Direct determination of the adsorption free energy for extremely low surface coverages (Henry limit) requires the use of a technique that must be highly sensitive to both the amount and the energetics of adsorbed molecules. Herein, we demonstrate that diffusional surface voltammetry (DSV), which embodies film and stripping voltammetries as two limiting cases, can be used to achieve this goal for electroactive adsorbates. To this end, a general analytical expression for the surface voltammetric peak potential of DSV is derived, which covers the full range of scan rates, bulk concentrations, and adsorptivity of the freely diffusing form of the redox couple, so that the surface redox conversion can be either equilibrated with or transport-isolated from the solution bulk. Strategies to get a quantitative insight into the energetics of electrosorption are outlined, and diagnostic criteria for their application are developed. In particular, it is demonstrated that DSV can be used in its stripping mode to determine group contributions to the adsorption free energy, avoiding possible interferences from intermolecular interactions or formation of oligomeric species. Application of this protocol to the reductive desorption of distinct homologous series of alkylthiolates adsorbed at mercury electrodes has allowed us to determine the contributions of the CH(n) groups (n = 0-3) to the free energy of adsorption of these molecules. These estimates are shown to correlate linearly with the corresponding group contributions to the octanol-water partition coefficient, revealing that adsorption of individual hydrocarbon groups at the mercury/solution interface scales with their hydrophobicity. Overall, the present work enlarges the capability of surface voltammetry to probe adsorption energetics down to the micromolar level, and it represents a first step toward the development of a unified treatment of stripping and film voltammetries.
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ACS Omega
January 2025
Department of Biomedical Engineering, Hanyang University, Seoul 04763, Republic of Korea.
Fast-scan cyclic voltammetry (FSCV) is a widely used electrochemical technique to measure the phasic response of neurotransmitters in the brain. It has the advantage of reducing tissue damage to the brain due to the use of carbon fiber microelectrodes as well as having a high temporal resolution (10 Hz) sufficient to monitor neurotransmitter release in vivo. During the FSCV experiment, the surface of the carbon fiber microelectrode is inevitably changed by the fouling effect.
View Article and Find Full Text PDFLangmuir
January 2025
Department of Chemistry, Christ University, Bangalore 560029, Karnataka.
The inclusion of redox mediators into electrocatalytic systems facilitates rapid electron shuttling kinetics and boosts the overall catalytic performance of the electrode. This approach overcomes the sluggish reaction dynamics associated with direct electron transfer, which may be impeded by restricted analyte access to the electrode's active sites. In contrast to conventional synthetic redox mediators, naturally sourced phytomolecule rutin trihydrate (RT), extracted from apple juice, offers potential ecological advantages.
View Article and Find Full Text PDFBiosens Bioelectron
January 2025
Department of Chemistry, Kansas State University, Manhattan, KS, 66502, USA. Electronic address:
Proteases are overexpressed at various stages of conditions such as cancers and thus can serve as biomarkers for disease diagnosis. Electrochemical techniques to detect the activity of extracellular proteases have gained attraction due to their multiplexing capability. Here we employ an electrochemical approach based on a 3 × 3 gold (Au) microelectrode array (MEA) functionalized with (2-aminoethyl)ferrocene (AEF) tagged specific peptide substrates to monitor cathepsin B (CB) protease activity.
View Article and Find Full Text PDFPolymers (Basel)
January 2025
Centro de Investigación y Desarrollo Tecnológico en Electroquímica SC, Parque Tecnológico Querétaro s/n Sanfandila, Pedro Escobedo, Querétaro 76703, Mexico.
Our work describes the green synthesis of silver sulfide nanoparticles (AgS NPs) and their formulation into polycaprolactone fibers (PCL), aiming to improve the multifunctional biological performance of PCL membranes as scaffolds. For this purpose, an extract of rosemary () was employed as a reducing agent for the AgS NPs, obtaining irregular NPs and clusters of 5-60 nm, with a characteristic SPR absorption at 369 nm. AgS was successfully incorporated into PCL fibers by electrospinning using heparin (HEP) as a stabilizer/biocompatibility agent, obtaining nanostructured fibers with a ca.
View Article and Find Full Text PDFMolecules
January 2025
Department of Chemistry, Middle Tennessee State University, 440 Friendship Street, Murfreesboro, TN 37132, USA.
Elevated dopamine (DA) levels in urine denote neuroblastoma, a pediatric cancer. Saccharide-derived carbon dots (CDs) were applied to assay DA detection in simulated urine (SU) while delineating the effects of graphene defect density on electrocatalytic activity. CDs were hydrothermally synthesized to vary graphene defect densities using sucrose, raffinose, and palatinose, depositing them onto glassy carbon electrodes (GCEs).
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