Glassy carbon electrodes modified with hemin-carbon nanomaterial films for amperometric H2O2 and NO2− detection

Highly active iron-nitrogen-boron-carbon bifunctional electrocatalytic platform for hydrogen peroxide sensing and oxygen reduction

An iron-nitrogen-boron-carbon (Fe-N-B-C) bifunctional electrocatalyst was prepared by means of a facile one-step hydrothermal reduction of graphene oxide using dimethylamine borane as doping agent. In addition, hemins were efficiently anchored during doping/reducing process on this modified graphene. The as-prepared Fe-N-B-C electro-catalyst showed enhanced response as regards its potential for reduction of H₂O₂ and O₂. In view of its catalytic activity, this Fe-N-B-C material was tested for the determination of H₂O₂ with a chronoamperometry method, obtaining a detection limit as low as 0.055 μM, which is better than that of some Hemin-N-C materials. Regarding O₂ reduction reaction, a study performed using a rotating disk electrode indicated that this material exhibits a positive onset potential (0.90V vs. RHE), high selectivity (4e^- process), high limiting-current density (4.75 mA cm^-2) and strong resistance against the crossover-effect from methanol in alkaline medium, making it to be the promising candidate as alternative for commercial Pt/C catalysts. These results could have commercial and environmental relevance and would deserve further complementary investigation.

Detection Technologies for Reactive Oxygen Species: Fluorescence and Electrochemical Methods and Their Applications

Reactive oxygen species (ROS) have been found in plants, mammals, and natural environmental processes. The presence of ROS in mammals has been linked to the development of severe diseases, such as diabetes, cancer, tumors, and several neurodegenerative conditions. The most common ROS involved in human health are superoxide (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH). Organic and inorganic molecules have been integrated with various methods to detect and monitor ROS for understanding the effect of their presence and concentration on diseases caused by oxidative stress. Among several techniques, fluorescence and electrochemical methods have been recently developed and employed for the detection of ROS. This literature review intends to critically discuss the development of these techniques to date, as well as their application for in vitro and in vivo ROS detection regarding free-radical-related diseases. Moreover, important insights into and further steps for using fluorescence and electrochemical methods in the detection of ROS are presented.

Synthesis and utilization of Co3O4 doped carbon nanofiber for fabrication of hemoglobin-based electrochemical sensor

In this paper cobalt oxide (Co₃O₄) nanoparticles were mixed with polyacrylonitrile to prepare Co₃O₄ doped carbon nanofiber (CNF) composite by electrospinning and carbonization, which was further used to modify on carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on Co₃O₄-CNF/CILE surface with Nafion acted as the protective film to fabricate an electrochemical biosensor (Nafion/Hb/Co₃O₄-CNF/CILE). Electrochemical behavior of Hb on the electrode was investigated with a pair of quasi-reversible redox peak appeared on cyclic voltammogram and electrochemical parameters were calculated. Moreover, this biosensor had good analytical capabilities for electrocatalytic reduction of different substrates including trichloroacetic acid, potassium bromate and sodium nitrite with wider detection range from 40.0 to 260.0 mmol L^-1, 0.1 to 48.0 mmol L^-1 and 1.0 to 12.0 mmol L^-1 by cyclic voltammetry, respectively. The proposed method showed excellent anti-interferences ability with good selectivity and was successful used for quantitative detection of real samples, which displayed the potential applications to develop into a new analytical device.

Sinusoidal voltage electrodeposition of PEDOT-Prussian blue nanoparticles composite and its application to amperometric sensing of H2O2 in human blood

A selective electrochemical sensor based on poly(3,4-ethylenedioxythiophene) (PEDOT) - Prussian blue nanoparticles (PBNPs) for hydrogen peroxide (H₂O₂) determination was prepared by innovative sinusoidal voltage (SV) method. The successful incorporation of citrate-stabilized PBNPs into PEDOT matrix was confirmed by energy dispersive X-ray analysis (EDX), Raman spectroscopy, UV-Vis spectroelectrochemistry and cyclic voltammetry measurements. The SV preparation method provides a PEDOT-PBNPs coating with rough surface morphology and good electrocatalytic activity toward H₂O₂ reduction. The amperometric response of PEDOT-PBNPs-based sensor at -50 mV vs. Ag/AgCl is linear within the range of concentrations from 5 μM to 1 mM H₂O₂ with a detection limit of 1.4 μM H₂O₂. The proposed Pt/PEDOT-PBNPs sensor displays good repeatability, reproducibility, operational stability as well as good selectivity toward H₂O₂ determination in the presence of interfering species like dopamine (DA), uric acid (UA), KNO₂ glucose (Glu), KNO₃ and ascorbic acid (AA), and was successfully applied to H₂O₂ determination in human blood samples without biofouling.

Fabrication of novel metal-free "graphene alloy" for the highly efficient electrocatalytic reduction of H2O2

Hydrogen peroxide (H₂O₂) is becoming significant due to its extensive applications, so determination of H₂O₂ is very important topic in analytical chemistry. Metal-free "graphene alloy" - nitrogen (N) and sulfur (S) heteroatoms co-doped reduced graphene oxide (NS-rGO) was produced via a simple one-step thermal annealing procedure using a mixture of 5-amino-2-mercapto-1,3,4-thiadiazole (AMT) and graphene oxide (GO). The obtained metal-free NS-rGO composite showed better electrocatalytic activity toward the reduction of H₂O₂ compared with the reduced graphene oxide (rGO). The enhanced performance was caused by the synergistic effect of N and S co-doping. Under optimum conditions, the constructed sensor demonstrated a linear response to H₂O₂ in the range of 7-18000μM, with a lower detection limit of 0.45μM (S/N=3), even better than some reported sensors based on noble metal nanoparticles. Moreover, the proposed sensor exhibited excellent analytical performance in terms of acceptable selectivity, excellent reproducibility and long-time stability. These results indicated that the NS-rGO composite was a promising metal-free electrocatalytic material for constructing H₂O₂ sensors. Additionally, NS-rGO composite was expected to be applied as catalysts for fuel cell applications, even for applications beyond fuel cells.

Large mesoporous carbons decorated with silver and gold nanoparticles by a self-assembly method: enhanced electrocatalytic activity for H2O2 electroreduction and sodium nitrite electrooxidation

The silver, gold nanoparticles were grown onto poly (diallyldimethyl ammoniumchloride, PDDA)-functionalized large mesoporous carbon (LMC) by simple self-assembly method. AuNPs or AgNPs/PDDA–LMC show superior electrocatalytic activity.