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Because of their unique physical, chemical, and biological characteristics, conductive nanomaterials have a lot of potential for applications in materials science, energy storage, environmental science, biomedicine, sensors/biosensors, and other fields. Recent breakthroughs in the manufacture of carbon materials, conductive polymers, metals, and metal oxide nanoparticles based electrochemical sensors and biosensors for applications in environmental monitoring by detection of catechol (CC) and hydroquinone (HQ) are presented in this review. To achieve this goal, we first introduced recent works that discuss the effects of phenolic compounds and the need for accurate, inexpensive, and quick monitoring, and then we focused on the use of the most important applications of nanomaterials, such as carbon-based materials, metals, and metal oxides nanoparticles, and conductive polymers, to develop sensors to monitor catechol and hydroquinone. Finally, we identified challenges and limits in the field of sensors and biosensors, as well as possibilities and recommendations for developing the field for better future applications. Meanwhile, electrochemical sensors and biosensors for catechol and hydroquinone measurement and monitoring were highlighted and discussed particularly. This review, we feel, will aid in the promotion of nanomaterials for the development of innovative electrical sensors and nanodevices for environmental monitoring.Research HighlightsThe most commonly used procedures to prepare electroechemical sensors for catechol and hydroquinone monitoring are described.The electroanalytical techniques have been compared and evaluated.The essential carbon based materials used to fabricate sensitive and selective electrodes are discussed.Prominent applications of nanomaterials combinations for electrochemical sensors are presented.The potential of novel green synthesis procedures for the future development of electrochemical sensors is outlined.

Reduced graphene oxide/metal organic framework based electrochemical sensor coupled with machine learning for sensitive detection of penta-chlorophenol.

A new electrochemical sensor is reported based on a modified platinum (Pt) electrode sequentially drop-casting doped with functionalized multi-walled carbon nanotubes (fMWCNTs) decorated by reduced graphene oxide (rGO) and nickel oxide (NiO) nanoparticles (NPs). The NiO/rGO/fMWCNTs nanohybrid was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). This sensor was employed for the simultaneous determination of catechol and hydroquinone. In the cyclic voltammetry (CV) results for a binary mixture of catechol and hydroquinone, the peak potentials of the two dihydroxybenzene isomers were separated by more than 105 mV, demonstrating the ability of the fabricated sensor to simultaneously determine the analytes. The NiO/rGO/fMWCNTs/Pt electrode exhibited a wide linear range of 10–300 μM with detection limits of 19.86 and 40.18 nM based upon a signal-to-noise ratio of 3 for catechol and hydroquinone, respectively. Furthermore, using differential pulse voltammetry (DPV), the sensor maintained well-defined peaks, demonstrating suitable selectivity. In addition, the NiO/rGO/fMWCNTs/Pt nanocomposite exhibits stability values of 92.3% and 91.6% for catechol and hydroquinone with excellent repeatability. The sensor analyzed water samples with spike recoveries from 90% to 106.66% for catechol and 88% to 98.66% for hydroquinone, respectively.

Electrochemical biointerfaces are constructed with a wide range of nanomaterials and conducting polymers that strongly affect the analytical performance of biosensors. The analysis of progress toward electrochemical sensing platforms offers opportunities to provide devices for commercial use. The investigation of different methods for the synthesis of phenol biointerfaces leads to design challenges in the field of monitoring phenolic compounds. This paper review the innovative strategies and feature techniques in the construction of phenolic compound biosensors. The focus was made on the preparation methods of nanostructures and nanomaterials design for catalytic improvements of sensing interfaces. The paper also provides a comprehensive overview in the field of enzyme immobilization approaches at solid supports and technical formation of polymer nanocomposites, as well as applications of hybrid organic-inorganic nanocomposites in phenolic biosensors. This review also highlights the recent progress in the electrochemical detection of phenolic compounds and summarizes analytical performance parameters including sensitivity, storage stability, limit of detection, linear range, and Michaelis-Menten kinetic analysis. It also emphasizes advances from the past decade including technical challenges for the construction of suitable biointerfaces for monitoring phenolic compounds.

The construction of suitable biosensing platforms for monitoring phenolic compounds has rapidly grown in the last years. In parallel, several efforts have been made to the improvement of physical and chemical properties of biosensing platforms based on nanomaterials and conducting polymers. However, several parameters affecting the analytical performance should be investigated during the preparation of electrochemical biosensors. This chapter describes effects of some basic conditions on the electroanalytical response of biosensors for the determination of phenolic compounds such as the electrochemical technique, immobilization method, nanomaterial combination, concentration of analyte, temperature, and the pH of the supporting electrolyte.

A mathematical model of an amperometric biosensor response for substrate and inhibitor detection has been developed. The model is based on system of reaction–diffusion equations containing a non-linear term related to Michaelis–Menten kinetics of the enzymatic reaction. The equations of the model were modified taking into account the inhibitor effect. The numerical simulation of an amperometric biosensor response was carried out using the implicit finite difference technique. The influence of inhibitor (Hg ++ ) concentration on the invertase activity and the effect of thickness of enzymatic membrane as well as diffusion layer on the biosensor response were investigated. The experimental data of biosensor for mercury ions detection were used to validate the mathematical model. The biosensor responses to various conditions such as, rate of inhibition, reaction time of inhibitor were simulated. The numerical results are compared with experimental ones and are found to be in good agreement.

A novel inhibition biosensor used for the detection of sulphides (Na2S) has been developed. The biosensor is based on the immobilisation of horseradish peroxidase (HRP) on the Sonogel-Carbon (SNGC) electrode using glutaraldehyde, Poly(4-vinylpyridine) and gold sononanoparticles (AuSNPs). The Poly(4-vinylpyridine) was used due to its high affinity for sulphide anions, while the presence of gold sononanoparticles enhances the electron transfer reaction and improves the analytical performance of the biosensor. The amperometric measurements were performed at an applied potential of −0.15 V vs. Ag/AgCl in 50 mM sodium acetate buffer solution pH = 6.0. The apparent kinetic parameters (Kmapp, Vmax) of immobilised HRP were calculated in the absence of inhibitor (sulphide) using caffeic acid as substrate. Under the optimal experimental conditions, the determination of sulphide can be achieved in a dynamic range of 0.4–2.8 µM with a low limit of detection of 0.15 µM. The electrochemical impedance spectroscopy (EIS) was also used to characterise the interactions of substrate and inhibitor with the enzyme-modified electrode. The developed biosensor exhibited high sensitivity, selectivity and stability, and can be successfully applied to the detection of sulphide in water.