Sensitive determination of the endocrine disruptor bisphenol A at ultrathin film based on nanostructured hybrid material SiO2/GO/AgNP

Fe–Decorated Nitrogen–Doped Carbon Nanospheres as an Electrochemical Sensing Platform for the Detection of Acetaminophen

In this work, Fe–decorated nitrogen–doped carbon nanospheres are prepared for electrochemical monitoring of acetaminophen. Via a direct pyrolysis of the melamine–formaldehyde resin spheres, the well–distributed Fe–NC spheres were obtained. The as–prepared Fe–NC possesses enhanced catalysis towards the redox of acetaminophen for abundant active sites and high–speed charge transfer. The effect of loading Fe species on the electrochemical sensing of acetaminophen is investigated in detail. The synergistic effect of nitrogen doping along with the above–mentioned properties is taken advantage of in the fabrication of electrochemical sensors for the acetaminophen determination. Based on the calibration plot, the limits of detection (LOD) were calculated to be 0.026 μM with a linear range from 0–100 μM. Additionally satisfactory repeatability, stability, and selectivity are obtained.

Electrochemical sensor based on epoxy-functionalized BEA nanozeolite and graphene oxide modified glassy carbon electrode for bisphenol E determination

An epoxy-functionalized beta type nanozeolite (BEA)/graphene oxide nanocomposite modified glassy carbon electrode (GCE/BEA/APTMS/GA/GO/NF) has been created for the differential pulse voltammetric determination of bisphenol E (BPE). The modified electrode presented an enhanced current response in comparison with bare GCE. A linear dependence of anodic peak current (Ip) and scan rate (ν) was observed, which showed that the electrochemical process was adsorption-controlled. Differential pulse voltammetry (DPV) was employed and optimized for the sensitive determination of BPE. Under the optimized conditions, the anodic peak current was linearly proportional to BPE concentration in the range between 0.07 and 4.81 µM, with a correlation coefficient of 0.995 and limit of detection 0.056 μM (S/N = 3). The electrode showed good repeatability and storage stability, and a low response to interfering compounds. Comparison was made to the determination of bisphenol A. To confirm the electrode analytical performance, recovery tests were performed, and deviations lower than 10% were found. The BEA zeolite-GO nanocomposite proved to be a promising sensing platform for bisphenol determination.

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Isotherm and thermodynamic studies on the removal of gelatin-stabilized silver nanoparticles from water by activated carbon

Gelatin-stabilized silver nanoparticles (AgNPs) with a particle size of 6.9 (±3.2) nm were synthesized and employed in nanoparticle adsorption onto activated carbon (AC). Subsequently, the synthesized AgNPs and the adsorbed nanoparticles onto the AC (AgNP@AC) were characterized by various techniques including UV–Vis spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT–IR) and X–ray diffraction (XRD). AgNPs possessed colloidal stability at a wide pH interval ranging between 4 and 13. Adsorption was studied batch-wise as a function of initial nanoparticle concentration (4–14 mg L-1), temperature (298–323 K), pH (4–13) and adsorbent dosage (0.01–0.05 g). Adsorption isotherms were investigated by fitting the data to different isotherm models including Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R). Error analysis indicated that the adsorption is well described by the Langmuir model with a monolayer adsorption capacity of 10.36 mg g-1 for 0.05 g AC at pH 7 and 323 K. Thermodynamic parameters such as enthalpy (66.77 kJ mol-1), entropy (232.92 J mol-1 K-1), and Gibbs free energy (–8.31 kJ mol-1) indicated that the process is endothermic, favorable and spontaneous through physical interactions.

A Status Update on the Development of Polymer and Metal-Based Graphene Electrochemical Sensors for Detection and Quantitation of Bisphenol A

The detection and quantitation of bisphenol A (BPA) in the environment and food products has been a subject of considerable interest. BPA, a diphenylmethane derivative is a well-known industrial raw material with wide range of applications. It is a well-known endocrine disruptor and acts as an estrogen mimic. BPA is an environmental health concern and its accumulation in hydro-geological cycles is a matter of serious ecological peril. This review basically assesses various chemically modified electrodes composed of diverse components that have been employed to recognize BPA in different matrices. Electrochemical sensors prepared using graphene materials in combination with metals and polymers for selective detection of BPA have been discussed extensively. The emphasis is on detection of BPA in various samples encountered in routine use such as plastic bottles, receipts, baby feed bottles, milk samples, mineralized water, tissue paper, DVDs, and others. Although research in this field is in the exploratory stage, deeper insights into fundamental studies of sensing systems, fast analysis of real samples and validation of sensors are some of the factors that need major impetus. It is expected that chemically modified electrode-based sensing systems will soon take over as a viable option for monitoring diverse pollutants.

Green Synthesis of ZnO/BC Nanohybrid for Fast and Sensitive Detection of Bisphenol A in Water

A nanohybrid of zinc oxide and biochar (ZnO/BC) with high conductivity was green synthesized using a simple hydrothermal method, and utilized for the sensitive detection of bisphenol A (BPA) by coating the nanohybrid film on an electrode of glassy carbon. The ZnO/BC presented greatly improved electrocatalytic performance and electron transfer ability compared to the zinc oxide and biochar. The ZnO/BC film-coated electrode could detect the BPA in aqueous solution within 3 min while neglected interference from higher concentrations of regularly existing ions and similar concentrations of estradiol (E2), phenol, dichlorophenol (DCP), and ethinylestradiol (EE2). Under optimal conditions, the linear range of BPA detection was 5 × 10−7~1 × 10−4 mol/L, with a detection limit of 1 × 10−7 mol/L, and the detection sensitivity was 92 mA/M. In addition, the ZnO/BC electrode could detect BPA in a real water sample with good signal recovery. This electrode, with the advantages of an easy preparation, low cost, and fast response time, could be potentially applicable for environmental monitoring.

Sensitive and direct electrochemical detection of bisphenol S based on 1T&2H-MoS2/CNTs-NH2 nanocomposites

A voltammetric sensor was constructed for ultra-trace BPS detection based on the signal amplification effect of 1T&2H-MoS2 and CNTs-NH2 composites.

In situ growth of ZIF-8 on gold nanoparticles/magnetic carbon nanotubes for the electrochemical detection of bisphenol A

We herein report a facile and scalable strategy for the fabrication of a metal-organic framework (MOF) based composite by in situ growing ZIF-8 on gold nanoparticle (AuNP) loaded magnetic carbon nanotubes (mCNTs). AuNPs were firstly loaded on PEI (polyethylenimine) modified mCNTs by electrostatic forces, and then AuNPs/mCNTs were encapsulated into the ZIF-8 frame through in situ self-assembling of zinc ions and 2-methylimidazole. The morphology, spectroscopy and structural properties of the AuNP/mCNT@ZIF-8 nanocomposites were systematically characterized. The conductivity-strain tests revealed that the in situ insertion of AuNPs/mCNTs in ZIF-8 could not only shorten the electron transfer distance between active sites and mCNTs, but also increase the dispersion of mCNTs, which would benefit the electron and mass transfer. Besides, by adopting the AuNP/mCNT@ZIF-8 nanocomposite-modified glassy carbon electrode (GCE) as the working electrode, a novel electrochemical sensor was successfully developed for the detection of bisphenol A (BPA). A linear range of BPA detection from 1 μM to 100 μM with a limit of detection of 690 nM was favorably obtained. Moreover, the developed sensor exhibited satisfactory reproducibility and superior stability with excellent anti-interference ability, and was successfully applied in the detection of BPA in real samples.

A Silver-Loaded Exfoliated Graphite Nanocomposite Anti-Fouling Electrochemical Sensor for Bisphenol A in Thermal Paper Samples

Silver nanoparticles (AgNPs) were synthesized separately and loaded onto the expanded layers of exfoliated graphite (EG) to form a silver nanoparticle-exfoliated graphite nanocomposite (AgNPs-EG). The AgNPs-EG was compressed into a pellet (0.6 cm in diameter) and used to prepare an electrochemical sensor for bisphenol A (BPA) in standard samples and in thermal paper. The synthesized materials were characterized by ultraviolet-visible spectrophotometry, X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive X-ray. The electrochemical behavior of BPA on the AgNPs-EG sensor was investigated by cyclic voltammetry and square wave voltammetry. Under optimized experimental conditions, the oxidation peak current was linearly proportional to bisphenol A concentrations in the range from 5.0 to100 μM, with a coefficient of determination (R2 ) of 0.9981. The obtained limit of detection of the method was 0.23 μM. The fabricated sensor was able to overcome electrode fouling with good reproducibility (RSD = 2.62%, n = 5) by mechanical polishing of the electrode on emery paper. The proposed method was successfully applied to determine bisphenol A in thermal paper samples and demonstrated good accuracy of 93.1 to 113% recovery.

Voltammetric determination of ethinylestradiol using screen-printed electrode modified with functionalized graphene, graphene quantum dots and magnetic nanoparticles coated with molecularly imprinted polymers

The present work reports the development of a sensitive and selective method for ethinylestradiol detection using screen-printed electrode (SPE) modified with functionalized graphene (FG), graphene quantum dots (GQDs) and magnetic nanoparticles coated with molecularly imprinted polymers (mag@MIP). The performance of the mag@MIP sensor was compared with that of a non-molecularly imprinted sensor (mag@NIP). Chemical and physical characterizations of the mag@NIP and mag@MIP sensors were performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) techniques. The electrochemical behavior of the electrodes investigated, which included (mag@MIP)-GQDs-FG-NF/SPE, (mag@NIP)-GQDs-FG-NF/SPE, GQDs-FG-NF/SPE and FG-NF/SPE, was evaluated by cyclic voltammetry. The results obtained show a significant increase in peak current magnitude for (mag@MIP)-GQDs-FG-NF/SPE. Using square wave voltammetry experiments, the efficiency of the (mag@MIP)-GQDs-FG-NF/SPE sensor was also tested under optimized conditions. The linear response range obtained for ethinylestradiol concentration was 10 nmol L^-1 to 2.5 μmol L^-1, with limit of detection of 2.6 nmol L^-1. The analytical signal of the (mag@MIP)-GQDs-FG-NF/SPE sensor suffered no interference from different compounds and the sensor exhibited good repeatability. The proposed sensor was successfully applied for ethynilestradiol detection in river water, serum and urine samples, where recovery rates between 96 to 105% and 97-104% were obtained for environmental and biological samples, respectively.

Flexible Carbon Electrodes for Electrochemical Detection of Bisphenol-A, Hydroquinone and Catechol in Water Samples

The detection of pollutant traces in the public water supply and aquifers is essential for the safety of the population. In this article, we demonstrate that a simple electrochemical procedure in acidic solution can be employed for enhancing the sensitivity of flexible screen-printed carbon electrodes (SPEs) to detect bisphenol-A (BPA), hydroquinone, and catechol, simultaneously. The SPEs were pretreated electrochemically in a H2SO4 solution, which did not affect their morphology, yielding high current signals with well separated oxidation peaks. The sensitivity values were 0.28, 0.230, and 0.056 µA L µmol−1 with detection limits of 0.12, 0.82, and 0.95 µmol L−1 for hydroquinone, catechol, and BPA, respectively. The sensors were reproducible and selective for detecting BPA in plastic cups, and with adequate specificity not to be affected by interferents from water samples. The simple, inexpensive, and flexible SPE may thus be used to detect emerging pollutants and monitor the water quality.

Moxifloxacin Hydrochloride Electrochemical Detection at Gold Nanoparticles Modified Screen-Printed Electrode

It appeared that either the carbon paste or the screen-printed carbon electrodes that were modified with gold nanoparticles (AuNPs) gave rise to the largest current responses after a rapid screening of various nanomaterials as modifiers of carbon composite electrodes in view of designing an electrochemical sensor for Moxifloxacin Hydrochloride (Moxi). The screen-printed electrode (SPE) support was preferred over the carbon paste one for its ability to be used as disposable single-use sensor enabling the circumvention of the problems of surface fouling encountered in the determination of Moxi. The response of AuNPs modified SPE to Moxi was investigated by cyclic voltammetry (CV) (including the effect of the potential scan rate and the pH of the medium), chronoamperometry, and differential pulse voltammetry (DPV) after morphological and physico-chemical characterization. DPV was finally applied to Moxi detection in phosphate buffer at pH 7, giving rise to an accessible concentration window ranging between 8 µM and 0.48 mM, and the detection and quantification limits were established to be 11.6 µM and 38.6 µM, correspondingly. In order to estimate the applicability of Moxi identification scheme in actual trials, it was practiced in a human baby urine sample with excellent recoveries between 99.8 % and 101.6 % and RSDs of 1.1-3.4%, without noticeable interference.

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.

A nanostructured label-free platform based on an ultrathin film for ultrasensitive detection of a secosteroid hormone

We report the electrocatalytic activity of perovskite-type LaNiO₃-nanoxide (LN-NO) on secosteroid hormone oxidation in alkaline solution.