Transient electrochemistry: beyond simply temporal resolution:

Some physicochem. intrigues for which transient electrochem. was necessary to solve the problem are summarized in this feature article. First, we highlight the main constraints to be aware of to access to low time scales, and particularly focus on the effects of stray capacitances. Then, the electron transfer rate const. measured for redox mols. in a self-assembled monolayer configuration is compared to the conductance measured through the same systems, but at the single mol. level. This evidences strong conformational changes when mols. are trapped in the nanogap created between both electrodes. We also report about dendrimers, for which a short electrochem. perturbation induces creation of a diffusion layer within the mol., allowing the electron hopping rate to be measured and analyzed in terms of mol. motions of the redox centers. Finally, we show that transient electrochem. provides also useful information when coupled to other methodologies. For example, when an ultrasonic field drives very fast movements of a bubble situated above the electrode surface, the motion can be dectected indirectly through a modification of the diffusion flux. Another field concerns pulse radiolysis, and we describe how the reactivity (at the electrode or within the soln.) of radicals created by a radiolytic pulse can be quantified, widening the possibilities of electrochem. to operate in biol. media

Controlling the stereochemistry and regularity of butanethiol self-assembled monolayers on Au(111)

© 2014 American Chemical Society. The rich stereochemistry of the self-assembled monolayers (SAMs) of four butanethiols on Au(111) is described, the SAMs containing up to 12 individual C, S, or Au chiral centers per surface unit cell. This is facilitated by synthesis of enantiomerically pure 2-butanethiol (the smallest unsubstituted chiral alkanethiol), followed by in situ scanning tunneling microscopy (STM) imaging combined with density functional theory molecular dynamics STM image simulations. Even though butanethiol SAMs manifest strong headgroup interactions, steric interactions are shown to dominate SAM structure and chirality. Indeed, steric interactions are shown to dictate the nature of the headgroup itself, whether it takes on the adatom-bound motif RS•Au(0)S•R or involves direct binding of RS• to face-centered-cubic or hexagonal-close-packed sites. Binding as RS• produces large, organizationally chiral domains even when R is achiral, while adatom binding leads to rectangular plane groups that suppress long-range expression of chirality. Binding as RS• also inhibits the pitting intrinsically associated with adatom binding, desirably producing more regularly structured SAMs

In-situ x-ray diffraction studies of electrochemical interfaces

A major objective of the work presented in this thesis has been the improvement of in-situ X-ray diffraction procedures to the stage that they can provide a surface sensitive technique for the investigation of a variety of electrochemical interfacial systems. Comparisons are made in a brief overview between this in-situ X-ray diffraction technique and other techniques applicable to the investigation of electrochemical interfaces. The methodology for the in-situ X-ray diffraction (INSEX) experiments is then given, particular attention being drawn to electrode surface preparation, cell design and detection system maintenance. INSEX has been applied to monitor the structural changes in diverse systems: the ordering of thallium and thallium iodide monolayers in the underpotential deposition region of the Tl+/Ag and TlI/Ag systems; the reconstruction of platinized surfaces induced by hydrogen and carbon monoxide adsorption and structure loss of Pt surfaces in the double layer region and due to the formation of oxide films; structural changes of polyaniline films undergoing oxidation/reduction cycles between the leucoemeraldine and emeraldine forms. The diffraction information from the systems is assessed qualitatively by comparing the diffractograms with diffraction intensities calculated from the equation derived for scattering from monolayer structures. (D80427)</p

In-situ STM and AFM Studies on Electrochemical Interfaces in imidazolium-based ionic liquids

Voltammetric responses, adsorption behaviors and layered structures of 1-ethyl-2, 3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (EMMITFSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) at Au (111) have been investigated by cyclic voltammetry, in-situ STM and in-situ AFM force curve measurements, respectively. Cyclic voltammetry measurements pointed out that two pairs of sharp redox peaks are located at around 0.1 and 0.7 V in EMMITFSI, but not in EMITFSI. In-situ STM studies revealed no etching of the Au (111) surface in the investigated potential region in EMMITFSI, but an etched Au (111) surface was observed in EMITFSI in the same potential region, indicating that the interaction between EMITFSI and the Au (111) surface is much stronger than that between EMMITFSI and the Au (111) surface. In-situ AFM force curve measurements showed three layered structures at Au (111)/EMITFSI interface, but no force curves with saw-toothed feature can be obtained when the potential is higher than +0.5 V, which implies the disappearance of layered structures. In EMMITFSI, force curves with saw-toothed feature can be obtained even at +1.2 V. The fact that layered structures can form in a broader potential region indicates that a stronger interaction exists between the EMMI cation and the TFSI anion. It is inferred that the methylation of the hydrogen position provides a configuration for EMMI cations with an increased hydrophobic interaction, which maintains the layered structure in wider potential region. As a consequence, the electrode potential may induce structural transition of the layered structures, which is responsible for the origin of the voltammetric features.This work is supported by Natural Science Foundation of China (Nos. 21673193, 21533006, 21727807 and 21621091) and the Natural Science Foundation of Fujian Province of China (Grant 2016J01075). MICINN (Spain) support from project CTQ2016-76221-P is greatly acknowledged. ELECTRONANOMAT (Grant Agreement Number: PIRSES-GA-2012-318990) under European Framework Programme-Marie Curie Actions is also acknowledged

Electrochemical interfaces in ionic liquids/deep eutectic solvents incorporated with water: A review

Abstract Ionic Liquids (ILs) and deep eutectic solvents (DESs) are promising candidate electrolytes in electrochemical fields due to their excellent properties. They can absorb water from the environment quickly, the existence of water in ILs/DESs benefits or harms their performance depending on the purpose of the applications. Therefore, studies on the effect of water on the properties of ILs/DESs have received much attention in recent years. This mini‐review provides an overview of the structure of the electrochemical interface in ILs/DESs incorporated with water by summarizing the information acquired from a variety of characterization technologies and simulations. Both our understanding of the interfacial structure and our perspective on further research in the field are presented