Abstract:The electrochemical response of
millimeter-sized hematite (α-Fe2O3) electrode
surfaces to bound ions of NaCl, NH4Cl, and NaHCO3 salts was monitored by alternating
current scanning electrochemical microscopy (AC-SECM). Local electrochemical
impedance spectroscopy (LEIS) measurements along 100 μm lines
on the (001) and (012) faces of hematite were used to extract capacitance
and resistance parameters affected by bound inorganic ions. Equivalent
circuit modeling was used to suggest that (1) double layer capacita… Show more
“…The absence of response at frequencies above ~3000 Hz shows that the applied AC cannot trigger space charge or bulk electron transport in hematite, as we have previously reported when the UME is in direct electrochemical contact with hematite 37 – 40 . As the ~30–3000 Hz region is more typical of solution-side processes 37 , 38 , we assigned the polarization resistance ( R bubble ) and double layer capacitance ( C bubble ) terms of the equivalent model to ion transport at bubble surfaces. Fig.…”
Gas bubbles grown on solids are more than simple vehicles for gas transport. They are charged particles with surfaces populated with exchangeable ions. We here unveil a gateway for alkali metal ion transport between oxygen bubbles and semi-conducting (iron oxide) and conducting (gold) surfaces. This gateway was identified by electrochemical impedance spectroscopy using an ultramicroelectrode in direct contact with bubbles pinned onto these solid surfaces. We show that this gateway is naturally present at open circuit potentials, and that negative electric potentials applied through the solid enhance ion transport. In contrast, positive potentials or contact with an insulator (polytetrafluoroethylene) attenuates transport. We propose that this gateway is generated by overlapping electric double layers of bubbles and surfaces of contrasting (electro)chemical potentials. Knowledge of this ion transfer phenomenon is essential for understanding electric shielding and reaction overpotential caused by bubbles on catalysts. This has especially important ramifications for predicting processes including mineral flotation, microfluidics, pore water geochemistry, and fuel cell technology.
“…The absence of response at frequencies above ~3000 Hz shows that the applied AC cannot trigger space charge or bulk electron transport in hematite, as we have previously reported when the UME is in direct electrochemical contact with hematite 37 – 40 . As the ~30–3000 Hz region is more typical of solution-side processes 37 , 38 , we assigned the polarization resistance ( R bubble ) and double layer capacitance ( C bubble ) terms of the equivalent model to ion transport at bubble surfaces. Fig.…”
Gas bubbles grown on solids are more than simple vehicles for gas transport. They are charged particles with surfaces populated with exchangeable ions. We here unveil a gateway for alkali metal ion transport between oxygen bubbles and semi-conducting (iron oxide) and conducting (gold) surfaces. This gateway was identified by electrochemical impedance spectroscopy using an ultramicroelectrode in direct contact with bubbles pinned onto these solid surfaces. We show that this gateway is naturally present at open circuit potentials, and that negative electric potentials applied through the solid enhance ion transport. In contrast, positive potentials or contact with an insulator (polytetrafluoroethylene) attenuates transport. We propose that this gateway is generated by overlapping electric double layers of bubbles and surfaces of contrasting (electro)chemical potentials. Knowledge of this ion transfer phenomenon is essential for understanding electric shielding and reaction overpotential caused by bubbles on catalysts. This has especially important ramifications for predicting processes including mineral flotation, microfluidics, pore water geochemistry, and fuel cell technology.
“…Electrochemical impedance spectroscopy (EIS) is an analysis method that has an extensive application and a simple operation . It is used to analyze electron transfer onto an electrode surface to study the cephalosporin–DNA complex.…”
The over-use of antibiotics has caused a number of problems such as contamination of antibiotic residues and virus resistance, and therefore has attracted global attention. In this study, spectroscopic techniques and molecular docking were employed to predict conformational changes and binding interaction between two cephalosporins (cefaclor and cefixime) and calf thymus DNA (ctDNA). Fluorescence and UV-vis spectra suggested that static quenching was predominant and cephalosporin bound to the groove region of ctDNA. Binding parameters calculated by the Stern-Volmer and Scatchard equations showed that cephalosporin bound to ctDNA with a binding affinity in the order of 10 3 L mol −1 . Thermodynamic parameters further indicated that the reaction was a spontaneous process driven by enthalpy and entropy, and that the main binding force was an electrostatic force. The effects of iodide, denaturant, thermal denaturation and pH on a cephalosporin-Hoechst-DNA complex were also studied, and the results confirmed that cephalosporin bound to the groove area of DNA.Finally, these results were further confirmed by molecular docking and electrochemical studies.
“…Then, they were sonicated for 1 min in acetone, ethanol, methanol, and 50% v/v methanol/water mixture for complete cleaning and finally immersed in ultrahigh water until use. 41 The decoration of the peptide on newly cleaved mica (001) was conducted according to a reported procedure. 42 In brief, the mica surface was silanized with trimethoxysilylpropyl-diethylenetriamine (DAEAPTS) first; then, it was transformed into an aldehyde layer by incubating it with glutaraldehyde and finally rinsed in water to remove loosely bound molecules.…”
Phosphate (P) adsorption systems featuring metal-based adsorbents have claimed to achieve ultralow P removal. However, little is known about the micron- and molecular-scale energetic knowledge of P-adsorbent interactions including the...
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