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The state of the art of existing/published work in the prediction of environmental degradation of pesticides by EC-MS/EC-LC-MS coupling was reviewed. Ways to improve EC-MS techniques in the prediction of environmental degradation were proposed.

Small-molecule metabolism has been extensively studied in the past decades, notably driven by the development of new pharmaceutical ingredients. The understanding of metabolism is critical to the anticipation of reactive metabolite formation in vivo that is often associated with toxicity. Electrochemistry has been proposed to simulate the oxidoreductive metabolism reaction catalyzed by cytochrome P450, a family of microsomal enzymes strongly involved in xenobiotic metabolism. The implementation of an electrochemical cell online with mass spectrometry allows for the fast formation and identification of the reaction end products. This study discusses the ability of the synthetic electrochemical approach to simulate a complex lactamization reaction that involves the formation of reactive metabolites. Aristolochic acid I was used as a model molecule to evaluate the ability of electrochemical simulation to generate nitroso, hydroxylamine, N-hydroxylactam, lactam, and nitrenium ion metabolites.

International audience; Mono- and di-anchoring γ-pyranylidene-based organic dyes featuring D–π–A and D–(π–A)2 architectures have been engineered as sensitizers for applications in Dye-Sensitized Solar Cells (DSSCs). Their photophysical, electrochemical and photovoltaic properties were further investigated. TD-DFT calculations were performed to rationalize the trends observed in the optical and electrochemical properties of the dyes. The investigation of the photovoltaic performances of this series of new dyes provided structure–property relationships where their Power Conversion Efficiencies (PCE) could be correlated to structural features, such as the length of the π-conjugated spacer, the nature of the substituents on the pyranylidene electron donor moiety and the number of anchoring groups. Dye-Sensitized Solar Cells based on mono-anchoring dyes were more efficient than the corresponding cells based on di-anchoring analogues due to high dye loading. The highest Power Conversion Efficiency of 5.23% was achieved with the mono-anchoring 17a dye containing t-butyl substituent groups on the pyranylidene fragment and with one thienyl π-conjugated spacer.

The detection of Rhamnolipid virulence factor produced by Pseudomonas aeruginosa involved in nosocomial infections is reported by using the redox liposome single impact electrochemistry. Redox liposomes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine as a pure phospholipid and potassium ferrocyanide as an encapsulated redox content are designed for using the interaction of the target toxin with the lipid membrane as a sensing strategy. The electrochemical sensing principle is based on the weakening of the liposomes lipid membrane upon interaction with Rhamnolipid toxin which leads upon impact at an ultramicroelectrode to the breakdown of the liposomes and the release/electrolysis of its encapsulated redox probe. We present as a proof of concept the sensitive and fast sensing of a submicromolar concentration of Rhamnolipid which is detected after less than 30 minutes of incubation with the liposomes, by the appearing of current spikes in the chronoamperometry measurement.

In vitro and in vivo experimental models, mainly based on cell cultures, animals, healthy humans and clinical trials, are useful approaches for identifying the main metabolic pathways. However, time, cost, and matrix complexity often hinder the success of these methods. In this study, we propose an alternative non-enzymatic method, using electrochemistry (EC) coupled to liquid chromatography (LC) – high resolution mass spectrometry (HRMS) – DFT theoretical calculations (EC/LC-MS/DFT) for the mimicry/simulation of the environmental degradation of phenylurea herbicides, and for the mechanism elucidation of this class of herbicides. Fenuron, monuron, isoproturon, linuron, monolinuron, metoxuron and chlortoluron were selected as relevant model compounds. The intended compounds are oxidized by EC, separated by LC and detected using electrospray ionization HRMS. The main oxidation products were hydroxylated compounds obtained by substitution and addition reactions. Unstable quinone imines/methines, rarely observed by conventional methods, have been identified during the oxidative degradation of phenylurea herbicides for the first time in this study. Some were directly observed and the others were trapped by glutathione GSH. Reactions such as hydrolytic substitutions (−Cl/+OH and −C3H7/+OH and −CH3/+OH and −OCH3/+OH), aromatic hydroxylation, alkyl carbon hydroxylation, dehydrochlorination/dehydromethylation/dehydromethoxylation and conjugation have been successfully mimicked. The obtained results, supported by theoretical calculations, are useful for simulating/understanding and predicting the oxidative degradation pathways of pesticides in the environment.

This work aims to design a high sensitivity and selectivity biosensor based on the electrochemistry of single impacts onto ultramicroelectrode (UME) to detect and identify various bacterial strains. The main objective is to establish a unique electrochemical signature for each bacterial cell through the individual impact event signal on the surface of the UME [1, 2]. First, we focus on the detection of well-known electroactive Gram-negative bacteria such as Shewanella oneidensis in order to be able to selectively detect these different single cells. In this case, the strategy currently used is to record a chronoamperometric curve in an aqueous potassium phosphate buffer (pH = 7.4) solution containing a redox probe at an UME polarized at the oxidation or reduction potential of the electrochemical active aqueous species and to observe a “current step” when one bacterium impacts the UME, corresponding to a “blocking effect” [3] (Figure A). The response signal expected from single bacterium collision may also be a “current spike” corresponding to either the own electrochemical activity of the bacterium toward the redox probe and the UME applied potential or a “bouncing effect” of the bacterium which does not stick onto UME surface (Figure B). In order to be able to identify the type of bacterial cell striking the UME surface, an adapted functionalization (covalent grafting via reduction of diazonium aryl salts) with appropriate affinity (bio)chemical species such as antibodies or aptamers could be performed. This strategy could confer to the UME surface a selectivity of the signal generated during single impacts. For example, the electro-grafting of diazo-pyridinium cations for microbial fuel cell electrodes showed to promote and improve the development of bacterial electroactive films [4]. [1] E. Lebègue, N. L. Costa, R. O. Louro, F. Barrière, J. Electrochem. Soc. 16 (2020) 105501 [2] A. T. Ronspees, S. N.Thorgaard, Electrochimica Acta. 278 (2018) 412-420 [3] G. Guanyue, W. Dengchao, B. Ricardo, Z. Jinfang, M. Michael V. Anal. Chem. 90 (2018) 12123−12130 [4] H. Smida, E. Lebègue, J-F. Bergamini, F. Barrière, C. Lagrost, Bioelectrochemistry. 120 (2018) 157-165 Figure 1

New methods for chemo-selective modifications of peptides and native proteins are important in chemical biology and for the development of therapeutic conjugates. Less abundant and uncharged amino-acid residues are interesting targets to form less heterogeneous conjugates and preserve biological functions. Phenylurazole (PhUr), N-methylphenylurazole (NMePhUr) and N-methylluminol (NMeLum) derivatives were described as tyrosine (Y) anchors after chemical or enzymatic oxidations. Recently, we developed the first electrochemical Y-bioconjugation method coined eY-click to activate PhUr in biocompatible media. In this work, we assessed the limitations, benefits and relative efficiencies of eY-click conjugations performed with a set of PhUr, NMePhUr and NMeLum derivatives. Results evidenced a high efficiency of NMeLum that showed a complete Y-chemoselectivity on polypeptides and biologically relevant proteins after soft electrochemical activation. Side reactions on nucleophilic or heteroaromatic amino-acids such as lysine or tryptophan were never observed during mass spectrometry analysis. Myoglobine, bovine serum albumin, a plant mannosidase, glucose oxidase and the therapeutically relevant antibody trastuzumab were efficiently labelled with a fluorescent probe in a two-step approach combining eY-click and strain-promoted azide–alkyne cyclization (SPAAC). The proteins conserved their structural integrity as observed by circular dichroism and the trastuzumab conjugate showed a similar binding affinity for the natural HER2 ligand as shown by bio-layer interferometry. Compared to our previously described protocol with PhUr, eY-click with NMeLum species showed faster reaction kinetics, higher (complete) Y-chemoselectivity and reactivity, and offers the interesting possibility of the double tagging of solvent-exposed Y., We assessed the relative efficiencies of tyrosine anchors in the electrochemical conjugation of peptides and proteins. Luminol derivatives showed faster reaction kinetics, complete tyrosine-chemoselectivity, and possible double modification.

The single-entity impact method is a very sensitive and powerful electroanalytical tool for biological and environmental purposes such as electrochemical detection of pathogens.[1] The versatility of ultramicroelectrodes (UMEs) gives unique and essential properties for electroanalytical sensing owing to their small size, high sensitivity, fast steady-state response, low double-layer charging current and minimal ohmic loss. The observation of these stochastic events can provide information on various single nanoparticles contrary to ensemble (bulk) measurements. The main advantage of studying collisions of single entities is the low limit of detection (in principle, one single species) inherent to this electroanalytical method and the ability to study single entities (cells, viruses, nanoparticles...) in real time (dynamic measurement).[2–4] Electrochemistry of single redox liposome impacts at an UME consists in detecting the electrolysis of a redox probe encapsulated inside a liposome when it is released at the UME after impact (or collision). The UME is polarized at the oxidation or reduction potential of the encapsulated redox probe and a concentration of several pico-molar of redox liposomes added to the aqueous buffer electrolyte is enough to detect “current spikes” in the chronoamperometry (i-t) curve corresponding to discrete collision events.[3,4] The electron transfer does not readily occur across a lipid bilayer, thus the electrolysis of the liposome redox active content after collision and membrane rupture or opening at the UME surface led to many studies dealing with the membrane permeation mechanism.[3,4] Here, our work is based on the previous results where no current spike was observed in the chronoamperometry curve because the redox DMPC liposomes did not break during impact (or collision) onto the UME surface.[3,4] Hence, the electrochemical sensing principle is based on the weakening of the liposomes lipid membrane upon interaction with a destructive bacterial virulence factor which leads upon impact at an UME to the breakdown of the liposomes and the release/electrolysis of its encapsulated redox probe, as previously reported.[5] In the presence of RL toxin in solution (acting like a surfactant in the lipid membrane), current spikes corresponding to the electrolysis of the encapsulated redox probe released from weakened liposomes are detected (see Figure). Thanks to the redox liposome single impact electrochemistry, the highest detection limit of RL toxin (500 nM) has been reached in comparison to several micromoles per liter previously reported.[5] [1] Lebègue, E.; Costa, N.L.; Louro, R.O.; Barrière, F. Communication—Electrochemical Single Nano-Impacts of Electroactive Shewanella Oneidensis Bacteria onto Carbon Ultramicroelectrode. J. Electrochem. Soc. 2020, 167, 105501, doi:10.1149/1945-7111/ab9e39. [2] Dick, J.E.; Lebègue, E.; Strawsine, L.M.; Bard, A.J. Millisecond Coulometry via Zeptoliter Droplet Collisions on an Ultramicroelectrode. Electroanalysis 2016, 28, 2320–2326, doi:10.1002/elan.201600182. [3] Lebègue, E.; Anderson, C.M.; Dick, J.E.; Webb, L.J.; Bard, A.J. Electrochemical Detection of Single Phospholipid Vesicle Collisions at a Pt Ultramicroelectrode. Langmuir 2015, 31, 11734–11739, doi:10.1021/acs.langmuir.5b03123. [4] Lebègue, E.; Barrière, F.; Bard, A.J. Lipid Membrane Permeability of Synthetic Redox DMPC Liposomes Investigated by Single Electrochemical Collisions. Anal. Chem. 2020, 92, 2401–2408, doi:10.1021/acs.analchem.9b02809. [5] Luy, J.; Ameline, D.; Thobie-Gautier, C.; Boujtita, M.; Lebègue, E. Detection of Bacterial Rhamnolipid Toxin by Redox Liposome Single Impact Electrochemistry. Angew. Chem. Int. Ed. 2021, accepted , doi: 10.1002/anie.202111416. Figure 1

International audience; The influence of the chemical composition on band edges and Fermi level of the Cu2ZnSn(SxSe1-x)4 stoichiometric compounds was investigated. The Cu-poor compounds, Cu1.70Zn1.15SnSSe3 and Cu1.70Zn1.15SnS2Se2, were also studied according to the same approach. As already reported, the absorption threshold increases linearly from 1.05 to 1.48 eV with increasing sulfur content. Simultaneously, the conduction band moves from −4.4 to −3.8 eV respectively, while the position of the uppermost level of the valence bands and the Fermi levels are almost not influenced by the S/Se ratio. In contrast, for Cu-poor compounds, a significant change in the chemical surface composition is witnessed compared to that of the bulk. Moreover, the absorption capability is enhanced without modification of the optical gap. The Cu off-stoichiometry influences also notably the positioning of Fermi level into the band gap. These features could be at the origin for the singular performances of the Cu poor CZTSSe-based solar cell.

International audience; Currently, there is a growing interest in the study of environmental degradation pathways of organic contaminants such as pesticides, with the objective to better understand their potential risk for environmental systems and living organisms. In this context, DFT (conceptual density functional theory) and predictive methods may systematically be used to simplify and accelerate the elucidation of environmental degradation. We report herein the electrochemical behavior/degradation of the carbendazim (CBZ) fungicide widely used to treat cereal and fruit crops. Oxidative degradation of CBZ was studied using an electrochemical flow-through cell directly coupled to a mass spectrometer for rapid identification of CBZ degradation products. The structural elucidation of CBZ oxidation products was based on retention time, accurate mass, isotopic distribution and fragmentation pattern by using LC-HRMS an LC-HRMS2. The most important chemical reactions found to occur in the transformation of CBZ were hydrolysis and hydroxylation. EC-LC-MS and EC-MS analysis has made it possible to highlight the identification of degradation products of CBZ. In addition to previously known transformation products common to those observed during environmental degradation (monocarbomethoxyguanidine, benzimidazole-isocyanate, 2-aminobenzimidazole, hydroxy-2-aminobenzimidazole, hydroxycarbendazim, CBZ-CBZ dimer), two new degradation products were identified in this work: a quinone imine and a nitrenium ion. Electrochemistry mass spectrometry hyphenated techniques represent an accessible, rapid and reliable tool to elucidate the oxidative degradation of CBZ, including reactive degradation products and conjugates.

International audience; The environmental degradation of contaminants such as pesticides can hinder the ability of analytical instruments, even high-performance system such as mass spectrometry, to detect and quantify contamination reliably. There is thus a need for developing synthetic approaches that allow the fast identification of contaminants markers that can be later support quantitative analysis. Combining electrochemical cell (EC), liquid chromatography (LC) and electrospray mass spectrometry (MS) (online EC-MS and offline EC-LC-MS) allows the rapid identification of some oxidation products of diuron (DIU) in the absence and in the presence of glutathione. The structural elucidation of DIU oxidation products was based on retention time, m/z ratio in positive mode and fragmentation pattern. Reactions such as hydrolytic dechlorination, hydroxylation, dehydrochlorination, dehydrogenation/hydrogenation, conjugation and dimerization have been successfully mimicked serving applications such as drug metabolism and environmental degradation simulation. The resort to electrochemistry to simulate naturally occurring reaction has been of particular interest for the production of reactive intermediate species. In this study, quinone imines, highly electrophilic chemical intermediates, have been identified as transformation products during the oxidative metabolism of diuron for the first time. The obtained results, supported by theoretical calculations, are useful for predicting and understanding the oxidative DIU degradation pathway.

International audience; Tandem dye‐sensitized solar cell devices (t‐DSSCs) are a potential alternative to Si‐based solar cells as autonomous power sources. Nevertheless, their further development suffers from the poor quality of the p‐type material, that is, NiO. In this study, N‐doped TiO2 thin films exhibiting a p‐type conductivity (p‐TiO2:N) are successfully grown by co‐reactive magnetron sputtering. Its p‐type conductivity is correlated to the incorporation of N atoms in substitutional positions which is controllable by carefully tuning the ratio between O2 and N2 reactive gases during the growth of the material. Furthermore, it reveals a three to six times higher mobility of the carriers (1.5–3.1 cm2·V−1·s−1) than sputtered NiO. These results are in particular interest for the development of new TiO2‐based t‐DSSCs.

Cu2O@CuO core-shell nanoparticles were synthesized via a facile precipitation-thermal oxidation method consisting in the preparation of Cu2O nanoparticles in solution followed by a post-treatment at 300 °C, 350 °C or 400 °C in air. From HRTEM micrographs, it was evidenced that Cu2O particles were uniformly covered by a 5 nm thick CuO layer to form a core-shell structure. This shell may be viewed as a passivating layer that overcomes the natural chemical instability of Cu2O towards electrolytes for instance. The as-obtained Cu2O@CuO nanoparticles were characterized by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. Both techniques concluded to the p-type conductivity of the Cu2O@CuO hetero-structures. These nanoparticles were then deposited as a film on a FTO glass by screen printing and used after sintering as photocathodes for p-DSSCs. Photovoltaic activity was confirmed with DPP-NDI dye as sensitizer and tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) as redox mediator.

International audience; We report herein the synthesis of nine new molecularly engineered metal-free organic pyranylidene-based dyes as efficient photosensitizers for Dye-Sensitized Solar Cells (DSSCs). Their photophysical, electrochemical, and photovoltaic properties were investigated, and their excited states have been modelled using Time-Dependent Density Functional Theory (TD-DFT). The investigation of the photovoltaic performances of this series of new dyes provided structure-property relationships where their Power Conversion Efficiencies (PCE) could be correlated to structural features, such as the length of the π-conjugated spacer and the nature of the substituents on the upper (positions 2 and 6) and lower parts (substituents on the exocyclic carbon) of the pyranylidene electron donor moiety. While these dyes fulfilled the criteria of efficient sensitizers for TiO2-based DSSCs, their photovoltaic performances were found to depend on the dye packing arrangements controlled by substituents on the pyranylidene group. The highest Power Conversion Efficiency of 5.52% was reached with the 20a dye containing phenyl substituent groups in both upper and lower parts of the pyranylidene fragment and with one thienyl π-conjugated spacer. © 2019 Elsevier Ltd

The control of the surface area enhancement and the ordering of the mesoporous photoanode is one of the key parameters to overcome the current limits of performance of dye sensitized solar cells (DSSCs). These parameters are expected to improve both the concentration of adsorbed dye molecules on the photoanode and the charge collection. In this paper, reactive magnetron sputtering at glancing angle is employed to synthesize nanostructured TiO2 thin films. A post-annealing treatment under an ambient atmosphere at 773 K allows recrystallization of the films to form individual single crystal-like anatase nanocolumns, as shown on a reference structure constituted by well-separated slanted nanocolumns. Even if the best cells provide an open circuit voltage of 0.8 V, a fill factor of 77%, and a short circuit current density of 4.6 mA/cm2 (JSC) and permit to reach an overall efficiency up to 2.6%, it does not yet reach the performances of the reference TiO2 nanoparticle (NP)-based cell. This is explained by a po...

Here we report on the synthesis of binary transition metal nitride electrodes based on titanium vanadium nitride (TiVN) thin films. These films were deposited by a method compatible with micro-electronic processes which consists of DC co-sputtering of vanadium (V) and titanium (Ti) targets. TiVN films with different Ti/V ratio were deposited. A dependence of the capacitance and the cycling stability with the Ti/V atomic ratio in the films was established. While V rich sample exhibits a Faradic behavior that limits its cycling ability despite a high areal and volumetric capacity, the addition of Ti in the film drastically improves the cycling ability with virtually no fade in capacitance after 10,000 cycles. Furthermore, a 1.1 Ti/V ratio leads to an areal capacitance up to 15 mF·cm−2 in 1 M KOH electrolyte solution. Such electrodes shed light on the use of binary transition metal nitrides as candidate electrodes for micro-supercapacitor. Keywords: Micro-supercapacitors, Transition metal nitride, Titanium nitride, Vanadium nitride

International audience; The development of fluorescent organic nanoparticles, serving as bioimaging agents or drug cargos, represents a buoyant field of investigations. Nevertheless, their ulterior fate and structural integrity after cell uptake remain elusive. Toward this aim, we have elaborated original photoactive organic nanoparticles (d TEM ∼ 35−50 nm wide) with an off−on signal upon cellular internalization. Such nanoparticles are based on the noncovalent association of red-emitting benzothiadiazole (BDZ) derivatives and azo dyes, acting as fluorescence quenchers. Upon varying the azo/BDZ ratio, we found that quantitative emission quenching could be obtained with only a 0.2:1 azo/BDZ ratio and originated from exergonic oxidative and reductive photoinduced electron transfer from the azo units (Δ el G 0 = −0.21 and −0.29 eV, respectively). Such results revisited the origin of emission quenching, often confusedly ascribed to Forster resonance energy transfer. A nonlinear and sharp drop of the emission intensity with the increase in the azo unit density n was observed and presents comparable evolution to a n −1/3 mathematical law. Thorough biological examinations involving cancer cells prove a receptor-independent endocytosis pathway, leading to progressive cell lighting upon nanoparticle accumulation in the late endosomal/lysosomal compartments. Complete emission recovery of the initially quenched azo/BDZ nanosystems could be achieved by using mefloquine, which caused endosomal/lysosomal disruption, and release of their content in the cytoplasm. Such results demonstrate that the dotlike emission from endosomes actually stems from fully dissociated individual dyes and not integer nanoparticles. They conclude on the high spatial confinement promoted by organelles and finally question its severe impact on functional compounds or nanoparticles whose properties are strongly distance dependent.

Dye-sensitisation of TiO2 and other metal oxides is an established strategy to couple solar light harvesting with efficient charge separation for the production of electricity in dye-sensitised solar cells (DSCs) or fuels in dye-sensitised semiconductor photocatalysis (DSP). Perylene monoimide (PMI) dyes have emerged as promising organic dyes, but they have not previously been used in a functional assembly with TiO2 in aqueous solution. Here, five novel PMI dyes bearing carboxylic acid, phosphonic acid, acetylacetone, hydroxyquinoline or dipicolinic acid anchoring groups for attachment onto TiO2 are reported. We identified functional DSC and DSP systems with PMI-sensitised TiO2 in aqueous solution, which permitted a side-by-side comparison with respect to performance between the two systems. Structure-activity relationships allowed us to suggest anchor-condition-system associations to suit specific anchoring groups at various pH values, and with different electron mediators (redox couple or sacrificial electron donor) and catalysts in DSC and DSP schemes. A DSC sensitised with the hydroxyquinoline-modified PMI dye reached the highest short-circuit current density (J(SC) approximate to 1.4 mA cm(-2)) in aqueous electrolyte solution during irradiation with simulated solar light. This dye also achieved a turnover number (TONPMI) of approximately 4900 for sacrificial proton reduction after 24 h irradiation in a DSP scheme with Pt as a H-2-evolving co-catalyst at pH 4.5. This performance was only surpassed by the carboxylic acid-bearing dye, which reached a new benchmark turnover number (TONPMI approximate to 1.1 x 10(4) after 72 h) for an organic dye in nanoparticulate DSP for solar fuel production. At higher pH (8.5), our results showed that the phosphonic acid group allows for higher performance due to a stronger anchoring ability. This study provides a platform for aqueous PMI dye-sensitised TiO2 chemistry and gives valuable insights into the performance of different anchoring groups in DSC and DSP systems.

In this study, four new diketopyrrolopyrrole (DPP) sensitizers, with a dicarboxylated triphenylamine anchoring group for attachment to NiO, were prepared and their electronic absorption, emission and electrochemical properties were recorded. The nature of the electronic excited-states was also modeled with Time-Dependent Density Functional Theory (TD-DFT) quantum chemistry calculations. The photovoltaic performances of these new dyes were characterized in NiO-based dye-sensitized solar cells (DSCs) with the classical iodide/triiodide and cobalt(II/III)–polypyridine electrolytes, in which they proved to be quite active. Laser spectroscopy on dye/NiO/electrolyte films gave evidence for ultrafast hole injection into NiO (0.2–10 ps time scales). For the dyes with an appended naphtalenediimide (NDI) acceptor unit, ultrafast electron transfer to the NDI dramatically prolonged the lifetime of the charge separated state NiO+/dye–, from the ps time scale to an average lifetime ≈0.25 ms, which is among the slowest ...

International audience; The development of new bio-orthogonal ligation methods for the conjugation of native proteins is of particular importance in the field of chemical biology and biotherapies. In this work, we developed a traceless electrochemical method for protein bioconjugation. The electrochemically promoted tyrosine-click (e-Y-CLICK) allowed the chemoselective Y-modification of peptides and proteins with labeled urazoles. A low potential is applied in an electrochemical cell to activate urazole anchors in situ and on demand, without affecting the electroactive amino acids from the protein. The versatility of the electrosynthetic approach was shown on biologically relevant peptides and proteins such as oxytocin, angiotensin 2, serum bovine albumin, and epratuzumab. The fully conserved enzymatic activity of a glucose oxidase observed after e-Y-CLICK further highlights the softness of the method. The e-Y-CLICK protocols were successfully performed in pure aqueous buffers, without the need for co-solvents, scavenger or oxidizing chemicals, and should therefore significantly broaden the scope of bioconjugation.

In this work, we report development of hybrid nanostructures of metal nanoparticles (NP) and carbon nanostructures with strong potential for catalysis, sensing, and energy applications. First, the etched silicon wafer substrates were passivated for subsequent electrochemical (EC) processing through grafting of nitro phenyl groups using para-nitrobenzene diazonium (PNBT). The X-ray photoelectron spectroscope (XPS) and atomic force microscope (AFM) studies confirmed presence of few layers. Cobalt-based nanoparticles were produced over dip or spin coated Nafion films under different EC reduction conditions, namely CoSO4 salt concentration (0.1 M, 1 mM), reduction time (5, 20 s), and indirect or direct EC reduction route. Extensive AFM examination revealed NP formation with different attributes (size, distribution) depending on electrochemistry conditions. While relatively large NP with >100 nm size and bimodal distribution were obtained after 20 s EC reduction in H3BO3 following Co2+ ion uptake, ultrafine NP (

The use of electrochemistry (EC) coupled to mass spectrometry (MS) has been widely reported in the past two decades as a tool for simulating drug metabolism. EC-MS is now used to generate metabolites in a simple matrix with easy implementation for high-throughput analysis. Another interesting use of EC in drug-metabolism investigation is simulation of the formation of reactive drug metabolites. Electrochemical reactions tend to be limited to the simulation of single-electron transfers initiated by cytochrome P450 reactions, hence the need for new analytical developments. This review aims to describe current knowledge of the use of EC-MS for the generation and the identification of reactive drug metabolites. We detail the electrochemical formation of electrophilic aryl, nitroso, aromatics and nitrogen-oxide species in the first part. We give future perspectives related to the surface-modified electrode coupled with MS for inhibition.

Rationale Electrochemistry (EC) coupled to mass spectrometry (MS) has been used to study different phase-I reactions. Despite of the versatility of EC/MS, the effect of the nature of the supporting electrolyte on the formation of oxidation products has seldom been discussed during EC/MS experiments. Here, we present a comparison of two different supporting electrolytes and their effect on the identification of unstable intermediate oxidation species is discussed. Methods The oxidation of acebutolol was performed with a coulometric cell in the presence of two supporting electrolytes namely ammonium acetate and lithium acetate. Ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/QTOFMS) using a binary gradient (water/acetonitrile) with positive electrospray ionization was used to identify the oxidation products in the presence and absence of glutathione. Chemical structure elucidations of the oxidation products were performed by high-resolution mass spectrometry (HRMS) and were also supported by nuclear magnetic resonance (NMR) measurements. Results From the electrochemical study and HRMS measurements, we demonstrate that the quinoneimide species resulting from the oxidative hydrolyses of acebutolol gives a benzimidazole ring product in the presence of ammonium acetate. Through the example of the oxidation of acebutolol, a correlation between the supporting electrolyte nature and oxidation product formation was established. The obtained results were supported by quantum mechanical calculations. Conclusions We present here evidence of the side reactions induced by the presence of ammonia as supporting electrolyte during EC/MS measurements. Acebutolol was used as a model to postulate an uncommon and unexpected side reaction leading to benzimidazole ring formation. The findings may help to understand the identification of the intermediate species in the oxidative degradation process. Copyright © 2015 John Wiley & Sons, Ltd.

Layered LaOCuS oxysulfide is a well-known wide band gap p-type semiconductor that has attracted strong interests for transparent electronics. We report here that nanoparticles of this material can also be used as a substitute for the widely used NiO compound to fabricate photocathodes for p-type dye sensitized solar cells.

International audience

International audience; To prevent the interfacial charge recombination between injected holes in the valence band and the redox mediator in the electrolyte in p-type dye sensitized solar cells (p-DSSC) the passivation of the recombination sites by organic insulator chenodeoxycholic acid (CDCA) layer is critically investigated in this study. Rather than classical coating of the semiconductor's surface by simultaneous co-adsorption of CDCA during the dyeing step, two other methods were investigated. The first consists in dissolving CDCA in the electrolyte, while the second consists in spin coating an ethanol solution of CDCA onto the already dyed photocathode. In 2 this study different sensitizers, electrolytes and p-SCs, (NiO, CuGaO2) were explored. Analysis of the current/voltage curves and electrochemical impedance spectroscopy provides evidence that the role of the CDCA layer is to create a physical barrier to prevent the approach of the redox mediator from the NiO surface and consequently raise the Voc. The important finding of this study is the demonstration that the Voc in p-DSSC is heavily limited by interfacial charge recombination and that higher Voc values much above 100 mV and as high as 500 mV can be attained with conventional materials (NiO) if this deleterious side reaction can be suppressed or diminished.

International audience; Nickel carbodiimide (NiCN) was synthesized using a two-step precipitation-decomposition route leading to a brown powder with gypsum-flower-like morphology and a large specific surface area (75 m/g). This layered material crystallizes in the 2H structure type of delafossite (space group P6/mmc), which is built upon infinite /[NiN] layers connected by linear carbodiimide ([N═C═N]) bridges. An X-ray diffraction Rietveld refinement and thermal analyses pointed out some nickel deficiencies in the material, and band structure calculations carried out on the defect compound predicted p-type conductivity in relation to a slight amount of N. This p-type conductivity was demonstrated by electrochemical impedance spectroscopy measurements, and a flat band potential of 0.90 V vs SCE at pH 9.4 was measured. This value, which is more positive than those of CuGaO and CuCrO delafossite oxides and NiO, prompted us to test NiCN nanoparticles as a photocathode in p-type dye-sensitized solar cells.

ANR is gratefully acknowledged for the financial support of these researches through the QuePhelec project (n° ANR-13-BS10-0011-01). Région des Pays de la Loire and Nantes University for the project LUMOMAT are also acknowledged. We acknowledge support from the European Research Council (grant number 321305) and the EPSRC (grant number EP/L017008/1). IDWS is a Royal Society Wolfson Research Merit award holder. The research data supporting this publication can be accessed at http://dx.doi.org/10.17630/ddaebfb9-e127-43cb-9048-966a572b50ac. Quantum dots (QDs) are very attractive materials for solar cells due to their high absorption coefficients, size dependence and easy tunability of their optical and electronic properties due to quantum confinement. Particularly interesting are the PbS QDs owing to their broad spectral absorption until the long wavelengths, their easy processability and low cost. Here, we used control of the PbS QDs size to understand charge transfer processes at the interfaces of NiO semiconductor and explain the optimal QDs size in photovoltaic devices. Towards this goal, we have synthesized a series of PbS QDs with different diameters (2.8 A until 4A) and investigated charge transfer dynamics by time resolved spectroscopy and their ability to act as sensitizers in nanocrystalline NiO based solar cells using the cobalt tris(4,4'-diterbutyl-2,2'-bipyridine) complex as redox mediator. We found that PbS QDs with average diameter of 3.0 nm are optimal size in terms of efficient charge transfers and light harvesting efficiency for photovoltaic performances. Our study showed that an hole injection from PbS QDs to NiO valence band (VB) is an efficient process even with low injection driving force (0.3 eV) and occurs in 6-10 ns. Furthermore we found that the direct electrolyte reduction (photoinduced electron transfer to the cobalt redox mediator) also occurs in parallel to the hole injection with rate constant of similar magnitude (10-20 ns). In spite of its large driving force, the rate constant of the oxidative quenching of PbS by Co(III) diminishes more steeply than hole injection on NiO when the diameter of PbS increases. This is understood as the consequence of increasing the trap states that limit electron shift. We believe that our detailed findings will advance the future design of QD sensitized photocathodes. Postprint

A highly stable copper(I) complex was obtained starting from a copper(II) salt. This compound was characterized by a combination of several analytical techniques (UV/Vis spectroscopy, energy-dispersive X-ray spectroscopy, electrochemistry, and X-ray photoelectron spectroscopy) and was shown to present an N4Cu structure. These results were confirmed by a density functional calculations study of the binding energy and the electronic structure of model ligand and copper complexes. Preliminary tests of complexation showed a high ability of the corresponding ligand to chelate 64Cu in very diluted medium, which is of interest for developing new positron emission tomography imaging agents. The stability and the kinetic inertness of the complex are promising. In particular, it displayed good redox stability, which is important because in vivo reduction or oxidation of the copper of Cu complexes can lead to demetalation. The rapid microwave-assisted strategy used to synthesize the ligand was applied to the synthesis of more than ten ligands. One of these was functionalized by an amino group to form a bifunctional chelate for a future bioconjugation for applications in nuclear medicine.

International audience; Transparent C, Au and Pt films with thickness in the 5-10 nm range have been deposited by a DC magnetron sputtering system on commercial ITO (indium tin oxide) coated glass substrate for evaluation as electrode of spectro-electrochemical transducer. The transmission, over the investigated spectral range, is superior to 55% with the best transmission values obtained for C films (higher than 80%). The deposited films have been characterized by AFM, XPS and electrochemical methods. Results showed a low roughness, improved in comparison with uncoated electrodes. Electrochemical properties of the Au and Pt films evidenced a metallic behavior, which allowed qualifying them as conductive optically transparent electrodes for spectro-electrochemical devices.

A comparative study of the electrochemical conversion and the biotransformation performed by the cytochrome P450 (CYP450) obtained by rat liver microsomes has been achieved to elucidate the oxidation mechanism of both acebutolol and alprenolol. For this purpose, a wide range of reactions such as N-dealkylation, O-dealkoxylation, aromatic hydroxylation, benzyl hydroxylation, alkyl hydroxylation, and aromatic hydroxylation have been examined in this study, and their mechanisms have been compared. Most of the results of the electrochemical oxidation have been found to be in accordance with those obtained by incubating acebutolol and alprenolol in the presence of CYP450, i.e., N-dealkylation, benzyl hydroxylation, and O-dealkoxylation reactions catalyzed by liver microsomes were found to be predicted by the electrochemical oxidation. The difficulty for the electrochemical process to mimic both aromatic and alkyl hydroxylation reactions has also been discussed, and the hypothesis for the absence of aromatic hydroxylated and alkyl hydroxylated products, respectively, for alprenolol and acebutolol, under the anodic oxidation has been supported by theoretical calculation. The present study highlights the potential and limitation of coupling of electrochemistry-liquid chromatography-high-resolution mass spectrometry for the study of phase I and phase II reactions of acebutolol and alprenolol.

In situ NMR spectroelectrochemistry is presented in this study as a useful hybrid technique for the chemical structure elucidation of unstable intermediate species. An experimental setting was designed to follow the reaction in real time during the experimental electrochemical process. The analysis of (1)H NMR spectra recorded in situ permitted us (1) to elucidate the reaction pathway of the electrochemical oxidation of phenacetin and (2) to reveal the quinone imine as a reactive intermediate species without using any trapping reaction. Phenacetin has been considered as hepatotoxic at high therapeutic amounts, which is why it was chosen as a model to prove the applicability of the analytical method. The use of 1D and 2D NMR experiments led to the elucidation of the major species produced from the oxidation process. We demonstrated that in situ NMR spectroelectrochemistry constitutes a fast way for monitoring unstable quinone imines and elucidating their chemical structures.

International audience; Unintentional nitrogen doped carbon nanowall (CNW) films were oxidized through anodic polarization in different applied potential windows, in a mild neutral K2SO4 electrolyte solution. Applied potentials in the range of [0-1], [0-1.5] and [0-2] V vs. SCE were explored. The films were characterized with X-ray photoelectron (XPS) and Micro-Raman spectroscopy, in order to investigate the surface chemistry and structural changes after treatment, respectively. The XPS analysis revealed that this electrochemical treatment leads to an increase of oxygen functional groups, and influences the nitrogen proportion and bonding configuration (such as pyridinic/pyridonic nitrogen) on the film surface at room temperature. In particular, an obvious enhancement of pyrrolic/pyridonic nitrogen doping of CNWs via electrochemical cycling in the range of [0-1.5] and [0-2] V vs. SCE was achieved. Such enhancement happened, because of the oxidation of nitrogen atoms in pyridine as a result of OH ions injection upon electrochemical cycling. Micro-Raman analysis indicates structural quality degradation with increasing the applied potential window. Moreover, the electrochemical capacitance of CNW films was increased after treatment in the range of [0-1] and [0-1.5] and decreased in the range of [0-2] V vs. SCE. The results show that harsh oxidation happened in the range [0-2] V.

Sensitized NiO based photocathode is a new field of investigation with increasing scientific interest in relation with the development of tandem dye-sensitized solar cells (photovoltaic) and dye-sensitized photoelectrosynthetic cells (solar fuel). We demonstrate herein that PbS quantum dots (QDs) represent promising inorganic sensitizers for NiO-based quantum dot-sensitized solar cells (QDSSCs). The solar cell sensitized with PbS quantum dot exhibits significantly higher photoconversion efficiency than solar cells sensitized with a classical and efficient molecular sensitizer (P1 dye = 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid). Furthermore, the system features an IPCE (Incident Photon-to-Current Efficiency) spectrum that spreads into the infra-red region, reaching operating wavelengths of 950 nm. The QDSSC photoelectrochemical device works with the complexes tris(4,4′-ditert-butyl-2,2′-bipyridine)cobalt(III/II) redox mediators, underscoring the formation of a long-lived charge-separated state. The electrochemical impedance spectrocopy measurements are consistent with a high packing of the QDs upon the NiO surface, the high density of which limits the access of the electrolyte and results in favorable light absorption cross-sections and a significant hole lifetime. These notable results highlight the potential of NiO-based photocathodes sensitized with quantum dots for accessing and exploiting the low-energy part of the solar spectrum in photovoltaic and photocatalysis applications.

Nanoporous materials are of great interest for various technological applications including sensors based on surface-enhanced Raman scattering, catalysis, and biotechnology. Currently, tremendous efforts are dedicated to the development of porous one-dimensional materials to improve the properties of such class of materials. The main drawback of the synthesis approaches reported so far includes (i) the short length of the porous nanowires, which cannot reach the macroscopic scale, and (ii) the poor organization of the nanostructures obtained by the end of the synthesis process. In this work, we report for the first time on a two-step approach allowing creating highly ordered porous gold nanowire arrays with a length up to a few centimeters. This two-step approach consists of the growth of gold/copper alloy nanowires by magnetron cosputtering on a nanograted silicon substrate, serving as a physical template, followed by a selective dissolution of copper by an electrochemical anodic process in diluted sulfuric acid. We demonstrate that the pore size of the nanowires can be tailored between 6 and 21 nm by tuning the dealloying voltage between 0.2 and 0.4 V and the dealloying time within the range of 150-600 s. We further show that the initial gold content (11 to 26 atom %) and the diameter of the gold/copper alloy nanowires (135 to 250 nm) are two important parameters that must carefully be selected to precisely control the porosity of the material.

Graphical abstract, Hydroxyapatite/titania nanocomposites (TiHAp) were synthesized from a mixture of a titanium alkoxide solution and dissolution products of a Moroccan natural phosphate. The simultaneous gelation and precipitation processes occurring at room temperature led to the formation of TiHAp nanocomposites. X-ray diffraction results indicated that hydroxyapatite and anatase (TiO2) were the major crystalline phases. The specific surface area of the nanocomposites increased with the TiO2 content. Resulting TiHAp powders were assessed for the removal of the patent blue V dye from water. Kinetic experiments suggested that a sequence of adsorption and photodegradation is responsible for discoloration of dye solutions. These results suggest that such hydroxyapatite/titania nanocomposites constitute attractive low-cost materials for the removal of dyes from industrial textile effluent.

We report on a novel fabrication approach of metal nanowires with complex surface. Taking advantage of nodular growth triggered by the presence of surface defects created intentionally on the substrate as well as the high tilt angle between the magnetron source axis and the normal to the substrate, metal nanowires containing hillocks emerging out of the surface can be created. The approach is demonstrated for several metals and alloys including gold, copper, silver, gold–copper and gold–silver. We demonstrate that applying an electrochemical dealloying process to the gold–copper alloy nanowire arrays allows for transforming the hillocks into ring-like shaped nanopores. The resulting porous gold nanowires exhibit a very high roughness and high specific surface making of them a promising candidate for the development of SERS-based sensors.

In p-type dye-sensitized solar cells (p-DSSCs), NiO is the most commonly used p-type semiconductor. Nevertheless, because of the drawbacks of NiO, much effort has been made to search for suitable substitutes. Herein, three different morphologies of CuO nanomaterials were used to prepare photocathodes for p-DSSCs, which have a deeper valence band and a higher dielectric constant compared to that of NiO. We observe that CuO is unstable in the presence of iodide/triiodide electrolyte, while cobalt complexes with bipyridine ligands are more suitable redox shuttles. We also note that the average transport time in CuO is shorter than that in NiO. Finally, the deep absorbance of CuO in the visible range indicates that suitable sensitizers for the CuO p-DSSC must exhibit high extinction coefficient and absorption bands located in the lower energy part of the solar spectrum (>600 nm) to be exploitable. In this case such CuO based photocathodes represent valuable systems to exploit the near-infrared (NIR) region.

p-Type dye-sensitized solar cells (p-DSSCs) have recently become a major research focus because coupling with n-type DSSCs yields highly efficient tandem DSSCs. Indeed many delafossite-like compounds appear as promising candidates for p-DSSCs due to their deep valence band position and high hole mobility. In this paper, the synthesis of CuBO2 was attempted by a facile sol–gel methodology. Then, the as-obtained particles were used to prepare photocathodes for p-DSSCs with DPP-NDI dye as sensitizer and tris(4,4′-di-tert-butyl-2,2′-bipyridine)cobalt(III/II) as redox mediator. Due to the deeper valence band position compared with classical NiO photocathode, the “CuBO2” based p-DSSC presents an open-circuit photovoltage (Voc) of 453 mV, which is 150 mV higher than that of NiO in the same conditions. The results show that “CuBO2” is a potential alternative for NiO in p-DSSCs.

The electrochemical behavior of Acebutolol was examined by cyclic voltammetry and coulometry. The products of Acebutolol oxidation were then characterized by liquid chromatography (LC) and mass spectrometry (MS). An aromatic ether cleavage reaction was observed and various intermediate species were identified. In the presence of glutathione, a series of glutathione adducts were identified enabling possible oxidation pathways of Acebutolol to be established. The obtained results are useful for predicting and understanding the oxidative Acebutolol degradation pathway.

International audience; In this contribution, we investigate the photovoltaic performances of four ruthenium trisbipyridine complexes in NiO based dye-sensitized solar cells (DSSC). The four complexes differ by the nature of the anchoring groups, which are either carboxylic acids, biscarbodithioic acids catechol or methyl phosphonic acids. The properties of the dyes were studied by electrochemistry, absorption and emission spectroscopies, surface binding measurements, time-dependent density functional theory (TDDFT) as well as by determining their photoconversion efficiencies in DSSCs under AM 1.5. We show that these simple dyes are relatively efficient sensitizers in NiO-based DSSCs, since some of them give photoconversion efficiencies comparable to that of a standard benchmark dye coumarin C343. We also demonstrate that both catechol and methyl phosphonic acid are promising binding groups for NiO sensitizers to replace classical carboxylic acids in NiO sensitizers and finally we report molecular design rules to elaborate a new generation of better performing ruthenium polypyridine sensitizers.

A screen-printed carbon electrode modified with tyrosinase (SPCE-Tyr/Paa/Glut) has been developed for the determination of phenol concentration in real samples. The resulting SPCE-Tyr/Paa/Glut was prepared in a one-step procedure, and was then optimized as an amperometric biosensor operating at 0 mV versus Ag/AgCl for phenol determination in flow injection mode. Phenol detection was realized by electrochemical reduction of quinone produced by tyrosinase activity. The possibility of using the developed biosensor to determine phenol concentrations in various smoked products (bacon, ham, chicken and salmon) was also evaluated. Gas chromatography (GC) method was used for result validation obtained in flow injection mode using amperometric biosensor. The result showed good correlation with those obtained by flowinjection analysis (FIA).