Electrochemical determination of Cu(II) ions using glassy carbon electrode modified by some nanomaterials and 3-nitroaniline

The application of multi-walled carbon nanotubes modified pencil graphite electrode for voltammetric determination of favipiravir used in COVID-19 treatment

This study describes the first application of an improved procedure on a pencil graphite electrode decorated with functionalized multi-walled carbon nanotubes (f-MWCNTs/PGE) for the determination of the COVID-19 antiviral drug, favipiravir (FVP). The electrochemical behavior of FVP at f-MWCNTs/PGE was examined by cyclic voltammetry and differential pulse voltammetry (DPV) methods, and it was noted that the voltammetric response significantly increased with the modification of f -MWCNTs to the surface. The linear range and limit of detection from DPV studies were determined as 1-1500 µM and 0.27 µM, respectively. In addition, the selectivity of the method was tested toward potential interferences, which can be present in pharmaceutical and biological samples, and it was found that f-MWCNTs/PGE showed high selectivity for the determination of FVP in the presence of probable interferences. The results with high accuracies and precisions from the obtained feasibility studies also revealed that the designed procedure can be used for accurate and selective voltammetric determination of FVP in real samples.

Graphical abstract

Thermal Exfoliated Graphite/Chitosan Modified Glassy Carbon Electrode for Cu(II) Ion Sensing

Aim:

Here, we report a simple strategy for the preparation of thermally exfoliated graphite (EG) and its application to modify glassy carbon electrode (GCE) surfaces for electrochemical Cu2+ ion sensing.

Method:

The electrochemical Cu2+ sensor was constructed by a layer modification of a glassy carbon electrode (GCE) with exfoliated graphite (EG) and chitosan (CS) as a binder, and CS also supports a large number of -NH2 functional groups for Cu2+ capture.

Result:

Due to the creation of a three-dimensional (3D) structure, the EG/CS-coated GCE (EG/CS/GCE) electrode exhibited a higher sensitivity towards Cu2+ detection than that of modification by graphite/chitosan (GP/CS), chitosan (CS) or graphite intercalated compounds (GIC)/chitosan.

Conclusion:

The proposed method could detect Cu2+ in the range of 10 µM to 3 mM with a detection limit of 0.5 µM and sensitivity of 43.62 μA mM-1.

Simultaneous visualization and quantification of copper (II) ions in Alzheimer's disease by a near-infrared fluorescence probe

The abnormal accumulation of copper ions (Cu²⁺) is considered to be one of the pathological factors of Alzheimer's disease (AD), but the internal relationship between Cu²⁺ and AD progression is still not fully clear. In this work, a sensitive and selective near-infrared fluorescent copper ion probe (DDP-Cu) was designed for quantification and visualization of Cu²⁺ level in lysates, living cells, living zebrafish and brain tissues of drosophila and mice with AD. By using this probe, we demonstrated that the content of Cu²⁺ in the brains of AD mice and drosophila enhanced nearly 3.5-fold and 4-fold than that of normal mice and drosophila, respectively. More importantly, pathogenesis analysis revealed that elevated Cu²⁺ led to changes in factors closely associated with AD, such as the increasing of reactive oxygen species(ROS), the aggregation of amyloid-β protein (Aβ) and nerve cell cytotoxicity. These findings could promote the understanding of the roles between Cu²⁺ and AD.

Simultaneous determination of cadmium(ii), lead(ii), copper(ii) and mercury(ii) using an electrode modified by N/S co-doped graphene

NSRG has superior sensitivity, selectivity, reproducibility, stability and practicality, exhibiting broad application prospects in the field of electrochemical sensing.

Synthesis, characterization and physicochemical studies of copolymers of aniline and 3-nitroaniline

Polyaniline (PA), the versatile conducting polymer, owing to its tunable optoelectronic properties, facile preparation methodology and reversible redox behavior, has elicited much interest among current researchers, particularly in the fields of energy generation storage devices, protective coatings and electrochemical sensors. However, its commercialization has been much restricted due to low solution processability and thermal stability. Recent studies reveal that the above-mentioned challenges can effectively be addressed by copolymerization of PA with suitable components. In addition, the properties of copolymers could be modified and tuned by varying the monomer ratios. Thus, the present work is concerned with the fabrication of poly(aniline-co-3-nitroaniline) with varying compositions obtained by in situ oxidative copolymerization of aniline and 3-nitroaniline by altering the molar ratio of monomers. Optimization of the physicochemical properties such as UV–visible absorption, solubility, thermal stability, electrical conductivity and dielectric signatures, particle size and morphology was achieved by varying the composition of monomeric substituents in these copolymers. Smoother morphology of the copolymer films was revealed by morphological studies via AFM technique and supported by particle size distribution study. The physicochemical trends demonstrated that proper proportions of nitro (–NO2) group in the polymer chain are essential to achieve desired optimal physicochemical properties. Therefore, copolymers are ideally appropriate for multifaceted applications and would promote wider usage of conjugated polymers in various fields of organic-based optoelectronic as well as energy storage devices in the near future.

Electrochemical study of a glassy carbon electrode modified by poly-4-nitroaniline-reduced/murexide and its sensitivity for metal ions

The electrochemical modification of a glassy carbon electrode using reduced poly-4 nitroaniline (P-4NA) and it's applicability for determination of metallic ions was performed in this study. The electrode modification was performed by cyclic voltammetry in the potential range between 0.9 V and 1.4 V vs Ag/Ag⁺ (in 10 mM AgNO₃) at the scan rate of 100 mV/s by 50 cycles in non-aqueous media. The reduction of nitro groups on the P-4NA modified glassy carbon electrode surface was performed in the potential range between -0.1 V and -0.8 V vs Ag/AgCl(Sat. KCl) at a scan rate of 100 mV/s in 100 mM aqueous HCl solution. The reduced P-4NA glassy carbon surface was modified with the murexide. The affinity of the modified glassy carbon electrode with some metallic ions was investigated by electrochemical impedance spectroscopy method in phosphate buffer solution (pH = 5).

Nanocomposite Platform Based on EDTA Modified Ppy/SWNTs for the Sensing of Pb(II) Ions by Electrochemical Method

Heavy metal ions are considered as one of the major water pollutants, revealing health hazards as well as threat to the ecosystem. Therefore, investigation of most versatile materials for the sensitive and selective detection of heavy metal ions is need of the hour. Proposed work emphasizes the synthesis of conducting polymer and carbon nanotube nanocomposite modified with chelating ligand for the detection of heavy metal ions. Carbon nanotubes are having well known features such as tuneable conductivity, low density, good charge transport ability, and current carrying capacity. Conducting polymers are the most reliable materials for sensing applications due to their environmental stability and tuning of conductivity by doping and de-doping. Formation of nanocomposite of these two idealistic materials is advantageous over the individual material, which can help to tackle the individual limitations of these materials and can form versatile materials with ideal chemical and electrical properties. Chelating ligands are the most favorable materials due to their ability of complex formation with metal ions. The present work possesses a sensing platform based on conducting polymer and carbon nanotube nanocomposite, which is stable in various aqueous media and possess good charge transfer ability. Chelating ligands played an important role in the increased selectivity toward metal ions. Moreover, in present investigation Ethylenediaminetetraacetic acid (EDTA) functionalized polypyrrole (Ppy) and single walled carbon nanotubes (SWNTs) nanocomposite was successfully synthesized by electrochemical method on stainless steel electrode (SSE). The electrochemical detection of Pb(II) ions using EDTA-Ppy/SWNTs nanocomposite was done from aqueous media. Cyclic voltammetry technique was utilized for the electrochemical synthesis of Ppy/SWNTs nanocomposite. Ppy/SWNTs nanocomposite was further modified with EDTA using dip coating technique at room temperature. The EDTA-Ppy/SWNTs modified stainless steel electrode (SSE) exhibited good sensitivity and selectivity toward heavy metal ions [Pb(II)]. Detection limit achieved for Pb(II) ions was 0.07 μM.

Comparison of Two Types of Overoxidized PEDOT Films and Their Application in Sensor Fabrication

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were prepared by electro-oxidation on Au microelectrodes in an aqueous solution. Electrolyte solutions and polymerization parameters were optimized prior to overoxidation. The effect of overoxidation time has been optimized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which results in the film overoxidized for 45 s at 1.35 V presenting a strong adsorption. The other one-step overoxidation film prepared by direct CV ranging from −0.6 V to 1.35 V was polymerized for comparison. Scanning electron microscope (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy were used for monitoring morphological changes and the evolution of functional groups. Both of them indicate increased abundant oxygen functional groups and roughness, yet the products exhibit dendritic morphology and piles of spherical protrusions, respectively. Moreover, double-step overoxidized film showed better electrochemical performance toward lead ion sensing. These characterizations highlight some novel properties that may be beneficial for specific sensing applications.

Advances on Aryldiazonium Salt Chemistry Based Interfacial Fabrication for Sensing Applications

Aryldiazonium salts as coupling agents for surface chemistry have evidenced their wide applications for the development of sensors. Combined with advances in nanomaterials, current trends in sensor science and a variety of particular advantages of aryldiazonium salt chemistry in sensing have driven the aryldiazonium salt-based sensing strategies to grow at an astonishing pace. This review focuses on the advances in the use of aryldiazonium salts for modifying interfaces in sensors and biosensors during the past decade. It will first summarize the current methods for modification of interfaces with aryldiazonium salts, and then discuss the sensing applications of aryldiazonium salts modified on different transducers (bulky solid electrodes, nanomaterials modified bulky solid electrodes, and nanoparticles). Finally, the challenges and perspectives that aryldiazonium salt chemistry is facing in sensing applications are critically discussed.