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1. Detection of Diclofenac and Carbamazepine using Voltammetry and Flow Injection Analysis at Boron‐Doped Diamond Thin‐Film Electrodes

   https://doi.org/10.1002/elan.202400157  

   Jacobs, Aaron I; Zwane, Simphiwe; Jarošová, Romana; Zamora, Marissa D; Kuvarega, Alex T; Swain, Greg (December 2024, Electroanalysis)

   Abstract The electrochemical detection of two pharmaceuticals, diclofenac (DCF) and carbamazepine (CBZ), was investigated as an oxidation current using boron‐doped nanocrystalline diamond (BDD) thin‐film electrodes. Both voltammetry and flow injection analysis with amperometric detection (FIA‐EC) were used to measure the drugs in standard solutions and a urine simulant. The oxidation potential for DCF wasca. 0.7 V vs. Ag/AgCl (3 M KCl) in 0.1 M phosphate buffer (pH 7.2) and wasca. 1.2 V for CBZ in 0.1 M perchloric acid. The DCF oxidation reaction was diffusion controlled at the detection potential with evidence of some surface fouling by reaction products. The CBZ oxidation reaction was also controlled by diffusion at the detection potential, but with no surface fouling. The voltammetric peak currents for both drugs increased linearly with the concentration in the micromolar range (r²≥0.994). FIA‐EC analysis of DCF and CBZ revealed a linear dynamic range from at least 0.1 to 100 μM with the actual minimum concentration detectable (S/N=3) being less than the lowest concentration measured. The recovery percentage for DCF in the urine simulant ranged from 94–108% and from 97–100% for CBZ, both assessed using square wave voltammetry. FIA‐EC data revealed that the BDD electrodes offer excellent intra and inter‐electrode repeatability with an RSD for DCF and CBZ of 4.90% and 3.81%, respectively. The BDD electrode provided good reproducibility and response stability over eight days of continuous use detecting both DCF and CBZ. Overall, BDD electrodes are a viable material  for the sensitive, selective, and reproducible electrochemical detection of these two pharmaceuticals. 

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2. Ion Selectivity of Intercalation Electrodes in Dual-Ion Electrolytes: Modeling Ion Selectivity as the Sum of Individual Cation Effects

   https://doi.org/10.1149/1945-7111/adf9cc  

   Pothanamkandathil, Vineeth; Feineman, Maureen; Gorski, Christopher A (July 2025, Journal of The Electrochemical Society)

   Intercalation electrode materials reversibly insert cations into their lattices under applied potentials or currents, which can be used to perform electrochemical separations. Optimizing performance, however, remains challenging due to tradeoffs between selectivity and separation rate being influenced by multiple variables. This study developed a quantitative model to describe the current response and cation selectivity of an intercalation electrode in a binary cation solution during cyclic voltammetry. We hypothesized that current responses and selectivity could be calculated by summing individual ion contributions. Cyclic voltammograms were experimentally measured using nickel hexacyanoferrate electrodes in NaCl, KCl, or mixed solutions. Post-mortem electron probe micro-analysis quantified intercalated Na⁺and K⁺fractions. A one-dimensional finite element model incorporating the Nernst-Frumkin isotherm, Butler-Volmer kinetics, and ion diffusion was developed, parameterized with pure NaCl or KCl solutions, and validated against mixed solutions. The model accurately reproduced experimental cyclic voltammograms and ion partitioning behaviors at ionic strengths ≥0.2 mol·l⁻¹. However, at lower ionic strengths, significant discrepancies arose for reasons still unclear. Results indicate that modeling ion contributions individually effectively captures the electrochemical response of selective intercalation electrodes at sufficiently high ionic strengths. 

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3. Reduced Glutathione-Modified Electrode for the Detection of Hydroxyl Free Radicals

   https://doi.org/10.3390/bios13020254  

   Ghaedamini, Hamidreza; Duanghathaipornsuk, Surachet; Onusko, Patrick; Binsheheween, Abdullah M; Kim, Dong-Shik (February 2023, Biosensors)

   Hydroxyl radicals (•OH) are known as essential chemicals for cells to maintain their normal functions and defensive responses. However, a high concentration of •OH may cause oxidative stress-related diseases, such as cancer, inflammation, and cardiovascular disorders. Therefore, •OH can be used as a biomarker to detect the onset of these disorders at an early stage. Reduced glutathione (GSH), a well-known tripeptide for its antioxidant capacity against reactive oxygen species (ROS), was immobilized on a screen-printed carbon electrode (SPCE) to develop a real-time detection sensor with a high selectivity towards •OH. The signals produced by the interaction of the GSH-modified sensor and •OH were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV curve of the GSH-modified sensor in the Fenton reagent exhibited a pair of well-defined peaks, demonstrating the redox reaction of the electrochemical sensor and •OH. The sensor showed a linear relationship between the redox response and the concentration of •OH with a limit of detection (LOD) of 49 µM. Furthermore, using EIS studies, the proposed sensor demonstrated the capability of differentiating •OH from hydrogen peroxide (H2O2), a similar oxidizing chemical. After being immersed in the Fenton solution for 1 hr, redox peaks in the CV curve of the GSH-modified electrode disappeared, revealing that the immobilized GSH on the electrode was oxidized and turned to glutathione disulfide (GSSG). However, it was demonstrated that the oxidized GSH surface could be reversed back to the reduced state by reacting with a solution of glutathione reductase (GR) and nicotinamide adenine dinucleotide phosphate (NADPH), and possibly reused for •OH detection. 

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4. Tunnel structured manganese oxide nanowires as redox active electrodes for hybrid capacitive deionization

   https://doi.org/https://doi.org/10.1016/j.nanoen.2017.12.015  

   Byles, Bryan W.; Cullen, David A.; More, Karren L.; Pomerantseva, Ekaterina (January 2018, Nano energy)

   Hybrid capacitive deionization (HCDI), which combines a capacitive carbon electrode and a redox active electrode in a single device, has emerged as a promising method for water desalination, enabling higher ion removal capacity than devices containing two carbon electrodes. However, to date, the desalination performance of few redox active materials has been reported. For the first time, we present the electrochemical behavior of manganese oxide nanowires with four different tunnel crystal structures as faradaic electrodes in HCDI cells. Two of these phases are square tunnel structured manganese oxides, α-MnO2 and todorokite-MnO2. The other two phases have novel structures that cross-sectional scanning transmission electron microscopy analysis revealed to have ordered and disordered combinations of structural tunnels with different dimensions. The ion removal performance of the nanowires was evaluated not only in NaCl solution, which is traditionally used in laboratory experiments, but also in KCl and MgCl2 solutions, providing better understanding of the behavior of these materials for desalination of brackish water that contains multiple cation species. High ion removal capacities (as large as 27.8 mg g−1, 44.4 mg g−1, and 43.1 mg g−1 in NaCl, KCl, and MgCl2 solutions, respectively) and high ion removal rates (as large as 0.112 mg g−1 s−1, 0.165 mg g−1 s−1, and 0.164 mg g−1 s−1 in NaCl, KCl, and MgCl2 solutions, respectively) were achieved. By comparing ion removal capacity to structural tunnel size, it was found that smaller tunnels do not favor the removal of cations with larger hydrated radii, and more efficient removal of larger hydrated cations can be achieved by utilizing manganese oxides with larger structural tunnels. Extended HCDI cycling and ex situ X-ray diffraction analysis revealed the excellent stability of the manganese oxide electrodes in repeated ion removal/ion release cycles, and compositional analysis of the electrodes indicated that ion removal is achieved through both surface redox reactions and intercalation of ions into the structural tunnels. This work contributes to the understanding of the behavior of faradaic materials in electrochemical water desalination and elucidates the relationship between the electrode material crystal structure and the ion removal capacity/ion removal rate in various salt solutions. 

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5. Modeling Charging Current Dynamics at Microelectrodes and their Interfaces with Electrolyte and Insulators with a Focus on Microfabricated Gold Microband Electrodes on an SU-8 Substrate

   https://doi.org/10.1149/1945-7111/ad546f  

   Abrego_Tello, Miguel A; Lotfi_Marchoubeh, Mahsa; Fritsch, Ingrid (June 2024, Journal of The Electrochemical Society)

   The suitability of electrochemical methods for quantitative measurements at microdevices is influenced by the relatively large electrode-insulator interface-to-electrode area ratio, greatly impacting charging dynamics due to interactions among electrolyte, conductor material, and insulator layers. The resulting charging current can overwhelm the faradaic current from redox chemistry. The device studied here features a 70μm × 100μm electroactive window, hosts gold coplanar microband electrodes, and is insulated by SU-8, which serves as both overlayer and substrate. The overlayer defines the electroactive length and isolates the leads of the electrodes from the sample solution. Cyclic voltammetry in 0.10 M KCl yields an unexpected, nonlinear dependence of current on scan rate, which can be explained with two empirical approaches. The first employs an equivalent circuit model, involving leakage resistance and double-layer capacitance in parallel, to address both background processes and electrode imperfections as a function of scan rate. The second associates the enhanced current to a changing-chargeable area resulting from interface irregularities. Prior publications on alternative conductor-insulator materials are benchmarked in this study. The comparison of the materials shows that the charging dynamics for devices made with SU-8 lead to more favorable electrochemical performance than for those constructed with glass, epoxy, and silicon nitride, and under certain circumstances, polyimide. 

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