Journal articles on the topic 'Cationic redox probe'
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1
Kushner, Douglas, Adlai Katzenberg, Xiaoyan Luo, and Ahmet Kusoglu. "Cationic Ionomer Thin Films for Alkaline Electrochemical Energy Conversion." ECS Meeting Abstracts MA2022-02, no. 41 (October 9, 2022): 1519. http://dx.doi.org/10.1149/ma2022-02411519mtgabs.
Abstract:
Ionomers are used as the solid-electrolyte in many electrochemical energy conversion technologies where they offer many functionalities such as ion conduction, electrical insulation, and water transport. These ionomers are found as nanometer-thick electrolyte thin films within the catalyst layers of fuel cells, electrolyzers, and hydrogen-based redox flow batteries where electrochemical reactions take place. The ionomer performance and durability are strongly related to their properties governed by a myriad of parameters such as chemical structure, water uptake, and morphology, all of which are stimulated differently by the external environment. Typically, the ionomer consists of the same ion-conducting polymer used as the electrode separator but exhibit disparate properties from the bulk membrane when nanometer thickness coatings are confined to a hard substrate (as in a catalyst layer), where the behavior is influenced by the ionomer affinity with the air and hard interfaces. Two motifs of ionomers exist, one as an acidic polymer (e.g. Nafion) and the alternative, and less studied, alkaline polymer (e.g. Sustainion). This talk will focus on filling in the gaps between the disparate properties of alkaline ionomers in the thin film motif that have been extensively studied for acidic ionomers. Aspects such as different backbones (e.g. perfluorinated, aliphatic, aromatic) and side chains (e.g. length, functional group) are explored in X-ray scattering, hydration, and transport measurements. Small-angle X-ray scattering is used to probe the morphology of these different polymer thin-films. Quartz crystal microbalance and spectroscopic ellipsometry under different states of humidity are used to probe hydration and free volume. The resulting correlations provide insights on not only how different polymer respond to the confined environment but how chemistry can be tuned to boost performance in alkaline electrochemical energy devices.
2
Huang, Zhongnan, Xuan Luo, Fei Yan, and Bo Zhou. "Homogeneous Electrochemical Aptasensor for Sensitive Detection of Zearalenone Using Nanocomposite Probe and Silica Nanochannel Film." Molecules 28, no. 21 (October 24, 2023): 7241. http://dx.doi.org/10.3390/molecules28217241.
Abstract:
Developing rapid and efficient analytical methods is of great importance for food safety Herein, we present a novel homogeneous electrochemical aptasensor for ultrasensitive quantitative determination of zearalenone (ZEN) based on a nanocomposite probe and silica nanochannel film. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV–Vis characterization techniques confirm that graphene oxide (GO) bears an aromatic conjugated structure, along with hydroxyl and carboxyl groups, facilitating the subsequent adsorption of cationic redox hexa-ammine-ruthenium (III) (Ru(NH3)63+) and anionic ZEN aptamer, to form a Ru(NH3)63+–ZEN aptamer–GO nanocomposite probe in a homogeneous solution. Vertically-ordered mesoporous silica films (VMSF) bearing silanol groups can be simply grown on the solid indium tin oxide (ITO) electrode surface and enable the selective preconcentration of Ru(NH3)63+, eventually leading to signal amplification. Since the detachment of Ru(NH3)63+ from the GO surface by the recognized ZEN aptamer in the presence of ZEN, more free Ru(NH3)63+ is released in solution and produces enhanced redox signals at the VMSF modified ITO electrode, allowing quantitative detection of ZEN. On the basis of the above sensing strategy, the proposed homogeneity, due to the assistance of graphene, as well as of the signal amplification and anti-fouling effects of VMSF, accurate analysis of ZEN can be realized in maize and Chinese chestnut samples.
3
Zhang, Tongtong, Shuai Xu, Xingyu Lin, Jiyang Liu, and Kai Wang. "Label-Free Electrochemical Aptasensor Based on the Vertically-Aligned Mesoporous Silica Films for Determination of Aflatoxin B1." Biosensors 13, no. 6 (June 16, 2023): 661. http://dx.doi.org/10.3390/bios13060661.
Abstract:
Herein we report a highly specific electrochemical aptasenseor for AFB1 determination based on AFB1-controlled diffusion of redox probe (Ru(NH3)63+) through nanochannels of AFB1-specific aptamer functionalized VMSF. A high density of silanol groups on the inner surface confers VMSF with cationic permselectivity, enabling electrostatic preconcentration of Ru(NH3)63+ and producing amplified electrochemical signals. Upon the addition of AFB1, the specific interaction between the aptamer and AFB1 occurs and generates steric hindrance effect on the access of Ru(NH3)63+, finally resulting in the reduced electrochemical responses and allowing the quantitative determination of AFB1. The proposed electrochemical aptasensor shows excellent detection performance in the range of 3 pg/mL to 3 μg/mL with a low detection limit of 2.3 pg/mL for AFB1 detection. Practical analysis of AFB1 in peanut and corn samples is also accomplished with satisfactory results by our fabricated electrochemical aptasensor.
4
Yan, Zhengzheng, Shiyue Zhang, Jiyang Liu, and Jun Xing. "Homogeneous Electrochemical Aptamer Sensor Based on Two-Dimensional Nanocomposite Probe and Nanochannel Modified Electrode for Sensitive Detection of Carcinoembryonic Antigen." Molecules 28, no. 13 (July 3, 2023): 5186. http://dx.doi.org/10.3390/molecules28135186.
Abstract:
A rapid and convenient homogeneous aptamer sensor with high sensitivity is highly desirable for the electrochemical detection of tumor biomarkers. In this work, a homogeneous electrochemical aptamer sensor is demonstrated based on a two-dimensional (2D) nanocomposite probe and nanochannel modified electrode, which can realize sensitive detection of carcinoembryonic antigen (CEA). Using π-π stacking and electrostatic interaction, CEA aptamer (Apt) and cationic redox probe (hexaammineruthenium(III), Ru(NH3)63+) are co-loaded on graphite oxide (GO), leading to a 2D nanocomposite probe (Ru(NH3)63+/Apt@GO). Vertically ordered mesoporous silica-nanochannel film (VMSF) is easily grown on the supporting indium tin oxide (ITO) electrode (VMSF/ITO) using the electrochemical assisted self-assembly (EASA) method within 10 s. The ultrasmall nanochannels of VMSF exhibits electrostatic enrichment towards Ru(NH3)63+ and size exclusion towards 2D material. When CEA is added in the Ru(NH3)63+/Apt@GO solution, DNA aptamer recognizes and binds to CEA and Ru(NH3)63+ releases to the solution, which can be enriched and detected by VMSF/ITO electrodes. Based on this mechanism, CEA can be an electrochemical detection ranging from 60 fg/mL to 100 ng/mL with a limit of detection (LOD) of 14 fg/mL. Detection of CEA in human serum is also realized. The constructed homogeneous detection system does not require the fixation of a recognitive aptamer on the electrode surface or magnetic separation before detection, demonstrating potential applications in rapid, convenient and sensitive electrochemical sensing of tumor biomarkers.
5
Florea, Ciprian, Andra Mihaela Onas, Andreea Madalina Pandele, Matei Raicopol, and Luisa Pilan. "Controlled Surface Functionalization Using Aryldiazonium Salts for the Development of Aptasensing Platforms." ECS Meeting Abstracts MA2023-02, no. 62 (December 22, 2023): 2946. http://dx.doi.org/10.1149/ma2023-02622946mtgabs.
Abstract:
It is well known that both the aptamer surface density and surface chemistry can have a strong influence on the analytical performance of aptasensors based on target-induced conformational changes1. In this context, we report here an improved protocol for obtaining aptasensing platforms which allows fine-tuning the DNA aptamer surface coverage. First, glassy carbon substrates were functionalized with ethynylphenyl groups through the electrochemical reduction of silyl-protected ethynylphenyl diazonium tetrafluoroborates followed by deprotection with tetrabutylammonium fluoride2. The successful removal of the protecting groups (triisopropylsilyl-, triphenylsilyl- and tris(biphen-4-yl)silyl-) was confirmed by X-ray photoelectron spectroscopy and cyclic voltammetry in the presence of Fe(CN)6 3-/4- as soluble redox probe. Following “click” post-modification with suitable derivatization reagents, the surface coverage with ethynylphenyl groups was assessed using complementary techniques such as XPS, cyclic voltammetry and chronocoulometry. For example, the F/C surface ratio of substrates derivatized with 1-(2,2,2-trifluoroethoxy)-6-azidohexane provided an indication of the functionalization degree, and the integration of Fc/Fc+ voltammetric peaks for substrates modified with N-(6-azidohexyl)ferrocenecarboxamide allowed a quantitative determination of the surface coverage. Both techniques showed a good correlation between the protective group size and the surface coverage with alkyne groups. Likewise, we observed a similar trend for substrates derivatized with azide-modified oligonucleotides, where the surface packing density was determined based on the chronocoulometric response of Ru(NH3)6 3+, a cationic redox probe which binds with the negatively charged phosphate groups from the oligonucleotide backbone. As proof of concept, we further developed an electrochemical molecular beacon aptasensor employing a ferrocene-labeled quinine aptamer. We demonstrate that the aptamer surface density, and ultimately the analytical performance of molecular beacon aptasensors, can be effectively fine-tuned by employing silyl protecting groups of different sizes. Acknowledgements This work was supported by a grant from the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020-2474, within PNCDI III. References Onaş, A. M., Dascălu, C., Raicopol, M. D. & Pilan, L. Critical Design Factors for Electrochemical Aptasensors Based on Target-Induced Conformational Changes: The Case of Small-Molecule Targets. Biosensors 12, (2022). Leroux, Y. R., Fei, H., Noël, J.-M. M., Roux, C. & Hapiot, P. Efficient covalent modification of a carbon surface: Use of a silyl protecting group to form an active monolayer. J. Am. Chem. Soc. 132, 14039–14041 (2010).
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Mozhzhukhina, Nataliia, Aleksandar Matic, Gilles Moehl, Lucia Perez Ramirez, Jean-Pascal Rueff, Stephanie Belin, Antonella Iadecola, Quentin Jacket, and Sandrine Lyonnard. "Understanding LiNiO2 Electronic Structure and Redox Mechanism by Raman and X-Ray Techniques." ECS Meeting Abstracts MA2023-02, no. 2 (December 22, 2023): 227. http://dx.doi.org/10.1149/ma2023-022227mtgabs.
Abstract:
LiNiO2 (LNO) is considered a very promising and high energy density alternative to Co-containing Li-ion battery cathodes. It is also the benchmarked cathode material of the European BIGMAP project, which aim is to combine advance operando characterization, computational modelling and artificial intelligence in order to accelerate the research and development of new generation batteries. However, the material suffers from several degradation issues resulting in fading cell performance. In particular, the presence of highly reactive Ni4+ species at the electrode/electrolyte interface1, Ni dissolution from the cathode leading to the loss of active material 2, and O2 release at high voltage are the major drawbacks precluding commercial applications. A recent in situ study1 has shown that O2 release compromises the structural stability and triggers reactions with ethylene carbonate (EC), prompting CO2evolution3,4. In parallel, solid state physics community is also largely interested into LiNiO2 in the framework of a larger investigation around the electronic and atomic structure of nickelates, in particular rare-earth nickelates. This interest rises from the fact that there is still no consensus on the atomic/electronic structure of LiNiO2, while different descriptions exist in literature. Local probe techniques demonstrate the distortion of NiO6 octahedra, and there are two on-going theories for explaining the presence of this distortion: (i) Ni3+ (t2g6 eg1) Jahn-Teller (JT) distortion, (ii) 2 Ni3+ → Ni2+ + Ni4+ bond disproportionation (BD)5. Surprisingly, the local order distortion does not result in the long-range distortion, the mechanism behind this phenomenon is not completely understood. In this contribution we present a detailed study of LNO cathode material by operando Raman and X-ray absorption spectroscopy (XAS) at the Ni K-edge, ex situ X-ray emission spectroscopy (XES) and resonant Inelastic X-ray scattering (RIXS). Distinguishing between JT and BD models is challenging, and therefore NaNiO2 reference is used, which is isoelectronic material to LiNiO2, and is known to feature long-range JT distortion. While XAS is widely established technique to probe local structure and transition metal oxidation state, RIXS is useful for assessing d-d transitions and bond disproportionation. Operando Raman spectroscopy is an excellent tool for studying phase transitions in Li-ion battery cathodes and is therefore complementary to the employed X-ray techniques6. It provides information on two characteristic for layered oxides crystalline phonon modes A1g and Eg, and sheds light on both short-range order and cationic/anionic redox. The penetration depth is estimated as top few hundred nanometers of around five micrometres sized secondary particle, therefore near-surface area is probed. The results show a complex behaviour of band positions and intensities during cycling (figure 1), corresponding to four phases transformations. Notably the peaks intensities increase considerably, while the widths are decreased, which is evidence of increased order upon material delithiation, and is in agreement with the Extended X-ray Absorption Fine Structure (EXAFS). Raman is also used to evaluate the contribution of anionic redox, since all the reduced oxygen species (superoxide, peroxide and molecular oxygen) have well-known Raman-active modes. To conclude, we demonstrate how a combination of multiple vibrational and X-rays based spectroscopies provides a better understanding of both LNO ground state electronic structure and redox mechanism. This increased fundamental understanding will stimulate the design of better strategies for prevention of the material degradation and improved cycle retention. References: de Biasi, L. et al. Phase Transformation Behavior and Stability of LiNiO2 Cathode Material for Li-Ion Batteries Obtained from In Situ Gas Analysis and Operando X-Ray Diffraction. ChemSusChem 12, 2240–2250 (2019). Klein, S. et al. Exploiting the Degradation Mechanism of NCM523 Graphite Lithium-Ion Full Cells Operated at High Voltage. ChemSusChem 14, 595–613 (2021). Jung, R., Metzger, M., Maglia, F., Stinner, C. & Gasteiger, H. A. Chemical versus Electrochemical Electrolyte Oxidation on NMC111, NMC622, NMC811, LNMO, and Conductive Carbon. J Phys Chem Lett 8, 4820–4825 (2017). Freiberg, A. T. S., Roos, M. K., Wandt, J., de Vivie-Riedle, R. & Gasteiger, H. A. Singlet Oxygen Reactivity with Carbonate Solvents Used for Li-Ion Battery Electrolytes. J Phys Chem A 122, 8828–8839 (2018). Chen, H., Freeman, C. L. & Harding, J. H. Charge disproportionation and Jahn-Teller distortion in LiNiO${}_{2}$ and NaNiO${}_{2}$: A density functional theory study. Phys Rev B 84, 85108 (2011). Flores, E., Mozhzhukhina, N., Aschauer, U. & Berg, E. J. Operando Monitoring the Insulator–Metal Transition of LiCoO 2 . ACS Appl Mater Interfaces 13, 22540–22548 (2021). Figure 1
7
Malecka, Kamila, Shalini Menon, Gopal Palla, Krishnapillai Girish Kumar, Mathias Daniels, Wim Dehaen, Hanna Radecka, and Jerzy Radecki. "Redox-Active Monolayers Self-Assembled on Gold Electrodes—Effect of Their Structures on Electrochemical Parameters and DNA Sensing Ability." Molecules 25, no. 3 (January 30, 2020): 607. http://dx.doi.org/10.3390/molecules25030607.
Abstract:
The background: The monolayers self-assembled on the gold electrode incorporated transition metal complexes can act both as receptor (“host” molecules) immobilization sites, as well as transducer for interface recognitions of “guest” molecules present in the aqueous solutions. Their electrochemical parameters influencing the sensing properties strongly depend on the transition metal complex structures. The objectives: The electrochemical characterization of the symmetric terpyridine–M2+–terpyridine and asymmetric dipyrromethene–M2+–terpyridine complexes modified with ssDNA probe covalently attached to the gold electrodes and exploring their ssDNA sensing ability were the main aims of the research presented. The methods: Two transition metal cations have been selected: Cu2+ and Co2+ for creation of redox-active monolayers. The electron transfer coefficients indicating the reversibility and electron transfer rate constant measuring kinetic of redox reactions have been determined for all SAMs studied using: Cyclic Voltammetry, Osteryoung Square-Wave Voltammetry, and Differential Pulse Voltammetry. All redox-active platforms have been applied for immobilization of ssDNA probe. Next, their sensing properties towards complementary DNA target have been explored electrochemically. The results: All SAMs studied were stable displaying quasi-reversible redox activity. The linear relationships between cathodic and anodic current vs. san rate were obtained for both symmetric and asymmetric SAMs incorporating Co2+ and Cu2+, indicating that oxidized and reduced redox sites are adsorbed on the electrode surface. The ssDNA sensing ability were observed in the fM concentration range. The low responses towards non-complementary ssDNA sequences provided evidences for sensors good selectivity. The conclusions: All redox-active SAMs modified with a ssDNA probe were suitable for sensing of ssDNA target, with very good sensitivity in fM range and very good selectivity. The detection limits obtained for SAMs incorporating Cu2+, both symmetric and asymmetric, were better in comparison to SAMs incorporating Co2+. Thus, selection of the right transition metal cation has stronger influence on ssDNA sensing ability, than complex structures.
8
Basnig, Deomila, Neus Vilá, Grégoire Herzog, and Alain Walcarius. "Voltammetric behaviour of cationic redox probes at mesoporous silica film electrodes." Journal of Electroanalytical Chemistry 872 (September 2020): 113993. http://dx.doi.org/10.1016/j.jelechem.2020.113993.
9
Steen, William A., Kavita M. Jeerage, and Daniel T. Schwartz. "Raman Spectroscopy of Redox Activity in Cathodically Electrodeposited Nickel Hexacyanoferrate Thin Films." Applied Spectroscopy 56, no. 8 (August 2002): 1021–29. http://dx.doi.org/10.1366/000370202760249756.
Abstract:
The intercalation of cations into electrodeposited nickel hexacyanoferrate (NiHCF) depends on the stoichiometry and oxidation state of the material. To better understand this material's performance as a cation separation matrix, the oxidation state needs to be measured independently from the stoichiometry, regardless of the particular intercalated cation. Reported is the use of Raman spectroscopy to quantify the absolute oxidation state of NiHCF thin films. Raman spectroscopy probes NiHCF's cyanide bonds, which are sensitive to the oxidation state of the matrix. The oxidation state is controlled via potentiostatic experiments in electrolytes containing Na+, K+, and Cs+ (NO3− is the common anion). Principal component analysis (PCA) on the Raman spectra shows that more than 90% of the spectral variance is captured by one principal component, with a score value shown to be directly related to the oxidation state of the film. A universal, predictive regression model was developed using these score values as the dependent variables and Raman spectra as the independent variables. The results were confirmed with electrochemistry and energy dispersive X-ray spectroscopy.
10
Raouafi, Noureddine, Janet Bahri, Rihab Sahli, and Khaled Boujlel. "Redox-responsive probes for selective chelation of bivalent cations." QScience Connect, no. 2012 (August 2012): 8. http://dx.doi.org/10.5339/connect.2012.8.
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MacInnes, Molly M., Zachary R. Jones, Bo Li, Nickolas H. Anderson, Enrique R. Batista, Ida M. DiMucci, Cecilia Eiroa-Lledo, et al. "Using molten salts to probe outer-coordination sphere effects on lanthanide(iii)/(ii) electron-transfer reactions." Dalton Transactions 50, no. 43 (2021): 15696–710. http://dx.doi.org/10.1039/d1dt02708e.
Abstract:
Molten salt matrices were used to evaluate outer-coordination sphere effects on lanthanide redox chemistry. Results were rationalized by correlating the polarization power of the outer-sphere cation with shifts in the Ln3+/Ln2+ reduction potentials.
12
Dai, Kehua, Jinpeng Wu, Zengqing Zhuo, Qinghao Li, Shawn Sallis, Jing Mao, Guo Ai, et al. "High Reversibility of Lattice Oxygen Redox Quantified by Direct Bulk Probes of Both Anionic and Cationic Redox Reactions." Joule 3, no. 2 (February 2019): 518–41. http://dx.doi.org/10.1016/j.joule.2018.11.014.
13
Marchini, Edoardo, Stefano Caramori, Rita Boaretto, Vito Cristino, Roberto Argazzi, Alessandro Niorettini, and Carlo Alberto Bignozzi. "Self-Assembled Multinuclear Complexes for Cobalt(II/III) Mediated Sensitized Solar Cells." Applied Sciences 11, no. 6 (March 19, 2021): 2769. http://dx.doi.org/10.3390/app11062769.
Abstract:
In this work, we designed a tetranuclear self-assembled dye 4 (2Z907-Ag+-(Ru(TMAM))) exploiting a combination of the antenna effect and positively-charged groups designed to repel the oxidized form of cationic cobalt redox mediators, in order to reduce recombination and increase the efficiency of dye sensitized solar cells (DSSCs). Charge transfer and excited dynamics were probed by photoelectrochemical and photophysical measurements. The sensitized cell performance, recorded with a [Co(bpy)3]3+/2+ redox mediator and PEDOT counter electrode, showed an improvement when passing from Z907 to the multinuclear systems. The enhancement of the efficiency compared to Z907 resulted mainly from a superior steric and electrostatic shielding determined by the simultaneous presence of long alkyl chains and quaternary ammonia ion units in the architecture of 4.
14
McDaniel, Jenny K., Khalil Bdeir, Douglas B. Cines, and X. Long Zheng. "Synthetic Partially Reduced Human Neutrophil Peptide (HNP)-1 Inhibits Platelet Adhesion and Aggregation on Von Willebrand Factor-Collagen Surfaces Under Arterial Shear Stress through a Disulfide Bond Reduction Mechanism." Blood 128, no. 22 (December 2, 2016): 3722. http://dx.doi.org/10.1182/blood.v128.22.3722.3722.
Abstract:
Abstract Background: Human neutrophil peptides (HNPs) are small cationic proteins primarily released from activated and degranulated neutrophils. HNPs have antimicrobial activity against diverse bacteria, viruses, fungi, and parasites. Additionally, HNPs exhibit prothrombotic properties by enhancing platelet aggregation and fibrin formation and by inhibiting proteolytic cleavage of von Willebrand factor (VWF) by ADAMTS13. However, the role of HNPs in thrombus formation under more physiological conditions (i.e. under flow) has not been determined. Objective: To investigate the effects of HNPs on platelet adhesion/aggregation on VWF/collagen surfaces under arterial shears. Design/Method: Whole blood was obtained from C57/BL6 wild type and Adamts13-/-mice, anticoagulated with a potent thrombin inhibitor D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK) and prostaglandin-E1 (PGE1), and platelets were labeled with FITC anti-mouse CD41 IgG. After incubation with varying concentrations of native HNPs and synthetic partially reduced HNP1 (sHNP1) for 30 minutes, the whole blood samples were perfused through a fibrillar collagen-coated surface in a microfluidic system at 100 dyne/cm² for 180 seconds. The rate and extent of accumulation of fluorescein-labeled platelets were determined under an inverted fluorescent microscope at 4-second intervals. The images were analyzed off-line with Montage to evaluate the area of platelet coverage over time. This process was repeated with the addition of N-ethylmaleimide (NEM) alone or NEM-treated sHNP1 to the samples to probe the effect of free cysteine residues. In addition, samples of native HNPs and sHNP1 incubated with NEM were analyzed via LC-mass spectrometry for NEM incorporation. Results: Purified native HNPs at final concentrations of 15 μM and 30 μM exhibited no or little effect on the adhesion and aggregation of murine platelets on VWF/collagen surfaces under arterial shears (100 dyne/cm2). Surprisingly, sHNP1 at the same concentrations (15 and 30 μM) dramatically reduced the rate and surface coverage of platelets from WT (Fig. 1A) and, more profoundly, from Adamts13-/- mice (Fig. 1B) on VWF/collagen surfaces under the same conditions. This inhibitory activity of sHNP1 was abolished upon pretreatment with NEM, which reacts with free thiols (-SH) (not shown). Aliphatic HNP1 with all 6 cysteine residues chemically modified also did not inhibit the adhesion and aggregation of murine platelets on VWF/collagen surfaces under shear (not shown). Analysis of samples by LC-mass spectrometry confirmed the NEM-labeling of free thiols present in sHNP1, but not in native HNPs. Conclusion: These results suggest that high concentrations of locally released native HNPs may be required to inhibit ADAMTS13 activity in vivo. However, the findings from this study indicate that HNPs differentially affect thrombus formation depending on how its redox state is modified by its biological milieu. Somewhat unexpectedly, synthetic and partially reduced HNP1 may be a potent antithrombotic agent by reducing platelet interactions with VWF under arterial shear via a disulfide bond reduction mechanism. Disclosures Zheng: Alexion: Research Funding; Ablynx: Consultancy.
15
Xu, Jiahe, Johna Leddy, and Carol Korzeniewski. "Cyclic Voltammetry as a Probe of Selective Ion Transport within Layered, Electrode-Supported Ion-Exchange Membrane Materials." Journal of The Electrochemical Society 169, no. 2 (February 1, 2022): 026520. http://dx.doi.org/10.1149/1945-7111/ac51fd.
Abstract:
Cyclic voltammetry was applied to investigate the permselective properties of electrode-supported ion-exchange polymer films intended for use in future molecular-scale spectroscopic studies of bipolar membranes. The ability of thin ionomer film assemblies to exclude mobile ions charged similarly to the polymer (co-ions) and accumulate ions charged opposite to the polymer (counterions) was scrutinized through use of the diffusible redox probe molecules [Ru(NH3)6]3+ and [IrCl6]2−. With the anion exchange membrane (AEM) phase supported on a carbon disk electrode, bipolar junctions formed by addition of a cation exchange membrane (CEM) overlayer demonstrated high selectivity toward redox ion extraction and exclusion. For junctions formed using a Fumion® AEM phase and a Nafion® overlayer, [IrCl6]2− ions exchanged into Fumion® prior to Nafion® overcoating remained entrapped and the Fumion® excluded [Ru(NH3)6]3+ ions for durability testing periods of more than 20 h under conditions of interest for eventual in situ spectral measurements. Experiments with the Sustainion® anion exchange ionomer uncovered evidence for [IrCl6]2− ion coordination to pendant imidazolium groups on the polymer. A cyclic voltammetric method for estimation of the effective diffusion coefficient and equilibrium extraction constant for redox active probe ions within inert, uniform density electrode-supported thin films was applied to examine charge transport mechanisms.
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Asefifeyzabadi, Narges, Torrey E. Holland, Poopalasingam Sivakumar, Saikat Talapatra, Ishani M. Senanayake, Boyd M. Goodson, and Mohtashim H. Shamsi. "Sequence-Independent DNA Adsorption on Few-Layered Oxygen-Functionalized Graphene Electrodes: An Electrochemical Study for Biosensing Application." Biosensors 11, no. 8 (August 14, 2021): 273. http://dx.doi.org/10.3390/bios11080273.
Abstract:
DNA is strongly adsorbed on oxidized graphene surfaces in the presence of divalent cations. Here, we studied the effect of DNA adsorption on electrochemical charge transfer at few-layered, oxygen-functionalized graphene (GOx) electrodes. DNA adsorption on the inkjet-printed GOx electrodes caused amplified current response from ferro/ferricyanide redox probe at concentration range 1 aM–10 nM in differential pulse voltammetry. We studied a number of variables that may affect the current response of the interface: sequence type, conformation, concentration, length, and ionic strength. Later, we showed a proof-of-concept DNA biosensing application, which is free from chemical immobilization of the probe and sensitive at attomolar concentration regime. We propose that GOx electrodes promise a low-cost solution to fabricate a highly sensitive platform for label-free and chemisorption-free DNA biosensing.
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Morozov, Anatolii V., Ivan A. Moiseev, Aleksandra A. Savina, and Artem M. Abakumov. "Impact of TM-O Bonding Covalency on the Structure and Performance of Li-Rich Layered Oxide Positive Electrodes for Li-Ion Batteries." ECS Meeting Abstracts MA2022-01, no. 2 (July 7, 2022): 340. http://dx.doi.org/10.1149/ma2022-012340mtgabs.
Abstract:
The application of positive electrode (cathode) materials with anionic redox activity is hoped to improve the energy density of future Li-ion batteries, and thus facilitate the mileage issue in rapidly growing electric transport industry. Such positive expectations are dictated by promising application potential of the Li4/3-xNi2+ xMn4+ 2/3-xCo3+ xO2 layered oxides demonstrating outstanding reversible discharge capacity exceeding 250 mAh/g and specific energy density of > 1000 Wh/kg. Such outstanding values are the result of joint participance of cationic (Ni2+→Ni3+→Ni4+, Co3+→Co4+) redox transitions and processes of O2 n-/2O2- units formation in charge compensation mechanism upon Li (de)intercalation. Nevertheless, oxygen redox chemistry in battery materials is a «double-edged sword», since it`s associated with practical drawbacks like sluggish kinetics, voltage hysteresis, voltage fade and safety worries alongside greatly improved energy density. At the same time, the exact nature of partially oxidized oxygen species is still raising intensive debates as well as the role of TM-O bonding in oxygen oxidation reversibility and interplay between anionic redox and accompanying bulk and local structure transformations and their accumulation during prolonged cycling. In our work, we probed the anionic redox properties as a function of electronic structure and chemical bonding substituting a small fraction of 3d-metals with Ru in a parent Li1.2Ni0.2Mn0.6O2 according to xLi2RuO3-(1-x)Li1.2Ni0.2Mn0.6O2 solid solution system (x is up to 0.1). This approach allowed us to gently tune the ratio between the contributions of the cationic and anionic redox whereas employing the same mixed Ni-Mn carbonate precursor excludes the impact of different sample morphology on the electrochemical behavior, providing a legitimate justification to attribute all the observed effects solely to crystal structure and TM-O bonding character. Both experimental results and theoretical calculations demonstrated that gradual increasing of Ru content drastically changes electrochemical behavior of the Li-rich layered oxides improving the reversibility of the oxygen redox thus suppressing irreversible oxygen oxidation at the first charge. In turn, diminished gaseous O2 evolution led to the retardation of “structural densification” as well as concomitant mitigation of Mn redox activity and changes in spatial distribution of the reduced Mn species. Moreover, despite the discharge voltage fade did not differ much for compounds with different Ru concentration, Ru doping surely decreased the charge voltage fade and, surprisingly, total discharge capacity likely due to inhibited Mn4+/3+/2+ redox activity in the Ru-doped compounds. In our report we will present the whole set of observations on xLi2RuO3-(1-x)Li1.2Ni0.2Mn0.6O2 model system aimed to trace the whole chain of events from increasing the covalency of the TM-O bond, suppressing irreversible oxygen oxidation and appearance of the reduced Mn species to retarding the structure densification in the Li-rich layered oxides.
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Zhang, Raymond, Timofey Averianov, and Ekaterina Pomerantseva. "Assembly of Two-Dimensional δ-V2O5-Ti3C2Tx Heterostructure Electrodes for Li-Ion Batteries." ECS Meeting Abstracts MA2022-02, no. 2 (October 9, 2022): 150. http://dx.doi.org/10.1149/ma2022-022150mtgabs.
Abstract:
The bilayered phase of vanadium oxide (δ-V2O5∙nH2O or BVO) synthesized via sol-gel synthesis method is an attractive candidate to be used as a cathode material for Li-ion batteries (LIBs) due to its expanded interlayer spacing, and high theoretical capacity. However, poor electrical conductivity and rapid capacity fade present challenges for achieving high-rate performance and good cycle life during cycling in LIBs. A viable solution to mitigating these drawbacks is to fabricate two-dimensional (2D) heterostructures comprised of vanadium oxide and an additional selected 2D material. Titanium carbide (Ti3C2Tx) MXenes are particularly of interest for their high electronic conductivity (103 S cm-1) and well developed delamination protocols. Herein, we present a wet-based approach for assembling BVO and MXene nanoflakes into 2D heterostructures in suspension. In this study, we first demonstrate a simple liquid phase exfoliation technique utilizing probe ultrasonication to exfoliate bulk -LixV2O5·nH2O (LVO). Previous experiments from our group showed the exfoliation technique in n-methyl-2-pyrrolidone, an organic solvent that is toxic, flammable, and resulted in low yield during exfoliation. Here, for the first time, we have successfully performed exfoliation of LVO in aqueous media and obtained few layered nanoflakes with high yield after centrifugation. Despite the partial solubility of vanadium oxide in water, these nanoflakes suspended in aqueous media maintained chemical stability and readily assembled into a free-standing film using vacuum filtration. The LVO nanoflake films have a two-dimensional (2D) layered morphology as confirmed by SEM and maintain the bilayered structure as confirmed by XRD. Due to the hydrated nature of LVO, we also highlight the importance of controlling interlayer water content with vacuum drying for achieving better cycling stability. The comparison of a 105°C and 200°C vacuum drying temperature and corresponding interlayer water content was carried out using XRD, TGA, and Raman spectroscopy characterization methods. The 200°C vacuum dried LVO nanoflake cathode achieved an initial ion storage capacity of 212 mAh g-1 which was 32.5% higher than the sample dried at 105°C. In addition, galvanostatic cycling experiments conducted for the 200°C vacuum dried LVO nanoflake cathode show there were significant improvements in capacity retention by ~35%, compared to the 105°C dried sample, after 100 cycles at a current density of 20 mA g-1. Subsequently, dispersions of LVO and Ti3C2Tx flakes in water were combined in different weight ratios of 9:1, 4:1, and 1:1 LVO to Ti3C2Tx. The heterostructure electrostatic assembly was facilitated by the introduction of a cationic species into the mixed suspensions. Resistivity measurements showed that heterostructure films achieved electronic conductivities as high as ~105 higher than pristine LVO. Through electrochemical testing, the 9:1 heterostructure cathodes delivered the highest ion storage capacity of 167 mAh g-1. At the cost of lower capacity (125.3 mAh g-1), the 4:1 heterostructures maintain a superior capacity retention of ~96% after 10 cycles. Furthermore, rate capability experiments for the 9:1 heterostructure cathodes demonstrate that the addition of 10 wt % Ti3C2Tx to LVO enables greater tolerance to high current densities with a capacity retention of ~90% after cycling through increasing current densities. In this work we also show that increased capacities can be acquired upon the extension of the potential window below 2V covering where Ti3C2Tx exhibits redox activity. These results demonstrate an environmentally friendly and safe approach to obtaining 2D LVO nanoflakes and offers pathways to constructing novel vanadium oxide based 2D heterostructures for improving electrochemical performance in energy storage devices.
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Sahli, Rihab, Janet Bahri, Issa Tapsoba, Khaled Boujlel, and Noureddine Raouafi. "Solvent Effects on the Electrochemical Behavior of TAPD-Based Redox-Responsive Probes for Cadmium(II)." International Journal of Electrochemistry 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/305721.
Abstract:
Two tetralkylated phenylenediamines (TAPD)1and2have been prepared by reductive alkylation ofpara-dimethylaminoaniline with furfural or thiophene 2-carboxaldehyde, respectively. Their chelation ability has been evaluated as electrochemical guest-responsive chemosensors for Cd(II) in acetonitrile (ACN), dimethylformamide (DMF), propylene carbonate (PC), and nitromethane (NM). The voltamperometric studies showed that these compounds are able to bind the Cd(II) cation with strong affinities except in DMF. The redox features of the chemosensors changed drastically when they are bounded to Cd(II) to undergo important anodic potential peak shifts comprised between ca. 500 and ca. 900 mV depending on the solvent. The addition of ∼4–10% molar triflic acid (TfOH) was found to be necessary to achieve rapidly the cation chelation which is slow without the acid. The electrochemical investigations suggested the formation of 1 : 2 stoichiometry complexes [Cd(L)2]2+. The results are discussed in terms of solvent effects as a competitive electron donating ligand to the cation. The reaction coupling efficiency (RCE) values were determined and were also found to be solvent-dependent.
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Uhrmacher, Michael, and Klaus-Peter Lieb. "Phase Transitions in Oxides Studied by Perturbed Angular Correlation Spectroscopy." Zeitschrift für Naturforschung A 55, no. 1-2 (February 1, 2000): 90–104. http://dx.doi.org/10.1515/zna-2000-1-217.
Abstract:
Radioactive atoms located on cation sites in oxide matrices can be used to monitor phase transitions by measuring the electric or magnetic hyperfine interactions by means of Perturbed Angular Correlations spectroscopy. The article illustrates three types of phase transitions studied with 111In tracers and their daughter nuclei 111Cd, namely magnetic, structural and REDOX phase transitions in binary and ternary polycrystalline or single-crystalline oxides. In this context, we also discuss the question of identifying the probes' lattice site(s), the scaling of the Electric Field Gradients in oxides, the influence of the (impurity) probes themselves on the phase transitions, and the occurrence and mechanisms of dynamic interactions. Recent results on 111In in pure and Li-doped In2S3 will also be presented.
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Wang, Junbo, David Stenzel, Raheleh Azmi, Saleem Najib, Kai Wang, Jaehoon Jeong, Abhishek Sarkar, et al. "Spinel to Rock-Salt Transformation in High Entropy Oxides with Li Incorporation." Electrochem 1, no. 1 (March 16, 2020): 60–74. http://dx.doi.org/10.3390/electrochem1010007.
Abstract:
High entropy oxides (HEOs) constitute a promising class of materials with possibly new and largely unexplored properties. The virtually infinite variety of compositions (multi-element approach) for a single-phase structure allows the tailoring of their physical properties and enables unprecedented materials design. Nevertheless, this level of versatility renders their characterization as well as the study of specific processes or reaction mechanisms challenging. In the present work, we report the structural and electrochemical behavior of different multi-cationic HEOs. Phase transformation from spinel to rock-salt was observed upon incorporation of monovalent Li+ ions, accompanied by partial oxidation of certain elements in the lattice. This transition was studied by X-ray diffraction, inductively coupled plasma-optical emission spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and attenuated total reflection infrared spectroscopy. In addition, the redox behavior was probed using cyclic voltammetry. Especially, the lithiated rock-salt structure HEOs were found to exhibit potential for usage as negative and positive electrode materials in rechargeable lithium-ion batteries.
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Dooryhee, Eric, Andrey Yakovenko, Jonathan Hanson, Sanjit Ghose, Jose Rodriguez, and Sanjaya Senanayake. "Tracking Cation Migration in Catalysts by Modulated Enhanced Powder Diffraction." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1175. http://dx.doi.org/10.1107/s205327331408824x.
Abstract:
Mixtures of Cu-Fe oxides are used for numerous industrial catalytic processes including the Water-gas shift reaction (WGS: CO + H2O -> CO2 + H2). In this work we measure the structural changes of CuFe2O4 under redox (oxidizing and reducing) and WGS reaction conditions. A key component associated with the catalytic properties of this material is the reversible transfer of Cu in and out of the spinel structure during the reaction. The WGS reaction is the most active when Cu is metallic and on the surface of the spinel which has become Fe3O4. The reversible nature of the Cu migration preserves the activity of the catalyst and protects the Cu species from deactivation. We investigate the cation migration process from the octahedral site inside the spinel to the surface as Cu metal, using modulation measurements that perturb the dynamic structural properties of the spinel structure in a time resolved manner. The experiments termed MED [1] involve the switching of co-reactants (i.e. CO -> O2 -> CO -> O2) so that the residence time of specific adsorbates can be controlled, thus we can probe directly the role of the reactant and the redox sensitivity in the migration of the Cu cation. We demonstrate how distinguishable this technique is from previous steady-state measurements. The powder patterns are averaged over several cycles of gas (CO/H2/O2) variations. Phase-sensitive detection is applied to demodulate the data, picking up structural changes which occur in phase with reactant in-flow variations. Oscillations of the diffracted signal can be observed at the stimulation frequency ω, but also at the harmonic 2ω. Therefore the Fourier analysis of the components provides selective access to partial diffraction contributions otherwise merged into one average diffraction signal. This work is supported by the BNL LDRD program and experiments were performed at the APS and at the NSLS.
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Yadav, Jaya, Sai Pranav Vanam, Baskar Senthilkumar, Penphitcha Amonpattaratkit, and Prabeer Barpanda. "Manganese-Based Tunnel and Layered Oxide Cathodes for Secondary Alkali-Ion Batteries." ECS Meeting Abstracts MA2023-02, no. 4 (December 22, 2023): 723. http://dx.doi.org/10.1149/ma2023-024723mtgabs.
Abstract:
Designing new cathode materials remains crucial in developing (post) Li-ion batteries. Mn-based oxide cathodes have received wide attention due to their sustainable nature, low cost, elemental abundance, structural diversity/polymorphism, and rich oxidation states (2+ to 7+), offering tunable redox potential [1]. Here, we have investigated different oxide-based cathode insertion compounds for secondary metal-ion batteries. i) We have demonstrated tunnel-type sodium insertion material Na44MnO2(NMO) as an intercalation host for Li-ion and K-ion batteries. The solution combustion synthesized Na0.44MnO2 assuming an orthorhombic structure (space group Pbam), exhibited rod-like morphology. After electrochemical ion exchange from NMO, we obtained Na0.11K0.27MnO2 (NKMO) and Na0.18Li0.51MnO2 (NLMO) cathodes for K-ion batteries and Li-ion batteries, respectively [2]. These new compositions, NKMO and NLMO, showed excellent cycling stability with capacities of ∼74 and 141 mAh g–1 (first cycle, C/20 current rate). The underlying mechanistic features concerning charge storage and structural modifications in these cathode compositions were probed by combining ex-situ structural, spectroscopy, and electrochemical tools [3]. ii) Using composite formation, we have tried to improve the P2-type layered material. Here, the stable Na7(Li1/18Mn1/18Ni3/18Fe2/18χ1/18)O2–xNa2MoO4 biphasic composite was synthesized using Mo doping. Overall, the redox chemistry was investigated using various spectroscopy techniques to prove the net capacity resulted from both cationic and anionic redox reactions [4]. Keywords: energy storage; batteries; cathode; manganese oxides; intercalation; doping References: [1] N. O. Vitoriano et al., T. Rojo, Energy Environ. Sci. 2017, 10 (5), 1051−1074. [2] K. Sada, B. Senthilkumar, P. Barpanda, Chem. Commun. 2017, 53 (61), 8588−8591. [3] S.P. Vanam et al., P. Barpanda, Inorg. Chem. 2022, 61 (9), 3959−3969. [4] S.P. Vanam, P. Barpanda, Electrochim. Acta. 2022, 431, 141122.
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Ozuguzel, Umut, Adelia Aquino, Shelley Minteer, and Carol Korzeniewski. "Tools to Simulate Resonance Raman Spectra for in-Situ Studies of Electron Transport Mediators and Bioelectrocatalysts." ECS Meeting Abstracts MA2023-02, no. 52 (December 22, 2023): 2498. http://dx.doi.org/10.1149/ma2023-02522498mtgabs.
Abstract:
Raman spectroscopy is widely applied as an in-situ probe of electrochemical processes. When the excitation light is resonant with an electronic transition, the detected signal can be enhanced by more than 1,000-fold. Resonance Raman (RR) spectroscopy has broad application in the study of common organic electron transport mediators (i.e., viologens, phenazines, photosynthetic pigments) and active sites of redox proteins (i.e., laccases, peroxidases, flavin-containing enzymes). To support investigations of bioelectrocatalytic membranes, we have been adapting RR spectroscopy to gain insights into the properties of immobilized redox mediators and biocatalyst active sites.1,2 Computational methods can be useful for guiding spectral interpretation. This poster reports on applications of recently advanced time-dependent density functional theory (TDDFT) codes that enable the simulation of RR spectra for small electron transport mediators (e.g., methyl viologen radical anion) and redox protein active site models (e.g., laccase T1 site mimics). The ORCA program suite3 was adapted. A series of Cu-centered compounds that model the T1 active site in laccases was studied along with the methyl viologen radical cation. The T1 site in laccases facilitates direct electron transport to an electrode and is a target for in-situ RR measurements. The reported work demonstrates careful selection of the functional (B3-LYP versus the long-range corrected hybrid exchange functional, ωB97X-D3) results in TDDFT-calculated electronic absorption and RR spectra that have features in excellent agreement with experiment. The results provide a foundation to build from in advancing models of small redox mediators and laccase catalytic active sites in support of sustainable technologies. Ozuguzel, U.; Aquino, A.J.A.; Nieman, R.; Minteer, S.D.; Korzeniewski, C. “Calculation of Resonance Raman Spectra and Excited State Properties for Blue Copper Protein Model Complexes” ACS Sustainable Chem. Eng. 2022, 10, 14614. Xu, J.; Koh, M.; Minteer, S. D.; Korzeniewski, C. “In Situ Confocal Raman Microscopy of Redox Polymer Films on Bulk Electrode Supports” ACS Measurement Science Au 2023 (DOI: 10.1021/acsmeasuresciau.2c00064). Neese, F.; Wennmohs, F.; Becker, U.; Riplinger, C. “ORCA Quantum Chemistry Program Package” J. Chem. Phys. 2020, 152, 224108.
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Zapata, Fabiola, Antonio Caballero, Pedro Molina, and Alberto Tarraga. "A Ferrocene-Quinoxaline Derivative as a Highly Selective Probe for Colorimetric and Redox Sensing of Toxic Mercury(II) Cations." Sensors 10, no. 12 (December 10, 2010): 11311–21. http://dx.doi.org/10.3390/s101211311.
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Hernández, Victor Agmo, and Fritz Scholz. "One redox probe (dmfc) can drive the transfer of anions and cations across the aqueous electrolyte∣ionic liquid interface." Electrochemistry Communications 8, no. 6 (June 2006): 967–72. http://dx.doi.org/10.1016/j.elecom.2006.04.002.
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Yu, Fabiao, Ping Song, Peng Li, Bingshuai Wang, and Keli Han. "Development of reversible fluorescence probes based on redox oxoammonium cation for hypobromous acid detection in living cells." Chemical Communications 48, no. 62 (2012): 7735. http://dx.doi.org/10.1039/c2cc33264g.
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Smida, Hassiba, Christine Thobie-Gautier, Mohammed Boujtita, and Estelle Lebegue. "(Digital Presentation) Electrochemical Single Impact Method for Electroactive Bacterial Detection Onto Carbon Ultramicroelectrode." ECS Meeting Abstracts MA2022-02, no. 52 (October 9, 2022): 1992. http://dx.doi.org/10.1149/ma2022-02521992mtgabs.
Abstract:
This work aims to design a high sensitivity and selectivity biosensor based on the electrochemistry of single impacts onto ultramicroelectrode (UME) to detect and identify various bacterial strains. The main objective is to establish a unique electrochemical signature for each bacterial cell through the individual impact event signal on the surface of the UME [1, 2]. First, we focus on the detection of well-known electroactive Gram-negative bacteria such as Shewanella oneidensis in order to be able to selectively detect these different single cells. In this case, the strategy currently used is to record a chronoamperometric curve in an aqueous potassium phosphate buffer (pH = 7.4) solution containing a redox probe at an UME polarized at the oxidation or reduction potential of the electrochemical active aqueous species and to observe a “current step” when one bacterium impacts the UME, corresponding to a “blocking effect” [3] (Figure A). The response signal expected from single bacterium collision may also be a “current spike” corresponding to either the own electrochemical activity of the bacterium toward the redox probe and the UME applied potential or a “bouncing effect” of the bacterium which does not stick onto UME surface (Figure B). In order to be able to identify the type of bacterial cell striking the UME surface, an adapted functionalization (covalent grafting via reduction of diazonium aryl salts) with appropriate affinity (bio)chemical species such as antibodies or aptamers could be performed. This strategy could confer to the UME surface a selectivity of the signal generated during single impacts. For example, the electro-grafting of diazo-pyridinium cations for microbial fuel cell electrodes showed to promote and improve the development of bacterial electroactive films [4]. [1] E. Lebègue, N. L. Costa, R. O. Louro, F. Barrière, J. Electrochem. Soc. 16 (2020) 105501 [2] A. T. Ronspees, S. N.Thorgaard, Electrochimica Acta. 278 (2018) 412-420 [3] G. Guanyue, W. Dengchao, B. Ricardo, Z. Jinfang, M. Michael V. Anal. Chem. 90 (2018) 12123−12130 [4] H. Smida, E. Lebègue, J-F. Bergamini, F. Barrière, C. Lagrost, Bioelectrochemistry. 120 (2018) 157-165 Figure 1
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Metzger, E., D. Langlet, E. Viollier, N. Koron, B. Riedel, M. Stachowitsch, J. Faganeli, M. Tharaud, E. Geslin, and F. Jorissen. "Artificially induced migration of redox layers in a coastal sediment from the Northern Adriatic." Biogeosciences Discussions 10, no. 7 (July 19, 2013): 12029–63. http://dx.doi.org/10.5194/bgd-10-12029-2013.
Abstract:
Abstract. Long term experimental studies suggest that, under anoxic transient conditions, redox fronts within the sediment shift upwards causing sequential rise and fall of benthic fluxes of reduced species (Mn(II), Fe(II) than S(−II)). Infaunal benthic organisms are associated to different redox fronts as micro-habitats and must be affected by such changes during natural hypoxia events. In order to document geochemical evolution of the sediment during prolonged anoxia in a realistic system, benthic chambers were deployed on the seafloor of the Northern Adriatic and sampled after 9, 30 and 315 days of incubation. Oxygen and sulfide were measured continuously in the early stages of the experiment (during 9 days). High-resolution porewater profiles were sampled by DET probes and redox sensitive species were analysed (alkalinity, SO42–, Mn2+, Fe2+). After 7 days, anoxia was reached within the chambers. Mn and Fe started diffusing towards the water column giving a rusty color to the seafloor. Infaunal species appeared at the surface. After 20 days, all macro-organisms were dead. Macro-organisms decomposition laying on the seafloor generated important production of sulfides within the chamber generating a downward flux of sulfide towards the sediment where sulfides were quickly oxidized by metallic oxides or precipitated as FeS. Sulfide was no more detectable in the water column and porewaters at the end of the experiment. Therefore, our results suggest that sulfide enrichment in the water column in coastal systems is strongly controlled by the biomass of benthic macrofauna and its decay during hypoxia while its residence time in water column is controlled by iron content (as solid oxides or as dissolved reduced cation) within the sediment, even without water circulation.
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Paulik, Matthew G., Paula A. Brooksby, Andrew D. Abell, and Alison J. Downard. "Grafting Aryl Diazonium Cations to Polycrystalline Gold: Insights into Film Structure Using Gold Oxide Reduction, Redox Probe Electrochemistry, and Contact Angle Behavior." Journal of Physical Chemistry C 111, no. 21 (May 2007): 7808–15. http://dx.doi.org/10.1021/jp0706578.
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Stokes, Thomas N., Geoffrey D. Bromiley, G. Diego Gatta, Nicola Rotiroti, Nicola J. Potts, and Kate Saunders. "Cation distribution and valence in synthetic Al–Mn–O and Fe–Mn–O spinels under varying conditions." Mineralogical Magazine 82, no. 4 (May 15, 2018): 975–92. http://dx.doi.org/10.1180/mgm.2018.109.
Abstract:
ABSTRACTThe spinel-group minerals, found in a range of igneous rocks, are resistant to weathering and can incorporate several multivalent elements, meaning they have the potential to provide insight into the redox conditions of parental magmas. Naturally occurring spinel can contain varying quantities of Mn, an element which occurs terrestrially and extra-terrestrially as Mn2+, Mn3+, Mn4+ and Mn5+. However, a lack of information on the effects of oxygen fugacity ($f_{{\rm O}_{\rm 2}}$) on: (1) Mn valence state and cation distribution; and (2) on spinel-melt partitioning means that the potential for a Mn-in-spinel oxy-barometer remains largely untested. Here, we use electron probe microanalysis, micro-focus X-ray Absorption Near Edge Structure (XANES) spectroscopy and single-crystal X-ray diffraction (SC-XRD) to investigate cation distribution and valence state in spinels in the Al–Mn–O and Fe–Mn–O systems synthesized at ambient pressure under varying $\hskip 2pt f_{{\rm O}_{\rm 2}}$ conditions. In contrast to previous studies, we find that the spectral resolution of the Mn K-edge XANES spectra is insufficient to provide quantitative data on Mn valence state and site occupancy, although it does verify that Mn is incorporated as both Mn2+ and Mn3+, distributed over tetrahedral and octahedral sites. Combination of data from XANES and SC-XRD refinements can, however, be used to model Mn, Al and Fe valence and site occupancy. It would be expected that Mn–Fe spinels have the potential to record $f_{{\rm O}_{\rm 2}}$ conditions in parental melts due to changes to the octahedral site under conditions that were more reducing. However, decoupling the effects of temperature and oxygen fugacity on the TFe3+–TMn2+ exchange in the Mn–Fe spinels remains challenging. In contrast, little variation is noted in Mn–Al spinels as a function of $\hskip 2pt f_{{\rm O}_{\rm 2}}$, implying that crystal chemistry and cation site geometry may significantly influence cation distribution, and by inference, crystal-melt partitioning, in spinel-group minerals.
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Metzger, E., D. Langlet, E. Viollier, N. Koron, B. Riedel, M. Stachowitsch, J. Faganeli, M. Tharaud, E. Geslin, and F. Jorissen. "Artificially induced migration of redox layers in a coastal sediment from the Northern Adriatic." Biogeosciences 11, no. 8 (April 22, 2014): 2211–24. http://dx.doi.org/10.5194/bg-11-2211-2014.
Abstract:
Abstract. Long-term experimental studies suggest that, under transient anoxic conditions, redox fronts within the sediment shift upwards, causing sequential rise and fall of benthic fluxes of reduced species (Mn(II), Fe(II) and S(-II)). Infaunal benthic organisms are associated with different redox fronts as micro-habitats and must be affected by such changes during natural hypoxia events. In order to document the geochemical evolution of the sediment during prolonged anoxia in the framework of an in situ experiment designed to mimic natural conditions, benthic chambers were deployed on the seafloor of the Northern Adriatic and sampled after 9, 30 and 315 days of incubation. Oxygen and sulfide were measured continuously in the early stages (9 days) of the experiment. High-resolution pore water profiles were sampled by DET probes and redox-sensitive species (S(VI), Mn(II) and Fe(II)) and alkalinity were measured. Starting oxygen saturation was about 80% within the chamber. After 7 days, anoxia was established in the bottom waters within the chambers. Mn(II) and Fe(II) started diffusing towards the anoxic water column until they reached the surficial sediment. Being reoxidized there, Mn and Fe reprecipitated, giving a rusty coloration to the seafloor. Infaunal species appeared at the sediment surface. After 20 days, all macro-organisms were dead. Decomposition of macro-organisms at the sediment–water interface generated S(-II) within the entire height of the chamber, leading to a downward flux of sulfides into the sediment, where they were quickly oxidized by metallic oxides or precipitated as FeS. S(-II) was below detection in the water column and pore waters at the end of the experiment. Our results suggest that S(-II) enrichment in the water column of coastal systems, which are episodically anoxic, is strongly controlled by the biomass of benthic macrofauna and its decay during anoxia, whereas its residence time in the water column is controlled by iron availability (as solid oxides or as dissolved reduced cations) within the sediment, even without water circulation.
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Cassidy, John F., Rafaela C. de Carvalho, and Anthony J. Betts. "Use of Inner/Outer Sphere Terminology in Electrochemistry—A Hexacyanoferrate II/III Case Study." Electrochem 4, no. 3 (July 11, 2023): 313–49. http://dx.doi.org/10.3390/electrochem4030022.
Abstract:
Salts of hexacyanoferrate II/III anions have been widely used as redox couple probe molecules to determine the characteristics of electrode surfaces. Examples include the assessment of electrocatalysts for energy applications and electrocatalysts for the detection of biological or chemical species, as well as the determination of electrochemically active surface areas. An examination of the electrochemical literature, based largely on cyclic voltammetric investigations, reveals a wide range of peak separation and/or heterogeneous electron transfer rate constants, classified sometimes as inner or outer sphere electron transfer processes. Originally developed for the mechanistic interpretation of inorganic transition metal compounds in solution, this terminology has since been extended to account for heterogeneous electron transfer occurring at electrodes. In the case of the hexacyanoferrate II/III anions, there can be a number of reasons why it sometimes behaves as an outer sphere probe and at other times displays inner sphere electron transfer characteristics. After examining some of the structural and chemical properties of the hexacyanoferrate II/III species, the methods used to determine such classifications are described. The most common method involves measuring peak-to-peak separation in a cyclic voltammogram to ascertain a heterogeneous rate constant, but it has inherent flaws. This paper reviews the reasons for the classification disparity, including the effects of various oxygen surface species, the influence of organic surface films, the nature of the cation counter-ion, surface adsorption and surface hydrophilicity/hydrophobicity. Other surface interactions may also take place, such as those occurring with Au corrosion or pH effects. These can impact the electrical double layer and thus may affect the electron transfer process. Consequently, it is recommended that hexacyanoferrate II/III should be considered a multi-sphere or alternatively a surface-sensitive electron transfer species.
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Soares, Rita B., Rita Manguinhas, João G. Costa, Nuno Saraiva, Nuno Gil, Rafael Rosell, Sérgio P. Camões, et al. "The Redox-Active Manganese(III) Porphyrin, MnTnBuOE-2-PyP5+, Impairs the Migration and Invasion of Non-Small Cell Lung Cancer Cells, Either Alone or Combined with Cisplatin." Cancers 15, no. 15 (July 27, 2023): 3814. http://dx.doi.org/10.3390/cancers15153814.
Abstract:
Manganese(III) porphyrin MnTnBuOE-2-PyP5+ (MnBuOE, BMX-001) is a third-generation redox-active cationic substituted pyridylporphyrin-based drug with a good safety/toxicity profile that has been studied in several types of cancer. It is currently in four phase I/II clinical trials on patients suffering from glioma, head and neck cancer, anal squamous cell carcinoma and multiple brain metastases. There is yet an insufficient understanding of the impact of MnBuOE on lung cancer. Therefore, this study aims to fill this gap by demonstrating the effects of MnBuOE on non-small cell lung cancer (NSCLC) A549 and H1975 cell lines. The cytotoxicity of MnBuOE alone or combined with cisplatin was evaluated by crystal violet (CV) and/or 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-Tetrazolium (MTS) reduction assays. Intracellular ROS levels were assessed using two fluorescent probes. Furthermore, the impact of MnBuOE alone or in combination with cisplatin on collective cell migration, individual chemotactic migration and chemoinvasion was assessed using the wound-healing and transwell assays. The expression of genes related to migration and invasion was assessed through RT-qPCR. While MnBuOE alone decreased H1975 cell viability at high concentrations, when combined with cisplatin it markedly reduced the viability of the more invasive H1975 cell line but not of A549 cell line. However, MnBuOE alone significantly decreased the migration of both cell lines. The anti-migratory effect was more pronounced when MnBuOE was combined with cisplatin. Finally, MnBuOE alone or combined with cisplatin significantly reduced cell invasion. MnBuOE alone or combined with cisplatin downregulated MMP2, MMP9, VIM, EGFR and VEGFA and upregulated CDH1 in both cell lines. Overall, our data demonstrate the anti-metastatic potential of MnBuOE for the treatment of NSCLC.
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Lin, Feng. "(Battery Division Early Career Award Sponsored by Neware Technology Limited) Design, Synthesis, and Characterization of Cathode Microstructures in Lithium Batteries." ECS Meeting Abstracts MA2022-02, no. 3 (October 9, 2022): 210. http://dx.doi.org/10.1149/ma2022-023210mtgabs.
Abstract:
The propagation of redox reactions governs the electrochemical properties of battery materials and their critical performance metrics in battery cells. The recent research progress, especially aided by advanced analytical techniques, has revealed that incomplete and heterogeneous redox reactions prevail in many electrode materials. Advanced high-capacity cathode materials are mostly polycrystalline materials that exhibit complex charge distribution (the valence state distribution of the redox-active cations) due to the presence of numerous constituting grains and grain boundaries. The redox reactions in individual grains typically do not proceed concurrently due to their distinct geometric locations in polycrystalline particles. As a result, these unsynchronized local redox events collectively induce heterogeneous and anisotropic charge distribution, building up intergranular and intragranular stress. Therefore, these polycrystalline materials may exhibit weak mechanical stability, leading to undesired chemomechanical breakdown during battery operation. Grain engineering in polycrystalline materials provides a large playground to modulate the materials properties beyond controlling the chemical composition, and electronic and crystal structures. In particular, the anisotropic ion-conducting pathways in layered oxides make the grain crystallographic orientation a critical factor in determining the modality of the redox reactions in these materials. This presentation will discuss our recent progress in the design, synthesis, and characterization of cathode microstructures in lithium batteries. First, we will discuss how the charge distribution is guided by grain crystallographic orientations in polycrystalline battery materials. We elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. While the holistic “surface-to-bulk” charge distribution prevails in polycrystalline particles, the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains. Compared to the randomly oriented grains, the radially aligned grains exhibit a lower cell polarization and higher capacity retention upon battery cycling. The radially aligned grains create less tortuous lithium-ion pathways, thus improving the charge homogeneity as statistically quantified from over 20 million nanodomains in polycrystalline particles. This study provides an improved understanding of the charge distribution and chemomechanical properties of polycrystalline battery materials. Second, we will discuss how the grain arrangement affects the thermal stability of polycrystalline cathode materials in rechargeable batteries. We performed a systematic in situ study on the Ni-rich polycrystalline cathode materials to investigate the fundamental degradation mechanism of charged cathodes at elevated temperatures, which is essential for tailoring material properties and improving performance. Using multiple microscopy, scattering, thermal, and electrochemical probes, we decoupled the major contributors to the thermal instability from intertwined factors. Based on our findings, the cathode grain microstructure has a forgotten yet important role in the thermal stability of polycrystalline rechargeable batteries. Oxygen release, as an important process during the thermal runaway, can be regulated through engineering grain arrangements. The grain arrangement can modulate the macroscopic crystallographic transformation pattern and oxygen diffusion length in layered cathodes to offer more possibilities for cathode material design and synthesis. Third, we will discuss our new understanding of particle behaviors in composite cathodes. We capture and quantify the particle motion during the solidification of battery electrodes and reveal the statistics of the dynamically evolving motion in the drying process, which has been challenging to resolve. We discover that the particle motion exhibits a strong dependence on its geometric location within a drying electrode. Our results also imply that the final electrode quality can be controlled by balancing the solvent evaporation rate and the particle mobility in the region close to the drying surface. We formulate a network evolution model to interpret the regulation and equilibration between electrochemical activity and mechanical damage of these particles. Through statistical analysis of thousands of particles using x-ray phase-contrast holotomography in a Ni-rich cathode, we found that the local network heterogeneity results in asynchronous activities in the early cycles, and subsequently the particle assemblies move toward a synchronous behavior. Our study pinpoints the chemomechanical behavior of individual particles and enables better designs of the conductive network to optimize the utility of all the particles during operation.
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Connelly, Neil G., Bernhard Metz, and A. Guy Orpen. "The stable radical cation [Mo2(µ-C8Me8)(η-C5H5)2]+: an intermediate in the redox activation of an alkyl C–H bond and a probe of metal–alkene bonding." J. Chem. Soc., Chem. Commun., no. 18 (1994): 2109–10. http://dx.doi.org/10.1039/c39940002109.
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Anderson, Lawrence O., Adrian Xiao Bin Yong, Elif Ertekin, and Nicola H. Perry. "Modifying Crystal Symmetry and B-O Charge Distribution to Tailor Chemical Expansion in Mixed Conducting Perovskites." ECS Meeting Abstracts MA2022-01, no. 37 (July 7, 2022): 1624. http://dx.doi.org/10.1149/ma2022-01371624mtgabs.
Abstract:
The exchange of ions between a lattice and the gaseous phase makes mixed conducting oxides ideal for a range of electrochemical applications. Altering oxygen ion concentration is accompanied by a change to electronic species concentrations, and this influences electrical, chemical, kinetic, and mechanical properties. The stability of electrochemical devices like fuel cells and batteries can heavily rely on the mechanical response to changes in chemical defect concentrations. Under both dynamic and steady-state operation of these devices, large volume strains and strain mismatch at interfaces can result in fracture, warping, and delamination that can cause performance degradation and/or failure. Strains between different materials are compared using the coefficient of chemical expansion (CCE), which normalizes the isothermal chemical strain by the change in defect concentration. Here, we advance the understanding of chemo-mechanical coupling through the study of PrGa0.9Mg0.1O3-δ and BaPr0.9Y0.1O3-δ by demonstrating CCEs 2-5x lower than any previously reported perovskite oxide1. Isothermal CCEs were evaluated with in situ, high temperature, and variable atmosphere x-ray diffraction and dilatometry for chemical strains, and with thermogravimetric analysis for stoichiometry changes. The experimental results show chemical strains to be significantly lower than predictions from simple empirical models that assume pseudo-cubic structures and full charge localization on multivalent cations, like Pr. To evaluate actual charge distribution, in situ impedance spectroscopy and density functional theory calculations were performed. The collaboration of experimental and computational work combines accurate and reliable material characterization with insights into atomic and electronic structures that are difficult to probe experimentally. Our results for the studied compositions indicate 2 primary factors that can be used to modify CCEs: 1) Altering the crystal structure away from the isotropic, cubic phase encourages anistropic expansion and lower CCEs in polycrystalline materials, and 2) Varying the distribution of charge along B-O bonds is shown to dramatically alter the CCE. While the first factor provides rather clear guidance to tailor expansion, we elaborate on the second by suggesting band structure design principles for near-zero redox-strain perovskites, and the benefit of locating holes partially or fully on oxygen is highlighted. These new findings add to the growing collection of crystal-chemical design rules for the rational tailoring of chemo-mechanical coupling in perovskite oxides. (1) Anderson, L. O.; Yong, A. X. Bin; Ertekin, E.; Perry, N. H. Toward Zero-Strain Mixed Conductors: Anomalously Low Redox Coefficients of Chemical Expansion in Praseodymium-Oxide Perovskites. Chem. Mater. 2021, 33 (21), 8378–8393. https://doi.org/10.1021/ACS.CHEMMATER.1C02739.
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Wu, Suozhu, and Bin Su. "7,7′,8,8′-Tetracyanoquinodimethane as a redox probe for studying cation transfer across the water/2-nitrophenyl octyl ether interface at three-phase junctions supported by carbon ink screen-printed electrodes." Journal of Electroanalytical Chemistry 656, no. 1-2 (June 2011): 237–42. http://dx.doi.org/10.1016/j.jelechem.2010.11.004.
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Quentel, Francois, Valentin Mirčeski, and Maurice L'Her. "Lutetium Bis(tetra-tert-butylphthalocyaninato): A Superior Redox Probe To Study the Transfer of Anions and Cations Across the Water|Nitrobenzene Interface by Means of Square-Wave Voltammetry at the Three-Phase Electrode." Journal of Physical Chemistry B 109, no. 3 (January 2005): 1262–67. http://dx.doi.org/10.1021/jp045914c.
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Hyk, Wojciech. "(Invited) Voltammetric Examination of Carbon Nanoelectrodes Under Mixed Diffusion - Migration Mass Transport Conditions." ECS Meeting Abstracts MA2023-01, no. 49 (August 28, 2023): 2555. http://dx.doi.org/10.1149/ma2023-01492555mtgabs.
Abstract:
In general, experiments carried out with nanoelectrodes are similar to those with microelectrodes. However, the extremely increased efficiency of the mass transport to nanoelectrodes results in steady-state current conditions in ultra-short times and high current densities. The transport of electroactive species to the working electrode surface is mainly realized by diffusion. The contribution of migration to the total mass transport is usually eliminated by shortening the thickness of the electrical double layer (EDL) achieved by the addition of supporting electrolyte excess. This simplifies the theoretical description of mass transport to pure diffusion but on the other hand, modifies physicochemical properties, including transport parameters of the analyzed environment. In systems containing a deficiency of supporting electrolyte, migration contributes to mass transport. The transport studies in these systems require the employment of small-sized electrodes (micro- / nanoelectrodes) and potentiostats capable of measuring ultralow currents. Migration introduces an additional variable (electrostatic potential) to the transport expressed by the Nernst-Planck equation. Under the low ionic strength conditions, the transport dynamics depends on the concentration profiles of a substrate, product, cations and anions of supporting electrolyte, and an uncompensated electrostatic potential gradient. In practice, the contribution of migration can be quantitatively related to the support ratio parameter (ξ), defined as the ratio of the concentrations of electroinactive charge carriers (i.e. not involved in the electrode reaction) to the concentration of the electrode reaction substrate. In terms of the ξ parameter, migration has a negligible effect on mass transport under the conditions of high values of the support ratio (ξ > 100). As the support ratio decreases (ξ < 1) the potential gradient occurs due to increased resistivity of the system and, consequently, the total mass transport is affected by the migrational contribution. The problem of diffusion-migration transport in voltammetric experiments involving microelectrodes was treated theoretically and the derived models allow one to predict the voltammograms for various types of electrode processes carried out under the conditions of various concentration of supporting electrolyte. The major factor complicating the theoretical description of mass transport induced by migration is the influence of an EDL. In the system containing a deficiency of supporting electrolyte, EDL may occupy a significant part of the diffusion layers of the substrate and the product of the electrode process. With the decrease of the electrode radius (below 100 nm), the EDL start to overlap with the diffusion layer and significantly affects the transport even in the system containing substantial concentrations of supporting electrolyte. To explore new research domains for nanoelectrodes, the procedures for the fabrication of nanoelectrodes of reproducible parameters and the theoretical description of the mass transport to nanoelectrodes under mixed diffusion-migration transport conditions have to be developed. The ultrasmall electrodes are highly susceptible to electrostatic mechanical and electrochemical damage, leading to the formation of recessed or protruding electrodes with altered current response, which is an additional impediment in the studies with their use. As a result of the damage causing recession, the electrodes lose their current response and give low feedback in their use as probes in scanning electrochemical microscopy (SECM). The damage caused by electrostatic discharging can be avoided by handling and storing the electrodes grounded together with objects in the vicinity. This work demonstrates the voltammetric behavior of the fabricated carbon nanoelectrodes in the presence and absence of supporting electrolyte. The ferrocene derivatives of various charges served as redox probes for the studies of diffusion-migration transport to nanoelectrodes. The obtained results are confronted to the theoretical predictions derived for microelectrodes. They revealed that migration of electroactive species to nanoelectrodes does not introduce significant changes to voltammetric signal as much as for bigger microelectrodes. Moreover, the elimination of supporting electrolyte in most cases led to the poor development of the voltammetric waves at nanoelectrodes. The possible reason may be related to the breakdown of the electroneutrality in the region adjacent to the nanoelectrode, since the electrical double layer for nanoelectrodes may occupy a significant fraction of the transport depletion layer. The uncertainty in the concentrations of ionic impurities (that determine the actual support ratio) in the layer adjacent to the electrode is another factor that may produce unpredictable and, to some extent, random voltammetric behavior of charged redox probes at nanoelectrodes in the absence of supporting electrolyte.
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Ozdogru, Bertan, and Omer Ozgur Özgür Capraz. "Driving Force behind the Amorphization in the Crystalline Cathode Structures during Alkali Metal Ion Intercalation for Electrochemical Energy Storage." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 453. http://dx.doi.org/10.1149/ma2022-024453mtgabs.
Abstract:
Development of cathode structures suitable for Na-ion and K-ion batteries is still one of the major challenges on the way to the design of next-generation alkali metal-ion batteries. Although Li, Na and K belong to the same alkali metal group with a single charge in their cation form, intercalation of Na+ and K+ ions in electrodes is difficult since ionic radii of Na+ (0.98 Å) and K+ (1.38 Å) are larger than that of Li+ (0.69Å). Intercalation of alkali metal ions results in volumetric expansions in the electrode structure. Even modest expansions in brittle cathodes can cause particle fracturing in a larger crystalline-size scale. Intercalation of larger ions can cause structural collapse and amorphization induced by continuous accumulation of strains and distortions. However, the lack of understanding behind the amorphization mechanisms in the crystalline electrodes upon ion intercalation materials hinders the development of electrode structures suitable for these large ions. In the first part of the talk, we will first report the utilization of in situ digital image correlation and in-operando X-ray diffraction (XRD) techniques to probe dynamic changes in the amorphous phase of iron phosphate during potassium intercalation1. A new experimental approach allows to monitor dynamic physical and structural changes in the amorphous phase of the electrodes. This method offers new insights to study mechanics of ion intercalation in the amorphous nanostructures. In the second part of the talk, we will discuss the electrochemical and mechanical response of the iron phosphate cathodes upon Li, Na and K ion intercalation. Strain evolution during Li and Na intercalation results in more linear dependence on the state of charge / discharge. However, strains generated in the electrode shows nonlinear behavior during insertion / extraction of K ions. Strain rate calculations showed that K ion intercalation results in a progressive increase in the strain rate, whereas Li and Na intercalation induce nearly constant strain rates2. Our results shows that strain rates are critical factor for the amorphization of the crystalline structure, rather than the absolute value of electrochemical strains. These observations provide a fundamental insight into the impact of alkali ions on the redox chemistry and associated chemomechanical deformations. Acknowledgement: This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (Award number DE-SC0021251). References: 1) B. Ozdogru et al, Nano Letters, 21, 18, 7579–7586, 2021. 2) B. Ozdogru et. al, Electrochemical Science Advances, e2100106, 2021.
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Romio, Martina, Yuri Surace, Nicolas Eshraghi, Benedikt Herzog, Bruno Eckmann, Damian Marlon Cupid, Johannes Hoffmann, and Marcus Jahn. "Advanced Investigation of the Electrolyte-Mg Anode Interphase for the Development of Mg-Ion Batteries." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 465. http://dx.doi.org/10.1149/ma2022-024465mtgabs.
Abstract:
Magnesium-ion batteries (MIBs) represent a promising chemistry to potentially substitute lithium-ion technologies in the e-mobility and stationary energy storage applications. This is due to the favourable properties of metallic Mg, such as: abundancy, non-toxic nature, high recycling rate1, low redox potential (-2.37 vs SHE), safety (smooth Mg2+ electrodeposition), as well as divalent character of Mg2+ cations which leads to higher theoretical volumetric capacity (3833 mAh/cm3) than Li (2046 mAh/cm3) and commercial graphite (760 mAh/cm3).2 However, the major obstacle in the further development of MIBs is the incompatibility of Mg metal anode with conventional electrolyte solutions, which are formed by mixing simple Mg-based salts (e.g Mg(TFSI)2, Mg(ClO4)2, etc.) and polar aprotic solvents (e.g. acetonitrile, carbonates, etc.). These solutions decompose at the surface of metallic Mg forming an electronic and ionic insulating layer, leading to the passivation of the Mg anode and poor performance of the overall cell. Conversely, organoborate (Mg-tetrakis(hexafluorosisopropyloxy)borate in monoglyme, MgBOR)3 or organoaluminate (1:2 AlCl3:PhMgCl in THF, APC)4 ethereal solutions are known to prevent the passivation of the Mg metal anode, allowing the reversible electrochemical Mg2+ electrodeposition onto its surface. Despite a great effort has been done in the development of MIB,5 very little is known about the formation, evolution and degradation of the solid electrolyte interphase (SEI) formed at the interface between metallic Mg and electrolyte. This work, therefore, aims to investigate the interactions between Mg metal and passivating (Mg(TFSI)2 in monoglyme:diglyme) and non-passivating (MgBOR and APC) electrolytes combining ex-situ and in-situ spectroscopic and microscopic techniques with electrochemical testing. The properties of the SEIs will be evaluated at different states of charge (ex-situ) and during cell cycling (in-situ). Raman, Fourier transformed infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies are used to identify the composition of the electrolyte interphases, as well as monitor their changes upon cell discharge-charge cycles. Scanning electron microscopy (SEM) is performed to analyse the interphase morphologies, whereas scanning microwave microscopy (SMM)6,7 locally probes the impedance of the SEI layer. Atomic force microscopy (AFM) is also employed to evaluate the roughness of the Mg metal electrodes. Cyclic voltammetry (CV) and galvanostatic cycling with potential limitation (GCPL) are carried out in order to determine the electrochemical performance of bare Mg metal or covered with SEI layers. Furthermore, electrochemical impedance spectroscopy (EIS) is employed to probe the Mg2+ diffusion coefficients through the SEI layers at different state of charge (e.g. open circuit voltage, etc.) and determine charge transfer evolution with cycling time of the Mg metal anode. As the first step, a successful polishing method was developed to remove the native oxide layer form the surface of Mg discs allowing to expose a bare Mg metal to the electrolyte solutions and to evaluate their interactions. The polishing method also enabled to perform SMM imaging of the Mg metal since a roughness between 1-2.5 µm was achieved. The Mg discs were then immersed in the electrolyte solutions and an initial deposition of interfacial species (few nanometre thickness) was observed by SEM when Mg(TFSI)2 in monoglyme:diglyme was used, whereas a smooth surface was detected with MgBOR and APC electrolytes. This resulted in different electrochemical behaviours. In fact, symmetric cells (Mg||Mg) with MgBOR electrolyte showed a significantly higher cycling stability (> 250 h) than those with Mg(TFSI)2 in monoglyme:diglyme solution. In addition, when the latter electrolyte was used, fluorinated by-products were identified by XPS. In order to study the SEI formation and growth further, in-situ spectroscopic techniques (e.g. Raman and SMM) were employed to establish a correlation between the chemical composition of the electrolyte, the voltage range of the electrochemical tests and cycling time. In particular, the SMM method was applied to MIB technologies for the first time in this work. References I. R. P. United Nations Environment Programme, (available at https://wedocs.unep.org/20.500.11822/8702); J. Niu, Z. Zhang, D. Aurbach, Adv. Energy Mater., 2020, 10, 2000697; Z. Zhao-Karger, M. E. Gil Bardaji, O. Fuhr, M. Fichtner, J. Mater. Chem. A, 2017, 5, 10815–10820; D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature, 2000, 407, 724; R. Dominko, J. Bitenc, R. Berthelot, M. Gauthier, G. Pagot, V. Di Noto, J. Power Sources, 2020, 478, 229027; A. Buchter, J. Hoffmann, A. Delvallée, E. Brinciotti, D. Hapiuk, C. Licitra, K. Louarn, A. Arnoult, G. Almuneau, F. Piquemal, M. Zeier, F. Kienberger, Rev. Sci. Instrum., 2018, 89, 23704; J. Hoffmann, M. Wollensack, M. Zeier, J. Niegemann, H. Huber, F. Kienberger, in 2012 12th IEEE International Conference on Nanotechnology (IEEE-NANO), pp. 1–4.
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Walters, Lucy Jayne, Alex R. Neale, Richard J. Nichols, and Laurence J. Hardwick. "Operando Surface Enhanced Infrared Spectroscopic Investigations of Interfacial Restructuring and Oxygen Electrochemistry in Ionic Liquid Electrolytes for Metal-Air Batteries." ECS Meeting Abstracts MA2022-01, no. 4 (July 7, 2022): 569. http://dx.doi.org/10.1149/ma2022-014569mtgabs.
Abstract:
Alkali metal-oxygen (M-O2) chemistry has received significant research interest as a promising next-generation battery, but many challenges need addressing before the technology can become viable in practice. Key among these obstacles are the understanding and control of the mechanisms of the oxygen reduction and evolution reactions (ORR and OER), and the tendency for the electrolyte materials to degrade due to attack by reactive intermediates. As such, a greater understanding of the ORR/OER in M-O2 cells, and how these factors contribute to the poor reversibility on cycling, is required in order to develop stable electrolytes. Attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) is highly sensitive to the interfacial region and can probe sub-monolayer adsorbates and species within ca. 10 nm of the electrode surface, which makes it valuable for studying interfacial processes. Our group demonstrated the application of ATR-SEIRAS to identify ORR products in nonaqueous M-O2 batteries, wherein a ZnSe prism internal reflection element (IRE) was utilised to extend the measurement range down to ca. 700 cm-1.1 While ZnSe offers enhanced optical properties over some conventional IREs, the lower wavenumber cut-off means that the sub-700 cm-1 vibrational frequencies of some superoxide and peroxide species and intermediates generated during ORR/OER cannot be observed. Recently, a micromachined Si wafer IRE has been developed to extend the measurement range of ATR-SEIRAS to well below 700 cm-1.2 In this work, we report ATR-SEIRAS investigations into the O2 electrochemistry and the potential dependent interfacial restructuring of 1-methyl-1-propylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide ([Pyrr13][TFSI]) utilising a thin-layer Au electrode on the micromachined Si wafer IRE to extend the measurement range towards the far-IR region. While the potential-dependent restructuring of the IL/Au electrode interface has been investigated by ATR-SEIRAS previously,3 the optical transmission of the Si wafer IRE used here reveals previously unreported changes in the 1000–500 cm-1 spectral region (Figure 1). We also discuss here how the redox couple of dissolved O2 strongly alters the double-layer restructuring, and the associated activation energy barriers, in the IL electrolyte. The ORR in the IL electrolyte in the presence of Li+ or Na+ cations is also explored, wherein the identification of sub-700cm-1 (su)peroxy intermediates/products, critical to understanding the overall mechanisms, is made possible using the Si wafer IRE. References J. P. Vivek, N. G. Berry, J. Zou, R. J. Nichols, and L. J. Hardwick, J. Phys. Chem. C, 121, 19657–19667 (2017). T. A. Morhart, B. Unni, M. J. Lardner, and I. J. Burgess, Anal. Chem., 89, 11818–11824 (2017). K. Motobayashi, Y. Shibamura, and K. Ikeda, Electrochem. Commun., 100, 117–120 (2019). Figure 1. Operando ATR-SEIRAS measurements of [Pyrr13][TFSI] (at a thin-layer Au electrode) at 0.9 V vs reference spectra at -2.7 V (dark blue and dark red spectra) at a) 1500-900 cm-1 and b) 860-500 cm-1. The Si wafer IRE (red spectrum) allows detection of [TFSI]- peaks below 1000 cm-1, which are not visible using the Si prism (light blue spectrum) due to the poor IR transmission in this region. Wafer spectra intensities are multiplied by a factor of 2 and the grey trace is an ex situ ATR-FTIR spectrum of the bulk IL. Figure 1
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Cheng, Chen, Zengqing Zhuo, Shuyuan Chen, Xi Zhou, Cheng Yuan, Pan Zeng, Jinghua Guo, and Liang Zhang. "Cationic and Anionic Redox of Battery Cathodes Investigated by Advanced Synchrotron‐Based Mapping of Resonant Inelastic X‐ray Scattering." Advanced Functional Materials, April 18, 2024. http://dx.doi.org/10.1002/adfm.202403442.
Abstract:
AbstractRedox reaction builds the foundation stone for the energy density of rechargeable battery cathodes. Probing and understanding the redox reaction behavior is crucial, but also extremely formidable, which requires individual and reliable detection of cationic and anionic redox states. Fortunately, the recently developed ultra‐high‐efficiency mapping of resonant inelastic X‐ray scattering (mRIXS) has emerged as a powerful tool to probe the battery chemistry states. Here, the latest advances of employing advanced mRIXS is summarized to investigate the cationic and anionic redox mechanism of battery cathodes during electrochemical operation. Owing to the new dimension of information along the emission energy and high sensitivity to valence 3d states, 3d transition‐metal L‐edge (TM‐L) mRIXS can eliminate the lineshape distortion in conventional 3d TM‐L fluorescence X‐ray absorption spectra and investigate the cationic redox quantitatively. Moreover, O‐K mRIXS could fingerprint the intrinsic oxidized lattice oxygen states and quantify the oxygen redox (OR) reversibility, thus demystifying the controversy in traditional wisdom. In addition, different modification strategies coupled with underlying mechanisms for regulating the activity and reversibility of OR utilizing mRIXS are also summarized. This review provides valuable guidance for further exploration of underlying reaction mechanisms of battery cathodes by mRIXS, along with both technological and scientific improvements.
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Prevot, Vanessa, Souad Touati, and Christine Mousty. "Confined Growth of NiAl-Layered Double Hydroxide Nanoparticles Within Alginate Gel: Influence on Electrochemical Properties." Frontiers in Chemistry 8 (December 2, 2020). http://dx.doi.org/10.3389/fchem.2020.561975.
Abstract:
NiAl Layered Double Hydroxide (LDH) alginate bionanocomposites were synthesized by confined coprecipitation within alginate beads. The NiAl based bionanocomposites were prepared either by impregnation by divalent and trivalent metal cations of pre-formed calcium cross-linked alginate beads or by using the metal cations (Ni2+, Al3+) as crosslinking cationic agents for the biopolymer network. The impregnation step was systematically followed by a soaking in NaOH solution to induce the LDH coprecipitation. Powder x-ray diffraction (PXRD), infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX), thermogravimetry analysis (TGA), electron microscopies (SEM and TEM) confirmed the biotemplated coprecipitation of LDH nanoparticles ranging from 75 to 150 nm for both strategies. The drying of the LDH@alginate beads by supercritical CO2 drying process led to porous bionanocomposite aerogels when Ca2+ cross-linked alginate beads were used. Such confined preparation of NiAl LDH was extended to bionanocomposite films leading to similar results. The permeability and the electrochemical behavior of these NiAl@alginate bionanocomposites, as thin films coated on indium tin oxide (ITO) electrodes, were investigated by cyclic voltammetry, demonstrating an efficient diffusion of the K4Fe(CN)6 redox probe through the LDH@alginate based films and the improvement of the electrochemical accessibility of the Ni sites.
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Duan, Shengnan, Chiasa Uragami, Kota Horiuchi, Kazuki Hino, Xiao-Feng Wang, Shin-ichi Sasaki, Hitoshi Tamiaki, and Hideki Hashimoto. "Hydroquinone redox mediator enhances the photovoltaic performances of chlorophyll-based bio-inspired solar cells." Communications Chemistry 4, no. 1 (August 11, 2021). http://dx.doi.org/10.1038/s42004-021-00556-5.
Abstract:
AbstractChlorophyll (Chl) derivatives have recently been proposed as photoactive materials in next-generation bio-inspired solar cells, because of their natural abundance, environmental friendliness, excellent photoelectric performance, and biodegradability. However, the intrinsic excitation dynamics of Chl derivatives remain unclear. Here, we show sub-nanosecond pump–probe time-resolved absorption spectroscopy of Chl derivatives both in solution and solid film states. We observe the formation of triplet-excited states of Chl derivatives both in deoxygenated solutions and in film samples by adding all-trans-β-carotene as a triplet scavenger. In addition, radical species of the Chl derivatives in solution were identified by adding hydroquinone as a cation radical scavenger and/or anion radical donor. These radical species (either cations or anions) can become carriers in Chl-derivative-based solar cells. Remarkably, the introduction of hydroquinone to the film samples enhanced the carrier lifetimes and the power conversion efficiency of Chl-based solar cells by 20% (from pristine 1.29% to 1.55%). This enhancement is due to a charge recombination process of Chl-A+/Chl-D–, which is based on the natural Z-scheme process of photosynthesis.
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Wang, Chao, Yupei Li, Peiqi Qiao, Yifan Yang, zixiang zhou, Ruirui Teng, and Yichuang Xing. "Electrochemical Characterization of Salt-in-Water and Water-in-Salt Zinc Sulfate and Zinc Acetate Electrolytes." Journal of The Electrochemical Society, November 20, 2023. http://dx.doi.org/10.1149/1945-7111/ad0e47.
Abstract:
Abstract The electrochemical properties of Zn(OAc)2 or ZnSO4 with water at different concentrations are investigated. The electrochemical stability window follows Pt < Au < GCE electrodes, and expands with increasing concentration of electrolytes. The change in salt concentration does not significantly change the double layer capacitance, and the potential of zero charge of Pt, Au and GCE electrodes are estimated to be 0.25 - 0.35 VSCE, 0.05 VSCE, and –0.20 VSCE, respectively. Using hydroquinone as a redox probe, the redox electrochemistry, ion transport and electron transport kinetics in these electrolytes are studied. The apparent redox potential of hydroquinone increases with the electrolyte concentration, and the diffusion coefficient of hydroquinone in Zn(OAc)2 and ZnSO4 electrolytes decreases with the increase of electrolyte concentration. The electron transfer rate constant (k) between the electrode and hydroquinone in Zn(OAc)2 and ZnSO4 electrolytes ranges from 1.28 to 1.46 and 0.29 to 0.81 cm s-1, respectively. The lower k in ZnSO4 electrolytes is related to the lower solvent reorganization energy, the interaction of electroactive ions with water, and the interaction of electrolyte cations.
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Ghosh, Sneha, Ananta Hazra, Sibshankar Bari, Tiasha Dutta, Sushil Kumar Mandal, Pritam Ghosh, and Partha Roy. "Detection of the +3 Oxidation State of Metal Ions with the Aid of a Rhodamine‐Based Dye and Applications in Construction of Complex Logic Circuits and Living Cell Imaging." ChemistrySelect 9, no. 2 (January 9, 2024). http://dx.doi.org/10.1002/slct.202303245.
Abstract:
AbstractDetection of correct oxidation state of a metal ion is important to understand its speciation and redox properties. Some of rhodamine derivatives can identify Al3+, Cr3+ and Fe3+ as the trivalent cations. We have synthesized a rhodamine derivative, HL‐qui, from the reaction of N‐(rhodamine‐6G)lactam‐ethylenediamine with quinoline‐2‐carboxaldehyde for the colorimetric as well as fluorogenic detection of all of metal ions with +3 oxidation state such as Al3+, Cr3+, Fe3+, Ga3+, In3+, Tl3+ and Gd3+. In the presence of these trivalent cations, colorless and nonfluorescent HL‐qui turns pink and strongly fluorescent in HEPES buffer (10 mM) in H2O/ethanol=1/9 (v/v) (pH 7.4) as its spirolactam ring gets open to show the changes in color and fluorescence properties. High sensitivity of the probe towards the cations is reflected from the limit of detection values that are in nM range. To the best of our knowledge, there is no such report where fluorescence sensing has been utilized to determine oxidation state. This multi‐ion sensing feature has been used for fabrication of multi input‐output based logic circuit using Boolean algebraic method. It has been used in imaging of metal ions in living cell (L6 cells).
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Leuthold, J., J. Blundy, and P. Ulmer. "Trace element partitioning in basaltic systems as a function of oxygen fugacity." Contributions to Mineralogy and Petrology 178, no. 12 (November 27, 2023). http://dx.doi.org/10.1007/s00410-023-02069-x.
Abstract:
AbstractAlong with temperature, pressure and melt chemistry, magmatic oxygen fugacity (fO2) has an important influence on liquid and solid differentiation trends and melt structure. To explore the effect of redox conditions on mineral stability and mineral-melt partitioning in basaltic systems we performed equilibrium, one-atmosphere experiments on a picrite at 1200–1110 °C with fO2 ranging from NNO-4 log units to air. Clinopyroxene crystallizes from 1180 °C to near-solidus, along with plagioclase, olivine and spinel. Olivine Mg# increases with increasing fO2, eventually reacting to pigeonite. Spinel is absent under strongly reducing conditions. Mineral-melt partition coefficients (D) of redox-sensitive elements (Cr, Eu, V, Fe) vary systematically with fO2 and, in some cases, temperature (e.g. DCr in clinopyroxene). Clinopyroxene sector zoning is common; sectors along a- and b-axes have higher AlIV, AlVI, Cr and Ti and lower Mg than c-axis sectors. In terms of coupled substitutions, clinopyroxene CaTs (MgSi = AlVIAlIV) prevails under oxidized conditions (≥ NNO), where Fe3+ balances the charge, but is limited under reduced conditions. Overall, AlIV is maximised under high temperature, oxidizing conditions and in slowly grown (a–b) sectors. High AlIV facilitates incorporation of REE (REEAlIV = CaSi), but DREE (except DEu) show no systematic dependence on fO2 across the experimental suite. In sector zoned clinopyroxenes enrichment in REE3+ in Al-rich sectors is quantitatively consistent with the greater availability of suitably-charged M2 lattice sites and the electrostatic energy penalty required to insert REE3+ onto unsuitably-charged M2 sites. By combining our experimental results with published data, we explore the potential for trace element oxybarometry. We show that olivine-melt DV, clinopyroxene-melt DV/DSc and plagioclase-melt DEu/DSr all have potential as oxybarometers and we present expressions for these as a function of fO2 relative to NNO. The crystal chemical sensitivity of heterovalent cation incorporation into clinopyroxene and the melt compositional sensitivity of the Eu2+–Eu3+ redox potential limit the use of clinopyroxene-melt and plagioclase-melt, however, olivine-melt DV affords considerable precision and accuracy as an oxybarometer that is independent of temperature, and crystal and melt composition. Variation of DV and DV/DSc with fO2 for olivine and clinopyroxene contains information on redox speciation of V in coexisting melt. By comparing the redox speciation constraints from partitioning to data from Fe-free synthetic systems and XANES spectroscopy of quenched glasses, we show that homogenous equilibria involving Fe and V species modify V speciation on quench, leading to a net overall reduction in the average vanadium valence. Mineral-melt partitioning of polyvalent species can be a useful probe of redox speciation in Fe-bearing systems that is unaffected by quench effects.
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Hamilton, Heather, and Charles Logan Hussey. "Electrochemistry and Mass Transport of Ytterbium(III) in Bis(trifluoromethylsulfonyl)imide-Based Room-Temperature Ionic Liquids: Effects of Temperature, Viscosity, and Electrode Materials." Journal of The Electrochemical Society, March 29, 2023. http://dx.doi.org/10.1149/1945-7111/acc897.
Abstract:
Abstract Voltammetric and impedance techniques were used to probe the electrochemistry and mass transport of Yb3+ in six hydrophobic room temperature ionic liquids based on the bis(trifluoromethylsulfonyl)imide (Tf2N-) anion. These investigations were carried out at glassy carbon as well as polycrystalline gold, platinum, and tungsten electrodes. The heterogeneous electron transfer rate of the Yb3+/2+ redox couple was found to depend strongly on the electrode materials with the fastest rate observed at gold and the slowest rate found at tungsten, but was independent of the physicochemical properties of the various ionic liquids. However, the mass transport of Yb3+ was dependent on the viscosity, and the temperature dependence of the diffusion coefficients was well represented by a V-T-F expression for glass-forming ionic liquids. Analysis of the diffusion coefficient data indicated that the solvodynamic radius of the diffusing Yb3+ was constant and independent of the structure and properties of the ionic liquid cations. The radius was estimated from the “stick model” for the Stokes-Einstein equation. Application of the Random Closest Packing (RCP) model for spheres in consideration of the solvodynamic radius of the diffusing Yb3+ entity indicated that this species must diffuse in association with ~5-6 of the anions.