Electrochemical Sensor for Sensitive Determination of Capsaicin Using Pd Decorated Reduced Graphene Oxide

In this work, the reduced graphene oxide functionalized with poly dimethyl diallyl ammonium chloride (PDDA) modified palladium nanoparticles (PDDA‐rGO/Pd) had been facile synthesized and used as the sensing layer for sensitive determination of capsaicin. The prepared composite was characterized by transmission electron microscopy, UV‐visible absorption spectroscopy. The image demonstrated that Pd nanoparticles were uniformly distributed on the graphene surface. The electrochemical properties of the prepared sensor were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the nanocomposite exhibits attractive electrocatalytic activity towards the oxidation of capsaicin. This attributed to the synergistic action of the excellent properties of Pd nanoparticles and graphene nanosheets. Under optimized conditions, the electrochemical sensor possessed a dynamic linear range from 0.32 μM to 64 μM with a detection limit of 0.10 μM (S/N=3) for capsaicin detection. Moreover, the cost‐effective and simple fabrication procedure, good reproducibility and stability as well as acceptable accuracy for capsaicin determination in actual samples are also the main advantages of this method, which might have broad application in other amide alkaloid detection.     

N-Doped Carbon Coated TiC Nanofiber Arrays on Ti-6Al-4V for Sensitive Electrochemical Determination of Cr(VI)

A sensitive electrochemical sensor for Cr(VI) detection based on N-doped carbon coated TiC nanofiber arrays (TiC@CNx NFAs) is reported. The abundant electrocatalytic active sites contained CNx shell, highly conducting TiC core, and good electrical contact between the TiC@CNx and underlying Ti alloy endow this electrode with the excellent electrochemical sensing properties. The developed electrochemical sensor shows remarkable determination activity towards Cr(VI) with a high sensitivity of 0.88 μA μM⁻¹ cm⁻², a low detection limit of 4.0 nM (S/N=3), a wide linear range from 0.2 to 24.1 μM, good selectivity and anti-interference property.     

An Enzyme-free Electrochemical H2O2 Sensor Based on a Nickel Metal-organic Framework Nanosheet Array

In this work, we reported the development of a nickel metal-organic framework nanosheet array on Ti-mesh (Ni-MOF/TM) as an enzyme-free electrochemical sensing platform for H₂O₂ determination. The as-obtained sensor exhibited outstanding detection properties of H₂O₂, which might be gifted from the large specific surface area, abundant active sites of Ni-MOF nanoarrays. The sensor displayed a good linear range (0.8 μM–4.6×10³ μM), a detection limit as low as 0.26 μM, a high sensitivity (307.5 μA mM⁻¹ cm⁻²), and a rapid response. Moreover, this enzyme-free sensor is promising for point-of-care (POC) testing of H₂O₂ in human serum attribute to the excellent performance of Ni-MOF and the simple preparation process of the sensor.     

Electrochemical Probe of the Reduced Graphene Oxide Modified by Bare Gold Nanoparticles Functionalized Zr(IV)-based Metal-organic Framework for Detecting Nitrite

Widely presented nitrite in drinking water, food and even physiological system endangers human health. Here,bare gold nanoparticles functionalized Zr-based metal-organic framework modified reduced graphene oxide (GNPs/UiO-66-NH₂/rGO) nanocomposites were prepared by hydrothermal method. This experiment studies the morphology, composition, structure and electrochemical behavior of the sensor. The experimental results show that the sensor has a peak potential of 0.9 V, the concentration range of NO₂⁻ is 5.0 μM to 768 μM, the linear regression equation of the calibration curve is I_pa=0.3646+0.00642 C (R²=0.9998), and the LOD is as low as 3.7 μM (S/N=3). Therefore, an electrochemical sensor platform for trace detection of NO₂⁻ was successfully constructed.     

Single step modification of copper electrode for the highly sensitive and selective non-enzymatic determination of glucose

A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy, and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct electrocatalytic oxidation of glucose on a CuO/Cu electrode at 0.7 V in 0.1 M sodium hydroxide. At this potential, the sensor is highly selective to glucose even in the presence of ascorbic acid, uric acid, or dopamine which are common interfering species. The sensor displays a sensitivity of 761.9 μA mM^?1 cm^?2, a linear detection range from 2 μM to 20 mM, a response time of <1 s, and a detection limit of 1 μM (S/N = 3). It was tested for determination of glucose level in blood serum.     

First Electroanalytical Methodology for the Determination of Hordenine in Dietary Supplements using a Boron‐doped Diamond Electrode

The present work describes the first electrochemical investigation and a simple, rapid and modification‐free electroanalytical methodology for quantification of hordenine (a potent phenylethylamine alkaloid) using a boron‐doped diamond electrode. At optimized square‐wave voltammetric parameters, the observed oxidation peak current in 0.1 M HClO₄ at +1.33 V (vs. Ag/AgCl) increased linearly from 5.0 to 100 μg mL^?1 (3.0×10^?5–6.1×10^?4 M), with detection limit of 1.3 μg mL^?1 (7.8×10^?6 M). The applicability of the developed method was tested with the determination of hordenine in the commercial dietary supplement formulations.     

Functionalized Carbon Black Nanospheres Hybrid with MoS2 Nanoclusters for the Effective Electrocatalytic Reduction of Chloramphenicol

Synthesis of nanomaterials using cheap and highly efficient material is an important aspect of nanotechnology. In this present work, we have used the carbon black (CB) as a highly conductive and inexpensive carbonaceous material for the fabrication of the electrochemical sensor. However, the poor dispersion in water obstructs the usage of CB in electrochemical sensor and biosensor applications. Hence, the CB was functionalized by simple reflux method and the functionalized CB (f‐CB) nanospheres hybrids with hydrothermally synthesized MoS₂ nanoclusters by simple ultrasonication process. In addition, the various suitable spectrometric techniques used to probe the surface morphology and chemical modification of the prepared materials. The prepared MoS₂ and f‐CB nanohybrids (f‐CB/MoS₂) applied for the electrocatalytic reduction of toxic chloramphenicol (CAP). Fascinatingly, the f‐CB/MoS₂ modified electrode showed a competitive electrocatalytic performance comparing with other modified electrodes. At the optimized condition, the sensor exhibited the LOD about 0.002 μM, wider linear range 0.015 to 1370 μM with the sensitivity of 3400 μA μM⁻¹ cm⁻² for the determination of CAP. Moreover, the practical viability of the sensor was exploited in milk powder and honey samples.     

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.     

Self‐Assembled Prussian Blue Nanoparticles Based Electrochemical Sensor for High Sensitive Determination of H2O2 in Acidic Media

In this paper, self‐assembled Prussian blue nanoparticles (PBNPs) on carbon ceramic electrode (CCE) were developed as a high sensitive hydrogen peroxide (H₂O₂) electrochemical sensor. The PBNPs film was prepared by a simple dipping method. The morphology of the PBNPs‐modified CCE was characterized by scanning electron microscopy (SEM). The self‐assembled PB film exhibited sufficient mechanical, electrochemical stability and high sensitivity in compare with other PB based H₂O₂ sensors. The sensor showed a good linear response for H₂O₂ over the concentration range 1 μM–0.26 mM with a detection limit of ca. 0.7 μM (S/N=3), and sensitivity of 754.6 mA M^?1 cm^?2. This work demonstrates the feasibility of self‐assembled PBNPs‐modified CCE for practical sensing applications.     

Electrochemical Glyphosate Sensor Based on Hybrid Material SiO2/Sm2O3/Carbon Modified with Meldola Blue

In this work, we have proposed an electrochemical sensor for the detection of pesticides by using a ceramic composite with a SiO₂ surface modified with Sm₂O₃ nanoparticles and C-graphite (SSMG), obtained by the sol-gel process and immobilized by adsorption in Meldola Blue cationic dye (MB). The composite was called (SSMG/MB), which was characterized by spectroscopic, electrochemical techniques, Fourier-transform infrared spectroscopy, and Cyclic Voltammetry. The proposed sensor was applied for the glyphosate electrochemical detection, using Differential Pulse Voltammetry, and, under optimized parameters has presented the linear response for the pesticide in the concentration range from 0.99 to 7.94 (μmol L⁻¹; R²=0.9963; n=8). The calculated values for the detection limit and the quantification limit were 0.15 and 0.49 μmol L⁻¹, respectively. Therefore, the new electrochemical sensor based on SiO₂, NPsSm₂O_3, C-graphite, and MB hybrid material was developed for the first time for glyphosate determination, which has demonstrated high potential for the development of new hybrid devices for environmental control.     

Synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>—Ag nanocomposites and their application to enzymeless hydrogen peroxide detection

To achieve highly sensitive nonenzymatic detection of H₂O₂, a novel electrochemical sensor based on Fe₃O₄-Ag nanocomposites was developed. Nanocomposites were synthesized by reducing [Ag(NH₃)₂]⁺ at the gas/liquid interface in the presence of silver seeds and confirmed by transmission electron microscopy and X-ray diffractometry. Electrochemical investigations indicate that the sensor is able to detect H₂O₂ within a wide linear range of 0.5 μM to 4.0 mM, sensitivity of 135.4 μA mM^?1 cm^?2 and low detection limit of 0.2 μM (S/N = 3). Additionally, the sensor exhibits good anti-interference ability, stability and repeatability. These results show that the Fe₃O₄-Ag nanocomposite is a promising electrocatalytic material for sensors construction.     

Photoelectrochemical Sensor for Isoniazid: Application in Drugs Used in the Treatment of Tuberculosis

The present work describes the development of a photoelectrochemical sensor based on titanium dioxide, cadmium telluride quantum dots and the tris (2,2′-bipyridyl) ruthenium(II) chloride complex for detection of Isoniazid (INH). The Ru(bpy)₃²⁺/CdTe-QDs/TiO₂/FTO photoelectrochemical platform was characterized by scanning electrochemical microscopy, electrochemical impedance spectroscopy and amperometry. The photoelectrochemical sensor presented two linear ranges for INH concentrations ranging from 0.5 to 150 μmol L⁻¹ and 150 to 1270 μmol L⁻¹, with a theoretical detection limit of 0.02 μmol L⁻¹. The sensor was successfully applied for the determination of INH in drugs samples used in the treatment of tuberculosis.     

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.     

A Novel Electrochemical Sensor Based on Copper‐based Metal‐Organic Framework for the Determination of Dopamine

A glassy carbon electrode (GCE) modified with a copper‐based metal‐organic framework (MOF) [HKUST‐1, HKUST‐1 = Cu₃(BTC)₂ (BTC = 1,3,5‐benzenetricarboxylicacid)] was developed as a highly sensitive and simple electrochemical sensor for the determination of dopamine (DA). The MOF was prepared by a hydrothermal process, and the morphology and crystal phase of the MOF were characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD), respectively. Meanwhile, the electrochemical performance was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the modified electrode showed excellent electrocatalytic activity and high selectivity toward DA. The linear response range was from 5.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M and the detection limit was as low as 1.5 × 10⁻⁷ M. Moreover, the electrochemical sensor was used to detect DA in real samples with excellent results. MOF‐based sensors hold great promise for routine sensing applications in the field of electrochemical sensing.     

Nitrogen‐doped Hollow Co3O4 Nanofibers for both Solid‐state pH Sensing and Improved Non‐enzymatic Glucose Sensing

Nitrogen‐doped hollow cobalt oxide nanofibers (Co₃O₄ NFs) with both glucose catalytic activity and pH sensitivity were fabricated through core‐sheath electrospinning technique, followed by calcination. The as‐developed nitrogen‐doped hollow Co₃O₄ NFs were thoroughly characterized using various techniques, and then employed to fabricate a dual electrochemical sensor for both pH sensing and glucose sensing. The pH sensitivity of the developed nitrogen‐doped hollow Co₃O₄ NFs demonstrated a Nernst constant of 12.9–15.9 mV/pH in the pH range of 3.0～9.0 and 6.8–10.7 mV/pH in the pH range of 9.0～13.0, respectively. The developed hollow cobalt oxides nanofibers sensor also possesses glucose sensitivity of 87.67 μA mM^?1 cm^?2, the limit of detection of 0.38 μM (S/N=3), and an acceptable selectivity against several common interferents in non‐enzymatic glucose determination. High accuracy for monitoring glucose in human serum sample was also demonstrated. These features indicate that the as‐synthesized nitrogen‐doped hollow cobalt oxides nanofibers hold great potential in the development of a unique dual sensor for both solid‐state pH sensing and superior non‐enzymatic glucose sensing.     

An enhanced oxime-based biomimetic electrochemical sensor modified with multifunctional AuNPs–Co<Subscript>3</Subscript>O<Subscript>4</Subscript>–NG composites for dimethoate determination

An enhanced oxime-based electrochemical sensor decorated with gold nanoparticles (AuNPs) and Co₃O₄ hexagonal nanosheets coupled with nitrogen-doped graphene has been developed for dimethoate determination dramatically. The introduction of Co₃O₄ hexagonal nanosheets tackles agglomeration of AuNPs and also enhances the sensitivity of electrochemical sensors greatly. The structure and properties of the synthesized composites were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy, confirming the successful modification of 2-(4-mercaptobutoxy)-1-naphthaldehyde oxime and Co₃O₄ supported AuNPs in a great experiment. In addition, differential pulse voltammetry further revealed that the developed electrochemical sensor exhibited excellent selectivity, sensitivity and stability in real samples analysis. Under optimal conditions, the modified sensor displayed a broad linear range from 1?×?10^?14 M to 1?×?10^?6 M with a fairly low detection limit of 8.4?×?10^?14 M (S/N?=?3) and was expected to act as a superior method for dimethoate determination.     

Synthesis of Ferrocene Based Naphthoquinones and its Application as Novel Non‐enzymatic Hydrogen Peroxide

At present, a highly sensitive hydrogen peroxide (H₂O₂) sensor is fabricated by ferrocene based naphthaquinone derivatives as 2,3‐Diferrocenyl‐1,4‐naphthoquinone and 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone. These ferrocene based naphthaquinone derivatives are characterized by H‐NMR and C‐NMR. The electrochemical properties of these ferrocene based naphthaquinone are investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) on modified glassy carbon electrode (GCE). The modified electrode with ferrocene based naphthaquinone derivatives exhibits an improved voltammetric response to the H₂O₂ redox reaction. 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone show excellent non‐enzymatic sensing ability towards H₂O₂ response with a detection limitation of 2.7 μmol/L a wide detection range from 10 μM to 400 μM in H₂O₂ detection. The sensor also exhibits short response time (1 s) and good sensitivity of 71.4 μA mM^?1 cm^?2 and stability. Furthermore, the DPV method exhibited very high sensitivity (18999 μA mM^?1 cm^?2) and low detection limit (0.66 μM) compared to the CA method. Ferrocene based naphthaquinone derivative based sensors have a lower cost and high stability. Thus, this novel non‐enzyme sensor has potential application in H₂O₂ detection.     

Simultaneous Determination of Catechol and Hydroquinone on Nano-Co/L-Cysteine Modified Glassy Carbon Electrode

In this study, a novel and highly sensitive electrochemical method for simultaneous determination of catechol (CC) and hydroquinone (HQ) was developed, which worked at GCE modified with Nano cobalt (Nano-Co) by electrodeposition and L-Cysteine by electrochemical polymerization. The Nano-Co/L-Cysteine GCE was investigated by cyclic voltammetry (CV), SEM and EIS. The excellent conditions have been selected including supporting electrolyte, pH, accumulation time and scan rate. The calibration curves of were obtained that the linear regression equation was I=0.0734c+6×10⁻⁶ in the range of 5.8 μM to 103 μM (R²=0.9942) for CC and the linear regression equation was I=0.0566c+5×10⁻⁶ in the range of 5.8 μM to 100 μM (R²=0.9967) for HQ. The obtained detection limits of CC and HQ both were 6×10⁻⁷ M. The modified electrode was successfully applied to the simultaneous determination of CC and HQ in water samples.     

Single Step Synthesis of MoSe2−MoO3 Heterostructure for Highly Sensitive Amperometric Detection of Nitrite in Water Samples of Industrial Areas

The present work reports a simple and single‐step hydrothermal synthesis of MoSe₂?MoO₃ composite for highly sensitive and selective electrochemical oxidation of nitrite. FESEM of the MoSe₂?MoO₃ hybrid revealed the formation of composite as laminated structure of different sizes piled up together as finger‐like MoSe₂ bars whilst other physico‐chemical characterizations (XRD, FTIR, UV‐Vis, XPS) confirmed that co‐existence of MoO₃ as a major by‐product of hydrothermal synthesis. The as‐fabricated MoSe₂?MoO₃ composite based nitrite sensor showed remarkable selectivity and reproducibility with <3s of response time, excellent sensitivity and detection limit of 10.84 A M^?1 cm^?2 (R²=0.996) and 0.1 μM, respectively, in the range of 2.5–80 μM. The obtained sensitivity can be credited to the high surface area obtained from 1T phase MoSe₂ and α phase MoO₃ as the sensing material. The developed sensor was effectively evaluated for electrochemical recognition of nitrite in the water samples (potable and tap water) gathered from an industrial area. This new and efficient MoSe₂?MoO₃ based electrode material offers a new frontier for the progress of a novel composites by simple and single‐step approach which can be used for progress of non‐enzymatic and inexpensive electrochemical sensors for a wide range of analytical applications.     

Synthesis of Cysteine Modified MoS2 Nanocomposite: A Biocompatible Electrochemical Sensor Material and its Application to the Determination of Antidiabetic Dapagliflozin

Herein, for the first time, a new generation cysteine modified MoS₂ (Cys@MoS₂) based electrochemical sensor was reported. The electrochemical behaviour of dapagliflozin (DAP) was investigated through differential pulse voltammetry (DPV) on the developed sensor (Cys@MoS₂/GCE). The transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), x‐ray diffraction spectroscopy (XRD) and x‐ray photoelectron spectroscopy (XPS) methods were performed for structural and morphological characterizations of Cys@MoS₂ nanocomposite. On the surface of Cys@MoS₂/GCE, an irreversible anodic peak was observed at 1324 mV. Under the optimal conditions, linear calibration curve with two working ranges between 2.0–60.0 μM and 60.0–110.0 μM were obtained and limit of detection was found to be 1.6 μM. The developed sensor was successfully applied to determine the content of DAP in pharmaceutical sample with satisfying recovery results. It is concluded that Cys@MoS₂/GCE is a reliable, easy to apply and cost‐effective sensor for the routine DAP analysis in pharmaceutical samples.