bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bio-Inspired Photoresponsive Regulator for Proton Cross-Membrane Transport
Authors: Li Ying , Tse Edmund C. M. , Barile Christopher J. , Gewirth Andrew A. , Zimmerman Steven C 
Published: February 2020

Proton-Coupled Electron Transfer (PCET) is ubiquitous in nature, essential to life but particularly difficult to study because of the complexity of natural systems. We recently developed a new experimental framework to permit fine-tuning of proton-transfer kinetics without perturbing the thermodynamics. The regulation took advantage of the “flip-flop” diffusion of proton carriers inside lipid membranes. Unfortunately, the diffusion happens spontaneously and more precise control could be beneficial. As a result, we designed the first synthetic photoresponsive proton gate incorporated in a lipid layer. The new proton carrier features a boronic acid head-group for proton transfer, a stiff stilbene body for photoresponsiveness, and an alkyl tail for lipid incorporation. The light-induced cross-membrane proton transfer was quantified by the activity of an O2 reduction catalyst buried under the lipid layer by electrochemistry. This molecular switch mimics the natural system to precisely control proton relocation without perturbing the proton thermodynamics (Scheme 1).
Scheme 1. Illustration of photoresponsive transmembrane proton transfer.

Figure 1
(Invited) Customizing Proteins and Microbes for Biological Fuel Cells
Authors: Ajo-Franklin Caroline Marie , Baruch Moshe , Fukushima Tatsuya 
Published: February 2020

Electron transfer between proteins in microorganisms and solid materials underpins many aspects of bioelectrochemical energy research. My laboratory seeks to tailor both new microbes and new proteins for specific bioelectrochemical applications. Here I will first describe how we have customized the industrial microbe Escherichia coli for use in biological fuel cells. By transplanting the Mtr pathway of Shewanella oneidensis MR-1 into Escherichia coli, we can confer upon these cells the ability to reduce metal ions, solid metal oxides, and electrodes. These cells couple current production to a metabolic shift towards more oxidized products, demonstrating that we can electronically control the intracellular state of these engineered E. coli. Additionally, we have shown that these engineered E. coli can accept, as well as donate, electrons from an electrode. Thus, this work provides a blueprint to bi-directionally move energy and information between microbial cells and electrodes, and has direct applications in biosynthesis and bioenergy. I will also describe new studies probing the thermodynamic and structural basis by which Mtr proteins reduce solid metal oxides. We show that MtrF from S. oneidensis MR-1, which can directly reduce iron oxide, binds to iron oxide, but not structurally similar aluminum oxide. Using protein and X-ray footprinting, we also probe which residues of this extracellular electron transfer protein are potentially involved in binding iron oxide. We find that these residues cluster in the tertiary, rather than primary, structure of the protein, suggesting that these regions form a binding site for their solid substrate. This new understanding will critically inform efforts to rationally design proteins capable of rapid interfacial electron transfer.
Spatially Resolved Confocal Resonant Raman Microscopic Analysis of Anode-Grown Geobacter Sulfurreducens Biofilms
Authors: Lebedev Nikolai , Strycharz-Glaven Sarah , Yates Matthew , Tender Leonard M 
Published: February 2020

When grown on the surface of anode electrode, Geobacter sulfurreducens forms a multi-cell thick biofilm in which all cells appear to couple oxidation of acetate with electron transport to the anode which serves as the terminal metabolic electron acceptor. Just how electrons are transported through such a biofilm from cells to the underlying anode surface over distances that can exceed 20 microns remains unresolved. Current evidence suggests it may occur by electron hopping through a proposed network of redox cofactors comprised of immobile outer membrane and/or extracellular multi-heme c-type cytochromes. In the present work we apply spatially resolved Confocal Resonant Raman (CRR) microscopic analysis to investigate anode-grown Geobacter biofilms. The results confirm presence of an intra-biofilm redox gradient whereby the probability that a heme is in the reduced state increases with increasing distance it resides from the anode surface. Such a gradient is required to drive electron transport toward the anode surface by electron hopping via cytochromes. The results also indicate that at open circuit when electrons are expected to accumulate in redox cofactors involved in electron transport due to inability of the anode to accept electrons, nearly all c-type cytochrome hemes detected in the biofilm are oxidized. The same outcome occurs when a comparable potential to that measured at open circuit (-0.30 V vs. SHE) is applied to the anode, whereas nearly all hemes are reduced when an exceedingly negative potential (-0.50 V vs. SHE) is applied to the anode. These results suggest that nearly all c-type cytochromes hemes detected in the biofilm can be electrochemically accessed by the electrode, but most have oxidation potentials too negative to transport electrons originating from acetate metabolism. The results also reveal lateral heterogeneity (x-y dimensions) in type of c-type cytochromes within the biofilm that may affect electron transport to the electrode.
[1] Lebedev, N., Griva, I. & Blom A. Internal Control of Electron Transfer through a Single Iron Atom by Chelating Porphyrin. J. Phys. Chem. C 117, 6933−6939, 2013.
[2] Lebedev, N., Strycharz-Glaven, S. M. & Tender L. M. Spatially Resolved Confocal Resonant Raman Microscopic Analysis of Electron Transfer in Geobacter sulforreducens Biofilm. ChemPhysChem, 15, 320-327, 2014.
[3] Lebedev, N., Strycharz-Glaven, S. M., & Tender L. M. High resolution AFM and single-cell resonance Raman spectroscopy of Geobacter sulfurreducens biofilms early in growth. Frontiers in Energy Research, 2:34, doi: 10.3389, 2014.
Influence of Anode Configuration on Flow Distribution and Performance in Tubular Microbial Fuel Cells
Authors: Mirhosseini Auvid , Salvacion Michael , Chen Shing , Babanova Sofia , Bretschger Orianna 
Published: February 2020

A microbial fuel cell (MFC) is a device that utilizes bacteria to oxidize organic and inorganic matter, and through the process of extracellular electron transfer, generate electricity. When the electron transfer at the bacteria-electrode interface is rapid, the efficiency of a MFC is dependent on the flow distribution and mass transport in the anode, which controls the delivery of reactants and removal of waste products. It has been predicted that diffusion of soluble substrates is fast over the length scale of bacterium, but gets significantly slower over millimeter-scale distances and at the scale of centimeters, advection is required. Electrolyte advection along with optimal flow distribution will bring substrates to anode respiring bacteria and enable substrate utilization at high rates. Therefore, in this study we explored the influence of the anode configuration on flow distribution and MFC performance. The efficiency of the system was determined on the basis of chemical oxygen demand (COD) removal and Columbic Efficiency (CE).
The MFC used for these studies was a membrane based tubular MFC with a submerged oxygen-reducing cathode. Three anode configurations were explored and included: 1) packed graphite granules (MFC 1); 2) bundles of stacked graphite granules (MFC 2); and 3) a small polypropylene mesh cylinder filled with packed graphite granules, wrapped with pleated carbon cloth (MFC 3). The volume of the anode compartment of each reactor was 1L. The reactors were operated under MFC, semi-batch mode with a downstream flow. The reactors were first inoculated with swine waste and lagoon sediment and subsequently fed with swine waste only 1,300 mg-COD/L.
Key parameters were measured on a weekly basis including COD, pH, dissolved oxygen (DO) and turbidity. Samples for 16S rRNA analysis were also collected on a weekly basis from the effluents of each reactor for the classification and identification of bacterial species present. Voltage data was recorded continuously and polarization curves and cyclic voltammetry were periodically performed to monitor biofilm development and MFCs operation.
The preliminary results indicate that due to the advanced flow distribution, MFC 3 demonstrated the highest performance. It showed a startup time of approximately 4 days and achieved a voltage of 0.40 V. MFC 2 also had a startup time of approximately 4 days and achieved a voltage of 0.15 V. MFC 1 had the slowest startup time of about 11 days with a voltage of ≈ 0.10 V. All MFCs were operated under 560 Ω resistors. Future work will include a comprehensive analysis of microbial dynamics and system performance to determine which anode structure was most correlated to improved wastewater treatment and energy recovery activities.
Development of a Microbiosensor for Acetate Detection in Biofilms
Authors: Atci Erhan , Babauta Jerome T. , Sultana Sujala T. , Beyenal Haluk 
Published: February 2020

We developed an amperometric acetate microbiosensor capable of measuring in situ sub-micromolar concentration of acetate inside biofilms. The operating principle of the microbiosensor utilized electrochemically active biofilms (EABs) to convert acetate to electrons on the microelectrode tip. The acetate microbiosensor consisted of a 30 µm glass-covered carbon wire working electrode with G.sulfurreducens biofilm on the tip recessed into a glass outer case approximately 200 μm and a Ag/AgCl reference electrode, as shown in Figure 1. The glass outer case terminated to a 30 µm tip diameter where acetate could flow into and diffuse up to the active tip. Acetate-free G.sulfurreducens growth medium served as electrolyte. The microbiosensor showed a linear response between 50 µM and 1.6 mM acetate concentration with a 79 ± 8 µM limit of detection (S/N=2). The operating potential of the microbiosensor was selected as +300 mVAg/AgCl satisfying the limiting current condition. The microbiosensor also demonstrated a higher specificity to acetate over other possible metabolites that could interfere with acetate measurements.
To test the microbiosensor, we measured local acetate concentration inside G. sulfurreducens biofilms grown on a 1 in2 electrode in a three-electrode bioreactor operated in fed-batch mode. Measuring acetate profiles in G.sulfurreducens biofilms is critical to understand acetate limitations and acetate diffusion and to test the developed microbiosensor in G.sulfurreducens biofilms which utilizes acetate as the electron donor. The microbiosensor was used to measure acetate depth profiles within ~225 µm thick G.sulfurreducens biofilm under no current generation (open circuit potential) and current generation (at +300 mVAg/AgCl) conditions. For depth profile measurements, bulk acetate concentration in the bioreactor was set to 1.5 mM by considering the linear calibration range of the microbiosensor. The acetate concentration remained at bulk values throughout the biofilm at open circuit potential when the biofilm was not respiring. However, the acetate concentration decreased from the bulk values to below the detection limit within 200 μm when current was allowed to pass at +300 mVAg/AgCl. This showed that the biofilm was acetate-limited due to the zero acetate concentration at the bottom of the biofilm.

Figure 1
(Invited) How Spatial Heterogeneities Affect Dynamics of Ionic Liquids
Authors: Roy Soham , Zheng Zhuan-ping , Bonn Mischa , Hunger Johannes 
Published: February 2020

Despite that the heterogeneous structure of ionic liquids (ILs) has been established, the consequences of the nanoscopic segregation on the dynamics of ILs has remained elusive. In particular, the spatial heterogeneity in ILs may result in inherently different local solute environments when using ILs as solvents. Such different local interactions will affect the ability to re-structure and dissipate excess energy during a chemical reaction, which determines the performance as a solvent.
We study these solvent dynamics using femtosecond infrared spectroscopy for a series of alkylammonium ionic liquids [1, 2]. In these experiments vibrational excitation of the ND or NH stretching vibrations results in an ultrafast, local temperature jump and we monitor the subsequent equilibration as a response to the dissipated energy. Owing to the intrinsic molecular specificity of infrared vibrations we can thus probe specifically the different moieties of the ionic liquid’s ions, providing access to the intrinsic solvation dynamics in the absence of any probe molecules. Our results show that ionic liquids are not only structurally heterogeneous, but exhibit a substantial dynamic heterogeneity, with the equilibration within the hydrophobic domains being two-fold faster than in the ionic domains.
The excitation anisotropy, which provides information on the local rotational mobility of the ionic fragments of the cations, is rather insensitive to the size of the cations: Our results even suggest that increasing the hydrophobic domain size goes along with an acceleration of the restricted rotational motion of the ammonium group of the cationic fragments of the IL’s ions. Such accelerated dynamics are indicative of reduced directional interionic interactions, which in turn signify a more fragile three-dimensional structure as the size of the hydrophobic fragments increases.
Our study shows that local dynamics in these ionic liquids are decoupled from macroscopic properties, like e.g. viscosity. Thus, our findings underline that the structural heterogeneity of ILs makes local dynamics heterogeneous, with substantially different solvation properties within the hydrophobic and the ionic sub-domains.
[1] J. Hunger, T. Sonnleitner, L Liu, R. Buchner, M. Bonn and H.J. Bakker, „Hydrogen-Bond Dynamics in a Protic Ionic Liquid: Evidence of Large-Angle Jumps“ J. Phys. Chem. Lett.
3, 3034 (2012).
[2] Z.P. Zheng, W.H. Fan, S. Roy, K. Mazur, A. Nazet, R. Buchner, M. Bonn, and J. Hunger “Ionic Liquids: Not only Structurally but also Dynamically Heterogeneous”, Angew. Chem. Int. Ed.
54
, 687 (2015).
(Invited) Towards a Molecular Level Understanding of the Electrolyte Choline Chloride / Urea
Authors: Hunt Patricia A , Ashworth Claire , Welton Tom 
Published: February 2020

Low melting point deep eutectic solvents (DES), can be formed from quaternary ammonium salts with a variety of neutral species. Eutectic mixtures of such salts with metal halides are well established, Figure 1a. DES employing an ionic liquid component and hydrogen-bond donor, such as CholineChloride/Urea (ChCl/Urea), Figure 1b, are gaining interest as electrolytes, particularly for clean metal extraction and deposition. DESs can reduce complex processes, avoid hydrogen evolution and embrittlement, deposit reactive metals and metal-alloys unobtainable from aqueous solutions, provide access to novel coating morphologies and enhanced surface properties (increased hardness, reduced roughness), and may offer advantages for the production of nanoporous and nanostructured metals.
DES have properties that are particularly attractive for large scale technological applications. DES are cheap, non-toxic, potentially biodegradable, they have a good electrochemical window, good thermal stability and reasonable electrical conductivity. DES can dissolve recalcitrant species such as metal oxides and reduce operating temperatures due to the low melting point. Additional advantages of the DES include muti-ton production and a high stability with respect to air and moisture.
For example, direct comparison of DESs with standard aqueous solution processes have shown Ni deposition occurs at comparable rates for the same concentration and temperature conditions. The increased viscosity and reduced conductivity of ChCl/Urea are not rate limiting factors and it has been suggested that speciation within the electrolyte plays the more significant role.1

Typically the melting point depression of DES is linked to the formation of a larger more diffuse covalent complexed anion, which has a reduced interaction with associating cations, Figure 1. However, when the neutral component is an organic species capable of acting as a H-bond donor there are uncertainties with respect to the speciation and bonding within the mixture. We have employed electronic structure methods to examine the interactions between constituent species of ChCl/Urea. Within cluster models a subtle interplay of electrostatics and different types of H-bonding are observed and elucidated. Links can be made between these molecular level interactions and the physico-chemical properties of ChCl/Urea DES.

1Abbott, A. P., Ballantyne, A., Harris, R. C., Juma, J. A., Ryder, K. S., & Forrest, G., Electrochimica Acta, 2015, 176, 718–726. http://doi.org/10.1016/j.electacta.2015.07.051

Figure 1
(Invited) Ionic Liquid-Based Electrolytes for Alkaly Metal Batteries
Authors: Giffin Guinevere , Jeong Sangsik , Passerini Stefano 
Published: February 2020

Ionic liquid-based electrolytes are encountering a great interest for the development of alkali metal (Li, Na, Mg, …) batteries. The use of magnesium metal as a negative electrode is of particular interest in post-lithium batteries as it has higher theoretical volumetric capacities and is more abundant in the earth’s crust than lithium. The first prototype system for a magnesium rechargeable battery included electrolytes based on magnesium organohaloaluminate salts, such as Mg(AlCl3R)2 and Mg(AlCl2RR′)2, in organic solvents such as tetrahydrofuran and glymes.1 These systems are based on the combination of a Lewis acid and Lewis base, to produce salts with active Mg species that promote facile and reversible Mg deposition. Recent advances include the development of so-called non-nucleophilic salts, which are less corrosive than the original strongly nucleophilic versions.2 However, these electrolytes are not stable in air and water, thus still present safety risks. Electrolytes containing air and water stable salts, e.g. Mg(TFSI)2, have significant advantages not only in terms of safety, but also in terms of chemical and electrochemical stability. Incorporating air and water stable salts into ionic liquids can result in electrolytes which, unlike those containing organic solvents, have low volatility and flammability.
Understanding Mg2+ solvation in ILs is one key step in the development of stable electrolyte systems which promote facile Mg2+ desolvation at the electrode surface. In this study, the intermolecular interactions between Mg2+ ands the IL anions and the impact of these interactions on the physical properties are examined. Furthermore, the transport mechanism of the Mg2+ in ionic liquid electrolytes is explored.
References
1. Aurbach, D.; Lu, Z.; Schechter, A.; Gofer, Y.; Gizbar, H.; Turgeman, R.; Cohen, Y.; Moshkovich, M.; Levi, E. Nature
2000, 407, 724-727.
2. Zhao-Karger, Z.; Zhao, X.; Wang, D.; Diemant, T.; Behm, R. J.; Fichtner, M. Adv. Energy Mater.
2015, 5, 1401155.
Physical and Chemical Analysis of Three Wide Electrochemical Window Ionic Plastic Crystals As Stable Electrolytes in Li-Ion Batteries
Authors: Stevenson Keith J , Dylla Anthony , O'Mahony Aoife 
Published: February 2020

Three ionic plastic crystalline solids were synthesized and analyzed to evaluate their suitability for use as electrolytes in Li-ion batteries: N-propyl-N-methylpiperidinium hexafluorophosphate (PP13PF6), N-propyl-N-methylpiperidinium tetrafluoroborate (PP13BF4) and piperidinium perchlorate (PPClO4). The physical and electro(chemical) properties will be discussed.Voltammetric analysis of the plastic crystals alone showed very wide electrochemical windows (>7.5 V) for PP13PF6 and PP13BF4, and a relatively wide window for PPClO4 (4V). Addition of the analogous lithium salts to each of these species (LiPF6, LiBF4 and LiClO4) in a 50:50 wt% ratio showed sluggish Li+ transport at room temperature, but improved when heated to temperatures greater than 45 °C. However, addition of 20 wt% of EC/DEC solvent increased Li+ transport dramatically, particularly for PP13PF6 and PP13BF4. Overall, a mixture containing LiBF4, PP13BF4 and EC/DEC displayed a stable wide electrochemical window of activity for several cycles and good Li+transport through the electrolyte rendering it a promising mixture for future use in Li-ion batteries.
Multifunctional Carbazole-Based Ionic Liquids
Authors: Kirankumar Rajendranath , Chen Po-Yu 
Published: February 2020

In this study, a new class of polymerizable ionic liquids were synthesized and modified upon conductive surfaces to enhance the sensitivity and/or selectivity of the electrodes, or to be electrochromic films. At suitable conditions, the poly-ionic liquids were soluble in some organic solvents.
Ionic liquids (ILs) have shown the advantages on electroanalysis when they were modified on electrode surface. Electropolymerization might be a good approach for the modification of ILs on conductive surface. Various carbazole-based ILs (Figure 1) were synthesized in this study and they were electropolymerized on indium tin oxide (ITO) electrodes by cyclic voltammetry in ILs BMP-TFSI, BMIm-PF6 and etc., as well as in conventional solvents (i.e. acetonitrile, methanol and DMSO)[1]. Electrochemical oxidation of the carbazole pendant units affords a conjugated polymer network (CPN) film of polycarbazole and the polymer is expected to have good conductivity on the conducting surface[2]. The electrode with electropolymerized ILs shows improved activity towards the oxidation of uric acid (UA), compared with that of unmodified electrodes. The polymerized ILs also exhibit electrochromic properties. The ITO electrodes modified with polycarbazole ILs show color change from deep green to pale yellow while the applied potential was scanned from +1.2 V to -0.2 V and vice versa.
On the other hand, bipyridinium (viologen) ionic liquids modified with carbazole via an alkyl spacer were synthesized and their electrochromic behavior in liquid state was studied in various ILs or conventional volatile organic solvents. Viologen is a well-known electroactive material with three different redox states: the dication, the radical cation and the neutral compound. The colors of radical cations depend on the groups substituted on the nitrogen atoms of the viologen moiety[3]. By introducing the carbazole groups, colors different from those observed for the traditional viologen compounds were recorded. This behavior is currently studied.

[1] D.-X. Zhuang, P.-Y. Chen, Journal of Electroanalytical Chemistry, 2009, 626: 197–200.

[2] Antonio F. Frau, Nicel C. Estillore and Rigoberto C. Advincula,ACS Appl. Mater. Interfaces, 2010, 2: 3726–3737.

[3] N. Jordao, L. Cabrita, F. Pina and L.C. Branco, Chem.-Eur.J., 2014, 20: 3982–3988.

Figure 1