bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
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.
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.
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).

M. Teymouri, and E. Bagherzadeh, J. Mat. Sci., 30, 3005, (1995).

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

I. Popescu, A. Urda, T. Yuzhakova, I. Marcu, J. Kovacs, and I. Sandulescu, C. R. Chimie, 12, 1072, (2009).

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).
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