bluuebunny/crossref_metadata_2025 huggingface dataset:
A Highly Porous and Conductive Composite Gate Electrode for NO, NO2, O2, H2 and NH3 Exhaust Gas Sensors
Authors: Chahdi Hassane Ouazzani , Helli Omar , Bourzgui Nour-Eddine , Breuil Léo , Danovitch David , Voss Paul L. , Sundaram Suresh , Aubry Vincent , Halfaya Yacine , Ougazzaden Abdallah , Salvestrini Jean-Paul , Maher Hassan , Soltani Ali
Published: May 2020

The real-time knowledge of the NO, NO2 and NH3 concentration at high temperature, would allow manufacturers of automobiles to meet the upcoming stringent EURO7 anti-pollution measures for diesel engines. Knowledge of the concentration of each of these species will also enable engines to run leaner (i.e. more fuel efficient) while still meeting the anti-pollution requirements. Our proposed technology is promising in the field of automotive sensors. It based on AlGaN/GaN high electron mobility transistor (HEMT) sensors incorporating highly porous platinum in the gate. Compared to platinum full gate AlGaN/GaN HEMT sensor, the Highly porous gate sensor has dramatically improved current response to O2, NO, NO2 H2 and NH3, to the NO concentration in the range of 0–2000 ppm, 0-2500 ppm NO2, 0-300 ppm NH3, (1.5-10%) H2 and O2 (1.5-100%) species at high temperature (500 °C). This improvement in sensitivity is the result of the increase in catalytic surface area interaction between gas and platinum.

Keywords—HEMT, sensors, GaN, H2, O2, NO2, NO, NH3 high temperature, highly porous gate.
WITHDRAWN: Organic Field Effect Transistor (OFET) for H2S sensing Using Tris(keto-hydrozone)
Authors: Yuvaraja Saravanan , Surya Sandeep , B.N Veerabhadraswamy , C.V Yelamaggad , Salama Khaled Nabil
Published: May 2020

This abstract has been withdrawn at the request of the authors.
Preparation of Efficient Memristive Films (2D materials) for Flexible Devices and Their Electrical Characterisation
Authors: Osayemwenre Gilbert
Published: May 2020

2D materials have various properties which make them potential candidates for better applications in electronic, chemical and biosensing devices. It is certain that so much work have previously been done on 2D materials. However, the aim of this study is to fabricate a material with a better quality that could create room for greater opportunities in electronic, chemical and biosensing devices. This fabrication was performed through exfoliation, and wet chemical means or PVD layer deposition technique. Furthermore, the current state of the electronics industry has necessitated the need for a novel and suitable memory for low cost and large scale flexible electronics materials. These materials should be non-volatile and low-power consuming devices because energy is of global concern. The non-volatility nature and the energy consuming ability of the finally fabrication was investigated from the current vs time curve in order to obtain the energy retention time. After the fabrication of the electronics material, various characterisations were performed on the devices; stability and endurance level was tested from the current vs cycle numbers of the curves. The rationale for these experiments is to take advantage of the Van der Waals multilayer force present in-between the layers of the two-dimensional (2D) materials to form a material with a desirable atomic and accurate quality. The outcome shows improve 2D memeristive material required to address most challenges experienced by electronic devices, particularly in the multilayer thin film. The result shows performance improvement of the memristors by raising the switching endurance at an elevated temperature of 300 oC and above. Finally, the mechanical flexibility and stability together with its endurance level were tested.
Micromechanical Resonators for Ultrasound-Based Sensors
Authors: Farhoudi Navid , Laurentius Lars B , Reiche Christopher F , Magda Jules , Solzbacher Florian
Published: May 2020

The current field of sensor platforms is substantial, and ever more creative approaches are envisioned and realized. Herein, we showcase a new platform technology for continuous sensing that relies on the resonant absorption of ultrasound waves in a microfabricated array of smart hydrogel structures (see Figure 1).[1] Smart hydrogels are biocompatible and can be tailored to respond to different analytes. [2,3] These selective materials undergo a volume-phase transition in response to changing levels of biomarkers. In addition, smart hydrogels can be based on compositions that include poly(ethylene glycol), poly(methyl methacrylate), or hyaluronic acid to be designed to biodegrade. By employing smart hydrogels as resonator structures and probing them using ultrasound will provide an implantable sensor platform that is minimally invasive, non-destructive, and free of transcutaneous wires.

This approach makes use of the fact that hydrogels can be molded into mechanical microresonators that are tuned to a specific ultrasound frequency. As they swell or contract in response to the presence or absence of the target analyte, their resonance frequency changes, leading to a shift in the ultrasound absorption spectrum. Measuring these changes allows for the reconstruction of the analyte concentration. In addition to that, tailoring the resonance frequency of the smart hydrogel resonator structures to different frequency ranges allows for multiplexing. We successfully demonstrate the use of this platform technology using glucose as a target metabolic marker in-vitro and in-vivo in rats (see Figure 2).

Florian Solzbacher declares financial interest in Blackrock Microsystems LLC and Sentiomed, Inc. Jules Magda declares financial interest in Applied Biosensors LLC.

[1] N. Farhoudi, H.-Y.L., J. Magda, F. Solzbacher and C.F. Reiche, A Biomedical Sensor Based on Resonant Absorption of Ultrasound Waves in Hydrogel-based Resonators. TechConnect Briefs 2019, 2019: p. 412.

[2] Buenger, F. Topuz, and J. Groll, “Hydrogels in sensing applications,” Prog. Polym. Sci., vol. 37, no. 12, pp. 1678–1719, 2012.

[3] A. Peppas, J. Z. Hilt, A. Khademhosseini, and R. Langer, “Hydrogels in biology and medicine:From molecular principles to bionanotechnology,” Adv. Mater., vol. 18, no. 11, pp. 1345–1360, Jun. 2006.

Figure 1
Leveraging Preconcentration and Partial Separations with Silicon Nanowire Arrays to Improve the Detection of Low Volatility Trace Explosive Vapors
Authors: Mullen Matthew , Giordano Braden
Published: May 2020

Trace detection of explosive vapors in real world environments is hindered by strict sensitivity and selectivity requirements that need to be met in order for these techniques to be effective. The physical properties of most explosive molecules limit environmentally relevant vapor concentrations to the part per billion (ppbv) – part per trillion (pptv) range due to their saturated vapor pressures under real world conditions. Additionally, trace explosive vapor detectors must be able to discriminate against a number of potential chemical and biological interferents present in complex real world environments. In this work, we present silicon nanowire arrays (SiNW) as a novel tunable material aimed at providing trace explosive vapor detectors with the sensitivity and selectivity necessary for operational use.

Dense, highly ordered silicon nanowires are fabricated through a nanosphere lithography process and topped with a porous gold electrode resulting in a high surface area adsorptive substrate intrinsically capable of rapid, precise temperature control via Joule heating. Explosive vapors are selectively preconcentrated onto the SiNW array by exploiting their affinities for the SiO2 surface of the nanowires. Chromatographic like partial separations of preconcentrated material on the array can be achieved through careful selection of desorption parameters. Using a multichannel detector such as an IMS or MS we demonstrate the preconcentration of a number of explosive vapors including 2,6-DNT, TNT, and RDX above and below their saturated vapor concentrations at room temperature, in addition to exploring the effects of desorption flow rates and temperatures on the partial separation of 2,6-DNT, 2,4-DNT, and TNT vapors.

Figure 1
Multishell Nano Structure for Enhancing Fluorescence
Authors: Lin Longhui , Chen Xi , Li Jian-Feng
Published: May 2020

As an important part of plasmon-enhanced spectroscopy technology, metal surface-enhanced fluorescence provides an effective approach for surface analysis and detection. Our group is interested in exploring how the plasmon effect interacts with emission of probes, such as quantum dots, dye molecules, clusters, rare earth luminescent materials. And we also apply SPR into electroluminescence and chemiluminiscence.

Recently, we have fabricated a type of multishell nano structure which consists of an Au core, an interstitial nanoscale SiO2 layer, and an Au shell layer. Its plasmonic properties result from the strong interaction between the plasmon modes of the Au core and the Au shell, giving rise to hybridized modes that can be tuned into the NIR, for particle sizes below 100 nm in diameter. These interactions also give rise to a strong Fano resonance in the visible region of the spectrum, appearing as an asymmetric modulation in the far-field extinction spectrum of the nanoparticle. Additionally, a monolayer of dye molecules (Cy5.5) was embeded into inner SiO2 layer. Finally, the highest enhanced fluorescence has achieved up to almost 30-fold.The combination of compact size and enhanced light emission with internal encapsulation of the fluorophores for increased biocompatibility suggests outstanding potential for this type of nanoparticle complex in biomedical applications.

Figure 1
Electrochemiluminescence Investigation of Atomically Precise Gold Nanoclusters Decorated with a Bulky Ligand
Authors: Hesari Mahdi , Ding Zhifeng
Published: May 2020

Electrochemiluminscnce (ECL) is about light generation in the course of an efficient electron transfer in the vicinity of an electrode. ECL has been propagated at the interface of electroanalytical and spectroscopic techniques, and has found worldwide applications in, for example, healthcare, physical and analytical chemistry fields. There have been a vast number of molecules and nanomaterials that are examined as ECL emitters. Among those emitters atomically precise thiolate–protected gold nanoclusters stood out rapidly owing to their well-defined geometric structures and inherent molecular-type opto-electronic properties. Recently, we showed that these gold nanoclusters emit ECL at Near-IR region, that is well-suited for biological applications (e.g., bio-imaging).1 Here, we report one–pot preparation of a gold nanocluster that decorated with a bulky aliphatic ligand (e.g., tert-buthyl thiol). The ECL mechanistic investigations, using conventional and newly established ECL spooling spectroscopy, show that this nanocluster emits ECL light at the Near-IR region.

(1) Hesari, M.; Ding, Z., Acc. Chem. Res.
2017, 50, 218.
Amplification-Free Point-of-Care microRNA Detection in Urine Using Molecular Beacon Based Electrochemiluminescence
Authors: Kerr Emily , Henderson Luke C , Prieto-Simon Beatriz , Voelcker Nicolas H
Published: May 2020

The burgeoning field of miRNA detection using electrochemiluminescence (ECL) has garnered a great deal of attention in recent times.1 ECL presents many advantages over alternative detection strategies as ECL analyses generally exhibit low-background signals, high sensitivity, are reproducible and scale-able.2 When combined with magnetic-beads for the immobilisation of biological recognition elements, ECL biosensors offer exceptional sensitivity owing to the ability to disperse the beads in large sample volumes to capture the biological target of interest via mixing then concentrate prior to analysis via magnetic extraction.3, 4

Herein, we present a novel biosensor for the sensitive detection of miRNA-21 comprising a molecular beacon ECL probe immobilised on magnetic beads. We obtained a limit of detection of 500 attomoles for miRNA-21 without enzymatic amplification or the addition of detection probes or intercalating labels, negating the need for lengthy and stringent washing procedures to reduce the background signal. Furthermore, we demonstrate the immense potential for point-of-care applications by developing a fully integrated miRNA detection platform. The platform comprises a mini-potentiostat for ECL generation, integrated silicon photodiode for ECL detection and a custom 3D-printed cell holder to readily interface a disposable screen-printed electrode with the potentiostat and photodiode.

We applied our magnetic miRNA extraction technology to the detection of miRNA-21 in human urine, a promising biomarker for the early diagnosis of chronic kidney disease.5 Urine is an ideal sample matrix as it is non-invasive to obtain in large volumes, does not require a phlebotomist to acquire and miRNAs in urine are stable in exosomes. When combined with point-of-care miRNA extraction methods, the molecular beacon based ECL system we have developed presents a promising tool for point-of-care diagnosis and management of numerous diseases.

1. P. K. Kalambate, N. S. Gadhari, X. Li, Z. Rao, S. T. Navale, Y. Shen, V. R. Patil and Y. Huang, TrAC, Trends Anal. Chem., 2019, 115643.

2. Y. Cheng, L. Dong, J. Zhang, Y. Zhao and Z. Li, Analyst, 2018, 143, 1758-1774.

3. M. H. Shamsi, K. Choi, A. H. Ng, M. D. Chamberlain and A. R. Wheeler, Biosens. Bioelectron., 2016, 77, 845-852.

4. W. Liu, X. Zhou and D. Xing, Biosens. Bioelectron., 2014, 58, 388-394.

5. M. L. Alvarez, M. Khosroheidari, R. Kanchi Ravi and J. K. DiStefano, Kidney Int., 2012, 82, 1024-1032.
Transferable ZTO Micro-Spheres Monolayer Based UV Photodetectors
Authors: Jung UiJin , Shin Dong Su , Peng XianZhan , Sang Chengwen , Park Jinsub
Published: May 2020

Zinc-tin-oxide (ZTO) is very attractive materials due to similar optical and electrical properites to those of ZnO. In addtion, the morphology control of ZTO nanomaterials such as nanowires, cubu, sphers etc is possible by using solution based synthesis methods. In this presentation, we reprot on the metal-semiconductor-metal (MSM) UV photodetectors consisting of transferable ZTO microspheres (MSs) monolayer with different phases. To investigate the effects of different phases of ZTO MS on the UV detection performance, the transferrable amorphous ZnSnO3 (a-ZTO) and crystallized Zn2SnO4 (c-ZTO) MSs monolayer were formed. From the fabricated UV detectors with different phases, c-ZTO MS monolayer based photodetectors are superior to a-ZTO base ones in device performance . The external quantum efficiency of c-ZTO MS based UV photodetector shown 580.9% (at 310nm) and the UV-to-visible rejection ratio of the c-ZTO exhibited over 1400, which indicated that our fabricated ZTO MS UV photodetectors have great visible-blind properties. For the further improvement of optoelectronic device performances, the c-ZTO MS-based UV photodetectors was optimized using with various sphere’s diameters. Our suggested facile transferable ZTO MS monolayer based optoelectronic devices have excellent potential to open a new way for various photonic and electronic applications
Durable Copper Nanostructures for on-Chip Plasmonic Devices
Authors: Hughes Robert A. , Preston Arin , Neretina Svetlana
Published: May 2020

The stability and durability of plasmonic materials is a subject of fundamental importance that can decide whether a technology is viable, reliable, and sustainable. Such considerations become amplified for plasmonic applications requiring that the nanostructures operate at elevated temperatures. With plasmonics being a field of study that is powered by the ability to shape- and size-engineer metals at the nanoscale, the tendency for these same structures to oxidize and morphologically reconfigure when heated can disrupt or destroy properties that were so carefully engineered in the first place. Here, we report on a strategy capable of yielding substrate-based plasmonic nanostructures that are robust to oxidation, etchants, and high temperatures. It is reliant on the formation of substrate-immobilized single-crystal nanostructures to which an ultrathin protective cladding is applied. It will be shown that suitably clad Au structures with far from equilibrium geometries are able to maintain their shape at temperatures as high as 800 °C. Using the same cladding, Cu structures are resistant to oxidation in air at temperatures as high as 600 °C. In both cases, the plasmonic properties, while modified by the application of the cladding, remain unchanged when heated. Together, the work provides a fundamental understanding of high-temperature diffusion processes occurring for clad metals and advances the processing science needed to manufacture durable plasmonics.
Carbon Dots: Synthesis, Characterization and Sensing Applications
Authors: Ma Xiaoyu , Wang Xudong , Lei Yu , Zhao Jing
Published: May 2020

Carbon dots are emerging environmental-friendly fluorescent nanomaterials which exhibit excitation wavelength dependent fluorescence, high quantum yield and offer good biocompatibility. Carbon dots can be synthesized in both water and oil using hydrothermal methods. Typically, carbon containing precursors (often small organic molecules) are heated and carbonized under elevated temperature. In the first study, we developed a heating equipment-free method to synthesize carbon dots using citric acid and 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl (EDC). Taking advantage of the heat released by the reaction itself, no external heating is required to form carbon dots. The carbon dots had a fluorescence peak at 480 nm. They were applied for fluorescence-based Fe3+ sensing and showed decent sensitivity and selectivity. In another study, carbon dots were synthesized in the hydrophobic phase following previous literature. The carbon dots were introduced into a lipid bilayer and voltage was applied across the bilayer. The fluorescence intensity of the carbon dots showed voltage-dependence due to Stark effect, demonstrating their potential in membrane voltage sensing application.
Manifestation of Mass-Transport Processes in the Electrochemical Impedance Spectroscopy Features of V2+/V3+ and VO2+/VO2
+ Redox Couples
Authors: Leuaa Pradipkumar , Neergat Manoj
Published: May 2020

Effect of mass-transport processes on the electrochemical impedance spectroscopy (EIS) features of V2+/V3+ and VO2+/VO2
+ redox reactions in acid electrolyte is illustrated on modified glassy-carbon disk electrode. The impedance features depend on the electrode potential, concentration of the redox species, concentration of the supporting electrolyte and constituents of the electrode. The results show that a combination of voltammetry and EIS is required to identify and explain the underlying physical processes that lead to the formation of specific EIS features. Optimum concentration of the vanadium redox species and supporting electrolyte is required to resolve the HF and LF semi-circles in the EIS features corresponding to the electron-transfer process and transport of vanadium ions, respectively. Nafion and Polytetrafluoroethylene (PTFE) binders are used to bind the carbon-black catalyst on the glassy carbon disk electrode surface. The binder-free electrode shows finite and semi-infinite linear transport of redox species under the dynamic and static conditions of the electrode, respectively. Addition of binder in the electrode offers extra resistance to the transport of vanadium redox species, which helps resolve EIS features of the transport of redox species through the porous thin-film electrode and that through the bulk of the electrolyte

Figure 1
Degradation of Carbon Electrodes in the Vanadium Redox Flow Battery
Authors: Singh Ashutosh Kumar , Yasri Nael , Pahlevaninezhad Maedeh , Roberts Edward P.L.
Published: May 2020

The Vanadium Redox Flow Battery (VRFB) is a promising candidate for large scale energy storage. These systems are expected to operate for long cycle life ~ 10 years of lifetime (~ 500 - 2000 charge – discharge cycles).1 The VRFB’s system includes an posolyte (VO2
+/VO2+) and negolyte (V2+/V3+) compartments with carbon electrodes, and uses acidic electrolytes (usually 3M H2SO4). The carbon electrodes in VRFB need to perform in a harsh and corrosive environment associated with the charge/discharge cycling. In this study, we used polyacrylonitrile (PAN) based carbon papers as model carbon electrodes to study changes in the electrodes during cycling operation. The carbon papers were pre-treated according to the conventional approach by heating them in air at 500 ⁰C to incorporate oxygen functional groups on their surfaces.2,3 These pre-treated electrodes were then used in flow battery for 100-cycles at a current density of 80 mA/cm2. At the single cell level, the performance of these electrodes following the operation indicated a slight decrease in voltage efficiency (from 60 % to 52 %). This decrease in performance may be attributed to the electrode degradation during operation. Characterization of the electrode prior and following 100-cycles was performed using Raman spectroscopy, XPS analysis as well as electrochemical studies. Raman analysis showed differences between the fresh and the degraded carbon electrodes, including increasing defect and electronic density distribution. XPS analysis of the degraded electrodes suggest an alteration in the amount of oxygen functional groups. Electrochemical studies showed an decrease in the electron transfer kinetics after degradation, coupled with noticeable difference between the electrodes exposed to the posolyte (VO2
+/VO2+) and negolyte (V2+/V3+). The results provide insight into the stability of the oxygen functional groups during cycling operation which could assist in developing pre-treatment methods to functionalize the VRFB’s electrodes and for other similar electrochemical systems.

References:

(1) Soloveichik, G. L. Flow Batteries: Current Status and Trends. Chem. Rev.
2015, 115, 11533–11558.

(2) Singh, A.; Yasri, N.; Karan, K.; Roberts, E. P. L. Electrocatalytic Activity of Functionalized Carbon Paper Electrodes and Their Correlation to the Fermi Level Derived from Raman Spectra. ACS Appl. Energy Mater.
2019, acsaem.9b00180.

(3) Singh, A. K.; Yasri, N.; Karan, K.; Roberts, E. P. L. Effect of Pretreatment on Carbon Materials. Meeting. Abstract.
2018, MA2018-01, 2391.
Low-Cost and High Rate Na-FeCl2 Batteries for Large Scale Energy Storage Applications
Authors: Zhan Xiaowen , Bonnett Jeff F , Reed David , Sprenkle Vincent , Li Guosheng
Published: May 2020

Developing battery systems that are inexpensive, enduring, and safe is essential for integrating renewable energy sources such as solar and wind power into the electricity grid and providing valuable grid services such as frequency regulation, peak shaving, and arbitrage. In this regard, Na-based batteries are promising candidates because they use naturally abundant sodium (Na) as the charge carrier, which can potentially reduce the materials cost and support multiple energy storage applications. Among various Na-based batteries developed to date, thorough investigations have been done on high-temperature (~300°C) Na-metal halide (Na-MH) batteries, which offer long cycle life and superior safety. In particular, the tubular sodium-nickel chloride (Na-NiCl2 or Zebra) battery has been commercialized and found wide application in the telecom and oil/gas industries. However, the high operating temperature and cost of the Zebra battery has hindered its further market penetration. Considering constraints of the Ni-based cell chemistry, it is highly desirable to develop an alternate cathode for Na-MH batteries towards next-generation energy storage applications. This pursuit, unsurprisingly, led us to the Fe/NaCl cathode. In this study, we present an advanced Na-FeCl2 battery with unprecedented high-rate performance and low cost for stationary energy storage applications. Operated at an extremely high current density of 33.3 mA/cm2 at 190°C, the cell can output 74% of its total capacity—a capacity retention double that of IT Na-NiCl2 cells. The origin of the high rate capability of Na-FeCl2 batteries was elucidated by means of comprehensive phase/structure analysis and electrochemical/electroanalytical characterizations. Moreover, Fe particle pulverization originating from liquid-phase reactions was determined to be the major source of capacity fading during long-term cycling. Accordingly, we designed a unique cathode with Ni additive, which delivered a high discharge specific energy density of over 295 Wh/kg for 200 cycles at C/5 with almost no capacity fading.
Enhancing the Performance of a Zinc-Iodide Redox Flow Battery
Authors: Shakeri Hosseinabad Fatemeh , Roesler Roland , Roberts Edward P.L.
Published: May 2020

A very high energy density has been reported for the zinc-iodide flow battery [1]. In order to enhance the performance of a zinc-iodide flow battery, an iodide-based complexing agent (1-cyanomethyl-1-methylpyrrolidinium iodide) was added to a 3.0 M ZnI2 electrolyte system. An optimized flow field design for uniform distribution of the electrolyte is desirable for the redox flow battery systems. The impact of flow field design on the performance of the battery was investigated.

Charge-discharge characteristics were carried out to investigate cyclability and efficiency of the zinc-iodide battery with and without the presence of complexing agent. The flow cell used graphite felt electrodes, a Nafion membrane, and had an active area of 5 cm2. In this study, the influence of a flow through design, and a flow-by design on the performance of the zinc-iodide flow battery was evaluated. Electrochemical characterization methods, including cyclic voltammetry (CV) and rotating disk electrode (RDE) studies, with and without the presence of complexing agent were performed to evaluate redox potential, diffusion coefficient and electrochemical reversibility of the electrolyte system. The deposited material on the positive and negative electrodes and stability of the electrode material were studied by SEM, EDX, XRD and Raman.

[1]- Li, Bin, Zimin Nie, M. Vijayakumar, Guosheng Li, Jun Liu, Vincent Sprenkle, and Wei Wang. "Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery." Nature communications 6 (2015): 6303.
Thin Membranes for PEM Water Electrolysis and the Challenge to Reduce Hydrogen Permeation
Authors: Stähler Markus , Stähler Andrea , Scheepers Fabian , Lehnert Werner , Carmo Marcelo
Published: May 2020

In order to reach the system efficiency targets for PEM water electrolysis of more than 70%LHV at current densities of up to 3 A/cm², thin membranes are indispensable. It is known that the use of thin membranes leads to the disadvantage that they additionally have to be stabilized mechanically and chemically for cell operation. Furthermore, it is known that during pressure operation, a large amount of gas permeates through the thin membrane. This can result in forming explosive gas mixtures of oxygen and hydrogen at the anode, especially at low current densities, which prevents a safe electrolysis operation. However, little research has been done so far that, when using thin membranes, additional effects can arise which significantly increase the gas permeation. These effects lead to safety-relevant hydrogen concentrations at the anode, not only for small but also for larger current densities of a few amperes per square centimeter.

It is demonstrated that, without an intensive comparison of material and cell operating parameters, a comparison of different investigations with respect to the measured permeation values in PEM water electrolysis can hardly be made. Important parameters are discussed which have to be taken into account in cell assemblies when thin membranes are used.

The presented experimental results show a correlation in the PEM water electrolysis MEA which can significantly increase the hydrogen permeation through a 50 μm thin N212 membrane under ambient pressure. At the same time, it is demonstrated how the hydrogen content in the anode gas can be reduced to very low levels using the identified correlation.
High-Pressure Polymer Electrolyte Membrane Water Electrolyzers: Is It Worth It?
Authors: Scheepers Fabian , Stähler Andrea , Stähler Markus , Müller Martin , Lehnert Werner , Carmo Marcelo
Published: May 2020

As a future fuel hydrogen should be stored at elevated pressure because of its low volumetric energy density. For transport in pipelines, a suitable pressure is about 200 bar. There are different paths conceivable to achieve this storage pressure. As an alternative to the conventional way of compressing the gas in external compressors subsequently, it is frequently discussed to operate electrolyzers at elevated pressure, which can save costly compressor stages. High Faraday efficiencies will be achieved by using improved materials with low permeation rates or thick membranes. However, thick membranes worsen the system performance since the decreased protonic conductivity of the cells ultimately reduces the amount of hydrogen produced. Therefore, it is recommendable to take a closer look at this context and to evaluate an optimized pressure operation depending on the application and cell parameters. In a comprehensive analytical model approach we discuss how voltage efficiency, Faraday efficiency and energy required for external gas compression are affected by a various number of system parameters. We demonstrate that the optimum gas pressure in electrolyzers is not only a function of the membrane thickness but strongly depends on the entire system configuration. To answer the question of whether high-pressure polymer electrolyte membrane electrolyzers are worthwhile both energetically and economically, our model was fed with a typical parameter set for systems based on Nafion 212 and Nafion 117. Our results demonstrate impressively why the use of thin membranes and their future development are a must for the meaningful use of PEM water electrolysis in a future energy grid.
Voltammetric Biosensor Based on Silver Nanowires and Tyrosinase for the Electrochemical Detection of Catechol
Authors: Salvo-Comino Coral , Rodriguez-Valentin Javier , Gonzalez-Gil Alfonso , Garcia-Cabezon Cristina , Rodriguez-Mendez Maria Luz
Published: May 2020

An enzymatic electrochemical biosensor for catechol detection based on silver nanowires (AgNWs), has been developed. The employment of AgNWs was essential to improve the electron transfer in comparison with that offered by an ITO substrate. AgNWs’ electrocatalytic properties and high affinity with biomolecules make them desirable for constructing biosensors. Combining nanomaterials with enzymes reduces insulating effects, due to the high-efficient electrical activity from the active site of the enzyme to the electrode. Moreover, the employment of these proteins increases the specificity of the sensor.

Among the variety of processes available to synthesize AgNWs [1,2], polyol process has been selected, because of the simplicity and reliability it offers. The employed method consisted in a silver precursor (AgNO3) reduction in presence of Ethylene glycol as a solvent and polyvynilpyrrolidone, which is a surfactant that facilitates the AgNWs dispersion. The developed biosensor results from the immobilization of tyrosinase (TYR) on the top of the AgNWs deposited by spin coating in a different concentration ratio. FTIR, UV-vis, DRX and AFM have confirmed the proposed structure and cyclic voltammetry has shown the amplification caused by the combination of the nanomaterial and the enzyme in the film denoting their excellent performance, sensitivity and reproducibility. Moreover it has been demonstrated that the concentration of AgNWs employed in the development of the biosensors is crucial in terms of reproducibility, in addition to being excellent electronic mediators.

Figure 1. Voltametric response of ITO-Tyr (red) and ITO-AgNWs-TYR (black) onto ITO surface to 10-4M catechol in phosphate buffer 10-2M.

[1] Xu, L. et al. Anal. Methods 7, 5649-5653 (2015), [2] Kumar-Krishnan, S. et al. RSC Adv. 6, 20102–20108 (2016)

Acknowledgments: Financial support by MINECO and FEDER (RTI2018-097990-B-100 and BES-2016-077825) and the Junta de Castilla y León-FEDER (VA-275P18) is gratefully acknowledged.

Figure 1
Bio-Sourced, Potentially Biodegradable Materials for Fast Response Moisture Sensors
Authors: Gouda Abdelaziz , Reali Manuel , Santato Clara
Published: May 2020

Humidity is a very important physical parameter that plays an imperative role in technology and human activity. Researchers are paying more attention to develop moisture-responsive materials with outstanding characteristics such as high sensitivity, wide humidity detection range, fast response and short recovery times to keep pace with the on-going development in technology. Abundant, bio-sourced and biodegradable organic materials, such as melanin, are needed to enable the development of eco-designed technologies that alleviate the environmental footprint of the electronics sector. Melanin is a ubiquitous biomacromolecule with diverse functions including hydration dependent electrical response [1], photoresponse [2], antioxidant [3] , metal chelation [4], and free radical scavenging [5]. Melanin originates from the oxidative polymerization of (5,6)-dihydroxindole (DHI) and (5,6)-dihydroxindole 2-carboxyl acid (DHICA) building blocks [6]. Natural melanin is expected to contain up to 70% of DHI in molecular ratio [7]. Due to the absence of the carboxyl group in the molecular structure, DHI-melanin features a ordered, conjugated structure thus expected to show better electrical conductivity with respect to DHICA-melanin [5]. Herein, we investigate DHI-melanin and DHI-DHICA melanin thin films (7:3 weight ratio), spin coated and polymerized on technologically relevant and potentially biodegradable substrates, as active layers for fast response moisture sensors.

References

[1] Wünsche J, Deng Y, Kumar P, Di Mauro E, Josberger E, Sayago J, Pezzella A, Soavi F, Cicoira F and Rolandi M 2015 Protonic and electronic transport in hydrated thin films of the pigment eumelanin Chem. Mater.
27 436-42

[2] Mostert A B, Rienecker S B, Noble C, Hanson G R and Meredith P 2018 The photoreactive free radical in eumelanin Science advances
4 eaaq1293

[3] Tu Y-g, Sun Y-z, Tian Y-g, Xie M-y and Chen J 2009 Physicochemical characterisation and antioxidant activity of melanin from the muscles of Taihe Black-bone silky fowl (Gallus gallus domesticus Brisson) Food Chem.
114 1345-50

[4] Hong L and Simon J D 2007 Current understanding of the binding sites, capacity, affinity, and biological significance of metals in melanin. ACS Publications)

[5] Panzella L, Gentile G, D'Errico G, Della Vecchia N F, Errico M E, Napolitano A, Carfagna C and d'Ischia M 2013 Atypical structural and π‐electron features of a melanin polymer that lead to superior free‐radical‐scavenging properties Angew. Chem. Int. Ed.
52 12684-7

[6] Meredith P and Sarna T 2006 The physical and chemical properties of eumelanin Pigment cell research
19 572-94

[7] Pezzella A, d'Ischia M, Napolitano A, Palumbo A and Prota G 1997 An integrated approach to the structure of Sepia melanin. Evidence for a high proportion of degraded 5, 6-dihydroxyindole-2-carboxylic acid units in the pigment backbone Tetrahedron
53 8281-6
(Invited) Organic Semiconductor, Receptor Material and Circuit Design for Organic Electronic Vapor Sensors and Biosensors
Authors: Katz Howard E.
Published: May 2020

We will present our recent results on the design of semiconducting material, dielectric receptor matrices, and stabilizing and amplifying circuit structures for detection of volatile analytes in the atmosphere and proteins in aqueous solution. Besides our natural interest in designing materials that respond more strongly to analytes of interest than to likely interferents, we also emphasize the use of chemical and electronic amplification methods to increase the ratio of the desired responses to the drift (signal/noise ratio). Printable materials, especially polymers, are emphasized for the responsive layers. The use of multiple sensing elements, typically field-effect transistors (FETs), to create patterns of responses increases the selectivity of the information, either by narrowing the classes of compounds providing the responses, distinguishing time-dependent from dose-dependent responses, and/or increasing the ratio of analyte responses to environmental drifts. As a specific example, using pairs of FETs, in series or in parallel, allows device drifts to be substantially canceled while analyte responses are maintained and even reinforced. This strategy has led to significant improvements in the use of polymer-based FETs to detect pollutant gases such as nitrogen dioxide and ammonia. To increase the stability of systems used to detect analytes in solution, we sometimes separate the sensing surface from the output device in an arrangement known as a remote gate. We show that the output device may be an organic-based or a silicon-based transistor, and can respond to electrochemical potential changes at the sensing surface arising from a variety of chemical interactions. This type of configuration was applied to the understanding of vapor sensors and the effect of receptor polarity on the detection of brain injury biomarker proteins. New details about the mechanisms for sensor responses to analytes can be obtained from remote gate configurations, including connection of interfacial voltages and charge densities in responsive polymer semiconductors.
Nitrogen-Doped Carbon Nanotube Fiber for Electrode Fabrication
Authors: Hoque Md Abdul , Alvarez Noe T.
Published: May 2020

Carbon Nanotubes (CNTs) are the emerging materials because of their extraordinary physical and chemical properties. Diverse applications, such as chemical and biochemical sensors, electronic devices, nanocontainer lithium ion batteries, thermally stable materials, and many others have been proposed and tested. The properties of carbon nanotubes depend on their structure, such as diameter, defect density, length, chirality, number of walls, etc. Regrowth of nitrogen-doped carbon nanotubes (N-CNTs) from open end of carbon nanotube fiber is our initial focus to achieve using Chemical Vapor Deposition (CVD) method. Incorporation of Nitrogen into carbon nanotube structure leads to high surface area and high density of defects. N-doped CNTs has excellent performance in oxygen reduction reactions and enhance the energy storage capabilities of Lithium ion batteries. Fe-Al bimetallic nanoparticles synthesized by electrochemical process lead to the N-CNTs growth by CVD which is proved by initial investigation. Fabrication of electrode using N-CNTs fiber is easy because of their high conductivity, large surface area, and strong mechanical strength. The application of the electrode and necessary data will be discussed in final presentation.
Electrochemical Sensing of Arsenic Using Physically Vapor Deposited Au Nanofilm Electrodes: Flow Cell Configuration
Authors: Casuse Tybur Quinton , Garzon Fernando H , Cerrato Jose M
Published: May 2020

There is a current need for an inline arsenic sensing system that can continuously sample aquifer water quality for well drilling and ground water monitoring applications. Concentrations of arsenic oxyanions above 10 μg/L in drinking water are considered dangerous by the World Health Organization [1]. Levels above this in daily consumption can lead to renal toxicity and a condition known as Arsenicosis, which produces lesions on the skin. We are currently developing an Au thin film, As stripping voltammetry flow cell sensing to meet this challenging need. Our findings show that use of gold (Au) nanofilm electrodes physically vapor deposited (PVD) onto porous carbon papers can detect concentrations below 10 μg/L of arsenite, As (III), in water. The nanofilms were characterized by SEM, X-ray diffraction and with X-ray fluorescence with a measured loading of approximately 13 μg of Au per 1 cm2 of carbon paper in each electrode. The PVD method increases the manufacturability of aqueous arsenic sensors because it is facile, scalable, and uses much less Au than screen printing methods. Linear stripping voltammetry (LSV) was used in a three-electrode configuration to create a calibration curve for standard additions of 5, 10, 25, 50 and 75 μg/L As (III). The resulting plot of peak area versus concentration resulted in a linear correlation. The capacitance of PVD deposited Au nano films was significantly less than that of Au nanoparticles on XC72 carbon, produced via solution precipitation methods. The lower capacitance enables the detection of low concentrations of As without the need for the application of more complex pulse voltammetry methods.

References

1. WHO, Arsenic in Drinking Water. 2011, World Health Organization.
Preparing DNA SAM Electrochemical Sensors Using Potential Assisted Deposition Methods. Controlling the Coverage and Local Organization of the DNA in the SAM.
Authors: Bizzotto Dan , Leung Kaylyn , Yu Hua-Zhong
Published: May 2020

Typically, DNA SAMs used for electrochemical based sensing are prepared without controlling the gold electrode potential[1]. Applying a potential during DNA deposition enables control over the coverage and DNA organization[2-4]. These characteristics are determined by the composition of the immobilization buffer, the immersion time, the DNA concentration, the extent of backfilling with a small alkylthiol and whether deposition occurs on a bare or alkythiol coverage gold surface[3-4]. Few studies have explored the influence of the underlying surface crystallography. Here, we show the possibilities of using electrochemical potential control to manipulate the characteristics of the DNA SAM. Moreover, the use of a single crystal gold bead electrode, coupled with the use of a fluorophore tagged DNA and fluorescence microscopy, enables examination of the influence of the underlying surface crystallography on the DNA SAM prepared. Various constant potentials were used as well as using a square-wave potential perturbation during deposition. There are significant differences in the DNA SAM produced under these conditions. In some cases, the DNA coverage was low on the <111> surfaces, higher on more open or atomically rough regions. In other cases, the coverage was higher on the <100> surfaces as compared to the other regions. The use of constant positive or negative potentials (vs SCE) resulted in significant differences in the relative coverages among regions of different atomic arrangements (Fig 1). In addition, a significant difference was observed between immobilization buffers that contain Cl and those that are Cl free. Also, the use of constant or square-wave potential perturbations resulted in significantly different local organizations of DNA in the SAM. Examples of these types of DNA SAM surfaces will be presented with some conclusions on the implications for use on polycrystalline planar gold surfaces.

References:

[1] Xiao, Y.; Lai, R. Y.; Plaxco, K. W. Preparation of Electrode-Immobilized, Redox-Modified Oligonucleotides for Electrochemical DNA and Aptamer-Based Sensing. Nat. Protoc.
2007, 2 (11), 2875–2880.

[2] Jambrec, D.; Kayran, Y. U.; Schuhmann, W. Controlling DNA/Surface Interactions for Potential Pulse‐Assisted Preparation of Multi‐Probe DNA Microarrays. Electroanal.
2019, 410, 3.

[3] Leung, K. K.; Gaxiola, A. D.; Yu, H. Z.; Bizzotto, D. Tailoring the DNA SAM Surface Density on Different Surface Crystallographic Features Using Potential Assisted Thiol Exchange. Electrochim. Acta
2018, 261, 188–197.

[4] Leung, K. K.; Yu, H. Z.; Bizzotto, D. Electrodepositing DNA Self-Assembled Monolayers on Au: Detailing the Influence of Electrical Potential Perturbation and Surface Crystallography. ACS Sens.
2019, 4 (2), 513–520.

Figure 1:

Figure 1
(Invited) Steps Towards a Mechanistic Understanding of Electrocatalytic Phenomena in Solid Oxide Cells
Authors: Fleig Juergen
Published: May 2020

Solid oxide fuel or electrolysis cells are based on electrochemical reactions such as oxygen reduction and evolution, hydrogen oxidation or water splitting and the corresponding cell performance depends crucially on the kinetics of these electrode reactions. High reaction rates at low driving forces (overpotentials) as well as low degradation rates are aimed at. This leads to much interest in reaction mechanisms of the corresponding reactions. In a first step, often the relevant reaction pathway (via triple phase boundaries or via the electrode bulk) is identified and the most resistive region within the predominant pathway is localized (e.g. a certain interface or the electrode bulk). In a next step, it is desirable to obtain an atomistic understanding of the resistive or electrocatalytic processes. Here, exact surface species or point defects and phenomena such as dissociation or ionization come into play, and despite strong research activities many questions remained unsolved so far.

This talk presents our recent progress on this topic: Established electrochemical approaches (e.g. Butler-Volmer equation) do no longer hold for describing such reactions and a novel model was thus developed, which allows a proper interpretation of p(O2) dependences and current-voltage curves. It is discussed, how composite electrodes can improve the reaction rate by a kind of “job sharing”. Exsolution-based composites are considered at the fuel side (Fe on LSF) and it is discussed, what happens during electrochemical switching of their electrocatalytic activity by an overpotential. Moreover, it is illustrated how nano-particles of Pt on (La,Sr)FeO3 (LSF) thin film electrodes strongly improve the reaction rate and also completely change the reaction mechanism (see figure) and the p(O2) dependence. Finally, the topic of active sites and electrode degradation is considered, with special emphasis on (La,Sr)CoO3 (LSC) and LSF. Extraordinarily high oxygen reduction activity of pristine films is shown, different reasons for degradation are discussed, and surprising defect chemical phenomena are displayed for oxygen evolution from LSC thin films.

Figure 1
(Invited) Elevated Temperature Electrosynthesis of Fuels and Chemicals Using Carbon Dioxide and Nitrogen through Protonic Ceramic Electrochemical Cells (PCECs)
Authors: Ding Dong , Hua Bin , Li Meng
Published: May 2020

Currently, the main feedstock in chemical and energy industry still comes from nonrenewable petroleum that is being depleted rapidly for fuel and chemical synthesis, leading to significant energy consumption and carbon emissions. To address rising environmental concerns and energy challenges, it is highly desirable to develop green chemical synthesis technologies for a sustainable future. Elevated temperature electrosynthesis through solid oxide cells is a promising strategy because of the following advatanges: (1) it can control the product selectivity by changing the operating potentials and temperatures, (2) it can be operated at ambient pressure, (3) it has high production rate and low overpotential, and (4) it can be easily integrated with other renewable power sources. Despite of these promising features, this technology still faces many challenges. One of the major issues is the relatively low catalyst activity as well as insufficient catalyst stability and durability. Therefore, the development of active and stable electrocatalysts is the key to make high temperature electrosynthesis efficient and practical for industrial scale applications. At Idaho National Laboratory, we have made significant achievements on electrosynthesis for ammonia production and CO2 hydrogenation using protonic ceramic membrane reactors. The outcomes of these researches have the potential to contribute to the US DOE’s goals of growing the energy economy, improving energy efficiency, and innovating clean energy sources.