Voltammetric simultaneous determination of catechol and hydroquinone using a glassy carbon electrode modified with a ternary hybrid material composed of reduced graphene oxide, magnetite nanoparticles and gold nanoparticles

Electrochemical Detection of Dihydroxybenzene Isomers at a Pencil Graphite Based Electrode

In this work, an HB pencil electrode (HBPE) was electrochemically modified by amino acids (AAs) glycine (GLY) and aspartic acid (ASA) and designated as GLY-HB and ASA-HB electrodes. They were used in the detection of dihydroxybenzene isomers (DHBIs) such as hydroquinone (HQ), catechol (CC), and resorcinol (RS), by cyclic voltammetry (CV), and by differential pulse voltammetry. HBPE was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. These three electrodes showed a linear relationship of current with concentration of DHBIs, and the electrochemical processes were diffusion controlled in all cases. In simultaneous detection, the limit of detection, based on signal-to-noise ratio (S/N = 3), for HQ, CC, and RS was 12.473, 16.132, and 25.25 μM, respectively, at bare HBPE; 5.498, 7.119, and 14.794 μM, respectively, at GLY-HB; and 22.459, 25.478, and 38.303 μM, respectively, at ASA-HB. The sensitivity for HQ, CC, and RS was 470.481, 363.781, and 232.416 μA/mM/cm², respectively, at bare HBPE; 364.785, 282.712, and 135.560 μA/mM/cm², respectively, at GLY-HB; and 374.483, 330.108, and 219.574, respectively, at ASA-HB. The interference studies clarified the suitability and reliability of the electrodes for the detection of HQ, CC, and RS in an environmental system. Real sample analysis was done using tap water, and the proposed electrodes expressed recovery with high reproducibility. Meanwhile, these three electrodes have excellent sensitivity and selectivity, which can be used as a promising technique for the detection of DHBIs simultaneously.

Insights into the Design and Electrocatalytic Activity of Magnesium Aluminum Layered Double Hydroxides: Application to Nonenzymatic Catechol Sensor

The design of an efficient electrocatalyst for effective trace level determinations of noxious synthetic and or biological compounds is the unceasingly noteworthy conceptual approach for rapid technology. In this work, we designed a magnesium-aluminum layered double hydroxides (Mg-Al LDHs) nanocatalyst and applied it to the electrocatalytic determination of an extremely carcinogenic catechol sensor. A coprecipitation method was employed for synthesizing the nanocatalyst, and the structure, porous nature, and morphology were confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption-desorption isotherm, field emission-scanning electron microscopy, and transmission electron microscopy. The elemental composition was observed by energy dispersive X-ray analysis. The electrochemical studies were investigated with the help of cyclic voltammetry and differential pulse voltammetry techniques. The Mg-Al LDHs-based electrocatalyst was used to detect catechol by electrochemical measurements with different parameters. The proposed catechol sensor shows a wide dynamic range (0.007-200 μM) with a lower level of detection (2.3 nm) and sensitivity (3.57 μA μM^-1 cm^-2). The excellent sensor performance is attributed to the high surface area, fast electron transfer, more active sites, and excellent flexibility. This study depicts the proposed sensor as probable to practical in a scientific investigation. In addition, the modified electrode showed greater selectivity and was used in the detection of fatal contaminants in instant treatment strategies. Moreover, the Mg-Al LDHs confirmed auspicious real sample scrutiny with noteworthy retrieval outcomes in lake water samples which exposed improved consequences.

Recent developments in carbon-based two-dimensional materials: synthesis and modification aspects for electrochemical sensors

This review (162 references) focuses on two-dimensional carbon materials, which include graphene as well as its allotropes varying in size, number of layers, and defects, for their application in electrochemical sensors. Many preparation methods are known to yield two-dimensional carbon materials which are often simply addressed as graphene, but which show huge variations in their physical and chemical properties and therefore on their sensing performance. The first section briefly reviews the most promising as well as the latest achievements in graphene synthesis based on growth and delamination techniques, such as chemical vapor deposition, liquid phase exfoliation via sonication or mechanical forces, as well as oxidative procedures ranging from chemical to electrochemical exfoliation. Two-dimensional carbon materials are highly attractive to be integrated in a wide field of sensing applications. Here, graphene is examined as recognition layer in electrochemical sensors like field-effect transistors, chemiresistors, impedance-based devices as well as voltammetric and amperometric sensors. The sensor performance is evaluated from the material's perspective of view and revealed the impact of structure and defects of the 2D carbon materials in different transducing technologies. It is concluded that the performance of 2D carbon-based sensors is strongly related to the preparation method in combination with the electrical transduction technique. Future perspectives address challenges to transfer 2D carbon-based sensors from the lab to the market. Graphical abstract Schematic overview from synthesis and modification of two-dimensional carbon materials to sensor application.

UV-assisted one-pot synthesis of bimetallic Ag-Pt decorated reduced graphene oxide for colorimetric determination of hydrogen peroxide

Bimetallic Ag-Pt nanoparticles decorated on the surface of reduced graphene oxide (Ag-Pt/rGO) were designed and selected as a nanozyme for the assay of hydrogen peroxide. The nanocomposites were prepared through a one-pot reduction of potassium chloroplatinate, silver nitrate, and graphene oxide under ultraviolet irradiation without using any extra chemical reducing agents or surfactants. The successful formation of Ag-Pt/rGO nanocomposites was confirmed by transmission electron microscopy, energy disperse spectroscopy mapping, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. Significantly, Ag-Pt/rGO nanocomposites possessed excellent peroxidase-like activity toward the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine to form a blue product in the presence of hydrogen peroxide. Steady-state kinetics studies suggested that Ag-Pt/rGO nanocomposites had high affinity to hydrogen peroxide. Based on these properties, a convenient and sensitive method for the colorimetric determination of hydrogen peroxide was developed. Under optimal conditions, the absorbance at 652 nm increases linearly in the 10-100 μM and 100 μM-1 mM ranges of hydrogen peroxide concentration, and the detection limit is 0.9 μM (S/N = 3). The method was successfully applied to the determination of hydrogen peroxide in real water samples. Graphical abstract Ag-Pt/rGO nanocomposites were prepared by a one-pot UV irradiation method and used as a novel nanozyme for colorimetric determination of H₂O₂.

Self-assembled Ti3C2 /MWCNTs nanocomposites modified glassy carbon electrode for electrochemical simultaneous detection of hydroquinone and catechol

A versatile electrochemical sensor based on titanium carbide (Ti₃C₂) and multi-walled carbon nanotubes (MWCNTs) nanocomposite was constructed to detection catechol (CT) and hydroquinone (HQ). To prepare this novel nanocomposite, a self-assembled process was conducted by blending two-dimensional (2D) hierarchical Ti₃C₂ and MWCNTs under ultrasonic-assisted. X-ray diffraction (XRD), High resolution transmission electron microscopy (HR-TEM) and Scanning electron microscopy (SEM) methods as well as electrochemical technique, such as Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) were performed to characterize the Ti₃C₂-MWCNTs nanocomposite and illuminate the electrochemical oxidation process. Under the optimum conditions, wide linear range from 2 μM to 150 μM for both HQ and CT and low detection limit of 6.6 nM for HQ and 3.9 nM (S/N = 3) for CT have been achieved. Impressively, the sensor possesses superior selectivity, ultra-stability, and good repeatability, which was successfully applied for detecting CT and HQ in real industrial waste water sample with recovery of 96.9%-104.7% and 93.1%-109.9% for HQ and CT, respectively. Hence, Ti₃C₂ nanosheeets were proved to be a promising platform to construct electrochemical oxidation sensor in environmental analyses and phenolic isomers detection.

Synergistic effect of a cobalt fluoroporphyrin and graphene oxide on the simultaneous voltammetric determination of catechol and hydroquinone

Graphene oxide (GO) was modified with the cobalt(II) and zinc(II) complexes (CoTFPP and ZnTFPP) of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin in order to improve the electrocatalytic activity of GO towards catechol (CC) and hydroquinone (HQ). It is found that the CoTFPP-modified GO on a glassy carbon electrode (GCE) displays the highest electrocatalytic activity. The response to CC (at 0.14 V vs. SCE) is linear in the 1-220 μM concentration range. The response to HQ (at 0.04 V vs. SCE) extends from 1 μM to 200 μM. The sensitivity and detection limits are 10.40 μA∙μM^-1∙cm^-2 and 0.17 μM for CC, and 8.40 μA∙μM^-1∙cm^-2 and 0.21 μM for HQ. Experimental results indicate that the Co(II) and Zn(II) ions in the porphyrins positively affect the electron transfer rate in the hybrid materials. The GCE modified with CoTFPP/GO was successfully applied to the simultaneous determination of CC and HQ in spiked samples of tap and lake water. Graphical abstract Schematic presentation of a voltammetric method for simultaneous determination of catechol (CC) and hydroquinone (HQ). It is based on the use of a cobalt (II) fluoroporphyrin (CoTFPP) functionalized graphene oxide (GO) hybrid.