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Iona??Selective Sensors Based on Lasera??Induced Graphene for Evaluating Human Hydration Levels Using Urine Samples
摘要： Complex graphene electrode fabrication protocols including conventional chemical vapor deposition and graphene transfer techniques as well as more recent solution-phase printing and postprint annealing methods have hindered the wide-scale implementation of electrochemical devices including solid-state ion-selective electrodes (ISEs). Herein, a facile graphene ISE fabrication technique that utilizes laser induced graphene (LIG), formed by converting polyimide into graphene by a CO2 laser and functionalization with ammonium ion (NH4+) and potassium ion (K+) ion-selective membranes, is demonstrated. The electrochemical LIG ISEs exhibit a wide sensing range (0.1 × 10?3–150 × 10?3 m for NH4+ and 0.3 × 10?3–150 × 10?3 m for K+) with high stability (minimal drop in signal after 3 months of storage) across a wide pH range (3.5–9.0). The LIG ISEs are also able to monitor the concentrations of NH4+ and K+ in urine samples (29–51% and 17–61% increase for the younger and older patient; respectively, after dehydration induction), which correlate well with conventional hydration status measurements. Hence, these results demonstrate a facile method to perform in-field ion sensing and are the first steps in creating a protocol for quantifying hydration levels through urine testing in human subjects.
关键词： graphene,solid-contact ion-selective electrode (ISE),potentiometry,urinalysis,hydration
更新于2025-09-23 15:21:01
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Light addressable ion sensing for real-time monitoring of extracellular potassium
摘要： Visualization of ion distribution has broad applications. We report here on a light addressable potassium (K+) sensor where light illumination of a semiconducting silicon electrode substrate results in a localized activation of the faradaic electrochemistry at the illuminated spot. This allows one, by electrochemical control, to oxidize surface bound ferrocene moieties that in turn trigger K+ transfer from the overlaid K+-selective film to the solution phase. The resulting voltammetric response is shown to be K+-selective, where peak position is a direct function of K+ activity at the surface of electrode. This concept was used to measure extracellular K+ concentration changes by stimulating living breast cancer cells. The associated decrease of intracellular K+ level was confirmed with a fluorescent K+ indicator. In contrast to light addressable potentiometry, the approach introduced here relies on dynamic electrochemistry and may be performed in tandem with other electrochemical analysis when studying biological events on the electrode.
关键词： physiological condition,potassium,light activated electrochemistry,ion-selective electrode,potentiometry
更新于2025-09-23 15:21:01
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Light addressable ion sensing for real-time monitoring of extracellular potassium
摘要： Visualization of ion distribution has broad applications. We report here on a light addressable potassium (K+) sensor where light illumination of a semiconducting silicon electrode substrate results in a localized activation of the faradaic electrochemistry at the illuminated spot. This allows one, by electrochemical control, to oxidize surface bound ferrocene moieties that in turn trigger K+ transfer from the overlaid K+-selective film to the solution phase. The resulting voltammetric response is shown to be K+-selective, where peak position is a direct function of K+ activity at the surface of electrode. This concept was used to measure extracellular K+ concentration changes by stimulating living breast cancer cells. The associated decrease of intracellular K+ level was confirmed with a fluorescent K+ indicator. In contrast to light addressable potentiometry, the approach introduced here relies on dynamic electrochemistry and may be performed in tandem with other electrochemical analysis when studying biological events on the electrode.
关键词： physiological condition,potassium,light activated electrochemistry,ion-selective electrode,potentiometry
更新于2025-09-23 15:21:01
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KEV: a free software for calculating the equilibrium composition and determining the equilibrium constants using UV-Vis and potentiometric data
摘要： Present paper reports on an algorithm for calculating the equilibrium composition of several compounds mixture if their total (equilibrium) concentrations and the equilibrium constants of reactions between them are known. The algorithm for determining the unknown equilibrium constants from UV-Vis or potentiometric experimental data using minimizing function (maximal likelihood method) is described. The recommendations on the evaluating of equilibrium constants from experimental results are given. The algorithms described are realized as free-of-charge distributed software/scripts bundle/source code.
关键词： potentiometry,UV-Vis spectroscopy,constant,equilibrium
更新于2025-09-19 17:15:36
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A Novel Transparent pH Sensor Based on a Nanostructured ITO Electrode Coated with [3,3′-Co(1,2-C2B9H11)2]-Doped Poly(pyrrole)
摘要： A novel transparent and nanostructured ion-sensitive electrode based on indium tin oxide (ITO) coated with cobaltbis(dicarbollide)-doped poly(pyrrole) (PPy) is presented in this work. This metallacarborane-doped PPy was used as conducting polymer due to its high stability and chemical resistance. The ion-sensitive electrode was coupled to a miniaturized and low-cost potentiostat, in a final autonomous kit for potentiometric determination of pH. Qualitative calibration of the system revealed Nernstian behavior, resulting promising for novel point-of-care biomedical applications.
关键词： indium tin oxide (ITO),intrinsically conducting polymer (ICP),poly(pyrrole) (PPy),pH sensor,potentiometry,potentiometric sensor,boron compounds,nanoscience,metallacarboranes
更新于2025-09-10 09:29:36
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Scanning probe microscopy and potentiometry using a junction field effect transistor based sensor
摘要： Scanning tunneling microscopy in its conventional form relies on a steady state tunneling current of 10?12–10?6 A. However, for various applications, it is desirable to reduce the current load to a minimum. Here, we present first experiments using a cooled junction field effect transistor in open gate operation, thereby reducing the DC-current to less than 10?19 A. This enables almost ideal measurements of the local electrochemical potential on a surface. Various methods applying dynamic modes can be used to maintain a constant distance between the scanning probe and the sample surface. Here, we use an AC-bias applied to the sample and a lock-in amplifier connected to the preamplifier to evaluate the conductance of the tunneling gap.
关键词： potentiometry,scanning probe microscopy,junction field effect transistor,sensor
更新于2025-09-09 09:28:46