Analysis of amplitude modulation atomic force microscopy in aqueous salt solutions

Cataloged from PDF version of article.We present a numerical analysis of amplitude modulation atomic force microscopy in aqueous salt solutions, by considering the interaction of the microscope tip with a model sample surface consisting of a hard substrate and soft biological material through Hertz and electrostatic double layer forces. Despite the significant improvements reported in the literature concerning contact-mode atomic force microscopy measurements of biological material due to electrostatic interactions in aqueous solutions, our results reveal that only modest gains of similar to 15% in imaging contrast at high amplitude setpoints are expected under typical experimental conditions for amplitude modulation atomic force microscopy, together with relatively unaffected sample indentation and maximum tip-sample interaction values. (C) 2014 Elsevier B.V. All rights reserved.We present a numerical analysis of amplitude modulation atomic force microscopy in aqueous salt solutions, by considering the interaction of the microscope tip with a model sample surface consisting of a hard substrate and soft biological materialthrough Hertz and electrostatic double layer forces. Despite the significant improvements reported in the literature concerning contact-mode atomic force microscopy measurements of biological material due to electrostatic interactions in aqueous solutions, our results reveal that only modest gains of ∼15% in imaging contrast at high amplitude setpoints are expected under typical experimental conditions for amplitude modulation atomic force microscopy, together with relatively unaffected sample indentation and maximum tip–sample interaction value

New insights into the electrode/electrolyte interface on positive electrodes in Li-Ion batteries

International audienceUnderstanding and controlling the reactivity at the electrode/electrolyte interface (EEI) is one of the key issues for the development of high capacity and efficient lithium-ion batteries. The heterogeneous and partially catalytic reaction of the electrode with the electrolyte triggers the formation of surface films on the electrode surface which can cause degradation of the cell performance. Whereas the EEI layer properties are quite well known for negative electrodes such as lithium metal and graphite [1,2], the EEI layer on positive electrode materials is still puzzling. Especially the interface layers on high voltage and high capacity positive electrodes, whose potentials approach the limit of electrolyte stability against oxidation [3], is quite unexplored. One of the challenges in understanding the reactions at the surface of the electrode is the complicated composition of the positive electrodes, containing not only the active material but also conductive agents and polymeric binders, that can modify the EEI layers on the electrode. To bypass these ambiguities, there is a need for study model electrodes such as thin films or pure active material electrodes, which allow for investigating solely the reactivity of the electrolyte at the active material surface. Here, combining X-ray Photoelectron Spectroscopy (XPS and X-ray Absorption and Emission Spectroscopy (XAS/XES), of model electrodes, we will show how the species formed at the electrode/electrolyte interface are affected by change in charging potential and the structure and nature of the transition metal in the material. XES and XAS will be used to shed light on the change of electronic structure upon delithiation

The Effect of Electrode-Electrolyte Interface on the Electrochemical Impedance Spectra for Positive Electrode in Li-Ion Battery

Understanding the effect of electrode-electrolyte interface (EEI) on the kinetics of electrode reaction is critical to design high-energy Li-ion batteries. While electrochemical impedance spectroscopy (EIS) is used widely to examine the kinetics of electrode reaction in Li-ion batteries, ambiguities exist in the physical origin of EIS responses for composite electrodes. In this study, we performed EIS measurement by using a three-electrode cell with a mesh-reference electrode, to avoid the effect of counter electrode impedance and artefactual responses due to asymmetric cell configuration, and composite or oxide-only working electrodes. Here we discuss the detailed assignment of impedance spectra for LiCoO[subscript 2] as a function of voltage. The high-frequency semicircle was assigned to the impedance associated with ion adsorption and desorption at the electrified interface while the low-frequency semicircle was related to the charge transfer impedance associated with desolvation/solvation of lithium ions, and lithium ion intercalation/de-intercalation into/from LixCoO[subscript 2]. Exposure to higher charging voltages and greater hold time at high voltages led to no significant change for the high-frequency component but greater resistance and greater activation energy for the low-frequency circle. The greater charge transfer impedance was attributed to the growth of EEI layers on the charged LixCoO[subscript 2] surface associated with electrolyte oxidation promoted by ethylene carbonate dehydrogenation. Keywords: Batteries - Lithium, Electrode Kinetics, EIS, Electrode-Electrolyte Interface, Li-ion BatteriesBMW Grou

Reactivity with Water and Bulk Ruthenium Redox of Lithium Ruthenate in Basic Solutions

The reactivity of water with Li rich layered Li2RuO3 and partial exchange of Li2O with H2O within the structure has been studied under aqueous electro chemical conditions. Upon slow delithiation in water over long time periods, micron size Li2RuO3 particles structurally transform from an O3 structure to an O1 structure with a corresponding loss of 1.25 Li ions per formula unit. The O1 stacking of the honeycomb Ru layers is imaged using high resolution HAADF STEM, and the resulting structure is solved from X ray powder diffraction and electron diffraction. In situ X ray absorption spectroscopy suggests that reversible oxidation reduction of bulk Ru sites is realized on potential cycling between 0.4 VRHE and 1.25 VRHE in basic solutions. In addition to surface redox pseudocapacitance, the partially delithiated phase of Li2RuO3 shows high capacity which can be attributed to bulk Ru redox in the structure. This work demonstrates that the interaction of aqueous electrolytes with Li rich layered oxides, can result in the formation of new phases with electro chemical properties that are distinct from the parent material. This understanding is important for the design of aqueous batteries, electrochemical capacitors and chemically stable cathode materials for Li ion batterie

Understanding electronic structure and interfaces of positive electrodes for lithium ion batteries

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.Includes bibliographical references (pages 104-110).Lithium ion batteries are the currently the best commercial battery in the market and they are used as energy storage devices for mobile phones, laptops, and other portable electronic devices. This is due to their balance of high energy density with high power density compared to other electrochemical energy devices. Also, these days the automotive industry wants to use lithium ion batteries to electric vehicles to reduce the pollution and independence to oil. Although lithium ion batteries are currently one of the best energy storage devices, there is still an ample room for improvement. One of the key parameters to study is electrode/electrolyte interface of electrodes. EEI on the negative electrode, also known as Solid Electrolyte Interphase (SEI) has the well-known structure with organic and inorganic compounds. Although EEI on negative electrodes is well known, it is not the case for positive electrodes. Numerous studies have been done on positive electrodes; however, there is still a need for systematic study of these interfaces on positive electrodes. This thesis is about understanding the reactivity and interactions of Li-ion battery positive electrode materials with the electrolyte. By understanding reactions at the EEI, we can develop a way to improve cycle life and safety of lithium ion batteries. To unambiguously pinpoint the electrode/electrolyte interface layers on different positive electrode materials, 100 % active materials are used as positive electrodes instead of composite electrodes.by Pinar Karayaylali.S.M

Analysis of amplitude modulation atomic force microscopy in aqueous salt solutions

We present a numerical analysis of amplitude modulation atomic force microscopy in aqueous salt solutions, by considering the interaction of the microscope tip with a model sample surface consisting of a hard substrate and soft biological material through Hertz and electrostatic double layer forces. Despite the significant improvements reported in the literature concerning contact-mode atomic force microscopy measurements of biological material due to electrostatic interactions in aqueous solutions, our results reveal that only modest gains of ∼15% in imaging contrast at high amplitude setpoints are expected under typical experimental conditions for amplitude modulation atomic force microscopy, together with relatively unaffected sample indentation and maximum tip-sample interaction values. © 2014 Elsevier B.V. All rights reserved

Effects of Trimetazidine and Selenium on High-Frequency Fatigue in Isolated Rat Diaphragm Muscle

Trimetazidine (TMZ), which has been used in numerous experimental studies, is applied nowadays with the aim of reducing myocardial ischemia. The aim of this study was to determine the prefatigue and postfatigue contractile characteristics associated with the relationship between the force and frequency of contraction in muscle. The study was conducted using diaphragm muscle isolated from 40 male Wistar rats weighing 230 to 270 g. The rats were divided into 4 groups of 10 animals each: controls and TMZ-, selenium (Se)-, and TMZ+Se-treated groups. The rats in the control group were treated with 2 mL of physiologic serum (SF), those in the second group with Se 30 µg/kg in 2mL of SF, those in the third group with TMZ 5 mg/kg in 2 mL of SF, and those in the fourth group with a combination of TMZ 5 mg/kg + Se 30 µg/kg in 2 mL of SF. All rats were treated twice daily for 15 days by means of gastric lavage. The rats were then killed by cervical dislocation. The diaphragm muscle bands were removed and placed in an organ bath. After a 2-hour thermoregulatory period, muscles were fatigued with 5-ms pulses at a frequency of 40 Hz. Force-frequency relationships were studied after the application of 10, 50, and 100 Hz and the development of contraction curves. Contraction forces for the groups treated with TMZ, Se, and TMZ+Se (16.1±1.2, 13.2±1.3, and 14.9±1.0 g, respectively) were significantly lower than for the control group (17.0±1.4 g) during the prefatigue period (P<.001). Similarly, postfatigue contraction forces for the treated groups (15.7±1.3, 8.8±1.0, and 12.0±1.4 g, respectively) were significantly lower than for the control group (12.4±1.2 g, P<.001, P<.001, and P<.05, respectively). A significant decrease was noted in postfatigue contraction forces and contraction and relaxation rates in the Se- and TMZ+Se-treated groups compared with prefatigue values (P<.001), but the difference was not significant. Force-frequency relationships were evaluated at 10, 50, and 100 Hz. The tetanic contraction forces for the control, Se-, TMZ-, and TMZ+Se-treated groups at 100 Hz were 81.3±5.7, 91.6±6.8, 65.3±5.0, and 84.9±7.5 g, respectively. In the TMZ-treated group, a significant increase was observed in tetanic contraction forces at 100 Hz compared with controls (P<.001); no significant changes were seen in the force-frequency relationships at 10 and 50 Hz. The decrease in the contraction force in the postfatigue period was prevented to a larger extent in the TMZ-treated group than in the TMZ+Se- and Se-treated groups

Severe acute renal failure due to tubulointerstitial nephritis, pancreatitis, and hyperthyroidism in a patient during rifampicin therapy

It is well known that rifampicin can cause nephrotoxicity. Rifampicin-related pancreatitis and hyperthyroidism are rarely reported in the same patient in the presence of tubulointerstitial nephritis. Reported herein is the medical management of a patient with hemolytic anemia, acute renal failure, pancreatitis, and hyperthyroidism during with rifampicin therapy. A 50-year-old man was admitted to the hospital owing to abdominal colic and acute renal failure. He was treated with 2 courses of tetracycline-rifampicin for brucellosis 3 weeks and 4 months prior to admission. Physical examination showed blood pressure of 130/70 mm Hg, pulmonary crackles, and edema. Laboratory findings are detailed in the case report. Findings of abdominal ultrasonography suggested edematose pancreatitis and thyroid ultrasonography showed several solid nodules. Renal biopsy showed tubulointerstitial nephritis. Although rifampicin-related tubulointerstitial nephritis and acute renal failure are not uncommon during rifampicin therapy, the convergence of hyperthyroidism, pancreatitis, tubulointerstitial nephritis, and acute renal failure rarely presents in the same patient. Although pancreatitis, tubulointerstitial nephritis, and acute renal failure were ameliorated with corticoid therapy within 2 months, hyperthyroidism continued and required antithyroid therapy. In conclusion, rifampicin may trigger hyperthyroidism in patients with goiter. © 2005 Health Communications Inc