(η8-Cyclooctatetraene)(η5-fluorenyl)titanium: a processable molecular spin qubit with optimized control of the molecule-substrate interface.

Depositing single paramagnetic molecules on surfaces for sensing and quantum computing applications requires subtle topological control. To overcome issues that are often encountered with sandwich metal complexes, we exploit here the low symmetry architecture and suitable vaporability of mixed-sandwich [FluTi(cot)], Flu = fluorenyl, cot = cyclooctatetraene, to drive submonolayer coverage and select an adsorption configuration that preserves the spin of molecules deposited on Au(111). Electron paramagnetic resonance spectroscopy and ab initio quantum computation evidence a d z 2 ground state that protects the spin from phonon-induced relaxation. Additionally, computed and measured spin coherence times exceed 10 µs despite the molecules being rich in hydrogen. A thorough submonolayer investigation by scanning tunneling microscopy, X-ray photoelectron and absorption spectrocopies and X-ray magnetic circular dichroism measurements supported by DFT calculations reveals that the most stable configuration, with the fluorenyl in contact with the metal surface, prevents titanium(iii) oxidation and spin delocalization to the surface. This is a necessary condition for single molecular spin qubit addressing on surfaces.

Spin polarized current in chiral organic radical monolayers.

The chirality-induced spin selectivity (CISS) effect is the capability of chiral molecules to act as spin filters, i.e. to selectively sort flowing electrons based on their spin states. The application of this captivating phenomenon holds great promise in the realm of molecular spintronics, where the primary focus lies in advancing technologies based on chiral molecules to regulate the injection and coherence of spin-polarized currents. In this context, we conducted a study to explore the spin filtering capabilities of a monolayer of the thia-bridged triarylamine hetero[4]helicene radical cation chemisorbed on a metallic surface. Magnetic-conductive atomic force microscopy revealed efficient electron spin filtering at exceptionally low potentials. Furthermore, we constructed a spintronic device by incorporating a monolayer of these molecules in between two electrodes, obtaining an asymmetric magnetoresistance trend with signal inversion in accordance with the handedness of the enantiomer involved, indicative of the presence of the CISS effect. Our findings underscore the significance of thia[4]azahelicene organic radicals as promising candidates for the development of quantum information operations based on the CISS effect as a tool to control the molecular spin states.

Assembling Fe4 single-molecule magnets on a TiO2 monolayer.

The decoration of technologically relevant surfaces, such as metal oxides, with Single-Molecule Magnets (SMMs) constitutes a persistent challenge for the integration of these molecular systems into novel technologies and, in particular, for the development of spintronic and quantum devices. We used UHV thermal sublimation to deposit tetrairon(III) propeller-shaped SMMs (Fe4) as a single layer on a TiO2 ultrathin film grown on Cu(001). The properties of the molecular deposit were studied using a multi-technique approach based on standard topographic and spectroscopic measurements, which demonstrated that molecules remain largely intact upon deposition. Ultralow temperature X-ray Absorption Spectroscopy (XAS) with linearly and circularly polarized light was further employed to evaluate both the molecular organization and the magnetic properties of the Fe4 monolayer. X-ray Natural Linear Dichroism (XNLD) and X-ray Magnetic Circular Dichroism (XMCD) showed that molecules in a monolayer display a preferential orientation and an open magnetic hysteresis with pronounced quantum tunnelling steps up to 900 mK. However, unexpected extra features in the XAS and XMCD spectra disclosed a minority fraction of altered molecules, suggesting that the TiO2 film may be chemically non-innocent. The observed persistence of SMM behaviour on a metal oxide thin film opens new possibilities for the development of SMM-based hybrid systems.

On the Electrochemical Growth of a Crystalline p-n Junction From Aqueous Solutions.

Our society largely relies on inorganic semiconductor devices which are, so far, fabricated using expensive and complex processes requiring ultra-high vacuum equipment. Here we report on the possibility of growing a p-n junction taking advantage of electrochemical processes based on the use of aqueous solutions. The growth of the junction has been carried out using the Electrochemical Atomic Layer Deposition (E-ALD) technique, which allowed to sequentially deposit two different semiconductors, CdS and Cu2S, on an Ag(111) substrate, in a single procedure. The growth process was monitored in situ by Surface X-Ray Diffraction (SXRD) and resulted in the fabrication of a thin double-layer structure with a high degree of crystallographic order and a well-defined interface. The high-performance electrical characteristics of the device were analysed ex-situ and show the characteristic feature of a diode.

Efficient Spin-Selective Electron Transport at Low Voltages of Thia-Bridged Triarylamine Hetero[4]helicenes Chemisorbed Monolayer.

The Chirality Induced Spin Selectivity (CISS) effect describes the capability of chiral molecules to act as spin filters discriminating flowing electrons according to their spin state. Within molecular spintronics, efforts are focused on developing chiral-molecule-based technologies to control the injection and coherence of spin-polarized currents. Herein, for this purpose, we study spin selectivity properties of a monolayer of a thioalkyl derivative of a thia-bridged triarylamine hetero[4]helicene chemisorbed on a gold surface. A stacked device assembled by embedding a monolayer of these molecules between ferromagnetic and diamagnetic electrodes exhibits asymmetric magnetoresistance with inversion of the signal according to the handedness of molecules, in line with the presence of the CISS effect. In addition, magnetically conductive atomic force microscopy reveals efficient electron spin filtering even at unusually low potentials. Our results demonstrate that thia[4]heterohelicenes represent key candidates for the development of chiral spintronic devices.

Metal-Free Electrocatalysts for the Selective 2 e- Oxygen Reduction Reaction: A Never-Ending Story?

Hydrogen peroxide (H2 O2 ) electrosynthesis via the 2e- Oxygen Reduction Reaction (ORR) represents a highly challenging, environmentally friendly and cost-effective alternative to the current anthraquinone-based technology. Various lightweight element hetero-doped carbon nanostructures are promising and cheap metal-free electrocatalysts for H2 O2 synthesis, particularly those containing O-functionalities. The exact role of O-containing functional groups as electroactive sites for the process remains debated if not highly controversial. Herein, we have reported on the covalent exohedral functionalization of the outer surface of extra-pure multi-walled carbon nanotubes (MWCNTs) with discrete O-functional groups as a unique approach to prepare selective electrocatalysts for the process. This kind of decoration has added fundamental tiles to the puzzling structure/reactivity relationship of O-containing carbon-based catalysts for ORR, clearing doubts on the controversial role of hydroxyl/phenol groups as key functionalities for the design of more performing 2e- ORR electrocatalysts.

Oxidation of Ethanol to Acetic Acid by Supported PtCu Nanoparticles Stabilized by a Diamine Ligand.

Diamine-capped PtCu nanoparticles have been synthesized by the simultaneous reduction of the corresponding bis-imine metal complexes with hydrogen and supported onto a high-surface-area carbon. The obtained heterogeneous catalyst was tested in thermally conducted aerobic oxidation of ethanol to acetic acid in water as well as in the electrochemical oxidation of ethanol. Both types of catalyses mediated by the PtCu alloy confirmed a notable increase in catalytic activity compared to the pure Pt- and Cu-based counterparts due to a clear bimetallic effect.

Driving up the Electrocatalytic Performance for Carbon Dioxide Conversion through Interface Tuning in Graphene Oxide-Bismuth Oxide Nanocomposites.

The integration of graphene oxide (GO) into nanostructured Bi2O3 electrocatalysts for CO2 reduction (CO2RR) brings up remarkable improvements in terms of performance toward formic acid (HCOOH) production. The GO scaffold is able to facilitate electron transfers toward the active Bi2O3 phase, amending for the high metal oxide (MO) intrinsic electric resistance, resulting in activation of the CO2 with smaller overpotential. Herein, the structure of the GO-MO nanocomposite is tailored according to two synthetic protocols, giving rise to two different nanostructures, one featuring reduced GO (rGO) supporting Bi@Bi2O3 core-shell nanoparticles (NP) and the other GO supporting fully oxidized Bi2O3 NP. The two structures differentiate in terms of electrocatalytic behavior, suggesting the importance of constructing a suitable interface between the nanocarbon and the MO, as well as between MO and metal.

Direct detection of spin polarization in photoinduced charge transfer through a chiral bridge.

It is well assessed that the charge transport through a chiral potential barrier can result in spin-polarized charges. The possibility of driving this process through visible photons holds tremendous potential for several aspects of quantum information science, e.g., the optical control and readout of qubits. In this context, the direct observation of this phenomenon via spin-sensitive spectroscopies is of utmost importance to establish future guidelines to control photo-driven spin selectivity in chiral structures. Here, we provide direct proof that time-resolved electron paramagnetic resonance (EPR) can be used to detect long-lived spin polarization generated by photoinduced charge transfer through a chiral bridge. We propose a system comprising CdSe quantum dots (QDs), as a donor, and C60, as an acceptor, covalently linked through a saturated oligopeptide helical bridge (χ) with a rigid structure of ∼10 Å. Time-resolved EPR spectroscopy shows that the charge transfer in our system results in a C60 radical anion, whose spin polarization maximum is observed at longer times with respect to that of the photogenerated C60 triplet state. Notably, the theoretical modelling of the EPR spectra reveals that the observed features may be compatible with chirality-induced spin selectivity, but the electronic features of the QD do not allow the unambiguous identification of the CISS effect. Nevertheless, we identify which parameters need optimization for unambiguous detection and quantification of the phenomenon. This work lays the basis for the optical generation and direct manipulation of spin polarization induced by chirality.

Unveiling the Role of PEO-Capped TiO2 Nanofiller in Stabilizing the Anode Interface in Lithium Metal Batteries.

Lithium metal batteries (LMBs) will be a breakthrough in automotive applications, but they require the development of next-generation solid-state electrolytes (SSEs) to stabilize the anode interface. Polymer-in-ceramic PEO/TiO2 nanocomposite SSEs show outstanding properties, allowing unprecedented LMBs durability and self-healing capabilities. However, the mechanism underlying the inhibition/delay of dendrite growth is not well understood. In fact, the inorganic phase could act as both a chemical and a mechanical barrier to dendrite propagation. Combining advanced in situ and ex situ experimental techniques, we demonstrate that oligo(ethylene oxide)-capped TiO2, although chemically inert toward lithium metal, imparts SSE with mechanical and dynamical properties particularly favorable for application. The self-healing characteristics are due to the interplay between mechanical robustness and high local polymer mobility which promotes the disruption of the electric continuity of the lithium dendrites (razor effect).