INTL. SYMP. ON ELECTROCHEMISTRY FOR SUSTAINABLE DEVELOPMENT

Two-dimensional (2D) nanomaterials, such as graphene and transition metal dichalcogenides, hold extraordinary promise for applications in a number of electrochemical technologies. Electrochemical energy storage (EES) devices, such as lithium-ion batteries, flow batteries, and supercapacitors, in particular, have seen 2D materials integrated into various components with exciting results. In general, EES devices are emerging as primary power sources for global efforts to shift energy dependence from limited fossil fuels towards sustainable and renewable resources. These EES devices, while renowned for their high energy or power densities, portability, and long cycle life, are still facing significant performance hindrance due to manufacturing limitations. One major obstacle is the ability to engineer macroscopic components that possess designed and highly resolved microstructures with optimal performance, via controllable and scalable manufacturing techniques. 3D printing covers several additive manufacturing methods that enable well-controlled creation of functional materials with 3D architectures, representing a promising approach for fabrication of next-generation EES devices with high performance. Here, we present recent work to a) develop modeling and optimization algorithms that determine the optimal electrochemical cell geometries for various performance objectives (e.g. maximize current, minimize pressure drop, etc.) and b) fabricate 3D functional electrodes utilizing 3D printing-based methodologies. Specifically, the framework of the 3D printing techniques such as projection microstereolithography and direct ink writing are described, as well as the details of respective feedstock development efforts. Finally, characterization of the 3D-printed electrodes and their performance in various EES applications (e.g. supercapacitors and batteries) will be compared with predicted performance and discussed.

Surface-enhanced Raman spectroscopy (SERS) is one of the few powerful in-situ electrochemical spectroscopies, since it is highly sensitive on the surface species and almost inert on the species in the bulk of electrolyte. However, in order to comprehensively understand electrocatalysis, EC-SERS has to be correctly understand and consistent with the electrochemistry and theory. Here, we present the EC-SERS study on the electrocatalytic reduction of benzyl chloride on Ag by combing experiments and theoretical calculations.
To identify the electrode surface species, we performed DFT calculations with Raman spectroscopy on the possible reaction intermediates and products. The results show that the Raman spectrum of the negatively charged benzyl-Ag cluster shows similar spectroscopic characters as experimental spectra, which indicates benzyl anion adsorbed Ag electrode is the key intermediate of the electrocatalytic reduction of benzyl chloride on Ag. By applying the same strategy, we also studied the adsorption of benzyl chloride and the possible products.
In light of the reaction pathway roughed out by the consistent EC-SERS observations and DFT simulations on the spectra, the details of the electrocatalysis regarding the binding energy and the activation energy of reactants and intermediates are revealed by electrochemical kinetics calculation combined with DFT calculation. We found that the weakly interaction between distorted benzyl chloride anion and Ag facilitates the dissociation of C-Cl bond and drives the conversion of benzyl chloride. The more detailed discussion will be given.
The combined EC-SERS/DFT investigation provides a key entry for understanding the origin of electro-catalytic activity by consistent experimental observations and theoretical calculations.

A systematic quantitative description of the main stages of the electrochemical process involving metal complexes is presented, and methods for taking into account the role of chemical stages are proposed.
The generalized model of mass transfer of chemically interacting particles is based on a system of differential equations containing both diffusion and kinetic terms [1]. The total surface concentration of metal-containing species can be determined at any kinetics of chemical steps using the convolution of current transients. Surface distribution of individual species depends on the degree of system liability. It serves as the basis for determining the surface concentrations that are used further in the analysis of the charge transfer kinetics. Based on the congruence of voltammograms and plots of potentiometric titration, the features of the processes occurring in labile systems are revealed. These are: development of cathodic pre-waves, anodic pseudo-limiting currents, double current maxima, etc. Methods for determining the composition of the electrochemically active complex (EAC) are substantiated taking into account the specificity of complex systems. Kinetic equations of direct and consecutive charge transfer are analyzed with their further transformation into Tafel plots normalized with respect to the EAC surface concentration. Prospects for extension of theoretical developments to other systems, in particular, to the processes of hydrogen evolution involving ligands as proton donors, are considered.

This report presents the main results of investigations of electrochemical processes involving complexes of various metals, such as copper, tin, zinc, cobalt. Particular attention is paid to systems containing ecological ligands: glycolic, malic, tartaric, citric, gluconic and other hydroxy acids.
The presence of pre-waves and double maxima on cathodic polarization curves obtained in the ligand-deficient solutions is experimentally confirmed. Kinetic parameters of charge transfer process are determined while taking into account the redistribution of species at the electrode surface [1]. In this case, the transformation of experimental voltammograms into normalized Tafel plots is used, which turn out to be close to linear, even in the case of very complex initial voltammograms. Similar data are given for the deposition of the Cu-Zn, Cu-Sn, Co-Sn, Co-Mo alloys. The characteristics and sequence of partial processes are analyzed, as well as their interaction under the codeposition conditions. The role of surfactants leading to the formation of surface complexes is demonstrated by the example of Cu and Sn codeposition in the presence of polyethers.
Brief information is provided on the account of side processes that often attend the reduction of metal complexes. Conditions for spontaneous formation of photosensitive surface Cu₂O layers are established and their photoelectrochemical behavior is investigated. The appearance of current oscillations is demonstrated in the region of voltammogram characterized by negative impedance. The regularities of hydrogen evolution involving ligands as proton donors are discussed.

The photoconversion of CO₂ by artificial photosynthesis is an area of great interest [1]. In this context, there is a great search for new semiconductors able to generate charge carriers (e-/h+) when irradiated by sunlight. Thus, the present work investigated the surface modification of TiO₂ nanotubes electrodes (NtTiO₂) with copper porphyrins for the CO₂ reduction by electrocatalysis, photocatalysis, and photoelectrocatalysis using UV/vis light and different potentials during 2h. For this, NtTiO₂ were constructed by anodization [2] and modified with three different porphyrins: [Cu(T4H3MPP)] (NtTiO₂-P1), [Cu(TDCPP)] (NtTiO₂-P2) and [Cu(TDCSPP)] (NtTiO₂-P3) (P1 and P2 = neutral copper(II)porphyrins and P3 = anionic Cu(II)porphyrin) using a wet chemical deposition method. These electrodes were characterized by SEM, XRD, linear and cyclic voltammetry. The CO₂ reductions were performed in 0.1 mol L-1 Na₂SO₄ with CO₂ using a photoelectrochemical reactor and Xe lamp of 300 W (Newport 67005) [3]. The NtTiO₂-P1 electrode when compared with the other materials presented a more homogeneous surface with porphyrin dispersed on well organized nanotubes and bang gap of 2.9 eV. The XRD showed the characteristics peaks of anatase and copper oxide II phases in all materials. The photoactivity of the semiconductors presented the same behavior for the three materials, showing a good response under light incidence, as the cyclic voltammetry that showed a new peak in presence of CO₂ around -0.8 V. All the semiconductors were applied in the CO₂ reduction with the best results obtained under -0.8 V for photoelectrocatalysis. Methanol was formed under all semiconductors, with different concentrations: 0.35 mmol L-1 for (NtTiO₂-P1) and 0.020 mmol L-1 for the other materials, while ethanol formation occurs just on NtTiO₂-P1 semiconductor forming 0.03 mmol L-1.The electrocatalysis and photocatalysis presented a smaller methanol and ethanol formation applying NtTiO₂-P1 electrode. [Cu(T4H3MPP)] porphyrin presented the best adsorption in the TiO₂ nanotube surface and NtTiO₂-P1 semiconductor yielded the higher concentration of products formation by the CO₂ reduction.

An environmental threat concern for the Earth's climate is the excessive level of CO₂ in the atmosphere, which reached an astounding 408 ppm in February 2018. Thus, the development of efficient alternatives for removal, sequestration, use, and conversion of this gas through higher value-added products has become a great challenge nowadays [1]. With remarkable advances in the past decades, photoelectrocatalysis techniques have proven to be viable alternatives for CO₂ conversion to formic acid, methane, methanol [2] and ethanol [3]. The present work investigates the properties of Polydopamine (PDA) and Nafion® (NF) as mediator's polymers in the modification of TiO₂ nanotubes (NtTiO₂) with Cu₂O nanocubes (NcCu₂O) and its applicability in CO₂ conversion. The use of PDA and NF promoted great adhesion of NcCu₂O previously synthesized as demonstrated by the results of MEV-FEG, Infra-Red, Diffuse Reflectance Spectroscopy, and photocurrent vs potential curves. However, NtTiO₂/PDA-NcCu₂O electrodes showed better adhesion and stability, higher performance when excited by UV-Vis irradiation, and good photoactivation even when excited by solar radiation. Assessment of the photoelectrocatalytic performance of both electrodes in the CO₂ reduction dissolved in 0.1 mol L-1 Na₂SO₄, pressure of 1 kg f cm-2, applied potential of 0.2 V vs Ag/AgCl and UV/Vis irradiation, indicates that the results are improved at NtTiO₂/PDA-NcCu₂O electrodes. The selective conversion of CO₂ to methanol after 120 min of photoelectrolysis was 14% (10 ppm), 40% (7 ppm) and 20% (4 ppm) higher when PDA was used, and the system illuminated by UV/Vis radiation of 300 W, 125 W lamp and solar simulator radiation, respectively. Our findings indicate that the use of PDA is a good strategy to obtain heterojunction p-n semiconductors and to improve its performance in the visible light region. The photoelectrocatalysis conducted at NtTiO₂/PDA-NcCu₂O is a promising alternative to convert CO₂ to added value compounds.

Prof. Christian Amatore is one of the pioneering and most authoritative scientists on ultramicroelectrodes, in both its fundamentals and methodologies. In his honorary symposium, we would like to give a mini-review of our work on nanoelectrodes at Xiamen University, to which many helpful discussions were contributed by our respected old friend, Prof. Amatore. First, we will present a method based on Fick's second law, to further prove the surface diffusion of adsorbates and quantitative measurements of surface diffusion coefficient of Faraday adsorbates on Au or Pt nanoelectrodes. Second, we will present the single molecular enzyme catalysis on the nanoelectrode, including a statistical method to obtain the turnover number of single molecular enzymes. Third, we will present the plasmon-induced voltammetric behavior on the nanostructured Au electrode.
The mobility of adsorptive atoms and molecules on catalyst surfaces is one of the most fundamental issues in solid surface science. It plays a pivotal role in various physiochemical processes, especially in thin-film deposition and heterogeneous catalysis. Quantifying the surface mobility will aid in a more in-depth understanding of the mechanism underlying these processes. Therefore, numerous spectroscopic methods have been developed for measuring surface diffusion coefficients, and many systematic investigations have been performed on solid surfaces in vacuum or atmospheric environment.
However, studying surface mobility on solid surface in liquid environment, especially in electrochemical systems, still faces challenges both in experiment and theory. The reason mainly stems from the fact that most of the techniques adopted for surface diffusion traditionally don't work at solid/liquid interfaces. Moreover, the co-adsorption of the water molecules or electrolyte ions, and the presence of strong electric fields make it extremely complicated at the electrochemical interface. Nevertheless, information on the transport and interaction of atoms or molecules on electrode surfaces is badly needed for gaining insights into many electrochemical interface processes, such as electrodeposition and electrocatalysis. These processes are directly related to electrochemical energy conversion, metal electrode processes, as well as other electrocatalytic domains.

Electrocodeposition of various Cu and Sn alloys to obtain metallic coatings is a process with a wide range of practical applications, from microelectronics to corrosion protection [1]. Such coatings show good solderability, malleability, and superior corrosion resistance. In order to control the co-deposition process and obtain the desired characteristics of final coatings, various surface active additives are traditionally employed [2-3]. Polyether (PE) compounds such as polyethylene glycol (PEG) is one of the well-known electroplating additives used to control Cu deposition rate. A number of studies have discussed the effects and underlying mechanisms of PEG for Cu deposition [4], however the effects of PEG in the case of Sn and Cu/Sn alloys are not well understood. In this work, we use periodic density functional theory calculations of various Cu and Sn surfaces and their interactions with various model adsorbates, such as ethylene glycol, oligoethylene glycols of various chain lengths, and PEG. In addition, to significantly differentiate electronic structure of Cu and Sn surfaces, the results also show different adsorption of hydroxyl, ether, and polyether species on these surfaces, which might explain the different behaviors of Cu/Sn electroplating.

Screen-printed electrodes (SPEs) are devices widely employed in the manufacturing of sensors and biosensors, because they have good stability and are manufactured by simple and scalable techniques. Furthermore, these electrodes can be easily modified with biomolecules— the best-known example being the glucose biosensor used in the diagnosis of Diabetes mellitus, which represents a market of approximately one billion of US Dollar [1]. In this work, we developed a method for manufacturing screen-printed electrodes using a laboratory-made conductive ink, employing terpene solvent, preferentially d-limonene, recycled polymeric additive derived from petroleum polymers, specifically polystyrene and micronized graphite and carbon black nanoparticle as conducting components [2]. In the process of conductive ink production, the concentrations of the components were optimized and appropriate parameters were established to obtain several types of inks with viscosity, surface area, and electric resistance modulated for the desired applications. After a complete characterization, screen printed electrodes were fabricated with two composition of the obtained laboratory-made conductive inks. A proof of concepts of their analytical application was made for the determination of ferrocene, catechol, ascorbic acid, hydroquinone, and potassium ferrocyanide/ ferricyanide.

ECL is a powerful tool for the study of electron transfer pathways and development of luminescent devices. Ru(II) and Ir(III) luminophores are the most commonly used concomitant electrochemiluminophores, owing to their high ECL efficiencies with TPrA as the co-reactant. Although the selective excitation of electrochemiluminophores was highly expected to open new avenues for multianalyte detection, over the years its application in this area was still limited. The major drawback is the weak solubility of Ir complexes in water, which limits the biological application of multi-color ECL. We adopted closed bipolar electrode (BPE), which solved the challenge by separating organic ECL emitters from the analyte. Selective excitation of the electrochemiluminophores (Ru(II) and Ir(III) luminophores) could be achieved by tuning the interfacial potential at the poles of BPE. Along with the increasing potential, the ECL intensities of the two emitters varied, and the emission color changed, which enabled us to detect biomarkers on a BPE array with different strategies. With a single DC power supply, prostate-specific antigen (PSA), circulating microRNA-141 (mRNA-141) and small molecular marker, sarcosine were simultaneously detected by the array.

Any approach of an energy planning program based on the sustainable development concept should consider the use of Proton Exchange Membrane Fuel Cells (PEM-FC). These electrochemical devices can be easily inserted in an Energy-production and distribution net because of their low pollution, portability, high efficiency, and wide range application characteristics [1-2]. However, PEM-FC still demands some improvements to decrease the production and operational costs and increase the efficiency for some fuels oxidation reactions. In this perspective, the development of new and more efficient electrocatalysts for fuel oxidation reactions has been considered a priority worldwide. Nevertheless, the development or improvement of electrocatalysts is limited by the lack of appropriated knowledge on materials activity. In this work, the authors present the study performed on the influence of the architectural disposition of metal elements in the geometric structure of electrode materials, and the resulting performance towards the anode reaction. We synthesized and fully characterized materials in the systems Pt-Sn and Pt-Ni— structured as ordinary alloy, ordered intermetallic, and core-shell nanoparticles— in the same metal proportion 1:1 (Pt:M), and evaluated them as anode for the eletrooxidation of hydrogen, methanol, ethanol, ethyleneglycol and glycerol fuels. It was concluded that, despite the same chemical composition and particle size, the electronic density of the Pt surface adsorption site is deeply affected by the energy of interaction with the foreign metal (Sn or Ni). Therefore, the structure as the nanoparticle crystallizes will influence the adsorptive characteristic of the anode material, thus determining the performance as efficient electrode material for the electrooxidation of a given fuel.

To curb the negative effect of carbon dioxide as a greenhouse gas, an interesting approach is the utilization of Carbon Capture and Conversion (CCC) methodologies. These recycling technologies are focused on the use of CO₂ waste as a feedstock for the production of industrially relevant chemicals. In the past years, increasing attention has been devoted to the electrochemical conversion of CO₂, which would combine the utilization of excess electric energy from intermittent renewable sources with the selective conversion of CO₂ into added value products. Furthermore, it would be possible, in order to reduce the costs, to use the excess of the daily produced electricity, not matching actual demand energy, that is usually lost or not properly used. Researches have shown that several products, including carbon monoxide, formic acid, methane, methanol, ethylene and oxalic acid, can be obtained by this process. Furthermore, it has been shown that carbon dioxide can be introduced in the backbone of other molecules, generating fine chemicals with high economic value, such as anti-inflammatory drugs, by cathodic reduction in aprotic solvents
In this work, various routes for the electrochemical conversion of carbon dioxide will be presented and discussed from both a scientific, technical and economic point of view, such as the synthesis of formic acid in water (in conventional and pressurized cells) or the electrocarboxylation of aromatic ketones and benzyl chlorides in organic solvents, in order to illustrate the current scenario.

Traditional thin-film synthetic diamond electrodes produced by chemical-vapor deposition (CVD, see [1, 2]) are remarkable for their wide potential window and low background current in supporting electrolytes and good reproducibility. However, they are not free of disadvantages, particularly from the film exfoliation from substrate, thru-holes, etc. In this work we presented a new electrode material, heavily boron-doped diamond compacts whose electrochemical properties are studied for the first time. Cylinder-shaped polycrystalline samples, 3.5-4 mm in diameter and 2.5 mm in height, were prepared by thermobaric processing of graphite-boron carbide mixtures at the pressure of 8-9 GPa and temperature of ~2500 K [3]. Their diamond nature, in particular, the absence of graphite, was confirmed by Raman spectroscopy and XRD technique. Their electrode behavior is studied by using cyclic voltammetry and electrochemical impedance spectroscopy. The compacts are shown to be superior to conventional thin-film CVD-diamond electrodes in their electrode characteristics. In particular, they have wide potential window, low background current in indifferent electrolytes (KCl, K₂SO₄), and good reproducibility. Moreover, their extremely high doping level makes them more electroactive, as can be seen by the current of Cl₂ anodic evolution from KCl solutions (figure), some organics electrooxidation, etc. [4].
Thus, the diamond compacts are well comparable to the CVD-diamond electrodes. At the same time, they are free of some drawbacks inherent in the latter. Moreover, their concentrated form can be advantageous in the designing of electrochemical devices. One might think that they can successfully be used, e.g., as electrodes in electrosynthesis, electroanalysis, water treatment, etc. [5].

Recently, the investigation on electrochemical biosensing has made great progress. The developed biosensors have extensively been used in different fields, particularly, the sensitive and accurate detection of DNA, protein and metal ions. The designs of specific electrochemical catalytic probes are becoming the main topic of electrochemical biosensing research. This presentation will introduce new electrochemical catalytic probes designed in our group for development of amplified biosensing strategies in last two years. For example, we prepared two electrochemical catalytic probes to design two molecular switches for electrochemical DNA sensing by coupling with porphyrin-encapsulated metal-organic frameworks. Several new signal amplification strategies based on nanotechnology and molecular biology have been presented for DNA detection and immunoassay. By the recognition of nucleic acids to metal ions, some label-free methods have been developed for specific and sensitive detection of heavy metal ions. Some new electrochemiluminescent emitters have been synthesized and used for design of new ECL biosensing mechanisms. A wavelength-resolved ratiometric photoelectrochemical technique has also been developed for sensing applications. These works led to a series of amplified methods for sensitive detection of DNA, microRNA and proteins.

Even though Oxygen Reduction Reaction, (ORR), kinetics have been studied by many authors over several decades, [1-3], the electrochemical mechanism still remains an open subject of debate and research. Elucidating ORR kinetics is of paramount importance in advancing Fuel Cell technology, which in turn will result in faster commercialization and robust applications for a greener future. In this work we propose a microkinetic transition state multistep reaction mechanism for ORR which takes place inside the cathodic electrode of a High Temperature Polymer Electrolyte Fuel Cell, (HTPEMFC). ORR kinetics are analyzed by the means of Electrochemical Impedance Spectroscopy, (EIS), in the kinetic low current density, (lcd), regime of operation where ORR activation power losses are dominant. The corresponding impedance spectra contain a linear high frequency part feature and two arcs depending on the double layer capacitance, (Cdl), value. This high frequency linear part of the spectrum originates from the finite ionic, (H+), resistance in the catalyst layer. The high frequency arc, under which all charge transfer reaction steps appear, is directly related to the Cdl of the electrochemical interface, (EI), while the low frequency arc stems from the relaxation of the adsorbed surface reaction intermediates on the catalyst surface, which is caused by the depletion of OHad on the surface. Our proposed kinetic model provides two Tafel slopes in the low and high current density (hcd) regime equal to 60 (mV/dec) and 180 (mV/dec) respectively.

Commercial solar photovoltaic technologies such as Si and CdTe are traditionally considered to be in a separate domain from electrochemistry. Their device operation is governed by semiconductor physics and their production involves non-electrochemical processes such as diffusion, screen printing, fractional distillation, etc. However, electrochemistry will likely play an indispensable role in sustaining the commercial solar technologies. This talk will discuss three roadblocks to sustainable solar photovoltaics and how electrochemistry can remove these roadblocks: 1) storage of intermittent solar electricity, 2) scarce Ag used in today's Si solar cells, and 3) high energy input in producing solar Si wafers. An off-grid route is proposed for solar electricity storage based on a closed loop of Zn-ZnO [1], in which Zn rods are produced in a solar electrolyzer from ZnO. The Zn rods are shipped to homes, offices, factories, and electric vehicles to be inserted into mechanically-recharged Zn/air batteries, for electricity on demand. The spent Zn anodes are collected for regeneration of Zn in the solar electrolyzer. This Zn-ZnO loop is advantageous over the H₂-H₂O loop in terms of theoretical performance and technical readiness. Electroplated Al on Si is proposed to replace the screen-printed Ag electrode in Si solar cells [2]. 18% efficiency has been demonstrated in a Si solar cell with an electroplated Al front electrode and a screen-printed Al back electrode, i.e., an Ag-free all-Al Si solar cell. To overcome the high resistivity of the solar Si wafer, direct Al plating on Si without any seed layer is developed through light-induced Al plating. Direct Al plating on Si drastically simplifies the metallization process for Al, resulting in a significantly-lower cost than competing technologies. Finally, electrochemical refining of metallurgical-grade Si for solar-grade Si has been unsuccessful. While metals up to 99.99% purity are readily produced by electrochemistry, solar-grade Si requires a purity of at least 99.9999%. This is coupled with non-electrochemical difficulties in Si purification such as oxidation of the Si anode and crystallinity of the Si cathode. An analysis will be presented on the foundation for ultrapure materials by electrochemistry [3]. The reason for unsuccessful Si electrochemical refining will be discussed through an analogy between electrochemical refining and fractional distillation.

The possibility and conditions of using lower oxidation state metal ions as reducing agents for autocatalytic electroless metal deposition are discussed. The theoretical background of these types of reactions is presented from a thermodynamics perspective. Kinetic data on electroless silver, copper, palladium, and platinum deposition, using Co (II)/Co (III) redox systems with different ligands are presented and discussed. Ti (III)/Ti (IV) redox systems with different ligands were also shown to be suitable reducing agents for reducing Pt (IV), Pd (II), Ni (II) and Co (II) to a metallic state and forming a continuous metal layer on the surface to be plated. The morphology of metal layers deposited using above-mentioned reducing agents was characterized by means of Field Emission Scanning Electron Microscopy (FESEM). Kinetics of the metal deposition rate was investigated by means of the gravimetry or Electrochemical Quartz Crystal Microgravimetry (EQCM).

Lability of electrochemical systems is one of the substantial characteristics for determining kinetics of the processes involving chemical steps.
A sufficiently rigorous quantitative estimate of this parameter is possible only for the preceding reactions of the first or pseudo-first order [1]. For more complex systems, such as solutions of metal complexes, there are no analytical expressions. To get around this obstacle, we analyzed the concentration profiles simulated using differential diffusion equations supplemented by the corresponding kinetic terms [2].
In the case of high lability, interrelation between concentrations of species is specified by stability constants of metal complexes. The certain deviations from equilibrium distribution are observed in the diffusion layer for less labile systems. In default of the electrically active complex, the reaction layer concept can be applied and used in the electroanalysis.
LPS voltammetric data obtained for hydrogen evolution on copper electrode in weakly acidic glycine solutions were used as basis for estimation of electrochemical lability of different glycine species. The dependence of current peaks on both solution pH and glycine concentration and the convolution of voltammograms show that only some protonated glycine species can act as labile proton donors in hydrogen evolution, since protons attached to different groups in glycine molecule exhibit different mobility. In contrast to protonated amino group, the release of proton from carboxylic group proceeds significantly faster. Consequently, protonated ⁺H₃N-CH₂-COOH species can be treated as labile proton donors, whereas zwitterions ⁺H₃N-CH₂-COO^- do not fall into this category.

Over the last few years, our group has been intrigued by catalytic cyclopropanations of N-Boc-pyrroles, which provides a stereoselective entry into bicyclic donor-acceptor substituted cyclopropanes that can be manipulated in various ways to natural products and synthetically useful building blocks. [1,2]. Herein we report the palladium catalyzed Heck-Mizoroki cross-coupling reaction between monocyclopropanated N-Boc-pyrroles and hetero/aryl halides leading to substituted 1,2-dihydropyridine preparation in moderate to good yields (40-81%). The arylation occurs selectively from the convex face of monocyclopropanated N-Boc-pyrrole, giving 1,2-dihydropyridine with an excellent transfer of chirality. The developed approach offers an attractive general method for accessing important six-membered nitrogen-containing scaffolds, which are in high demand in the pharmaceutical sciences and beyond. [3]

In this work, aiming at the construction of a sensitive, disposable system for the bioanalysis of unicellular samples, we report a single cell detection electrochemical (SCDE) platform based on Au@Pt nanostructures modified boron-doped nanocrystalline diamond microelectrode arrays (BNCD-MEAs) with 16 channels. The SCDE platform could be readily adapted for a highly sensitive detection of H₂O₂ released from stimulated single cell by ascorbic acid (AA), which could be utilized to distinguish cancer unicellular and normal unicellular ones. The Au@Pt nanostructures have good electrocatalytic activity for the H₂O₂ detection and were modified in the BNCD-MEAs by Pt NPs which were electrodeposited onto the BNCD-MEAs through an electrodeposition approach. As a result, this SCDE platform exhibited a wide linear range with a low detection for H₂O₂ determination. Furthermore, it also displayed satisfactory selectivity, excellent stability, and good reproducibility. The developed method opens a new pathway to clinical bioassay.

Air-hydrogen low temperature fuel cells are promising devices for a sustainable energy supply. Carbon-supported platinum-based nanoparticles are the most active and stable cathodic electrocatalysts [1]. Nowadays, attention has been moving towards Pt-free catalysts like metal oxides, carbides/nitrides, and metals-free or metals-doped carbons.
In this study, we investigated the influence of the cobalt and iron concentration in carbons on their catalytic activity and stability in the oxygen reduction reaction. Catalytically active carbons were prepared from a bimetallic zeolitic imidazolate framework (ZIF) [2]. The synthetic procedure included three steps: i) preparation of a hybrid Co/Zn-ZIF; ii) impregnation with iron acetate (II) and 1,10-phenanthroline; iii) calcination at 700 °C for 3 h under argon flow [3].
The properties of prepared materials were assessed with the set of techniques, including HR-TEM and SEM, TGA, XRD. High energy resolution fluorescence detection XANES spectra were measured at the ESRF. The electrochemical properties of the prepared electrocatalysts were investigated by cyclic voltammetry and linear sweep voltammetry.
The metal content was found influencing both morphology and catalytic activity of the prepared carbons. Increase in relative quantity of cobalt and in the final material stimulated formation of bamboo-like carbon nanotubes.

The electrochemical treatment of wastewater contaminated by organic and inorganic pollutants resistant to conventional processes is considered a very promising and appealing approach. The most interesting processes are the electrochemical direct oxidation, the indirect oxidation by electro-generated active chlorine, and the electro-Fenton. However, various problems limit the potential application of such methodologies [1], such as the cost of electric energy necessary to drive the process; the costs due to the addition of electrolyte for wastewater with low conductivity; the low current efficiencies due to the low mass transfer for low concentrations of pollutants.
In this work, various innovative approaches to solve or minimize such problems will be presented and discussed, such as the utilization of microfluidic cells (for both direct anodic oxidation and electro-Fenton) [2,3], pressurized reactors (for electro-Fenton) [4], microbial fuel cells [5] and reverse electrodialysis [6].
It will be shown that the utilization of such processes can drastically improve the performances of various electrochemical processes for the treatment of wastewater. In particular, the activation of various molecules able to oxidize organic pollutants will be discussed.

KISSA, the software developed in our group, provides a general framework to analyze and rationalize 1D- and 2D-electrochemical problems of any complexity within a user-friendly environment. Results are obtained without any intervention of user into numerical part except for defining the sought reaction mechanism using classical chemical formulations and initial values of the initial concertation, expected and equilibrium rate constants, diffusion coefficients, etc. [1]. The accuracy of the numerical solution is guaranteed in KISSA through performing calculations using non-uniform time grids and adaptive space grids. The latter one was constructed on the basis of specific kinetic criteria (rather than on a gradient-based one as in other programs). This offers a built-in automatic high dynamic resolution at moving acute reaction fronts which are readily detected and tracked by the program.
The efficiency of this strategy was proven by addressing such sophisticated problems as i) simulation of reaction mechanisms leading to the emission of electrochemiluminescence (ECL) [2, 3] and ii) solution of electrocatalytic problems involving the reactive dynamic adsorption steps [4, 5], etc.

In recent years, the industrial importance of lithium (Li) has increased due to its use in Li-ion batteries. Previously, the author had developed a method for the recovery of Li from seawater using a Li ionic superconductor functioning as a Li-ion separation membrane (LISM). In this method, only Li ions were successfully recovered from seawater through the LISM. Consequently, the author then developed a new innovative method for recycling Li from used Li-ion batteries using the LISM.
This innovative method involves the use of an LISM, whereby only Li ions in a solution of used Li-ion batteries permeate from the positive electrode side to the negative electrode side during electrodialysis; the other ions, including Co, Al, and F, do not permeate the membrane. Li_0.29La_0.57TiO₃ was selected as the LISM. The positive side of the dialysis cell was filled with used Li-ion battery solution. Then the negative side was filled with distilled water. The applied dialysis voltage was 5 V, and electrode area was 16 cm2. The Li recovery ratio increased with electrodialysis time. Subsequently, Co, Al, and F were not permeated.
After electrodialysis, CO₂ gas was bubbled in the Li recovery water to produce lithium carbonate (Li₂CO₃) as a raw material for Li-ion batteries. The Li₂CO₃ deposition was easily generated by the reaction of CO₂ gas and the Li recovery solution as a lithium hydroxide (LiOH) solution.
This new method for recycling Li-ion batteries shows good energy efficiency and is easily scalable. Thus, this electrodialysis method is suitable for the recovery of Li from used Li-ion batteries.

Electrosynthesis is a powerful tool in organic chemistry that circumvents the use of expensive and toxic reagents for the generation of reactive intermediates. During electrosynthesis, molecules are activated under mild and green conditions directly at the surface of an electrode. [1] Even though a plethora of transformations have been developed and many of them were successfully used in several industrial processes [2-4], the potential of preparative organic electrochemistry remains largely underestimated. However, the growing impetus to look for greener and cheaper alternatives to classic synthetic methodologies prompted us to further investigate new electrochemical reactions. We have recently developed two new electrochemical methodologies that allow the generation of organic and organometallic radicals under mild, green, economical, and safe conditions.
The first one allowed us to prepare a new class of organometallic drugs based on the cymantrene motif (CpMn(CO)₃). Anodic oxidation of the metallic core, under weakly coordinating conditions, allowed us to selectively replace one of carbonyl ligand (CO) by another ligand (L). This helped us to finely tune the physical properties of the drug, such as its redox potential or its lipophilicity. The final compounds have revealed to inhibit autophagy, and to have both very promising anticancer and antimalarial properties. [5-7]
In the same vein, we have recently developed a new electrosynthetic methodology to generate aroyloxy and benzamidyl radicals under mild conditions. The electrochemical reaction was even successfully scaled up to a 2g scale. [8] We are planning on using those radicals in the synthesis of other biologically relevant products such as phthalides, [9, 10] dihydroisocoumarins, [11, 12] isoindolinones, [13] and dihydroisoquinolones. [14] Those compounds are known to be important classes of bioactive compounds that are very often found in natural products. Several synthetic strategies have been developed for the synthesis of those scaffolds, but still rely on the use of expensive and hazardous chemicals which would prevent any industrial scale up. [15-17]

The electrification of our world, particularly road transportation and power storage, drives a strong increase in demand for lithium. The continued availability of lithium can only rely on a strong increase of mining and ore processing. It would be an inconsistency if the increased production of lithium salts for a more sustainable society would be associated with non-sustainable practices. Currently 2/3 of the world production of lithium is extracted from brines, a practice that evaporates half a million cubic metres of water per ton of lithium carbonate.
We will present an integrated membrane electrolysis concept to separate lithium from brines, driven by renewable power and delivering byproducts instead of waste. Our technology is based on a 4 stage process, each based on a water electrolyser with a side crystallizer. The chambers of the electrolysers are separated by anion and/or cation exchange membranes (AEM or CEM). At the anode, water will be oxidized to oxygen, and/or chloride to chlorine gas. In the cathode, water will be reduced to hydrogen, and the pH will increase. The applied potential and the need to maintain electroneutrality will make cations and anions selectively move to the cathodic or anionic compartments. By a careful pH adjustment with current flow, and selectively bubbling CO₂ at interval, it is possible to sequentially precipitate the different brine components, with Li₂CO₃ precipitating last.
Our proposed technology is fast, not requiring time consuming evaporation. Because it is much less dependent on solution composition, it could render the exploitation of a large number of currently unexploited resources possible, including salar brines and geothermal waters in Europe. Moreover, this technology will be much easier to adapt to different brines, and pilot scale runs will be performed quickly, as opposed to sluggish optimization in the evaporitic technology.

Nanochannels have brought new opportunities for biosensor development. Herein, we present the novel concept of a nanochannels photoelectrochemical (PEC) biosensor based on the integration of a unique Cu_xO-nanopyramid-islands (NPIs) photocathode, an anodic aluminum oxide (AAO) membrane, and alkaline phosphatase (ALP) catalytic chemistry. The Cu_xO-NPIs photocathode possesses good performance, and further assembly with AAO yields a designed architecture composed of vertically aligned, highly ordered nanoarrays on top of the Cu_xO-NPIs film. After biocatalytic precipitation (BCP) was stimulated within the channels, the biosensor was used for the successful detection of ALP activity. This study has not only provided a novel paradigm for an unconventional nanochannels PEC biosensor, which can be used for general bioanalytical purposes, but also indicated that the new concept of nanochannel-semiconductor heterostructures is a step toward innovative biomedical applications.

Emergence of energy harvesting and storage applications is an essential in next generation with electrochemical reactions including ion transport for secondary batteries and electrocatalytic reactions for hydrogen evolution and oxygen reduction. For introducing their high functionality, active materials can be synthesized in micro-/nano-meter scale. Indeed, their exotic phenomena are induced by nanoscale effects in the comparison with the materials in bulk scale. Therefore, one of key issues is to standardize a quantitative technique for nanoscale electrochemical analysis and imaging [1]. Scanning probe microscopies are good candidates for this purpose in resolution. For example, scanning tunneling microscopy and conductive atomic force microscopy can analyze materials at atomic scale precisely. On the other hand, their information is mainly limited to electronic properties which would be indirect information related to their electrochemical properties. In recent years, scanning electrochemical microscopy (SECM) has become popular as a spatially resolved electrochemical analysis. As the challenge for SECM, it is still remained to satisfy the distance control between the sample and probe, sensitivity, spatial and temporal resolution. In this talk, as a family of SECM techniques, we will introduce our scanning electrochemical cell microscopy (SECCM) system with a single barrel nanopipette [2]. The SECCM uses a meniscus as a nanoscale electrochemical cell simulator which created between the sample and nanopipette. Further, our recent progress of nanoscale electrochemical imaging will be presented on battery electrodes and two dimensional materials for electrocatalyst [3-4].

Electrochemical imaging [1] is an emerging technology used to understand localized functions of various materials, because the unique functions of biomaterials, energy materials, and other materials are in many cases based on electrochemical phenomena. Electrochemical imaging is categorized into two basic ways: imaging using micro/nanoelectrode arrays, and scanning micro/nanoelectrochemical probes. In this presentation, I will show the basic outlines and recent progress of nanoscale electrochemical imaging using scanning probes.
Although a scanning electrochemical microscope (SECM) has become popular, the distance control between the probe and sample has still been a big challenge to improve temporal resolution and sensitivity. We adopted voltage-switching mechanisms to attain high resolution bioimaging in SECM systems and applied to simultaneous imaging of topography and electrochemical responses live cells [2]. We also incorporated an ion-conductance feedback for nanoelectrochemical imaging and applied to rapid, non-invasive bioimaging of live cells [3]. This system affords information on dynamic changes of nanostructures of cell membrane surfaces. Capacitive currents can also be used for feedback signal to control the distance. We incorporated this feedback mechanism to develop a nano-scanning electrochemical cell microscope (SECCM) and applied to characterization of localized battery materials with resolution of less than 100 nmm [4]. The technique measures electrode topography and different electrochemical properties simultaneously, and the information can be combined with complementary microscopic techniques to reveal new perspectives on structure and activity. The nanoscale SECCM (NanoSECCM) exhibit highly spatially heterogeneous electrochemistry at the nanoscale, both within secondary particles and at individual primary nanoparticles, which is highly dependent on the local structure and composition. We also applied NanoSECCM to characterize functional 2D materials.

Surfaces and interfaces play a key role in heterogeneous reactions. The electronic and geometric structure of the surface may significantly influence surface reactions. It is important for developing a method to probe the surface structure and the interaction of reactants or products with the active sites at the nanometer scale. In this regard, tip-enhanced Raman spectroscopy (TERS) appears to be an ideal tool.
We demonstrated that TERS can chemically and spatially resolve the site-specific electronic and catalytic properties bimetallic model catalysts of Pd or Pt on Au(111) with a spatial resolution of about 3 nm, using the vibrational fingerprints of phenyl isocyanide (PIC) adsorbed and reacted on the surface. The distinct chemical (electronic) and physical (plasmonic) properties of Pd or Pt steps compared with terraces have been directly visualized.
We further extend TERS to electrochemical systems for studying electrochemical surface and interfacial processes with the unique potential control over the sample. With the designed spectroelectrochemical cell, we were able to synergistically control the reaction by both electrode potential and laser power and characterize the reaction at the nanometer spatial resolution. The plasmon-induced reaction can lead to a reaction region of 30 nm in radius, which equals the mean free path of electron in Au. We further used TERS to characterize the defects of MoS2 with a spatial resolution better than 10 nm and combined electrochemistry to reveal the evolution of the active sites during electrocatalytic processes.

Electrochemiluminescence (ECL), or electrogenerated chemiluminescence, is an electrochemically triggered light-emitting phenomenon. It has been extensively studied in immunoassays, DNA probe assays, aptasensors, enzymatic biosensors, coreactant detection, light-emitting devices, drug screening, and so on. It is one of the most successful electrochemical in vitro diagnostic techniques. Luminophores, coreactants, electrodes, electrocatalysts, quenchers, and microbeads are often used in ECL. These materials have critical effects on ECL performance.
Herein, we reported some new materials with excellent features, such as luminophor ([Ru(bpy)₂dppz]²⁺), coreactant (2-(dibutylamino)ethanol), electrodes (stainless steel electrode and bismuth electrode), noble metal nanocrystal electrocatalyst with high-index facets, single-walled carbon nanohorn ECL quencher, and microbead [1-5].

Hydroxyl radical (•OH) is a very powerful oxidizing agent (E°(•OH/H₂O) = 2.8 V/SHE), second after fluorine. The presence of unpaired electron confers to •OH a very high reactivity towards organic and inorganic compounds, through three action modes established until now: (i) hydrogen abstraction; (ii) electrophilic addition to unsaturated bond; and (iii) electron transfer [1]. Its exceptional oxidation properties have attracted attention in many sectors, and especially in water and wastewater treatment. Thus, hazardous emerging micropollutants such as pesticides, pharmaceuticals, dioxin, etc. are released into the water bodies, being resistant to biodegradation in wastewater treatment plants and in natural waters. Recently, these contaminants have been successfully degraded by •OH involved in the so-called advanced oxidation processes (AOPs). However, •OH has been considered in several studies as unreactive with perhalogenated alkanes (C_xX_y) since they don't have any hydrogen atoms or non-saturated bonds, and they possess a high degree of oxidation due to the electrons of the carbon atoms that are drawn toward the halogen. Interestingly, CCl₄ could be degraded in a Fenton process, while superoxide ion (O2^*-) that is a weak nucleophile and reductant was suggested to be responsible for its degradation; still, the mechanisms of CCl₄ degradation remain unclear. Emerging electrochemical AOPs (EAOPs) offer the advantage to continuously generate •OH in situ in the electrolytic cell according to the electrode materials employed [2]. Excitingly, the implementation of EAOPs highlighted the primary role of •OH radicals for CCl₄ degradation according the ipso-substitution of the radical onto the perhalogenocarbon compound [3]. This new route of •OH oxidation opens up many applications, especially in environmental applications.

Reactive Oxygen Species (ROS) are closely related to various diseases or symptoms. Twendee X (TWX) is an antioxidant composition consisting of Vitamin C, L-Glutamine, L-Cystine or L-Cysteine, Riboflavin, Succinic acid, Fumaric acid, Coenzyme Q10, and Niacin. TWX was invented from the basic experiments of alcohol, glucose, and fat metabolisms (1-4). TWX strongly reduces ROS (Patent: WIPO WO2013/072441 A1, COMPOSITION FOR PROTECTION AGAINST CELL-DAMAGING EFFECTS). Lysozyme radiation experiments showed that antioxidant effects of TWX are 6-7 times higher than Vitamin C (Data from Dr. Helmut Durschschlarg, Regensburg Univ. Germany). Oxidative stress and mitochondrial expert ICDD (France) experiments using hepatic cancer cell line HepG2 showed TWX decreases 63% mitochondrial ROS and increases 147% mitochondrial SOD. ICDD confirmed that TWX is safe and has the strongest anti-ROS and protection effects from ROS. TWX was also shown to increase the Neogenesis nerve cell number of the hippocampal dentate gyrus in the 56 week-old mouse, which was increased to the same as the 6 week-old mouse. Mitochondrial metabolism of the mouse hippocampal dentate gyrus was activated by TWX administration according to metabolome analysis. The Japanese Association for Prevention Dementia started a double blind clinical trial from autumn 2017 for 400 patients with Mild Cognitive Impairment and stroke, to prove TWX prevention effects on Alzheimer's disease and Vascular dementia. TWX effects were monitored in various disease and symptoms.
Monitoring questionnaires was conducted by I’s Corporation (Tokyo), who holds over 100,000 of internet monitoring members in Japan. TWX (13-15 mg/kg/day) was administered to those that suffered from the following disease or symptoms: chronic sinusitis (80 patients), atopic dermatitis (68 patients), asthma (44 patients), pollinosis (107 patients), fatigue (107 patients), etc. All data collected by the website was analyzed by I’s Corporation. A small clinical trial was also conducted for sleep apnea, hepatic disease, hyperthyroidism, diabetes, and stroke. All reports from I’s Corporation are listed on I’s Corporation home page (https://www.eyez.jp/case_reports). The effectiveness and partial effectiveness of TWX in these diseases' symptoms are as follows: chronic sinusitis 78%, atopic dermatitis 80%, asthma 95%, pollinosis 85%, fatigue 80%. Asthma attack numbers were significantly reduced from before TWX administration. All other diseases also showed positive effects. Diabetic peripheral neuropathy patients reported that symptoms disappeared within 8 weeks after start administration of TWX.
TWX has strong potential to treat various disease and symptoms, and its ability to decrease asthma attacks without side effects has presented itself as a major benefit for asthma patients.

Regenerative photoelectrochemical capacitors adapted from an experimental system previously reported (J. E. Halls, J. D. Wadhawan, Energy Environ. Sci., 2012, 5, 6541) and based on the doping of a lamellar lyotropic liquid crystal with visible light sensitizer tris(2,2'-bipyridyl)ruthenium(II), N-methylphenothiazine, zinc(II) ions and potassium chloride (as electrolyte) are examined in this work. The two dye species, by virtue of similarity in redox potentials and difference in size and lipophilicity, allow for electron transfer cascades to occur under illumination, which can be harnessed in a power-generating device through the use of a sacrificial counter electrode. In operation as a solar cell, a maximum light-to-electrical power conversion efficiency is reported as being 5.0% under green light (530 nm centreband, 30 nm bandwidth, 2.2 mW cm-2 intensity), which extrapolates to the opportunistic value of 1% under one Sun conditions. The electrical characteristics of the devices under illumination afford specific capacitances of ca. 2 F g-1 and have fill factors ~20% which are close to the 25% expected for a perfect photogalvanic cell. The time constants of the reported devices (~1 s) are consistent with the notion of electroporation of the surfactant lamellæ. The advantages of these mid-ranging photoelectrochemical capacitors are suggested as being their low cost and versatility afforded by their flexible liquid framework that is able to realign itself under conditions of open circuit.

Methyl Orange is a dye with strong color, used in dyeing and textile printing. When present in effluents, it may contaminate rivers, lakes, and aquifers, causing health risks to living organisms [1]. Textile industries produce large volumes of effluents with high concentrations of dyes, which can become recalcitrant products that are difficult to remove by conventional processes [2]. As an alternative, new technologies have emerged, including heterogeneous phototacalysis, whose principle is based on the irradiation of a semiconductor to the generation of electrons/holes where the reactions of reduction/oxidation occur, favoring the production of hydroxyl radicals (strong oxidizing agent) [3]. The main objective of this work is to degrade the methyl orange dye by photocatalytic processes using a tubular flow reactor containing as photocatalyst nanostructured oxides grown on Ti0.5W alloy. There are few publications in the area of design and construction of flow reactors using nanotube oxides as photoanode [4]. The reactor operated in batch mode with recirculation. The Ti0.5W alloy was prepared in an arc-voltaic furnace, roll processed, and anodized at 120 V for 30 minutes in order to obtain a layer of nanostructured oxide (nanotube form) on alloy surface. As this oxide layer is amorphous, the nanostructures were submitted to heat treatment at 450 °C to obtain a crystalline structure, preferably anatase. The photocatalyst was inserted into the reactor and irradiated by a UV lamp (125 W). The results showed that the processes of photocatalysis and photoelectrocatalysis significantly reduced the absorbance in the visible UV spectrum and the total organic carbon values. However, photoelectrocatalysis presented better performance compared to photocatalysis. In addition, the experiments were carried out at different flow rates, and showed that the increase in flow rate contributes to an increase in the dye removal efficiency.

Photoelectrochemical (PEC) bioanalysis is a newly established analytical approach based on the photo- to-electrical properties of photoactive materials. It possesses many intrinsic advantages such as remarkable sensitivity, simple instrument, and inherent miniaturization. From the combination of photoelectrochemistry and bioanalysis, PEC bioanalysis has advantageously inherited the high sensitivity and specificity. Its general sensing mechanism is that, upon illumination, the photoactive materials could convert the specific biorecognition events into electrical signals, thereby realizing the quantification of various analytes. In past years, the rapid development of PEC bioanalysis has attracted considerable interest, and significant progress has been achieved in its advancement and application. This talk introduces the basic principles, classification, characteristics, as well as the recent progress of PEC bioanalysis in our group.

The localized surface plasmon resonance (LSPR) arises from the collective oscillation of conduction electrons of metal nanostructures, which can be used to monitor recognition events of biomolecules at single nanoparticles [1]. The enhanced electric field around the nanostructures due to LSPR will significantly enhance the Raman scattering, fluorescence, and IR spectra, which enable the realization of single molecule detection. In addition, the LSPR will excite high-energy electron-hole pair (referred to as "hot electrons" and "hot holes") emerging on metal surface. The energetic charges will considerably affect the electrochemical reactions occurring at the nanoparticles. When the plasmonic metallic nanostructures are coupled to other substrates, for example, the semiconductor (i.e., TiO₂, MoS₂) and the plasmon-excited hot electron-hole at nanoparticle surface can communicate with the conductance and valence bands of the semiconductors, resulting in variation in electro/photocatalytic activity. In this talk, we will start with the study on the possibility of LSPR for monitoring biomolecules and their recognition events at single nanoparticles. [1] Then, we report the LSPR enhanced IR for biosensing. [2] In the third part, we will show how the LSPR accelerates electrochemical reactions of electroactive biomolecules, such as glucose on gold nanoparticles and hydrogen evolution reaction at molybdenum disulphide nanosheets. [3] Based on the plasmonics accelerated electrochemical reactions (PAER), high sensitive electrochemical biosensors for detection of glucose and other electroactive biomolecules have been constructed.

Vesicular exocytosis is a key biological mechanism through which cells communicate with each other or with their environment. It is involved in many systems in our body (e.g. nervous, endocrine, digestive, etc.), which makes its understanding of paramount importance from both fundamental and practical points of view. Amperometric measurements of vesicular exocytosis with ultramicroelectrode in artificial synapse configuration [1] provide two important advantages: unsurpassed temporal resolution on emitted fluxes of neurotransmitter during single exocytotic events and possibility to obtain massive data. These two advantages allow statistical analysis of exocytotic events and observe trends in different cell types and/or under various physico-chemical conditions (osmotic shocks, effect of drugs etc.). However, generally statistical analysis is restricted to the examination of some shape features of the amperometric spikes (half-peak time width, charge released etc.) representing individual exocytotic events, even though all relevant physico-chemical parameters are intricately convoluted in the monitored current. Extraction of these thought parameters is extremely difficult, due to the fact that each exocytotic event is unique in terms of vesicle size, its internal composition, neurotransmitter load etc. We developed a theoretical framework providing means to extract statistically sound fusion pore sizes during exocytotic event from individual amperometric spikes [2-3], that is the information hardly accessible or not accessible by other approaches. This permits us to analyze and quantify vesicle pore sizes from amperometric data obtained at bovine chromaffin cells [4].
Recently we dramatically simplified the fusion pore size extraction procedure (without sacrificing its accuracy) so that it can be easily implemented by the experimentalists, e.g. in spreadsheet or general purpose mathematical software. This advance allow us to address a larger data set of spikes obtained at chromaffin cells and reveal statistical changes in fusion pores topology under modified conditions (osmotic stress, modification of cell membrane with exogeneous lipids) with respect to control conditions. Of high interest was the finding that in all considered cases the fusion pore radius was never larger than 30 nm, that is much smaller to the average radius of the chromaffin cell vesicle (156 nm). Taking into account significant size of the data set (more than 1000 spikes) this questions the 'inevitable full fusion' paradigm and statistically support a mode of exocytosis where the pore size is significantly smaller the vesicle size [4].

Earth-abundant transition metal (Fe, Co, or Ni) and nitrogen doped porous carbon electrocatalysts (M-N-C) were synthesized for CO₂ valorization from cheap precursors via silica templated pyrolysis. [1] The effect of the material composition and structure (i.e. porosity, nitrogen doping, metal identity, and oxygen functionalization) on the activity for the electrochemical CO₂ reduction reaction (CO₂RR) in water was investigated. The activity/selectivity order for CO₂-to-CO conversion is Ni > Fe >> Co with respect to the metal in M-N-C. Notably, the Ni doped carbon exhibits a high selectivity with a faradaic efficiency of 93% for CO production. The metal free material exhibits a high selectivity but low activity for the CO₂RR. Tafel analysis shows a change of the rate-determining step as the metal overtakes the role of the nitrogen as the most active site.
Recording of X-ray photoelectron spectra and extended X-ray absorption fine structure demonstrates that the metals are atomically dispersed in the carbon matrix, most likely coordinated to four nitrogen atoms and with carbon atoms serving as a second coordination shell. Presumably, the carbon atoms in the second coordination shell affect the CO₂RR activity, considering that the reactivity order for the central metal in carbon supported metal meso-tetraphenylporphyrin complexes is the opposite. From a better understanding of the relationship between the CO₂RR activity and the material structure, it becomes possible to rationally design high-performance porous carbon electrocatalysts for CO₂ valorization. [2]

Innovative microdevices were designed to monitor electrochemically primary reactive oxygen (ROS) and reactive nitrogen species (RNS) released by populations of aerobic cells. Taking advantage of the space confinement and microelectrodes performances, only few experiments were sufficient to provide significant statistical data relative to the average behavior of cells during oxidative stress bursts.
Platinum-black coated platinum (Pt/Pt-black) electrodes were microfabricated and optimized to achieve optimal performance during the electrochemical detection of four primary species H₂O₂, NO, ONOO^- and NO₂^-.^1,2 The results demonstrated that relative ROS/RNS contents in synthetic mixtures can be easily assessed at selected detection potentials. Under given experimental conditions, the Pt/Pt-black electrodes allow detection limits down to 10 nM with high sensitivities and long-term stability of the electrodes responses.
The electrochemical detection of ROS/RNS released by cell populations was then implemented in a multi-chambers microsystem³ and in a microfluidics device.⁴ As an important cell type, RAW 264.7 macrophages secretion triggered by a calcium ionophore was chosen for assessing the performance, sensitivity and specificity of the detection in both cases. In comparison to some previous evaluations obtained from single-cell measurements, reproducible and relevant determinations could be achieved. However, separating emitting cells from the detection area in the microfluidic device seems to be a better approach to avoid any perturbations of cell behaviors by electrode operations. Furthermore, any biological effects during oxidative stress of living cells can be easily investigated. As a proof of concept, we reported the analysis of the influence of a NO synthase inhibitor during the perfusion culture.

Many electrochemical processes involving self-assembled nanoparticles are subjects of intense research [1]. Most studies use drop casting of nanoparticles on an insulating barrier, however this method has an enormous drawback, since it does not offer control over the deposition process [2]. Here, we used a strategy based on the self-assembly of programmable atom equivalents consisting of AuNps with complementary DNA strands [3] to prepare the self-assembled lattice film on the electrode surface. The investigations of the properties of the films by EIS and CV will be shown. The results reveal how the 3D structure influences the electrical conduction, as well as how the impedance shows that conduction is dependent on the organization and thickness of the superlattice film. The results demonstrating the formation of a hybrid electroactive device with a well-organized structure composed of different nanoscopic entities working together are combined. In this way, we intend to show that our results pave the way for the future development of electrochemically active nanomachines based on DNA nanostructures.

Nearly all kinds of cells within organisms are sensitive to mechanical forces and convert into specific biochemical responses. This important and sophisticated process is described as mechanotransduction. To monitor such presumably transient and weak signaling events from very early stages of mechanotransduction, flexible and stretchable biocompatible electrochemical sensors should offer ideal platforms for applying mechanical strains and monitoring electroactive biochemical responses at the same time. However, to date, despite several stimulating progresses in stretchable physical sensors and very few emerging successes in wearable electrochemical devices, very few breakthrough has emerged for inducing mechanotransduction and investigating it in real-time by a single electrochemical device.
To address this issue, we reported high-performance stretchable electrodes based on interlacing networks of gold nanotubes (Au NTs) or carbon nanotubes (CNTs) deposited on polydimethylsiloxane (PDMS) thin films. This allowed for the first time, real-time electrochemical monitoring of mechanically sensitive cells on the sensor both in their stretching-free and stretching states, as well as sensing of the inner lining of blood vessels. To detect very weak transient signals triggered from cells by stretching strains only, the mechanical and electrochemical performances of stretchable sensor were further enhanced by implementing a percolating CNTs network onto the Au NTs backbones, which allowed monitoring stretch-induced transient release of vasoactive molecules by endothelial cells cultured on this sensor and submitted to stretching strains. Furthermore, by combination of electrochemical sensing materials and nanophotocatalyst, we developed a stretchable and photocatalytically renewable sensor which endows the sensor with excellent electrochemcial performance and high photocatalytic activity, and thereby providing a versatile and efficient way to promote the biomedical applications of stretchable devices in cell and tissue monitoring.

The sustainability of human organs, including the brain, rely on complex networks of connections throughout the body to maintain viability. These networks exchange information using global physical methods— such as temperature, force, blood flow, or point to point electrical signals - such as neuronal impulses, and locally acting chemical signals. Clinicians have traditionally diagnosed disease and treated injury by looking at the overall state of these networks at a point in time— that is, doctors take your temperature, measure your blood pressure, or take a blood sample for analysis. By comparing these individual measurements to the "normal" values of a population, a course of treatment is selected. If required, progress is checked by using a second point measurement.
Advances in computerized instrumentation, and in particular, electroanalytical sensors and biosensors, are allowing us to imagine a different "real-time" medicine where the patient information networks are measured directly and continuously. Injury or disease onset, progression, and treatment can be assessed directly through effects on the measured signals. Such an approach has the great advantage that it takes into account the health of the patient as an individual, and hence offers the possibility of a precise and personalized treatment.
This presentation will use examples from our work to explore how measurement of tissue chemical signals, using electroanalytical devices, can be combined with other real-time measurements to understand injury processes and hence guide treatment.

4-Nitrophenol (4-NP) is a highly hazardous and toxic phenol, which can cause significant damages to the health and to the environment [1,2]. Thus, the interest in its determination in environmental samples has led to the development of several quantification methods. The present work describes the development of a highly sensitive and selective molecularly imprinted electrochemical sensor (MIS) for its detection. The MIS film was prepared in three steps. The first used vinyltrimethoxysilane-modified MWCNTs (MWCNTs-VTMS), a procedure adapted from Correa et al.[3]. Thereafter, VTMS and AIBN were added to the previous mixture (MWCNT- VTMS and DMF). The flask was placed in a thermal oil bath at 70°C, under stirring, for 48 hours. At the second step, for the preparation of the GCE modified with MWCNTs-VTMS, the resulting suspension was dropped onto the GCE surface, and allowed to dry, at room temperature. At last, the imprinted sensor was prepared using the acid catalyzed hydrolysis and condensation of tetraethoxysilane, phenyltriethoxysilane and 3-aminopropyltrimethoxysilane, in the presence of 4-NP as the template molecule and in its absence. For the characterization of the silanes' films, SEM, TGA and FTIR were used. The electrochemical performance of the imprinted siloxane film was characterized by cyclic voltammetry and differential pulse voltammetry. This sensor showed its best performance in 0.1 mol L-1 phosphate buffer solution, at pH 7.0. After optimizing the operational conditions, this sensor provided a linear response range for 4-NP from 0.1 up to 100 mol L-1 and good parameters as LOD (0.03 mol L-1), and sensitivity (1.4 x 10-2 A mol L-1). Furthermore, the MIS/4-NP sensor exhibited good stability with adequate reproducibility and accuracy.

Radioactive waste contains many important elements like cesium ion. Generally, the separation of these elements is expensive and exotic. However, electrically switched ion exchange (ESIX) process is an attractive method for separation, which involves an ion exchange film deposited onto an electrode surface. In this study, a graphite electrode was used; nickel hexacyanocobaltate was introduced into the graphite electrode to improve the capacity for cesium ion separation. X-ray tomography was used to characterize nickel hexacyanocobaltate inside the electrode, and FTIR was used to characterize the prepared material. Cyclic voltammogram was used to measure the ion exchange performance. This technique was found to enhance both the removal capacity of cesium and stability of the ion exchange process compared to other techniques.

In South Africa, industrial development and mining sustains the country's economy. Unfortunately, the effluents from these industries introduce heavy metal pollutants such as lead into the environmental water. Lead(II) is widely recognized as a highly toxic and non-biodegradable metal [1,2,3]. This study addresses a method of monitoring lead(II) by modifying glassy carbon electrode (GCE) with gold nanoparticles (AuNPs) and generation 2 (G2) poly(propyleneimine) dendrimer (PPI), to provide a highly sensitive electrochemical sensor for the determination of lead(II) ions in water using square wave anodic stripping voltammetry (SWASV). The co-deposition of PPI and AuNPs on the surface of GCE was confirmed by field emission scanning microscopy (FESEM). Voltammetric probing showed that the GCE/PPI-AuNP platform exhibited reversible electrochemistry and conductivity in [Fe(CN)6]^3-/4- redox probe. The electroactive surface area of the modified electrodes were also calculated in order to illustrate that the prepared PPI+AuNP nanocomposite could improve the surface area and conductivity of the GCE and was found to be 8.17 mm², GCE-AuNP, 10.84 mm², GCE-PPI, 11.03 mm², while 11.13 mm² was found for GCE-PPI+AuNP. The electroactive surface area of GCE-PPI+AuNP modified electrode increased to approximately 36.23% as compared to bare GCE, which provided an effective evidence for the superior conductivity of PPI+AuNP as expected. The effect of different electrochemical parameters on the sensitivity of the sensor for the Pb2+ detection were also scrutinized, including supporting electrolyte (HNO₃), pH (1), deposition potential (-0.8 V) and deposition time (150s). The sensor was applied in the detection of lead(II) in real water sample and it was exhibited good stability and the results were validated by ICPOES.

Investigations of electrochemical processes involving metal complexes show [1] that, simultaneously with the formation of metal coatings, other side processes can occur on the electrode surface, such as hydrogen evolution or the reduction of semiconductor compounds. Under linear potential sweep (LPS) conditions, all of them can be manifested as current peaks. Various factors can be used for their diagnostics: pH, potential sweep rate, electrochemical quartz crystal microgravimetry (EQCM) data, duration of the system pre-exposure under open-circuit conditions, optical excitation by quanta of different energies, etc. A comparison of the LPS voltammetry and EQCM data can be carried out using time-depending charges q(t) or current densities i(t). The procedures used include integrating the experimental voltammograms or differentiating the EQCM transients. The latter quantities coincide with voltammetric i(t) in the case of metal deposition, show no peak at hydrogen evolution and pass the minumum when surface oxides are reduced. Close inspection of the properties of the experimental peaks shows that these criteria can be successfully used for diagnostics of peak currents based on the indications presented.

Voltammograms of the reduction of metal complexes obtained for ligand-deficient systems have certain features [1]. Steady-state curves contain pre-waves and the splitting of current maximum into two peaks is observed under linear potential sweep (LPS) conditions. Despite of the complex shape, their transformation into linear normalized Tafel plots (NTP) is possible. For this, the following procedures should be followed.
Since the kinetic equations contain the surface concentration of the electrochemically active complex, the current density must be normalized with respect to this value. The latter can be determined using the model of mass transfer of chemically interacting particles [1]. According to it, the total concentrations of the metal, ligand, or proton donors and acceptors obey laws of diffusion; hence, these quantities can be obtained using common procedures. Further, if the system is sufficiently labile, individual surface concentrations are available from the material balance equations with the analytical expressions of stability constants.
Analysis of the LPS voltammograms obtained for the Cu|Cu(II), glycine system is presented. NTPs, close to linear, were obtained for the charge transfer process Cu(II)L⁺ + e = Cu(I)L. The following kinetic parameters were obtained at pH 4: the cathodic charge transfer coefficient α_c = 0.44 and and the exchange current density i₀₁ = 0.14 mA cm^-2.
The method applied can be extended to other electrochemical systems where charge transfer is coupled with chemical steps. A similar analysis of hydrogen evolution on the copper electrode in acetate solutions has been carried out, yielding α_c = 0.76 and i₀ = 0.3 nA cm^-2. Acetic acid acts as a labile proton donor in this case.

Molecules may be considered as electronic systems, with electrons rapidly moving through molecular orbitals and also by long distances in biological metabolism and photosynthesis. The prospect of incorporating molecules into microelectronic circuits based on silicon and metallic conductors has great potential for enhancing consumer electronics, providing solar energy conversion and permitting new functions not possible with silicon. "All-carbon" molecular junctions consist of organic molecules covalently bonded to conducting carbon contacts, which are thermally stable and compatible with practical applications. [1-2] Strong electronic coupling between aromatic molecules and carbon contacts via conjugated bonds results in transport dominated by molecular structure of the interior of the device rather than that of the contacts. Conductance of the molecular junction is strongly dependent on the presence of dihedral angles and interruption of conjugation within the molecular layer, opening the possibility of "rational design" of electronic behavior. An application in a consumer device for electronic music will be described, [3] as will its potentially broader applications in photonics, [4-5] memory, [6-7] and on-chip energy storage. [6] In addition to microelectronic applications, graphene-modified carbon electrodes have unusually high capacitance with both Faradaic and double layer contributions, and may be valuable in supercapacitors used for large scale energy storage. [8]

Conventional batteries function by storing the electrical energy inside solid electrodes, while redox flow batteries (RFBs) are able to store their electrical energy within molecules in solution. RFBs have a number of proposed advantages over conventional batteries; including, (i) the huge number of molecular systems that can potentially be utilized, (ii) the ability to tune the voltage over a wide range, (iii) simple electrode designs that do not change morphologies during charging and discharging, and, (iv) cost-effectiveness for large-scale energy storage. Nevertheless, RFBs suffer several drawbacks in their implementation compared to conventional solid-state batteries, such as their relatively low energy densities due to low molecular solubility, and the increased reactivity of the redox active species. In this study, two fully organic molecular systems were identified that were able to function as the anolyte and catholyte in solution phase batteries. The systems studied were based on modified forms of the naturally occurring vitamin E [1,2] and vitamin K₁ [3]. The systems were chosen because of their suitable reduction (vitamin K₁) and oxidation (vitamin E) potentials measured by cyclic voltammetry, because the compounds had long-lifetimes in their reduced/oxidized states, and because the compounds were highly soluble in acetonitrile containing acid/water. Furthermore, the molecules were found to be able to be utilized in a "mixed-reactant" system were the solutions had exactly the same composition in both compartments (anolyte and catholyte). The lifetime of the reduced forms of vitamin K₁ were affected by the acidity of the solution, which allowed the pH of the solution to be adjusted to allow for the optimal stabilities of the reduced/oxidized quinonoids. Repeated electrolysis experiments in acidified solutions indicated that the systems were fully chemically reversible and so suitable for long-term energy storage applications.