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Faraday Discussions

A Robert Hillman, Robert Barker, Robert M Dalgliesh, Virginia C Ferreira, Emma J R Palin, Rachel M Sapstead, Emma L Smith, Nina-Juliane Steinke, Karl S Ryder, Andrew D Ballantyne
Exquisite control of the electrodeposition of metal films and coatings is critical to a number of high technology and manufacturing industries, delivering functionality as diverse as anti-corrosion and anti-wear coatings, electronic device interconnects and energy storage. The frequent involvement of more than one metal motivates the capability to control, maintain and monitor spatial disposition of the component metals, whether as multilayers, alloys or composites. Here we investigate the deposition, evolution and dissolution of single and two-component metal layers involving Ag, Cu, and Sn on Au substrates immersed in the deep eutectic solvent (DES) Ethaline...
July 13, 2018: Faraday Discussions
Woochul Song, Yue-Xiao Shen, Chao Lang, Prantik Saha, Iryna V Zenyuk, Robert J Hickey, Manish Kumar
Artificial water channels are a practical alternative to biological water channels for achieving exceptional water permeability and selectivity in a stable and scalable architecture. However, channel-based membrane fabrication faces critical barriers such as: (1) increasing pore density to achieve measurable gains in permeability while maintaining selectivity, and (2) scale-up to practical membrane sizes for applications. Recently, we proposed a technique to prepare channel-based membranes using peptide-appended pillar[5]arene (PAP[5]) artificial water channels, addressing the above challenges...
July 12, 2018: Faraday Discussions
Cameron L Bentley, Patrick R Unwin
Techniques in the scanning electrochemical probe microscopy (SEPM) family have shown great promise for resolving nanoscale structure-function (e.g., catalytic activity) at complex (electro)chemical interfaces, which is a long-term aspiration in (electro)materials science. In this work, we explore how a simple meniscus imaging probe, based on an easily-fabricated, single-channeled nanopipette (inner diameter ≈ 30 nm) can be deployed in the scanning electrochemical cell microscopy (SECCM) platform as a fast, versatile and robust method for the direct, synchronous electrochemical/topographical imaging of electrocatalytic materials at the nanoscale...
July 12, 2018: Faraday Discussions
Di Huang, Quanfeng He, Jie-Jie Shan, Matthew Sartin, Ran Pang, Fang-Zu Yang, Yongliang Zhou, Bin Ren, Zhong-Qun Tian, Dongping Zhan
Recently, the photoelectric effect in metals in electrolyte environments has aroused the interest of researchers. However, direct evidence for surface plasmons-enhanced electrochemical reactions involving classic outer-sphere reactions of reversible redox couples is seldom reported. We used a surface plasmons-active gold-mushroom-array as a working electrode and observed enhanced faradaic current from ferrocenemethanol following illumination with a xenon lamp. The photoelectric current behaved differently in the presence and absence of oxygen in the solution...
July 12, 2018: Faraday Discussions
Sebastien Balme, Fabien Picaud, Mathilde Lepoitevin, Mikhael Bechelany, Emmanuel Balanzat, Jean-Marc Janot
We investigated ionic transport behavior in the case of uncharged conical nanopores. To do so, we designed conical nanopores using atomic layer deposition of Al2O3/ZnO nanolaminates and then coated these with trimethylsilane. The experimental results are supported by molecular dynamics simulations. The ionic transport reveals an unexpected behavior: (i) a current rectification and (ii) a constant conductance at low salt concentration which are usually reported for charged conical nanopore. To explain these results, we have considered different assumptions: (i) a default of functionalization, (ii) the adsorption anion and (iii) the slippage...
July 11, 2018: Faraday Discussions
Xianchan Li, Johan Dunevall, Andrew G Ewing
We use an electrochemical platform, nanoparticle tracking analysis, and differential centrifugation of single catecholamine vesicles to study the properties of nanometer transmitter vesicles, including the number of molecules, size, and catecholamine concentration inside. Vesicle impact electrochemical cytometry (VIEC) was used to quantify the catecholamine content of single vesicles in different batches isolated from pheochromocytoma (PC12) cells with different ultracentrifugation speeds. We show that, vesicles containing less catecholamine are obtained at subsequent centrifugation steps with higher speed (force)...
July 10, 2018: Faraday Discussions
Viorel Nastasa, Cristina Stavarache, Anamaria Hanganu, Adina Coroaba, Alina Nicolescu, Calin Deleanu, Aude Sadet, Paul R Vasos
Water uptake in vesicles and the subsequent exchange between water protons and amide -NH protons in amino acids can be followed by a new, highly sensitive, type of magnetic resonance spectroscopy: dynamic nuclear polarisation (DNP)-enhanced NMR in the liquid state. Water hydrogen atoms are detected prior to and after their transfer to molecular sites in peptides and proteins featuring highly-accessible proton-exchangeable groups, as is the case for the -NH groups of intrinsically disordered proteins. The detected rates for amide proton-water proton exchange can be modulated by membrane-crossing rates, when a membrane channel is interposed...
July 10, 2018: Faraday Discussions
Ke Huang, Jan Clausmeyer, Long Luo, Karalee Jarvis, Richard M Crooks
In this paper, we report the electrosynthesis and characterization of individual, shape-controlled Pt nanocrystals (NCs) electrodeposited on carbon nanoelectrodes (CNEs). Single Pt NCs were deposited onto the CNEs using an empirically developed square-wave potential program. Characterization by scanning electron microscopy indicates that the sizes of Pt NCs are remarkably reproducible (relative standard deviation = 6%). Electrochemically active surface areas, determined by Cu underpotential deposition and H adsorption/desorption analyses, are also reproducible...
July 10, 2018: Faraday Discussions
Oscar Diaz-Morales, Thomas J P Hersbach, Cansin Badan, Amanda C Garcia, Marc T M Koper
The "hydrogen region" of platinum is a powerful tool to structurally characterize nanostructured platinum electrodes. In recent years, the understanding of this hydrogen region has improved considerably: on Pt(111) sites, there is indeed only hydrogen adsorption, while on step sites, the hydrogen region involves the replacement of adsorbed hydrogen by adsorbed hydroxyl which interacts with co-adsorbed cations. However, the hydrogen region features an enigmatic and less well-understood "third hydrogen peak", which develops on oxidatively roughened platinum electrodes as well as on platinum electrodes with a high (110) step density that have been subjected to a high concentration of hydrogen...
July 10, 2018: Faraday Discussions
Ramya H Tunuguntla, Andrew Y Hu, Yuliang Zhang, Aleksandr Noy
Carbon nanotubes represent one of the most interesting examples of a nanofluidic channel that combines extremely small diameters with atomically smooth walls and well-defined chemical functionalities at the pore entrance. In the past, sub-1 nm diameter carbon nanotube porins (CNTPs) embedded in a lipid membrane matrix demonstrated extremely high water permeabilities and strong ion selectivities. In this work, we explore additional factors that can influence transport in these channels. Specifically, we use stopped-flow transport measurements to focus on the effect of chemical modifications of the CNT rims and chaotropic polyethyleneglycol (PEG) additives on CNTP water permeability and Arrhenius activation energy barriers for water transport...
July 10, 2018: Faraday Discussions
Shao-Chuang Liu, Meng-Xiao Li, Meng-Yin Li, Ya-Qian Wang, Yi-Lun Ying, Yong-Jing Wan, Yi-Tao Long
Nanopore analysis is a powerful technique for single molecule analysis by virtue of its electrochemically confined effects. As a single molecule translocates through the nanopore, the featured ionic current pattern on the time scale contains single molecule characteristics including volume, charge, and conformational properties. Although the characteristics of a single molecule in a nanopore have been written to the featured ionic current, extracting the dynamic information from a complex current trace is still a big challenge...
July 9, 2018: Faraday Discussions
Andrea Vezzoli, Richard J Brooke, Nicolò Ferri, Carly Brooke, Simon J Higgins, Walther Schwarzacher, Richard J Nichols
In recent years, the use of non-metallic electrodes for the fabrication of single-molecule junctions has developed into an elegant way to impart new properties to nanodevices. Integration of molecular junctions in a semiconducting platform would also speed technological deployment, as it would take advantage of established industrial infrastructures. In a previous proof-of-concept paper, we used simple α,ω-dithiol self-assembled monolayers on a gallium arsenide (GaAs) substrate to fabricate molecular Schottky diodes with a STM...
July 6, 2018: Faraday Discussions
Tobias Löffler, Patrick Wilde, Denis Öhl, Yen-Ting Chen, Kristina Tschulik, Wolfgang Schuhmann
The quantitative characterisation of electrocatalytic properties of nanoparticle catalyst materials is so far only performed for layers typically comprising additionally conducting additives and binders. We propose a method enabling the evaluation of intrinsic catalytic activity of nanoparticles based on the diffusion-limited steady-state current. In a step-after-step process, the influence of coverage on kinetic and diffusion limited current is evaluated to highlight the challenges of sub-monolayer electroanalysis...
July 6, 2018: Faraday Discussions
Tong Sun, Dengchao Wang, Michael V Mirkin
This paper is concerned with long-distance interactions between an unbiased metal nanoparticle (NP) and a nanoelectrode employed as a tip in the scanning electrochemical microscope (SECM). A NP immobilized on the inert substrate acts as a bipolar electrode, producing positive SECM feedback. The tip current magnitude depends strongly on the ratio of the particle and tip radii and the heterogeneous charge-transfer kinetics. The onset of electron tunneling was observed at very short separation distances (<2-3 nm) at which the NP behaves as a part of the tip electrode...
July 6, 2018: Faraday Discussions
Jean-François Lemineur, Jean-Marc Noël, Catherine Combellas, Dominique Ausserré, Frédéric Kanoufi
The interest in nano-objects has recently dramatically increased in all fields of science, and electrochemistry is no exception. As a consequence, in situ and operando visualization of electrochemical processes is needed at the nanoscale. Herein, we propose a new interferometric microscopy based on an antireflective thin metal electrode layer. The technique is coupled to electrochemistry in a model example: the electro-deposition of Ag metallic nanoparticles (NPs). This challenges the current opto-electrochemical methods and even those relying on nano-impact detection...
July 5, 2018: Faraday Discussions
Wanfeng Yang, Wensheng Ma, Zhonghua Zhang, Chuan Zhao
Electrochemical CO2 reduction (ECR) depends significantly on the nanostructures of electrocatalysts. Here we show a nanoporous Ag network catalyst (np-Ag) for efficient electrochemical reduction of CO2. The np-Ag samples with an average ligament size of 21 nm (denoted by np-Ag (21 nm)) and 87 nm (denoted by np-Ag (87 nm)) were fabricated by dealloying the rapidly solidified Mg80Ag20 (wt%) alloy ribbons in 1 wt% citric acid and 5 wt% phosphoric acid, respectively. The ligament size effect on the electrocatalytic activity and selectivity of CO2 conversion into CO is investigated...
July 5, 2018: Faraday Discussions
Martin Vögele, Jürgen Köfinger, Gerhard Hummer
Artificial channels made of carbon nanotube (CNT) porins are promising candidates for applications in filtration and molecular delivery devices. Their symmetric shape and high mechanical, chemical, and thermal stability ensure well-defined transport properties, and at the same time make them ideal model systems for more complicated membrane protein pores. As the technology to produce and tune CNTs advances, simulations can aid in the design of customized membrane porins. Here we concentrate on CNTs embedded in lipid membranes...
July 5, 2018: Faraday Discussions
Daniel Ryan Barden, Harish Vashisth
Biomimetic membranes, designed by combining proteins or protein-mimics with self-assembled block copolymers, are emerging as novel hybrid materials with applications in the next generation of sensing and separation devices. However, designing such membranes requires a fundamental understanding of the atomic-scale interactions between biological channel proteins and their non-native polymeric membrane environment as it affects their stability and function. In principle, all-atom molecular dynamics (MD) simulations are well-suited to probe the atomistic details of channel/membrane interactions, but the absence of interatomic potentials is a major limiting factor in conducting such simulations...
July 5, 2018: Faraday Discussions
Laurent Bacri, Hajar Mamad-Hemouch, Cédric Przybylski, Bénédicte Thiébot, Gilles Patriarche, Nathalie Jarroux, Juan Pelta
Biomimetic ion channels can be made to display the high sensitivity of natural protein nanopores and to develop new properties as a function of the material used. How to design the best future biomimetic channels? The main challenges are to control their sensitivity, as well as their syntheses, chemical modifications, insertion and lifetime in a lipid membrane. To address these challenges, we have recently designed short cyclodextrin nanotubes characterized by mass spectrometry and high-resolution transmission electron microscopy...
July 5, 2018: Faraday Discussions
Samuel Murail, Tudor Vasiliu, Andrei Neamtu, Mihail Barboiu, Fabio Sterpone, Marc Baaden
Artificial water channels (AWCs) have been designed for water transport across membranes with the aim to mimic the high water permeability observed for biological systems such as aquaporins (∼108-109 water molecules per s per channel), as well as their selectivity to reject ion permeation at the same time. Recent works on designed self-assembling alkylureido-ethylimidazole compounds forming imidazole-quartet channels (I-quartets), have shown both high water permeability and total ionic-rejection. I-quartets are thus promising candidates for further development of AWCs...
July 5, 2018: Faraday Discussions
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