High Performance Non‐enzymatic Glucose Sensor Based on One‐Step Electrodeposited Nickel Sulfide

Nanostructured NiS thin film was prepared by a one‐step electrodeposition method and the structural, morphological characteristics of the as‐prepared films were analyzed by X‐ray diffractometry (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X‐ray analysis (EDAX). The electrocatalytic activity of NiS thin film towards glucose oxidation was investigated by fabricating a non‐enzymatic glucose sensor and the sensor performance was studied by cyclic voltammetry (CV) and amperometry. The fabricated sensor showed excellent sensitivity and low detection limit with values of 7.43 μA μM ^?1 cm^?2 and 0.32 μM , respectively, and a response time of <8 s.     

Sensitive Voltammetric Determination of Bisphenol A Based on a Glassy Carbon Electrode Modified with Copper Oxide‐Zinc Oxide Decorated on Graphene Oxide

A highly sensitive and selective chemical sensor was prepared based on metallic copper‐copper oxides and zinc oxide decorated graphene oxide modified glassy carbon electrode (Cu?Zn/GO/GCE) through an easily electrochemical method for the quantification of bisphenol A (BPA). The composite electrode was characterized via scanning electron microscopy (SEM), X‐Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of BPA in Britton‐Robinson (BR) buffer solution (pH 7.1) was examined using cyclic voltammetry (CV). Under optimized conditions, the square wave voltammetry (SWV) response of Cu?Zn/GO/GCE towards BPA indicates two linear relationships within concentrations (3.0 nmol L^?1?0.1 μmol L^?1 and 0.35 μmol L^?1?20.0 μmol L^?) and has a low detection limit (0.88 nmol L^?1). The proposed electrochemical sensor based on Cu?Zn/GO/GCE is both time and cost effective, has good reproducibility, high selectivity as well as stability for BPA determination. The developed composite electrode was used to detect BPA in various samples including baby feeding bottle, pacifier, water bottle and food storage container and satisfactory results were obtained with high recoveries.     

Electrochemical Determination of Uric Acid Using a Multiwalled Carbon Nanotube Platinum–Nickel Alloy Glassy Carbon Electrode

Platinum–nickel nanoparticles were synthesized by a reduction procedure. The Pt–Ni/C composite was characterized by X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and electrochemical analysis. The measurements show that the Pt–Ni/multiwalled carbon nanotubes provided higher electrocatalytic activity for the oxidation of uric acid than Pt–Ni/carbon black. The sensor prepared from the characterized material provided a long linear dynamic range from 0.1 to 240.4?µM with a detection limit of 0.03?µM and a sensitivity of 41.21?µA?mM^?1?cm^?2. The reported modified electrode also provided excellent selectivity, good stability, and satisfactory reproducibility for the determination of uric acid.     

Synthesis of Ag Nanoparticle Doped MnO2/GO Nanocomposites at a Gas/Liquid Interface and its Application in H2O2 Detection

Ag/MnO₂/GO nanocomposites were synthesized via the method of gas/liquid interface based on silver mirror reaction, and a non‐enzymatic H₂O₂ sensor was fabricated through immobilizing Ag/MnO₂/GO nanocomposites on GCE. The composition and morphology of the nanocomposites were studied by energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Electrochemical investigation indicated that it exhibited a favorable performance for the H₂O₂ detection. Its linear detection range was from 3 μM to 7 mM with a correlation coefficient of 0.9960; the sensitivity was 105.40 μA mM^?1 cm^?2 and the detection limit was estimated to be 0.7 μM at a signal‐to‐noise ratio of 3.     

One‐Step Electrodeposition of NiCo2S4 Nanosheets on Patterned Platinum Electrodes for Non‐Enzymatic Glucose Sensing

The preparation of NiCo₂S₄ (NCS) nanosheets on photolithographically patterned platinum electrodes by electrodeposition was explored. The as‐prepared nanosheets were systematically characterized by field‐emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy techniques. The NCS‐modified Pt electrode was used as a non‐enzymatic glucose sensor. The sensor response exhibited two linear regions in glucose concentration, with a limit of detection of 1.2 μm . The sensors showed that the as‐prepared NCS nanosheets have excellent electrocatalytic activity towards glucose with long stability, good reproducibility, and excellent anti‐interference properties, and thus, this material holds promise for the development of a practical glucose sensor.     

Functionalization of Graphene Oxide with 3‐Mercaptopropyltrimethoxysilane and Its Electrocatalytic Activity in Aqueous Medium

In this work, a highly dispersed graphene oxide (GO) was successfully functionalized with 3‐mercaptopropyltrimethoxysilane (MPTS) molecule by silanization method. The chemically generated GO and MPTS functionalized GO (MPTS‐GO) were structurally characterized by thermogravimetric analysis (TGA), X‐ray diffraction analysis (XRD), scanning electron microscope (SEM), energy dispersive X‐ray (EDAX), fourier transform infrared spectroscopy (FT‐IR) and ultraviolet visible spectroscopy (UV‐Vis) techniques. The MPTS‐GO is highly suspensable in water. The thermal and conductivity results for MPTS‐GO are significantly increased compared to GO. Moreover, glassy carbon electrode modified with MPTS‐GO hybrid (MPTS‐GO/GCE) was prepared by casting of the MPTS‐GO solution on GCE. The MPTS‐GO/GCE showed an excellent electrocatalytic activity towards methionine (Met). This was understood from the observed less positive oxidation potential and higher oxidation current when compared to bare GC electrode. The MPTS‐GO has excellent electrocatalytic activity, making it an ideal candidate for sensor applications.     

Fabrication of Electrochemical Sensor Based on CeO2−SnO2 Nanocomposite Loaded on Pd Support for Determination of Nitrite at Trace Levels

Here, an electrochemical sensor based on CeO₂‐SnO₂/Pd was prepared and used for highly selective and sensitive determination of nitrite in some real samples. This nanocomposite was characterized by various methods like X‐ray photoelectron spectroscopy, X‐ray diffraction, energy dispersive spectroscopy, Fourier‐transform infrared spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical behavior of the sensor was evaluated by cyclic voltammetry. The results showed excellent catalytic property of the nanocomposite as a an electrocatalyst for nitrite oxidation. In the following, the experimental parameters affecting the analytical signal for nitrite were optimized. Under the optimal conditions, the limit of detection and sensitivity of the sensor were calculated as 0.10 μM and 652.95 μA.mM^?1.cm^?2, respectively. Also, the response of the sensor was linear in the range of 0.36 to 2200 μM of nitrite. Finally, some of the inherent features of the sensor such as repeatability, reproducibility and stability were examined after evaluation of the sensor selectivity in the presence of several interfering species.     

A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3‐Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide

In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3‐aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO‐APTES) and hydrogen peroxide sensor based on rGO‐APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X‐ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO‐APTES/GOx/GC and Nf/rGO‐APTES/GC composites showed good electrocatalytical activity toward glucose and H₂O₂, respectively. The Nf/rGO‐APTES/GC electrode exhibited a linear range of H₂O₂ concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 μA mM⁻¹ cm⁻². The Nf/rGO‐APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 μM and sensitivity of 75.26 μA mM⁻¹ cm⁻². Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.     

Electrocatalytical Oxidation of Nitrite and Its Determination Based on Au@Fe3O4 Nanoparticles

A promising electrochemical nitrite sensor was fabricated by immobilizing Au@Fe₃O₄ nanoparticles on the surface of L ‐cysteine modified glassy carbon electrode, which was characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The proposed sensor exhibited excellent electrocatalytic activity toward nitrite oxidation. The kinetic parameters of the electrode reaction process were calculated, (1–α)n_α was 0.38 and the heterogeneous electron transfer coefficient (k) was 0.13 cm s^?1. The detection conditions such as supporting electrolyte and pH value were optimized. Under the optimized conditions, the linear range for the determination of nitrite was 3.6×10^?6 to 1.0×10^?2 M with a detection limit of 8.2×10^?7 M (S/N=3). Moreover, the as‐prepared electrode displayed good stability, repeatability and selectivity for promising practical applications.     

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.     

A Non‐Enzymatic Hydrogen Peroxide Sensor Based on Ag/MnOOH Nanocomposites

A novel non‐enzymatic sensor based on Ag/MnOOH nanocomposites was developed for the detection of hydrogen peroxide (H₂O₂). The H₂O₂ sensor was fabricated by immobilizing Ag/MnOOH nanocomposites on a glassy carbon electrode (GCE). The morphology and composition of the sensor surface were characterized using scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy and X‐ray diffraction spectroscopy. The electrochemical investigation of the sensor indicates that it possesses an excellent electrocatalytic property for H₂O₂, and could detect H₂O₂ in a linear range from 5.0 µM to 12.8 mM with a detection limit of 1.5 µM at a signal‐to‐noise ratio of 3, a response time of 2 s and a sensitivity of 32.57 µA mM^?1 cm^?2. Additionally, the sensor exhibits good anti‐interference. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective non‐enzymatic H₂O₂ sensor.     

Preparation and Characterization of Bhant Leaves‐derived Nitrogen‐doped Carbon and its Use as an Electrocatalyst for Detecting Ketoconazole

In this study, the electrocatalytic characteristics of nitrogen‐doped carbon (NDC) prepared from Clerodendrum Infortunatum L leaves on a glassy carbon electrode (GCE) surface was evaluated with regards to its ability to detect the electroactive drug ketoconazole (KCZ). The NDC was prepared by carrying out a simple pyrolysis of dry powder of the leaves at 850 °C. The prepared NDC was characterized using field‐emission scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and Brunauer‐Emmett‐Teller analysis, and was then used as an electrode material. The performance of the electrochemical KCZ sensor with the NDC‐modified glassy carbon electrode (NDC/GCE) was found to be optimal when using PBS buffer at pH 3 and a concentration of 0.1 mg/ml of NDC in the conjugate with Nafion polymer. Under these conditions, the NDC/GCE displayed a KCZ detection limit of 3 μM and a linear dependence of its response on KCZ concentration over a wide range of KCZ concentrations from 47 μM to 752 μM (R²=0.9742). These results confirmed the potential of NDC as an electrocatalyst.     

Nickel Hydroxide and Intercalated Graphene with Ionic Liquid Nanocomposite‐modified Electrode for Sensing of Glucose

A novel non‐enzymatic glucose sensor based on nickel hydroxide and intercalated graphene with ionic liquid (G‐IL) nanocomposite modified glass carbon electrode was fabricated. Scanning electron microscope, Fourier transform infrared spectra and energy dispersive X‐ray spectroscopy of the nanocomposite confirmed the morphology and ingredient of Ni(OH)₂ as well as G‐IL. Moreover, experimental results of cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry indicated the sensing properties of Ni(OH)₂ at Ni(OH)₂/G‐IL modified electrode towards the typical electrocatalytic oxidation process of glucose at 0.43 V in 0.10 M NaOH. The current response was linearly related to glucose concentration in a range from 0.5 to 500 μM with a detection limit of 0.2 μM (S/N = 3) and sensitivity of 647.8 μA mM^?1 cm^?2. The response time of the sensor to glucose was less than 2 s. This work may be expected to develop an excellent electrochemical sensing platform of G‐IL as a catalysis carrier.     

Flower‐like Ni(II)‐based Metal‐organic Framework‐decorated Ag Nanoparticles: Fabrication,Characterization and Electrochemical Detection of Glucose

Glucose concentration monitoring is important for the prevention, diagnosis and treatment of diabetes. In this work, a composite material of AgNPs/MOF‐74(Ni) was prepared for electrochemical determination of glucose. AgNPs/MOF‐74(Ni) was characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS). The electrochemical properties of the glassy carbon electrodes modified with the AgNPs/MOF‐74(Ni) composites were characterized by cyclic voltammetry (CV) and current‐time curve (I‐t curve) with three electrode system. The determination of glucose with the electrode modified by AgNPs/MOF‐74(Ni) has a linear range of 0.01～4 mM with the correlation coefficient (R²) of 0.994. The detection limit is 4.7 μM (S/N=3) and the sensitivity is 1.29 mA ? mM^?1 ? cm^?2. In addition, this sensing system possesses reasonable reproducibility and stability. The good performance of electrochemical determination for glucose is attributed to the concerted effect of silver nanoparticles and MOF‐74(Ni) on the promotion of glucose oxidation     

Electrocatalytic Activity of Nanocomposites of Sulphur Doped Graphene Oxide and Nanosized Cobalt Phthalocyanines

In this work we explore the electrocatalytic activity of nanocomposites of reduced sulphur doped graphene oxide nanosheets (rSDGONS) and cobalt phthalocyanine (CoPc) or cobalt tetra amino phthalocyanine (CoTAPc) towards hydrogen peroxide. Transmission electron microscopy, scanning electron microscopy, X‐ray photon spectroscopy, X‐ray diffraction, chronoamperometry, linear scan voltammetry and cyclic voltammetry were used to characterize the nanocomposites. Nanosized CoPc showed superior (in terms of currents) electrocatalytic oxidation and reduction of hydrogen peroxide compared to CoTAPc nanoparticles (CoTAPc NP ). The lowest detection limit was obtained for hydrogen peroxide oxidation on electrodes modified with CoPc NP ‐rSDGONS at 1.49 µM. The same electrode gave a high adsorption equilibrium constant of 1.27×10³ mol^?1 and a Gibbs free energy of ?17.71 kJ/mol, indicative of a spontaneous reaction on the electrode surface.     

Electrochemical Investigation of Glucose on a Highly Sensitive Nickel‐Copper Modified Pencil Graphite Electrode

Novel nickel‐copper modified pencil graphite electrode (Ni?Cu/PGE) was fabricated and used as non‐enzymatic sensor for glucose determination. Ni and copper were electrodeposited on PGE using cyclic voltammetry. Morphology and composition of the modified PGE electrode were characterized by field‐emission gun scanning electron microscopy (FEG‐SEM), energy‐dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT‐IR). Electrochemical oxidation of glucose was evaluated by cyclic voltammetry as well as by amperometry. Electrochemical measurements indicate that the Ni?Cu/PGE exhibits a high sensitivity of 2951 μA mM^?1 cm^?2, and a low detection limit of 0.99 μM which are, respectively, three times higher and twice lower than that on Ni/PGE prepared in the same conditions. Moreover, Ni?Cu/PGE exhibits a wider linear range from 1 to 10000 μM with a rapid response time within 2 s. Moreover, Ni?Cu/PGE showed a remarkable stability. The electrode was successfully applied for determination of glucose concentration in human blood without significant interference from potential endogenic interferents. The good applicability of the elaborated sensor made Ni?Cu/PGE promising for the development of effective and inexpensive non‐enzymatic glucose sensor.     

Molecularly Imprinted Polyresorcinol Based Capacitive Sensor for Sulphanilamide Detection

A molecularly imprinted polymer (MIP) based capacitive sensor for antibiotic detection in drinking water and milk has been developed on a gold coated silicon electrode (Au Electrode). The electrode was fabricated by electropolymerizing monomer resorcinol (RN) on Au surface in presence of sulphanilamide (SN) as a template molecule, to get insulated RN polymer antibiotic composite. The insulation of the polymer film was improved by incubation of electrode in 1‐Dodecanethiol solution. Subsequently MIP sensor was obtained by extraction of SN in ethanol and acetic acid solution. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements were performed for characterization of the developed MIP electrode at different steps of fabrication. The surface morphology of MIP electrode was characterized using atomic force microscopy (AFM), X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x‐ray spectroscopy (EDS). Performance of MIP sensor was evaluated by measuring change in capacitance against varying concentration of SN using EIS. A linear response in the range 1 to 200 μg L^?1 SN was recorded for MIP sensor with a detection limit of 0.1 μg L^?1. The developed MIP sensor exhibited good selectivity towards SN in water and milk with recoveries in the range 92 % to 105 %. The obtained results suggest the usability of MIP based sensor for SN estimation in water and milk samples.     

Synthesis of Ferrosoferric Oxide‐graphene Oxide Nanocomposite by Isoelectric Point Method for the Detection of Catechol

Ferrosoferric oxide functionalized graphene oxide nanocomposite with layer by layer structure was synthesized by isoelectric point method in this work. The prepared material was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Then the material was used to modify a glassy carbon electrode to fabricate an electrochemical sensor for the detection of catechol. The electrochemical sensor exhibited excellent electrochemical performance towards the detection of catechol with a linear response in the range of 5–205 μM and a detection limit of 2.32 μM. Furthermore, the electrochemical sensor showed excellent selectivity, stability and repeatability. These results revealed ferrosoferric oxide functionalized graphene oxide nanocomposite has potential applications in the fabrication of electrochemical sensors.     

Differential Pulse Voltammetry Determination of Ofloxacin in Human Serum and Urine Based on a Novel Tryptophan‐graphene Oxide‐carbon Nanotube Electrochemical Sensor

The highly sensitive determination of ofloxacin (OFL) in human serum and urine was achieved on a novel tryptophan‐graphene oxide‐carbon nanotube (Trp‐GO‐CNT) composite modified glassy carbon electrode (Trp‐GO‐CNT/GCE). The Trp‐GO‐CNT composite was fabricated, and its morphologies and surface functional groups were characterized by field emission scanning electron microscopy (FE‐SEM) and Fourier transform infrared (FT‐IR) spectroscopy. The electrochemical properties of Trp‐GO‐CNT/GCE were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The superior electrochemical behaviors of Trp‐GO‐CNT/GCE toward OFL can be mainly assigned to the excellent electrocatalytic activity of Trp, the great conductivity and high surface area of GO and CNT, and the synergistic effect between Trp, GO and CNT. Under optimum conditions, a wide and valuable linear range (0.01–100 μM), a low detection limit (0.001 μM, S/N=3), a good linear relationship (R2>0.999), good stability and repeatability were obtained for the quantitative determination of OFL. Furthermore, the Trp‐GO‐CNT electrochemical sensor was successfully applied to the determination of OFL in human serum and urine samples, and satisfactory accuracy and recovery could be obtained.     

A New Amperometric Hydrazine Sensor Based on Prussian Blue/Single‐walled Carbon Nanotube Nanocomposites

A slow reaction process has been successfully used to synthesize Prussian blue/single‐walled carbon nanotubes (PB/SWNTs) nanocomposites. Electrochemical and surface characterization by cyclic voltammetry (CV), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV‐vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) confirmed the presence of PB nanocrystallites on SWNTs. PB/SWNTs modified glassy carbon electrode (GCE) exhibits efficient electron transfer ability and high electrochemical response towards hydrazine. The fabricated hydrazine sensor showed a wide linear range of 2.0×10^?6–6.0×10^?3 M with a response time less than 4 s and a detection limit of 0.5 μM. PB/SWNTs modified electrochemical sensors are promising candidates for cost‐effective in the hydrazine assays.