Cauliflower‐like Platinum Particles Decorated Reduced Graphene Oxide for Sensitive Determination of Acetaminophen

Over the past years, the development of electrochemical sensing platforms for the sensitive detection of drug molecules have received great interests. In this research study, we introduced cauliflower‐like platinum particles decorated reduced graphene oxide modified glassy carbon electrode (Pt?RGO/GCE) as an electrochemical sensing platform for highly sensitive determination of acetaminophen (ACTM). The sensor was prepared via a simple and environmentally friendly two‐step electrodeposition method at room temperature. The combination of conductive RGO nanosheets and unique structured Pt particles (average 232 nm in diameter) provided an efficient interface with large effective surface area which greatly facilitated the electron transfer of ACTM. The experimental conditions that might affect the drug detection were studied in detail and optimized for best performance. The Pt?RGO/GCE was able to detect ACTM up to the limit of 2.2 nM with a linear concentration range from 0.01 to 350 μM. With its high reproducibility, excellent stability and selectivity, the as‐fabricated sensor was successfully applied to the ACTM content measurement in commercial tablets.     

Electrochemical Behavior and Voltammetric Determination of Curcumin at Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of curcumin by using a electrochemically reduced graphene oxide (ERGO) modified glass carbon electrode (GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The electrochemical behaviors of curcumin at ERGO/GCE were investigated by cyclic voltammetry, suggesting that the ERGO/GCE exhibits excellent electrocatalytic activity towards curcumin, compared with bare GCE and GO/GCE electrodes. The electrochemical reaction mechanisms of curcumin, demethoxycurcumin and bisdemethoxycurcumin at the ERGO/GCE were also investigated and discussed systematically. Under physiological condition, the modified electrode showed linear voltammetric response from 0.2 μM to 60.0 μM for curcumin, with the detection limit of 0.1 μm. This work demonstrates that the graphene‐modified electrode is a promising strategy for electrochemical determination of biological important phenolic compounds.     

Pt‐Pd Bimetallic Nanoparticles Decorated Nanoporous Graphene as a Catalytic Amplification Platform for Electrochemical Detection of Xanthine

The nanoporous graphene papers (NGPs) was prepared by the hard‐template method. The Pt−Pd modified NGPs hybrid was prepared by the self‐assembly method. Then a glassy carbon electrode (GCE) modified with Pt−Pd bimetallic nanoparticles‐functionalized nanoporous graphene composite has been prepared for the electrochemical determination of Xanthine (XA). The Pt−Pd/NGPs hybrid was characterized by transmission electron microscopy, scanning electron microscope and X‐ray diffraction. The electrochemical behavior of XA on Pt−Pd/NGPs/GCE was investigated by cyclic voltammetry and amperometric i‐t. The Pt−Pd/NGPs modified electrode exhibited remarkably electrocatalytic activity towards the oxidation reaction of XA in phosphate buffer solution (pH=5.5). Under the optimal conditions, the determination of XA was accomplished by using amperometric i‐t, the linear response range from 1.0×10⁻⁵∼1.2×10⁻⁴ M. The detection limit was 3.0×10⁻⁶ M (S/N=3). The proposed modified electrode showed good sensitivity, selectivity, and stability with applied to determine XA in human urine.     

The Synthesis of Chitosan Decorated Reduced Graphene Oxide‐Ferrocene Nanocomposite and its Application in Electrochemical Detection Rhodamine B

Chitosan (CS) decorated reduced graphene oxide‐Ferrocene nanocomposite (RGO?Fc?CS) was synthesized by a one‐pot reaction. In the synthesis process of RGO?Fc?CS, GO?Fc was successfully self‐assembled via the π–π interaction, which had the features of large surface area and the high load. Then GO‐Fc and CS linked via one‐pot under alkaline conditions. The FT?IR, TGA, SEM were employed to characterize the successful synthesis of RGO?Fc?CS composites. A miniature electrochemical system was fabricated by RGO?Fc?CS modified glassy carbon electrode (expressed as RGO?Fc?CS/GCE) for the sensitive detection of RhB enantiomers via DPV. Electrochemical results revealed that the RGO?Fc?CS/GCE exhibited high molecular recognition toward RhB. Due to the synergy between the RGO?Fc and CS, the RGO?Fc?CS/GCE showed a linear range of 0.001–70 μM with a LOD of 0.5 nM, indicating that RGO?Fc?CS/GCE has broad application prospects to simplify monitor RhB real‐time.     

Fabrication of an electrochemical sensor based on the electrodeposition of Pt nanoparticles on multiwalled carbon nanotubes film for voltammetric determination of ceftriaxone in the presence of lidocaine, assisted by factorial-based response-surface methodology

A glassy carbon electrode (GCE) is modified with platinum nanoparticle (PtNPs) decorated multiwalled carbon nanotube (MWCNT). The modified electrode is applied for the determination of ceftriaxone (CFX) in the presence of lidocaine. Different methods were used to characterize the surface morphology of the modified electrode. The electrochemical behavior of CFX was investigated at GCE, MWCNT/GCE and PtNPs/MWCNT/GCE. A factorial-based response-surface methodology was used to find out the optimum conditions with minimum number of experiments. Under the optimized conditions, oxidation peak currents increased linearly with CFX concentration in the range of 0.01–10.00 μM with a detection limit of 9.01 nM. The results prove that the modified electrode is also suitable for the determination of CFX in pharmaceutical and clinical preparations.     

Voltammetric Determination of Folic Acid Using Adsorption of Methylene Blue onto Electrodeposited of Reduced Graphene Oxide Film Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of folic acid by adsorbing methylene blue onto electrodeposited reduced graphene oxide film modified glassy carbon electrode (MB/ERGO/GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The surface morphology of the MB/ERGO/GCE modified electrode was characterized using scanning electron microscopy, displays that both MB and ERGO distributed homogeneously on the surface of GCE. The MB/ERGO/GCE modified electrode shows more favorable electron transfer kinetics for potassium ferricyanide and potassium ferrocyanide probe molecules, which are important electroactive compounds, compared with bare GCE, MB/GCE, and ERGO/GCE. The electrochemical behaviors of folic acid at MB/ERGO/GCE were investigated by cyclic voltammetry, suggesting that the modified electrode exhibited excellent electrocatalytic activity towards folic acid compared with other electrodes. Under physiological condition, the MB/ERGO/GCE modified electrode showed a linear voltammetric response from 4.0 μM to 167 μM for folic acid, and with the detection limit of 0.5 μM (S/N=3). The stability, reproducibility and anti‐interference ability of the modified electrode were examined. The developed method has been successfully applied to determination of FA in tablets with a satisfactory recovery from 96 % to 100 %. The work demonstrated that the electroactive MB adsorbing onto graphene modified electrode showed an enhanced electron transfer property and a high resolution capacity to FA.     

A Self‐assembled L‐Cysteine and Electrodeposited Gold Nanoparticles‐reduced Graphene Oxide Modified Electrode for Adsorptive Stripping Determination of Copper

Glassy carbon electrode (GCE) modified with L‐cysteine and gold nanoparticles‐reduced graphene oxide (AuNPs‐RGO) composite was fabricated as a novel electrochemical sensor for the determination of Cu²⁺. The AuNPs‐RGO composite was formed on GCE surface by electrodeposition. The L‐cysteine was decorated on AuNPs by self‐assembly. Physicochemical and electrochemical properties of L‐cysteine/AuNPs‐RGO/GCE were characterized by scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, Raman spectroscopy, X‐ray diffraction, cyclic voltammetry and adsorptive stripping voltammetry. The results validated that the prepared electrode had many attractive features, such as large electroactive area, good electrical conductivity and high sensitivity. Experimental conditions, including electrodeposition cycle, self‐assembly time, electrolyte pH and preconcentration time were studied and optimized. Stripping signals obtained from L‐cysteine/AuNPs‐RGO/GCE exhibited good linear relationship with Cu²⁺ concentrations in the range from 2 to 60 μg L⁻¹, with a detection limit of 0.037 μg L⁻¹. Finally, the prepared electrode was applied for the determination of Cu²⁺ in soil samples, and the results were in agreement with those obtained by inductively coupled plasma mass spectrometry.     

Highly Selective and Sensitive Voltammetric Sensor Based on Ruthenium Nanoparticle Anchored Calix[4]amidocrown‐5 Functionalized Reduced Graphene Oxide: Simultaneous Determination of Quercetin,Morin and Rutin in Grape Wine

In this report, ruthenium nanoparticles (RuNPs) and calix[4]amidocrown‐5 (C4A5) were synthesized and grafted onto the surface of reduced graphene oxide (RGO) nanocomposite (RuNPs/C4A5/RGO). The morphologies of the nanocomposites were characterized by transmission electron microscope, scanning electron microscope, atomic force microscope, electrochemical impedance spectroscopy and x‐ray photoelectron spectroscopy. The electrochemical experiments were performed by cyclic voltammetry, electrochemical impedance spectroscopy and square wave voltammetry. The simultaneous determination of quercetin, rutin and morin was performed on glassy carbon electrode modified with RuNPs/C4A5/RGO (RuNPs/C4A5/RGO/GCE). The linearity ranges and the detection limits of QR, RT and MR were 1.0×10^?10–1.0×10^?8 M and 2.0×10^?11 M respectively.     

Synthesis of graphene oxide nanosheet: A novel glucose sensor based on nickel-graphene oxide composite film

The graphene oxide (GO) nanosheets were produced by chemical conversion of graphite, and were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR). An electrochemical sensor based on Ni/graphene (GR) composite film was developed by incorporating Ni²⁺ into the graphene oxide film modified glassy carbon electrode (Ni/GO/GCE) through the electrostatic interactions with negatively charged graphene oxide. The Ni²⁺/graphene modified glassy carbon electrode (Ni/GR/GCE) was prepared by cyclic voltammetric scanning of Ni/GO/GCE in the potential range from ?1.5 to 0.2 V at 50 mV s^?1 for 5 cycles. The electrochemical activity of Ni/GR/GCE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni/GR/GCE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. The introduction of conductive graphene not only greatly facilitates the electron transfer of Ni²⁺, but also dramatically improves the long-term stability of the sensor by providing the electrostatic interactions. Ni/GR/GCE also shows good electrocatalytic activity toward the oxidation of glucose. The Ni/GR/GCE gives a good linear range over 10 to 2700 μM with a detection limit of 5 μM towards the determination of glucose by amperometry. This sensor keeps over 85% activity towards 0.1 mM glucose after being stored in air for a month, respectively. Furthermore, the modified sensor was successfully applied to the sensitive determination of glucose in blood samples.     

Platinum Nanoparticles/Poly(isoleucine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Hydroquinone and Catechol

A new electrochemical sensor based on Poly(Isoleucine) modified glassy carbon electrode decorated with platinum nanoparticles (Pt/Poly(Isoleucine)/GCE) was developed for sensitive individual and simultaneous determination of hydroquinone (HQ) and catechol (CC). Scanning electron microscopy (SEM), Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) were performed in order to characterize the Pt/Poly(Isoleucine)/GCE nanocomposite. For simultaneous determination of HQ and CC, Pt/Poly(Isoleucine)/GCE showed wide linear range between the 0.01–100.0 μM. The detection limits were 0.006 μM for HQ and 0.005 μM for CC. The Pt/Poly(Isoleucine)/GC electrode exhibited good sensitivity and reliability in the simultaneous electroanalysis of two isomers in PBS of pH 7.5. The modified electrode was used to detect the isomers in naturel samples.     

Prussian Blue Nanoparticles Self Assembling on Electrochemically Reduced Graphene Oxide Modified GC Electrode for Sensitive Hydrogen Peroxide Detection

A facile, fast, and convenient route was suggested for the fabrication of Prussian blue nano particles (PBNPs) assembled on reduced graphene oxide (RGO) modified glassy carbon electrode (PBNPs|RGO|GCE). RGO was electrodeposited on the surface of GCE and the prepared RGO|GCE was immersed into a ferric‐hexacyanoferrate(III) solution and PBNPs were assembled on the RGO|GCE for a certain period of time. The PBNPs film thickness can be easily controlled by adjusting the assembling duration. The developed PBNPs|RGO|GCE was successfully used for determining hydrogen peroxide, with a linear response over the concentration range 0.5‐400 μM, a good accuracy and precision, detection limit 0.44 μM, and sensitivity 1168 mA M^?1 cm^?2.     

Investigation of Methanol Behavior at the Designed Electrochemical Sensor based on Ni(II) Complex and Graphene Nanosheets

In this work, the electrochemical oxidation of methanol was investigated by different electrochemical methods at a carbon paste electrode (CPE) modified with (N‐5‐methoxysalicylaldehyde, N´‐2‐hydroxyacetophenon‐1, 2 phenylenediimino nickel(II) complex (Ni(II)–MHP) and reduced graphene oxide (RGO), which is named Ni(II)‐MHP/RGO/CPE, in an alkaline solution. This modified electrode was found to be efficient for the oxidation of methanol. It was found that methanol was oxidized by the NiOOH groups generated by further electrochemical oxidation of nickel(II) hydroxide on the surface of the modified electrode. Under optimum conditions, some parameters of the analyte (MeOH), such as the electron transfer coefficient (α), the electron transfer rate constant) k_s), and the diffusion coefficient of species in a 0.1 M solution (pH = 13), were determined. The designed sensor showed a linear dynamic range of 2.0–100.0 and 100.0–1000.0 μM and a detection limit of 0.68 μM for MeOH determination. The Ni(II)‐MHP/RGO/CPE sensor was used in the determination of MeOH in a real sample.     

Sensitive Voltammetric Determination of Baicalein at Thermally Reduced Graphene Oxide Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of the flavonoid baicalein by using a thermally reduced graphene oxide (TRGO) modified glassy carbon electrode (GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The surface morphology and structure of TRGO investigated by atomic force microscopy, FT‐IR spectroscopy and Raman spectroscopy reveal that the TRGO prepared maintained as single or bilayer sheets and with significant edge‐plane‐like defect sites. The TRGO/GCE modified electrode shows more favorable electron transfer kinetics for potassium ferricyanide and potassium ferrocyanide probe molecules, which are important electroactive compounds, compared with bare GCE and GO/GCE electrodes. The electrochemical behaviors of baicalein at the TRGO/GCE were investigated by cyclic voltammetry, suggesting that the TRGO/GCE exhibits excellent electrocatalytic activity to baicalein. Under physiological conditions, the modified electrode showed linear voltammetric response from 10 nM to 10 µM for baicalein, with a detection limit of 6.0 nM. This work demonstrates that the graphene‐modified electrode is a promising tool for electrochemical determination of flavonoid drugs.     

Fabrication of Trimetallic Pt−Pd−Co Porous Nanostructures on Reduced Graphene Oxide by Galvanic Replacement: Application to Electrocatalytic Oxidation of Ethylene Glycol

In present work, reduced graphene oxide nanosheets (rGO) decorated with trimetallic three‐dimensional (3D) Pt−Pd−Co porous nanostructures was fabricated on glassy carbon electrode (Pt−Pd−Co/rGO/GCE). First, GO suspension was drop‐casted on the electrode surface, then GO film reduction was carried out by cycling the potential in negative direction to form the rGO film modified GCE (rGO/GCE). Then, electrodeposition of the cobalt nanoparticles (CoNPs) as sacrificial seeds was performed onto the rGO/GCE by using cyclic voltammetry. Afterward, Pt−Pd−Co 3D porous nanostructures fabrication occurs through galvanic replacement (GR) method based on a spontaneous redox process between PtCl₂, PdCl_2, and CoNPs. The morphology and structure of the Pt−Pd−Co/rGO porous nanostructure film was characterized by scanning electron microscopy, energy dispersive spectroscopy and X‐ray diffraction method. The performance of the prepared electrode was investigated by various electrochemical methods including, cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic activity of the as‐prepared modified electrode with high surface areas was evaluated in anodic oxidation of ethylene glycol. The study on electrocatalytic performances revealed that, in comparison to various metal combinations in modified electrodes, trimetallic Pt−Pd−Co/rGO/GCE exhibit a lower onset potential, significantly higher peak current density, high durability and stability for the anodic oxidation of ethylene glycol. The excellent performances are attributed to the rGO as catalysts support and resulting synergistic effects of the trimetallic and appropriate characteristics of the resulted 3D porous nanostructures. Moreover, the influence of various concentrations of ethylene glycol, the potential scan rate and switching potential on the electrode reaction, in addition, long‐term stability have been studied by chronoamperometric and cyclic voltammetric methods.     

Selective and Simultaneous Determination of Dihydroxybenzene Isomers Based on Green Synthesized Gold Nanoparticles Decorated Reduced Graphene Oxide

In the present study, we report the simultaneous electrochemical determination of hydroquinone (HQ), catechol (CC) and resorcinol (RC) at gold nanoparticles (Au‐NPs) decorated reduced graphene oxide (RGO) modified electrode. An enhanced and well defined peak current response with a better peak separation of HQ, CC and RC is observed at RGO/Au‐NPs composite than that of RGO and Au‐NPs modified electrodes. The fabricated modified electrode shows a wide linear response in the concentration range of 3–90 µM, 3–300 µM and 15–150 µM for HQ, CC and RC, respectively. The detection limit of HQ, CC and RC is found as 0.15 µM, 0.12 µM and 0.78 µM, respectively.     

Fabrication of Cu−CeO2 Coated Multiwall Carbon Nanotube Composite Electrode for Simultaneous Determination of Guanine and Adenine

A copper nano particles and cerium (IV) oxide modified carbon nanotube based composite on glassy carbon electrode (Cu−CeO₂/MWCNT/GCE) was fabricated for simultaneous determination of guanine and adenine. The surface morphology, chemistry and conductance of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy dispersion X‐ray (EDX), X‐Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The Cu−CeO₂/MWCNT/GCE improved electrochemical behaviour of guanine and adenine compared to other electrodes. The modified electrode was also used for individual and simultaneous determination of guanine and adenine. Under optimized conditions, the calibration curves were obtained linearly in the range of 0.20 to 6.00 μM for the guanine and 0.10 to 8.0 μM for the adenine by differential pulse voltammetry. The limits of detection of guanine and adenine were calculated as 0.128 and 0.062 μM, respectively. Interferences studies were also performed in the presence of inorganic and organic compounds. Moreover, the determination of guanine and adenine contents were carried out in a calf thymus DNA sample by the developed method with satisfactory results.     

Electrochemical Sensor Based on a Novel Pt−Au Bimetallic Nanoclusters Decorated on Reduced Graphene Oxide for Sensitive Detection of Ofloxacin

Pt−Au nanoclusters decorated on the surface of reduced graphene oxide (rGO/Pt−Au) was facilely prepared by one‐pot electrochemical reduction. The morphology and composition of rGO/Pt−Au composites had been characterized by scanning electron microscopy (SEM) coupled with energy‐dispersive X‐ray spectrometry (EDX), fourier transform‐infrared spectroscopy (FT‐IR) and electrochemical methods. Ofloxacin is a member of synthetic quinolones which has been widely used for the treatment of common diseases in humans and animals. The performance of the rGO/Pt−Au nanocomposite toward the oxidation of ofloxacin was compared with the other similar nanostructures like rGO/Pt and rGO/Au. In the optimized conditions, two linear calibration curves were obtained, from 0.08 to 10 μM and 10 to 100 μM ofloxacin. A detection limit of 0.05 μM ofloxacin was observed at pH 5.7 for the GCE/rGO/Pt−Au. The proposed sensor was successfully applied to determine ofloxacin in tablets and human urine samples and the results were satisfactory.     

Design of a Sensitive Electrochemical Sensor Based on Ferrocene-reduced Graphene Oxide/Mn-spinel for Hydrazine Detection

Herein, we report construction of a ferrocene-reduced graphene oxide-Mn spinel modified glassy carbon electrode (Fc−G/Mn₃O₄/GCE) as a sensitive electrochemical probe for hydrazine detection via its oxidation. The synergistic effect of ferrocene, graphene oxide and Mn₃O₄ provides it a great electrocatalytic effect. The electrochemical investigations of Fc−G/Mn₃O₄/GCE were studied using cyclic voltammetry, while differential pulse voltammetry was utilized for recording the electrocatalytic sensing of hydrazine. The prepared Fc−G/Mn₃O₄ offers a platform for sensitive and selective detection of low-level hydrazine in two linear ranges from 0.045 to 108 μM and 108 to 653 μM with limit of detection 8.5 nM. Real sample analysis was also performed in local industrial water samples with satisfactory recovery results.     

Underpotential Deposition Preparation of Pt‐loading AuNPs/Reduced Graphene Oxide and Its Catalytic Detection of Catechol

Ultralow Pt‐loading Au nanoparticles have been fabricated on the surface of reduced graphene oxide (RGO) by using underpotential deposition (UPD) monolayer redox replacement process. The Pt/Au/RGO modified electrode exhibits an excellent electrocatalytic activity toward catechol and hydroquinone. Under the optimized condition, the separation of peak‐to‐peak between hydroquinone and catechol is 197 mV, which is wide enough to distinguish the isomers of benzenediol. Catechol is detected by the Pt/Au/RGO/GCE with a low detection limit in the presence of hydroquinone.     

Electrochemical Preparation of Yttrium Hexacyanoferrate on Reduced Graphene Oxide and Its Application to Analgesic Drug Sensor

Herein, we report a template free and surfactant less electrochemical approach for the preparation of flower‐like yttrium hexacyanoferrate (YHCF) particles on reduced graphene oxide (RGO) modified glassy carbon electrode (GCE). The morphology of YHCF particles has been controlled by varying the molar ratio of Y(NO₃)₂ and K₃Fe(CN)₆ for the first time. The surface morphology of as‐prepared RGO/YHCF composite was characterized using SEM, EDX, IR and XRD methods. The electrocatalytic activity of the RGO/YHCF composite modified GCE towards Paracetamol (PA) oxidation has been investigated by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Besides, the practical feasibility of the fabricated modified GCE has been demonstrated through the determination of PA from commercially purchased Paracetamol tablets.