bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrosynthesis of Highly Functionalized N,N-Diarylamides and Selective Functionalization of Caffeine Via Electrochemically Generated HFIP Ethers
Authors: Dörr Maurice , Lips Sebastian , Röckl Johannes , Waldvogel Siegfried R.
Published: May 2020

Most cross-coupling reactions make use of transition metal-based catalysts and require prefunctionalization or an excess of oxidizers. This results in large quantities of partially toxic reagent waste. By anodic cross-coupling via the oxidation of phenols, those drawbacks are avoided.[1] Utilizing simple undivided cells, a safe and sustainable protocol for the synthesis of highly functionalized N,N-diarylamides was presented. This involves the hydrolysis of the initially formed hydrobenzoxazolo-[2,3-b]benzoxazole during a simple work-up procedure.[2] The resulting N,N-Bis(2-hydroxyphenyl)amides are of special interest for the synthesis of crown ethers[3] and biologically active compounds.[4]

Derivatives of caffeine showed biological activities in the past.[5] The selective functionalization of caffeine was now achieved by electrochemically generating the corresponding hexafluoroisopropyl ether and thereby activating it for subsequent metal-catalyzed cross-coupling reactions. Using a “Design of Experiments” approach (DoE) for the optimization of the initial step, detailed information about the system was gathered. This led to the implementation of a fast and selective electrolysis.

[1] A. Wiebe, T. Gieshoff, S. Möhle, E. Rodrigo, M. Zirbes, S. R. Waldvogel, Angew. Chem. Int. Ed.
2018, 57, 5594–5619; Angew. Chem.
2018,
130, 5694–5721.

[2] M. Dörr, S. Lips, C. A. Martínez-Huitle, D. Schollmeyer, R. Franke, S. R. Waldvogel, Chem. Eur. J.
2019, 25, 7835–7838.

[3] a) T. Németh, A. Kormos, T. Tóth, G. T. Balogh, P. Huszthy, Monatsh. Chem.
2015, 146, 1291–1297; b) S. Lakatos, J. Fetter, F. Bertha, P. Huszthy, T. Tóth, V. Farkas, G. Orosz, M. Hollósi, Tetrahedron
2008, 64, 1012–1022.

[4] M. Farkas, G. Láng, Z. Dinya, P. Sohár, L. Rózsa, Z. Sudai, J. Mol. Struct.
1985, 131, 131–140.

[5] a) J. Pretorius, S. F. Malan, N. Castagnoli, J. J. Bergh, J. P. Petzer, Bioorganic & medicinal chemistry
2008, 16, 8676–8684; b) D. E. Guttman, A. E. Gadzala, Journal of pharmaceutical sciences
1965, 54, 742–746.

Figure 1
Anodic Oxidation of 9,9'-Spiro-Bifluorenes Containing C, Si, Ge and Sn as the Central Elements
Authors: Becker James Y.
Published: May 2020

Previously we investigated [1] the electrochemical properties of various 2,3,4,5-tetraphenylsiloles (I) with different substituents attached to the Si atom. Major products include 1,2-dibenzoyl, 1,2-diphenylethene, tetraphenylfuran and tetraphenyldihydrofuran.

Later [2] we explored the redox properties of four silafluorenes of type (II). Major products after CPE involve both aromatic hydrocarbons and siloxane derivatives.

Recently [3] we studied the electrochemical redox properties of four spiro-derivatives (III) in which the central atom is C, Si, Ge or Sn, both by cyclic voltammetry and controlled potential electrolysis. The outcome from these measurements will be presented in this talk. It is noteworthy to indicate that each spiro derivative afford different products.

References

[1] A. Dhiman, Z.-R. Zhang, R. West, J. Y. Becker, J. Electroanal. Chem.,
2004, 569,

15-22; A. Dhiman, Z.-R. Zhang, R. West, J. Y. Becker, J. Electroanal. Chem.,
2004,

573, 139-146.

[2] A. C. Herath, R. West, J.Y. Becker, J. Electroanal. Chem., 2014, 728, 118-122.

[3] T. Golub-Sedinkin, A. C. Herath, R. West, and J. Y. Becker, ChemElectroChem
,

2019, 6, 1–6.

Figure 1
Electrochemical Oligopeptide Synthesis Assisted By a Soluble Tag Method
Authors: Nagahara Shingo , Okada Yohei , Chiba Kazuhiro
Published: May 2020

Recently, peptides have attracted much attention as the medicinal candidates with higher specificity and lower side effects than small molecular medicines. Peptides have been synthesized using stoichiometric amount of coupling reagents. While these reagents enable quantitative reaction, stoichiometric byproducts from coupling reagents cause poor atom economy. In this context, “General methods for catalytic/ sustainable (direct) amide or peptide formation” is selected as one of the top research area in green chemistry. [1]

To solve the problem, we are aiming to establish a method of electrochemical oligopeptide synthesis and recycle coupling reagents. Inspired by the report of Uribe’s group, [2] we selected triphenylphosphine (TPP) as the coupling reagent in electrochemical peptide bond formation. Although triphenylphosphine oxide (TPPO) is generated as the stoichiometric byproduct, reduction of TPPO to TPP are achieved in various ways. [3] Therefore, TPP can be a recyclable coupling reagent in peptide synthesis and this lead to reduce the amount of waste. In addition, we employed soluble tags as protecting group of carboxylic acids, which are consisted of benzyl group with long alkyl chain and precipitate in polar solvents, to make purification easier. [4]

Until now, we have succeeded quantitative electrochemical peptide bond formation. Notably, we found that soluble tag serves to prevent undesired oxidation of amino acids maybe because long alkyl chain of soluble tag keep amino acids away from electrode. Work to synthesis bioactive oligopeptides is in progress.

Reference

[1] M. C. Bryan, P. J. Dunn, D. Entwistle, F. Gallou, S. G. Koenig, J. D. Hayler, M. R. Hickey, S. Hughes, M. E. Kopach, G. Moine, P. Richardson, F. Roschangar, A. Steven and F. J. Weiberth, Green Chem., 2018, 20, 5082-5103.

[2] A. Palma, J. Cardenas and B. A. Frontana-Uribe, Green Chem., 2009, 11, 283–293.

[3] Y. Okada, H. Suzuki, T. Nakae, S. Fujita, H. Abe, K. Nagano, T. Yamada, N. Ebata, S. Kim, and K. Chiba, J. Org. Chem., 2013, 78, 320−327.

[4] D. Hérault, D. H. Nguyen, D. Nuel and G. Buono, Chem. Soc. Rev., 2015,
44
, 2508-2528.

Figure 1
Fabrication of TiO2-WO3 Nanopillars for Alcohol Oxidation
Authors: Parihar Amritdev , Hosseini Seyyedamirhossein , Peters Dennis G.
Published: May 2020

Ethanol, the major component of biofuel mixture, has significantly lower heat capacity compared to that of longer-chain alcohols such as butanol. As a result, oligomerization of ethanol has gained much attention. This three-step process includes: (I) alcohol oxidation to the corresponding carboxylic acid, (II) dimerization via carboxylic acid terminals, and (III) further reduction of the oligomer to form the saturated alcohol.1 In this context, TEMPO has been vastly utilized for the electrochemical oxidation of alcohols, but this process suffers from shortcomings such as limited turnover frequency of the reagent and small conversion yield of the synthesis.2 There have been some reports on the application of semiconductor electrodes for oxidizing certain types of alcohols. This approach, however, has shown some pitfalls such as high oxidation overpotential, low reaction yield, and low stability of the working electrode.3

The goal of this research is to fabricate a novel photoanode for oxidizing alcohols to their corresponding carboxylic acids. In this work, we aimed at fabricating an ordered array of TiO2 nanopillars decorated with WO3 nanoparticles. To prepare such an electrode, silicon oxide nanospheres (SONS) were deposited onto a silicon wafer covered with a 5-nm layer of gold. Then, TiO2 was electrodeposited into the empty hexagonal spaces resulting from SONS forming a tight-packed structure. Subsequently, SONS were washed away and a layer of WO3 was electrodeposited. Our experimental results have shown a homogeneous deposition of the WO3 layer when 60-ms symmetrical pulse cycles of potential (-0.5 V vs. SCE) were applied for 50 min.

References

1. Fu, S.; Shao, Z.; Wang, Y.; Liu, Q. Manganese-Catalyzed Upgrading of Ethanol into 1-Butanol. J. Am. Chem. Soc. 2017, 139, 11941-11948.

2. Rafiee, M.; Miles, K. C.; Stahl, S. S. Electrocatalytic Alcohol Oxidation with TEMPO and Bicyclic Nitroxyl Derivatives: Driving Force Trumps Steric Effects. J. Am. Chem. Soc. 2015, 137, 14751-14757.

3. Hitmi, H.; Belgsir, E. M.; Léger, J.; Lamy, C.; Lezna, R. O. A Kinetic Analysis of the Electro-Oxidation of Ethanol at a Platinum Electrode in Acid Medium. Electrochimica Acta. 1994, 39, 407-415.
Visible Light-Driven Catalytic Reaction Catalyzed By the B12-Rhodium-Titanium Oxide Hybrid Catalyst
Authors: Shimakoshi Hisashi , Shichijo Keita , Hisaeda Yoshio
Published: May 2020

Organometallic B12 compounds are unique metal complexes having a cobalt-carbon σ-bond present in biological systems [1]. Cleavage of the metal-organic σ-bond initiates many B12 dependent enzymatic reactions. Based on unique properties of B12 enzymes, many B12-inspired reactions were developed [2]. Here we report the visible light-driven new B12 inspired reaction for the fine chemical synthesis [3]. The hybrid catalyst composed of the B12 complex and rhodium ion modified titanium oxide was synthesized for the visible light-driven B12 inspired reaction. Visible light irradiation (λ≧420 nm) of the hybrid catalyst in the presence of a sacrificial reagent showed absorption at 390 nm, typical for the Co(I) state of the B12 complex monitored by diffuse reflectance UV-vis analysis, which imply that electron transfer from the titanium oxide to Co(III) center of the B12 complex occurred by the visible light irradiation. Benzotrichloride was converted to N,N-diethylbenzamide by the visible light irradiation in the presence of triethylamine catalyzed by the hybrid catalyst in air at room temperature. Both the conduction band electron and valence band hole of the catalyst were utilized for the reaction to form the amide product. The reaction mechanism of the duet reaction was proposed. The B12-inspired photocatalyst shown here can be used for the sustainable production of fine chemicals with the possible expense of energy economy.

[1] Review: H. Shimakoshi, Y. Hisaeda, Current Opinion in Electrochem. 2018, 8, 24.

[2] K. Proinsias, A. Jackowska, K. Radzewicz, M. Giedyk, D. Gryko, Org. Lett., 2018, 20, 296.

[3] K. Shichijo, M. Fujitsuka, Y. Hisaeda, H. Shimakoshi, J. Organomet. Chem. 2020, in press.

Figure 1
Shifts of pNIPAM Lower Critical Solution Temperature in an Applied Electric Field
Authors: Halpern Jeffrey M , Roberge Emma , Ren Tianyu , LaFreniere Joelle , Balog Eva Rose M , Seitz William Rudolf
Published: May 2020

Poly(N-isopropylacrylamide), or pNIPAM, is a free-radical polymer that is commonly studied for uses in surface coatings, tissue engineering, energy storage, biosensing, and more, due to its temperature responsiveness. Below its transition temperature, pNIPAM is dissolved in solution with a small particle size. Above the transition temperature, pNIPAM agglomerates and condenses out of solution. Dynamic Light Scattering (DLS) measures temperature induced agglomeration of pNIPAM by determining the transition temperature, which is typically 30-35oC for pNIPAM. We initially confirmed the lower critical solution temperature (LCST), or the point in which pNIPAM agglomerates, to be thermodynamically reversible and reproducible for both pNIPAM and an electrochemically active poly(N-isopropylacrylamide)-block-poly(ferrocenylmethyl methacrylate) block copolymer, or p(NIPAM-b-FMMA).

Applying a potential across the DLS light path, we expected p(NIPAM-b-FMMA) to cause a shift in the transition temperature and agglomeration behavior. However, we unexpectedly observed a shift in the transition behavior of pNIPAM. At an applied electric field of 400 mV/cm and above, the transition temperature of pNIPAM started to shift negative. Further, upon cooling, the pNIPAM never re-dissolves, indicating an irreversible agglomeration in the presence of an applied.

We have also started to investigate reasons on why this phenomenon might occur. We will discuss two primary hypotheses, including wetting behavior changes of the pNIPAM and further radicalization of the RAFT agents leading to cross-linking and irreversible behavior.

Acknowledgements: The authors would like to acknowledge the financial support from NIH (P20 GM113131), NSF (CBET 1638896), the Collaborative Research Excellence Initiative Pilot Research Program at the University of New Hampshire, and the Hamel Center of Undergraduate Research at the University of New Hampshire. The authors also would like to acknowledge the assistance of Dr. Seitz’s laboratory and Dr. Halpern’s laboratory
The Use of Electroactive Ureidopyrimidones As Redox-Responsive Chain Terminators for Supramolecular Polymers
Authors: Smith Diane K. , Cedano Mario , Vuong Katrina
Published: May 2020

Unlike conventional polymers, in which monomers are reacted to form strong covalent connections, supramolecular polymers are formed by linking together monomers via weaker, non-covalent interactions such as H-bonds, ion-dipole interactions and so on. One very well-studied class of supramolecular polymers are based on the ureidopyrimidones, UPy’s, which dimerize via 4 strong, linear H-bonds in non-competitive solvents. Monomers for supramolecular polymerization can be made by linking together 2 or more UPy units with short covalent chains. Under dimerization conditions, the UPy’s link up to form longer polymeric chains. One of the useful attributes of such polymers is their self-healing ability. Application of heat or mechanical stress will readily break the monomers apart at the H-bonds, but, upon cooling or relief of stress, the bonds reform. The goal of this research is to see if electron transfer can be used as an alternative, more selective stimulus to break apart the UPy chains. As a first step in this direction, the use of our previously studied electroactive UPy’s, 1a and 1b, are being investigated as redox-active chain terminators. For these studies the known UPy monomer, 2, was synthesized. Viscosity measurements of solutions of 2 in 0.1 M NBu4PF6/CH2Cl2 give a critical polymerization concentration of 20 mM. Based on this, 60 mM 2 was chosen as the working concentration for initial experiments giving a solution with a specific viscosity of 3.0 mPa∙s. Upon addition of 2 mM of the ferrocene containing UPy 1a, the viscosity dropped to 1.1 mPa∙s, indicating that 1a is an effective chain terminator, decreasing the lengths of the chains which results in a decrease in the viscosity of the solution The ferrocenes were then completely oxidized to the ferrocenium form in a two compartment electrochemical cell. This caused the viscosity of the solution to increase from 1.0 to 1.7 mPa∙s, suggesting decreased effectiveness of the ferrocenium form as a chain terminator. This is consistent with poorer binding of the ferrocenium form to the bis-UPy. Importantly, reduction back to the ferrocene led to a decrease in the viscosity back to close to where it was initially. In this presentation, the results of further studies on the ability of both 1a and 1b to act as redox-responsive chain terminators for UPy-based supramolecular polymers will be reported.

Figure 1
Fluorescence Mapping of α-Tocopherol Redox Activity in Supported Lipid Bilayers
Authors: Sakaya Aya , Durantini Andres , Sverko Tara , Wieczny Vincent , Cosa Gonzalo
Published: May 2020

Lipid membranes have gained wide attention as assembly scaffolds, owing to their ability to self-assemble into well-defined fluid structures, allowing the compartmentalization and direct assembly of components of interest in a fluid platform. Model lipid membranes offer the opportunity to mimic and study processes occurring across these fluid mosaics such as respiration, transport and signaling.

Armed with a spectroelectrochemistry microscopy setup, in this study we have explored redox reactions within lipid membranes, proof of concept experiments intended to address the response of membrane embedded redox systems. Experimentally, a supported lipid bilayer was formed on top on an indium tin oxide (ITO)-coated glass. H4BPMHC, a redox sensitive fluorogenic probe bearing the chromanol moiety of α-tocopherol (Vitamin E), and a BODIPY tail segment was incorporated within the lipid membrane. The electrochemical and optical properties were next studied using our total internal reflection fluorescence (TIRF) microscopy based spectro-electrochemical (SEC) setup, that enables monitoring emission while minimizing background by virtue of sampling a small ~ 300 nm region above the glass water interface, while also controlling the redox potential at the basal leaflet of the lipid membrane.

Our results are consistent with oxidation of the chromanol moiety of the probe into a chromanone moiety through an irreversible process that elicits fluorescence, and further thermally induced rearrangement of the newly formed chromanone into a chromoquinone. We will discuss the general methodology, results, and implications of the work in the context of electron transport through relay redox systems.
Drug Metabolizing Liver Microsomal Biocatalysis on Pyrenyl Carbon Nanostructures
Authors: Krishnan Sadagopan
Published: May 2020

Non-covalent functionalization of carbon nanostructures has gained considerable attention in biological electrocatalysis, energy devices, and sensors. Simplicity of making the surface modification, scalability, and surface stability of pyrenyl-nanocarbon coated graphitic surface under rigorous conditions (e.g., electrode rotation at 2000 rpm for 4 days) makes them very attractive for biological electrocatalysts, operating in aqueous electrolytes. In the present work, we have designed a pi-pi stacked pyrenyl-carbon-nanostructure-electrode for stable electrostatic immobilization of liver microsomes. Direct electrocatalytic properties and drug monooxygenation activity of the major drug metabolizing membrane-bound cytochrome P450s present in the microsomal films will be discussed.
Electrochemical Investigations of L-Cysteine Interactions with Bismuth Ions
Authors: Cheek Graham T , Pena Dominik V
Published: May 2020

The use of bismuth compounds as medicinal treatments has prompted the electrochemical investigation of bismuth(III) salicylate, bismuth(III) citrate and bismuth(III) nitrate with L-cysteine in 0.1M HNO3 and 0.1M HCl using cyclic and square wave voltammetry. This level of acidity is meant to approximate the proton levels in gastric fluids. Platinum and gold electrodes were not used in order to avoid the reduction of protons to hydrogen gas at these high proton levels. At boron-doped diamond (BDD) and glassy carbon (GC) electrodes, significant voltammetric changes were observed upon incremental additions of L-cysteine even at pH 1.00. For example, additions of L-cysteine to bismuth(III) salicylate in 0.1M HNO3 at GC caused the Bi(III) reduction process to became narrower with an initial negative potential shift. Upon further additions of L-cysteine, the reduction curve displayed a positive potential shift and became even narrower as the complex exhibited faster electron transfer than the original Bi(III) species. A positive peak potential shift of the corresponding bismuth stripping peaks was also observed upon L-cysteine additions. These results show that L-cysteine, even in its most protonated state, is capable of acting as a complexing agent for Bi(III) species at pH 1.00. The results for other Bi(III) compounds under similar conditions are also planned for presentation.
Characterization of Antibiotic Compounds By Electrochemistry
Authors: Islam MD Rafiqul , Kuss Sabine , Schweizer Frank
Published: May 2020

The rise of antibiotic resistance has become a severe problem around the world. According to a report from the Centers for Disease Control and Prevention, approximately two million illnesses and 23,000 deaths are caused by antibiotic resistance each year in the United States alone and 10 million deaths worldwide each year. The Public Health Agency of Canada reported antimicrobial resistant is expected to kill nearly 400,000 Canadians and cost $400 billion in GDP by 2050. Electrochemistry with its high sensitivity has caught significant attention in the fields of biosensing and medical diagnostics over the last decade. This presentation describes our efforts to detect and quantify drug efflux from living bacteria. To this end, cyclic voltammetry and chronoamperometry were employed to characterize common antibiotics as well as newly investigational compounds, such as the antibiotic hybrid ciprofloxacin-tobramycin. Understanding the diffusional processes and electrochemical behavior of these drugs, first steps have been taken towards their quantitative detection in drug-sensitive and drug-resistant Pseudomonas bacteria.
Designing Amino Acid Detecting Electrochemical Biosensors for Health Research Applications
Authors: Mauzeroll Janine , Moussa Siba
Published: May 2020

Amino acids are recently emerging as potential biomarkers of neurological and kidney diseases such as Alzheimer's, Amyotrophic Lateral Sclerosis and Chronic Kidney Disease. The rising global prevalence of these disorders is making it increasingly essential to develop tools for rapid, direct and accurate amino acid quantification. In this talk, we will discuss the development of amino acid detecting enzymatic electrochemical biosensors and their applications health research. More specifically, the characterization of three different enzymes (Yeast D-amino acid oxidase, Human D-amino acid oxidase, and Glycine oxidase) and their development into biosensors will be presented.We will also explore the practical application of these biosensors for extensive use in answering fundamental neuroscience questions and their potential for implementation as a clinical diagnostic tool.
Improvement of the Performance in Membraneless Aqueous H2O2 Fuel Cells By Electroadsorption of Ad-Anions on the Surface of the Cathodes
Authors: Manriquez Juan , Ortega-Díaz David , Sepúlveda Selene , Bustos Erika , Orozco Germán
Published: May 2020

Performance of a membraneless aqueous H2O2 fuel cells were significantly improved by assembling prussian blue-modified glassy carbon anodes (GC/PB) and gold cathodes whose surfaces were enriched by H2PO4
- ad-anions (Au/H2PO4
-). In this way, glassy carbon anodes were modified by a potentiostatically-deposited prussian blue (PB = Fe4[Fe(CN)6)]3•xH2O) film, whereas H2PO4
- ad-anions were electroadsorbed on the polycrystalline gold cathodes by means of cyclic voltammetry. The as-prepared electrodes were inserted in H2O2 fuel cells filled by deoxygenated phosphates buffer solutions (PBS, pH 2) containing several initial H2O2 concentrations. A highest power performance of the electrode materials was found by comparing all the discharge curves (potential vs. current plots) obtained as a function of the initial H2O2 concentration fed to the cells. Effect of the gap between the electrodes over the fuel cells performance was previously explored and optimized. The tabulated results below, demonstrate that the performance achieved for the cells constructed in this work was significantly superior to the best performance reported for comparable H2O2 fuel cells. Thereafter, electrochemical impedance spectroscopy (EIS) and a Bisquert type electrical transmission line [2] (data not shown), were employed for better understanding how an optimized electron-transfer kinetics for the Au/H2PO4
- cathodes allowed improving to the fuel cells performance. Finally, our results demonstrated that, once the Au/H2PO4
- cathodes were inserted into the H2O2 fuel cells the fill factor and the maximal power density were improved with the aid of the establishment of a competition between the electrical and ionic conductivities occurring through the PB films at the Au/PB anodes.

open-circuit potential

(mV)

maximal current density

(mA/cm2)

fill factor

maximal power density (mW/cm2)

This work

741±11

13.5±0.4

0.56±0.03

5.6±0.2

Ref. [1]

600

10

0.26

1.6

References:

[1] Y. Yamada, M. Yoneda, S. Fukuzumi, Energy Environ. Sci., 8 (2015) 1698.

[2] J. Bisquert, Phys. Chem. Chem. Phys., 2 (2000) 4185.

Acknowledgements:

The authors thank the Mexican Council for Science and Technology (CONACyT) for its financial support of this work (grant 258789). D.O. acknowledges CONACyT for his PhD scholarship (grant 639209).
Anodic Dissolution of Copper in the Aluminum Chloride-1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid
Authors: Reidy Lorlyn , Wang Chen , Hussey Charles
Published: May 2020

The ever popular AlCl3-1-ethyl-3-ethylimidazolium chloride (EtMeImCl) ionic liquid (IL) system offers a unique solvation environment for many metal ions. In fact, the use of these chloroaluminate ionic liquids for the electrochemical surface finishing of metals was recently reviewed.1 These ionic liquids display adjustable Lewis acidity that depends directly on the mole ratio of the AlCl3 to the organic salt. The basic AlCl3-EtMeImCl mixture, which contains coordinately unsaturated Cl-, provides a solvation environment similar to aqueous HCl and NaCl, except of course without the complications due to the H2O solvent or H3O+. The opposite situation prevails in the Lewis acidic ionic liquid because the main chemically active ionic component of the ionic liquid is the coordinately unsaturated species, [Al2Cl7]-. Thus, there are no “hard” ligands available to form stable, isolable anionic complexes with the anodization product. Recently, both composition regions of the AlCl3-EtMeImCl IL system have been explored for the electrodissolution/electropolishing of Al.2 The advantages afforded by anodic dissolution of metals in this ionic liquid relative the aqueous acids and salt solutions commonly used for this purpose are quite obvious, i.e., the avoidance of the oxide surface films that invariably complicate the metal electropolishing process. In this paper, we report the thermodynamics and kinetics of the anodic dissolution of copper metal in the acidic and basic compositions of the AlCl3-EtMeImCl ionic liquid. In the former, the dissolution of copper at a Cu-RDE exhibits mixed control. No limiting current or passivation due to the formation of an insoluble surface film was apparent. In the basic composition region, mixed control was observed at small overpotentials, but as the overpotential was increased, a limiting current was obtained that scaled linearly with the Cl- concentration in the ionic liquid. The connection between these results and the mechanism of the dissolution process will be discussed.

____________________________________________

1. T. Tsuda, G. R. Stafford and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017).

2. C. Wang and C. L. Hussey, J. Electrochem. Soc., 163, H1186 (2015).
Analysis of Stacked-Photo-Anode for Photoelectrochemical Water Splitting Reaction
Authors: Pala Raj Ganesh , Ummireddi Ashok
Published: May 2020

In photoelectrochemical water splitting, every impinging photon should not only be absorbed but also be utilized towards reaction. While increasing photoelectrode thickness in photoelectrochemical reactors facilitates photon absorption, it has a debilitating effect on efficiency if the thickness required for complete photon absorption is much more than the exciton diffusion length, which is a property determined by the material and its processing. To address this issue, we demonstrate a general experimental methodology with a stack of CdSe photoanodes wherein the thickness of each photoelectrode is of the order of exciton diffusion length and which improves overall photocurrent by about 50%.
Development of Metal Oxides Heterostructure for Highly Selective CO2 Reduction to Methanol.
Authors: Sabbah Amr , Chen Ting-Hsuan , Shown Indrajit , Chen Kuei-Hsien , Chen Li-Chyong
Published: May 2020

Carbon dioxide conversion into valuable chemicals using solar light considered an ideal goal in renewable energy studies. For the purpose of effective photocatalytic materials, a large number of strategies have been studied. Coupling of semiconductors is considered one of the best approaches to design a good photocatalyst for producing selective solar fuels. In this study, we fabricate ZnO/ Co(OH)2 model heterogeneous catalysts for CO2 reduction under visible light irradiation. Firstly, Three ZnO samples with different morphologies and surface area were fabricated by varying preparation methods. It is found that ZnO nanoflakes with a high ratio of {0002} facets possess a higher conversion rate yielding Methanol, Acetaldehyde, and Acetone as the major products of photocatalytic CO2 reduction in a continuous flow gas-phase reaction condition. The obtained ZnO nanoflakes were then treated to form the heterostructure of ZnO/Co(OH)2. When the mass ratio between hexagonal-phased ZnO and Co(OH)2 is varied, the composite catalyst shows selective methanol formation as a major product compared to pristine ZnO phases. The synthesized samples were characterized by means of a multi techniques approach involving powder X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, Photoluminescence, UV-Visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and surface area measurements. In conclusion, the results can not only provide the importance indication about the influence of {0002} facets of ZnO, but also demonstrated a strategy for the selective formation of hydrocarbons over the heterostructure semiconductors of ZnO/Co(OH)2 nanocomposites.
Local Electrocatalytic Activity of Electrodeposited Ni-Fe Particles
Authors: Byers Joshua , Beugre Romaric C
Published: May 2020

NiFe electrocatalysts have received increasing attention for the electrocatalysis of the oxygen evolution reaction.[1] Recently, using bipolar electrochemistry for the electrodeposition of nickel, we have demonstrated the formation of nickel particle gradients, which vary in size and particle density as a function of electrode position.[2] In this work, low ionic strength aqueous solutions containing Ni(II) and Fe(II) salts, without supporting electrolyte, were used for the electrodeposition of NiFe particles onto a conducting fluorine doped tin oxide substrate. In this talk, I will present our recent results exploring the effect of composition, size and morphology of NiFe particles on the local electrocatalytic activity towards the oxygen evolution reaction, measured using scanning electrochemical cell microscopy.[3]

[1] Song, F., Bai, L., Moysiadou, A., Lee, S., Hu, C., Liardet, L., Hu, X. Transition Metal Oxides as Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Solutions: An Application-Inspired Renaissance (2018) Journal of the American Chemical Society, 140 (25), pp. 7748-7759.

[2] Beugré, R., Dorval, A., Lavallée, L.L., Jafari, M., Byers, J.C. Local electrochemistry of nickel (oxy)hydroxide material gradients prepared using bipolar electrodeposition (2019) Electrochimica Acta, 319, pp. 331-338.

[3] Bentley, C.L., Kang, M., Unwin, P.R. Nanoscale Surface Structure-Activity in Electrochemistry and Electrocatalysis (2019) Journal of the American Chemical Society, 141 (6). pp. 2179-2193
Real-Space 3D Simulation of Cyclic Voltammetry in Carbon Felt Electrodes for Application in Vanadium Redox-Flow Batteries Based on a Combination of Micro CT Data, Digital Simulation and Convolutive Modelling
Authors: Tichter Tim , Andrae Dirk , Schneider Jonathan , Gebhard Marcus , Hilger André , Manke Ingo , Roth Christina
Published: May 2020

Cyclic voltammetry (CV) is the prevalently used technique for investigating the kinetic performance of carbon felt electrodes for application as porous electrocatalysts in vanadium redox-flow batteries. However, the theoretical treatment of internal diffusion-reaction phenomena of such electrodes, allowing for quantitative data evaluation, is still unexplored and mostly relies on diffusion domain approximations assuming the felt as an array of either planar, spherical or cylindrical microelectrodes in a randomly distributed and finite diffusion domain. With this study, we present a novel three-step strategy for real-space CV simulation of felt electrodes. By using micro x-ray tomography (CT) data of the felts, we obtain a locally resolved 3D template of the diffusion space making any diffusion domain approximations obsolete. CV simulation involving this real diffusion domain template is performed by combining the implicit Crank-Nicolson technique in 3D with convolutive modelling. At first, by utilizing the Crank-Nicolson method, we obtain the chronoamperometric current of the 3D porous network for Cottrell-like Dirichlet boundary conditions. Subsequently, the mass transfer functions, usually generated with the aid of Laplace integral transformation techniques, are calculated from these chronoamperometric currents. Then, CV simulation is performed on the basis of these mass transfer functions involving classical convolution integrals. This strategy offers three significant advantages. First, we avoid the difficulty of implementing non-Dirichlet boundaries in the matrices of the Crank-Nicolson scheme. Second, the difficulty of performing an inverse Laplace transformation is avoided since no direct Laplace transformation step is involved. Third, once the mass transfer functions are obtained the simulation can be done with significant savings in time since the 3D network is converted into a one-dimensional problem that can be solved via classical convolution integrals. Our simulation is supported by experimental data acquired for the VO2+-oxidation reaction underlining the validity of our approach.

Figure 1
Organic/Inorganic Hybrid Electrode Materials for Photo-Conversion of Solar Energy
Authors: Jouini Mohamed , Santoni Marie-Pierre , Ramanitra Hasina , Delices Annette , Xu Zijun , Dong Chang-Zhi , Bellynck Sebastien , Maurel François , Chevillot Alexandre , Szaniawska Ewelina , Wadas Anna , Rutkowska Iwona Agnieszka , Kulesza Pawel J.
Published: May 2020

NiO nanoparticles deposited on FTO glass modified surface were used to adsorb an organic dye. The obtained device was covered with PEDOT/PSS polymers blend and later sprinkled with palladium nanoparticles.

This modified hybrid electrode was used under ligth and than under dark conditions to study the reduction reaction of CO2 in solution.

The results obtained indicated a large shift toward positive potential of the reduction wave of CO2 in solution under light when compared to the same reduction wave under dark in the same conditions.

The obtained results will be presented and discussed in the frame of the state of the art of CO2 reduction catalysed by palladium nanoparticles supported by hybrid charge transport material.
Observing the Growth Mechanism of Au-ZnO Core-Shell Nanoparticles by In-Situ Liquid Cell TEM
Authors: Tsai Shin-Bei , Huang Chih-Yang , Chen Jui-Yuan , Wu Wen-Wei
Published: May 2020

Heterostructured nanoparticles have attracted significant attention due to its unique morphology and promotion of a wide range of applications. Among the different kinds of heterostructured nanomaterials, Au-ZnO core-shell nanoparticles have been widely used in dye-sensitized solar cells, photocatalysis, gas sensing and biological detection due to its distinctive physical and chemical properties. Understanding the growth behaviors of nanomaterials is essential for controlling their size, morphology and chemical composition, which can improve the applicability. However, the growth mechanisms of Au-ZnO core-shell nanoparticles are mostly suggested by the post-reaction investigations, and the direct observation of synthesis process is lacking but crucial.

In this work, we utilized liquid cell transmission electron microscopy (LC-TEM) to observe the formation of Au-ZnO core-shell nanoparticles in real-time. The synthesis process of Au-ZnO core-shell nanoparticles was successfully demonstrated via in-situ LC-TEM (Figure 1). The solutions of zinc nitrate hexahydrate ( Zn(NO3)2 · 6H2O), hexamethylenetetramine (HMTA), ascorbic acid (AA) and hexadecyl trimethylammonium bromide (CTAB) were introduced into the liquid cell at the flow rate of 1 µl/min via the microchannels after Au nanoparticles dispersed. The citrate-stabilized Au nanoparticles attracted Zn(OH)4
2‒ complexes with the aid of CTAB and AA, and then Zn(OH)4
2‒ complexes would dehydrate and transform into loose ZnO shells around the Au cores. The morphology of ZnO shells was spherical and smooth, without any granular or crystalline appearance (Figure 2), which was suggested to result from absorbing CTAB molecules. In order to increase the crystallinity of ZnO shells by removing CTAB molecules, the Au-ZnO core-shell nanoparticles were heat-treated at 500°C for 2 h. The crystallization of ZnO shells followed by heat treatment could methodically control the microstructure of heterostructed nanoparticles (Figure 3). The growth behaviors, elements distribution and the statistics about growth has been systematically analyzed. This in-situ experiment casts light on preparation of Au-ZnO core-shell nanoparticles with function of CTAB and AA, extending the study of reaction mechanism and the improvement of controllability of heterostructure synthesis for further device application.

Figure 1
Quantitative Concentration Mapping with AFM-SECM
Authors: Mirabal Alex , Calabrese Barton Scott
Published: May 2020

Efficient transport of reaction intermediates between active sites can improve the efficiency of multi-site reactions1–3. Experimental detection of these nanometer length scale transport mechanisms is enabled by Scanning Electrochemical Microscopy (SECM). Electrochemical measurements can allow for concentration profile mapping to elucidate the transport processes in experimental systems. SECM can correlate position dependent responses to properties of the system. There is a significant impact on the response profile due to the SECM tip’s presence at the nanoscale. Finite Element Analysis (FEA) has been used to understand and remove these in situ tip effects.

The calculated concentration, using current-flux relations, can be complex near sites generating flux through reactions and/or transport. Additionally, uncertainties such as tip positioning in relation to the interface site can further complicate the response. Quantitative concentration fields can more readily be interpreted through FEA, by matching the experimental tip response.

Electrodeposited platinum nanoparticles were imaged topographically and electrochemically with a Bruker AFM-SECM (Figure 1). The positive response over the nanoparticles vs. the planar HOPG sites allows for kinetic response imaging. The model is parameterized through approach curves and verified though SECM mapping correlation.

We have previously applied FEA to correlate experimental in situ results to in operando conditions. Here, we use this approach to generate corrected concentration profiles. We use Pt nanoparticle catalysts deposited on HOPG, to develop surface property correlations. In this way, a comparison can be drawn between in situ and in operando approaches.

References

(1) Schuhmann, W. Amperometric Enzyme Biosensors Based on Optimised Electron-Transfer Pathways and Non-Manual Immobilisation Procedures. Rev. Mol. Biotechnol.
2002, 82 (4), 425–441.

(2) Wheeldon, I.; Minteer, S. D.; Banta, S.; Barton, S. C.; Atanassov, P.; Sigman, M. Substrate Channelling as an Approach to Cascade Reactions. Nat. Chem.
2016, 8 (4), 299–309.

(3) Liu, Y.; Hickey, D. P.; Guo, J. Y.; Earl, E.; Abdellaoui, S.; Milton, R. D.; Sigman, M. S.; Minteer, S. D.; Calabrese Barton, S. Substrate Channeling in an Artificial Metabolon: A Molecular Dynamics Blueprint for an Experimental Peptide Bridge. ACS Catal.
2017, 7 (4), 2486–2493.

Figure 1
High Electrochemical Signal Amplification Using a Propagating Cascade Reaction and a Redox Cycling Reaction
Authors: Yang Haesik , Park Kiryeon
Published: May 2020

Propagating cascade reactions based on two enzymes have been used to achieve high signal amplification in biosensors wherein one enzyme continually triggers the activation of the other enzyme that produces signaling species. However, in many cases, biosensors that use cascade reactions are not sensitive enough to allow low detection limits because of the inherent slowness of proteolytic reactions. This paper reports a sensitive electrochemical immunosensor using a high-signal-amplification method that combines a propagating cascade reaction and a redox cycling reaction. The cascade reaction uses ecarin and prothrombin: the ecarin label proteolytically converts inactive prothrombin into active thrombin, which then proteolytically liberates electroactive p-aminophenol (AP) from an AP-conjugated peptide. The liberated AP is electrochemically oxidized to p-benzoquinone imine (QI), regenerated by the reduction of QI by NADH, and then electrochemically reoxidized. This electrochemical−chemical (EC) redox cycling reaction significantly increases the electrochemical signal. The developed immunosensor is also compared with an immunosensor that uses only a propagating cascade reaction and an immunosensor that uses a single proteolytic reaction and an EC redox cycling reaction. The detection limits for thyroid-stimulating hormone (TSH) obtained using the three immunosensors are 3 pg/mL, 2 ng/mL, and 4 ng/mL, respectively, indicating that the newly developed immunosensor is more sensitive than the others. The measured concentrations of TSH in clinical serum were found to agree well with those determined using a commercial instrument, indicating that the immunosensor is highly promising for sensitive detection of biomolecules.

Keyword: Electrochemical biosensor, Cascade reaction, Redox cycling, Proteolytic reaction
Synthesis of Au@ZIF-8 Nanocomposites for Enhanced Electrochemical Detection of Dopamine
Authors: Lu Shun , Hummel Matthew , Gu Zhengrong
Published: May 2020

Dopamine (DA) is a well-known neurotransmitter, which is an organic chemical of the catecholamine and phenethylamine families, playing important roles in in the brain and body. However, a deficiency of DA in the human body could lead to neurological disorders. In contrast, a high level of DA could cause an increased risk of depression. Therefore, the significance of DA in the clinical diagnostic perspectives has drawn great awareness for the development of sensitive and reliable techniques for their detection. In our recent study, gold nanoparticles and zeolitic imidazolate framework-8 nanocomposites (Au@ZIF-8) were synthesized through a simple hydrothermal method and used as an enzyme-free sensor for the detection of DA. To gain insight into the structure and morphology of Au@ZIF-8 nanocomposites, various characterizations were used, i.e. scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopic (TEM), scanning transmission electron microscope-energy X-ray diffraction spectroscopy (STEM-EDX). Then, Au@ZIF-8 nanocomposites modified glass carbon electrodes (Au@ZIF-8/GCEs) were examined in 0.1 M phosphate-buffered saline (PBS) with different concentrations of DA. Au@ZIF-8/GCE possessed an excellent electrochemical catalytic performance to DA which are derived from electrochemical test, having been reported to own wider linear range from 0.01-50 μM, lower detection limit of 0.01 μM (S/N = 3) and higher sensitivity of 6.452 μA mM-1 cm-2. The proposed Au@ZIF-8/GCE exhibits better sensitivity than ZIF-8/GCE that we previously reported, it also shows good selectivity and long-term stability after 1000-cycle CV test. Such selectivity and comparable performance can be attributed the synergetic electrochemical performance between Au NPs and ZIF-8, and fast charge transfer ability between the electrochemical sites and the electrode. Therefore, Au@ZIF-8/GCE presents promising performance as a potential non-enzymatic dopamine sensor.

Figure 1
Electrodeposition of Cu2o/MoS2 Thin Films on Fto Substrate As a Heterojunction Photoelectrochemical Cell for Water Splitting
Authors: Le Viet Hai , Huynh Le Thanh Nguyen , Nguyen Hoang Thai
Published: May 2020

The layered structure MoS2, an n-type conductor (bandgap of 1.9-2 eV), can be excited under irradiation with visible light. However, its valence band energy (-4.2 eV) is closed to the minimum energy required to reduce water into hydrogen (- 4.2 eV at pH = 7). The p-type semiconductor Cu2O (a bandgap of 2 eV) has a valence band energy of - 4.0 eV, higher than that of MoS2 and therefore has potentially as photocatalytic for water splitting. In this work, the heterojunction of Cu2O/MoS2 is prepared on a conductive FTO-coated glass substrate by electrodeposition methods. We conduct initially the MoS2 thin film on FTO by cyclic voltammetry (CV). Then, the Cu2O thin film is deposited on the MoS2/FTO thin film by double-potential pulse chronoamperometric (DPPC) to form a p-n junction Cu2O/MoS2/FTO photo-electrode which play an anodic role in a photoelectrochemical cell. The structure, morphology and composition of heterojunction electrode are characterized by powder X-ray diffraction, SEM, TEM, IR, Raman spectroscopy, electrochemical impedance spectroscopy (EIS). The optical properties are determined by UV-VIS spectroscopy and Photoluminescence (PL) spectroscopy. The photoelectrochemically catalytic activity of the electrodes is performed in dark condition and light condition with 1.5 AM from a solar simulator system by Linear-sweep voltammograms and Transient photocurrent-time methods. The H2-generation yield is evaluated by gas chromatography. The effect of the structure and the composition of the Cu2O/MoS2 thin films on the kinetics and mechanism of the photoelectrochemical water splitting is also considered.
Investigating the Importance of the Experimental Cell Environment
Authors: Thomas Nikita , Kuss Sabine
Published: May 2020

Scanning Electrochemical Microscopy (SECM) has gained increasing attention in the field of bioanalytical chemistry and recent applications include studies on tissue cells, cancer cells and bacteria. Although these studies represent interesting new approaches, the influence of the experimental conditions on the electrochemical signal obtained from cells has never been properly assessed. This poster presents a thorough assessment of the electrochemical signal obtained from cervical cancer cells and how it changes depending on experimental conditions. Cell media composition, temperature, and light exposure as well as the experiment duration has been considered. This study will be an important basis for SECM research on biological cells, and may be a reference point for many future studies in the bioelectrochemical community.