bluuebunny/crossref_metadata_2025 huggingface dataset:
The Selective Coupling and Quantification of Peptides on a Polymer-Coated Microelectrode Array
Authors: Graaf Matthew D. , Moeller Kevin D
Published: February 2020

Microelectrode arrays have been utilized by our group for several years to monitor the binding event of a biological system in “real-time”.1 The use of a diblock co-polymer coating over the electrode surface as a support structure for the molecules of interest has been crucial to the success of these experiments.2 In order to better understand the orientation of these molecules on the surface and their influence on binding to a target receptor, selective coupling and characterization of the molecule is needed. Here in we report the ability to couple peptides directly to the polymer surface with high selectivity and in some cases, without the use of protecting group strategies. Further, we can utilize this technique to quantify the amount of peptide on the array to optimize binding studies.

1Fellet, M. S.; Bartels, J. L.; Bi, B.; Moeller, K. D. J. Am. Chem. Soc. 2012 , 134, 16891

2Hu, L.; Graaf, M. D.; Moeller, K. D. J. Electrochem. Soc. 2013 , 160 (7) G3020-G3029

Figure 1
Electrochemical Explorations of 9,10-Anthraquinone/Hafnium(IV) Ion Interactions in Nonaqueous Solvents
Authors: Cheek Graham T.
Published: February 2020

Introduction

       The well-defined electrochemical behavior of quinones such as  9,10-anthraquinone (AQ) in nonaqueous solvents (1,2) suggests its use as a probe for interactions of metal cations with the AQ carbonyl oxygens.  In previous work from this laboratory, the interaction of AQ with added Al(III) trifluoromethanesulfonate [Al(TfO)3] in adiponitrile has been shown to produce a shift in the initial AQ reduction process to more positive potentials (3).  In contrast to the behavior seen for 9-fluorenone (4), however, the second AQ reduction process disappears even at the 0.4 : 1.0 Al3+ : AQ point.  This observation suggests that AQ reduction products are good ligands for the Al3+ cation, with approximately three reduced AQ ligands coordinated to one Al3+.  The present work explores whether this effect extends to other metals, particularly Hf4+.  The general effect of Hf4+ on the cyclic voltammetry of AQ in adiponitrile is also treated.

Experimental

       Adiponitrile (AN) and 9,10-anthraquinone (AQ) were obtained from Aldrich Chemical Co. Hafnium trifluoromethansulfonate [hafnium triflate, Hf(TfO)4] was obtained from Alfa-Aesar.  Tetraethylammonium tetrafluoroborate [TEA BF4] was purchased from Southwestern Analytical Chemicals (SACHEM). Voltammograms were acquired with a PAR283 potentiostat using PowerSuiteTM  software. Potentials are reported with respect to a Ag/AgCl (0.1M EMICl in EMI BF4) reference electrode (Cypress Systems).  Vitreous carbon electrodes were obtained from Cypress Systems.  All experiments were carried out in a Vacuum Atmospheres drybox.

Results and Discussion

      A cyclic voltammogram of AQ in adiponitrile without added Hf(TfO)4 is shown in Figure 1a, which shows the usual two uncomplicated successive one-electron transfers.  Upon addition of Hf(TfO)4 at the 0.4 : 1.0 Hf4+ : AQ level, however, a substantial positive potential shift is observed for AQ reduction (Figure 1b). This shift is due to complexation of one of the AQ carbonyl oxygens by Hf4+.  As in the case of Al3+ addition, there is none of the original second AQ redox process at this point.  This observation implies that Hf4+ is complexed by multiple AQ reduction products, as was also seen for Al3+ addition.  Further additions of Hf(TfO)4 give only the shifted reduction process at the 1:1 Hf4+ : AQ point, with substantially more of the small reduction peak at +0.1 V in Figure 1b.  The latter observation suggests the possibility that both AQ carbonyl oxygens can undergo complexation by Hf4+ in this system.  The present results indicate extensive interaction of Hf4+ with AQ, including the role of reduced AQ species as multiple ligands for Hf4+.

References

N. A. Macıas-Ruvalcaba and D. H. Evans, J. Phys. Chem. C,
114
, 1285 (2010).

L.  Jeftic and G. Manning,  J. Electroanal. Interfacial Echem, 26, 195 (1970).

Electrochemical Society 226th Meeting, Fall 2014, Cancum, Mexico, ECS Abstract H1-1345.

D. Canby, E. Sanders,and G. T. Cheek, J. Electrochem. Soc., 160(7), G3159 (2013).

Figure 1
Second Generation Aqueous Electrolyte Electrochemical Cells for Scaled Stationary Energy Storage
Authors: Whitacre Jay
Published: February 2020

The design and function of next generation aqueous electrolyte dual-intercalation energy storage devices and systems will be discussed.  These system use relatively unexplored electrode interactions that exploit muti-cation reactions (eg lithium, sodium and proton interactions all can contribute to the energy storage function). The core device uses a configuration wherein the active anode material consists of a blend of carbon-coated NaTi2(PO4)3 and activated carbon and the cathode is cubic spinel l-MnO2 that has resident lithium.  The electrolyte is a blend of Li+ and Na+ and hydrogen (at some states of charge) cation species, with SO4
- and OH- (at some states of charge) as the countering anions, solvated in an initially neutral pH aqueous electrolyte. 

Improvements to the original large-format devices first disclosed in 2011 will be disclosed, and data will be presented showing that large scale industrially packaged batteries with over 3000 Wh in capacity have be produced and qualified.  Data showing the relationship between electrode thickness, current collector resistance, and overall battery performance will be shown. Systems containing packs of these batteries in the multi-kWh range have been effectively implemented in field-testing around the world.  These applications include support for both smaller off-grid applications with bus voltages in the in the 20 to 100 V range, as well as, grid compatible systems with bus voltages in excess of 1000 V.
The Electrochemical Properties of Diamond and Tetrahedral Amorphous Carbon Electrodes in Room Temperature Ionic Liquids
Authors: Swain Greg M , Jarosova Romana , Munson Catherine
Published: February 2020

Room temperature ionic liquids (RTILs) are emerging as a new medium for redox reactions as these liquids possess high solubilizing  power, electrical conductivity, wide breakdown voltage and low volatility. Being composed entirely of ions (no solvent) and possessing wide electrochemical windows (
ca.
5 V), it is not difficult to see why these liquids are viewed by electrochemists to be attractive electrolytes for investigation. Our group is (i) studying the wetting of these ionic fluids on different carbon electrode surfaces and how this wetting affects the capacitance-potential relationships and (ii) investigating how the carbon electrode surface chemistry and microstructure affect the heterogeneous electron-transfer rate constant of different inorganic and organic redox systems in these ionic liquids. It is well established that the in aqueous electrolyte solutions, the heterogeneous electron-transfer rate constant for certain redox-systems at ordered HOPG and more microstructurally-disordered glassy carbon is strongly affected  by the electrode surface microstructure and chemistry. We seek to learn if these same trends hold in ionic liquids.

In this presentation, we will compare the electrochemical behavior of boron-doped nanocrystalline diamond and nitrogen-incorporated tetrahedral amorphous carbon thin-film electrodes. Specifically, contact angle measurements of the surface wettability, measurements of the double-layer capacitance (C
dl) and its variation with potential, and heterogeneous electron-transfer rate constants for redox systems in structurally distinct RTILs will be presented. These two carbon electrodes have distinct microstructures as compared to their sp2 carbon counterparts. Nitrogen-incorporated tetrahedral amorphous carbon (ta-C:N) is a composite material consisting of a mixture of sp2 and sp3-bonded carbon. Impurities can be incorporated during growth (e.g., N) further adding to their complex structure. These films typically possess 40-60% sp3-bonded carbon. It has been widely used as a protective coating due to its hardness, high wear resistance and low coefficient of friction. The growth temperature for ta-C is usually from 25 to about 100 °C. This means that non-traditional materials, such as plastics, can be used as substrates for deposition. Importantly, these carbon materials possess some electrochemical properties that are similar to those of diamond.
Transparent Solid Polymer Electrolyte Thin Film Via Layer-By-Layer Deposition for Electrochromic Devices
Authors: Cui Mengqi , Lee Pooi See
Published: February 2020

Polymer solid-state ionic conducting materials are of high interests because of their great applied potential in flexible and wearable devices. Layer-by-Layer (LbL) deposition is a facile method to fabricate thin film with precise control of structures and functionalities. In this work, a new solid polymer thin film constructed by layer-by-layer deposition as Li+ ion conductor is presented. Unlike traditional polymeric LbL films, which usually involve two individual polymers as components, here we demonstrate a novel strategy for LbL assembly method by using poly(ethylene oxide) (PEO)-poly(acrylic acid) (PAA) and PAA-PEO complexes as building blocks. Compared with non-complexing polymers, polymeric complexes possess unique steric structures and interfacial behaviors, providing more possibilities to modulate the final structure and properties of the LbL film. We studied a series of LbL films-- PAA/PEO, PAA-PEO/PEO, PEO-PAA/PAA and PEO-PAA/PAA-PEO, investigating the growth kinetics and ionic conduction of those films. We found out that the polymeric complexes not only contributed to a fast growing behavior of LbL films, but also led to an improved ionic conductivity. We further present the use of PEO-PAA/PAA-PEO multilayers as solid electrolyte for a working electrochromic device.
Electrochromic Properties of Non-Stoichiometric Ni1-Xo Thin Films
Authors: Da Rocha Mathias , Manceriu Laura , Rougier Aline
Published: February 2020

NiO is a well known anodic electrochromic (EC) material showing optical modulation under electrochemical oxidation and reduction [1]. Despite the simplicity of this oxide, electrochromism in NiO thin films is rather complicated although it is generally accepted that the optical modulation is related to a charge-transfer process between Ni(II) and Ni(III). The NiO is commonly associated to WO3 in inorganic EC devices, a combination leading to a neutral color due to the simultaneous brownish and blue color of NiO in oxidized state and WO3 reduced state, respectively. Nevertheless, their association is complicated owing to their different stabilities in acidic/basic media, a factor which also impinges on the device stability. In our group, an unusual reactivity for non-stoichiometric Ni1-xO thin films cycled in various electrolytes was recently reported opening the choice of materials for complete devices working in both lithium and lithium free electrolyte [2].

      Ni1-xO thin films were grown at room temperature by sputtering deposition on ITO-glass substrate. The influence of various partial pressures of O2 (a 4 Pa total pressure was maintained during deposition) on the stoichiometry, morphology and cristallinity of Ni1-xO thin films was studied and correlated to their EC behavior. Unsurprisingly, an increase in oxygen partial pressure is related to a stronger brownish appearance associated with to an increase in the Ni3+ amount as well as a decrease in film porosity and roughness. Moreover, the comparison of the electrochemical properties of Ni1-xO films cycled in aqueous (KOH), lithium based and lithium free ionic liquid electrolytes, shows an evolution from a faradic to a pseudo-capacitive behavior, while optical contrast from colorless to brownish remains in all cases. This suggests that electrochromism is not only the result of of small cations (de)insertion but also depends on surface phenomena including possible participation of anions.

      Herein, the relationship between the physical-chemical properties and EC performances of non-stoichiometry Ni1-xO thin films will be investigated. Finally, the combination of Ni1-xO with WO3 and PEDOT in full devices will be discussed.

[1] C.G. Granqvist, Handbook of inorganic electrochromic materials, Elsevier, Amsterdam, Netherlands, 1995

[2]  Moulki, H., Faure, C., Mihelčič, M., Vuk, A.S., Švegl, F., Orel, B., Campet, G., Rougier, A. Electrochromic performances of non-stoichiometric NiO thin films, Thin Solid Films, 2014, 553, 63-66.
Enhanced Electrochromic Switching and Electrochemical Stability of Conducting Polymer on the Ionic Liquid Functionalized ITO Electrode
Authors: Ouyang Mi , Yang Yuan
Published: February 2020

Conducting polymers (CPs) based electrochromic materials have drawn wide interests owing to multicolor display property, high coloration efficiency, good processibility and high optical contrast. However, the relatively slow response speed and poor long-term stability have severely limited their applications. Therefore, to improve the response speed and long-term stability via various methodsis is one of the key to expand the practical applications of the CPs-based electrochromic devices. Ionic liquids are good for electrochemical synthesis and applications as a promising medium due to their wide electrochemical windows, good electrical conductivity and solvent transport properties.1-2 Therefore, ionic liquids has been introduced to improve the EC performance of conducting polymers. In this paper,  conducting polymer poly(4,4',4"-tris[4-(2-bithienyl) phenyl]amine) (PTBTPA) incorporated with 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) was successfully prepared via electrochemical polymerization on the [BMIM]BF4 functionalized ITO substrate. The PTBTPA–[BMIM]BF4 film presents reversible multicolor changes from orange, olive green to dark gray. The electrochromic measurement exhibits the switching speed of conducting polymer is significantly enhanced by incorporating with ionic liquid than that of the pure PTBTPA film. Electrochemical impedance spectra demonstrates the PTBTPA–[BMIM]BF4 film possesses much lower charge transfer resistance and faster charge transfer speed. In addition, the PTBTPA–[BMIM]BF4 film presents better electrochemical stability in the ionic liquid.

Figure 1
Novel Self-Powered Electrochromic Materials and Devices
Authors: Xu Chunye
Published: February 2020

Self-powered electrochromic device is a kind of instrument that can change transmittance with the electricity converting from solar energy. A novel derivative of triphenylamine, (4-((4-(dimethylamino)phenyl)(phenyl)amino)benzyl) phosphoric acid (TPAPA), with both photovoltaic and electrochromic functions, is designed and synthesized in this work. Working electrode was made by dissolving the compound in chloroform and then coating the solution on titanium dioxide-coated fluorine-doped tin oxide glass. The working electrode shows light yellow at -1.5 V and dark green at +2.5 V. The maximum transmittance contrast between the two states is 64.2% at 629 nm. Meanwhile, the photovoltic properties of TPAPA-based electrochromic devices were measured with a solar simulator under 1-sun illumination. Energy conversion efficiency of 0.32% was obtained, with short-circuit current density of 1.32 mA/cm2, open-circuit voltage of 0.44 V and fill factor of 0.54. Our results suggest that the compound has dual functions of electrochromism and photovoltaics. Compared with conventional photoelectrochromic devices with both photovoltaic and electrochromic electrodes, the dual functional TPAPA-based device provides much simple strcuture, and thus may have potential application in buildings, vehicles and displays.
Self-Terminated Electrodeposition of Monolayer Electrocatalysts
Authors: Ahn Sang Hyun , Liu Yihua , Wang Rongyue , Bertocci Ugo , Moffat Thomas
Published: February 2020

In a recent publication Pt deposition at negative potentials revealed an unanticipated self-terminating characteristic that enables controlled deposition of Pt monolayer films from a K2PtCl4-NaCl electrolyte. Herein we explore the generality of such reactions by examining a variety of other transition metal systems. In the case of Pt, the deposition reaction is quenched at potentials just negative of proton reduction by alteration of the double layer structure and adsorption properties induced by a saturated surface coverage of underpotential deposited hydrogen, (Hupd). The surface may be reactivated for Pt deposition by stepping the potential to more positive values where Hupd is oxidized and fresh sites for adsorption of PtCl4
2- become available. Periodic pulsing of the potential enables sequential deposition of additional Pt layers to fabricate films of desired thickness relevant to a range of advanced technologies in manner that is tantamount to wet atomic layer deposition (ALD).  This talk will present an update on the exploration and use of self-terminating electrodeposition reactions to form electrocatalysts for use in water electrolysis and related reactions.
Modeling/Simulation and Prototyping Development of Solar-Hydrogen Generators
Authors: Xiang Chengxiang , Chen Yikai , Walczak Karl , Singh Meenesh , Weber Adam Z , Jin Jian , Lewis Nathan S.
Published: February 2020

A solar-driven water-splitting cell is generally comprised of light absorbers, electrocatalyts, membrane separators and an electrolyte solution in a specific system geometry.  The overall solar-to-hydrogen conversion efficiency of such a system depends on the performance and materials properties of all the individual components as well as the design of the system.  Significant advancements in modeling/simulation and prototyping development of solar-hydrogen devices have been made at Joint Center for Artificial Photosynthesis (JCAP).  In this talk, I will present a comprehensive multi-physics model for a solar-hydrogen cell that accounts for the performance of photoabsorbers and electrocatalyts and the transport properties of electrolytes and membrane separators.  The whole cell model was employed to optimize geometries of prototype designs, to define operational conditions and constraints for various system designs, to provide target materials properties and to evaluate the viability of new design concepts.  Specifically, the optimal band-gap combination of a tandem photoabsorbers, the performance limits in near-neutral pH electrolytes and the target transport properties of the membrane separators will be discussed in detail.  A few novel cell designs, including a vapor feed device and a solar concentrator coupled solar-hydrogen cell will also be discussed.  In the past years, guided by the modeling and simulation activity, a robust prototype, the louvered design, has been developed.  A solar-to-hydrogen conversion efficiency that exceeds 10% has been achieved in an integrated device with product gas separations.
Electrochemical Detection of Four Prominent Tuberculosis Biomarkers Using Functionalized Titania Nanotubular Array Sensing Platform
Authors: Bhattacharyya Dhiman , Smith York R. , Mohanty Swomitra K. , Misra Mano
Published: February 2020

Current available state-of-art tuberculosis (TB) detection techniques face four challenges: cost, time of detection, equipment portability, and performance. For rapid, point-of-care (POC) detection, sensing of volatile organic compounds (VOCs) from the breath is important for early diagnosis of several pulmonary diseases such as TB. VOCs such as methyl nicotinate, methyl p-anisate, methyl phenylacetate, and o-phenylanisole have been identified as prominent TB breath biomarkers. Sensing of VOCs using solid-state TiO2 nanotube array sensors is a robust method to detect VOC vapors.

Highly ordered titania nanotubular arrays (TNA) were synthesized through electrochemical anodization and functionalized with cobalt. Passing nitrogen gas through an ethanol biomarker solution was used to deliver the vapor of the individual biomarkers to the sensor. Detection of biomarkers was carried out in amperometric mode at optimized bias potentials determined from cyclic voltammetry studies. The sensor response towards the biomarkers was calculated by subtracting the base current (only N2/ethanol) from the peak current obtained (N2/ethanol + biomarker). Varying the concentration of the biomarker in solution was used to determine the sensitivity of the sensors. Further, the sensitivity was also examined through electrochemical sensing of all the four biomarkers mixed in solution. The selectivity of the sensor was investigated by operating the sensor at different potentials when exposed to the mixture of biomarker vapors.

The results illustrate that titania nanotubular morphology and cobalt are necessary for volatile organic biomarker (VOB) detection. Also, the sensor exhibits good sensitivity and selectivity towards the four prominent TB biomarkers. Further, mechanisms have been proposed to describe the attachment of the biomarkers to Co-TNA and are supported by XPS characterization and band theory.
Facile Synthesis of High-Porous Noble-Metal-Free Catalyst for Highly Efficient Oxygen Reduction Reaction
Authors: Whang Dongmok , Kim Mansu
Published: February 2020

High-porous noble-metal-free catalyst is great alternative for oxygen reduction reaction (ORR) in fuel cells. But, there are some challenges in further performance and stability and understanding of reaction mechanisms on electro-catalyst. Herein, we design a facile method to synthesis high-porous noble-metal-free material from metal-organic framework through only one pathway. After significant pyrolysis process of metal−metalloporphyrin framework (MMPF-6), resultant product could potentially play a very important role for highly efficient oxygen reduction reaction in both alkaline and acidic mediums. Carbonized MMPF-6 shows highest ORR activity with onset and half-wave potentials of 976 and 848 mV in 0.1 M KOH, respectively, which are similar activity to those of commercial Pt/C (half-wave potential 860 mV vs RHE). Moreover, carbonized MMPF-6 has much greater long-term stability under alkaline and acidic mediums than commercial Pt/C. We suggest that the carbonized MMPF-6 catalyst has an electrochemical active surface area due to ensemble effect between zirconium oxide cluster and iron as active site. Electrochemical analysis shows that the carbonized MMPF-6 catalyst in 0.1 M KOH and HClO4 follows the efficient four-electron-tranfer pathway.
Self-Propelled Nanorockets for Water Monitoring and Pollutants Purification
Authors: Li Tianlong , Li Longqiu , Wang Lin , Zhang Guangyu
Published: February 2020

Self-propelled catalytic microrockets, capable of converting energy into movement and forces, have shown considerable promise for addressing environmental problems. It can be widely used in environmental areas that would benefit from these developments, including protecting the water resource and ensure widespread access to clean and affordable water.In this work, a self-propelled polymer-based microrocket, which is proposed to monitor the water quality and remove organic and inorganic pollutants, is fabricated and investigated. The effects of electropolymerized outer layers and the concentration of the microrocket, upon the removal of pollutants are evaluated. Furthermore, the adsorption kinetics and adsorption isotherms are also studied. As we found, polymer-based microrocket provides a highly efficient way to remove pollution particles and purify water due to the motion of microrocket.
Electrochemical Characterisation of a Real-Time pH Sensor
Authors: Herdman Karen M. , Bolger Fiachra B. , Finnerty Niall J. , Breslin Carmel B.
Published: February 2020

Real-time monitoring of pH levels is important for many reasons.  Abnormal tissue pH is an indicator of altered cellular metabolism in illnesses such as stroke and cancer.  Tumour pH, for example, is more acidic than that of normal tissue in both animals and humans due to elevated levels of anaerobic and aerobic glycolysis in tumours1.  In the brain, the release of neurotransmitters result in a series of metabolic processes causing an influx of various ions that result in pH changes in the surrounding matrix2. Transient local pH changes in the brain are important markers of neuronal activity that can be used to follow metabolic processes which underlie the biological basis of behaviour, learning and memory3.

In this study a carbon paste electrode (CPE) was modified with a quinone containing diazonium salt by electrochemical deposition.  Various deposition conditions were employed to give the optimum and most efficient method.  Shown in Figure 1 is a SEM micrograph of a modified CPE alongside the mechanism for the electrodeposition of the diazonium salt onto the electrode.

Figure 2 shows a bare CPE cycled in a PBS solution compared to a modified CPE cycled in the same solution.  This indicates that the diazonium salt was successfully deposited onto the electrode surface.  Potentiometric pH responses of the modified electrodes showed a response slope of −60.36 ± 0.89 mV/pH, n = 23, as shown in Figure 3.  The electrode stability was tested for a period of up to 28 days.  Modified electrodes were also subjected to treatment with physiologically relevant proteins and lipids to investigate any implications for real-time monitoring of brain pH.

References:

J. Wike-Hooley, A. van den Berg, J. van der Zee and H. Reinhold, European Journal of Cancer and Clinical Oncology, 1985, 7, 785-787.

M. Makos, Y.Kim, K. Han, M. Heien and A. Ewing , Analytical Chemistry, 2009, 81, 1848–1854.

P. Takmakov, M. Zachek, R. Keithley, E. Bucher, G. McCarthy and R. Wightman, Analytical Chemistry, 2010, 82, 9892–9900.

Figure 1
(Keynote) Progress in the Development of Metal Oxide Gas Sensors to Reduce Carbon Footprint
Authors: Thangadurai Venkataraman , Mulmi Suresh
Published: February 2020

A chemical gas sensor is a device that transfers chemical information (receptor) of a specific sample component or total composition into an analytically useful signal (transducer). Based upon the transducer operating principle, the signals could be the results of optical, electrochemical, mass, calorimetric and/or magnetic properties. The challenge to fix the current issues on cost, sensitivity, selectivity and reliability of a gas sensor, metal oxide based electrochemical gas sensors are much emphasized for the development of suitable sensor materials. As such, electrochemical gas sensors are mainly categorized into potentiometric, amperometric and resistive-type depending upon the analytical electrical signals; V, I and R, respectively.

The real-time detection of gas composition is essential for improving efficiency in industrial process and to lower the greenhouse gas (GHG) emissions. CO2, one of the major components of GHGs, encounters a challenge on being monitored at real-time under harsh environmental conditions. Spectroscopic and optical techniques based on infrared radiation are commonly used to detect CO2 at room temperature, however, the in situ monitoring of the gas species by placing such sensors directly at high temperature and aggressive environment is practically incompatible due to their size and stability issues. Na+ and Li+ ion conducting electrolytes (e.g., Na-β-alumina, NASICON-type), and Na2CO3 and BaCO3 electrodes have been widely employed to fabricate all-solid-state EMF CO2 sensor.  On the other hand, SnO2, TiO2 and WO3 as semiconductor-based sensors were also used as resistive-type CO2 sensors. In both cases, the stability and cross sensitivities, however, have remained as major obstacles. Our approach was, therefore, to use perovskite oxides (POs) in semiconductor-based gas sensors, for their high thermal and chemical stability, which in turn improve sensor's reliability and long-term performance. In addition, the doping flexibility in POs allowed us to prepare transition metal-doped perovskites. The critical role of dopant on CO2 sensing properties is discussed. The future prospect of using nanotech with its ability to precisely control the structure of these materials may guide CO2 sensors into a whole new level.
Comparison of Magnetoelastic Sensors to Other Acoustic Wave Sensors
Authors: Wikle Howard Clyde , Hu JiaJia , Horikawa Shin , Chai Yating , Chin Bryan A
Published: February 2020

Acoustic wave (AW) sensors have been widely investigated for use as gravimetric devices to weigh extremely small masses and for surface science studies. By measuring the frequency shift and/or the motion of the sensor, the change in mass, due to adsorption of chemical or biological species on the surface of the sensor, can be determined. The mass resolution for some AW sensors have been demonstrated to extend to the yoctogram (1 yg = 10-24 g) range, the mass of a single proton. Here we compare the operation and performance of the magnetoelastic (ME) acoustic wave sensor to other AW sensor platforms. For the ME sensor, longitudinal vibrations are actuated by an oscillating external magnetic field which induces magnetostrictive strain within the material. The use of the ME sensor platform as a biosensor for the detection of foodborne pathogens is discussed.
Temperature-Controlled Electrochemical Microsensors and Microsensor Arrays
Authors: Contento Nicholas M. , Semancik Steve
Published: February 2020

There is a growing demand for rapid, simple, and low-cost chemical sensors for next generation bio-manufacturing, medical diagnostics and environmental monitoring. Current reliable technologies like mass spectrometry and fluorescence-based assays suffer from low throughput and relatively high cost. A preferred alternative method would use electrochemical techniques, which can be adapted for automated screening of multiple chemical/biochemical targets. Unfortunately, due to the complexity of real-world samples, which can contain multiple interfering species spanning several orders of magnitude in concentration, the broad range of electrochemical sensing strategies found in the literature have produced only limited commercial technologies. Actively controlling an electrode’s surface temperature, which is simultaneously one of the most critical and most neglected parameters in determining sensor response, offers a route towards improved electrochemical detection for real-world samples. Previous work has demonstrated certain advantages of both directly and indirectly heated electrodes in terms of sensitivity and selectivity[1,2].

In this work we present the design concepts, fabrication methods, and temperature characterization approaches for microfabricated, temperature-controlled electrodes. The use of modern microfabrication techniques provides several advantages by facilitating the construction of sensors with highly reproducible heating/electrochemical characteristics, the production of high spatial-density sensor arrays, and the compatibility of sensors with complementary microfluidic/MEMS components for sensing in ultra-small sample volumes. The sequential deposition of patterned metallic structures and insulating layers (e.g. SiO2) was used to fabricate Au disk electrodes (r ≤ 75 μm) with underlying platinum resistive heating elements as shown in Figure 1A. The small vertical electrode-heater separation (≲ 500 nm) allows for rapid and efficient heating of the electrode surface. Infrared and fluorescent temperature imaging techniques are used to evaluate temperature gradients and thermal response times, which impact sensor performance. We demonstrate temperature-dependent electrochemical measurements performed on model systems (e.g. Fe(CN)6
3-/4- and Ru(NH3)6
3+/2+) in which coupled heat and mass transport impart signal enhancement as shown in the cyclic voltammograms in Figure 1B. We also discuss the impact of various temperature control routines, such as temperature steps, pulses and oscillations, on electrochemical signal content.

References

(1)      Gründler, P. Fresenius. J. Anal. Chem.
2000, 367, 324–328.

(2)      Flechsig, G.-U.; Walter, A. Electroanalysis
2012, 24, 23–31.

Figure 1
First Principles Molecular Dynamics of Ionic Transport in High-Temperature Molten-Salt Electrolytes
Authors: Cheng Yi-Chia , Li Hao-Yu , Chen Chung-Fu , Hong Che-Wun
Published: February 2020

Introduction

The main purpose of this study is to simulate the ionic transport  in the electrolytes of high-temperature molten-salt batteries using first-principles molecular dynamics techniques. Figures 1 and 2 show the configuration of a thermal battery in which what we concentrate on is the electrolyte. Figure 3 displays its overall chemical reaction to generate electricity. Our fundamental technique is based on the Hellmann-Feynman theorem which integrates the molecular dynamics (MD) simulation with the Density Functional Theory. Then we compare simulation results with experiments from leteratures to verify the pros and cons of different methods. First principles MD simulation technique is a powerful tool for evaluating ionic conductivity and to understand the interactions between each ion. 

Results and Discussion

Figure 4 shows the molecular simulation model of the LiCl-KCl electrolyte. Its radial distribution function (RDF) is shown in Figure 5, which implies a stable molten structure and the phenomenon of ionic distributions. Figure 6 shows the mean square displacement (MSD) in different runs of the same case. It indicates that run-1 did not reach convergence. With continuous run-2 and run-3, a good converged mean square displacement is displayed. The ionic conductivity is related to the diffusion coefficient and is calculated by the Nernst-Einstein relation. The simulation results compared with experimental data are shown in Figure 7.  Furthermore, Figure 8 shows the melting point prediction by cooling down the molten-salt electrolytes; the temperature at the discontinuous of the potential energy jump is recognized to be the melting point of electrolyte. 

Conclusion

First-principles molecular dynamics simulation technique is an ab initio technique to simulate the ionic interaction from the very beginning without inputting a semi-empirical potential model. It is expected to build up a more complete software tool for designing the molten salt electrolytes to replace the costive  trial-and-error experiments and to optimize the battery design in a more efficient way.

Figure 1
Theoretical Approach to the CH4 Decomposition on BaTiO3(001)
Authors: Rivera Rocabado David Samuel , Ishimoto Takayoshi , Koyama Michihisa
Published: February 2020

Oxide configurations with perovskite structures exhibit some interesting and controllable properties. BaTiO3 compounds have attracted considerable attention due to their potential use as electric and optical applications (1). Additionally, BaTiO3 has been studied for its catalytic properties in the oxidative coupling of methane (2), partial oxidation of methane (3) and for the total oxidation of methane (4) showing some promising results. Moreover, the presence of BaTiO3 on the anode material showed to suppress the C deposition for the low temperature dry methane reforming (5). In a similar way, BaTiO3 has been used as anode for solid oxide fuel cells (SOFCs) exhibiting quite low performance when methane was employed as fuel, but its performance increased in the presence of sulfur containing fuel (6). Although, this material showed some curious properties when used partially or totally as anode for SOFCs to date there are only speculations regarding its potential. In several occasions theoretical studies have been used to elucidate the phenomena behind some exciting properties such as catalytic behaviour. However, this is not any easy task since heterogeneous catalytic processes are complex to model due to the absence of information on the molecule-surface interaction, and the effect that the operating conditions and catalyst preparation have on its performance. In this work an idealized model will be used to describe the methane decomposition on the surfaces of BaTiO3(001) employing density functional theory (DFT) method. Preliminary results show that the TiO2-terminated surface is approximately four times more active for the total decomposition of methane than the BaO-terminated surface.

References

S. Saha, T. P. Sinha, and A. Mookerjee, Phy. Rev. B, 62, 8828, (2001).

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C. Guo, J. Zhang, W. Li, P. Zhang, and Y. Wang, Cat. Today, 98, 583, (2004).

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X. Li, Q. Hu, Y. Yang, Y. Wang, and F. He, Appl. Catal. A: General, 413– 414, 163, (2012).

J. H. Li, X. Z. Fu, J. L. Luo, K. T. Chuang and A. R. Sanger, J. Power Sources, 213, 69 (2012).
Acetylacetonate Complexes for Non-Aqueous Redox Flow Battery Applications
Authors: Kucharyson Jonathan F. , Suttil James A. , Escalante-Garcia Ismailia L. , Thompson Levi T
Published: February 2020

An ester functionalized vanadium acetylacetonate (acac) complex was synthesized and characterized for use in redox flow batteries (RFBs). The resulting complex has a solubility of 1.32M, a significant improvement over other metal complexes that have been considered for non-aqueous RFB applications, and a theoretical energy density of 37 Wh/L. While short term flow cell cycling of the complex shows high coulombic efficiencies (95%), capacity fade limits long term cycling. To better understand the causes of capacity fade, a stability study utilizing bulk electrolysis was conducted on both the parent vanadium acetylacetonate, and the ester functionalized complex. The results were used to determine the shelf life, solubility at each oxidation state, and cycle life for each half reaction. The shelf life is greater than the cycling experiment timelines and should not result in a loss of capacity. The solubilities at each oxidation state do not change by more than 25% of the solubility of the parent species. Vanadyl formation is evident during oxidation, and ligand detachment occurrs during reduction. The cycle life for the vanadium acetylacetonate is limited by vanadyl formation and reaches 80% capacity within ten cycles. The ester functionalized system shows rapid vanadyl formation and reaches 80% capacity after just the first cycle. Work is ongoing to better characterize side products and better understand the mechanism of the reactions.
In Situ Oxygen Gradient Generation, Control and Model inside a Microfluidic Habitat
Authors: Mustain William E , Liu Ying , Kadilak Andrea , Shor Leslie
Published: February 2020

Microfluidic devices can be used to simulate complex microhabitats where the concentration gradients of oxygen, nutrients, or other chemical stimulants need to be dynamically controlled.  Though oxygen gradients can be achieved by flowing an oxygenated fluid through a microchannel and allowing the oxygen to diffuse through a polymer membrane/hydrogel to the cell culture area, this configuration does not allow the precise control either spatially or temporally [1]. 

The diverse microbial community of the termite gut is an example of a naturally occurring microhabitat that experiences steep oxygen gradients [2]. These oxygen gradients are really necessary for the formation of spatially-distinct microniches for the protists, bacteria, and archea inhabiting the gut, while the microniches allow microbial symbionts to co-exist with each other and the termite host while breaking down various carbon sources into useful products such as acetate.

In this presentation, we will detail a new method to generate, control, and model the oxygen gradients within a microfluidic habitat.  A novel microfabrication method was developed to photopattern gold electrodes on the vertical side walls of the microchannels for oxygen generation, as shown in Figure 1 [3]. Finite element simulations were conducted to model oxygen production rates under varied geometries, operating currents, and flow rates.  Additionally, in-plane hydrogel barriers were constructed between the channels containing the electrodes and the cell culture chambers, to maintain the stable oxygen gradient and also dampen any sudden changes to the system that could harm cells. With these recent advances in microfabrication and modeling techniques, the micro-scale physical and chemical features of a termite gut (and other communities) can be synthetically recreated in microfluidic devices. 

[1] Brune, A., D. Emerson, and J.A. Breznak, The Termite Gut Microflora as an Oxygen Sink: Microelectrode Determination of Oxygen and pH Gradients in Guts of Lower and Higher Termites. Appl Environ Microbiol, 1995. 61, 2681-2687.

[2] Brune, A., Termite Guts: The World's Smallest Bioreactors. Trends Biotechnol., 1998. 16, 16-21.

[3] Kadilak, A. L., Liu, Y., Shrestha, S., Bernard, J. R., Mustain, W. E., and Shor, L. M., Selective Deposition of Chemically-bonded Gold Electrodes onto PDMS Microchannel Side Walls. J. Electroanal. Chem.
, 2014. 727, 141-147.

Figure 1
Graphene Ring Nanoelectrodes (GRiNs): Application As an Electroanalytical Sensor
Authors: Ferrer-Huerta Miriam , Boxall Colin , Dickinson James William , Andrieux Fabrice , Freeman Neville J
Published: February 2020

We present the fabrication and characterisation of Graphene Ring Nanoelectrodes (GRiNs) at size ranges below 10 nm. Graphene was obtained from chemically exfoliated graphite oxide (GO) prepared by a modified Hummers’ method. GO was dip coated from colloidal solution onto optical fibre and the consequential GO layer was reduced to graphene by both chemical (hydrazine) and thermal treatments. Subsequent electrical connections and isolation of the optical fibre were carried out.

In an attempt to reduce the thickness of the ring electrodes, mechanical exfoliation of the graphene layer was conducted using an adaptation of the classic Scotch tape method. This approach stripped off all the graphene layers from the optical fibre and was abandoned because it was not conducive to achieving GRiNs in the sub-5 nm domain. The lower limit for electrode thickness is 0.335 nm corresponding to a single layer of graphene.

In light of this previous trial, it was proven that the concentration of GO suspension and its viscosity governs the thickness of the graphene layer. Results show that previously used GO suspension concentrations of 10 wt% yield a thick fluid with non-newtonian rheological properties that result in GRiNs with micrometer range ring electrode thicknesses. Thinner, newtonian fluids are obtained at 1, 1.5, 2, 2.5, 4, 6, 8 and 8.5 wt%. Non-newtonian fluids are obtained at 8.6 wt%. GRINs fabricated using 4 wt% GO solution are found to be conducting and, through the application of electrochemical sizing methods, were proven to have ring electrode thicknesses in the sub-10 nm range.

The resultant nanoelectrodes are highly reliable, the nanoring design allows for efficient utilisation of electrochemically active edge sites. The behaviour of the so-formed graphene ring nanoelectrodes was studied using the well-known electrochemically reversible system of Fe(CN)6
4/3- with GRiNs of ring thicknesses 5-75 nm. Test results revealed that at thicknesses sub-10 nm, electron transfer rate constants are one order of magnitude larger than those obtained using macroelectrodes. Further, such GRiNs exhibit specific capacitances of two orders of magnitude greater than those reported for equivalent macroelectrodes.

These nanometer dimensions result in: increased densities of charge, and thus energy storage at the electrode surface compared to macroscopic systems; and enhanced rates of reactant mass transport to, and electron transfer across, the electrode/electrolyte interface (due to the more rapid potential drop within the diffusion double layer). These effects are especially enhanced at critical electrode dimensions of below 10 nm. Thus, their study consequently provides molecular level insight into nanoelectrochemistry application areas such as energy storage systems and environmental monitoring.
(Invited) Self-Assembly on Graphene and 2D Materials
Authors: De Feyter Steven
Published: February 2020

Nanostructured monolayers of molecules can be formed at a variety of interfaces. At a liquid-solid interface, such two-dimensional (2D) molecular assemblies can be created by depositing a solution of the compound of interest on top of the substrate (drop casting) or by immersing the substrate into a solution (dip coating). Very often, only weak non-covalent interactions govern the interplay between molecules and molecules and substrate.

Advanced interface specific methods such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM) provide structural and other types of information at the nanoscopic level.

In this presentation, we focus on several aspects of molecular self-assembly at the interface between a liquid or air, and substrates such as highly oriented pyrolytic  graphite and graphene. Highly oriented pyrolytic graphite can be considered as an excellent model surface for adsorption and self-assembly of molecules on graphene.

We will discuss the concept of 2D crystal engineering and the effect of solvent, solute concentration and temperature, bringing insight into thermodynamic and kinetics aspects of the self-assembly process at the interface between a liquid and graphite or graphene.1,2

Based on these insights, we will demonstrate molecular self-assembly based functionalization of graphite and graphene.3

Various applications will be presented,4 including tunable doping of graphene based field effect transistors5.

(1) De Feyter, S.; De Schryver, F. C.  Chem.Soc.Rev. 2003, 32, 139.

(2) Mali, K. S.; Adisoejoso, J.; Ghijsens, E.; De Cat, I.; De Feyter, S. Acc.Chem.Res. 2012, 45,  1309.

(3) Li, B.; Tahara, K.; Adisoejoso, J.; Vanderlinden, W.; Mali, K. S.; De Gendt, S.; Tobe, Y.;  De Feyter, S. ACS Nano 2014, 7, 10764.

(4) Xu, H.; Saletra, W. J.; Iavicoli, P.; Van Averbeke, B.; Schenning, A. P. H. J.; Beljonne, D.; Lazzaroni, R.; Amabilino, D. B.; De Feyter, S. Angew. Chem. Int. Ed. 2012, 51, 11981.

(5) Li, B.; Klekachev, A.; Cantoro, M.; Huyghebaert, C.; Stesmans, A.; Asselberghs, I.; De Gendt, S.; De Feyter, S. Nanoscale 2013, 5, 9640.

Figure 1
Accelerated Materials Design of Solid Electrolyte Materials Using First Principles Computation
Authors: Mo Yifei
Published: February 2020

The design and discovery of new materials have been pursued through a trial-and-error manner largely based on human intuition and serendipity. This traditional materials design process is time consuming and labor intensive, and often takes decades to bring a new material to market. Accelerated development of novel, high-performance materials are critical to address our societal challenges for electrochemical energy storage and conversion. First principles computation, which can predict materials properties with little experimental input, has the potential to accelerate the development of new materials. In this presentation, I will demonstrate the use of first principles computation methods to design and discover solid electrolyte materials for all-solid-state Li-ion battery and solid oxide fuel cells. Using recently identified lithium thio-phosphate lithium super ionic conductor and sodium bismuth oxide oxygen conductor as examples, I will first show the use of first principles computation to provide unique materials insights, such as in identifying the performance limiting factors for these new materials. The first principles computation methods in predicting the phase stability, chemical stability, and diffusional properties will be demonstrated to address the materials issues of these solid electrolyte materials. New materials with enhanced properties will be designed using the accelerated first principles approach. Our first principle calculation results are in good agreements with experiments, and the newly predicted materials are experimentally confirmed by multiple studies.