetic resonance (EPR) and solid state electrochemical techniques, such as cyclic voltammetry (CV) measurements on single crystals. In particular, solid state electrochemistry proves to be an effective tool to probe, on a macroscopic scale, the electronic characteristics of the co-crystal. However, EPR highlights the presence of spin 1/2 radicals localized on F4 molecules, possibly linked to defects. The experimental findings are discussed on the basis of density functional theory (DFT) based calculations, carried out using both the projector augmented wave (PAW), with "periodic boundary conditions" (pbc), method and the localized orbitals, molecular cluster, approach. In particular, a satisfying agreement is found between the experimental, 0.336 eV (electrochemical), and theoretical, 0.303 eV (PAW), band gaps. Differences with the reported optical bandgap are discussed considering excitonic effects.

Controlled reduction of oxygen is important for developing clean energy technologies, such as fuel cells, and is vital to the existence of aerobic organisms. The process starts with oxygen in a triplet ground state and ends with products that are all in singlet states. Hence, spin constraints in the oxygen reduction must be considered. Here, we show that the electron transfer efficiency from chiral electrodes to oxygen (oxygen reduction reaction) is enhanced over that from achiral electrodes. We demonstrate lower overpotentials and higher current densities for chiral catalysts versus achiral ones. This finding holds even for electrodes composed of heavy metals with large spin–orbit coupling. The effect results from the spin selectivity conferred on the electron current by the chiral assemblies, the chiral-induced spin selectivity effect.

The Kane-Maguire polymerization mechanism is disassembled at a molecular level by using DFT-based quantum mechanical calculations. Resorcinol electropolymerization is selected as a case study. Stationary points (transition states and intermediate species) leading to the formation of the dimer are found on the potential energy surface (PES), and elementary reactions involved in the dimer formation are characterized. The latter allow to further propagate the polymerization chain reaction, when applied recursively. In this paper, the fundamental role of the sulfate anion (a typical base electrolyte) is addressed. Investigation of the PES in terms of both stationary-state properties and of ab initio molecular dynamics results (dynamic reaction coordinate) allows the appreciation in detail of the critical role of the base electrolyte anion in making the proton dissociation from the initial radical ion, a feasible (downhill in energy) process.

The role of thiourea as an organic additive in the nucleation and growth mechanism was studied for copper deposition and its application in the decorative electroplating and fashion accessory industries. The bath was designed to reduce the environmental and ecological impacts using methanesulfonic acid as electrolyte as an alternative to alkaline cyanide baths. We evaluated the nucleation and growth mechanism of copper exploiting voltametric and chronoamperometric measurements with a brightener concentration ranging from 0 to 90 ppm. We used the Scharifker–Hills model to estimate the type of nucleation mechanism after progressive addition of thiourea. Scanning electron microscope was employed for surface analysis and morphological characterisation of the nuclei. We verified that progressive nucleation is a key step in the obtainment of a shiny and homogeneous copper film, but an excess of thiourea could cause parasitic adsorption reactions on the surface of the substrate. X-ray fluorescence spectroscopy was used for the thickness determination of the copper deposits and the electrodeposition efficiency correlated to thiourea concentration. Finally, the optimal concentration of thiourea was assessed to be 60 ppm for the used formulation of copper plating.

The ethanol electro-oxidation catalyzed by Pd in an alkaline environment involves several intermediate reaction steps promoted by the hydroxyl radical, OH. In this work, we report on the dynamical paths of the first step of this oxidation reaction, namely the hydrogen atom abstraction CH3CH2OH + OH -> CH3CHOH + H2O, occurring at the Pd(111) surface and address the thermodynamic stability of the adsorbed reactants by means of quantum and molecular mechanics calculations, with special focus on the effect of the solvent. We have found that the impact of the solvent is significant for both ethanol and OH, contributing to a decrease in their adsorption free energies by a few dozen kcal mol-1 with respect to the adsorption energy under vacuum. Furthermore, we observe that hydrogen atom abstraction is enhanced for those simulation paths featuring large surface-reactant distances, namely, when the reactants weakly interact with the catalyst. The picture emerging from our study is therefore that of a catalyst whose coverage in an aqueous environment is largely dominated by OH with respect to ethanol. Nevertheless, only a small amount of them, specifically those weakly bound to the catalyst, is really active in the ethanol electro-oxidation reaction. These results open the idea of a rational design of co-catalysts based on the tuning of surface chemical properties to eventually enhance exchange current density.

This paper studies the mechanism of electrochemically induced carbon–bromine dissociation in 1-Br-2-methylnaphalene in the reduction regime. In particular, the bond dissociation of the relevant radical anion is disassembled at a molecular level, exploiting quantum mechanical calculations including steady-state, equilibrium and dissociation dynamics via dynamic reaction coordinate (DRC) calculations. DRC is a molecular-dynamic-based calculation relying on an ab initio potential surface. This is to achieve a detailed picture of the dissociation process in an elementary molecular detail. From a thermodynamic point of view, all the reaction paths examined are energetically feasible. The obtained results suggest that the carbon halogen bond dissociates following the first electron uptake follow a stepwise mechanism. Indeed, the formation of the bromide anion and an organic radical occurs. The latter reacts to form a binaphthalene intrinsically chiral dimer. This paper is respectfully dedicated to Professors Anny Jutand and Christian Amatore for their outstanding contribution in the field of electrochemical catalysis and electrosynthesis.

We show that enantioselective reactions can be induced by the electron spin itself and that it is possible to replace a conventional enantiopure chemical reagent by spin-polarized electrons that provide the chiral bias for enantioselective reactions. Three examples of enantioselective chemistry resulting from electron-spin polarization are presented. One demonstrates the enantioselective association of a chiral molecule with an achiral self-assembled monolayer film that is spin-polarized, while the other two show that the chiral bias provided by the electron helicity can drive both reduction and oxidation in enantiospecific electrochemical reactions. In each case, the enantioselectivity does not result from enantiospecific interactions of the molecule with the ferromagnetic electrode but from the polarized spin that crosses the interface between the substrate and the molecule. Furthermore, the direction of the electron-spin polarization defines the handedness of the enantioselectivity. This work demonstrates a new mechanism for realizing enantioselective chemistry.

The study of physicochemical processes at chiral surfaces is a particularly intriguing field of science.1,2 Of course, a logical and natural extension is the study of the electrochemical behavior of a “chiral-electrode”|solution interface, which is the subject of rapidly growing scientific and applicative interest in electrochemistry.3–6 In physics (and biology too), the concept of chirality, and the relevant involvement of physical interactions ruling chiral-systems is fascinating field of science: Maxwell equations, light polarization to mention a few (in biology, the homochirality dilemma7). Besides the purely fascinating scientific aspects, in chemistry chirality means a concept able to rule asymmetric synthesis and enantioselectivity/enantio-recognition (sensors). Within the area of chirality, it was shown that chiral systems are able to interact selectively with spin-polarized electrons8 acting also as spin-filter: chiral induced spin-selectivity (CISS).9 As a rational development, the implementation of the chiral spin-selectivity in electrochemistry, lead to the so-called spin-dependent electrochemistry.10 Quite recently where surfaces functionalized with chiral molecules shown better charge transfer properties if compared with structurally similar achiral compounds.11 Moreover, “chiralized” (which means co-deposition with a chiral-inducer compound) electrodeposited nickel and electropolymerized aniline (PANI), showed both good enantioselectivity as well as spin filtering (magnetoresistance measurements) characteristics.12–14 In this paper we want to prepare “chiralized” metals by electroless co-deposition of a suitable metal (here Cu and Ni) with an enantiopure chiral molecule: asymmetry inducer. This aiming to deposit a chiral conductive (metallic and possibly ferromagnetic) surface on a non-conductive material, in view of applications in both energy (photovoltaic) and spintronics (spin-valve) applications. In general, electroless deposition of both Cu and Ni relies on the use of Pd salts (where the real “catalyst” are Pd metallic nanoparticles), this makes the electroless procedure quite expensive. At present, in our laboratory the electroless deposition of both Cu and Ni was successfully carried out using Ag nanoparticles as the catalyzer, Figure 1. Co-deposition in the presence of enantiopure organic compounds is under investigations. References A. J. Gellman, Acc. Mater. Res., 2, 1024–1032 (2021). D. Avnir, Advanced Materials, 30, 1706804 (2018). C. Wattanakit et al., Nature Communications, 5, ncomms4325 (2014). H. Moshe et al., Chem. Eur. J., 19, 10295–10301 (2013). H. Moshe, G. Levi, D. Sharon, and Y. Mastai, Surface Science, 629, 88–93 (2014). S. Arnaboldi, M. Magni, and P. R. Mussini, Current Opinion in Electrochemistry, 8, 60–72 (2018). G. Laurent, D. Lacoste, and P. Gaspard, PNAS, 118 (2021) https://www.pnas.org/content/118/3/e2012741118. S. Mayer, C. Nolting, and J. Kessler, J. Phys. B: At. Mol. Opt. Phys., 29, 3497–3511 (1996). K. Ray, S. P. Ananthavel, D. H. Waldeck, and R. Naaman, Science, 283, 814–816 (1999). D. Mishra et al., Proceedings of the National Academy of Sciences, 110, 14872–14876 (2013). M. Innocenti et al., Journal of Electroanalytical Chemistry, 856, 113705 (2020). M. Gazzotti et al., Electrochimica Acta, 286, 271–278 (2018). S. Mishra et al., Small Methods, 4, 2070038 (2020). S. Mishra, L. Pasquali, and C. Fontanesi, Appl. Phys. Lett., 118, 224001 (2021). Figure 1

This work summarizes state-of-the-art results achieved by combining, in a synergetic approach, the outcome obtained by electrochemical, spectroscopic and theoretical methods. A number of selected case-studies are reported, where such a synergetic approach enables to draw a complete picture of complex experimental systems. Finally, the relevance of the combined experimental and theoretical approach in solid-state electrochemistry, a territory amidst novel concepts in solidstate electronics, is recapped.

Oxygen Reduction Reaction (ORR) is the bottle-neck strategic reaction ruling the fuel cell efficiency process. The slow kinetics of the reaction require highly effective electrocatalysts for proper boosting. In this field, composite catalysts formed by carbon nanotubes functionalized with palladium(II) complexes showed surprising catalytic activity comparable to those of a commercial Pt electrode, but the catalytic mechanisms of these materials still remain open to discussion. In this paper, we propose the combination of experimental and theoretical results to unfold the elementary reaction steps underlying the ORR catalysis.

Enantiospecific crystallization of the three amino acids asparagine (Asn), glutamic acid hydrochloride (Glu·HCl) and threonine (Thr), induced by ferromagnetic (FM) substrates, is reported., Enantiospecific crystallization of the three amino acids asparagine (Asn), glutamic acid hydrochloride (Glu·HCl) and threonine (Thr), induced by ferromagnetic (FM) substrates, is reported. The FM substrates were prepared by evaporating nickel capped with a thin gold layer on standard silicon wafers. Magnets were positioned underneath the substrate with either their North (N) or South (S) poles pointing up. Asymmetric induction, controlled by the magnetic substrates, was demonstrated for the crystallization of the pure enantiomers and was then extended for the racemic mixtures of Asn and Glu·HCl. In the case of the solution of the pure enantiomers, the l enantiomer was crystallized preferentially at one pole of the magnet and the d enantiomer at the other. Consequently, the racemates of Asn and Glu·HCl undergo separation under the influence of the magnetic substrate. With Thr, however, despite the enantiospecific interactions of the pure enantiomers with the FM, no separation of the emerging crystals could be achieved with the racemates, although they crystallize as conglomerates, implying differences taking place in the crystallization step. The results reported here are not directly related to the magnetic field, but rather to the aligned spins within the ferromagnets. The findings provide a novel method for resolving enantiomers by crystallization and offer a new perspective for a possible role played by magnetic substrates regarding the origin of chirality in nature.

Redox potential modulation of achiral probes on chirally modified electrode surfaces with spin filter features under an applied magnetic field., Impressive spin-related effects are observed in cyclic voltammetry (CV) experiments performed under an applied magnetic field on a non-ferromagnetic electrode modified with a thin electroactive oligothiophene film, either “inherently chiral” or featuring chiral pendants with stereogenic centres. When flipping the magnet’s north/south orientation, the CV peaks of two achiral, chemically reversible Fe(iii)/Fe(ii) redox couples in aqueous or organic solution undergo impressive potential shifts (up to nearly 0.5 V depending on protocol conditions), specularly by changing the film’s (R)- or (S)-configuration. The magnitude of the potential shift decreases upon increasing both the polymer film thickness and the distance between the permanent magnet and the electrode surface. Such unprecedented spin-related redox potential modulation, obtained in the absence of a magnetic electrode acting as a spin injector, provides striking evidence (as well as an attractive evaluation criterion) of the spin selectivity properties of chiral thin films.

The XRF analysis is the most widespread in the industry setting to determine the thickness of metallic coatings, thanks to its ease of use, robustness, and non-destructive nature. However, accurate measurement requires primary standards that are expensive, not always available, and must be periodically replaced due to a limited shelf-life. In this context, we propose a versatile and cost-effective way for measuring the thickness of metallic coatings. Our method relies on a calibration curve based upon self-produced standards made through electroplating process and measured by a cross-sectional microscopy observation, either by SEM or light microscope. Thickness distribution was sufficiently homogeneous to be consistent with certified standard specifications: 5% of thickness variation in the central portion of the coatings (1 cm2) could be achieved for cathode length starting from 5 cm. Moreover, thickness distribution can be quantitatively predicted, relying only on primary current simulations, almost on simple shaped objects. The self-produced standard fit the calibration curve with a R2 > 0.999. Comparing different XRF quantitative methods with Student's t-test, we demonstrated that the proposed protocol is as effective as certified standards-based methods in terms of accuracy but at significantly lower costs.

This study focuses on the influence of an applied external magnetic field on the electrodeposition process and capacitive performances of MnO2, as pseudo-capacitive active material for supercapacitors electrodes. MnO2 was electrochemically deposited on Si/Au substrates in the presence and in the absence of a 0.5 T magnet, and its capacitive performance was tested via electrochemical characterization. The samples obtained in the presence of the magnetic field show a positive influence on the deposition process: the increase in deposition efficiency leads to more compact and uniform MnO2 coatings, with a decrease in capacitance values for the samples produced with the magnetic field.

The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure., A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene.

Charge-transfer crystals exhibit unique electronic and magnetic properties with interesting applications. The charge-transfer single crystal formed by dibenzotetrathiafulvalene (DBTTF) together wit...

The influence of polyethyleneimine (PEI) as additive for cyanide-free silver bath, in combination with 5,5-dimethylhydantoin (DMH) as complexing agent, is studied. Cyclic voltammetry (CV) measurements are used to characterize the electrochemical behaviour of the Ag/DMH complex. The Ag electrodeposition from the cyanide-free silver-plating bath is analysed by CVs and the process is optimized varying the PEI concentration. Chronoamperometry is then used to investigate the electrodeposition mechanism, which is found to be a three-dimensional diffusion-controlled nucleation and growth mechanism, according to the Scharifker-Mostany's model. Smoother, brighter and blue coloured silver deposits are obtained in the presence of PEI in a Hull's cell test, at low density current. Eventually, the influence of nitrate anion is also investigated. The presence of nitrate increases the range of current density allowing for an effective Ag deposition.

The efficiency of charge transmission in chiral compared to achiral molecular systems, of structurally related compounds, is probed via cyclic voltammetry measurements. For such a purpose five different thiols have been selected two achiral (i.e. 3-mercaptopropionic acid (MPA) and 8-mercapto-1-octanol (M8O)) and three chiral (i.e. L- and D-cysteine (Lcys, Dcys) and D-penicillamine (Dpen)). These compounds are used to form 2D self-assembled monolayers (SAM) on gold. Cyclic voltammetry (CV) measurements, by using the potassium hexacyanoferrate(III)/potassium hexacyanoferrate(II) redox couple (Fe3Fe2), are exploited to probe the charge transfer ability of the electrode|SAM|solution interface. In particular, MPA, Lcys and Dpen compounds are selected due to their quite similar structural and geometrical characteristics (virtually the same molecular length and terminal groups). M8O is a longer SAM forming thiol, which was selected as a reference blocking electrode compound. The comparison of the cyclic voltammetry data shows that a better ability in the charge transmission is obtained when chiral SAM are used; namely in the case of L-cysteine and D-penicillamine. This result can be related to the spin filtering ability of chiral compounds: chiral induced spin selectivity (CISS) effect. As rationalized on the basis of theoretical values of optical rotation (OR), calculated at the CAMB3LYP/6-31G(d,p) level of the theory.

In this work, the electrodeposition of smooth bismuth thin films was investigated. Bismuth is known for its peculiar magnetic, thermal and electrical properties but the deposition of a uniform and flat film, which are features required for its application in electronic devices, is not trivial. We investigated the morphology of Bi film electrodeposited at increasing overpotential on a monocrystalline silver electrode. We found that the presence of an underpotential deposition (UPD) layer, previously deposited on the surface, drives the overpotential deposition to a smoother growth. The samples were investigated by means of different techniques: atomic force microscopy (AFM) and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDS) to study the morphology, X-ray photoemission spectroscopy (XPS) to assess the composition and X-ray diffraction spectroscopy (XRD) to check the crystallinity. We also found an unexpected form birefringence behaviour, which has been preliminary investigated with cross polarized light microscopy (CPL).

Results are presented concerning the influence on the water splitting process of enantiopure tartaric acid present in bulk solution. Stainless steel and electrodeposited nickel are used as working electrode (WE) surface. The latter is obtained by electrodeposition on the two poles of a magnet. The influence and role played by the chiral compound in solution has been assessed by comparing the current values, in cyclic voltammetry (CV) experiments, recorded in the potential range at which oxygen evolution reaction (OER) occurs. In the case of tartaric acid and nickel WE a spin polarization of about 4 % is found. The use of the chiral environment (bulk solution) and ferromagnetic chiral Ni electrode allows for observing the OER at a more favourable potential: about 50 mV (i.e. a cathodic, less positive, shift of the potential at which the oxygen evolution is observed).

The energy hierarchy, of the main chemical species involved in the reaction mechanism relevant to the electrodeposition of aluminum in 1-Butyl-3-methylimidazolium chloride/aluminum trichloride solution (BMImCl/AlCl3), is studied by using ab-initio based theoretical calculations. Eventually, a reasonable theoretical estimate of energies, involved in the principal reactions ruling the aluminum electrodeposition from BMImCl ionic liquid solutions, is obtained. For screening purposes (geometry optimization and Hessian calculations) the CAMB3LYP density functional, DFT, has been used. Then single point (exploiting CAMB3LYP optimized geometries) energy data are obtained at the Møller-Plesset (MP2) level of the theory. They are used to cross-check DFT results. A reaction mechanism emerges in which, although the species AlCl-4 is formed with very high efficiency from the neutral species AlCl3, the competing reaction points to an almost complete conversion of aluminum to the dimeric form into bulk solution. This is observed in the absence and, most importantly, in the presence of a coordinating BMIm+ cation. In this respect, the presence of BMIm+ does not seem to affect significantly the equilibrium between the monomeric and dimeric forms of aluminum. This outcome is very interesting because the dimeric species is directly reduced to yield the metal aluminum. Indeed, a larger concentration of Al2Cl-7 gives due reason for a more effective electrodeposition process, as it is experimentally observed in the ionic liquid medium.