Carbon nanotube β-cyclodextrin modified electrode as enhanced sensing platform for the determination of fungicide pyrimethanil

An electrochemical sensor for the determination of environmentally hazardous fungicide pyrimethanil in water and fruit samples

We developed a facile electroanalytical system for the rapid and sensitive detection of pyrimethanil through the modification of carbon paste electrode surface using the as-fabricated europium doped feather-type CuO nanoflowers (FT-Eu3+-CuO NF sensor). The peak current of pyrimethanil oxidation was elevated by the sensor due to the integration of appreciable electrochemical features of the modifier, which indicates the high ability of the modified electrode to enhance the sensitivity of pyrimethanil detection. The pyrimethanil sensor under the optimized setting had a broad linear dynamic range (0.001-800.0 μM) and a narrow limit of detection (0.18 nM). The practical applicability of the as-fabricated electrode was verified by sensing pyrimethanil in real samples; it also exhibited commendable specificity, stability and reproducibility.

A Review on CNTs-Based Electrochemical Sensors and Biosensors: Unique Properties and Potential Applications

Carbon nanotubes (CNTs), are safe, biocompatible, bioactive, and biodegradable materials, and have sparked a lot of attention due to their unique characteristics in a variety of applications, including medical and dye industries, paper manufacturing and water purification. CNTs also have a strong film-forming potential, permitting them to be widely employed in constructing sensors and biosensors. This review concentrates on the application of CNT-based nanocomposites in the production of electrochemical sensors and biosensors. It emphasizes the synthesis and optimization of CNT-based sensors for a range of applications and outlines the benefits of using CNTs for biomolecule immobilization. In addition, the use of molecularly imprinted polymer (MIP)-CNTs in the production of electrochemical sensors is also discussed. The challenges faced by the current CNTs-based sensors, along with some the future perspectives and their future opportunities, are also briefly explained in this paper.

da Silva Alves D, Okeke C, Breslin CB. Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.

A sensitive pyrimethanil sensor based on porous NiCo2S4/graphitized carbon nanofiber film

With the extensive use of pesticides, the problem of pesticide residues has become people's concern. In this work, NiCo₂S₄ nanoneedle arrays grown on an electrospun graphitized carbon nanofiber film (NiCo₂S₄/GCNF) is successfully prepared by a simple two-step hydrothermal method, and further applied to detection of fungicide pyrimethanil (PMT). NiCo₂S₄ arrays exhibit a unique core-shell structure with rough surface, providing abundant electrochemically active sites exposed to the electrolyte. The NiCo₂S₄/GCNF modified electrode displays excellent electrocatalytic activity, and the electrode surface is controlled both by diffusion and adsorption processes. When applied to PMT determination, NiCo₂S₄/GCNF sensor displays wide linear range from 0.06 to 800 μM with low detection limit (20 nM). Furthermore, the as-proposed sensor also displays other outstanding advantages, including simple preparation, low cost, perfect reproducibility and good application in practical samples. Such attracting analytical properties could be attributed to high electrocatalytic activity of NiCo₂S₄ and superior electrical conductivity of GCNF frameworks. In addition, the detailed oxidation mechanism of PMT at NiCo₂S₄/GCNF electrode was also studied. The results indicate that NiCo₂S₄/GCNF is a promising platform for PMT sensors.

Development of amperometric biosensor in modified carbon paste with enzymatic preparation based on lactase immobilized on carbon nanotubes

Abstract

The variety of products derived from milk, without or with lactose, encourages the development of more effective analytical techniques that can be applied to the quality control of both the production line and the final products. Thus, in this work an efficient and minimally invasive method for the detection of lactose was proposed, using a biosensor containing the enzyme lactase (LAC) immobilised on carbon nanotubes (CNTs) that, when reacting with lactose, emit an electrochemical signal. This biosensor was connected to a potentiostat, and its electrochemical cell was composed of the following three electrodes: reference electrode (Ag/AgCl), auxiliary electrode (platinum wire), and working electrode (biosensor) on which graphite (carbon) paste (CP), CNTs, and LAC were deposited. The transmission electron microscopy and scanning electron microscopy were used in the characterisation of the composite morphology, indicating excellent interactions between the CNTs and LAC. The sensitivity of the CP/LAC/CNT biosensor was determined as 5.67 μA cm^-2.mmol^-1 L and detection limits around 100 × 10^-6 mol L^-1 (electrode area = 0.12 cm²) and an increase in the stability of the system was observed with the introduction of CNTs because, with about 12 h of use, there was no variation in the signal (current). The results indicate that the association between the CNTs and LAC favoured the electrochemical system.

Graphic Abstract

A Sensitive Pyrimethanil Sensor Based on Electrospun TiC/C Film

Titanium carbide (TiC) is a very significant transition metal carbide that displays excellent stability and electrical conductivity. The electrocatalytic activity of TiC is similar to noble metals but is much less expensive. Herein, carbon nanofibers (CNFs)-supported TiC nanoparticles (NPs) film (TiC/C) is prepared by electrospinning and carbothermal processes. Well-dispersed TiC NPs are embedded tightly into the CNFs frameworks. The electrochemical oxidation of pyrimethanil (PMT) at the TiC/C-modified electrode displays enhanced redox properties, and the electrode surface is controlled simultaneously both by diffusion and adsorption processes. When TiC/C is applied for PMT determination, the as-fabricated sensor shows good sensing performance, displaying a wide linear range (0.1⁻600 μM, R² = 0.998), low detection limit (33 nM, S/N = 3), and good reproducibility with satisfied anti-interference ability. In addition, TiC/C shows long-term stability and good application in natural samples. The facile synthetic method with good sensing performance makes TiC/C promising as novel electrode materials to fabricate efficient sensors.

β-Cyclodextrins incorporated multi-walled carbon nanotubes modified electrode for the voltammetric determination of the pesticide dichlorophen

In this work, a glassy carbon electrode modified with β-cyclodextrins and multi-walled carbon nanotubes (β-CDs/MWCNTs/GCE) was constructed and applied for the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the pesticide dichlorophen (Dcp). For the first time, this compound was electrochemically investigated. The voltammetric measurements were conducted in phosphate buffer (PBS) at pH 6.5 as a supporting electrolyte, and SWAdSV technique parameters were optimized. A linear calibration curve in the wide concentration range from 5.0 × 10^-8molL^-1 to 2.9 × 10^-6molL^-1 was obtained. Excellent analytical performance in terms of limit of detection (LOD) of 1.4 × 10^-8molL^-1 was achieved. The utility of the proposed method was verified by the quantitative analysis of Dcp in Pilica River water samples with satisfactory results. The characterization of modified electrodes was conducted by means of atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Moreover, in this work, the dissociation constants (pK_a) of Dcp using potentiometric pH titration were estimated. The stoichiometry of the Dcp-β-CDs inclusion complex formed in solution was determined by proton nuclear magnetic resonance (¹H NMR) spectroscopy, and a binding constant (β₂) was estimated from NMR titration studies.

β-Cyclodextrin carbon nanotube-enhanced sensor for ciprofloxacin detection

A simple and expedite electrochemical methodology was developed for the determination of ciprofloxacin, based on a glassy carbon (GC) electrode modified by a combination of multi-walled carbon nanotubes (MWCNT) with β-cyclodextrin (β-CD) incorporated in a polyaniline film. The combined use of β-CD and MWCNT in the electrochemical sensor leads to a significant signal improvement. The β-CD/MWCNT modified GC electrode exhibited efficient electrocatalytic behavior in the oxidation of ciprofloxacin with relatively high sensitivity, stability and lifetime. Molecular modeling studies showed that ciprofloxacin binds preferably to β-CD rather than to CNT edges, leading to an improved sensitivity of the sensor. Under optimized conditions, a linear calibration curve was obtained for ciprofloxacin in the concentration range 10-80 µM with a detection limit of 50 nM. The analytical performance of this sensor was evaluated for the detection of ciprofloxacin in a wastewater treatment plant effluent.