Assessment of Melamine in Different Water Samples with ZnO-doped Co3O4 Nanoparticles on a Glassy Carbon Electrode by Differential Pulse Voltammetry

In this investigation, a melamine electrochemical sensor has been developed by using wet-chemically synthesized low-dimensional aggregated nanoparticles (NPs) of ZnO-doped Co₃O₄ as sensing substrate that were decorated onto flat glassy carbon electrode (GCE). The characterization of NPs such as UV-Vis, FTIR, XRD, XPS, EDS, and FESEM was done for detailed investigations in optical, functional, structural, elemental, and morphological analyses. The ZnO-doped Co₃O₄ NPs decorated GCE was used as a sensing probe to analyze the target chemical melamine in a phosphate buffer at pH 5.7 by applying differential pulse voltammetry (DPV). It exhibited good performances in terms of sensor analytical parameters such as large linear dynamic range (LDR; 0.15–1.35 mM) of melamine detection, high sensitivity (80.6 μA mM⁻¹ cm⁻²), low limit of detection (LOD; 0.118±0.005 mM), low limit of quantification (LOQ; 0.393 mM), and fast response time (30 s). Besides this, the good reproducibility (in several hours) and repeatability were investigated under identical conditions. Moreover, it was implemented to measure the long-time stability, electron mobility, less charge-transfer resistance, and analyzed diffusion-controlled process for the oxidation reaction of the NPs assembled working GCE electrode, which showed outstanding chemical sensor performances. For validation, real environmental samples were collected from various water sources and investigated successfully with regard to the reliability of the selective melamine detection with prepared NPs coated sensor probe. Therefore, this approach might be introduced as an alternative route in the sensor technology to detect selectively unsafe chemicals by an electrochemical method with nanostructure-doped materials for the safety of environmental, ecological, healthcare fields in a broad scale.     

A novel electrochemical sensor based on gold nanorods and Nafion-modified GCE for the electrocatalytic oxidation of nitrite

The high-quality CTAB-stabilized gold nanorods (Au NRs) were prepared by the way of seed-mediated protocol. The microstructure and composition of the Au NRs were identified by transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and UV–visible spectroscopy. Further, a novel non-enzymatic electrochemical sensor of nitrite based on Au NRs–Nafion-modified glassy carbon electrode (GCE) was successfully developed. Under the optimum experimental conditions, the electrochemical behaviors of nitrite on the Au NRs–Nafion-modified GCE were systematically studied by electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry. The electrochemical investigations indicated that the Au NRs–Nafion-modified GCE had a wide linear range of 3.0 × 10^?6–6.0 × 10^?3 mol L^?1, an acceptable sensitivity of 130.9 ± 0.05 μA mM^?1 cm^?2, a fast response time of 3 s and a low detection limit of 0.64 ± 0.02 μmol L^?1 at the signal-to-noise ratio of 3 (S/N = 3). Additionally, the electrochemical sensor also showed good stability and favorable anti-interference capability for the detection of nitrite.     

A Novel Cerium Tungstate Nanosheets Modified Electrode for the Effective Electrochemical Detection of Carcinogenic Nitrite Ions

In this present scenario, for the first time, we propose a facile and simple wet chemical approach for the fabrication of two‐dimensional (2D) cerium tungstate (CeW₂O₉;CeW) nanosheets and evaluated as an electrochemical sensor for the detection of nitrite ions. The successful formation of CeW₂O₉ nanosheets was confirmed by various physicochemical techniques such as X‐ray diffraction, Fourier transform infrared spectroscopy, Raman, Scanning electron microscope, Transmission electron microscope and Energy dispersive X‐ray studies. The electrochemical properties of the CeW nanosheets were studied by using cyclic voltammograms (CV) and chronoamperometric techniques. As an electrochemical sensor, the CeW nanosheets modified glassy carbon electrode (GCE) showed superior electrocatalytic activity in the oxidation of nitrite in terms of higher anodic peak current and lower oxidation potential when compared with unmodified GCE. CeW nanosheets based electrochemical sensor has been fabricated which detect nitrite in wide linear response range, good sensitivity and very low detection limit of 0.02–986 μM, 2.85 μA μM⁻¹ cm⁻² and 8 nM, respectively. Moreover, the CeW nanosheets modified GCE exhibited excellent selectivity even in the presence of common metal ions and biologically co‐interfering compounds. For the practical viability of the prepared amperometric sensor has been utilized in various water samples such as tap, lake and drinking water and the obtained recoveries are appreciable.     

Development of reproducible thiourea sensor with binary SnO2/V2O5 nanomaterials by electrochemical method

In this methodology, the thiourea (TU) sensor was made-up by means of glassy carbon electrode (GCE) layered by the wet-chemically prepared binary SnO₂/V₂O₅ nanomaterials (NMs). The existence of SnO₂ and V₂O₅ in prepared spherical NPs were categorized by X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray spectroscopy and X-ray Powder Diffraction (XRD). The TU sensor was displayed the linear responses in concentration range (LDR) of 0.1 nM ~ 0.01 mM. The calibration curve of TU sensor was made by plotting current verses concentration of TU, which was measured by electrochemical technique. The sensitivity and lower limit of detection (DL) for TU sensor were calculated from calibration curve, which are found as 17.0918 µAµM^-1cm⁻² and 95.40 ± 4.77 pM respectively. The analytical parameters of TU sensor such as reproducibility, response time and stability were measured and found efficient results. It also was validated in the detection of TU in presence of real bio-samples. Thus, this unique and prospective method is introduced to develop the selective biosensor by electrochemical approach, which might be a pioneer sensor probe for its simple and reliable approach for the safety of healthcare and biomedical fields in a large scales.     

Sensitive detection of Penicillin-G chemical using SnO2.YbO nanomaterials by electrochemical approach

In this approach, binary tin oxide doped ytterbium oxide nanosheets (SnO₂.YbO NSs) were synthesized in an alkaline phase using under low-temperature facile hydrothermal technique. Traditional methods such as UV–Visible spectroscopy, Fourier Transform Infra-Red Spectroscopy (FTIR), Powder X-ray diffraction (XRD), Field Emission Scanning Microscopy (FESEM) equipped with X-ray electron dispersive spectroscopy (XEDS), and X-ray photoelectron spectroscopy (XPS) were used to fully characterize the prepared SnO₂.YbO NSs. Fabrication of a thin-coating with doped NSs onto GCE by using 5% nafion conducting binder resulted in development of a selective and enzyme-free penicillin-G sensor probe. A reliable I-V technique was used to perform electrochemical performances of good sensitivity, large LDR, and long-term stability of the desired Penicillin-G sensor (SnO₂.YbO NSs/GCE/Nf). With a wide range of Penicillin-G concentration, the proposed calibration plot is noticed good linearity (R² = 0.9830). Sensitivity and LOD of the sensor were calculated as 24.75 μAμM^-1cm^?2 and 30.0 pM, respectively based on S/N = 3 formula. Real samples (Human and rabbit serum, milk, and red-sea water) were analyzed with the fabricated SnO₂.YbO NSs/GCE/Nf sensor probe and the findings results were acceptable and satisfactory. This approach could be a noble development of in-situ Penicillin-G sensor based on binary SnO₂.YbO NSs/GCE/Nf by reliable I-V technique for important sensing applications including beneficial doped nanomaterials and nano-technological system.     

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.     

Development of Electrochemical Platform Based on Molecularly Imprinted Poly(methacrylic acid) Grafted on Iniferter-modified Carbon Nanotubes for 17β-Estradiol Determination in Water Samples

This paper describes the development of a new electrochemical sensor for 17β-estradiol (E2) determination based on glassy carbon electrode (GCE) modified with molecularly imprinted polymer grafted onto iniferter-multiwall carbon nanotubes surface (MIP-MWCNT) and dihexadecyl-hydrogen-phosphate (DHP). The electrochemical method was based on closed-circuit preconcentration of E2 in 0.1 mol L⁻¹ phosphate buffer (pH 7.0) during 500 s. Upon preconcentration, E2 was determined by differential pulse voltammetry (DPV) exhibiting a limit of detection of 0.01 μmol L⁻¹. The sensor exhibited higher selectivity toward E2 and it was applied for E2 determination in natural water samples, with accuracy attested by HPLC-DAD.     

Gold Nanoparticles-electrochemically Reduced Graphene Oxide/Poly(indole-5-carboxylic acid) Nanocomposite for Electrochemical Non-enzymatic Sensing of Hydrogen Peroxide

Herein, co-electrodeposition of AuNPs and ERGO onto GCE was conducted to prepare the modified electrode, GCE/AuNPs-ERGO. The poly(indole-5-carboxylic acid) (P(In-5-COOH) was then coated onto the GCE/AuNPs-ERGO with the help of electropolymerization. FT-IR, FE-SEM and EDX, and XRD techniques were employed to characterize the prepared nanocomposite. The nanocomposite modified electrode (GCE/AuNPs-ERGO/P(In-5-COOH)) was examined for the electrochemical reduction of H₂O₂ using chronoamperometry. A high reduction current for H₂O₂ was observed due to the synergistic effect between AuNPs-ERGO and P(In-5-COOH). The proposed sensor demonstrated a wide linear range of 0.025–750 μmol L⁻¹, with a LOD of 0.008 μmol L⁻¹ at −0.4 V. Furthermore, the developed sensor was applied for the detection of H₂O₂ in fetal bovine serum and urine samples.     

二氧化钛纳米颗粒/还原氧化石墨烯修饰玻碳电极在对硝基苯酚检测中的应用

本文报道了用二氧化钛纳米颗粒（TiO₂NPs）/还原氧化石墨烯（RGO）的复合物修饰玻碳电极检测微量对硝基苯酚（4-NP）的电化学方法. 本研究用扫描电子显微镜（SEM）对该复合材料形貌进行表征,用循环伏安法和交流阻抗谱对该复合物电极的电化学性能进行检测,表现出良好的电化学特性,采用差分脉冲伏安法对4-NP进行微量检测,结果令人满意,这主要得益于TiO2NPs/RGO复合物对4-NP有较高的催化活性,其电流峰值与浓度呈较高的线性关系,DPV的检测范围为10μmol·L^-1 ~ 350μmol·L^-1,检测限为0.13 μmol·L^-1. 与其他报道的一些电化学传感器相比,该传感器检测范围大,检测限低,且工作稳定,成本低,分析简单快速,具有很好的应用前景.     

Enzyme‐free Glucose Sensor Fabricated by Nanorods Decorated Nanopore Arrays on Biomedical Stainless Steel

A novel enzyme‐free glucose sensor was proposed by preparation of nanorods decorated nanopore arrays (NRs/NPAs) on 316L stainless steel simply by electrochemical treatments. The NRs/NPAs sensor displays two linear ranges towards glucose determination, one range from 1 μM to 1.2 mM with a sensitivity of 202.2 μA ? cm^?2 ? mM^?1, another range from 1.2 mM to 7.7 mM with a sensitivity of 59.18 μA?cm^?2 ? mM^?1. The detection limit is 0.5 μM. The NRs/NPAs electrode exhibits excellent stability, good selectivity and reproducibility, rendering it suitable for glucose monitoring.     

Facile Synthesis of Graphene/Cobalt Oxide Nanohexagons for the Selective Detection of Dopamine

This work presents a simple green approach for the chemical synthesis of cobalt oxide nano hexagons (Co₃O₄ NHs) with an average size of 160±40 nm incorporated graphene nanosheets (GR). The techniques used to confirm the formation of GR−Co₃O₄ NHs are transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), and X‐ray diffraction spectroscopy (XRD). The dopamine (DA) sensor was fabricated by drop casting GR−Co₃O₄ NHs on the pre‐cleaned glassy carbon electrode (GCE). GR−Co₃O₄ modified GCE displayed a sensitive and selective electrochemical determination of DA compared to only GR and Co₃O₄ NHs modified GCE. Our fabricated sensor showed a wide linear range from 0.2 to 3443 μM with low limit of detection (84 nM) towards the determination of DA. The sensitivity of our fabricated sensor was calculated to be 108 μA mM⁻¹ cm⁻². As well, a significant storage stability, repeatability and reproducibility were attained by GR−Co₃O₄ NHs modified GCE. Human urine samples were targeted for the demonstration of practicality of our sensor.     

Ferrocene Decorated N-doped Carbon Modified Electrode with Enhanced Electrocatalytic Activity towards Non-enzymatic Glucose Detection

The nitrogen doped carbon (NDCN) have been synthesized by flame synthetic method to prepare ferrocene decorated NDCN. The hydrolysis product (FC-SH) of ferrocene benzyne derivative (FC-SAc) was immobilized onto NDCN modified GCE and used for glucose detection with high sensitivity. Cyclic voltammetric analysis reveal that FC-S-NDCN/GCE exhibit excellent activity for glucose oxidation when compared to FC/GCE. The FC-S-NDCN/GCE with wide linear responses range from 0.001 to 0.01 mM with the regression co-efficient of 0.998. The FC-S-NDCN/GCE show low detection limit (LOD) of 0.08 μM and exhibit sensitivity of 1580 μA mM⁻¹ cm⁻². The FC-S-NDCN glucose sensor exhibit wide linear range, high sensitivity and lower detection limit on determination of glucose.     

Polyaniline Nanowire Arrays Deposited on Porous Carbon Derived from Raffia for Electrochemical Detection of Imidacloprid

An electrochemical sensor based on raffia derived porous carbon (RPC) and polyaniline (PANI) composite functional glass carbon electrode (GCE) was constructed for imidacloprid (IMI) determination. PANI nanowire arrays were deposited on RPC surface uniformly without aggregations. The electrochemical response of IMI at RPC@PANI/GCE is about four times than that at bare GCE, indicating high electrocatalytic activity of RPC@PANI towards IMI reduction. The prepared sensor also offers a wide linear range of 0.1–70 μg mL⁻¹ for IMI determination with a limit of detection (LOD) of 0.03 μg mL⁻¹. In addition, it offers high recoveries with testing real samples.     

Polyaniline-ZnO−NiO Nanocomposite Based Non-enzymatic Electrochemical Sensor for Malathion Detection

An electrochemical sensor based on polyaniline-ZnO−NiO (PANI-ZnO−NiO) nanocomposite was developed for the non-enzymatic detection of malathion. The structure, surface morphology, and optical properties of the as-prepared nanocomposite were studied by XRD, FTIR, SEM, and UV-Vis spectroscopy. The electrochemical behavior of the nanocomposite based sensor was first evaluated through cyclic voltammetry (CV). Under optimum conditions, differential pulse voltammetry (DPV) was further utilized for malathion detection, which proved the PANI-ZnO−NiO/GCE electrode as an effective electrochemical sensor. The developed electrochemical sensor showed a low detection limit of 1.0×10⁻⁸ M with a wider linear range of 10 to 70 nM for malathion.     

Electrochemical Determination of Dicofol at Nickel Nanowire Modified Poly(p‐aminophenol) Film Electrode

An electrochemical sensor was fabricated by construction of nickel nanowires on the surface of poly(p‐aminophenol) (PPAP) modified glassy carbon electrode. The electrochemical response of dicofol, a known pesticide and used for agricultural activities such as cyclic voltammetry and differential pulse voltammetry, were investigated and the results were compared with those obtained unmodified electrodes. Following the optimization of NaOH concentration, polymerization cycle number, Ni nanowire amount, the linear range for the dicofol was studied and found as 0.83–30.7 μmol L^?1 (R²=0.9981) at Ni/PPAP/GCE with a 0.08 μmol L^?1 detection limit according to S/N=3. Finally, the proposed Ni/PPAP/GCE sensor was successfully applied for the dicofol analysis in soil samples. The characterization of the developed surface was carried out by scanning electron microscopy and X‐Ray photoelectron spectroscopy.     

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.     

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.     

Ferrite Nanocomposite Based Electrochemical Sensor: Characterization,Voltammetric and Amperometric Studies for Electrocatalytic Detection of Formaldehyde in Aqueous Media

Development of nanocomposite based electrochemical sensors for detection of toxic chemicals describes an environmentally benign strategy for monitoring the health of ecosystem. Herein, we reported in situ preparation of graphitic carbon nitride (g-C₃N₄) decorated Ag₂S/NiFe₂O₄ nanocomposite sensor by facile precipitation method. The electrochemical studies demonstrated efficient electrocatalytic activity of ternary nanocomposite pasted glassy carbon electrode (g-C₃N₄@Ag₂S/NiFe₂O₄/GCE) for selective detection of formaldehyde. Moreover, fabricated sensor exhibit rapid amperometric response with excellent selectivity, remarkable sensitivity (1681 μA mmol L⁻¹ cm⁻²) and lower detection limit (LOD: 1.63 μmol L⁻¹). It is noteworthy to mention that sensor exhibits good operational and long-term storage stability.     

Over‐Oxidized Poly (Phenol Red) Film Modified Glassy Carbon Electrode for Anodic Stripping Voltammetric Determination of Ultra‐Trace Antimony (III)

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over‐oxidized poly(phenol red) modified glassy carbon electrode (PPhRed_ox/GCE) in 0.1 mol L^‐1 HCl medium. The formation of both poly(phenol red) and over‐oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRed_ox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRed_ox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 ‐ 1.218 μg L⁻¹ and 3.40 – 18.26 μg L⁻¹ with a detection limit of 0.0075 μg L⁻¹. The proposed over‐oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE‐EnviroMAT™ EP−L‐2).     

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.