bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogenation at Metal-Ligand Interfaces in CO2 Electrochemical Reduction
Authors: Fang Yuxin , Cheng Xun , Xu Ye , Flake John 
Published: February 2020

CO2 holds the potential to a significant source of renewable carbon. Previous studies have shown that it can be converted to CO, CH4, HCOOH, CH3OH and other higher order hydrocarbons suitable as fuels or chemical intermediates. The electrochemical approach holds the advantage in using renewable electric source (wind, solar and tide). Extensive experimental and theoretical studies have been done on pure metals (such as Au, Ag, Cu, etc.)1, 2 range from bulk to nano scale3, Cu4 appear to be the only catalyst that is capable of perform hydrogenation to yield hydrocarbon liquid products at the expense of single product selectivity and overpotential. Density function theory based simulation suggest the unique binding energies of CO* and COH* are the key for copper to perform the hydrogenation. 5

We took the inspiration from nature’s enzyme chemistry6 which manipulate metal nanoclusters with ligands in photosynthesis, explored the possibility using engineered metal-ligand electrocatalyst to yield the hydrocarbon liquid products. Our previous work has shown that thiolate ligands can facilitate reduction and hydrogenation at neutral to mildly acidic pKa. Suitable ligands can significantly enhance the yield of CO or HCOOH (usually trace on Au) production. We are taking a step further by depositing strong CO binding metal nanoparticles on to salinized semiconductor substrate with proton donor group to create metal-ligand interfaces. We have observed enhanced CH3OH production in such systems. The engineered metal-ligand interface thus appear to be a highly promising method to promote hydrogenation routes in CO2 electrochemical reduction.
Reference:
1. Y. Hori, A. Murata, R. Takahashi and S. Suzuki, Chemistry Letters, 16, 1665 (1987).
2. Y. Hori, in Modern Aspects of Electrochemistry, C. Vayenas, R. White and M. Gamboa-Aldeco Editors, p. 89, Springer New York (2008).
3. D. R. Kauffman, D. Alfonso, C. Matranga, H. Qian and R. Jin, Journal of the American Chemical Society, 134, 10237 (2012).
4. K. Manthiram, B. J. Beberwyck and A. P. Alivisatos, Journal of the American Chemical Society, 136, 13319 (2014).
5. C. Shi, H. A. Hansen, A. C. Lausche and J. K. Norskov, Physical Chemistry Chemical Physics, 16, 4720 (2014).
6. B. El-Zahab, D. Donnelly and P. Wang, Biotechnology and Bioengineering, 99, 508 (2008).
Electrochemical Studies of Zinc/Cysteine Interactions
Authors: Doan Michelle Y , Worosz Matthew A. , Cheek Graham T. 
Published: February 2020

Introduction
The amino acid L-cysteine has been studied because of its role in several biochemical pathways (1). Electrochemical studies are possible due to the redox characteristics of the sulfhydryl group, so that the electrochemical characteristics of L-cysteine can be determined by voltammetric methods (2). In this study, the biochemical importance of zinc(II)/cysteine complexes in proteins (“zinc fingers”) has prompted an investigation of the interaction of ZnSO4with L-cysteine in various media.
Experimental
L-Cysteine was obtained from Sigma-Aldrich Company, and ZnSO4
.7 H2O was obtained from ThermoFisher Scientific. A Gamry Interface 1000 potentiostat with Gamry Framework software was used to carry out electrochemical experiments. Potentials are referenced against a Ag/AgCl reference electrode. Platinum and glassy carbon electrodes were purchased from BASi. Gold electrodes were obtained from eDAQ.
Results and Discussion
In a study of the complexation of Zn2+ by L-cysteine in pH 7.4 phosphate buffer, it was found that addition of ZnSO4
. 7 H2O to the buffer solution produced a cloudy appearance due to the low solubility of the resulting Zn3(PO4)2 . Upon addition of L-cysteine, the system was still cloudy at the 1:1 L-cysteine : Zn2+ point; however, at the 2:1 L-cysteine : Zn2+ point, the solution became clear. This behavior evidently occurs because the interaction of Zn2+ with L-cysteine is stronger than is its interaction with phosphate. These results are consistent with Zn(cys)2 complexation reported in the literature (3). The corresponding voltammograms at glassy carbon are shown in Figure 1. For ZnSO4 addition, the scan showed only a very small zinc stripping peak at the negative end of the potential range. At the 1:1 L-cysteine : Zn2+ point, processes are clearly evident for zinc deposition/stripping, and oxidation of complexed L-cysteine is observed at +0.7 V vs Ag/AgCl. This oxidation process is slightly altered compared to that observed for only L-cysteine (no added Zn2+) (2). Similar behavior for the oxidation processes was also observed at gold. Further additions of L-cysteine gave larger currents for the L-cysteine oxidation process. These results support the uptake of zinc ion into the solution as L-cysteine interacts with Zn2+, initially added as ZnSO4
. 7 H2O in pH 7.4 phosphate buffer.
References

C.K. Mathews, K.E. Van Holde, D.R. Appling, and S. J. Anthony-Cahill, Biochemistry, 4th Edition, Pearson Canada, Toronto, 2013.

G. T. Cheek and M. A. Worosz, ECS Transactions, 2016, 72(27), 1-8.

S. Foley and M. Enescu, Vibrational Spectroscopy, 2007, 44, 256-265.

Figure 1. Cyclic voltammograms at glassy carbon (3 mm diameter) in aqueous pH 7.4 phosphate buffer, 100 mV/s scan rate.
[ Dashed red line : ZnSO4 . 7 H2O, 2.1 mM nominal concentration ]
[ Solid black line : Addition of 2.4 mM L-cysteine to previous solution ]

Figure 1
X-Ray Spectroscopic and Electroanalytical Studies on the Bio-Electic Interface of Metal Oxide Semiconductors and Algal Proteins and Biofilms
Authors: Braun Artur 
Published: February 2020

Artificial photosynthesis has been the domain of molecular biology and biophysics and is traditionally restricted to the study of modified natural photosynthetic organisms and their components and has not matured yet to a technology. Photovoltaics is the established field of electric power generation with semiconductor solar cells and has made it to technologies with market share and commodity. Photoelectrochemical cells based on the principles of semiconductor photoelectrochemistry are right now about to become a technology and can produce solar fuels. I present a hybrid approach where bio-organic motifs are combined with metal oxide semiconductor substrates so as to enhance the performance of photoelectrodes.
Specifically, we have functionalized the surface of the hematite photoelectrode with the light harvesting antenna protein c-phycocyanin (CPC) and ran it as a bio-hybrid pphotoelectode in strong alkaline and neutral pH buffer saline - and found that the chromophores surpass the denaturation of the proteins and still can be performance enhancing. Further refinement of the assembly by genetic engineering of the algae to obtain a histidine tagged CPC was also investigated, as well as the blending the system with melanin. We carried out impedance studies and synchrotron based resonant valence band photoemission studies to learn abu the cahrge transfer across the bio-metal oxide interface.
Finally we grew an algal biofilm on the photoelectrode and operated it under photoelectrophysiological conditions in an ambient pressure XPS chamber under 150 mTorr water vapor and determined the valence band shift under different electric bias and light/dark influence.
[1] A. Braun, F. Boudoire, D. K. Bora, G. Faccio, Y. Hu, A. Kroll, B. S. Mun, S. T. Wilson, Biological components and bio-electronic interfaces of water splitting photo-electrodes for solar hydrogen production, Chem. Eur. J. 2015, 21(11), 4188-4199.
Thermodynamics of Polymer Electrolyte Membranes in Contact with Concentrated Electrolyte Solutions
Authors: Peng Jing , Goenaga Gabriel A. , Zawodzinski Thomas A. 
Published: February 2020

In this study, we build off our recent development of a database of data describing the composition of polymer electrolytes in contact with various acids, bases and salts. This situation is common in practical electrochemical systems such as redox flow batteries and electrochemical reactors. For example, the vanadium redox flow battery (VRFB) electrolyte solutions consist of several molar solutions of aqueous sulfuric acid (with other acids used in certain cases) and up to 2M vanadium salts. As we have shown, these concentrations cause the general phenomenon of breakdown of the Donnan exclusion effect in a variety of polymer electrolyte membranes, both cation and anion exchanging membrane types.1,2,3 A description of these processes would be useful in helping to separate the effects of various modifications of the membrane composition and structure on its behavior.
We develop the groundwork for a thermodynamic description of uptake of ionizable species by polymer electrolyte membranes in contact with concentrated solution electrolyte solutions using the VRFB membrane-electrolyte combination as our test case.
We note that all such descriptions of the behavior of polymer systems entails the assumption of a ‘local’ equilibrium, relevant for short times. Here the adjective short refers to times long enough for uptake processes to occur but short enough that the polymer itself does not have time to change from its initial state, set by its thermal history. This allows us to assess membranes that might be thermally ‘re-arranged’ as separate entities, thus isolating any effects of the treatment.
We first develop a description of the local equilibrium of the acid solution with the membrane. As Tang et al showed,1 this has several interesting features that are generic to acid uptake into Nafion and related polymer electrolytes. A convenience of this approach is the broad availability of descriptions of the acid solution properties.
Once a description of the acid-membrane equilibrium is available, we proceed to consider the situation with added vanadium. For simplicity, we will begin by developing the case for VOSO4 solutions in acid. In this case, we need to reassess the solution thermodynamics, adding some measurements specific to a given ternary composition. We will describe these measurements in the oral presentation.

Acknowledgements

We gratefully acknowledge the support of this work by the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability (Dr. Imre Gyuk) and by the Office of Naval Research. We also thank 3M for providing membranes.
(Invited) T-Chip, a Biosensor Based on the Electron Tunneling: Theory and Experiment
Authors: Park Young June , Yun Jun Yeon , Lee Won Cheol , Lee Young Eun , Kim Kyoung Yeon 
Published: February 2020

The presentation covers an electrical biosensor platform (T-chip) based on the electron tunneling phenomenon between the metal electrode and the methylene blue (MB) molecules. Firstly, the general idea of the T-chip is introduced. Secondly, the practical application of the T-chip for detecting biomarkers of the cancer is suggested. Finally, the numerical simulation of the T-chip considering the electron tunneling and the transport of ions in the electrolyte is introduced.
To detect the target biomarkers in aqueous solution, the T-chip is integrated with the peptide molecules as the probe molecule of which end terminal was functionalized with the redox sites providing the electron states for tunneling. An asymmetric gold electrode structure of the T-chip facilitates a simple 2-electrode structure and reliable electrical measurement without adopting a reference electrode used in the conventional electrochemical system.
As an example of the biosensor application, we selected the matrix metalloproteinase-9 (MMP-9) as the target biomarker which indicates metastasis of the cancer and tumor invasion. As the probe molecules, a peptide sequence conjugated with the MB was designed to be cleaved by the MMP-9. As an electrical indicator of the probe-target cleavage event, the MB was chosen. The cleavage event causes the reduction of the number of the MB sites (electron tunneling states) which leads a decrease in the electron tunneling current.
To describe the physical model and evaluate the electrical characteristics of the T-chip, a numerical simulator (3-dimension) has been developed. To estimate the electron tunneling rates between the electrodes and the MB states, we used the non-equilibrium Green’s function (NEGF) method. Additionally, the ion motions in electrolyte is calculated by using drift-diffusion as the continuity equation. Finally, the terminal current due to the electron tunneling and ion movement was extracted by using the extended Ramo-Shockley theorem.
Theory and experiment of the tunneling based biosensor will enhance the potential of success of the electrical biosensor through detailed understanding of the molecules and surface chemistry involved in the sensor system.
Silicon Anisotropic Etching in Ternary Solution Composed of TΜΑΗ+Triton+NH2ΟΗ
Authors: Swarnalatha Veerla , Narasimha Rao Avvaru Venkata , Pal Prem 
Published: February 2020

Wet chemical etching is extensively used in the fabrication of microelectromechanical systems (MEMS) owing to its several benefits such as low cost, easy handling, and bulk production [1, 2]. TMAH and KOH are most widely employed etchants for silicon anisotropic etching. In these two etchants, TMAH is preferred when complementary metal oxide semiconductor (CMOS) compatibility is a major concern and the oxide layer is used as mask material [2, 3]. Etching behavior of TMAH can be modified by the incorporation of different kinds of additives such surfactants, alcohol, etc. [2-4]. Significant amount of research has been done to modify the etching characteristics by adding some additives, however very less is reported on TMAH-based ternary solutions. Present research reports the anisotropic etching characteristics of silicon in various concentrations of TMAH (5 wt%, 15 wt%, and 25 wt%) solutions containing 10% NH2OH and Triton-X-100 ranging from ppb to ppm level. The etch rate, undercutting at convex corners, and etched surface morphology are investigated in different compositions of ternary solutions (TMAH+NH2OH+Triton). Optical microscope, scanning electron microscope (SEM), and three-dimensional (3D) measuring laser microscope are employed for the characterization of etched surface morphology and to measure the etch depth and undercutting at convex corners. Figure 1 presents the etch rate of Si{100} and the undercutting rate (U
<110> = l
<110>
/d, l
<110>: undercutting length along <110> direction, d: etch depth) at convex corners. High etch rate and undercutting are achieved in NH2OH-added 15 wt% TMAH, while significantly less undercutting with reasonably good etch rate of Si{100} (Er = 18 µm/hr) is obtained in 25 wt% TMAH+10%NH2OH+1ppm Triton. The high undercutting is desirable when freestanding structures are fabricated, while it is unwanted effect when microstructures with convex corners have to be fabricated such as mesa structure. The present research is very useful for engineering applications for the fabrication of microstructures using CMOS-compatible silicon bulk micromachining for MEMS-based devices.

References:

[1] I. Zubel, M. Kramkowska, J. Micromech. Microeng. 1
5 485 (2004).
[2] P. Pal, and K. Sato. J. Micromech.Microeng. 19 055003 (2009).
[3] A. Ashok and P. Pal, Microsy. Technol. 1-8 (2015).
[4] Y.W. Xu, A. Michael, C.Y. Kwok, Sens. Actuators A 166, 164-171 (2011).

Figure 1
Real Time Quantification of Phenolic Compounds in Oil and Gas Wells Produced Wastewater Using a QCM Sensor
Authors: Barrera Magda Lorena Lorena , Pedraza Julio Andrés , Ríos Fabián Alirio 
Published: February 2020

Phenols (phenol, m-cresol, o-cresol and p-cresol) are contaminant compounds and due to its toxicity and persistence in the environment are listed in the Environmental Protection Agency as dangerous substances [1]; its presence in the environment is widely associated with wastewater effluents as is the produced water generated by oil and gas production.
One of the systems that has been gaining importance to measure phenols in real time is the Quartz Crystal Microbalance (QCM). This technique comprises a thin quartz crystal sandwiched between two metal electrodes and senses the changes in frequency that suffers the quartz crystal when a certain amount of mass is deposited on its surface [3].
In order to improve the sensibility of compounds to measurement using a QCM have been used coatings on quartz crystal electrode surface, for example for phenols determination polymethylmethacrylate (PMMA) is used. The main objective of this research is to determine in real time and in continuous flow the concentration of phenolic compounds in produced water using the technique QCM with PMMA as coating on quartz crystal electrode surface.
This work is conducted in three stages mainly: 1. Determination of a suitable layer of PMMA to use as coating, 2. Evaluation of the effect of the concentration of phenols, pH and flow rate in the measurements by QCM, 3. Comparison of sensitivity and time response obtained in the technique QCM with standard method by colorimetry.
Results have shown that the PMMA films are more uniform when is used dichloroethane as solvent instead of chloroform and the stability and sensitivity in the measurements improve due to the vapor pressure of solvent that allows more dispersion of the polymer during spin coating, which is consistent with other authors [2]. Increase in the concentration of phenolic compounds, the flow rate and the pH increases the changes in frequency of the quartz crystal.

Keywords

: Quartz crystal microbalance, PMMA, phenols, produced water, real time.

Mirmosheni, A., Oladegaragoze, A. Application of the quartz crystal microbalance for determination of phenol in solution. 2003. Sensors and Actuators, B: Chemical, Vol.98 (1), p. 28-36.

Mohajerani, E. Morphological and thickness analysis for PMMA spin coated films. 2007. Journal of optoelectronics and advanced materials, Vol. 9 (12), p. 3901-3906.

Reddy, S. Detection of phenol in aqueous solution using an AT-cut quartz thickness shear mode sensor. 2000. Materials Science and Engineering C, Vol. 12 (1), p. 23-28.
Effect of Surfactant and Alcohol Additives on Etching Characteristics in Aqueous Potassium Hydroxide Solutions
Authors: Narasimha Rao Avvaru Venkata , Swarnalatha Veerla , Pal Prem 
Published: February 2020

Anisotropic wet etching is a low cost technique for silicon bulk micromachining to fabricate MEMS components such as cantilevers, diaphragms, etc. It is inevitable for the fabrication of microstructures with slanted sidewalls and to remove underneath material for the realization of freestanding microstructures. Potassium hydroxide (KOH) is a popular etchant as it provides high anisotropy between {100}/{110} and {111} planes. In order to alter the etching characteristics, the effect of various kinds of additives such as isopropyl alcohol (IPA), surfactants (Triton X-100) in pure KOH is studied [1-3]. In this work, we studied the etching characteristics of ternary solutions composed of KOH + Triton X-100 + IPA. The concentration of KOH is varied from 5-40 wt% in step of 5 wt%, while the concentrations of Triton and IPA are kept fixed at 0.1 vol% and 15 vol%, respectively. In the different compositions of ternary solutions, the etch rate and etched surface morphologies of Si{100}, Si{110} and Si{111} are investigated. In addition to that the undercutting at convex corners, which is very important parameter for designing compensation structure to protect convex corner and to estimate etching to release the structure from the substrate, is measured. In order to explore the thermal oxide as mask and structural material, the etch rate of silicon dioxide is also measured. In the ternary solution comprising low concentration KOH, the etching characteristics are more significantly affected by Triton than IPA. However, in the case of ternary solution containing high concentration KOH, IPA influences etching characteristics more prominently than Triton. The systematic study of etch rate, etched surface roughness, and undercutting at convex corners in ternary solution presented in this work is very useful to select the composition of ternary solution for MEMS applications as per the requirement.

References:

[1] I. Zubel, M. Kramkowska, Sens. Actuators A 101 255-261 (2002).
[2] P. Pal, A. Ashok, S. Haldar, Y. Xing, K. Sato, Micro Nano Lett. 10 224-228 (2015).
[3] K.P. Rola, I. Zubel, J. Microelectromech. Syst. 22 1373-1382 (2013).
Fabrication of Three-Dimensional Woodpile Cerium Oxide Nanostructure Via Solution-Based Soft Nanoimprint Lithography for Enzymatic Glucose Sensor
Authors: Zhou Yiliang , Uzun Sema Demirci , Briseno Alejandro L. , Carter Kenneth R. , Watkins James J. 
Published: February 2020

Fabrication of ultra-high surface area electrodes can improve sensitivity for analyte detection. Here we report a scalable method for producing three-dimensional, nanoscale woodpile structures of cerium oxide for use in glucose sensors. A CeO2 nanoparticle based ink was used to directly pattern 500 nm wide grid structures via a solution-based soft nanoimprint lithography technique. The residual layer of the imprinted pattern was minimized by optimization of CeO2 concentration, speed and time of spin coating. Multi-layered woodpile structures of CeO2 were then achieved by a layer-by-layer imprint strategy. To prevent defects at the intersection of the layers, titanium diisopropoxide bis(acetylacetonate) was added as a binder. SEM data revealed that three-dimensional woodpile cerium oxide structures were successfully fabricated over a large areas.
Then, an enzymatic glucose sensor was fabricated by printing such a CeO2 woodpile structure on a gold-coated substrate. Cyclic voltammetry and chronoamperometry were applied for detecting glucose in PBS buffer solution (50 mM, pH 7.0, 25 °C). Experimental data showed the sensitivity of glucose sensors can be improved by increasing the number of layers. The tetralayer CeO2 glucose sensors exhibited high sensitivity (8.2 µA mM-1 cm-2), short response time (1-2 s) and long linear range (0.02 mM-2.0 mM). These results indicated the three-dimensional woodpile structure of CeO2 is a promising material for high sensitivity biosensors.