Nickel-dimethylglyoxime complex modified graphite and carbon paste electrodes: preparation and catalytic activity towards methanol/ethanol oxidation

Nickel oxide nanoparticles modified with dimethylglyoxime grafted on a cellulose surface as an efficient adsorbent for thin film microextraction of tramadol in biological fluids followed by its determination using HPLC

In the current study, nickel oxide nanoparticles (NiO NPs) modified with dimethylglyoxime (DMG) were deposited onto the cellulose surface (Ni(DMG)2-NiO-Cell) and used as an efficient adsorbent for thin film microextraction (TFME) of tramadol (TRA). The extracted TRA was determined using a high-performance liquid chromatography-ultraviolet detector (HPLC-UV). NiO NPs were synthesized by co-precipitation method on the surface of the cellulose substrate; afterward, its surface was modified by DMG to increase the extraction capability of the thin film toward TRA. The synthesized NiO-Cell and Ni(DMG)2-NiO-Cell thin films were characterized using various techniques. The effect of modification of the NiO thin film with DMG reagent on the extraction efficiency was investigated. The crucial parameters influencing the extraction efficiency, including extraction time, desorption time, desorption solvent, pH and salt content, were investigated via a one-at-a-time approach. The figures of merit for the developed method were evaluated in urine, plasma, and deionized water under the optimized extraction and desorption condition. The limits of detection and limits of quantification were in the range of 0.1 to 1 ng mL-1 and 0.3 to 3 ng mL-1, respectively, for the studied samples. The linear dynamic ranges of the developed TFME-HPLC-UV method were 0.3-1000, 1-2500, and 3-5000 ng mL-1 for the deionized water, urine, and plasma samples, respectively. The reproducibility and repeatability of the developed method was assayed in terms of intra-day, inter-day, and inter-thin film precisions by conducting six-replicate experiments at the concentration level of 0.1 and 1 μg mL-1, which were in the range of 5.9% to 8.3%. The sufficiency and applicability of the developed TFME-HPLC-UV method was investigated by determining TRA in urine and plasma samples, and the resulting relative recoveries (RR%) were 85.9% and 91.7%, respectively.

Ni(OH)2-Type Nanoparticles Derived from Ni Salen Polymers: Structural Design toward Functional Materials for Improved Electrocatalytic Performance

Herein, we report the potential-driven electrochemical transformation carried out in basic media of two Ni2+ salen polymers, (poly(NiSalen)s), abbreviated as poly(meso-NiSaldMe) and poly(NiSaltMe). These two polymers, with different configurations of methyl substituents on the imine bridge, were used as precursors for the preparation of electrocatalytically active nickel hydroxide [Ni(OH)2]-type nanoparticles (NPs) anchored in the polymeric matrix as poly[SalenNi(OH)2]. The use of potentiodynamic and potentiostatic electropolymerization conditions for the deposition of polymeric precursors allowed us to control the molecular architecture of poly(NiSalen)s and NPs derived from them. Thus, we obtained different arrangements of NPs embedded in morphologically different poly(Salen) matrixes, indicating their electrocatalytic activity toward ethanol to different extents. Moreover, we found a direct relationship between the electrochemical stability of the poly(NiSalen) precursors operating in the organic solvent-based electrolyte solutions and the easiness of their transformation into Ni(OH)2 NPs operating in the aqueous alkaline media. Poly(NiSalen)s and Ni(OH)2-type NPs were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy.

Bismuth-Chitosan Nanocomposite Sensors for Trace Level Detection of Ni(II) and Co(II) in Water Samples

Trace minerals play an essential role in methane production via anaerobic digestion (AD). It is important to monitor Ni(II) and Co(II) concentrations and the Ni/Co concentration ratio for the rapid diagnosis of the ecological status or activity of methanogens in AD. Electrochemical detection of Ni(II) and Co(II) was investigated by coating the Bi-chitosan nanocomposite on a glassy carbon electrode (GCE) via the electrodeposition technique. A square-wave adsorptive cathodic stripping voltammetry technique (SWAdCSV) was applied and optimized when dimethylglyoxime (DMG) was used as the chelating agent for Ni(II) and Co(II) measurements. The SWAdCSV results showed that the current peaks for Co(II) detection are 6.1 times greater than the current peaks for Ni(II) measurements, probably due to the different affinity of DMG molecules between Ni(II) and Co(II). DMG molecules demonstrated higher selectivity toward Co(II) cations compared to Ni(II). The modified Bi-chitosan GCE developed in this study showed a relatively wide range of the Ni(II) and Co(II) concentrations (2–100 µg L−1) with a limit of detection of 3.6 µg L−1 for Ni(II) and 2.4 µg L−1 for Co(II), respectively. The developed sensor was applied to Ni(II) and Co(II) spiked natural water samples and showed good performance of detection with 12 consecutive measurements. Overall, the fabricated sensor showed excellent sensitivity toward Ni(II) and Co(II) in natural water samples.

Development, Optimization, Characterization, and Application of Electrochemical Biosensors for Detecting Nickel Ions in Food

Nickel is naturally present in drinking water and many dietary items, which expose the general population to nickel ingestion. This heavy metal can have a variety of harmful health effects, causing allergies and skin disorders (i.e., dermatitis), lung, cardiovascular, and kidney diseases, and even certain cancers; therefore, nickel detection is important for public health. Recent innovations in the development of biosensors have demonstrated they offer a powerful new approach over conventional analytical techniques for the identification and quantification of user-defined compounds, including heavy metals such as nickel. We optimized five candidate nickel-biosensing receptors, and tested each for efficiency of binding to immobilization elements on screen-printed electrodes (SPEs). We characterized the application of nickel-detecting biosensors with four different cultivated vegetables. We analyzed the efficiency of each nickel-detecting biosensor by potentiostat and atomic absorption spectrometry and compared the results from the sample analytes. We then analyzed the performance characteristics and responses of assembled biosensors, and show they are very effective at measuring nickel ions in food, especially with the urease-alginate biosensor affixed to silver SPEs, measured by cyclic voltammetry (sensitivity-2.1921 µA Mm-1 cm-2 and LOD-0.005 mg/L). Given the many advantages of biosensors, we describe an optimization pipeline approach to the application of different nickel-binding biosensors for public health, nutrition, and consumer safety, which are very promising.

Electrochemical aptasensor using boron-carbon nanorods decorated by nickel nanoparticles for detection of E. coli O157:H7

The development of a label-free impedimetric aptasensor is reported for rapid and sensitive detection of Escherichia coli O157:H7 employing boron-carbon nanorods decorated by nickel nanoparticles (BC-Ni) nanostructured platform. These highly electroactive BC-Ni nanorods were synthesized to increase the sensitivity of the sensor surface and subsequently functionalized with a specific anti-E. coli O157:H7 aptamer (K_d = 69 nM) as bio-recognition moiety. This fully characterized high-affinity DNA aptamer against the bacteria was selected using a facile microtiter plate-based cell-SELEX methodology. The fabricated electrochemical aptasensor is demonstrated to detect E. coli O157:H7 selectively with a detection limit of 10 cfu and a dynamic detection range of 10⁰ to 10⁵ cfu in water, juice, and fecal samples. Graphical abstract.

Study on Thermal Decomposition Behavior, Gaseous Products, and Kinetic Analysis of Bis-(Dimethylglyoximato) Nickel(II) Complex Using TG-DSC-FTIR-MS Technique

The fiber-like bis-(dimethylglyoximato) nickel(II) complex, Ni(DMG)2 was successfully synthesized. The obtained samples were characterized by SEM-EDS, FT-IR, XRD, and XPS. The TG-DSC-FTIR-MS coupling technique was used to characterize the thermal decomposition behavior and evolved gas analysis of Ni(DMG)2. The non-isothermal decomposition reaction kinetic parameters were obtained by both combined kinetic analysis and isoconversional Vyazovkin methods. It was found that Ni(DMG)2 begins to decompose at around 280 °C, and a sharp exothermic peak is observed in the DSC curve at about 308.2 °C at a heating rate of 10 °C·min−1. The main gaseous products are H2O, NH3, N2O, CO, and HCN, and the content of H2O is significantly higher than that of the others. The activation energy obtained by the combined kinetic analysis method is 170.61 ± 0.65 kJ·mol−1. The decomposition process can be described by the random nucleation and growth of the nuclei model. However, it was challenging to attempt to evaluate the reaction mechanism precisely by one ideal kinetic model.

Naphthalene flanked diketopyrrolopyrrole: a new conjugated building block with hexyl or octyl alkyl side chains for electropolymerization studies and its biosensor applications

Naphthalene flanked DPP with hexyl and octyl chain based electropolymerized conjugated polymers exhibits bio-sensing.

Nickel-foam-supported β-Ni(OH)2 as a green anodic catalyst for energy efficient electrooxidative degradation of azo-dye wastewater

Electrochemical oxidative degradation (EOD) is a particularly promising technique for removing organic pollutants from wastewater. However, due to the high overpotential of EOD in conventional anode materials, the energy cost of EOD is usually very high, which greatly promotes the search for highly active, stable, and energy-efficient anodic catalysts. Herein, we demonstrated that nickel-foam-supported (NF-supported) β-Ni(OH)₂ (NF/β-Ni(OH)₂) prepared via a facile hydrothermal method could be used as an energy efficient anode for EOD. The as-prepared 3D porous NF/β-Ni(OH)₂ exhibited high activity toward the electrochemical oxidation of methyl orange (MO) in the low potential region (<1.07 V vs. SCE). This property differs greatly from those of the conventional anode materials that require a high positive potential to keep them active for EOD, making NF/β-Ni(OH)₂ an energy-efficient and active anode material for EOD. With an oxidation current density of 0.25 mA cm⁻², the decolorization of MO was completed within 30 min, and the COD removal after 3h of reaction was 63.0%. The normalized energy consumption for the 3 h degradation of MO was 22.2 kW h (kg COD)⁻¹, which is only a fraction of (or even one tenth of) the values reported in the literature. Moreover, NF/β-Ni(OH)₂ had a good stability and recyclability for EOD. No activity decay was observed during 10 h of EOD and the COD removal remained almost unchanged after four consecutive reaction cycles. We demonstrated experimentally that the NF/β-Ni(OH)₂ anode could generate large amounts of hydroxyl radicals and that the oxidation of MO by hydroxyl radicals was the main mechanism during EOD. We believe that this work opens a new avenue for developing highly active and energy-efficient anode materials that can work in the low potential region for EOD.

A novel NF/β-Ni(OH)₂ catalyst for energy efficient electrochemical degradation of methyl orange was fabricated via a facile hydrothermal method.

Complexation-Based Detection of Nickel(II) at a Graphene-Chelate Probe in the Presence of Cobalt and Zinc by Adsorptive Stripping Voltammetry

The adsorptive stripping voltammetric detection of nickel and cobalt in water samples at metal film electrodes has been extensively studied. In this work, a novel, environmentally friendly, metal-free electrochemical probe was constructed for the ultra-trace determination of Ni2+ in water samples by Adsorptive Cathodic Stripping Voltammetry (AdCSV). The electrochemical platform is based on the adsorptive accumulation of Ni2+ ions directly onto a glassy carbon electrode (GCE) modified with dimethylglyoxime (DMG) as chelating agent and a Nafion-graphene (NGr) nanocomposite to enhance electrode sensitivity. The nafion-graphene dimethylglyoxime modified glassy carbon electrode (NGr-DMG-GCE) shows superior detection capabilities as a result of the improved surface-area-to-volume ratio and enhanced electron transfer kinetics following the incorporation of single layer graphene, while limiting the toxic effects of the sensor by removal of the more common mercury, bismuth and lead films. Furthermore, for the first time the NGr-DMG-GCE, in the presence of common interfering metal ions of Co2+ and Zn2+ demonstrates good selectivity and preferential binding towards the detection of Ni2+ in water samples. Structural and morphological characterisation of the synthesised single layer graphene sheets was conducted by Raman spectrometry, HRTEM and HRSEM analysis. The instrumental parameters associated with the electrochemical response, including accumulation potential and accumulation time were investigated and optimised in addition to the influence of DMG and graphene concentrations. The NGr-DMG-GCE demonstrated well resolved, reproducible peaks, with RSD (%) below 5% and a detection limit of 1.5 µg L-1 for Ni2+ reduction at an accumulation time of 120 s., the prepared electrochemical sensor exhibited good detection and quantitation towards Ni2+ detection in tap water samples, well below 0.1 mg L-1 set by the WHO and EPA standards. This comparable to the South African drinking water guidelines of 0.15 mg L-1.

Synergistic effect of novel redox additives of p-nitroaniline and dimethylglyoxime for highly improving the supercapacitor performances

In present work, we demonstrate a simple but effective strategy for high-performance supercapacitors by adding the p-nitroaniline (PNA) into an alkaline electrolyte of KOH.