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Effectively detecting catechol (CC) and hydroquinone (HQ) simultaneously is crucial for environmental protection and human health monitoring. In the study presented herein, a novel electrochemical sensor for the sensitive simultaneous detection of CC and HQ was constructed based on an electrochemically reduced graphene oxide (ERGO)-modified multi-walled carbon nanotube paste electrode (MWCNTPE). Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical techniques were utilized to characterize the sensing interface and investigate the sensing mechanism. Under the optimal detection conditions, the oxidation peak currents of CC and HQ show a good linear relationship with their concentrations in the range of 0.4–400 μM with a detection limit of 0.083 μM for CC and 0.028 μM for HQ (S/N = 3). Moreover, the sensor exhibits good performance and can be applied successfully in the simultaneous detection of CC and HQ in tap water samples and urine samples with satisfactory results, indicating its promising application prospects. [ABSTRACT FROM AUTHOR]

This study shows that incorporating taro carbon (TC) into a glassy carbon electrode (GCE) significantly enhanced surface charge transfer characteristics and conductivity and successfully separated the hydroquinone (HQ) and catechol (CT). Moreover, TC on the GCE surface reduced the overpotential of HQ and CT oxidation. Using X‐ray diffraction (XRD) analysis, field‐emission scanning electron microscopy (FESEM), and energy dispersive spectroscopy (EDS), the surface morphology and elemental composition of TC was investigated. The enhanced electron transfer process at TC‐GCE was studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) investigation. Scan rate analysis revealed that HQ and CT exhibited a higher oxidation affinity at TC‐GCE, with diffusion‐regulated anodic processes. Quantitative analysis showed a linear detection range of 5–200 μM for both HQ and CT, with LOD values of 0.47 μM for HQ and 0.51 μM for CT respectively. The modified electrode showed excellent selectivity, stability, and high recovery rates for detecting HQ and CT in tap water. [ABSTRACT FROM AUTHOR]

The development of an efficient, precise, and reliable method for identifying hazardous substances in environmental samples has drawn a lot of attention in the current research environment. The process of electrochemical polymerization produces conducting and non-conducting polymers from electroactive monomers on the electrode surface. By adjusting specific interactions between the functional groups on the polymer and the electrode surface, the electrodes modified by electropolymers can be tuned for a particular usage. Here we present an easy, sensitive, and straightforward method for the electro-polymerization of 4-amino-6-chloro-1,3-benzene disulfonamide on a graphite electrode, which allows for the simultaneous determination of hydroquinone (HQ) and catechol (CC). The electrochemical activity of ACBSA-modified pencil graphite electrode (PGE) towards the analytes in contrary to other reported polymer-based sensors is dramatically enhanced in terms of the concentration range and detection limit. The fabricated sensor has a lower detection value of 3.15 μM for CC and 0.6 μM for HQ. The polymer can act as a versatile medium for the electrochemical determination of catechol and hydroquinone in water samples with distinct oxidation peaks. [ABSTRACT FROM AUTHOR]

In this work, the glassy carbon electrode was modified by multi-walled carbon nanotubes, β -cyclodextrin, reduced graphene oxide, and gold nanoparticle nanocomposites GC/MWCNTs/ β -CD-rGO@Au). The GC/MWCNTs/ β -CD-rGO@Au electrode was utilized for simultaneous monitoring of catechol (CC) and hydroquinone (HQ). The modified electrode has a clear pair of voltammetric peaks for CC and HQ, which makes it an appropriate tool for the simultaneous determination of the two isomers. Under optimized conditions, the oxidation peak currents of CC and HQ at GC/MWCNTs/ β -CD-rGO@Au were increased linearly in the 1–173 μ M and 2–80 μ M concentration range with the limit of detection (LOD) (based on S/N = 3) of 0.17 μ M and 0.26 μ M. The GC/MWCNTs/ β -CD-rGO@Au exhibits adequate stability, repeatability, and recovery in analyzing two dihydroxybenzenes isomers. [ABSTRACT FROM AUTHOR]

N-doped hollow carbon spheres loaded with Cu single atoms (Cu SAs/N-CSs) were prepared via an in situ hard-template method. As an electrode catalyst, the Cu SAs/N-CSs electrochemical-sensing properties to hydroquinone (HQ) and catechol (CC) were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), and the linear detection ranges of HQ and CC were 1–324 and 1–123 μM, respectively; the detection limits are 0.33 and 0.17 μM, respectively. The experimental and DFT calculation results show that Cu SAs/N-CSs have stronger adsorption strength and more effective affinity for CC and HQ due to the synergistic effect of dispersed Cu SAs and N-CSs, thus improving the electrocatalytic and sensing properties of CC and HQ. Furthermore, the prepared electrode has been successfully applied to the simultaneous determination of HQ and CC in practical water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Catechol (CT) is a phenolic compound widely used in various industrial sectors, but it is toxic; thus, there is a need for methods that aim to identify and quantify the existence of residues of this material in the environment. In this study a disposable printed electrochemical sensor was developed as an effective alternative for determining CT in water samples. The electrode, called SPEC, was manufactured using the screen-printing method using polyethylene terephthalate (PET) as a support, in which a conductive ink based on carbonaceous materials was used to print the working and auxiliary electrodes and a silver/silver chloride of ink on the reference electrode. The optimal ratio for the conductive ink was 6.25% carbon black, 35.42% graphite, and 58.33% nail polish. The ink obtained was characterized by scanning electron microscopy (SEM). The assessment of the effect of pH on the redox process showed Nernstian behavior (0.057 V pH−1), indicating that the process involves the same number of protons and electrons. Under optimized conditions, with 0.2 mol L−1 acetate buffer at pH 5.0, and by square wave voltammetry, the sensor presented sensitivity values of 0.31 μA L μmol−1, a detection limit of 5.96 μmol L−1, and a quantification limit of 19.87 μmol L−1. The sensor was applied to determine CT in tap water samples, and the results showed recoveries between 97.95 and 100.17%. [ABSTRACT FROM AUTHOR]

An innovative electrochemical sensing method is introduced for dihydroxy benzene (DHB) isomers, specifically hydroquinone (HQ) and pyrocatechol (PCC), employing a zinc-oxide/manganese-oxide/reduced-graphene-oxide (ZnO/MnO2/rGO) nanocomposite (NC) as an electrode modifier material. Comprehensive characterization confirmed well-dispersed ZnO/MnO2 nanoparticles on rGO sheets. Electrochemical analysis revealed the ZnO/MnO2/rGO-NC-based modified electrode possesses low electrical resistance (126.2 Ω), high electrocatalytic activity, and rapid electron transport, attributed to the synergies between ZnO, MnO2 and rGO. The modified electrode demonstrated exceptional electrochemical performance in terms of selectivity for the simultaneous detection of HQ and PCC. Differential pulse voltammetry studies validated the proposed sensor's ability to detect HQ and PCC within linear response ranges of 0.01–115 μM and 0.03–60.53 μM, with detection limits of 0.0055 µM and 0.0053 µM, respectively. Practical validation using diverse water samples showcased excellent percent recovery of HQ and PCC using the ZnO/MnO2/rGO-based electrochemical sensor, underscoring the sensor's potential for real-world applications in environmental monitoring. [ABSTRACT FROM AUTHOR]

An affordable and highly efficient graphite‐coated electrode was developed and applied in this work as a compelling alternative to other modified electrodes in catechol determination. Electrode modification involved a simple deposition process using a commercial graphite dispersion, Aquadag®Acheson. Morphological and electrochemical studies revealed the formation of a uniform layer with enhanced surface area and significant conductivity. Catechol quantification was successfully achieved in the linear concentration range extended up to 80 μmol L−1 with a detection limit of 0.5 μmol L−1 under optimized conditions (pH 7 and an accumulation time of 2 min). Spike‐and‐recovery experiments validated the accuracy of the determination. Unlike hydroquinone, structurally similar compounds such as phenol and resorcinol did not interfere with catechol analysis. The interference posed by hydroquinone was addressed by derivative treatment of the voltammograms allowing peaks resolution. [ABSTRACT FROM AUTHOR]

Abstract Hydroquinone (HQ), catechol (CC) and nitrite (NT) are considered aquatic environmental pollutants. They are highly toxic, harm humans’ health, and damage the environment. Thus, in the present work we introduce a simple and efficient electrochemical sensor for determination of HQ, CC, and NT simultaneously in wastewater sample. The sensor is fabricated by modifying the surface of a glassy carbon electrode (GCE) by two successive thin films from poly(3,4-ethylenedioxythiophene) (PEDOT) and a mixture of carbon nanotubes-graphene oxide (CNT-GRO). Under optimized conditions the HQ, CC, and NT are successfully detected simultaneously in wastewater sample with changing their concentrations in the ranges (0.04 → 100 µM), (0.01 → 100 µM) and (0.05 → 120 µM), the detection limits are 8.5 nM, 3.8 nM and 6.1 nM, respectively. Good potential peak separations: 117 mV and 585 mV are obtained between the HQ-CC, and CC-NT. The sensor has an excellent catalytic capability toward the oxidation of HQ, CC, and NT due to good synergism between its composite components: PEDOT, GRO and CNTs. The features of the sensor are large active surface area, good electrical conductivity, perfect storage stability, good reproducibility, anti-interference capability and accepted recovery rate for HQ, CC, and NT determination in wastewater sample.

In this work, manganese‐based metal‐organic frameworks (MnBDC) were synthesized by solvothermal method and physically mixed with pre‐prepared graphene oxide (GO) to obtain GO/MnBDC, which were calcined to give MnO@C composite coated with reduced graphene oxide (rGO) marked as rGO/MnO@C. The materials were characterized by SEM, XRD, FTIR and XPS. Based on this composite, a novel sensor was constructed on a glassy carbon substrate, which exhibited good electrocatalytic activities to the redox reactions of catechol (CC) and hydroquinone (HQ), enabling simultaneous detection of both analytes. Under optimized conditions, the electrochemical sensor demonstrated a linear range of 0.50–90.00 μM for both CC and HQ detection, with respective detection limits of 0.05 μM and 0.03 μM. Moreover, the sensor exhibited excellent sensitivity, selectivity and accuracy for detecting CC and HQ simultaneous in real samples. [ABSTRACT FROM AUTHOR]

Hydroquinone (HQ), catechol (CC) and nitrite (NT) are considered aquatic environmental pollutants. They are highly toxic, harm humans' health, and damage the environment. Thus, in the present work we introduce a simple and efficient electrochemical sensor for determination of HQ, CC, and NT simultaneously in wastewater sample. The sensor is fabricated by modifying the surface of a glassy carbon electrode (GCE) by two successive thin films from poly(3,4-ethylenedioxythiophene) (PEDOT) and a mixture of carbon nanotubes-graphene oxide (CNT-GRO). Under optimized conditions the HQ, CC, and NT are successfully detected simultaneously in wastewater sample with changing their concentrations in the ranges (0.04 → 100 µM), (0.01 → 100 µM) and (0.05 → 120 µM), the detection limits are 8.5 nM, 3.8 nM and 6.1 nM, respectively. Good potential peak separations: 117 mV and 585 mV are obtained between the HQ-CC, and CC-NT. The sensor has an excellent catalytic capability toward the oxidation of HQ, CC, and NT due to good synergism between its composite components: PEDOT, GRO and CNTs. The features of the sensor are large active surface area, good electrical conductivity, perfect storage stability, good reproducibility, anti-interference capability and accepted recovery rate for HQ, CC, and NT determination in wastewater sample. [ABSTRACT FROM AUTHOR]

Differential pulse voltammetry has often been considered one of the most suitable techniques for electroanalytical applications. However, the voltammetric parameters used are often chosen without a proper examination of their effect on the resulting response. In this lab experiment, the students are guided to a more informed choice of the electrochemical parameters to apply depending on the application sought. In the first part of the experiment, we highlight how each voltammetric parameter affects the signal-to-noise ratio and the resolution of the voltammetric response of hydroquinone, taken as an example of the application of this electrochemical technique. A Design of Experiment is then applied to optimize the intensity and the sharpness of the oxidation peak response. Finally, an analogous approach is followed to optimize the peak resolution of an equimolar hydroquinone and catechol mixture to achieve the best separation among the peak current response for the two electrochemical processes. Thanks to these two experiments, the student will identify the correct choice of parameters to optimize as key factors for achieving the best analytical performance in specific applications. [ABSTRACT FROM AUTHOR]

Cellulose, which is one of the main components of wood biomass, was carbonized and activated by KOH to prepare a hierarchical porous carbon. This biomass derived carbon was successfully utilized as an effective sensor's material for simultaneously determine hydroquinone (HQ) and catechol (CC) through cyclic voltammetry and amperometry techniques. The resulting sensor exhibited wide linear ranges for HQ (0.5–3000 μmol/L) and CC (1–3000 μmol/L), with the detection limits of HQ (0.47 μmol/L) and CC (0.4 μmol/L) by amperometry technique, respectively. In addition, the prepared sensor also possesses good performances including specific selectivity, long lifetime and good applicability. The practical application in domestic lake water samples with satisfied recoveries implies the proposed sensor is promising. These results demonstrate that cellulose containing biomass have potential as an effective precursor of porous carbon materials and are applicable on various electrochemical sensors. [ABSTRACT FROM AUTHOR]

Effectively detecting catechol (CC) and hydroquinone (HQ) simultaneously is crucial for environmental protection and human health monitoring. In the study presented herein, a novel electrochemical sensor for the sensitive simultaneous detection of CC and HQ was constructed based on an electrochemically reduced graphene oxide (ERGO)-modified multi-walled carbon nanotube paste electrode (MWCNTPE). Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical techniques were utilized to characterize the sensing interface and investigate the sensing mechanism. Under the optimal detection conditions, the oxidation peak currents of CC and HQ show a good linear relationship with their concentrations in the range of 0.4–400 μM with a detection limit of 0.083 μM for CC and 0.028 μM for HQ (S/N = 3). Moreover, the sensor exhibits good performance and can be applied successfully in the simultaneous detection of CC and HQ in tap water samples and urine samples with satisfactory results, indicating its promising application prospects.

Hydroquinone (HQ) and catechol (CC) are isomers with similar structures, which destroyed ecosystem balance and human health at an alarming rate. Therefore, it is critical to monitor HQ and CC in the environment simultaneously. Herein, a sensitive electrochemical sensor based on multiwalled carbon nanotubes and covalent polyoxometalate-organic frameworks (CPOFs) modified by nanoparticles (PtNPs@CPOFs-MWCNTs) was designed for the simultaneous detection of HQ and CC. Polyoxometalates (POMs) have been extensively studied in the area of electrochemical sensors because of rich reversible multielectron redox behavior. The porous and long stick-shaped CPOFs was synthesized by solvothermal Schiff base reaction, with NH2-POM-NH2 and 2,5-dimethoxy-phenyl-1,4-diformaldehyde as monomers. Using the porosity and large surface area of CPOFs, the obtained PtNPs@CPOFs nanocomposite showed an improved distribution of electroactive sites. At the same time, highly conductive MWCNTs was incorporated to guarantee the conductivity. Consequently, PtNPs@CPOFs-MWCNTs was obtained to improve the electrical conductivity and electrocatalytic activity. The results showed that the PtNPs@CPOFs-MWCNTs/GCE performed a wide range and low detection limit toward the detection of HQ and CC simultaneously. Furthermore, PtNPs@CPOFs-MWCNTs/GCE also had great stability and anti-interference ability. [ABSTRACT FROM AUTHOR]

Hemicellulose and lignin, which are main components of wood biomass with different structures, were carbonized and activated by KOH to prepare wood biomass‐derived porous carbons (WBM‐PCs). The resulting WBM‐PCs were characterized by SEM, XRD, Raman, FI‐IR, and N2‐adsorption/desorption isotherms, and successfully utilized as an effective modifier on the glassy carbon electrode surface (GCE) for simultaneous electrochemical determination of dihydroxybenzene isomers, i. e. hydroquinone (HQ) and catechol (CC), which are highly toxic and non‐degradable. The resulting WBM‐PCs‐modified GCEs allowed simultaneous determination of HQ and CC with cyclic voltammetry and constant‐potential amperometry. The linear range for determination of HQ by hemicellulose‐derived carbon (HC) was from 1.0 to 3000 μmol/L with the limit of detection (LOD) of 1.05 μmol/L, and that for CC was from 1.0 to 5000 μmol/L with LOD of 0.4 μmol/L. For lignin‐derived carbon (LC), the linear range for HQ was from 0.5 to 1000 μmol/L with LOD of 0.095 μmol/L, and that for CC was from 0.5 to 3000 μmol/L with LOD of 0.15 μmol/L. These results imply that wood biomass (hemicellulose and lignin), which is sustainable, renewable and environment‐friendly material, have potential as an effective precursor of electrochemically active porous carbon materials applicable to various electrochemical sensors. [ABSTRACT FROM AUTHOR]

Purpose: To synthesize and characterize new cocrystals of berberine chloride (BCl) for potential pharmaceutical tablet formulation. Methods: Solutions of BCl with each of three selected cocrystal formers, catechol (CAT), resorcinol (RES), and hydroquinone (HYQ) were slowly evaporated at room temperature to obtain crystals. Crystal structures were solved using single crystal X-ray diffraction. Bulk powders were characterized by powder X-ray diffraction, thermogravimetric-differential scanning calorimetry, FTIR, dynamic moisture sorption, and dissolution (both intrinsic and powder). Results: Single crystal structures confirmed the formation of cocrystals with all three coformers, which revealed various intermolecular interactions that stabilized crystal lattices, including O–H···Cl− hydrogen bonds. All three cocrystals exhibited better stability against high humidity (up to 95% relative humidity) at 25 ℃ and higher intrinsic and powder dissolution rates than BCl. Conclusion: The enhanced pharmaceutical properties of all three cocrystals, as compared to BCl, further contribute to the existing evidence that confirms the beneficial role of cocrystallization in facilitating drug development. These new cocrystals expand the structure landscape of BCl solid forms, which is important for future analysis to establish a reliable relationship between crystal structure and pharmaceutical properties. [ABSTRACT FROM AUTHOR]

The conversion of metal-organic frameworks (MOFs) into advanced functional materials offers a promising route for producing unique nanomaterials. MOF-derived systems have the potential to overcome the drawbacks of MOFs, such as low electrical conductivity and poor structural stability, which have hindered their real-world applications in certain cases. In this study, laser scribing was used for pyrolysis of a Cu-based MOF ([Cu4{1,4-C6H4(COO)2}3(4,4′-bipy)2]n) to synthesize a Cu-CuO@C composite on the surface of a screen-printed electrode (SPE). Scanning electron microscopy, X-ray diffractometry, and Energy-dispersive X-ray spectroscopy were used for the investigation of the morphology and composition of the fabricated electrodes. The electrochemical properties of Cu-CuO@C/SPE were studied by cyclic voltammetry and differential pulse voltammetry. The proposed flexible electrochemical Cu-CuO@C/SPE sensor for the simultaneous detection of hydroquinone and catechol exhibited good sensitivity, broad linear range (1–500 μM), and low limits of detection (0.39 μM for HQ and 0.056 μM for CT). [ABSTRACT FROM AUTHOR]

Here, the synthesized zinc oxide nanoparticle and characterized with XRD and SEM techniques. The carbon paste electrode was modified by using prepared nanoparticles with electrochemically polymerized by treating with 25mM Congo red and sensing environmental pollutants. The Poly (Congo red) Zinc oxide modified carbon paste [PCRZOMCPE] brings an enhanced sensitivity at electrochemical detection of catechol (CC) by using cyclic voltammetry (CV); the parameters like pH, sweep rates and concentration study was carried out, the PCRZOMCPE is applied for the simultaneous determination of CC and hydroquinone (HQ) then the detection limit and quantification value for CC is established to be 9.39µM and 31.30 µM respectively and the electrode showed excellent sensitivity and selectivity towards electrochemical examination of CC. [ABSTRACT FROM AUTHOR]

Herein, a three-dimensional flower-like cobalt-nickel bimetallic metal-organic framework (CoNi-MOF) coupled with two-dimensional graphene oxide (GO) nanocomposites was successfully synthesized for the selective and simultaneous electrochemical determination of catechol (CC) and hydroquinone (HQ). The three-dimensional flower-like structure of the CoNi-MOF/GO nanocomposite has a multilayer structure and a large surface area, which greatly improves its electrocatalytic activity towards CC and HQ. Differential pulse voltammetry (DPV) results showed that the peak-to-peak separation of CC (0.223 V) and HQ (0.120 V) was 103 mV at a CoNi-MOF/GO modified glassy carbon electrode (CoNi-MOF/GO/GCE), suggesting that the proposed modified electrode can selectively and simultaneously determine them. Under optimal conditions, the CoNi-MOF/GO/GCE showed an excellent analytical performance for the simultaneous determination of CC and HQ, including a wide linear range (0.1–100 μM), low detection limit (0.04 μM for HQ and 0.03 μM for CC) and high anti-interference ability. As expected, the developed modified electrode has been used to analyze CC and HQ in river water, with acceptable results. [ABSTRACT FROM AUTHOR]

A collaborative study among 20 participating laboratories was conducted in an effort to publish a recommended method for determination of phenols in mainstream cigarette smoke. The study was conducted using 10 test samples including reference cigarettes and commercial products from various regions (ISO 3308 total particulate matter 1–16 mg/cig) smoked under two regimes (ISO 3308 and ISO 20778). Health Canada method T-114 was chosen as a basis for the analytical methodology and therefore mainstream cigarette smoke was trapped on 44-mm glass fiber filter pads which were subsequently extracted with 1% aqueous acetic acid for analysis by high performance liquid chromatography with fluorescence detection. Statistical analysis was carried out following ISO 5725 to generate repeatability (r) and reproducibility (R) data for results from linear and rotary smoking. For reproducibility (R) expressed as a percentage of mean yield across all of the studied products and both smoking regimes, values ranged from 17–150%. The lowest “tar” yielding products had the most variable data. Results trended as expected for total particulate matter, blend type, regime, and relative analyte yields. Results supporting a robust method for hydroquinone, resorcinol, catechol, phenol, o-cresol, m-cresol, and p-cresol are reported herein and support establishment of CRM 78, ISO 23904 and ISO 23905 standardized methods. [Contrib. Tob. Nicotine Res. 32 (2023) 18–25]

Benzoquinone (BQ, 1,4-dihydroxybenzene) and catechol (CC, 1,2-dihydroxybenzene) are considered as emerging microcontaminants due to their persistent toxicity for plants and animals. Therefore, it is of great importance to monitor these contaminants in groundwater. This work proposes a novel sensor based on a multiwalled carbon nanotubes functionalised with carbonyls, and iron oxide nanoparticles (MWCNT-COOH/Fe2O3) for simultaneous determination of BQ and CC. The nanomaterials were characterised by Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Cyclic Voltammetry (CV). The electrochemical determination of BQ and CC has been studied using differential pulse voltammetry (DPV) technique on glassy carbon electrode (GCE) modified with MWCNT-COOH/Fe2O3 nanocomposite (MWCNT-COOH/Fe2O3/GCE). The developed new method under optimised experimental conditions was applied successfully for the simultaneous determination of BQ and CC in spiked underground water sample, pH 5.0 (Britton Robson – BR buffer). For DPV measurements, the following parameters were used after optimisation: Einitial = 0.0 V, Efinal = 0.40 V; scan rate = 0.01 V s−1 and pulse amplitude = 0.07 V. The linearity range of both analytes BQ and CC was 8–100 µmol L−1 with limits of detection (DLs) of 3.46 µmol L−1 and 1.52 µmol L−1, respectively. Good average results of recovery (n = 3) were obtained in spiked environmental samples for BQ (sample 1: 98.16%; sample 2: 100.55%) and CC (sample 1: 97.44%; sample 2: 97.84%), with precision (relative standard deviation) of 4.5% and 5.6%, respectively. [ABSTRACT FROM AUTHOR]

In this study, by utilizing the co-precipitation method we prepared a cadmium oxide nanoparticle and analyzed by XRD, SEM, and EDS techniques. By utilizing prepared nanoparticles carbon paste electrode was modified and pretreated with 0.1M NaOH and sensing environmental pollutants. The CdO/PMCPE brings enhanced sensitivity in an electrochemical investigation of Hydroquinone (HQ) and Catechol (CC) in the existence of Resorcinol (RS) by using cyclic voltammetry (CV) and differential pulse Voltammetric techniques (DPV); The experimental parameter such as scan rate and concentration study was carried out for the determination of CC and HQ, the CdO/PMCPE is utilized for individual and concurrent determination of CC, HQ, and RS, then the detection limit for CC, HQ, and RS found to be 0.506 μM, 0.442 μM and 0.651 µM respectively. The effect of conflict was analyzed by using the Differential Pulse Voltammetry. The electrode showed excellent stability and reproducibility, the prepared sensor can be used for the detection of CC, HQ, and RS in real sample analysis. [ABSTRACT FROM AUTHOR]

Metal oxides comprise a large group of chemicals used in water treatment to adsorb organic pollutants. The ability of titanium dioxide (TiO2) and iron (III) oxide (Fe2O3) to reduce the chronic toxicity of (phenolic) C6H6(OH)2 isomers, namely hydroquinone (HQ) and catechol (CAT) to Ceriodaphnia dubia and Pimephales promelas (less than 24 h-old) were investigated. The toxic endpoints following metal oxide treatment were compared to endpoints of untreated CAT and HQ. In chronic toxicity testing, HQ resulted in greater toxicity than CAT for both test organisms; the median lethal concentrations (LC50) for CAT were 3.66 to 12.36 mg.L−1 for C. dubia and P. promelas, respectively, while LC50 for HQ were 0.07 to 0.05 mg.L−1, respectively. Although both treated solutions presented lower toxic endpoints than those in the untreated solutions, Fe2O3 had a better potential to reduce the toxic effects of CAT and HQ than TiO2. [ABSTRACT FROM AUTHOR]

Well-dispersed reduced graphene oxide (RGO) nanostructures with uniform decoration of silver nanoparticles (AgNPs) on them have been prepared through a hydrothermal process followed by the freeze-drying method. The obtained graphene-layer-like structure with uniform distribution of AgNPs have then been applied on the glassy carbon electrodes (GCE) to detect different concentration of hydroquinone (HQ) and catechol (CC) in their mixed solutions. Because of such well-dispersed structure and uniform distribution of AgNPs, the AgNPs/RGO/GCE illustrated enhanced simultaneous detection performance for HQ and CC. In the HQ and CC mixed solution with pH of 6.0, the AgNPs/RGO/GCE electrode exhibits a wide linear range of HQ (0.18–130 μM) and CC (0.07–120 μM), and accurate limit of detection (2.37 × 10−2 μM for HQ and 5.8 × 10−2 μM for CC). Thus, it is believed that the AgNPs/RGO nanostructures shows a great potential of applying as possible probes for simultaneous detection of HQ and CC in real environment. [ABSTRACT FROM AUTHOR]

Catechol and Hydroquinone are considered to be main organic pollutants in water, and have a threat to human health and ecology security. It is imperative to establish a detection method of catechol and hydroquinone with high selectivity and sensitivity.In this work, a composite of L-Cysteine and nickel cobaltite co-functionalised graphene oxide was synthesised successfully by a facile hydrothermalmethod.The morphology and structure of the as-prepared composite was characterised by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The results revealed that the final product formed a 3D framework with urchin-like nickel cobaltite nanoparticle tightly packed on the layers of graphene oxide. The electrochemical properties of the composite modified glassy carbon electrode for detecting hydroxybenzeneisomers (hydroquinone and catechol) were tested by cyclic voltammetry and differential pulse voltammetry. The results discovered that the modified electrode exhibited an excellent repeatability and anti-interference towards the detection of catechol and hydroquinonewith linear response in the range of 10–140 μM and 10–200 μM, respectively. [ABSTRACT FROM AUTHOR]

The current effort benefited from a simple hydrothermal production protocol to fabricate a nanocomposite using graphene oxide nanosheets anchored with manganese dioxide nanorods (MnO2 NRs-GO) that was applied to construct a sensitive electrochemical catechol sensing system. As-produced nanocomposite was characterized by Field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Fourier transformed-infrared spectroscopy (FT-IR), which was then drop-casted on glassy carbon electrode (MnO2 NRs-GO/GCE) for sensor application. The MnO2 NRs-GO/GCE showed remarkable electrocatalytic capacity for the redox reaction of catechol, with minimized redox overpotentials and boosted voltammetric peak currents. As-fabricated sensor displayed an admirable electrocatalytic behavior to catechol, with a narrow limit of detection (0.02 µΜ), a broad linear range (0.5–400.0 µM) and an impressive sensitivity (0.0503 µA/µΜ). The MnO2 NRs-GO/GCE was also successful in sensing catechol in real specimens, with appreciable recovery rates. [ABSTRACT FROM AUTHOR]

Developing excellent electrochemical sensors for the determination of pollutants in the environment is crucial to advances of human detection technology. In this work, Ni/N-doped graphene oxide (Ni/N-GO) composite was constructed as an electrochemical sensor (Ni/N-GO/GCE) for the selective determination of catechol (CC) and hydroquinone (HQ). Thereinto, the Ni/N-GO composite was prepared by a high-temperature thermal reduction method. Also, a series of characterizations and electrochemical measurements were used to research the electrochemical properties of Ni/N-GO/GCE to detect CC and HQ. Furthermore, the oxidation peak potentials of CC and HQ on Ni/N-GO/GCE were 0.07 and 0.17 V, respectively, allowing selective detection of HQ and CC. Ni/N-GO/GCE exhibited linear responses toward CC and HQ in the concentration ranges of 1.4 ~ 800 and 1.0 ~ 800 μM, respectively. Besides, the detection limits were calculated as 0.06 and 0.16 μM (S/N = 3) through differential pulse voltammetry, respectively. Under optimized experimental conditions, the electrochemical sensor revealed excellent catalytic performance for the redox of CC and HQ. Finally, the results showed that Ni/N-GO/GCE was a promising electrode with superb long-term stability and reproducibility for the determination of hydroquinone isomers. [ABSTRACT FROM AUTHOR]

Herein, a novel D‐A‐D type monomer that contains hexylthiophene as the donor and benzo[c][1,2,5]thiadiazole as the acceptor has been electropolymerized successfully to yield P(DTFBT) and its electrochromic properties and performance in amperometric biosensors have been investigated. The polymer shows great electrochemical features with low band gap and multichromic properties. Additionally, after polymer modification, laccase was immobilized on a modified electrode surfaces for catechol sensing. Biosensor optimization values, cycle number, enzyme amount, pH and also interfering effect of some possible compounds were investigated. With optimum values, analytical characterization of the sensor was determined. Kmapp, LOD and sensitivity values were estimated as 0.11 mM, 0.014 mM and 166.74 μA/(mM cm2), respectively. The experimental results revealed that the sensor shows satisfactory accuracy and confirms the proposed sensor has a potential candidate for catechol quantification. [ABSTRACT FROM AUTHOR]

The adsorption behaviours of phenolic isomers, catechol (CC) and hydroquinone (HQ), on an inexpensive adsorbent, corncob, were studied. The optimum conditions required for the extractions of CC and HQ from aqueous media by the ground corncob were comprehensively studied. Further, the concentrations of CC and HQ were electrochemically determined with a palladium nanoparticles/poly(1,2-diaminoanthraquinone)/glassy carbon modified electrode (PdNPs/p1,2-DAAQ/GC/ME) by a square wave voltammetry technique in 0.05 M perchloric acid. It was confirmed that the maximum uptakes of 100 ppm CC and 100 ppm HQ were obtained at pH 8 and shaking time of 1.5 h with an adsorbent (corncob) dose of 0.1 g. The adsorptions of CC and HQ by ground corncob followed the second- and first-order models determined by the Freundlich adsorption isotherm, respectively. Corncob effectively adsorbed phenolic compounds from wastewater. [ABSTRACT FROM AUTHOR]

Carbonized polymer dots (CPDs) were developed for the quantitative detection of hydroquinone (HQ). CPDs were synthesized via a hydrothermal treatment at 150 °C for 12 h using proline (Pro) and polyethyleneimine (PEI) as precursor materials. CPDs displayed bright blue fluorescence, while HQ significantly quenched it. It was attributed to the fact that HQ was easily oxidized to 1,4-benzoquinone under alkaline conditions, and 1,4-benzoquinone might form hydrogen bonds with amino groups on the surface of CPDs. At the same time, the electrons of the excited CPDs can be transferred to 1,4-benzoquinone, which eventually leads to the fluorescence quenching of CPDs. CPDs can effectively eliminate the interference from resorcinol and catechol in the detection of HQ. The linear range for the detection of HQ was between 0.1 μM and 120 μM, with a limit of detection of 80 nM. Furthermore, CPDs were successfully applied to the determination of HQ in lake water and developer samples. It was proved that the system had a good prospect for the detection of HQ in environmental samples and broadened the application of CPDs in the field of analysis. [ABSTRACT FROM AUTHOR]

The conversion of metal-organic frameworks (MOFs) into advanced functional materials offers a promising route for producing unique nanomaterials. MOF-derived systems have the potential to overcome the drawbacks of MOFs, such as low electrical conductivity and poor structural stability, which have hindered their real-world applications in certain cases. In this study, laser scribing was used for pyrolysis of a Cu-based MOF ([Cu4{1,4-C6H4(COO)2}3(4,4′-bipy)2]n) to synthesize a Cu-CuO@C composite on the surface of a screen-printed electrode (SPE). Scanning electron microscopy, X-ray diffractometry, and Energy-dispersive X-ray spectroscopy were used for the investigation of the morphology and composition of the fabricated electrodes. The electrochemical properties of Cu-CuO@C/SPE were studied by cyclic voltammetry and differential pulse voltammetry. The proposed flexible electrochemical Cu-CuO@C/SPE sensor for the simultaneous detection of hydroquinone and catechol exhibited good sensitivity, broad linear range (1–500 μM), and low limits of detection (0.39 μM for HQ and 0.056 μM for CT).

A spectrophotometric method has been developed for the determination of some phenolic compounds (Catechol, Resorcinol and Quinol). The method is based on oxidative coupling reaction of these compounds with 4-aminoantipyrine (4-AAP) in the presence of cupper sulphate as oxidizing agent in alkaine medium forming a brown colour. The products show maximum absorption at 404 nm, 474 nm and 392 nm for Catechol, Resorcinol and Quinol respectively. The molar absorptivities are 12133, 7695 and 16570 l/mol.cm for concentrations obeyed Beer’s law in the range 0.2 - 14, 0.04 - 18 and 0.2 - 4 μg.ml-1 for the above compounds respectively. The average recovery was ranged between 97.72% and 100.05% with relative standard deviation less than 3.4 for all the studied compounds, The 4-AAP products were formed in the ratio of 1:2 phenolic compound: 4-AAP With the exception of the complex catechol:4-amino antipyrine, it is in a 1:1 ratio. The stability constant of the products was 1.8369 × 104 (l.mol-1), 2.82 × 1010 and 1.285 × 1010 (l2.mol-2) for Catechol, Resorcinol and Quinol products respectively indicating the good stability of these products, The effect of a number of interfering substances represented by primary and secondary aliphatic alcohols, aliphatic amines and other organic compounds was also studied. Finally, the results obtained indicate the selectivity of the method as there was no interference from the additives. [ABSTRACT FROM AUTHOR]

Nano-sized bimetal Cu–Fe silica catalyst (Cu–Fe–SiO2/S) had been directly prepared by supercritical one-step method from sodium silicate to catalyze phenol hydroxylation. Compared with the ordinary silica, it had the same structure and composition with smaller particle size, more fluffy morphology and larger oil absorption. Its particle size mainly was 20 nm with 192.4 m2/g specific surface area, and much higher than that of ordinary silica (90.0 m2/g). This method employing bimetal Cu–Fe–SiO2/S as catalyst for phenol hydroxylation was better catalytic activity than Fe–SiO2/S and Fe-containing precipitated silica catalyst (Fe–SiO2/P), which was benefited the favorable performance attributes such as larger specific surface area and more regular pore structure as catalyst support, and the synergistic catalysis between Cu and Fe. Under optimal reaction conditions, 46.9% of dihydroxybenzene yield, 43.3% of catechol yield, 3.6% of hydroquinone yield, and 82.3% of catechol selectivity was achieved. The possible catalytic reaction mechanism for phenol hydroxylation over Cu–Fe–SiO2/S was also suggested. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sustainable laser-assisted method for fabrication of flexible electrode based on Laser-Induced Graphene/Al NPs/PET (LIMPc) • Inexpensive and versatile method of synthesizing nanomaterials using PET as the raw material for converting waste PET. • Electrochemical detection of catechol and hydroquinone with excellent resistance to interference, repeatability, and stability of analysis. The conversion of waste polymers into functional materials presents a promising approach for PET upcycling. In this study, we exploit PET transformed into a Laser-Induced Graphene/Al NPs/PET nanocomposite (LIMPc − Laser-Induced Metal-Polymer composite) modified with electrodeposited gold nanoparticles (AuNPs). The morphology and structure of the material were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The nanocomposite was employed as a flexible electrochemical sensor for the simultaneous electrochemical detection of hydroquinone (HQ) and catechol (CT). The LIMPc-plasma-NaOH-Au composite displayed well-defined oxidation peaks for HQ and CT during electrochemical analysis, with limits of detection (LOD) as low as 47 nM for CT and 56 nM for HQ, within a linear range of 0.1–300 μM for both compounds. The long-term stability of LIMPc-plasma-NaOH-Au and its performance in real sample analysis demonstrate its potential for environmental monitoring applications. [ABSTRACT FROM AUTHOR]

Herein, a three-dimensional flower-like cobalt-nickel bimetallic metal-organic framework (CoNi-MOF) coupled with two-dimensional graphene oxide (GO) nanocomposites was successfully synthesized for the selective and simultaneous electrochemical determination of catechol (CC) and hydroquinone (HQ). The three-dimensional flower-like structure of the CoNi-MOF/GO nanocomposite has a multilayer structure and a large surface area, which greatly improves its electrocatalytic activity towards CC and HQ. Differential pulse voltammetry (DPV) results showed that the peak-to-peak separation of CC (0.223 V) and HQ (0.120 V) was 103 mV at a CoNi-MOF/GO modified glassy carbon electrode (CoNi-MOF/GO/GCE), suggesting that the proposed modified electrode can selectively and simultaneously determine them. Under optimal conditions, the CoNi-MOF/GO/GCE showed an excellent analytical performance for the simultaneous determination of CC and HQ, including a wide linear range (0.1–100 μM), low detection limit (0.04 μM for HQ and 0.03 μM for CC) and high anti-interference ability. As expected, the developed modified electrode has been used to analyze CC and HQ in river water, with acceptable results.

Different morphology of N-doped carbon materials, including three-dimensional interconnected N-doped hierarchically porous carbon networks (3D-NC), two-dimensional ultrathin porous carbon nanosheets (2D-NC), and bulk N-doped carbon with micron size (bulk-NC), was easily prepared by using NaCl crystal templates–assisted strategy. Compared with bare glassy carbon, bulk-NC, and 2D-NC, the as-synthesized 3D-NC exhibits excellent electrochemical activity toward the oxidation and sensing of three kinds of common environmental pollutants dihydroxybenzene isomers (hydroquinone (HQ), catechol (CC), and resorcinol (RS)). The impressive electrochemical activity of 3D-NC can be interpreted by its large specific surface area, continuous network-like morphology, superior electro-catalytic ability, and strong accumulation efficiency. Differential pulse voltammetry (DPV) test showed the 3D-NC-modified electrode exhibited three well-separated oxidation peaks at 0.05 V, 0.14 V, and 0.45 V vs. saturated calomel electrode (SCE) for HQ, CC, and RS, and their detection limits were evaluated to be as low as 0.0044, 0.012, and 0.016 mg L−1, respectively. Finally, a novel electrochemical analytical platform is successfully fabricated for the simultaneous monitoring of hydroquinone, catechol, and resorcinol with high sensitivity. When used for real wastewater samples analysis, recovery ratio ranging from 94 to 108% with lower than 5% of relative standard deviation (RSD) values was achieved. This work proves a facile strategy to prepare morphology-controlled N-doped carbon-based material and demonstrates its high application potential for environmental monitoring and electrochemical analysis. [ABSTRACT FROM AUTHOR]

Natural graphite has a large electrical conductivity in plane direction, hundreds times of that in vertical direction. Regulating graphite flakes perpendicular to the plane will improve the performance of the sensor. As a non-connected method, magnetic field-assisted orientation can be no-additives. However, some studies believe that diamagnetic materials are non-magnetic, and must be doped by ferromagnetic materials before oriented by a magnetic field. Here, original graphite flakes were vertically oriented by a low magnetic field during the electrode preparation to increase effective surface area. The performance of electrode was enhanced in both potassium ferricyanide/potassium ferrocyanide probe system and detection of hydroquinone (HQ) and catechol (CC). For HQ and CC detection, the sensitivities of vertically oriented graphite flakes electrode are 5.05 times and 6.35 times higher than that of graphite flakes without magnetic field, respectively. This magnetic alignment technology could construct other electrode materials for electrochemical sensors. [ABSTRACT FROM AUTHOR]

The degradation kinetics of different organic compounds in a rotating packed bed (RPB) were investigated in this work. Phenol, catechol, hydroquinone, and aniline that can react rapidly with ozone were chosen to be the model pollutants, and the lumped parameter models were established to characterize the reaction rate of fast ozonation of those organic compounds in the RPB. Correlations for the lumped parameters of the organic compounds degradation (A1) and COD removal (A2) were obtained by fitting the experimental data. The deviations between experimental and predicted A1 and A2 were generally within 25%, indicating that the ozonation rate model has a good predictability for fast ozonation between ozone and organic compounds in the RPB. [ABSTRACT FROM AUTHOR]

Branching sucrases, a subfamily of Glycoside Hydrolase family (GH70), display transglycosidase activity using sucrose as donor substrate to catalyze glucosylation reaction in the presence of suitable acceptor substrates. In this study, the (a1!3) branching sucrase GtfZ-CD2 from Apilactobacillus kunkeei DSM 12361 was demonstrated to glucosylate benzenediol compounds (i.e., catechol, resorcinol, and hydroquinone) to form monoglucoside and diglucoside products. The production and yield of catechol glucosylated products were significantly higher than that of resorcinol and hydroquinone, revealing a preference for adjacent aromatic hydroxyl groups in glucosylation. Amino residues around acceptor substrate binding subsite 11 were targeted for semirational mutagenesis, yielding GtfZ-CD2 variants with improved resorcinol and hydroquinone glucosylation. Mutant L1560Y with improved hydroquinone mono-glucosylated product synthesis allowed enzymatic conversion of hydroquinone into a-arbutin. This study thus revealed the high potential of GH70 branching sucrases for glucosylating noncarbohydrate molecules. [ABSTRACT FROM AUTHOR]

In this article, an electrochemical sensor was prepared for the simultaneous detection of hydroquinone (HQ) and catechol (CT) by incorporating porous tal palm carbon nanosheets (PTPCNS) as the modifier substance on the surface of glassy carbon electrode (GCE). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were utilized to characterize the electrochemical properties of the designed (PTCNS/GCE) sensor. PTPCNS/GCE demonstrated excellent electro‐catalytic property toward resolving the individual voltametric signal of HQ and CT from their mixture. Differential pulse voltammetry (DPV) was applied to quantify the lower limit of HQ and CT. The calculated limit of detection (LOD) was 0.15 µM for HQ with the linear range of 1–300 µM and 0.49 µM for CT with the corresponding linear range 5–225 µM obtained for the proposed sensor. The limit of quantification (LOQ) was found 0.51 µM and 1.63 µM for HQ and CT, respectively. Modified PTPCNS/GCE exhibited excellent selectivity towards HQ and CT even in presence of 10 folds potential interference. The practical applicability of the proposed sensor was analyzed in tap water sample with an excellent recovery of 98–104% for HQ and 99–102% for CT. [ABSTRACT FROM AUTHOR]

Flexible sensing is an alternative to traditional sensing and possesses good flexibility and wearability. Intrinsically conductive polymers, particularly poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS), have received significant attention due to their high mechanical flexibility and good biocompatibility. Here, we report the design of highly conductive and electrochemically active PEDOT:PSS-coated plastic substrate electrodes by combining N-doped graphene (NG) or S-doped graphene (SG) with methanesulfonic acid-treated PEDOT:PSS (denoted as NG-f-MSA-PEDOT:PSS/PET and SG-f-MSA-PEDOT:PSS/PET) by a simple drop-coating method. At room temperature, the NG-f-MSA-PEDOT:PSS/PET electrode demonstrated the lowest detection limits of 17.09, 33.84, 28.30, and 44.96 nM for paracetamol, uric acid, dopamine, and catechol (S/N = 3), respectively. The NG-f-MSA-PEDOT:PSS/PET electrode had good anti-interference ability and reproducibility without employing expensive noble metals and requiring much effort to polish the surface of traditional glass carbon electrodes. Most importantly, this film electrode could maintain a stable electrochemical response under different bending and crease states and had excellent mechanical stability and flexibility. [ABSTRACT FROM AUTHOR]

Herein, conductive polymer membrane with excellent performance was successfully fabricated by integrating carboxylated multi-walled carbon nanotubes (MWCNTs) and poly (trans-3-(3-pyridyl) acrylic acid) (PPAA) film. The drop-casting method was employed to coated MWCNTs on the glassy carbon electrode (GCE) surface, and PPAA was then electropolymerized onto the surface of the MWCNTs/GCE in order to form PPAA-MWCNTs membrane. This enables the verification of the excellent performances of proposed membrane by electrochemically determining catechol (CC) and hydroquinone (HQ) as the model. Cyclic voltammetry experiments showed that the proposed membrane exhibited an obvious electrocatalytic effect on CC and HQ, owing to the synergistic effect of PPAA and MWCNTs. Differential pulse voltammetry was adopted for simultaneous detection purposes, and an increased electrochemical responded to CC and HQ. A concentration increase was found in the range of 1.0 × 10−6 mol/L~1.0 × 10−4 mol/L, and it exhibited a good linear relationship with satisfactory detection limits of 3.17 × 10−7 mol/L for CC and 2.03 × 10−7 mol/L for HQ (S/N = 3). Additionally, this constructed membrane showed good reproducibility and stability. The final electrode was successfully applied to analyze CC and HQ in actual water samples, and it obtained robust recovery for CC with 95.2% and 98.5%, and for HQ with 97.0% and 97.3%. Overall, the constructed membrane can potentially be a good candidate for constructing electrochemical sensors in environmental analysis.

The photoreactions of a luminescent osmium(VI) nitrido complex, [OsVI(N)(L)(CN)3]− (OsN, HL = 2-(2-hydroxy-5-nitrophenyl)benzoxazole), with catechol (H2Cat) and hydroquinone (H2Q) lead to the cleavage of strong C–OH bonds (ca. 120 kcal mol−1) of the dihydroxybenzenes with concomitant conversion of the coordinated cyanide to carbon monoxide. [ABSTRACT FROM AUTHOR]

Herein, a graphene-nano-molybdenum disulphide (pGr-MoS2), synthesized from pulverized graphite and using precursors of MoS2, was investigated for the electrochemical sensing of dihydroxy benzene isomers (DHBI): hydroquinone (HQ), catechol (CA), and resorcinol (RE). Interestingly, the material could sense the three isomers simultaneously, with well-defined peaks and an adequate potential difference between each peak. The detection limits (3σ method) of HQ, CA, and RE on the glassy carbon electrode (GCE) modified with pGr-MoS2 are 10−13, 10−12, and 10−8 M (i.e., 0.1 pM, 1 pM, and 10 nM), respectively, and are the lowest reported so far for the isomers. The pGr-MoS2/GCE exhibited selectivity towards DHBI, in the presence of other toxic contaminants and metal ions such as phenol, dinitrophenol, trinitrophenol, urea and glucose, Hg(II), Ca(II), Ni(II), Zn(II), Cu(II), Na(I) and K(I). A possible mechanism for this superior selectivity of pGr-MoS2 towards DHBI is discussed based on the structural properties of pGr-MoS2 with evidence. Further, the pGr-MoS2 sensor exhibited reproducibility (with six different electrodes), stability (≥90 days), and repeatability properties. The sensing performance was successfully demonstrated in real water samples such as ground-, tap-, and river- water spiked with HQ, CA, and RE. [ABSTRACT FROM AUTHOR]

It is quite important to develop sensitive, simple, and convenient methods for the simultaneous determination of Hydroquinone (HQ) and Catechol (CC) due to their wide existence, the difficulty of degradation, and the high toxicity. Herein, Cu-TCPP nanosheets were prepared in N,N-dimethylformamide (DMF) through the solvent exfoliation method. The morphology and electrochemical performance of Cu-TCPP were characterized, revealing its stacked sheet structure with abundant pores, a fast electron transfer ability, and a large electrode active area. Using Cu-TCPP nanosheets as the sensitive material to modify the glassy carbon electrodes (Cu-TCPP/GCEs), it was found that they had an obvious enhancement effect on the electrochemical oxidation currents of HQ and CC. The signal enhancement mechanism was explored. The Cu-TCPP nanosheets not only enhanced the accumulation abilities of HQ and CC, but also improved their apparent catalytic rate, displaying high sensitivity for HQ and CC. The values of the detection limit were calculated to be 3.4 and 2.3 nM for HQ and CC. A satisfactory recovery was obtained when this method was used in measuring HQ and CC in the water samples. [ABSTRACT FROM AUTHOR]

In this study, popcorn‐derived microporous carbon (PPC) was prepared by pyrolysis method under KOH activation, which was used as an electrochemical sensor material for simultaneous detection of hydroquinone (HQ), catechol (CC), and nitrite (NT). The prepared PPC/GCE exhibited highly electrocatalytic activity to the oxidation of HQ, CC and nitrite. The oxidation peaks for HQ (111 mV), CC (216 mV), and NT (854 mV) were well separated under the optimized conditions. The PPC/GCE showed a wide linear range of 3.0–700 μM, 3.0–500 μM and 5.0–10000 μM for HQ, CC and NT with detection limits of 1.45 μM, 0.49 μM and 1.5 μM, respectively. The KOH‐activated PPC is a promising electrode material for fabricating selective and sensitive electrochemical sensors. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hydrogen bonding in polyurethane (PU) is imposed by molecular parameters. In this study, the effect of structural isomerism of certain monomers on hydrogen bonding of waterborne polyurethane (WBPU) was studied theoretically and experimentally. Two dihydroxybenzene (DHB)-based structural isomers such as catechol (CC) and hydroquinone (HQ), with different OH positions on the inner benzene core, had been used. Two series of WBPU dispersions were prepared using CC and HQ with defined contents. The binding energies between the catechol (CC)/hydroquinone (HQ) (respective OH group) and urethane/urea were calculated theoretically. By using a density functional theory (DFT) method, it was found that the largest binding energy between the urea and CC was higher than that of urea and HQ. The FT-IR analysis of synthesized polymer was also carried out to compare the results with the theoretical values. The CC-based polymers showed a stronger hydrogen bond both theoretically and experimentally than those for HQ-based polymers. The higher level of hydrogen bond was reflected in their properties of CC-based polymers. The adhesive strength, thermal stability, and hydrophobicity were higher for CC-based materials than those for HQ-based materials. The adhesive strength was increased 25% with the addition of 2.0 wt% CC content. This adhesive strength slightly deviated at a moderately high temperature of 80 °C. [ABSTRACT FROM AUTHOR]

This study introduces an innovative approach for quantifying isomeric pollutants utilizing an amperometric sensor. The determination of the isomers hydroquinone and catechol is based on the use of a glassy carbon electrode modified with Cu@PtPd/C nanoparticles (Cu@PtPd/C/GCE) in core-shell form, showing significant electrocatalytic activity in the oxidation of the later compounds. The determination was carried out at two different potentials: one at which where only hydroquinone is oxidized, and another in which where both hydroquinone and catechol are oxidized. Using these potentials, two calibration curves were built, one for the quantification of hydroquinone and the other for both isomers. Subsequently, the quantification of catechol was performed using a strategy based on the calculation of a difference using the information collected in the first step. The experiments using hydrogen peroxide as a redox probe demonstrate a clear synergistic effect in the catalytic reduction of hydrogen peroxide at −0.100 V, when Pt, Pd and Cu are incorporated into the core-shell nanostructure. The best performance was achieved with Cu@PtPd/C/GCE 1.00 mg mL−1. For the selected sensor, the analytical parameters are very competitive compared to similar devices reported in recent years for hydroquinone and catechol, with comparable linearity ranges of 0.010–0.200 mmol L−1 (hydroquinone) and 0.005–0.500 mmol L−1 (catechol), low limits of detection (LODs) of 14.0 nmol L−1 (S/N = 3.3) and 1.75 nmol L−1 (S/N = 3.3) for hydroquinone and catechol. The resulting sensor platform has been successfully applied for the quantification of hydroquinone and catechol in river and tap water and could be a promising candidate for environmental monitoring and drinking water safety. [Display omitted] • A novel strategy for the quantification of isomeric pollutants by electrochemical detection. • Amperometric sensor for the simultaneous determination of hydroquinone (HQ) and catechol (CC). • The Cu@PtPd/C in core-shell form are used as amplifiers for the electrochemical detection of HQ and CC. • Analysis of real samples for environmental monitoring was successfully performed. [ABSTRACT FROM AUTHOR]