Lignosulfonate-Assisted In Situ Deposition of Palladium Nanoparticles on Carbon Nanotubes for the Electrocatalytic Sensing of Hydrazine.

This paper presents a novel modified electrode for an amperometric hydrazine sensor based on multi-walled carbon nanotubes (MWCNTs) modified with lignosulfonate (LS) and decorated with palladium nanoparticles (NPds). The MWCNT/LS/NPd hybrid was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The electrochemical properties of the electrode material were evaluated using cyclic voltammetry and chronoamperometry. The results showed that GC/MWCNT/LS/NPd possesses potent electrocatalytic properties towards the electro-oxidation of hydrazine. The electrode demonstrated exceptional electrocatalytic activity coupled with a considerable sensitivity of 0.166 µA µM-1 cm-2. The response was linear from 3.0 to 100 µM L-1 and 100 to 10,000 µM L-1, and the LOD was quantified to 0.80 µM L-1. The efficacy of the modified electrode as an electrochemical sensor was corroborated in a study of hydrazine determination in water samples.

Synthesis, Electrochemical and Photochemical Properties of Sulfanyl Porphyrazine with Ferrocenyl Substituents.

Ferrocene is useful in modern organometallic chemistry due to its versatile applications in material sciences, catalysis, medicinal chemistry, and diagnostic applications. The ferrocene moiety can potentially serve many purposes in therapeutics and diagnostics. In the course of this study, (6-bromo-1-oxohexyl)ferrocene was combined with dimercaptomaleonitrile sodium salt to yield a novel maleonitrile derivative. Subsequently, this compound was subjected to an autocyclotetramerization reaction using the Linstead conditions in order to obtain an octaferrocenyl-substituted magnesium(II) sulfanyl porphyrazine. Following that, both compounds-the maleonitrile derivative and the porphyrazine derivative-were subjected to physicochemical characterization using UV-Vis, ES-TOF, MALDI-TOF, and one-dimensional and two-dimensional NMR spectroscopy. Moreover, the sulfanyl porphyrazine was subjected to various photophysical studies, including optical absorption and emission measurements, as well as the evaluation of its photochemical properties. Values of singlet oxygen generation quantum yields were obtained in different organic solvents. The electrochemical properties of the synthesized compounds were studied using cyclic voltammetry. According to the electrochemical results, the presence of electron-withdrawing oxohexyl groups attached to ferrocene afforded significantly more positive oxidation potentials of the ferrocene-based redox process up to 0.34 V vs. Fc+/Fc.

Improved Electrochemical Hydrogen Peroxide Detection Using a Nickel(II) Phthalimide-Substituted Porphyrazine Combined with Various Carbon Nanomaterials.

A metal-free porphyrazine derivative with peripheral phthalimide substituents was metallated with a nickel(II) ion. The purity of the nickel macrocycle was confirmed using HPLC, and characterized by MS, UV-VIS, and 1D (1H, 13C) and 2D (1H-13C HSQC, 1H-13C HMBC, 1H-1H COSY) NMR techniques. The novel porphyrazine was combined with various carbon nanomaterials, such as carbon nanotubes-single walled (SWCNTs) and multi-walled (MWCNTs), and electrochemically reduced graphene oxide (rGO), to create hybrid electroactive electrode materials. The carbon nanomaterials' effect on the electrocatalytic properties of nickel(II) cations was compared. As a result, an extensive electrochemical characterization of the synthesized metallated porphyrazine derivative on various carbon nanostructures was carried out using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). An electrode modified with carbon nanomaterials GC/MWCNTs, GC/SWCNTs, or GC/rGO, respectively, was shown to have a lower overpotential than a bare glassy carbon electrode (GC), allowing for the measurement of hydrogen peroxide in neutral conditions (pH 7.4). It was shown that among the tested carbon nanomaterials, the modified electrode GC/MWCNTs/Pz3 exhibited the best electrocatalytic properties in the direction of hydrogen peroxide oxidation/reduction. The prepared sensor was determined to enable a linear response to H2O2 in concentrations ranging between 20-1200 µM with the detection limit of 18.57 µM and sensitivity of 14.18 µA mM-1 cm-2. As a result of this research, the sensors produced here may find use in biomedical and environmental applications.

A Synergistic Effect of Phthalimide-Substituted Sulfanyl Porphyrazines and Carbon Nanotubes to Improve the Electrocatalytic Detection of Hydrogen Peroxide.

A sulfanyl porphyrazine derivative with peripheral phthalimide moieties was metallated with cobalt(II) and iron(II) metal ions. The purity of the macrocycles was confirmed by HPLC, and subsequently, compounds were characterized using various analytical methods (ES-TOF, MALDI-TOF, UV-VIS, and NMR spectroscopy). To obtain hybrid electroactive electrode materials, novel porphyrazines were combined with multiwalled carbon nanotubes. The electrocatalytic effect derived from cobalt(II) and iron(II) cations was evaluated. As a result, a significant decrease in the overpotential was observed compared with that obtained with bare glassy carbon (GC) or glassy carbon electrode/carbon nanotubes (GC/MWCNTs), which allowed for sensitive determination of hydrogen peroxide in neutral conditions (pH 7.4). The prepared sensor enables a linear response to H2O2 concentrations of 1-90 µM. A low detection limit of 0.18 µM and a high sensitivity of 640 µA mM-1 cm-2 were obtained. These results indicate that the obtained sensors could potentially be applied in biomedical and environmental fields.

Lignosulfonate-assisted synthesis of platinum nanoparticles deposited on multi-walled carbon nanotubes for biosensing of glucose.

It is presented in this work that lignosulfonate (LS) can be preferentially adsorbed on the surface of multi-walled carbon nanotubes (MWCNT) giving rise to the functional platform for platinum nanoparticles (NPt) deposition. The novel MWCNT/LS/NPt hybrid material has been characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). The morphology of the MWCNT/LS/NPt electrodes has been investigated by atomic force microscopy (AFM). The electrochemical studies of MWCNT/LS/NPt hybrid material revealed strong electrocatalytic properties towards hydrogen peroxide. In addition, the effects of lignosulfonate amount adsorbed at the MWCNT on the voltammetric response of the hydrogen peroxide were discussed and used to select the optimal and effective conditions for the synthesis of the electrode material. An amperometric biosensor for glucose was developed based on the covalent linkage of glucose oxidase (GOx) at the MWCNT/LS/NPt. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for glucose. The linear range of the glucose determination was 50-1400 µM and LOD was quantified as 15.67 µM.