Preparation of poly(diallyldimethylammonium chloride)-functionalized graphene and its applications for H2O2 and glucose sensing

An electrochemical sensor for the detection of arsenic using nanocomposite-modified electrode

The aim of this research is to develop an electrochemical sensor based on a conducting polymer, polyaniline, and a cationic polymer, poly(diallyldimethylammonium chloride), reinforced with graphene oxide nanosheets functionalized with acrylic acid. The two-dimensional nature of acrylic acid functionalized graphene oxide nanosheets and clusters made of conductive polymers and acrylic acid functionalized graphene oxide nanosheets were confirmed by microscopic tests. The prepared nanocomposite was deposited on the glassy carbon electrode in order to prepare an electrochemical sensor for the detection of arsenic by cyclic voltammetry and differential pulse voltammetry methods. It should be mentioned that the presence of acrylic acid functionalized graphene oxide nanosheets increases the surface area due to the nano size effect and better dispersion of this nanomaterial, poly(diallyldimethylammonium chloride), increases the adsorption capacity of the analyte due to electrostatic interaction between the negatively charged analyte and positively charged surface, and polyanilin increases the charge transfer rate due to the good conductivity. The results show that the prepared electrode has a sensitivity equal to 1.79 A/M with 0.12 μM as the detection limit. The proposed sensor could be used for the determination of total inorganic arsenic by first oxidative pretreatment for conversion of As(III) to As(V).

Label-Free, Highly Sensitive Electrochemical Aptasensors Using Polymer-Modified Reduced Graphene Oxide for Cardiac Biomarker Detection

Acute myocardial infarction (AMI), also recognized as a "heart attack," is one leading cause of death globally, and cardiac myoglobin (cMb), an important cardiac biomarker, is used for the early assessment of AMI. This paper presents an ultrasensitive, label-free electrochemical aptamer-based sensor (aptasensor) for cMb detection using polyethylenimine (PEI)-functionalized reduced graphene oxide (PEI-rGO) thin films. PEI, a cationic polymer, was used as a reducing agent for graphene oxide (GO), providing highly positive charges on the rGO surface and allowing direct immobilization of negatively charged single-strand DNA aptamers against cMb via electrostatic interaction without any linker or coupling chemistry. The presence of cMb was detected on Mb aptamer-modified electrodes using differential pulse voltammetry via measuring the current change due to the direct electron transfer between the electrodes and cMb proteins (Fe3+/Fe2+). The limits of detection were 0.97 pg mL-1 (phosphate-buffered saline) and 2.1 pg mL-1 (10-fold-diluted human serum), with a linear behavior with logarithmic cMb concentration. The specificity and reproducibility of the aptasensors were also examined. This electrochemical aptasensor using polymer-modified rGO shows potential for the early assessment of cMb in point-of-care testing applications.

Determination of Concentrated Hydrogen Peroxide Free from Oxygen Interference at Stainless Steel Electrode

H₂O₂ is frequently used at high concentrations in various applications. It is very challenging to detect high concentrations of H₂O₂ and to eliminate oxygen interference for H₂O₂ detection through electrochemical reduction. In the present investigation, the electrochemistry of H₂O₂ at stainless steel electrode has been carried out for the first time. A cathodic peak for H₂O₂ reduction was observed at about -0.40 V, and no cathodic peak for dissolved oxygen reduction was observed on type 304 stainless steel electrode. Amperometric determination of H₂O₂ on type 304 stainless steel electrode displayed a linear range from 0.05 up to 733 mM with a detection limit of 0.02 mM (S/N = 3) and a sensitivity of 16.7 μA mM^-1 cm^-2. The type 304 stainless steel electrode not only shows much higher upper limit than other reported electrodes for the detection of concentrated H₂O₂ but also is free from oxygen interference, which is of great importance for practical applications. This method could detect H₂O₂ in wound wash and lake water with excellent recoveries. Moreover, we successfully applied the stainless steel electrode to determine glucose using glucose oxidase to catalyze the oxidation of glucose to generate hydrogen peroxide. The linear range for glucose is between 0.5 and 25 mM, which covers clinically important blood glucose concentrations well.

A new voltammetry sensor platform for eriocitrin based on CoS2-MoS2-PDDA-GR nanocomposite

A novel electrochemically activated nanocomposite, CoS₂ Nanoparticles and MoS₂ Nanosheets decorated poly(diallyldimethylammonium chloride)-functionalized graphene (CoS₂-MoS₂-PDDA-GR), was successfully synthesized through a simple and low-cost method. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) techniques were used to characterize the nanocomposites. Based on the CoS₂-MoS₂-PDDA-GR nanocomposite modified glassy carbon electrode, the electrochemical properties of eriocitrin were investigated in detail and a sensitive determinative method was established synchronously. Compared with others, this sensor exhibited larger effective surface area, more reactive site and excellent voltammetric response for eriocitrin. Under optimum conditions by DPV, the oxidation peak currents responded to eriocitrin linearly over a concentration range from 2.0 × 10^-9 to 1.0 × 10^-6 mol L^-1 with a detection limit of 6.7 × 10^-10 mol L^-1 (S/N = 3). In addition, this fabricated sensor was successfully applied to detect eriocitrin in real samples with satisfactory results.

Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide as a multifunctional catalyst for H2O2 reduction, oxygen reduction and evolution reaction

This study describes a facile and effective route to synthesize hybrid material consisting of Co₃O₄ nanoparticles anchored on nitrogen-doped reduced graphene oxide (Co₃O₄/N-rGO) as a high-performance tri-functional catalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and H₂O₂ sensing. Electrocatalytic activity of Co₃O₄/N-rGO to hydrogen peroxide reduction was tested by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. Under a reduction potential at −0.6 V to H₂O₂, this constructing H₂O₂ sensor exhibits a linear response ranging from 0.2 to 17.5 mM with a detection limit to be 0.1 mM. Although Co₃O₄/rGO or nitrogen-doped reduced graphene oxide (N-rGO) alone has little catalytic activity, the Co₃O₄/N-rGO exhibits high ORR activity. The Co₃O₄/N-rGO hybrid demonstrates satisfied catalytic activity with ORR peak potential to be −0.26 V (vs. Ag/AgCl) and the number of electron transfer number is 3.4, but superior stability to Pt/C in alkaline solutions. The same hybrid is also highly active for OER with the onset potential, current density and Tafel slope to be better than Pt/C. The unusual catalytic activity of Co₃O₄/N-rGO for hydrogen peroxide reduction, ORR and OER may be ascribed to synergetic chemical coupling effects between Co₃O₄, nitrogen and graphene.

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.

Gold nanoparticles/Orange II functionalized graphene nanohybrid based electrochemical aptasensor for label-free determination of insulin

Nanocomposites, gold nanoparticles on Orange II functionalized graphene (AuNPs/O-GNs), were developed to modify the electrode surface for anchoring an insulin binding aptamer.

Redox mediated synthesis of hierarchical Bi2O3/MnO2 nanoflowers: a non-enzymatic hydrogen peroxide electrochemical sensor

Redox mediated synthesis of Bi₂O₃/MnO₂ nanoflowers for efficient electrochemical sensing of hydrogen peroxide down to 0.05 μM.

Decoration of GO with Fe spinel-Naf/DMAP: an electrochemical probe for sensing H2O2 reduction

We herein report the preparation of graphene oxide decorated with Fe spinel (Fe₃O₄)-Naf/DMAP for an unprecedented and highly selective non-enzymatic electrochemical sensing of hydrogen peroxide.

Sonoelectrochemical intercalation and exfoliation for the preparation of defective graphene sheets and their application as nonenzymatic H2O2 sensors and oxygen reduction catalysts

A sonoelectrochemical synthetic method is reported for rapidly preparing and dispersing reduced graphene nanosheets (RGN_SECM) stabilized in an aqueous electrolyte.

Hydrogen peroxide sensitive hemoglobin-capped gold nanoclusters as a fluorescence enhancing sensor for the label-free detection of glucose

A novel label-free fluorescent probe based on blue-emitting gold nanoclusters capped by hemoglobin for the direct detection of glucose is presented.

The nanoporous PdCr alloy as a nonenzymatic electrochemical sensor for hydrogen peroxide and glucose

The nanoporous PdCr alloy fabricated by one-step mild dealloying exhibits superior sensing performance and durability toward H₂O₂ and glucose compared to Pt/C and NP-Pd catalysts.