Efficient sensing of hydrogen peroxide via electrocatalytic oxidation reactions using polycrystalline Au electrode modified with controlled thiol group immobilization

Ultrasensitive Peptide-Based Electrochemical Biosensor for Universal Diagnostic of Dengue

Dengue is a neglected disease mainly affecting tropical and subtropical countries. The diagnosis of dengue fever is still a problem since most of it is made from whole or recombinant DENV proteins, which present cross-reactions with other members of the Flavivirus family. Therefore, there is still a huge demand for new diagnostic methods that provide rapid, low-cost, easy-to-use confirmation. Thus, in this study, we developed an affordable electrochemical biosensor for rapidly detecting immunoglobulin G (IgG) serological antibodies in the sera of DENV-infected patients. An identified linear B-cell epitope (DENV/18) specific for DENV 1-4 serotypes recognized by IgG in patient sera was selected as a target molecule after a microarray of peptides using the SPOT-synthesis methodology. After chemical synthesis, the DENV/18-peptide was immobilized on the surface of the working electrode of a commercially available screen-printed gold electrode (SPGE). The capture of DENV-specific IgG allowed for the formation of an immunocomplex that was measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using a potassium ferrocyanide/ferricyanide ([Fe(CN)6]3-/4-) electrochemical probe. An evaluation of the biosensor's performance showed a detection limit of 100 µg mL-1 for the synthetic peptides (DENV/18) and 1.21 ng mL-1 in CV and 0.43 ng mL-1 in DPV for human serum, with a sensitivity of 7.21 µA in CV and 8.79 µA in DPV. The differentiation of infected and uninfected individuals was possible even at a high dilution factor that reduced the required sample volumes to a few microliters. The final device proved suitable for diagnosing DENV by analyzing real serum samples, and the results showed good agreement with molecular biology diagnostics. The flexibility to conjugate other antigenic peptides to SPEs suggests that this technology could be rapidly adapted to diagnose other pathogens.

Voltammetric determination of hydrogen peroxide at decorated palladium nanoparticles/poly 1,5-diaminonaphthalene modified carbon-paste electrode

In this work, palladium nanoparticles (PdNPs)/p1,5-DAN/ carbon paste electrode (CPE) and p1,5-DAN/CPE sensors have been developed for determination of hydrogen peroxide. Both sensors showed a highly sensitive and selective electrochemical behaviour, which were derived from a large specific area of poly 1,5 DAN and super excellent electroconductibility of PdNPs. PdNPs/p1,5-DAN/CPE exhibited excellent performance over p1,5-DAN/CPE. Thus, it was used for detecting hydrogen peroxide (H2O2) with linear ranges of 0.1 to 250 µM and 0.2 to 300 µM as well as detection limits (S/N = 3) of 1.0 and 5.0 nM for square wave voltammetry (SWV) and cyclic voltammetry (C.V) techniques, respectively. The modified CPE has good reproducibility, adequate catalytic activity, simple synthesis and stability of peak response during H2O2 oxidation on long run that exceeds many probes. Both reproducibility and stability for H2O2 detection are attributable to the PdNPs immobilized on the surface of p1,5-DAN/CPE. The modified CPE was used for determining H2O2 in real specimens with good stability, sensitivity, and reproducibility.

Validation of the efficiency of arsenic mitigation strategies in southwestern region of Bangladesh and development of a cost-effective adsorbent to mitigate arsenic levels

World's highest arsenic (As) contamination is well-documented for the groundwater system of southwestern region (mainly Jashore district) of Bangladesh, where the majority of inhabitants are underprivileged. To mitigate As poisoning in southwestern Bangladesh, numerous steps have been taken so far by the government and non-governmental organizations (NGOs). Among them, digging deep tube wells and As removal by naturally deposited Fe(OH)3 species are being widely practiced in the contaminated areas. However, these actions have been left unmonitored for decades, making people unaware of this naturally occurring deadly poison in their drinking water. Hence, water samples (n = 63, both treated and untreated) and soil samples (n = 4) were collected from different spots in Jashore district to assess the safety level of drinking water and to understand the probable reasons for high As(III) contamination. About 93.7% of samples were found to contain As(III) above 10 μg/L; among them, 38% contained above 50 μg/L. The study shows that current As(III) removal strategies in the study area are ineffective. In this connection, a simple low-cost As(III) removal adsorbent is proposed that can be prepared with very cheap and locally available materials like iron sludge and charcoal. The adsorbent was characterized in terms of SEM, EDX, and XPS. The optimal dosage of the adsorbent was investigated for real-life application concerning several vital water quality parameters. The Fe-C adsorbent exhibited a maximum As(III) removal efficiency of 92% in real groundwater samples. The study will allow policymakers for informed decision-making regarding water body management as well as enable the local people to avail As-safe water in a way that aligns with their economic factors.

Impedimetric sensing platform for sensitive carbendazim detection using MOCVD-synthesized copper graphene

Nanostructures of graphene were synthesized for electrochemical carbendazim (CBZ) fungicide detection via metal-organic chemical vapor deposition (MOCVD). The arduous process of graphene transfer is eliminated by this innovative approach to MOCVD graphene development. It also generates several defects and impurities and ultimately leads to the uniform deposition of graphene on SiO2/Si. SEM, EDX, and ICP-AES were used to assess the morphological properties and chemical composition of the materials. To obtain in-depth knowledge of the entire system, the electrochemical behavior was also investigated using voltammetric techniques and electrochemical impedance spectroscopy. The interaction of particles of copper with CBZ and the enhanced surface area of graphene, which causes a strong oxidation current, has been demonstrated to achieve the ideal CBZ sensing behavior. The electrode responded linearly at CBZ concentration levels of 1 to 50 nM, and the sensitivity of the sensing materials was estimated to be 0.0337 Ω nM-1. The statistical analysis validates the electrode's exceptional selectivity and remarkable reproducibility in determining CBZ.

Electrochemical Stability of Thiolate Self-Assembled Monolayers on Au, Pt, and Cu

Self-assembled monolayers (SAMs) of thiolates have increasingly been used for modification of metal surfaces in electrochemical applications including selective catalysis (e.g., CO₂ reduction, nitrogen reduction) and chemical sensing. Here, the stable electrochemical potential window of thiolate SAMs on Au, Pt, and Cu electrodes is systematically studied for a variety of thiols in aqueous electrolyte systems. For fixed tail-group functionality, the reductive stability of thiolate SAMs is found to follow the trend Au < Pt < Cu; this can be understood by considering the combined influences of the binding strength of sulfur and competitive adsorption of hydrogen. The oxidative stability of thiolate SAMs is found to follow the order: Cu < Pt < Au, consistent with each surface's propensity toward surface oxide formation. The stable reductive and oxidative potential limits are both found to vary linearly with pH, except for reduction above pH ∼10, which is independent of pH for most thiol compositions. The electrochemical stability across different functionalized thiols is then revealed to depend on many different factors including SAM defects (accessible surface metal atom sites decrease stability), intermolecular interactions (hydrophilic groups reduce the stability), and SAM thickness (stability increases with alkanethiol carbon chain length) as well as factors such as SAM-induced surface reconstruction and the ability to directly oxidize or reduce the non-sulfur part of the SAM molecule.

Facile fabrication of GCE/Nafion/Ni composite, a robust platform to detect hydrogen peroxide in basic medium via oxidation reaction

Nickel particles alone can oxidize hydrogen peroxide but confronts extreme stability problem which imparts a barrier to act as sensor. The porous Nafion bed on glassy carbon electrode (GCE) surface provides the sureness of incorporating of Ni particles which was further exploited as an electrochemical sensor for H₂O₂ detection through oxidative degradation process. The simple electrochemical incorporation of Ni particles along the pores of Nafion improves the stability of the sensor significantly. The oxidative pathway of hydrogen peroxide on GCE/Nafion/Ni was probed by analyzing mass transfer dependent linear sweep voltammograms both in static and rotating modes along with chronoamperometry. An electron transfer step determines the overall reaction rate with k°= 2.72 × 10^-4 cm s^-1, which is supported by the values of transfer coefficient (β) in between (0.68-0.75). Sensing performance was evaluated by recording differential pulse voltammograms (DPVs) with the linear detection limit (LOD) of 1.8 μM and linear dynamic range (LDR) of 5-500 μM. Real samples from industrial sources were successfully quantified with excellent reproducibility mark GCE/Nafion/Ni electrode as an applicable sensor.