Assessing the evolution of oxygenated functional groups on the graphene oxide surface upon mild thermal annealing in water.

Graphene oxide (GO) is known to be a 2D metastable nanomaterial that can be reconstructed under thermal annealing into distinct oxidized and graphitic phases. Up to now, such phase transformation, mainly related to epoxide and hydroxyl functional groups, has been usually achieved by thermally treating layers of GO in the solid state. Here, we present the mild annealing of GO dispersed in an aqueous medium, performed at two temperatures, 50 °C and 80 °C, for different intervals of time.

Self-Assembling Peptide-Based Magnetogels for the Removal of Heavy Metals from Water.

In this study, we present the synthesis of a novel peptide-based magnetogel obtained through the encapsulation of γ-FeO-polyacrylic acid (PAA) nanoparticles (γ-FeONPs) into a hydrogel matrix, used for enhancing the ability of the hydrogel to remove Cr(III), Co(II), and Ni(II) pollutants from water. Fmoc-Phe (-Phenylalanine) and diphenylalanine (Phe) were used as starting reagents for the hydrogelator (Fmoc-Phe) synthesis via an enzymatic method. The PAA-coated magnetic nanoparticles were synthesized in a separate step, using the co-precipitation method, and encapsulated into the peptide-based hydrogel.

Femtosecond laser-induced nano- and microstructuring of Cu electrodes for CO electroreduction in acetonitrile medium.

The dependency of CO reduction rate in acetonitrile-BuNClO solution on cathodes, which were modified by laser induction of a copper surface, was studied. The topography of laser-induced periodic surface structures (LIPSS) → grooves → spikes was successively formed by a certain number of pulses. It was proved that for a higher number of laser pulses, the surface area of the copper cathode increases and preferred platy orientation of the copper surface on [022] crystallografic direction and larger fluence values increase.

One-pot carboxyl enrichment fosters water-dispersibility of reduced graphene oxide: a combined experimental and theoretical assessment.

Graphene, one of the allotropic forms of carbon, has attracted enormous interest in the last few years due to its unique properties. Reduced graphene oxide (RGO) is known as the nanomaterial most similar to graphene in terms of electronic, chemical, mechanical, and optical properties. It is prepared from graphene oxide (GO) in the presence of different types of reducing agents.

Self-Healing and Reprocessable Oleic Acid-Based Elastomer with Dynamic S-S Bonds as Solvent-Free Reusable Adhesive on Copper Surface.

In the last decade, the application of dynamic covalent chemistry in the field of polymeric materials has become the subject of an increasing number of studies, gaining applicative relevance. This is due to the fact that polymers containing dynamic functions possess a structure that affords reprocessability, recyclability and peculiar self-healing properties inconceivable for "classic" polymer networks. Consequently, the synthesis of a dynamic covalent chemistry-based polymer and its chemical, thermal, and mechanical characterizations are reported in the present research.

Green In Situ Synthesis of Silver Nanoparticles-Peptide Hydrogel Composites: Investigation of Their Antibacterial Activities.

The present paper investigated the synthesis of peptide-based hydrogel composites containing photo-generated silver nanoparticles (AgNPs) obtained in the presence and absence of honey as tensile strength enhancer and hydrogel stabilizer. Fmoc-Phe and diphenylalanine (Phe) were used as starting reagents for the hydrogelator synthesis via an enzymatic method. In particular, we developed an in situ one-pot approach for preparing AgNPs inside peptide hydrogels using a photochemical synthesis, without any toxic reducing agents, with reaction yields up to 30%.

Effect of Electrolytic Medium on the Electrochemical Reduction of Graphene Oxide on Si(111) as Probed by XPS.

The wafer-scale integration of graphene is of great importance in view of its numerous applications proposed or underway. A good graphene-silicon interface requires the fine control of several parameters and may turn into a high-cost material, suitable for the most advanced applications. Procedures that can be of great use for a wide range of applications are already available, but others are to be found, in order to modulate the offer of different types of materials, at different levels of sophistication and use.

Progress, highlights and perspectives on NiO in perovskite photovoltaics.

The power conversion efficiency (PCE) of NiO based perovskite solar cells has recently hit a record 22.1% with a hybrid organic-inorganic perovskite composition and a PCE above 15% in a fully inorganic configuration was achieved. Moreover, NiO processing is a mature technology, with different industrially attractive processes demonstrated in the last few years.

Adsorption Dynamics of Redox Active Species onto Polarized Surfaces of Sensitized NiO.

Mesoporous NiO films were deposited by means of a screen printing technique onto fluorine-doped tin oxide transparent electrodes and consequently sensitized with Erythrosin B (EryB) dye. The obtained colored NiO material was used as a working electrode in a three-electrode cell to study the evolution of the triple semiconductor/dye/electrolyte interface upon electrochemical polarization in dark conditions. The electrolyte was a solution of I /I in acetonitrile, with the redox couple representing the typical redox shuttle of dye-sensitized solar cells (DSCs).

Biocompatible N-acetyl cysteine reduces graphene oxide and persists at the surface as a green radical scavenger.

We demonstrate that N-acetyl cysteine (NAC) reduces graphene oxide (GO) at room temperature. This represents a new green method to produce reduced GO (rGO). NAC adheres to the rGO surface as demonstrated by several spectroscopy techniques and avoids GO-mediated oxidation of glutathione.

Noticeable Role of TFSI Anion in the Carbon Cathode Degradation of Li-O Cells.

In this work we address the phenomena at the basis of the performance loss in a Li-O cell operating in the presence of a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/tetraethylene glycol dimethyl ether (TEGDME) salt/solvent couple and a porous carbonaceous cathode. The cell was discharged/charged applying both voltage and capacity limits, and the effects of repeated galvanostatic cycling were addressed. The ex situ characterization of carbonaceous cathodes corresponding to different cutoff voltages was based on vibrational spectroscopies, transmission electron microscopy, and X-ray photoelectron spectroscopy.

Adsorption Behavior of I and I Ions at a Nanoporous NiO/Acetonitrile Interface Studied by X-ray Photoelectron Spectroscopy.

The adsorption of I and I anions, i.e., the two species constituting the most common redox couple of dye-sensitized solar cells (DSCs), onto the surface of screen-printed nanoporous NiO was studied by means of X-ray photoelectron spectroscopy (XPS).

1,2-Dimethoxyethane Degradation Thermodynamics in Li-O Redox Environments.

The reaction thermodynamics of the 1,2-dimethoxyethane (DME), a model solvent molecule commonly used in electrolytes for Li-O rechargeable batteries, has been studied by first-principles methods to predict its degradation processes in highly oxidizing environments. In particular, the reactivity of DME towards the superoxide anion O in oxygen-poor or oxygen-rich environments is studied by density functional calculations. Solvation effects are considered by employing a self-consistent reaction field in a continuum solvation model.

Calix[4]arene-Functionalised Silver Nanoparticles as Hosts for Pyridinium-Loaded Gold Nanoparticles as Guests.

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1-dodecanethiol and 1-(11-mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω-alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X-ray photoelectron spectroscopy (XPS).

Surface Reactivity of a Carbonaceous Cathode in a Lithium Triflate/Ether Electrolyte-Based Li-O2 Cell.

Li-O2 batteries are currently one of the most advanced and challenging electrochemical systems with the potential to largely overcome the performances of any existing technology for energy storage and conversion. However, these optimistic expectations are frustrated by the still inadequate understanding of the fundamentals of the electrochemical/chemical reactions occurring at the cathode side, as well as within the electrolyte and at the three-phase interface. In this work, we illustrate the evolution of the morphology and composition of a carbonaceous cathode in the first discharge/charge in a Li-O2 cell with an ether-based electrolyte by X-ray photoemission spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy.

Probing the redox states at the surface of electroactive nanoporous NiO thin films.

Nanoporous NiO thin film electrodes were obtained via plasma-assisted microwave sintering and characterized by means of a combination of electrochemical techniques and X-ray photoelectron spectroscopy (XPS). The aim of this study is the elucidation of the nature of the surface changes introduced by the redox processes of this nanostructured material. NiO undergoes two distinct electrochemical processes of oxidation in aqueous electrolyte with the progress of NiO anodic polarization.

Assembly of gold nanoparticles on functionalized Si(100) surfaces through pseudorotaxane formation.

The assembly of gold nanoparticles (AuNPs) on a hydrogenated Si(100) surface, mediated by a series of hierarchical and reversible complexation processes, is reported. The proposed multi-step sequence involves a redox-active ditopic guest and suitable calix[n]arene-based hosts, used as functional organic monolayers of the two inorganic components. Surface reactions and controlled release of AuNPs have been monitored by application of XPS, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM) and electrochemistry.

Copper protection by self-assembled monolayers of aromatic thiols in alkaline solutions.

Copper corrosion in alkaline solutions is inhibited by the formation of self-assembled monolayers of aromatic thiols, made of either benzenethiol or 2-naphthalenethiol or 4-acetamidothiophenol. Electrochemical experiments, based on voltammetry and impedance spectroscopy, point out the much lower reactivity of copper surfaces towards oxidation, when covered by compact adlayers of the above molecules bonded through the S atom. The peculiar shape and peak position in the voltammetric reduction of residual oxides grown on modified metal surfaces suggest that they are due to Cu(I) suboxides, probably grown on reactive metal defects.

Electron-transfer processes in metal-free tetraferrocenylporphyrin. Understanding internal interactions to access mixed-valence States potentially useful for quantum cellular automata.

Redox properties of H(2)TFcP [TFcP(2-) = 5,10,15,20-tetraferrocenylporphyrin(2-)] were investigated using cyclic voltammetry, differential pulse voltammetry, and square-wave voltammetry methods in a large variety of solvents and electrolytes. When DMF, THF, and MeCN were used with TBAP as the supporting electrolyte, the first oxidation wave was assigned to a single four-electron oxidation process reflecting simultaneous oxidation of all iron(II) centers into iron(III) centers in H(2)TFcP. When an o-DCB (1,2-dichlorobenzene)/TBAP combination was used in electrochemical experiments, four ferrocene substituents underwent two very diffuse, "two-electron" stepwise oxidations.

Metal-free and transition-metal tetraferrocenylporphyrins part 1: synthesis, characterization, electronic structure, and conformational flexibility of neutral compounds.

H(2)TFcP [TFcP = 5,10,15,20-tetraferrocenyl porphyrin(2-)] was prepared by a direct tetramerization reaction between pyrrole and ferrocene carbaldehyde in the presence of a BF(3) catalyst, while the series of MTFcP (M = Zn, Ni, Co and Cu) were prepared by a metallation reaction between H(2)TFcP and respective metal acetates. All compounds were characterized by UV-vis and MCD spectroscopy, APCI MS and MS/MS methods, high-resolution ESI MS and XPS spectroscopy. Diamagnetic compounds were additionally characterized using (1)H and (13)C NMR methods, while the presence of low-spin iron(ii) centers in the neutral compounds was confirmed by Mössbauer spectroscopy and by analysis of the XPS Fe 2p peaks, revealing equivalent Fe sites.

Electrochemical reversibility of vinylferrocene monolayers covalently attached on H-terminated p-Si(100).

A reversible electrochemical behavior is demonstrated on a specially prepared redox-functionalized H-Si(100) surface, obtained via an extra-mild grafting procedure from vinylferrocene. The results of a detailed XPS and electrochemical characterization of the resulting hybrid are reported and discussed to propose it as a reference system for high-quality electroactive monolayers on Si. The investigated ferrocene derivative bears a functional group suitable for a mild route to covalent anchoring on Si, which is based on a photoinduced reaction with visible light under an inert atmosphere.