bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Surface Adsorption and Electrode Passivation during Electrochemical Oxidation of Redox-Active Organics
Authors: Shaheen Nora Adel , Carino Emily , Yang Zhenzhen , Trahey Lynn , Srinivasan Venkat , Akolkar Rohan
Published: November 2022

Redox-active organic molecules (ROMs) have gained interest as electroactive materials for redox flow batteries (RFBs). Electrochemical properties of ROMs, i.e., their solubility and redox potential, can be tuned through molecular engineering of the base molecule. Previously, we reported values of the apparent anodic charge transfer coefficient α (values approaching 1) associated with the electrochemical oxidation of a model ROM, 4-hydroxy-TEMPO.1 Also, we have proposed an adsorption-mediated mechanism to explain this unusual value of α, and have presented evidence to support the occurrence of adsorbed intermediates. Here, we extend this investigation to gain further insights using techniques of slow-scan voltammetry and electrode cycling, and apply them to other ROMs. We will discuss results of spectroscopic and micro-gravimetric studies, which provide further insights into the physicochemical properties of the adsorbed surface-passivating films. Ramifications of these to implementation of ROMs in flow batteries will be discussed too.

[1] N. A. Shaheen, M. Ijjada, M. B. Vukmirovic, R. Akolkar. J. Electrochem. Soc.,
167 (2020) 143505.

Acknowledgements:

Investigation of the model ROM was supported by Breakthrough Electrolytes for Energy Storage (BEES)—an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0019409. Work completed at Argonne was supported by the Joint Center for Energy Storage Research (JCESR), a U.S. Department of Energy, Energy Innovation Hub, and by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by ORAU under contract #DE‐SC0014664. All opinions expressed in this paper are the author’s and do not necessarily reflect the policies and views of DOE, ORAU, or ORISE.
(Invited) In-Situ/Operando X-Ray Absorption Spectroscopy: Methods and Challenges in Electrocatalysts Characterization
Authors: Zitolo Andrea
Published: November 2022

During the last decades X-ray absorption spectroscopy (XAS) has proved to be a fundamental tool for understanding the nature of active catalytic species, especially in the form of highly dispersed, amorphous phases, and in the case of single atom catalysts. [1-4] The efforts in developing this technique under working conditions are justified by the extraordinary information that can be obtained on the identity of active species, reaction intermediates and activation/degradation phenomena. Clearly, the challenges embrace many fields: 1) catalysts can be very complex materials, comprising different, even disordered, phases; 2) it is a technique that uses synchrotron radiation, and the design of an appropriate experimental set-up requires know-how, but also synergy with a beamline team; 3) a rigorous interpretation of the XAS data requires high level of expertise to avoid easy misinterpretations, and the continuous development of new data analysis methods.

This talk aims to discuss in-situ/operando XAS studies to investigate the activity and stability of novel catalysts during electrochemical reactions in proton exchange membrane fuel cell (PEMFC) devices and during CO2 reduction. In most studies with operando XAS, electrochemical studies have been performed in liquid electrolyte cells. While instructive, the performance and stability observed in liquid electrolyte at room temperature is however never directly transferable to the performance in a PEMFC device, operating at high temperature, high current density, and with a solid-polymer electrolyte interface. This current limitation can be overcome by the design of an appropriate cell able to isolate and extract the signal coming from the area where the reactions take place.

Part of the talk will also be devoted to some time-resolved structural probing techniques to follow a reaction pathway under high temperature or pressure conditions.

M. Elmaalouf,M. Odziomek, S. Duran, M. Gayrard, M. Bahri, C. Tard, A. Zitolo, B. Lassalle-Kaiser, J.Y. Piquemal, O. Ersen, C. Boissière, C. Sanchez, M. Giraud, M. Faustini and J. Peron Nat Commun
2021, 12
, 3935

D. Karapinar, N.H. Tran, N.R. Sahraie, J. Li, D. Wakerley, N. Touati, S. Zanna, D. Taverna, L.H. Galvão Tizei, A. Zitolo, F. Jaouen, V. Mougel, M. Fontecave, Angewandte Chemie International Edition
2019, 58(42), 15098-15103

Zitolo, A.; Ranjbar-Sahraie, N.; Mineva, T.; Li, J.; Jia, Q.; Stamatin, S.; Harrington, G. F.; Lyth, S. M.; Krtil, P.; Mukerjee, S.; Fonda, E.; Jaouen, F., Nat Commun
2017,
8 (1), 957

A. Zitolo, V. Goellner, V. Armel, M. T. Sougrati, T. Mineva, L. Stievano, E. Fonda, F. Jaouen, Nature Materials
2015, 14, 937-942
Zip Membranes: The Coveted Blockade for the Vanadium Crossover in Flow Batteries
Authors: Crivellaro Giovanni , Vezzu Keti , Pagot Gioele , Lorandi Francesca , Pace Giuseppe , Gambaro Chiara , Meda Laura , Di Noto Vito
Published: November 2022

Vanadium Redox Flow Batteries (VRFBs) are considered as a key technology in the field of large-scale energy storage systems [1, 2]. Unfortunately, their capabilities are compromised by the crossover of active species through the membrane which reduces the overall efficiency during operation and hinders the long-term capacity storage [3]. In this work, an extremely selective proton exchange material is proposed. “Zip-like” Ion Exchange Membranes (ZIEMs) are prepared by means of an acid-base reaction between the cationic and anionic functionalities of two interacting ionomers. The strong electrostatic crosslinking interactions between the two components generate an overall improvement of thermal and mechanical properties, and the permeation of vanadium ions is strongly hindered (the best performing membrane has a selectivity of 3.1⸱105 S⸱min⸱cm-3, which is almost 50 times higher than Nafion). The best performing membranes show outstanding VRFB performance with a stable coulombic efficiency (>98% at 50 mA⸱cm-2), and a retained capacity of 82% after 100 cycles compared to the 21% of the same device with a Nafion 212 membrane. The results presented here show how ZIEM family of membranes can be regarded among the best performing ion exchange membranes up-to-date.

Acknowledgements

The authors wish to thank the fruitful collaboration within the project “Development of high-selectivity ion-exchange membranes for application in next-generation redox flow batteries” funded by ENI S.p.A., contract 2500026228. In addition, the authors wish to thank the SID2020Project of the Department of Industrial Engineering, University of Padova “A New frontier in Hybrid Inorganic-Organic Membranes for Energy Con-version and Storage Devices” (Prot. BIRD201244) for funding.

References

[1] R.K. Emmett, M.E. Roberts, Recent developments in alternative aqueous redox flow batteries for grid-scale energy storage, Journal of Power Sources, 506 (2021) 230087.

[2] C. Sun, E. Negro, A. Nale, G. Pagot, K. Vezzù, T.A. Zawodzinski, L. Meda, C. Gambaro, V. Di Noto, An efficient barrier toward vanadium crossover in redox flow batteries: The bilayer [Nafion/(WO3)x] hybrid inorganic-organic membrane, Electrochimica Acta, 378 (2021) 138133.

[3] V. Di Noto, K. Vezzù, G. Crivellaro, G. Pagot, C. Sun, L. Meda, I.A. Rutkowska, P.J. Kulesza, T.A. Zawodzinski, A general electrochemical formalism for vanadium redox flow batteries, Electrochimica Acta, 408 (2022).
(Invited) A Formalism Relating the Relative Humidity to the Proton Conductivity Mechanism of Membranes
Authors: Di Noto Vito , Vezzu Keti , Lorandi Francesca , Pagot Gioele , Paddison Stephen , Zawodzinski Thomas A.
Published: November 2022

The relationship between relative humidity of gas phase and proton conductivity in proton exchange membranes has been subject of extensive investigations [1],[2]. Herein, a theoretical framework is presented which describes proton transport in relation to stepwise equilibria that reflect the water uptake. In the proposed model, at first, the hydration process is treated as a stepwise equilibrium process, in agreement with experimental observations. Several hierarchical levels of structure evolve with increasing hydration. These levels are easily confirmed by the analysis of the electric response of perfluorinated based membranes by complex dielectric and conductivity spectra. Thus, a wide range of literature data on hydration of Nafion as a function of activity and temperature has been analyzed by means of the proposed model to extract chemical parameters diagnostic of the type of interactions characterizing the hydrophilic domains of membranes.

These parameters, which are crucial in order to modulate the ion transport phenomena in ionomers, are then introduced into the model to describe the functional dependence of conductivity on water activity in gas phase. The treatment of proton conductivity is built on the approaches commonly adopted to describe transport in solids [3]. Key proton migration phenomena appropriate to the levels of the structural hierarchy are considered. The conductivity model is used to describe a set of conductivity vs. water uptake data as a function of temperature, with data taken to exceptionally low water contents. The formalism is then used to analyze a set of data for a perfluorosulfonic acid (PFSA) membrane as a function of hydration, temperature and polymer equivalent weight. The main advantage of the proposed framework is the possibility of a straightforward application to multiple membrane types based on the energetics of water uptake. Actually, the focus on chemical interactions allows to better correlate the effects of the morphology and relaxation events of the matrix to the proton migration phenomena of the membrane.

Acknowledgements

This work has received funding from: (a) the European Union’s Horizon 2020 research and innovation program under grant agreement 881603; (b) the project ‘Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells’ funded by EIT Raw Materials.

References

[1] Kreuer K.D., Schuster M., Obliers B., Diat O., Traub U., Fuchs A., Klock U., Paddison S.J., Maier J. 2008 J. Power Sources
178 499-509.

[2] Maalouf M., Pyle B., Sun C.N., Wu D., Paddison S.J., Schaberg M., Emery M., Lochhaas K.H., Hamrock S.J., Ghassemi H., Zawodzinski, T.A. 2009 ECS Trans.
25 1473.

[3] A.D. LeClaire and A. Rabinovitch, 1981, J. Phys. C, 14 3863.
(Invited) Photoinduced Electron Transfer in Mechanically Interlocked Suit[3]Ane Systems
Authors: Stasyuk Anton , Stasyuk Olga , Solà Miquel , Voityuk Alexander A.
Published: November 2022

Mechanically interlocked molecules (MIMs) attract significant attention of scientists over the past few decades due to their unusual architecture. For a long time, architectures of MIMs were represented by catenanes, rotaxanes, molecular knots, and their derivatives. Only several years ago, a new type of MIMs that do not possess interlocked rings or dumbbell shaped molecule threaded through a macroring was introduced. Suitanes – a class of MIMs, which consist of two separate components - contains a body with two or more rigid limbs protruding outwards and a close-fitting, all-in-one suit.

We present the results of computational modelling of the photoinduced processes in the recently reported by F. Stoddart two-component MIM - suit[3]ane, and similar systems with aromatic 3-fold symmetric bodies.[1] The reported suit[3]ane contains a benzotrithiophene (BTT) derivative with three n-hexyl substituents (BTT-3C6
) as a body and 3-fold symmetric pyridinium-based cage, namely HexaCage6+ (HC6+∙6PF6
-
), as a suit.

Analysis of the ground state properties of the suit[3]anes show that low LUMO of HC6+∙6PF6
-
and its ability to delocalize charge make this cage an efficient electron acceptor. The TDDFT calculations for a series of inclusion complexes (HC6+∙6PF6
-

⊃
XXX, where XXX are aromatic 3-fold symmetric bodies) revealed that the photoinduced electron transfer process is favorable not only for the complexes with strong donors, such as thiatruxene or benzotrithiophenes, but also for poor donors, such as benzotrifuran. The photoinduced charge separation in the studied complexes occurs on a picosecond time scale. The computations predicts very similar electronic properties not only for single unit of suit[3]ane but also for its aggregates.

The high stability of suit[3]anes in combination with their photoinduced electron transfer properties makes this new class of interlocked molecules promising materials for photovoltaic applications.[2]

References:

[1] J. F. Stoddart et al., J. Am. Chem. Soc.
2020, 142, 20152.

[2] A.J. Stasyuk et al., J. Mater. Chem. C, 2021, 9, 9436.

Figure 1
Determination of Individual Gibbs Energies of Ion and Electron Transfer in Electrochemical Insertion Processes
Authors: Muñoz Eduardo , López Silvana , Cáceres Gustavo , Rojas Victor , Vera Cristobal
Published: November 2022

Based on three-phase electrode models, we study to access the Gibbs energy contributions for the transfer of ions and electrons in Prussian blue analogs since they have long life cycles and high energy efficiency. Ni[Fe(CN)6] (HCFNi) and Cu[Fe(CN)6] (HCFCu) were preliminarily synthesized by a hydrothermal process. The obtained HCFNi powders were supported on a paraffin-impregnated graphite electrode in contact with an organic electrolyte, producing solid-state oxidation-reduction electrochemical reactions, which have been monitored by cyclic voltammetry and open circuit potential measurements in the presence of potassium as intercalating ion. The results show a behavior according to the Nernst equation as the potassium ion concentration varies, with a slope of 61.2 mV/dec. These experiments make it possible to access Gibbs free energy values for both transfers separately and replicate them for different insertion ions, such as Na+ and Li+.

Figure: (Left) Open circuit potential measurements; (center) mid-peak potential measurements; and (right) cyclic voltammetry for Ni[Fe(CN)6] in potassium media.

Figure 1
Probing Adsorption of Uranium Species at Electrochemical Interfaces in Support of Environmental Radiochemistry
Authors: Kersten Bethany , Akolkar Rohan , Duval Christine E
Published: November 2022

Special nuclear material, like enriched uranium and plutonium, can contaminate environmental soils and water because of weapons development and testing or improper waste storage. To remediate affected lands and design long-term waste storage solutions, it is crucial to understand uranium speciation in the environment which depends on its complexation, oxidation state, and associated adsorption mechanisms. These phenomena are complex and poorly understood because they depend on many variables including the environmental pH, water or soil composition, uranium concentration, and surface chemistry of the minerals or soils. In previous studies, the proposed mechanism for adsorption of the hexavalent uranyl species, UVIO2
2+, on metal-oxide surfaces follows these general steps: 1) adsorption of UVIO2
2+ on the mineral, followed by 2) reduction to UVIO2
2+ due to the coupled reaction of a redox active species within the mineral. To gain better mechanistic insight into coupled electron transfer and adsorption phenomena associated with uranyl species, we demonstrate here a novel technique to probe an electrochemical interface to detect adsorbed uranium species under reducing conditions. In this technique, we monitor the transient response of the electrode potential immediately after electrochemical reduction of UVIO2
2+ on a rotating disc electrode is halted. This potential relaxation rate, when analyzed, contains information on presence and coverage of surface adsorbed species. In combination with electrochemical quartz crystal microgravimetry (e-QCM), these experiments confirm the presence of an adsorbed layer of uranium ions during the reduction of UVIO2
2+. To simulate uranyl adsorption on minerals under environmental conditions, future work will aim to probe adsorption onto a metal-oxide film prepared on an e-QCM electrode under varying redox and pH conditions.
Detection of Pertechnetate Using Square Wave Anodic Stripping Voltammetry on Carbon Electrodes
Authors: Rakos Jason , Gonzalez Karen , Flaum Vivian , Weber Dustyn , Rusinek Cory
Published: November 2022

Technetium-99 (Tc-99) is a primary fission product of U-235, U-233, and Pu-239 and is a major constituent of radioactive waste. Tc-99 is commonly found as pertechnetate (TcO4
-), an anion that does not readily adsorb to natural sediment and is extremely mobile in environmental water systems. With concerns that radioactive waste may be leaking from sub-surface storage tanks and potentially reaching groundwater, developing detection methods for TcO4
- is important. Square wave anodic stripping voltammetry (SWASV) is a simple electrochemical technique that has yet to be investigated for pertechnetate due to the high potential required to form solid TcO2. In this work, we use SWASV with a variety of carbon electrodes to determine the optimal conditions for the detection of TcO4
- in a variety of solutions including acidic, basic and neutral pH. Carbon electrodes such as glassy carbon, boron-doped diamond, and nitrogen-doped tetrahedral amorphous carbon were examined. Carbon electrodes are ideal for the detection of pertechnetate due to their robust nature, low background current, and wide windows when compared to metal electrodes. Control studies included optimization of the deposition potential and time. In addition, calibration curves were created for each solution’s optimized parameters. Several analytical figures of merit such as the sensitivity, limit of detection, and limit of quantification were determined. This work expands upon the use of carbon electrodes for trace detection of environmentally relevant analytes.
(Digital Presentation) Environmentally Oriented Electrochemistry in the Teaching Laboratory
Authors: Ibanez Jorge G.
Published: November 2022

Electrochemistry has much to offer for a better understanding of natural electron exchange phenomena and multiple environmental remediation schemes. We have designed and tested several laboratory experiments to explore and demonstrate these functions in a teaching lab setting. These include: indirect electrolytic destruction of organic wastes, indirect H2S removal, electrocoagulation of oily wastewater, color removal of simulated wastewater by electrocoagulation-electroflotation, electrokinetic processing of soils, recovery of a soil metal pollutant and its extractant, production of disinfectants (ferrate and ozone), experimental transitions in a potential vs. pH (Pourbaix) diagram, electrolytically-generated activation of a metal surface for CO2 conversion, the indirect generation of colloidal sulfur to demonstrate Rayleigh scattering, a mini-solar cell, and the construction of a solar fuel cell. We have also generated experiments on non-electrodic electron transfer phenomena like simultaneous photocatalysis, removal of metal ions by cementation, destruction of pollutants by Fenton´s reagent, photoreduction of metal ions, production of disinfectants (ClO2, chloramines), water acidification by oxidation of mineral sulfides (acid mine drainage), and the oxidation of Fe(II) ions by molecular dioxygen.
(Invited) Prussian Blue Analogues as Battery Materials
Authors: Pasta Mauro
Published: November 2022

Prussian Blue Analogues (PBAs) have gathered renewed interest recently because of their unique electrochemical properties, several of which are highly desirable for energy storage1. These intriguing properties arise from the interaction of the crystal structure with inserting ions. The general electrochemical equation for the insertion of an alkali metal into a PBA is given by:

AxPJ[RK(CN)6]1−y · wH2O + A+ + e− → Ax+1PJ[RK−1(CN)6]1−y · wH2O

where A is an alkali-metal ion, and P and R are transition-metal ions octahedrally coordinated to six cyanide ligands via the nitrogen and carbon atom, respectively (Figure 1). The value y is the fraction of vacancies in the hexacyanoferrate complex ion (the primary lattice defect). Water can also be present, both as zeolitic and coordinated to deficiently bonded metal ions at vacancies.

Figure 1: Schematic representation of the crystal structure of PBAs. The green and dark-blue atoms are transition-metal ions at the R site and P site, respectively. Gray atoms are carbon and light-blue atoms are nitrogen.

In my talk, I will show how these exciting properties are linked to the structural diversity of PBAs2 and how their chemistry can be tuned to adapt their electrochemistry to a variety of energy storage applications3,4, with focus on K-ion batteries5–7.

References

Hurlbutt, K., Wheeler, S., Capone, I. & Pasta, M. Prussian Blue Analogs as Battery Materials. Joule vol. 2 1950–1960 (2018).

Cattermull, J., Pasta, M. & Goodwin, A. L. Structural complexity in Prussian blue analogues. Materials Horizons 8, 3178–3186 (2021).

Wheeler, S., Capone, I., Day, S., Tang, C. & Pasta, M. Low-Potential Prussian Blue Analogues for Sodium-Ion Batteries: Manganese Hexacyanochromate. Chemistry of Materials 31, 2619–2626 (2019).

Hurlbutt, K., Giustino, F., Pasta, M. & Volonakis, G. Electronic Structure and Electron-Transport Properties of Three Metal Hexacyanoferrates. Chemistry of Materials 33, 7067–7074 (2021).

Fiore, M. et al. Paving the Way toward Highly Efficient, High-Energy Potassium-Ion Batteries with Ionic Liquid Electrolytes. Chemistry of Materials 32, 7653–7661 (2020).

Dhir, S., Wheeler, S., Capone, I. & Pasta, M. Outlook on K-Ion Batteries. Chem 6, 2442–2460 (2020).

Cattermull, J. et al. Revealing the structural complexity of Prussian blue analogues: the case of K2Cu[Fe(CN)6]. ChemRxiv (2022) doi:10.26434/chemrxiv-2022-zr5nn.

Figure 1
(Invited) Switching Molecular Ionic Magnetism
Authors: Ren Shenqiang
Published: November 2022

Magneto-ionics of molecular based magnets, the ionic control of magnetism, promise ultralow-power sensor technologies, while the extent of reversible ion intercalation in turn is also the key state-of-charge feature in rechargeable battery electrodes. Here we report the reversible ion intercalation in molecular magnetic electrode, which simultaneously monitors the state of charge in battery and enables dynamic switching of its room-temperature magnetic transition. Microwave excited spin wave reveals lithiation degree in molecular-magnetic anode, enabling magneto-ionics towards the real-time monitoring of state of charge in rechargeable battery under a low magnetic field and radiofrequency. The structural vacancy and hydrogen-bonding networks in such molecular magneto-ionic compound enables the reversible lithiation and delithiation, which in turn, leads to a dynamical and reversible magnetization tunability.
Electrochemically Tunable Mixed Valence Conduction in Ruthenium Hexacyanoruthenate
Authors: Robinson Donald A , Foster Michael E , Bennett Christopher H , Bhandarkar Austin , Webster Elizabeth R. , Celebi Aleyna , Celebi Nisa , Fuller Elliot J. , Stavila Vitalie , Spataru Catalin D. , Ashby David S. , Marinella Matthew J. , Krishnakumar Raga , Allendorf Mark D. , Talin A. Alec
Published: November 2022

Reversible electrochemical doping of ruthenium hexacyanoruthenate, a type of Prussian blue analogue (PBA), enables the on-demand tuning of electronic conductivity by more than four orders of magnitude. Inkjet-printed electrochemical random access memory (ECRAM) devices based on Ru-PBA and lithium- or proton-conducting ionogel electrolytes exhibit excellent switching efficiency and long-term memory retention, important characteristics for analog artificial synapses in neuromorphic circuits. We also demonstrate excellent biocompatibility with live neurons and the use of Ru-PBA ECRAM devices to detect dopamine, promising first steps toward connecting artificial and biological neural networks. In-situ probing of metal-metal charge transfer by UV/Vis/NIR absorption spectroscopy reveals a switching mechanism whereby electrochemically tunable valence mixing between N-coordinated Ru sites controls the carrier concentration and mobility, as independently supported by both Marcus-Hush electron transfer theory and more conventional band structure predictions from DFT. The experimental agreement achieved by both theoretical approaches supports a general mechanistic picture that intramolecular charge transfer reactions, more commonly studied in polynuclear mixed valence small molecules, are central to electronic conductivity in extended coordination frameworks.
An Incremental Double Layer Capacitance of a Novel Ring-Disk Electrodes Array for Avidin/Strepavidin Sensing
Authors: Xie Qiuzhe , Lin Chih-Ting
Published: November 2022

Electric double layer (EDL) is established by ion redistribution at a solid-liquid interface. This ion redistribution electrically screens solid-surface charges and renders the interface to neutral. As a result, EDL is highly related to the surface potential, and a capacitor or constant phase element (CPE) is always employed to model the relationship between EDL and surface potential. According to this mechanism, diverse applications have been developed by controlling EDL via modulate potential fields or surface modifications. However, most of previous methods are sophisticated and hard to implemented as an in-situ monitoring method. To address this demand, we proposed a ring-disk electrode array (RDA) architecture to detect the changes of EDL capacitance between ring and disk electrode.

Based on the proposed architecture, the surface potential will change while the biomolecular is immobilized onto to the vertical nanogap. This effect is verified by immobilizing different charged functional groups and the correlation between the surface potential and incremental-capacitance variance is also demonstrated. Based on this effect, the application for Avidin detection is implemented. The detectable range for Avidin measurement is from 100 fg/ml to 1 ng/ml.

Based on this work, the incremental double-layer capacitance of a planar nanogap structure can provide a simple and reliable method for surface potential monitoring and can be used for different chemical and clinical examinations.

Figure 1
Computational Study on the Interaction of Iodide Electrolyte/Dye/TiO2 Interface in Dye-Sensitized Solar Cells
Authors: Hailu Yohannes Mulugeta , Jiang Jyh-Chiang
Published: November 2022

Abstract

Dye-sensitized solar cells (DSSCs) represent an emerging and promising candidate as a future renewable energy resource because of their potential low-cost fabrication cost, environmentally friendly, stability, and efficient solar energy conversion1. However, the intrinsic dye/iodide interaction with the dye on the semiconductor surface in understanding the DSSCs mechanism remains unclear2.In this work, three metal-free organic dyes based on D–π–A architecture were designed and computationally investigated for understanding the DSSCs mechanism and improving its efficiency2
-
4. The different donor groups were employed for the comparative study noted as D1Y, D2Y, and D3Y. This computational study mainly aims at determining the effect of the interaction of the iodide/triiodide with the dye on the semiconductor surface using the first-principles calculations (see scheme.1). We investigated the structural and electronic properties of these dyes when standing alone and being adsorbed on the oxide surface with the iodide electrolyte. Our studies revealed that the incorporation of a strong donor unit in D1Y and D

2

Y dyes in combination with iodide electrolytes on the TiO2 surface provides better adsorption and electronic properties in comparison to those from the dye alone on the TiO2 surface. Analysis of density of states (DOS) revealed that the dye with a strong electron-donating group, mainly D1Y and D2Y with an iodide electrolyte on the surface remarkably upshifts the Fermi energy, thereby improving the efficiency of the DSSCs by increasing the open-circuit voltage (Voc). These current findings provide a valuable hint for attaining a deeper understanding of the intrinsic interaction taking place at the electrolyte/dye/TiO2 interface.

References

O’Regan, B.; Grätzel, M.A Low-Cost High-Efficiency Solar Cell Based on Dye-Sensitized Colloidal TiO2 Films. Nature 1991, 353, 737– 740.

Hailu, M. and J.-C. Jiang Phys. Chem. Chem. Phys., 2020, 22, 26410-26418.

Hailu, W.-R. Shie, S. Nachimuthu and J.-C. Jiang, ACS Sustain. Chem. Eng., 2017, 5, 8619-8629.

Hailu, M. T. Nguyen and J.-C. Jiang, Phys. Chem. Chem. Phys., 2018, 20, 23564-23577.

Figure 1
Determination of Cr(VI) in Natural and Waste Waters Using Differential Pulse Polarography (US EPA SW-846 Method 7198)
Authors: Vyas Ritesh Navneetrai , Brankle Dane
Published: November 2022

The accurate determination of hexavalent chromium in environmental matrices such as natural and waste waters is crucial for the safety of both human and wildlife populations. The United States Environmental Protection Agency (U.S.EPA) has put forth SW-846, Method 7198, using differential pulse polarography for determination of Cr (VI) in both, the natural as well as waste waters. In Method 7198, the cathodic peak current resulting from the reduction of Cr (VI) to Cr (III) is measured and the concentration range for this method is listed as 10 ppb to 5 ppm Cr (VI). Using BASi Epsilon Potentiostat that is specifically made for measuring ultra-low current resolutions and a controlled growth mercury electrode (CGME) set-up, the US EPA method 7198 has been successfully optimized in this work for higher detection limits. It is observed that a detection limit of up to 7 ppb can be easily obtained by efficiently managing the interference of iron and Sulphur through a combination of various supporting electrolytes. This work may also become a valuable source of reference information on the behavior of wide variety of electrolytes and their control parameters needed to achieve extremely low detection limits.

Figure 1
Analytical Validation of Surface-Enhanced Raman Scattering Paper Lateral Flow Assays for Detection of Traumatic Brain Injury Biomarker
Authors: Tan Weirui , Hang Yingjie , Wu Nianqiang
Published: November 2022

Traumatic brain injury (TBI) can cause brain function loss injury-related deaths. Early TBI management is significant, but requires a timely, accurate, and sensitive assessment solution. However, current radiation- or imaging-based TBI diagnostic technologies are either less effective or time-consuming and expensive. Here, a surface-enhanced Raman scattering paper-based lateral flow strip (SERS-PLFS) is developed for rapid detection of neuron-specific enolase (NSE), a TBI biomarker in clinical blood plasma samples. The SERS-PLFS device is validated analytically with clinical human blood plasma samples. The performance metrics including accuracy, precision, reportable range, lower limit of quantification and upper limit of quantification, recovery, uncertainty, selectivity, robustness, are assessed using statistical methods. The validation results show that the SERS-PLFS is reliable in measuring the NSE levels in TBI patients.
Efficient Sensor Calibration Via Machine Learning-Based Resampling Methods
Authors: Ding Alison , Wang Jiacheng , Hang Yingjie
Published: November 2022

It remains a challenge to accurately and precisely calibrate a sensor in an experimentally-efficient manner. The calibration task at hand is to quantify the functional relationship between the sensor’s response (denoted as y) and the target analyte concentration (denoted as x) based on laboratory experiments. In practical use, the sensor’s mathematical calibration model needs to be coupled with the device to make inference regarding the concentration of the analyte in an environment based on the observed sensor response. It is critical to provide a single-value estimate for the analyte concentration, as well as to quantify the uncertainty of the target estimate (i.e., to provide the possible range of the underlying concentration level).

However, classic statistical methods are not able to provide valid inference on the target quantity of interest due to the following difficulties in sensor calibration. First, not only the typical forward modeling but also the inverse estimation is involved. The former refers to the generation of a calibration model functionally relating the analyte concentration to the sensor response (x→y) based on experimental data; The latter concerns the use of the calibration model in practical setting to obtain from the observed response the estimation of the unknown concentration (y→x). Second, the variability of the sensor responses tends to be heterogeneous as opposed to homogeneous, which is an assumption that classic statistical methods rely on.

In light of the above, a computational resampling method was adapted in this work to address the machine learning (ML)-based inference issues (i.e., the uncertainty quantification of the estimated analyte concentrations). Built on the inference capability, a two-stage experimental design procedure was developed to guide the efficient sampling of calibration data via laboratory experiments.

The ML-based inference and experimental design methods are integrated in the chemometric calibration procedure, which was applied on a simulated biosensor to demonstrate its efficiency over traditional methods. The sensor simulator is developed from the real experimental data for a paper-based lateral flow strip (PLFS) designed to measure in blood the diagnosis biomarkers for traumatic brain injury. PLFS is finding increasing applications in detection of various diseases in point-of-care testing settings.

Figure 1
Electrochemically Driven Yarn and Textile Actuators
Authors: Jager Edwin W.H. , Mehraeen Shayan , Melling Daniel , Martinez Jose , Backe Carin , Guo Li , Persson Nils-Krister , Vancaeyzeele Cédric , Nguyen Giao T. M. , Vidal Frédéric , Plesse Cédric
Published: November 2022

Conjugated polymers such as polypyrrole can be electrochemically oxidised and reduced. These redox reactions are accompanied by a flow of counter ions and solvent from the electrolyte into or out of the polymer matrix in order to maintain charge balance and osmotic pressure, resulting in an electrochemically induced volume change of the conjugated polymer. This volume change can be exploited to fabricate electrochemically driven actuators in various formats from bending bilayer microactuators to macroscopic textile actuators. Yarn and textile actuators are fabricated by coating commercially yarns and fabrics with the conjugated polymers. First a thin layer of PEDOT (poly(3,4-ethylenedioxythiophene)) is applied to make the yarns or fabrics electrically conductive. Thereafter the yarns/fabrics are coated with electromechanically active polypyrrole using electrochemical synthesis. Next the yarn or textile actuators can be actuated by applying the appropriate redox potentials. In order to achieve in-air actuation, the yarns or fabrics will be coated with novel ionogels (gelled semi-solid electrolytes), that function as the ion source/sink to drive the electrochemical reactions. Two of such ionogel coated yarns will be assembled forming the anode/cathode pair of the electrochemical circuit. Using advanced textile manufacturing such yarn actuators can be integrated into fabrics using knitting or weaving. The latest results of our textile actuators both operating in liquid electrolytes as in-air will be presented.

Fig. 1 A textile actuator with 4 inlay-knitted, in-air operating yarn actuators.

Figure 1
Well Array Microelectrode Electrochemical Sensor for High Sensitivity Cytokine Detection
Authors: Ilhamsyah Rizky , Hesketh Peter J. , Xu Jie , Guise Nicholas , Hayden Harley T. , Young Katherine T. , Ledford Keri , Robertson Wesley D.
Published: November 2022

Introduction

The activity of cytokines in the human body can be associated with certain diseases such as cancer, autoimmune, and infectious disease [1]. Recent studies found that it was possible to non-invasively detect certain cytokines such as Il6 through human saliva and sweat [2]. However, detection of cytokine in such bodily fluid poses a challenge due to very low cytokine concentration, ranging from fg/ml to pg/ml. Thus, signal amplification is necessary to achieve high sensitivity in cytokine detection. In this study, we propose a microfabricated electrochemical sensor with array of platinum micro-well as working electrode (Figure 1a and b). The charge transfer current density is compared to commonly used interdigitated electrode configuration (Figure 1c). A COMSOL model was developed to analytically compare charge transfer current for both electrode type. The electrodes were then compared experimentally through square wave voltammetry measurement.

Method

The microelectrode chips consist of platinum electrode and silicon nitride as insulation layer was fabricated using standard microfabrication techniques. The well array electrode consists of 1024 (32x32) array of 50 μm diameter well (counter electrode) and 2 μm ledge width for ring working electrode. The interdigitated electrode has 30 μm width and 1000 μm length with 10 parallel fingers. Square wave voltammetry measurement was carried using 20 mM Potassium Ferricyanide/ Ferrocyanide as redox probe, dissolved in 1x PBS and Ag/AgCl used as a reference electrode. Scanning range was set between 0 to 0.5 V with 5 mV step size, 25 mV pulse amplitude, and scanning 10 Hz frequency.

Results and Conclusions

Based on experimental results the well microelectrode configuration has 187% higher current density compared to its interdigitated electrode counterpart. The low current amplitude issue of well microelectrode is solved by having an array of 1024 well microelectrode (32x32) which amplify the signal from nanoampere to microampere scale.

References

[1] Monastero, R. N., & Pentyala, S. (2017). Cytokines as Biomarkers and Their Respective Clinical Cutoff Levels. International Journal of Inflammation, 2017, 1–11. doi:10.1155/2017/4309485

[2] Dutta, N., Lillehoj, P. B., Estrela, P., & Dutta, G. (2021). Electrochemical Biosensors for Cytokine Profiling: Recent Advancements and Possibilities in the Near Future. Biosensors, 11(3), 94. https://doi.org/10.3390/bios11030094

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Li6BaLa2Ta2O12 solid State Probe for Molten Alloys
Authors: Lujan Enric Lujan , Nel-lo Marc , Hinojo Antonio , Colominas Sergi , Abella Jordi
Published: November 2022

Nowadays, most of the energy consumption depends on carbon-based sources such as petroleum, natural gas and coal. If the current trend of CO2 emissions continues, the increment in the global average temperature will exceed 2oC (by 2050). Therefore, there is a need to develop new energy sources to reduce the environmental footprint. In this frame, nuclear fusion appears as a carbon-free alternative that perfectly fits in this sustainable transition. Future fusion reactors are expected to use deuterium and tritium as fuel. On the one hand, deuterium is a stable isotope that can be obtained from water. On the other hand, tritium is a radioactive isotope with a relatively short half-life (12.3 years) and must be generated in the reactor itself. For this purpose, it is suggested that lithium will react with high energy neutrons to produce this hydrogen isotope.

6Li + n → 4He + 3H + 4.8MeV

This nuclear reaction will take place in the tritium breeding modules. Molten Pb-Li alloy, in its eutectic composition, is considered the main breeding candidate. According to reaction (1), lithium will be consumed. Therefore, to maintain the eutectic composition, it is crucial to control both the concentration and the dosage of lithium. As future nuclear reactors will deal with extreme operational conditions, sensors based on solid-state electrolytes are a promising tool to monitor this lithium content.

In the present work, potentiometric sensors to measure Li concentration in molten Sn-Li alloys were constructed. These alloys will be used as a first step before Pb-Li assays. For that, Li6BaLa2Ta2O12 (LBLTO) solid-state electrolyte was synthesized and sintered as a pellet. EIS measurements were performed to evaluate the ionic conductivity of the sintered pellets at temperatures from 30 to 300ºC. These pellets were sealed in alumina tubes using a glass binder for sensor construction. On the one hand, Sn-Li alloys with different lithium contents (from 3at%Li up to 10at%Li) were used in the working electrode. On the other hand, a 3at%Li Sn-Li alloy was considered as the reference electrode. Potentiometric measurements were performed at different temperatures. Correlation curves of the recorded potentials versus the Li activity were in good agreement with the Nernst equation.
Understanding Changes of Both Faradaic and Nonfaradaic Currents with Temperature in DNA Monolayer-Based Sensors on Gold Electrodes
Authors: Mazumder A Z M Mainul Islam , Gurukandure Asanka , Kurian Amanda Siyanka Nellimale , Somasundaram Subramaniam , Easley Christopher John
Published: November 2022

Electrochemical sensors are well studied for detecting DNA, RNA, small molecules, inorganic ions, etc. Using the latest DNA-based sensors, a change in the location of a redox reporter attached to an electrode-bound nucleic acid gives rise to faradaic current changes, which can be monitored by square wave voltammetry (SWV) and used for sensing of various analytes. However, the nonfaradaic current generated along with the faradaic current has often been viewed as a limiting factor in sensor performance and either subtracted or ignored. Nonfaradaic current can be suppressed somewhat by surface blocking and reduced electrode surface area, and our group recently introduced a differential potentiostat (DiffStat) that provided efficient, in-hardware subtraction. On the other hand, removal of nonfaradaic current may lead to loss of important information embedded within. Moreover, a change in temperature can affect both faradaic and nonfaradaic currents by altering the movement of DNA strands and other ions present in the solution. Usually, faradaic current is proportional to the temperature. However, temperature-dependent changes in nonfaradaic current have not been well studied in DNA monolayer-based sensors. In this study, the changes in both faradaic and nonfaradaic currents were monitored in an electrochemical DNA hybridization assay. A thiolated DNA (thio-DNA) monolayer was assembled onto gold electrodes, and current was measured at different square wave frequencies (1 to 1000 Hz). The DNA analyte and the methylene blue tagged DNA (MB-DNA) were hybridized with the thio-DNA separately to compare the signals. Using an in-house built Peltier controller, the effects of temperature were monitored during operation of an analyte-induced proximity assay with SWV readout. In-house written MATLAB code was developed to automatically analyze each set of raw SWV data. Within this code, a polynomial baseline was calculated in the vicinity of the redox potential of MB-DNA (around -200 mV) to allow faradaic and nonfaradaic currents to be separated, post assay. Two-dimensional heatmaps were generated to study the variation of these currents with both temperature and square wave frequency. The faradaic current increased up to a certain temperature and then decreased due to dissociation (or melting) of the DNA from the surface. The nonfaradaic current, on the other hand, increased with temperature in a viscosity-dependent manner and also increased with the square wave frequencies as expected from a capacitive, single exponential time decay. Current changes exhibited by the DNA sensors upon analyte binding and temperature fluctuation suggested that both faradaic and nonfaradaic signals could be used for multidimensional analysis of sensor responses in the future.

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Nanocomposite Electrodes for Detection of Hexavalent Chromium
Authors: Lam Quang , Mutueke Joel , Elkholy Mohammed , Pham Duy , Aphale Ashish
Published: November 2022

Metal cations, when present in appropriate concentrations, serve an essential physiological function, however, their presence in larger concentrations has proven to be detrimental to human health. Modern industrial processes such as alloy treatment, coatings, and leather pigmentation, often result in the release of the heavy metal cations, causing adverse biological and ecological consequences. Amongst many, hexavalent chromium (Cr6+) is a major concern because of its carcinogenic properties. Therefore, it is imperative to develop a sophisticated technique for the early detection of Cr present in aqueous solutions. Numerous methods use techniques such as mechanical, optical, spectroscopic, and electrochemical for the detection of contaminants in aqueous solutions. Electrochemistry driven sensors have shown promise due to their possibility of miniaturization and low-cost. However, early and trace detection of such contaminants remains a challenge. Recently, atomically thin allotropes of carbon such as graphene or graphene oxide have been used to fabricate ultra-responsive and selective sensor platforms, owing to its excellent electrical conductivity, high surface area for functionalization, and physicochemical stability. In this work, we examine the use of electrically conducting polymer and atomically thin carbon materials as electrodes for the development of electrochemical sensors. Nanocomposite electrode films have been synthesized, and its performance as a function of number of cycles of deposition were analyzed. A capacitive microcomb sensor device has been fabricated, and the device performance using electrochemical, chemical, and morphological tests on electrodes as a function of deposition and electrolyte solutions will be highlighted. A fundamental understanding of reaction kinetics and identification of the rate-limiting steps will lead a path forward for developing robust sensors.
A CNN Regression Approach for Real-Time Estimation of Dielectrophoretic Force
Authors: Ajala Sunday , Muraleedharan Jalajamony Harikrishnan Muraleedharan , Fernandez Renny Edwin
Published: November 2022

This research presents a supervised learning framework with a Convolutional Neural Network (CNN) to precisely quantify dielectrophoretic force () in microfluidic devices using a regression approach. As opposed to using a classification paradigm in our prior work, here we recast the estimation task as a regression problem. Micrographs of pearl-chain arrangement in a DEP sensing device were processed using a using modified CNN architectures of AlexNet, ResNet-50, MobileNetV2, and GoogLeNet in order to predict the induced on yeast cells and polystyrene microbeads. Micrographs obtained from our dielectrophoresis (DEP) experiments with varied input voltages were preprocessed and used in building these deep regression models. prediction accuracy of the models was tested for using Mean Absolute Error (MAE), Mean Absolute Relative (MRE), Mean Squared Error (MSE), R-squared, and Root Mean Square Error (RMSE) as evaluation metrics. The results from the experiments show that the performance of our regression models had better prediction accuracy and generalization ability when compared to our classification models. ResNet-50 with RMSPROP gave the best performance, with a validation RMSE of 0.0918 on yeast cells while AlexNet with ADAM optimizer gave the best performance, with a validation RMSE of 0.1745 on microbeads. This provides a baseline for further studies in the application of deep learning and dielectrophoresis for DEP force estimation.

Figure 1