Pencil graphite electrode modified with nitrogen-doped graphene and molecular imprinted polyacrylamide/sol-gel as an ultrasensitive electrochemical sensor for the determination of fexofenadine in biological media

The Effect of Polymerization Techniques on the Creation of Molecularly Imprinted Polymer Sensors and Their Application on Pharmaceutical Compounds

Molecularly imprinted polymers (MIPs) have become more prevalent in fabricating sensor applications, particularly in medicine, pharmaceuticals, food quality monitoring, and the environment. The ease of their preparation, adaptability of templates, superior affinity and specificity, improved stability, and the possibility for downsizing are only a few benefits of these sensors. Moreover, from a medical perspective, monitoring therapeutic medications and determining pharmaceutical compounds in their pharmaceutical forms and biological systems is very important. Additionally, because medications are hazardous to the environment, effective, quick, and affordable determination in the surrounding environment is of major importance. Concerning a variety of performance criteria, including sensitivity, specificity, low detection limits, and affordability, MIP sensors outperform other published technologies for analyzing pharmaceutical drugs. MIP sensors have, therefore, been widely used as one of the most crucial techniques for analyzing pharmaceuticals. The first part of this review provides a detailed explanation of the many polymerization techniques that were employed to create high-performing MIP sensors. In the subsequent section of the review, the utilization of MIP-based sensors for quantifying the drugs in their pharmaceutical preparation, biological specimens, and environmental samples are covered in depth. Finally, a critical evaluation of the potential future research paths for MIP-based sensors clarifies the use of MIP in pharmaceutical fields.

Controlled electrochemical surface exfoliation of graphite pencil electrodes for high-performance supercapacitors

A controlled surface exfoliation method for graphite pencil electrodes using an environmentally friendly, low cost and scalable electrochemical process is reported. A simple direct current power supply in a neutral medium is used for inducing graphene formation on the electrode surface in a controlled manner. The electrochemical properties of the surface exfoliated electrode are characterized, displaying a >300× increase in the electrochemical surface area and >50× decrease in the electrode resistance after exfoliation. The surface graphene layer is characterized using electron microscopy, Raman, infrared, X-ray photoelectron, and energy dispersive X-ray spectroscopies and X-ray diffractometry showing a fully exfoliated surface, formation of surface defects and mild surface graphene oxidation while maintaining an intact graphitic crystal structure. The surface exfoliated electrode is tested as a supercapacitor demonstrating more than 2 orders of magnitude improvement over non-exfoliated electrode in both 3-electrode and 2-electrode setups and achieving a high areal capacitance of ∼54 mF cm^-2. The benign nature, low cost, scalability of our controlled surface exfoliation methodology, and its significant impact on the electrochemical properties of the electrode make it very promising for further investigation in various applications such as energy storage and conversion, sensors, and catalysis.

A review on optimistic development of polymeric nanocomposite membrane on environmental remediation

Current health and environmental concerns about the abundance and drawbacks of municipal wastewater as well as industrial effluent have prompted the development of novel and innovative treatment processes. A global shortage of clean water poses significant challenges to the survival of all life forms. For the removal of both biodegradable and non-biodegradable harmful wastes/pollutants from water, sophisticated wastewater treatment technologies are required. Polymer membrane technology is critical to overcoming this major challenge. Polymer matrix-based nanocomposite membranes are among the most popular in polymer membrane technology in terms of convenience. These membranes and their major components are environmentally friendly, energy efficient, cost effective, operationally versatile, and feasible. This review provides an overview of the drawbacks as well as promising developments in polymer membrane and nanocomposite membranes for environmental remediation, with a focus on wastewater treatment. Additionally, the advantages of nanocomposite membranes such as stability, antimicrobial properties, and adsorption processes have been discussed. The goal of this review was to summarize the remediation of harmful pollutants from water and wastewater/effluent using polymer matrix-based nanocomposite membrane technology, and to highlight its shortcomings and future prospects.

Electrochemical assay of acetamiprid in vegetables based on nitrogen-doped graphene/polypyrrole nanocomposites

Dual-mode electrochemical aptasensor based on nitrogen-doped graphene (NG) doped with the conducting polymer polypyrrole (PPy) nanocomposite is proposed for the determination of acetamiprid. NG/PPy was electrodeposited onto the glassy carbon electrode (GCE) using cyclic voltammetry technique. NG/PPy/GCE showed outstanding electrocatalytic activity for the oxidation of nitrite due to "active region" induced by the charge redistribution of carbon atoms. The ultrasensitive dual-mode biosensor for acetamiprid could be easily developed by coupling acetamiprid aptamers with the NG/PPy hybrid. The specific binding between acetamiprid and the aptamers resulted in the increase of differential pulse voltammetry (DPV) signal change and the decrease of chronoamperometry (CA) signal, and the concentration of acetamiprid could be measured. The working potentials of DPV and CA were - 0.2 ~ 0.4 V and - 0.4 ~ 0.4 V (vs. SCE), respectively. The dual-mode acetamiprid biosensor showed a wide linear range from 10^-12 to 10^-7 g mL^-1, with low detection limits of 1.15 × 10^-13 g mL^-1 and 7.32 × 10^-13 g mL^-1 through DPV and CA modes, respectively. Moreover, owing to high active area and superior conductivity, as well as good electrocatalytic ability, the dual-sensing platform based on NG/PPy nanocomposite supported the quantification of acetamiprid in complex samples. A dual-mode electrochemical aptasensor based on NG/PPy nanocomposite for acetamiprid detection was proposed through both the increase of differential pulse voltammetry (DPV) signal change and the decrease of chronoamperometry (CA) signal of the nitrite oxidation electrocatalyzed by NG/PPyn in sensors and biosensors.

Electrochemical determination of acetamiprid using PEDOT sensing coating functionalized with carbon quantum dots and Prussian blue nanoparticles

A dual-mode electrochemical biosensor for acetamiprid detection was proposed for the first time based on carbon quantum dots/Prussian blue (CQDs/PB)-functionalized poly(3,4-ethylenedioxythiphene) (PEDOT) nanocomposite. The nanocomposite with spherical stacking nanostructure showed high surface area, excellent catalytic ability, and cycling stability. The biosensor can be effortlessly constructed after the immobilization of acetamiprid aptamer. The concentration of acetamiprid can be determined by differential pulse voltammetry (DPV) based on its signal change deduced from the pristine PB. With the capture of acetamiprid, the response current (I-T) signal generated by hydrogen peroxide catalysis from the biosensor can also been used to establish the method for monitoring acetamiprid. The dual-mode biosensor showed a wide linear range from 10^-12 g mL^-1 to 10^-6 g mL^-1, low detection limits of 6.84 × 10^-13 g mL^-1 and 4.99 × 10^-13 g mL^-1, and ultrafast detection time of 25 s and 5 s through DPV and I-T mode, respectively. The biosensor possessed excellent selectivity and stability. More importantly, the biosensor was successfully applied to detect acetamiprid residues in vegetables, proving a promising approach for routine detection of pesticide in real samples. The biosensor based on PEDOT/CQDs/PB for acetamiprid can be effortlessly constructed through both the increase of differential pulse voltammetry (DPV) signal change deduced by the pristine PB and the decrease of the response current (I-T) signal of the reduction of hydrogen peroxide catalyzed by PEDOT/CQDs/PB.

Recent developments on graphene and its derivatives based electrochemical sensors for determinations of food contaminants

The sensing of food contaminants is essential to prevent their adverse health effects on the consumers. Electrochemical sensors are promising in the determination of electroactive analytes including food pollutants, biomolecules etc. Graphene nanomaterials offer many benefits as electrode material in a sensing device. To further improve the analytical performance, doped graphene or derivatives of graphene such as reduced graphene oxide and their nanocomposites were explored as electrode materials. Herein, the advancements in graphene and its derivatives-based electrochemical sensors for analysis of food pollutants were summarized. Determinations of both organic (food colourants, pesticides, drugs, etc.) and inorganic pollutants (metal cations and anions) were considered. The influencing factors including nature of electrode materials and food pollutants, pH, electroactive surface area etc., on the sensing performances of modified electrodes were highlighted. The results of pollutant detection in food samples by the graphene-based electrode have also been outlined. Lastly, conclusions and current challenges in effective real sample detection were presented.

Recent Developments in Voltammetric Analysis of Pharmaceuticals Using Disposable Pencil Graphite Electrodes

The even growing production of both well-known and new derivatives with pharmaceutical action involves the need for developing facile and reliable methods for the analysis of these compounds. Among the widely used instrumental techniques, the electrochemical ones are probably the simplest and the most rapid, also having good performance characteristics. However, the key tool in electroanalysis is the working electrode. Due to the inherent electrochemical and economic advantages of the pencil graphite electrode (PGE), the interest in its applicability in the analysis of different analytes has continuously increased in recent years. Thus, this paper aims to review the scientific reports published in the last 10 years on the use of the disposable eco- and user-friendly PGEs in the electroanalysis of compounds of pharmaceutical importance in different matrices. The PGE characteristics and designs (bare or modified with various types of materials), along with their applications and performance parameters (e.g., linear range, limit of detection, and reproducibility), will be discussed, and their advantages and limitations will be critically emphasized.

Voltammetric picomolar determination of mercury, copper and cadmium using modified pencil graphite electrode with poly-L-cysteine and Fe3O4 nanoparticles

Cost-effective simultaneous determination of mercury, copper and cadmium ions was performed by differential pulse anodic stripping voltammetry (DPASV) using a pencil graphite electrode (PGE) modified with poly-L-cysteine (P-L-Cys) and Fe₃O₄ nanoparticles. Electropolymerization of L-cysteine was performed by cyclic voltammetry (CV) through applying different cycles. Also, Fe₃O₄ was deposited in a single step by applying a constant potential on the electrode surface in the presence of ferric nitrate. To enhance the sensitivity of measurement, several parameters such as monomer concentration, scan rate, number of cycles in electropolymerization, ferric nitrate concentration, Fe₃O₄ electrodeposition potential and time, and pH of the sample solution were optimized. The surface morphology of the modified electrode was examined by SEM and FTIR. Electrochemical impedance spectroscopy was conducted to investigate the impedance of the electrode surface. The linear ranges for cadmium, copper and mercury were 0.001‒2500, 0.0002‒3600 and 0.0001‒2500 nM with detection limits of 6.4 × 10^-13, 1.0 × 10^-13 and 9.0 × 10^-14 M, respectively. The stability and reproducibility of the electrode were investigated. Finally, the modified electrode was applied to determine mercury, copper and cadmium in real samples such as the groundwater, Caspian Sea and Tajan River water.