Simultaneous determination of hydroquinone and catechol using a glassy carbon electrode modified with gold nanoparticles, ZnS/NiS@ZnS quantum dots and L-cysteine

Molecularly imprinted electrochemiluminescence sensor based on ZIF-8 doped with CdSe quantum dots for the detection of trace estriol

A composite of the metal-organic framework compound ZIF-8 doped with CdSe quantum dots (QDs) with sensitive and stable luminescence was synthesized, and a molecularly imprinted electrochemiluminescence (ECL) sensor was constructed on the basis of this composite. The ZIF-8@CdSe molecularly imprinted ECL sensor combines the high sensitivity of ECL and the high selectivity of molecular imprinting to realize the sensitive and specific detection of estriol. CdSe QDs and gold nanoparticles were encapsulated within ZIF-8 to obtain the ZIF-8@CdSe QDs/GNP (ZIF@CdSe/GNP) composite. Subsequently, the GNPs were further loaded on the surface of this composite to obtain the GNP/ZIF@CdSe/GNP composite. L-cysteine was used to immobilize the GNP/ZIF@CdSe/GNP composite on the surface of a gold electrode to obtain the GNP/ZIF@CdSe/GNP-modified gold electrode. A molecularly imprinted polymer (MIP) film was prepared on the surface of the modified electrode via electropolymerization with o-phenylenediamine as the functional monomer and estriol as the template molecule. After elution, estriol could be specifically recognized by the cavities. The re-adsoption of estriol by the MIP can prevent the coreactant from reaching the electrode surface through the cavities, thereby weakening ECL. A good linear relationship existed between the ∆ECL and lg C of estriol concentrations of 1 × 10^-14 - 1 × 10^-9 mol·L^-1 . The detection limit was as low as 8.9 × 10^-16 mol·L^-1 . The sensor was applied in the determination of estriol in serum samples with a recovery of 97.0 % - 102 %.

Nanomaterials for electrochemical detection of pollutants in water: A review

The survival of living beings, including humanity, depends on a continuous supply of clean water. However, due to the development of industry, agriculture, and population growth, an increasing number of wastewaters is discarded, and the negative effects of such actions are clear. The first step in solving this situation is the collection and monitoring of pollutants in water bodies to subsequently facilitate their treatment. Nonetheless, traditional sensing techniques are typically laboratory‐based, leading to potential diminishment in analysis quality. In this paper, the most recent developments in micro‐ and nano‐electrochemical devices for pollutant detection in wastewater are reviewed. The devices reviewed are based on a variety of electrodes and the sensing of three different categories of pollutants: nutrients and phenolic compounds, heavy metals, and organic matter. From these electrodes, Cu, Co, and Bi showed promise as versatile materials to detect a grand variety of contaminants. Also, the most commonly used material is glassy carbon, present in the detection of all reviewed analytes.

Rapid synthesis of a hybrid of rGO/AuNPs/MWCNTs for sensitive sensing of 4-aminophenol and acetaminophen simultaneously

In this work, a hybrid of multiwalled carbon nanotubes, nanogold, and reduced graphene (rGO/AuNPs/MWCNTs) was synthesized rapidly with an easy method, and then combined with chitosan (CS), which was fixed on a glassy carbon electrode (GCE) to construct a new kind of electrochemical sensor to simultaneously determine 4-aminophenol (4-AP) and acetaminophen (AC). When detecting 4-AP and AC simultaneously, the linear range is 0.12~12 μM for acetaminophen and 0.05~25 μM for 4-aminophenol; the detection limit is 42 nM for acetaminophen and 2.95 nM for 4-aminophenol. Compared with previously related reports, the proposed sensor has an excellent electrocatalytic performance for the redox of 4-AP and AC, which can effectively determine 4-AP and AC simultaneously in actual samples and has potential application prospect. Graphical abstract.

Ultrasonic synthesis of CuO nanoflakes: A robust electrochemical scaffold for the sensitive detection of phenolic hazard in water and pharmaceutical samples

Hydroquinone (HQ), a phenolic compound is expansively used in many industrial applications and due to the utilization of HQ, water pollution tragedies frequently found by the improper handling and accidental outflows. When HQ is adsorbed directly through the skin that create toxic effects to human by affecting kidney, liver, lungs, and urinary tract and hence, a highly selective and sensitive technique is required for its quantification. Herein, we have developed the ultrasonic synthesis of copper oxide nanoflakes (CuO-NFs) using ultrasonic bath (20 kHz, 100 W) and successfully employed for the sensitive detection of the environmental hazardous pollutant HQ. The formed CuO-NFs were confirmed by X-ray diffraction, field emission scanning electron microscopy (FE-SEM), FT-IR spectroscopy and UV-visible spectroscopy and fabricated with the screen-printed carbon electrode (SPCE). The SEM images exhibited the uniform CuO-NFs with an average width of 85 nm. The linker-free CuO-NFs fabricated electrode showed the appropriate wide range of concentrations from 0.1 to 1400 µM and the limit of detection was found to be 10.4 nM towards HQ. The fabricated sensor having long term stability and sensitivity was successfully applied for the environmental and commercial real sample analysis and exhibited good recovery percentage, implying that the SPCE/CuO-NFs is an economically viable and benign robust scaffold for the determination of HQ.

Simultaneous detection of acetaminophen and 4-aminophenol with an electrochemical sensor based on silver–palladium bimetal nanoparticles and reduced graphene oxide

Simultaneous detection of acetaminophen and 4-aminophenol with a highly sensitive electrochemical sensor based on silver–palladium bimetal nanoparticles and reduced graphene oxide.

Amperometric determination of hydroquinone and catechol using a glassy carbon electrode modified with a porous carbon material doped with an iron species

A porous carbon material doped with an iron species (Fe/PC) was prepared by carbonizing a mixture of zeolitic imidazolate framework-8 in the presence of iron(II) ions. The resulting material was characterized by X-ray diffraction, nitrogen adsorption isotherms, transmission electron microscopy, and by Raman and X-ray photoelectron spectroscopy. Fe/PC was the deposited on the surface of glassy carbon electrode (GCE) to obtain a sensor for amperometric determination of phenolic compounds. The unique catalytic activity, good electrical conductivity and hierarchical structure of the Fe/PC composite results in good electrooxidative activity towards hydroquinone (HQ; typically at 44 mV) and catechol (CC; typically at 160 mV). Under optimal conditions, the amperometric responses are linear in the range from 0.1 to 120 μmol · L^-1 for HQ, and from 1.0 to 120 μmol · L^-1 for CC. The respective detection limits are 14 and 33 nmol · L^-1. The sensor is highly selective against potential interferents and was successfully applied to the determination of HQ and CC contents in (spiked) water samples. Graphical abstract An amperometric sensor for phenolic compounds was constructed by using a metal-organic framework derived iron doped porous carbon material.

Synthesis and application of bismuth ferrite nanosheets supported functionalized carbon nanofiber for enhanced electrochemical detection of toxic organic compound in water samples

Recently, the multiferroic material has fabulous attention in numerous applications owing to its excellent electronic conductivity, unique mechanical property, and higher electrocatalytic activity, etc. In this paper, we reported that the synthesis of bismuth ferrite (BiFeO₃) nanosheets integrated functionalized carbon nanofiber (BiFeO₃ NS/F-CNF) nanocomposite using a simple hydrothermal technique. Herein, the structural changes and crystalline property of prepared BiFeO₃ NS/F-CNF nanocomposite were characterized using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). From this detailed structural evolution, the formation of nanosheets like BiFeO₃ and its nanocomposite with F-CNF were scrutinized and reported. Furthermore, the as-prepared BiFeO₃ NS/F-CNF nanocomposite modified glassy carbon electrode (GCE) was applied for electrochemical detection of catechol (CC). As expected, BiFeO₃ NS/F-CNF/GCE shows excellent electrocatalytic activity as well as 3.44 (F-CNF/GCE) and 7.92 (BiFeO₃ NS/GCE) fold higher electrochemical redox response for CC sensing. Moreover, the proposed sensor displays a wide linear range from 0.003 to 78.02 µM with a very low detection limit of 0.0015 µM. In addition, we have validated the real-time application of our developed CC sensor in different water samples.

Synergic effect of silver nanoparticles and carbon nanotubes on the simultaneous voltammetric determination of hydroquinone, catechol, bisphenol A and phenol

A glassy carbon electrode (GCE) was modified with multi-walled carbon nanotubes (MWCNT) and silver nanoparticles (AgNPs) and applied to the simultaneous determination of hydroquinone (HQ), catechol (CC), bisphenol A (BPA) and phenol by using square-wave voltammetry. The MWCNTs were deposited on the GCE and the AgNPs were then electrodeposited onto the MWCNT/GCE by the application of 10 potential sweep cycles using an AgNP colloidal suspension. The modified GCE was characterized by using SEM, which confirmed the presence of the AgNPs. The electrochemical behavior of the material was evaluated by using cyclic voltammetry, and by electrochemical impedance spectroscopy that employed hexacyanoferrate as an electrochemical probe. The results were compared to the performance of the unmodified GCE. The modified electrode has a lower charge-transfer resistance and yields an increased signal. The peaks for HQ (0.30 V), CC (0.40 V), BPA (0.74 V) and phenol (0.83 V; all versus Ag/AgCl) are well separated under optimized conditions, which facilitates their simultaneous determination. The oxidation current increases linearly with the concentrations of HQ, CC, BPA and phenol. Detection limits are in the order of 1 μM for all 4 species, and the sensor is highly stable and reproducible. The electrode was successfully employed with the simultaneous determination of HQ, CC, BPA and phenol in spiked tap water samples. Graphical abstract A glassy carbon electrode was modified with carbon nanotubes and silver nanoparticles and then successfully applied to the simultaneous determination of four phenolic compounds. The sensor showed high sensitivity in the detection of hydroquinone, catechol, bisphenol A and phenol in water samples.

Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode

A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0μM-1.0mM range for hydroquinone with the detection limit of 1.2μM and from 30.0μM-1.0mM for catechol with the detection limit of 1.1μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples.