bluuebunny/crossref_metadata_2025_split huggingface dataset:
Establishing Direct Electron Transfer in Cyanobacteria for Photocurrent Generation
Authors: Sekar Narendran , Ramasamy Ramaraja P. 
Published: February 2020

Cyanobacteria are used as anode catalyst in photo-bioelectrochemical cells to generate electricity in a sustainable, economic and environmental friendly manner. Though cyanobacteria (CB) have huge advantage for solar energy conversion through its robust photosynthesis, they could not perform extracellular electron transfer effectively as other electricigens. This is because, unlike electricigens such as Geobacter sp., CB do not possess any special key players on their outer membrane to carry out direct electron transfer. In this work, we genetically engineered a cyanobacterium named Synechococcus elongatus PCC7942 to express an outer membrane c-type cytochrome called OmcS1. The genetically modified CB (Eng-CB) enhanced the photocurrent generation significantly in photo-bioelectrochemical cells compared to that of wild type without the addition of any redox mediator. A specific redox peak corresponding to OmcS (~ 0.1 V vs Ag/AgCl) was observed in Eng-CB in a low-scan rate cyclic voltammetry (1 mV/s) and the same was found absent in the wild type. Both these evidences confirmed the establishment of direct electron transfer in Eng-CB. Also, extracellular electron transfer of the Eng-CB was investigated biochemically based on its ability to reduce the exogenously added soluble redox compound like potassium ferricyanide during its growth in BG11 medium. The enhanced ferricyanide reduction as well as photocurrent generation by the Eng-CB under both light and dark conditions elucidates the fact that the heterologously expressed OmcS could interact with both photosynthetic and respiratory electron transport chains. This work demonstrates the importance of interdisciplinary and integrated approach to enhance the photocurrent generation using CB and aid in advancing the understanding of biological interfaces with the electrode leading to for rapid development of photosynthetic microbial fuel cell technology.

References:

1. N. Sekar, R. Jain, Y. Yan, R. P. Ramasamy (2015) Biotechnol Bioeng. doi: 10.1002/bit.25829

Figure 1
The Effect of Cation Exchange Membrane on Long-Term Electromethanogenic Performance
Authors: Carpenter Kayla , Ishii Shino , Ishii Shunichi , Phadke Sujal , Babanova Sofia , Flynn Michael , Hogan John , Bretschger Orianna 
Published: February 2020

Bioelectrochemical systems offer a method to microbially harness the energy from unwanted compounds, such as wastewater, and use towards biosynthesis of beneficial compounds. Understanding the effects of the cation exchange membrane and other potential environmental stimuli is critical for developing bioelectrochemical systems that are robust and reliable. In this study, an electron-consuming community enriched from rice paddy soil was fed with a stable electron source via potentiostatic control of the working electrode to -700 mV vs. Ag/AgCl, and carbon dioxide as the sole inorganic carbon source. A subpassage technique was used as a selective pressure to enhance electron consumption and methanogenesis within the system. After relatively stable operation over a 250-day period along with sampling of the community to determine taxonomic composition, the cation exchange membrane was changed from Nafion®-117 to Ultrex®. While methane production remained consistent for an additional 450-day operation, there was a striking decrease in measured current consumption of the system (Fig. 1), which may also correlate to a change in the cathode microbial community and mechanism of energy recovery from the electrode (Fig. 2).
Results suggest that the properties of the cation exchange membrane are correlated to electrical system performance. Nafion is a physically thinner cation exchange membrane than the Ultrex material, and the physical differences in the membrane properties may impact the diffusion of protons and other molecules between the counter and working compartments. For example, it is possible that free radicals are formed at the counter electrode surface during poised-potential operation and may diffuse into the working chamber via the membrane. However, the presence of a thicker member (e.g. the Ultrex) in the system may minimize this diffusion effect and also limit the proton transfer, thereby leading to reduced electrochemical activity and alternative mechanisms for methane formation at the working electrode.
The taxonomic composition of the electromethanogic community was characterized using 16S rRNA gene sequences. The communities associated with the working electrode changed significantly when the membrane was switched from Nafion to Ultrex (Fig. 2). The relative abundance of methanogens (Euryarchaeota) increased from below detection to occupying nearly 60% of the community during the first subpassage after the membrane change. The relative abundance of the methanogenic population varied throughout operation with Ultrex membranes, but remained detectable and in high relative abundance for several subpassages. Interestingly, the relative abundance of Clostridia, α-, δ-, and ε-Proteobacteria also significantly changed throughout the duration of operation with the Ultrex membrane.

Figure 1
On-Body Energy Harvesting: Wearable Biofuel Cells
Authors: Jia Wenzhao , Banodkar Amay , Wang Joseph 
Published: February 2020

The presentation will discuss describe the development of textile- and tattoo-based flexible biofuel cells and batteries. We will illustrate the favorable electrochemical behavior of these wearable devices, and demonstrate the ability to generate substantial levels of electrical power from the human perspiration in a non-invasive and continuous fashion. Mechanical stress studies indicate that the printed devices survive large mechanical deformations. Technical challenges and prospects for using textile- and tattoo-based electrochemical biofuel cells and batteries will be discussed, along with several demonstrations and prospects for future on-body applications.

REFERENCES
[1] “Epidermal Biofuel Cells: Energy Harvesting from Human Perspiration”, W. Jia, G. Valdés-Ramírez, A. J. Bandodkar, J. R. Windmiller, J. Wang, Angew Chemie Int. Ed., 52(2013)7233.
[2] “Wearable Electrochemical Sensors and Biosensors: A Review”, J. R. Windmiller and J. Wang, Electroanalysis, 25(2013)29.
(Invited) Photovoltaic Proprieties and Photocatalytic Activity of Perovskite Oxide-Based Systems
Authors: Nechache Riad 
Published: February 2020

Photocatalytic water splitting with semiconductor materials has been investigated as a clean and
renewable process for directly converting sunlight into chemical energy. In particular, multiferroics MFs have recently
been used for applications in both photocatalysis (PC) and photovoltaics (PV) due to their ferroelectric properties and
narrow band gaps, allowing them to harness the majority of solar radiation in the visible range. As typical MFs,
BiFeO3 (BFO) and Bi2FeCrO6 (BFCO) have been recognized as potential materials for PV and visible-light PC
applications owing to their suitable band gap (1.4-2.8 eV) and good chemical stability. However, the investigations on
such materials for photocatalytic water splitting are still limited and efforts have to be undertaken to demonstrate their
full potential. An efficient PV system is at the basis on an effective PC process. Thus, the control of PV properties of
MFs is a critical issue for achieving highly efficient photocatalytic system. Here we will present, the controlled growth
and characterization of BFCO and BFO thin films and nanostructures via pulsed laser and hydrothermal techniques.
The PV properties of such systems and their photocatalytic activity will be also discussed
Insulator-Metal-Insulator-Semiconductor (IMIS) Photoelectrodes for Water Splitting
Authors: Esposito Daniel , Labrador Natalie Yumiko , Li Xinxin , Koberstein Jeffrey , Liu Yukun 
Published: February 2020

One promising approach to achieving stable and efficient photoelectrochemical (PEC) water splitting is the composite photoelectrode architecture known as a metal-insulating-semiconductor (MIS) photoelectrode. [1,2,3,4] Within the MIS design, metal catalyst is deposited on top of a thin insulating layer ( < 2 nm thick) that separates the metal from the semiconducting absorber layer. The insulating layer is particularly important because it can protect the underlying semiconductor from corrosion and avoid fermi-level pinning while still enabling efficient charge transfer between the semiconductor and metal through quantum mechanical tunneling. Through this composite design, the MIS architecture is able to decouple efficiency and stability, and has been applied to c-Si and InP photoelectrodes with great success in recent years, [1,2,3,4] For example, InP MIS photocathodes for the hydrogen evolution reaction have achieved photoelectrode conversion efficiencies up to 14%,[2] and n-Si MIS photoanodes have been demonstrated with stable operation in the highly oxidative environment of the oxygen evolution reaction for > hrs.[1]. Despite these encouraging results, further improvement in MIS photoelectrode performance is needed if this technology is to become commercially viable. In particular, improved photovoltage and maximized photo-current density generated by MIS photoelectrodes is essential for achieving DOE solar-to-hydrogen conversion efficiency targets.
In this work, electrodeposition has been explored as a potentially low-cost and scalable means of depositing ultra-low loadings (1 to 20 ng cm-2) of Pt nanoparticles onto SiO2-covered p-Si photoelectrodes. As-deposited MIS photoelectrodes are found to exhibit very poor durability, but we describe how this issue can be overcome through application of a thin secondary insulating layer to form an insulator-metal-insulator-semiconductor (IMIS) geometry. Surprisingly, it is found that the secondary insulating layer also results in a substantial improvement in the fill factor and short circuit current of IMIS devices compared to MIS photoelectrodes of identical loading. The combination of electrodeposition with the IMIS architecture thus offers an exciting opportunity for improving both the efficiency and durability of photoelectrochemical energy conversion. After presenting a side-by-side comparison of MIS and IMIS photoelectrode performance, we highlight reasons for the differences in their performance.
References:
[1] Y.W. Chen, P. McIntyre, et al., Nat. Mater., 10 (2011)
[2] M.H. Lee, et al., Angew. Chem. Int. Ed., 51 (2012).
[3] J.C. Lee, A. Bard, J. Ekerdt, et al., Nature Nanotech., 10, 84-90 (2015)
[4] D.V. Esposito,I. Levin, T.P. Moffat, and A.A. Talin.Nature Materials, 12, 562-568 (2013).
(Invited) Numerical Modeling of a Particle-Suspension Reactor for Solar Water Splitting
Authors: Bala Chandran Rohini , Breen Sasuke , Shao Yuanxun , Ardo Shane , Weber Adam Z 
Published: February 2020

Sunlight-driven water splitting offers the potential to store and transport transient solar energy in the form of stable chemical bonds as hydrogen. Existing technologies for solar water splitting—multijunction photovoltaic systems coupled to water electrolyzers and photoelectrochemical cells—have demonstrated efficiencies up to 18%, but are not cost-competitive with hydrogen from fossil fuels on an energy density basis. Particle-suspension reactor designs consisting of microscale photocatalysts suspended freely in the electrolyte are projected to be cost-competitive with hydrogen from gasoline and hence motivate this study. Of specific focus here is a vertically stacked, particle-suspension reactor (see figure below) evolving hydrogen (HER) and oxygen (OER) in separate compartments in the presence of a redox mediator/shuttle via a Z-scheme mechanism. Porous separators between the two reactor vessels facilitate ion transport while attenuating crossover of product gases. The tandem design facilitates the use of wide bandgap semiconductors in the top compartment and relatively narrow bandgap materials in the bottom compartment. A transient, two-dimensional, computational model has been developed to simulate the coupled light absorption, species transport and electrochemical reactions in a unit cell of the proposed reactor. The model is used to identify reactor dimensions that reduce mass transport limitations of the redox shuttle and maximize incident light absorption. Sensitivity of model results to optical properties of the photocatalyst and species diffusivities are studied. Results indicate sustainable solar-to-hydrogen conversion efficiencies of at least 1% for a chosen reactor design in the absence of forced convection, which is not only feasible with state-of-the-art photocatalytic materials but is close to a value that could be reasonably cost competitive with hydrogen from fossil sources.
Acknowledgments: This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Program of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and University of California, Irvine under award no DE-EE0006963.

Figure 1
Controlling the Product Syngas H2:CO Ratio through Pulsed Bias Electrochemical Reduction of CO2 on Copper
Authors: Kumar Bijandra , Brian Joseph Patrick , White Robert , Kumari Sudesh , Spurgeon Joshua M 
Published: February 2020

Copper is one of the most commonly studied materials for the electrochemical conversion of carbon dioxide (CO2) into valuable chemical products. Numerous efforts have been made to enhance the product selectivity - an important characteristic essential for efficient chemical production from CO2 - of Cu with only marginal progress. Here, we introduce a pulsed-bias technique for the electrochemical reduction of CO2 on Cu catalyst which led to 100% selectivity for CO formation over other carbon products and only produced syngas (CO + H2). X-ray photoelectron spectroscopy (XPS) and controlled CO2 electrochemical reduction experiments suggest that in-situ oxidation and reduction of the Cu causes the preference for CO formation over other carbon products on polycrystalline Cu. Moreover, the observed pulse waveform dependency of the H2 to CO product ratio can also be beneficial by allowing tunable CO2 reduction products as a controllable syngas feedstock for different industrial applications (e.g., Fischer-Tropsch process, and hydroformylation of alkenes to aldehydes) without an additional hydrogen source. This study opens a new route for the selective conversion of CO2 into syngas on robust and cost-effective Cu catalysts, which could be adopted at large scale in the chemical industry.

Keywords: Copper, Catalyst, CO2reduction, Syngas, Selectivity, Electrochemistry
(Keynote) Detecting Small Molecule-Membrane Protein Binding Kinetics
Authors: Tao Nongjian 
Published: February 2020

Detection of molecular interactions is critical for understanding many biological processes, for detecting disease biomarkers, and for screening drug candidates. To date the most widely used detection technique uses fluorescence dyes. While useful, the approach can be problematic when applied to the detection of small molecules, because the dye molecules may significantly alter the binding activities of the small molecules. Label-free detection techniques have been developed, but they largely rely on the detection of the mass of a molecule, which are difficult for small molecules. Small molecules are the most popular form of drugs, and play important roles in many biological processes, including post-translational modification of proteins, metabolic and cellular signaling processes. A capability to detect small molecules will have large impacts on the understanding of these processes, detecting of diseases, and discovery of drugs.
We show that molecular interactions with membrane proteins induce mechanical deformation in cellular membrane, and real-time monitoring of the deformation allows quantitative analysis of membrane protein binding kinetics. This new strategy provides mechanical amplification to small binding signals, which, together with a differential optical detection algorithm to track cell deformation with 0.5 nm accuracy, make it possible to detect small molecule interactions with membrane proteins. This capability also allows study of heterogeneous nature of cells by analyzing the binding kinetics variability between different cells, and different regions of a single cell.
Monitoring of Nitric Oxide Levels Released from NOS-Loaded Liposomes in Proximity of Cystic Fibrosis Cell Line Models
Authors: Bayachou Mekki , Bose Tiyash , Henderson Tericka 
Published: February 2020

Nitric oxide (NO) is a biological free radical, associated with many physiological and pathological processes that include neuronal signaling, immune response and inflammatory response. In mammalian organisms, NO is produced from L-arginine in an NADPH-dependent reaction catalyzed by a family of nitric oxide synthase (NOS) enzymes. Fluctuations in NO levels generally accompany a number of inflammatory diseases. Cystic Fibrosis (CF) is an autosomal recessive genetic disease that chronically affects the lungs. It has been found that exhaled NO levels remains unchanged or reduced in cystic fibrosis patients unlike other inflammatory lung diseases like asthma where it increases. However it is not clear whether the lower NO levels in cystic fibrosis correlate with lowered production of this metabolite in the bronchial epithelium. Also, it has been proposed recently that nitric oxide can be used as a potent antimicrobial molecule to treat bacterial infection of CF tissue. Nitric oxide’s role in CF is mutlifaceted. In this work, we want to establish a basic system to understand how nitric oxide interacts with CF cells versus normal cells by monitoring levels of nitric oxide released from NOS-loaded liposomes on normal cells and CF cells.
We will present work establishing the performance of combined reference/working electrodes modified with ruthenium oxide and poly(3,4-ethylenedioxythiophene) (PEDOT) for catalytic detection of nitric oxide. We will then show how we can use this nitric oxide sensitive probe to measure levels of nitric oxide from NOS-loaded liposomes. In this case, nitric oxide is triggered exogenously both in proximity of normal cells and near a CF cell line model. We will compare and contrast the observed amperometric levels of nitric oxide and discuss the results in light of potential biological implication of nitric oxide with the two cell models.
Ethanol Gas Sensing Behavior of ZnO Nanorods Decorated with Various Metal Catalysts
Authors: Park Hyejin , Lee Eunji , Chung Yoonsung , Kim Dong-Joo 
Published: February 2020

Solid gas sensors are widely employed owing to their good stability and excellent gas responses [1]. However, the operating temperature to activate reaction sites of oxide semiconductor is relatively high to widen the applications [2]. As demands of gas sensors have increased in various fields, one of the research issues is to lower the operation temperature to enhance adaptability. To lower sensing temperature of semiconductor oxide sensors from several hundred Celsius to room temperature and to improve the gas selectivity, compositional gradient of catalysts was explored based on the catalyst effects on gas sensing mechanism and performance. Two metals having different catalytic activities were utilized: Platinum (Pt) and palladium (Pd). The thickness of the catalyst layer was kept constant, and only composition (ratio of the components) was changed to investigate the effect of the catalyst composites [3].
In this study, deposition of metal catalysts on ZnO NR gas sensing devices was successfully conducted by the sputter method. Pd and Pt were selected as catalysts to improve the gas sensing behaviors such as gas response, gas response rate, and selectivity. The amount of 1 or 2 % of catalysts was deposited on the gas sensing devices. When metal catalysts were applied, operation temperature of ZnO NR gas sensors was successfully reduced from 300 °C to 100 °C. Moreover, enhancement in gas sensing behaviors was observed with catalysts but degraded gas sensing behavior occurred with large amount of the catalysts. Improvement was resulting from the increase in activate sites and modification of the Fermi energy level. The degradation was primarily due to the blockage of activate sites caused by excessive amounts of catalysts. Catalysts decorated ZnO NR gas sensors can be a candidate for lowered operating temperature with great gas responses.
This research was partially supported by the Korea Institute of Energy Technology Evaluation and Planning (20158520000210) grant funded by the Korea Government Ministry of Trade, Industry and Energy, a grant from a Strategic Research Project (2013-0132) funded by the Korea Institute of Construction Technology, and Auburn University IGP.

[1] Azad, A. M., et al. Journal of the Electrochemical Society 139.12 (1992): 3690-3704..

[2] Morrison, S. Roy. Sensors and actuators 12.4 (1987): 425-440..

[3] Müller G, Friedberger A, Kreisl P, Ahlers S, Schulz O, Becker T. Thin Solid Films. 2003;436(1):34-45.

Figure 1
Development and Characterization of Fuel Cell Sensor for Potential Transdermal Ethanol Sensing
Authors: Jalal Ahmed Hasnain , Umasankar Yogeswaran , Bhansali Shekhar 
Published: February 2020

The existing fuel cell alcohol sensors [1-3] suffer severely with humidity interference and signal instability. This interference and instability renders the existing sensors useless for transdermal ethanol detection in non-ideal environment. To address these issues of the fuel cell alcohol sensor, various electrode designs along with the catalysts were explored in this work. The design includes both two and three electrode setups with the Nafion as proton exchange membrane, where the three electrode setup provided stable signal compared to two electrode setup. Considering the development of a potential transdermal ethanol sensor, the ethanol exposed area of the working electrode was optimized to 1cm2and reference and counter electrode were placed on the other side of the Nafion membrane. For the ethanol measurements in the three electrode system, a fixed potential was applied between working and reference electrode and the change in current due to ethanol concentration was measured between working and counter electrode. To eliminate the interference due to humidity the applied potential for measurement was same as that of the open circuit potential (OCP) of the fuel cell in presence of humidity. Catalysts such as Ni, Cu, Fe and Au were studied, where Ni has better catalytic activity for ethanol oxidation and oxygen reduction [4] providing almost 600, 300 and 3 times greater current response than Au, Fe and Cu respectively (Figure 1). The sensitivity for the sensor was found 0.062 nA/ppm in vapor phase for this Ni catalyst.

Figure 1: Amperometric responses of fuel cell sensor for ethanol (a) Fe, (b) Au, (c) Ni and (d) Cu catalysts.

Acknowledgements:

This work is funded by the ASSIST NSF ERC and NSF I-Corps Teams.

References:

1. Jeng, K.-T.; Huang, W. M.; Chien, C. C. and Hsu, N.-Y. 2007. A versatile electrochemical fuel sensor for direct membrane fuel cell applications. Sens Act B: Chem 125:278-283.
2. Jiang, L.; Zhou, Z.; Wang, S.; Liu, J.; Zhao, X.; Sun, G.; Xin, Q. and Zhou, B. 2004. Development of air-breathing direct ethanol fuel cells with PtSn as anode. Prepr Pap-Am Chem Soc, Div Fuel Chem, 49:668-670.
3. Robertson, R.; Vanlaar W. and Simpson, H. 2007. Continuous transdermal alcohol monitoring: A primer for criminal justice professionals. The Traff Inj Resc,ISBN: 978-0-920071-60-1.
4. Barbosa, A. F. B.; Oliveira, V. L.; Drunen V. and Tremiliosi-Filho, G. 2015. Ethanol electro-oxidation reaction using a polycrystalline nickel electrode in alkaline media: Temperature influence and reaction mechanism. J. of
Electroanal Soc, 746: 31-38.

Figure 1