Search

Holey graphenic nanomaterials with porosity within the basal plane attract significant interest. It is observed that the perforation of graphene can enhance the specific surface area of the nanosheet, ensuring effective wetting and penetration of electrolytes to the electrode surface, facilitating rapid charge transfer, and boosting the electrocatalytic efficacy of the transducers. This study reports the first example of nitrogen-doped holey reduced graphene oxide with a mesoporous morphology of the graphene basal plane (N-MHG). It is shown that N-MHG can be synthesized through a one-step hydrothermal treatment of GO using NH 3 and H 2 O 2 . A straightforward procedure for the purification of N-MHG has also been developed. AFM, TEM, and Raman analyses have revealed that N-MHG possesses a highly mesoporous network structure with a pore size ranging from 10 to 50 nm. X-ray photoelectron spectroscopy data have indicated a partial reduction of the graphene oxide sheets during the etching process but also show a 3-5 times higher content of C═O and O-C═O fragments compared to rGO. This could account for the remarkable stability of the N-MHG aqueous suspension. An electrochemical sensor for dopamine analysis is assembled on a glassy carbon electrode with N-MHG/Nafion membrane and characterized by cyclic voltammetry and electrochemical impedance spectroscopy., (© 2024 Wiley‐VCH GmbH.)

This study presents the first insights into vinpocetine (VIN) behavior, a nootropic compound, on a glassy carbon electrode (GCE). Cyclic voltammetry (CV) revealed an irreversible oxidation peak at +1.0 V ( vs. Ag/AgCl), with pH dependency indicating proton involvement in the electrochemical reaction. Density functional theory (DFT) optimized VIN's molecular geometry, while Fukui functions and dual descriptors elucidated its reactivity for a more straightforward exploration of the complete electrooxidation mechanism. Differential pulse voltammetry (DPV) demonstrated VIN sensing capabilities within a concentration range of 0.20 to 12.8 mg L -1 , with a theoretical limit of detection (LOD) at 0.07 mg L -1 , using optimized conditions of supporting electrolyte. The method showed selectivity in the presence of excipients and interfering species commonly found in pharmaceutical formulations. Recovery tests yielded 95.5% ( n = 3), and quantification in pharmaceutical formulations showed no significant differences compared to the reference method based on HPLC DAD. This novel electroanalytical method holds promise for VIN nootropic sensing and routine pharmaceutical analysis.

Ultrasensitive electroanalytical monitoring of interleukin-6 levels in serum samples has emerged as a valuable tool for the early diagnosis of inflammatory diseases. Despite its advantages, there is a lack of strategies for the label-free voltammetric determination of cytokines. Here, a novel chitosan/genipin modified fluorine tin oxide electrode was developed providing an in-situ hydrogel formation (FTO/CSG). This platform was applied for the detection of interleukin-6, a major pro-inflammatory cytokine. Transmission electron microscopy (TEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) indicated genipin serves as an efficient green cross-linker to build the immunosensing platform (FTO/CSG/anti-IL-6). EIS showed an increase in charge transfer resistance from 326 to 1360 kΩ after the immobilization of anti-IL-6 antibodies. By square wave voltammetry, this method achieved a detection limit of 0.03 pg mL -1 with a wide linear range of 0.05-1000 pg mL -1 . Additionally, it displayed a high selectivity index when tested in the presence of three inflammatory cytokines as interfering proteins: IL-12, IL-1β, and TNF-α. The sample matrix effect showed a peak current variation lower than 5 %. The novel method was applied for the quantification of IL-6 in serum samples of septic mice. No statistical differences were observed between the standard ELISA and the proposed method using a confidence level of 95 %., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

The synthesis and characterization of a novel titania/silica hybrid xerogel subsequently modified with 4-methylpyridine (4-Pic), named TiSi4Pic + Cl -  is reported. The physicochemical, structural and thermal properties of TiSi4Pic + Cl - were characterized using several techniques. Anchoring cobalt(II) phthalocyanine (CoTsPc) in TiSi4Pic + Cl - showed greater electroanalytical sensitivity over other sensors built with these materials. A novel electroanalytical method was developed to quantify the noxious biocide pentachlorophenol (PCP) for environmental monitoring. The peak current intensity increased linearly with the analyte concentration in the range between 0.99 and 4.21 μmol L -1 , based on the oxidation process (at + 0.81 V, vs. Ag/AgCl) of differential pulse voltammetry (DPV). The estimated limit of detection (LOD) was 29 nmol L -1 . Recovery tests in environmental samples showed a PCP concentration of 2.05 ± 0.03 μmol L -1 (n = 3). The method was statistically validated by comparing the PCP concentrations with those obtained by molecular absorption spectrometry and high-performance liquid chromatography-diode array detection (HPLC-DAD). At a 95% confidence level, no difference between the results was found, therefore confirming the excellent accuracy of the proposed method., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Phenylurea herbicides are persistent contaminants, which leads their transport to the surface and ground waters, affecting human and aquatic organisms. Different analytical methods have been reported for the detection of phenylureas; however, several of them are expensive, time-consuming, and require complex pretreatment steps. Here, we show a simple method for the simultaneous electrochemical determination of two phenylurea herbicides by differential pulse adsorptive stripping voltammetry (DPAdSV) using a modified platinum/chitosan electrode. The one-step synthesized platinum/chitosan PtNPs/CS was successfully characterized by TEM, XRPD, and FT-IR, and applied through the sensing platform designated as PtNPs/CS/GCE. This bio-based modified electrode is proposed for the first time for the individual and/or simultaneous electrochemical detection of the phenylurea herbicides diuron and isoproturon compounds extensively used worldwide that present a very similar chemical structure. Electrochemical and interfacial characteristics of the modified electrode were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the oxidation mechanism of diuron and isoproturon occurs in two different pathways, with a peak-to-peak definition of ca. 0.15 V. Under differential pulse adsorptive stripping voltammetry (DPAdSV) optimized conditions, the limit of detection (LOD) was estimated as 7 μg L -1 for isoproturon and 20 μg L -1 for diuron (E d  = +0.8 V; t d  = 100 s). The proposed method was successfully applied to the determination of both analytes in river water samples, at three different levels, with a recovery range of 90-110%. The employment of the bio-based sensing platform PtNPs/CS/GCE allows a novel and easy analytical method to the multi-component phenylurea herbicides detection., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Determination of Se(IV) and Se(VI) in high saline media was investigated by cathodic stripping voltammetry (CSV). The voltammetric method was applied to assay selenium in seawater, hydrothermal and hemodialysis fluids. The influence of ionic strength on selenium determination is discussed. The CSV method was based on the co-electrodeposition of Se(IV) with Cu(II) ions and Se(VI) determined by difference after sample UV-irradiation for photolytic selenium reduction. UV-irradiation was also used as sample pre-treatment for organic matter decomposition. Detection limit of 0.030 microg L(-1) (240 s deposition time) and relative standard deviation (RSD) of 6.19% (n=5) for 5.0 microg L(-1) of Se(IV) were calculated. Linear calibration range for selenium was observed from 1.0 to 100.0 microg L(-1). Concerning the pre-treatment step, best results were obtained by using 60 min UV-irradiation interval in H(2)O(2)/HCl medium. Se(VI) was reduced to the Se(IV) electroactive species with recoveries between 91.7% and 112.9%. Interferents were also investigated.

A multivariate calibration model (PLS) was developed for the simultaneous spectrophotometric determination of Al(III) and Fe(III) in post-hemodialysis fluids with pyrocathecol violet (PCV) as chromogenic reagent. The analytes build stable complexes with PCV in presence of hexamine buffered medium at pH 6.1. The complexes show overlapped absorption bands in the spectral range of 220-800nm so that absorptions of 580 wavelengths were necessary for the calibrations. Determinations of Al(III) and Fe(III) were done without masking agents. The best calibration model was obtained by using PLS-1 regression with three components after data mean centering. The spectrophotometric method applied to assay the analytes in real post-hemodialysis samples containing no desferrioxamine B presented good agreement with voltammetric measurements used as reference. Concentrations ranging from 0.20 to 0.60mgL(-1) for Al(III) and for Fe(III) were determined in real samples. The multivariate detection limits for Al(III) and Fe(III) were 0.044 and 0.052mgL(-1), respectively, and the calculated values of sensitivity were 6.33 for Al(III) and 3.44 for Fe(III). The proposed method showed to be straightforward and useful to follow the hemodialysis progress for patients under treatment. Interferents were also investigated.