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A wide variety of 2-amino-4 H-chromene derivatives with diverse substituents on the 4 H-chromene ring were efficiently prepared via one-pot three-component reaction of an aromatic aldehyde and malononitrile with 2-hydroxynaphthalene-1,4-dione, ethyl acetoacetate, or naphthols in the presence of triethanolamine as a new organocatalyst under solvent-free conditions. The procedure is transition metal-free and environmentally friendly approach to various 2-amino-4 H-chromene derivatives. Its advantages include short reaction time, high yields, low cost, and straightforward work-up. Triethanolamine is an efficient reusable catalyst. 2-Amino-4 H-benzo[ g]chromenes (ABgC) were applied as novel components of electro synthesis of silver nanoparticles. [ABSTRACT FROM AUTHOR]

This study introduces a novel ion-imprinted polymer for the ultrasensitive detection of mercury(II) in water. The ion-imprinted polymer was synthesized via a simple bulk polymerization process using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, morpholine-4-carbodithioic acid phenyl ester as the chelating agent, and ammonium persulfate as the initiator. The electrochemical mercury(II) sensing capability of the ion-imprinted polymer was studied via the modification of a cost-effective carbon paste electrode. A stripping voltammetric technique was utilized to quantify the analyte ions following open-circuit enrichment. Critical experimental parameters, including the nature and concentration of the eluent, solution pH, preconcentration duration, ion-imprinted polymer dosage, sample solution volume and reduction potential, were systematically studied and optimized. Under optimal conditions, the sensor exhibited a linear response in the range of 1.0 to 240.0 nM, with a low detection limit of 0.2 nM. The sensor demonstrated remarkable selectivity against potential interfering ions, including lead(II), cadmium(II), copper(II), zinc(II), manganese(II), iron(II), magnesium(II), calcium(II), sodium(I) and cobalt(II). The practical applicability of the developed method was successfully validated through the analysis of real water samples, suggesting its potential for environmental monitoring applications., (© 2024. The Author(s).)

Molybdenum-doped BiVO 4 thin films were uniformly coated on indium-doped tin oxide (ITO) substrates via a facile modified hot spin coating (HSC) technique. The prepared layers were used as photoanode in a photoelectrochemical (PEC) cell. Different percentage of Mo dopant was examined to maximize the photo-current density (J) of the layers. The highest J value (872 ± 8 μA/cm 2 ) was obtained by 5 atomic% of Mo doping. After that, the surface topographies of these samples were changed by varying the initial precursor concentration from 27 to 80 mM. The relation between surface topographies and the PEC activity of Mo-doped BiVO 4 thin films was investigated from microscopic point of view by calculating the surface roughness exponent of α, and a mechanism for the PEC activity of Mo-doped BiVO 4 photoanodes was proposed accordingly. The sample with a small roughness exponent provided a surface with jagged microscopic fluctuations which may trap the air molecules between the electrolyte and sample surface, hindering the fine atomic interaction for photo-generated electron-hole transition. Therefore, the layer with the highest roughness exponent (2α = 0.48 ± 0.03), which means the smoother microscopic surface and better interfacial contact with the electrolyte, exhibited the best PEC activity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Cancer monitoring plays a critical role in improving patient outcomes by providing early detection, personalized treatment options, and treatment response tracking. Carbon-based electrochemical biosensors have emerged in recent years as a revolutionary technology with the potential to revolutionize cancer monitoring. These sensors are useful for clinical applications because of their high sensitivity, selectivity, rapid response, and compatibility with miniaturized equipment. This review paper gives an in-depth look at the latest developments and the possibilities of carbon-based electrochemical sensors in cancer surveillance. The essential principles of carbon-based electrochemical sensors are discussed, including their structure, operating mechanisms, and critical qualities that make them suited for cancer surveillance. Furthermore, we investigate their applicability in detecting specific cancer biomarkers, evaluating therapy responses, and detecting cancer recurrence early. Additionally, a comparison of carbon-based electrochemical sensor performance measures, including sensitivity, selectivity, accuracy, and limit of detection, is presented in contrast to existing monitoring methods and upcoming technologies. Finally, we discuss prospective tactics, future initiatives, and commercialization opportunities for improving the capabilities of these sensors and integrating them into normal clinical practice. The review highlights the potential impact of carbon-based electrochemical sensors on cancer diagnosis, treatment, and patient outcomes, as well as the importance of ongoing research, collaboration, and validation studies to fully realize their potential in revolutionizing cancer monitoring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In this work, novel modified electrode (MXene/MIL-101(Cr)/GCE) are manufactured through simple layer-by-layer immobilization procedure. The fabricated electrochemical sensor was utilized for electrochemical sensing of flutamide in biological fluids. The immobilization of both MXene and metal-organic framework (MOF) materials on the electrode surface could improve the electrochemical performance of the modified glassy carbon electrode (GCE) towards flutamide due to the synergic effects. The established sensor illustrated the significant sensing ability for the determination of flutamide. The influence of solution pH and volume ratio of MXene/MIL-101(Cr) on electrochemical performance of the modified GCE was researched and optimized. The sensor demonstrated a favorable detection limit of 0.009 μM and a linear range of 0.025-100 μM using differential pulse voltammetry (DPV) technique. The suggested assay illustrated an excellent sensing efficiency towards flutamide in body fluids with recoveries ranging from 97.7% to 102.5%, which indicates its potential in real matrices. In addition, the MXene/MIL-101(Cr)/GCE was illustrated some advantages including simple preparation, good selectivity and reproducibility, and rapid flutamide detection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In this work, an environmentally friendly strategy was used to synthesize gold nanoparticles (Au NPs) using Olea europaea (olive) fruit. Transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) were used to characterize the physicochemical properties of the synthesized NPs. An Au NPs modified glassy carbon electrode was used to investigate the direct electrochemical oxidation of hydrazine. The suggested hydrazine sensor has good performance, such as a wide linear range (2.5-275 μM), low limit of detection (0.09 μM), notable selectivity and excellent reproducibility (RSD = 2.2%). The in-vitro cytotoxicity of three human cancer cell lines (KATOIII, NCI-N87, and SNU-16) was also explored with various concentrations of Au NPs prepared from olive fruit extract. Bio-synthesized Au NPs were found to have cytotoxic properties against gastric cancer in humans based on MTT assay protocol. The obtained results show that green synthesized Au NPs can be successfully employed in electrochemical sensing and cancer treatment applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Exposure to thallium (Tl), a noxious heavy metal, poses significant health risks to both humans and animals upon ingestion. Therefore, monitoring Tl levels in the environment is crucial to prevent human exposure and reduce the risk of developing severe health problems. This paper presents the development of a highly sensitive Tl ions sensor through surface modification of a glassy carbon electrode with a nanocomposite comprising MnO 2 magnetic sepiolite and multi-walled carbon nanotubes (MnO 2 @Fe 3 O 4 /Sep/MWCNT/GCE). Multiple methodologies were employed to assess the performance of the newly developed sensor. By employing square wave anodic stripping voltammetry (SWASV) to optimize the measurement conditions, notable enhancements were observed in the stripping peak currents of Tl (I) on the MnO 2 @Fe 3 O 4 /Sep/MWCNT/GCE surface. The effectiveness of the nanocomposite in facilitating electron transfer between the Tl (I) ions (guest) and the electrode (host) was demonstrated from the enhanced signals observed at the different modified electrode surfaces under optimal conditions. The developed sensor displayed a wide linear range of 0.1-1500 ppb for Tl (I) and a low detection limit of 0.03 ppb for Tl (I). It was found to be selective for Tl (I) ions while remaining unaffected by interfering non-target ions in the presence of the target ions. Despite its simple preparation procedure, the modified electrode exhibited high stability and excellent reproducibility for measuring Tl (I). The outstanding electroanalytical performances of the MnO 2 @Fe 3 O 4 /Sep/MWCNT/GCE electrode enabled its successful use as an ultrasensitive sensor for determining trace amounts of Tl in environmental samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Our investigation aimed to create and manufacture an electrochemical impedance sensor with the purpose of improving the detection efficiency of melatonin (ME). To achieve this objective, we employed gold nanoparticles coated on polydopamine formed in glassy carbon electrodes (AuNPs/PDA/GCE) as a means to enhance the sensor's capabilities. A novel approach employing the signal-off strategy and electrochemical impedance spectroscopy (EIS) technique was utilized to determine ME. When the AuNPs/PDA/GCE electrode was immersed in a buffered solution containing ME, and the oxidation current of AuNPs was recorded, it was observed that the oxidation current of AuNPs decreased upon the introduction of ME molecules. The decrease in electrical current can be ascribed to the inhibitory impact of ME molecule adsorption on the electrode surface with applying -0.2 V for 150 s in acetate buffer solution (ABS) (pH, 5) through various mechanisms, which hinders the electron transfer process crucial for AuNPs oxidation. Consequently, by utilizing EIS, various concentrations of ME were quantified spanning from 1 to 18 pM. Moreover, the ME sensor achieved an impressive detection limit of 0.32 pM, indicating its remarkable sensitivity in detecting low concentrations of ME. Importantly, these novel sensors demonstrated exceptional attributes in terms of sensitivity, specificity, stability, and repeatability. The outstanding performance of these sensors, coupled with their desirable attributes, establishes their considerable potential for a wide range of practical applications. These applications encompass various fields such as clinical diagnostics, pharmaceutical analysis, environmental monitoring, and industrial quality control, where accurate and sensitive detection of ME is of utmost importance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

An effective biosensing platform is described based on halloysite nanotube/carbon composite decorated with Pd nanoparticles (HNT/C@Pd NPs). A novel electrochemical aptasensor was designed using the proposed nano-platform to determine human epidermal growth factor receptor 2 (HER2), a breast cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity and selectivity for tumor markers owing to the high specific surface area of HNT/C and good conductivity stems from deposition of Pd NPs into HNT/C composite. With a correlation coefficient of 0.996, the electrochemical aptasensor demonstrated a wide linear range from 0.03 ng/mL to 9 ng/mL. The limit of detection (LOD) of the established assay was 8 pg/mL based on S/N = 3 method. Further, the designed biosensor demonstrated acceptable selectivity, good reproducibility, and high stability. The applicability of the impedimetric sensor in human serum samples was also examined and compared to enzyme-linked immunosorbent assay (ELISA) assay (p-value >0.05). Based on the results, it was found that the proposed methodology can be used in quantification of breast cancer markers for early diagnosis and treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Nanocomposites have gained attention due to their variety of applications in different fields. In this research, we have reported a green synthesis of a bi-metallic nanocomposite of nickel and zinc using an aqueous extract of Citrus sinensis in the presence of chitosan (Ni/Zn@orange/chitosan). The nanocomposite was characterized using different techniques. We have examined various applications for Ni/Zn@orange/chitosan. The NPs were manufactured in spherical morphology with a particle range size of 17.34-90.51 nm. Ni/Zn@orange/chitosan showed an acceptable ability to remove dyes of Congo red and methyl orange from an aqueous solution after 80 min furthermore, it uptaking the drug mefenamic acid from a solution. Ni/Zn@orange/chitosan also exhibited great photocatalytic activity in synthesizing benzimidazole using benzyl alcohol and o-phenylenediamine. Ni/Zn@orange/chitosan was found as a potent electrochemical sensor to determine glucose. In the molecular and cellular section of the current research, the cells with composite nanoparticles were studied by MTT way about the anti-breast adenocarcinoma potentials malignant cell lines. The IC 50 of composite nanoparticles were 320, 460, 328, 500, 325, 379, 350, and 396 μg/mL concering RBA, NMU, SK-BR-3, CAMA-1, MCF7, AU565, MDA-MB-468, and Hs 281.T breast adenocarcinoma cell lines, respectively. The results revealed the newly synthesized nanocomposite is a potent photocatalyst, dye pollution removal agent, and an acceptable new drug to treat breast cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Inc.)

Sensing of cadmium (Cd) and lead (Pb) in environmental samples is crucial for identifying potential health risks associated with exposure to these heavy metals as well as understanding the extent of heavy metal contamination in different environments and its impact on the ecosystem. The present study elucidates the development of a novel electrochemical sensor that can detect Cd (II) and Pb (II) ions simultaneously. This sensor is fabricated using reduced graphene oxide (rGO) and cobalt oxide nanocrystals (Co 3 O 4 nanocrystals/rGO). The characterization of Co 3 O 4 nanocrystals/rGO was done by using various analytical techniques. The incorporation of cobalt oxide nanocrystals with intense absorption properties results in an amplification of the electrochemical current generated on the surface of the sensor by heavy metals. This, when coupled with the unique properties of the GO layer, enables the identification of trace levels of Cd (II) and Pb (II) in the surrounding environment. The electrochemical testing parameters were meticulously optimized to obtain high sensitivity and selectivity. The Co 3 O 4 nanocrystals/rGO sensor exhibited exceptional performance in detecting Cd (II) and Pb (II) within a concentration range of 0.1-450 ppb. Notably, the limits of detection (LOD) for Pb (II) and Cd (II) were found to be highly impressive at 0.034 ppb and 0.062 ppb, respectively. The Co 3 O 4 nanocrystals/rGO sensor integrated with the SWASV method displayed notable resistance to interference and exhibited consistent reproducibility and stability. Therefore, the suggested sensor has the potential to serve as a technique for detecting both ions in aqueous samples using SWASV analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this work, a new dendrimer modified magnetic graphene oxide (GO) was used as a substrate for electrodeposition of Au nanoparticles. The modified magnetic electrode was employed for sensitive measuring of As(III) ion as a well-established human carcinogen. The prepared electrochemical device exhibits excellent activity towards As(III) detection using the square wave anodic stripping voltammetry (SWASV) protocol. At optimum conditions (deposition potential at -0.5 V for 100 s in 0.1 M acetate buffer with pH 5.0), a linear range from 1.0 to 125.0 μgL -1 with a low detection limit (calculated by S/N = 3) of 0.47 μg L -1 was obtained. In addition to the simplicity and sensitivity of the proposed sensor, its high selectivity against some major interfering agents, such as Cu(II) and Hg(II) makes it an appreciable sensing tool for the screening of As(III). In addition, the sensor revealed satisfactory results for detection of As(III) in different water samples, and the accuracy of obtained data were confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) setup. Accounting for the high sensitivity, remarkable selectivity and good reproducibility, the established electrochemical strategy has great potential for analysis of As(III) in environmental matrices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Pendimethalin (PND) is a herbicide that is regarded to be possibly carcinogenic to humans and toxic to the environment. Herein, we fabricated a highly sensitive DNA biosensor based on ZIF-8/Co/rGO/C 3 N 4 nanohybrid modification of a screen-printed carbon electrode (SPCE) to monitor PND in real samples. The layer-by-layer fabrication pathway was conducted to construct ZIF-8/Co/rGO/C 3 N 4 /ds-DNA/SPCE biosensor. The physicochemical characterization techniques confirmed the successful synthesis of ZIF-8/Co/rGO/C 3 N 4 hybrid nanocomposite, as well as the appropriate modification of the SPCE surface. The utilization of ZIF-8/Co/rGO/C 3 N 4 nanohybrid as a modifier was analyzed using. The electrochemical impedance spectroscopy results showed that the modified SPCE exhibited significantly lowered charge transfer resistance due to the enhancement of its electrical conductivity and facilitation of the transfer of charged particles. The proposed biosensor successfully quantified PND in a wide concentration range of 0.01-35 μM, with a limit of detection (LOD) value of 8.0 nM. The PND monitoring capability of the fabricated biosensor in real samples including rice, wheat, tap, and river water samples was verified with a recovery range of 98.2-105.6%. Moreover, to predict the interaction sites of PND herbicide with DNA, the molecular docking study was performed between the PND molecule and two sequence DNA fragments and confirmed the experimental findings. This research sets the stage for developing highly sensitive DNA biosensors that will be used to monitor and quantify toxic herbicides in real samples by fusing the advantages of nanohybrid structures with crucial knowledge from a molecular docking investigation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

p_Aminophenol, namely 4-aminophenol (4-AP), is an aromatic compound including hydroxyl and amino groups contiguous together on the benzene ring, which are suitable chemically reactive, amphoteric, and alleviating agents in nature. Amino phenols are appropriate precursors for synthesizing oxazoles and oxazines. However, since the toxicity of aniline and phenol can harm human and herbal organs, it is essential to improve a reliable technique for the determination of even a trace amount of amino phenols, as well as elimination or (bio)degradation/photodegradation of it to protect both the environment and people's health. For this purpose, various analytical methods have been suggested up till now, including spectrophotometry, liquid chromatography, spectrofluorometric and capillary electrophoresis, etc. However, some drawbacks such as the requirement of complex instruments, high costs, not being portable, slow response time, low sensitivity, etc. prevent them to be employed in a wide range and swift in-situ applications. In this regard, besides the efforts such as (bio)degradation/photodegradation or removal of 4-AP pollutants from real samples, electroanalytical techniques have become a promising alternative for monitoring them with high sensitivity. In this review, it was aimed to emphasize and summarize the recent advances, challenges, and opportunities for removal, degradation, and electrochemical sensing 4-AP in real samples. Electroanalytical monitoring of amino phenols was reviewed in detail and explored the various types of electrochemical sensors applied for detecting and monitoring in real samples. Furthermore, the various technique of removal and degradation of 4-AP in industrial and urban wastes were also deliberated. Moreover, deep criticism of multifunctional nanomaterials to be utilized as a catalyst, adsorbent/biosorbent, and electroactive material for the fabrication of electrochemical sensors was covered along with their unique properties. Future perspectives and conclusions were also criticized to pave the way for further studies in the field of application of up-and-coming nanostructures in environmental applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Bismuth molybdate has three phases α-Bi 2 MoO 6 , β-Bi 2 Mo 2 O 9 , and γ- Bi 2 Mo 3 O 12 , each of which has unique properties that distinguish them from each other. Among them, Bi 2 MoO 6 and Bi 2 Mo 3 O 12 have the most stability. In this research, γ-Bi 2 MoO 6 @Bi 2 Mo 2.66 W 0.34 O 12 core‒shell nanofibers were deposited on the stainless steel mesh as effective and low‒cost substrate. The co‒axial electrospinning as a simple method was applied to form nanofibers on the substrate. Both of the abovementioned bismuth molybdates contents include different crystal facets, controlling the Red‒Ox properties. α-Bi 2 MoO 6 possesses the vast numbers of oxygen vacancies in Mo-O bonding makes the oxidant {100} crystal facet. Likewise, γ‒Bi 2 Mo 2.66 W 0.34 O 12 contains brittle facet of {010} with high concentration of Oxygen vacancies resulted in oxidative capability of the core‒shell composite. The obtained data indicated the key role of OH radical through photocatalytic reactions and a new heterojunction having direct Z‒scheme standing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In this work, graphene oxide (GO) sheets were prepared via a facile electrochemical exfoliation of graphite in acidic medium and subsequent oxidation with potassium permanganate. The GO sheets were employed for preparation of reduced GO adorned with nanosized silver (rGO/Ag NPs) using green reduction of GO and Ag(I) via olive fruit extract as a reducing and immobilizing agent. The crystal phase, morphology, and nanostructure of the prepared catalyst were characterized by XRD, SEM, EDX, UV-Vis and Raman spectroscopy techniques. The as-prepared rGO/Ag NPs showed superior catalytic performance towards the complete reduction (up to 99%) of 4-nitrophenol (4-NPH) to 4-aminophenol (4-APH) and rhodamine B (RhB) to Leuco RhB within 180 s using NaBH 4 at ambient condition. The rate constant (k) values were found to be 0.021 and 0.022 s -1 for 4-NPH and RhB reduction, respectively. In addition, the regenerated catalyst could be reused after seven cycles without losing any apparent catalytic efficiency. Accounting for the excellent catalytic capability, chemical stability and environment-friendly synthesis protocol, the rGO/Ag NPs has great potential working as a heterogeneous catalyst in the transforming harmful organic contaminants into less harmful or harmless compounds., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Neurodegenerative diseases (NDDs) are conditions that cause neuron structure and/or function to deteriorate over time. Genetic alterations may be responsible for several NDDs. However, a multitude of physiological systems can trigger neurodegeneration. Several NDDs, such as Huntington's, Parkinson's, and Alzheimer's, are assigned to oxidative stress (OS). Low concentrations of reactive oxygen and nitrogen species are crucial for maintaining normal brain activities, as their increasing concentrations can promote neural apoptosis. OS-mediated neurodegeneration has been linked to several factors, including notable dysfunction of mitochondria, excitotoxicity, and Ca 2+ stress. However, synthetic drugs are commonly utilized to treat most NDDs, and these treatments have been known to have side effects during treatment. According to providing empirical evidence, studies have discovered many occurring natural components in plants used to treat NDDs. Polyphenols are often safer and have lesser side effects. As, epigallocatechin-3-gallate, resveratrol, curcumin, quercetin, celastrol, berberine, genistein, and luteolin have p-values less than 0.05, so they are typically considered to be statistically significant. These polyphenols could be a choice of interest as therapeutics for NDDs. This review highlighted to discusses the putative effectiveness of polyphenols against the most prevalent NDDs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing for financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The novel synthetic Sol‒EPD process of a thin film including of well decorated g‒C 3 N 4 nanotubes on plate‒like hydroxyapatite (HAp) were applied. Using Sol‒EPD designable method anisotropic growth of HAp nanocrystals on the substrate were achieved. It has provided the orientation of the different crystal facets resulted in the photogenerated O‒vacancy from phosphate groups. Based on the studied XRD pattern, EPD deposited film of HAp was oriented along c‒plane that can improve the photocatalytic activity of the designed composited film. Systematic designing was applied for decoration of g‒C 3 N 4 nanotubes on the HAp under thermal condensation of melamine coincide with calcination of HAp. This new designed HAp/g‒C 3 N 4 nanofilm was shown high photocatalytic efficiency and completely degradation of persistent pollutant of 4‒nitrophenol in the aqueous solution. According to the electrochemical impedance spectroscopy and current density studies, the higher charge separation/low charge recombination results were obtained for composited g‒C 3 N 4 /HAp nano‒film comparing with the single films of HAp and urchin like g‒C 3 N 4 . This high separation of charge pairs should be also assigned to the special designed morphology. In addition, wrapped like structure of g‒C 3 N 4 nanotubes with C‒vacancy around HAp nanoplates play key role in separation of photo‒induced charge pairs, light diffusion, and high light harvesting within hollow nanotube. It can be highlighted that the composite degraded more than 95% of 4‒nitrophenol during 90 min that after 5 runs the photocatalytic activity was not significantly changed., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Herein, simultaneous determination of Tl (1) and Pb (II) has been carried out at the surface of a modified glassy carbon electrode with polydopamine functionalized multi-walled carbon nanotubes- BiNPs nanocomposite (BiNPs/MWCNTs-PDA/GC) using square-wave anodic stripping voltammetry (SWASV) technique. The morphologies, composition and, electrochemical properties of the BiNPs/MWCNTs-PDA/GC were characterized by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDX), electrochemical impedance spectroscopy (EIS) and, SWASV. The parameters affecting the stripping current response were investigated and optimized. The large specific area of MWCNTs and good electro-conductibility of BiNPs causes the BiNPs/MWCNTs-PDA/GC electrode to exhibit an excellent electro-catalytic effect with good separation peaks for Tl and Pb oxidation compared to bare GCE under the optimal conditions. The proposed sensor showed wide leaner ranges from 0.4-100 ppb and 100-400 ppb for Tl (I) and Pb (II). Low detection limits of 0.04 ppb for Tl (I) and 0.07 ppb for Pb (II) were achieved. The efficiency of the electrode after thirty days of storage in ambient conditions without using it and also with the ability to reuse for 16 days did not decrease significantly. In addition, the modified electrode with simple preparation method showed good reproducibility, and high selectivity for measuring target ions. The method was successfully implemented for the simultaneous determination of Tl (I) and Pb (II) in tap, mineral and waste water samples with acceptable recovery (from 99.1-103.2 for Tl (I) and 98.4-100.4 for Pb (II))., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Azo dyes as widely applied food colorants are popular for their stability and affordability. On the other hand, many of these dyes can have harmful impacts on living organs, which underscores the need to control the content of this group of dyes in food. Among the various analytical approaches for detecting the azo dyes, special attention has been paid to electro-analytical techniques for reasons such as admirable sensitivity, excellent selectivity, reproducibility, miniaturization, green nature, low cost, less time to prepare and detect of specimens and the ability to modify the electrode. Satisfactory results have been obtained so far for carbon-based nanomaterials in the fabrication of electrochemical sensing systems in detecting the levels of these materials in various specimens. The purpose of this review article is to investigate carbon nanomaterial-supported techniques for electrochemical sensing systems on the analysis of azo dyes in food samples in terms of carbon nanomaterials used, like carbon nanotubes (CNT) and graphene (Gr)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Synthetic azo dyes are widely used in a variety of industries, but many of them pose a risk to human health, particularly when consumed in large quantities. As a result, their existence in products should be closely monitored. D&C red 33 and Patent Blue V are mostly used in cosmetics, especially in toothpaste and mouthwashes. A novel carbon paste electrode modified with ZIF-8/g-C 3 N 4 /Co nanocomposite and 1-methyl-3-butylimidazolium bromide as an ionic liquid was employed as a highly sensitive reproducible electrochemical sensor for the simultaneous determination of these common dyes. ZIF structure has unique properties such as high surface area, suitable conductivity, and excellent porosity. The electrochemical behavior of the suggested electrode was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). To characterize the synthesized nanocomposites, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were applied to investigate the structure of nanocomposites. Under the optimized conditions, the modified sensor offered a wide linear concentration range 0.08-10 μM (R 2  = 0.9906) and 10-900 μM (R 2  = 0.9932) with a low limit of detection of 0.034 μM. The value of diffusion coefficient (D), and the electron transfer coefficient (α) was calculated to be 310 × 10 -5 , and 0.9 respectively. This technique offered a successful performance for the determination of target analyte in the real samples with acceptable results between 96% and 107%., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Drug efficiency can be considerably boosted while adverse effects can be reduced by precisely monitoring the concentration of anti-cancer drugs. Thus, one of the most important parameters for human health is the monitoring and detection of anticancer drugs during chemotherapy treatment. Herein, a glassy carbon electrode (GCE) was modified by Pt- and Pd-incorporated ZnO nanoparticles-decorated single-wall carbon nanotubes (Pt-Pd-ZnO/SWCNTs) nanocomposites, and ds-DNA (Calf Thymus) that was a biological recognition element, and it was aimed to be utilized as an ultrasensitive and effective electroanalytical biosensor for idarubicin (IDR) monitoring. Various physicochemical characterization techniques including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS) were used to investigate the morphology and structure of the Pt-Pd-ZnO/SWCNTs nanocomposite, which was produced via straightforward chemical precipitation combined with the one-pot method. The layer-by-layer modification technique was implemented to fabricate the ds-DNA/Pt-Pd-ZnO/SWCNTs/GCE to be further utilized as a voltammetric sensor for sensitive monitoring of idarubicin in biological fluids and pharmaceutical substances. The electroanalytical method implemented to detect idarubicin was based to detect the ds-DNA's guanine base signal on the surface of the modified electrode in the absence and presence of the anticancer drug. The results explicated that the developed biosensor performed well in determining idarubicin in concentrations ranging from 1.0 nM to 65 μM, with a detection limit of 0.8 nM. The idarubicin detection ability of the modified electrode in real samples was evaluated, and the recovery data was acquired in the range of 98.0% and 104.75%. In the final step, the preferential intercalative binding mode of idarubicin drug with ds-DNA was approved by molecular docking study. This study paves the way for engineering highly sensitive DNA biosensors to be employed in the monitoring of anticancer drugs by combining the benefits of nanocomposites and valuable information of a molecular docking study., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

One of the critical challenges in the simultaneous determination of As 3+ and Cu 2+ by stripping voltammetry is the overlapping of their oxidation peaks. Therefore, the engineering of nanostructured sensors in order to uplift their electrochemical performance is a significant issue for the codetection of As 3+ and Cu 2+ . Herein, we modified a glassy carbon electrode with a new nanocomposite based on poly methyldopa along with gold nanoparticles immobilized on the surface of magnetic graphene oxide (GCE/GO/Fe 3 O 4 @PMDA/AuNPs) that can determine As 3+ and Cu 2+ with great sensitivity. Optimization of the measurement conditions by square wave stripping voltammetry (SWSV) caused the oxidation peaks of As 3+ and Cu 2+ to be distinguished significantly from each other, while the peak currents of As 3+ and Cu 2+ increased 9-12 fold, respectively, compared to the bare electrode. The proposed electrode exhibits low detection limits (S/N ≥ 3): 0.15 ppb for As 3+ and 0.11 ppb for Cu 2+ . The GCE/GO/Fe 3 O 4 @PMDA/AuNPs also has good linearity over a wide concentration range from 5 to 500 ppb for As 3+ and 0.5-750 ppb for Cu 2+ . The good recovery values were obtained for the analysis of As 3+ and Cu 2+ in pool and drinking water samples., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Potentiometric-based biosensors have the potential to advance the detection of several biological compounds and help in early diagnosis of various diseases. They belong to the portable analytical class of biosensors for monitoring biomarkers in the human body. They contain ion-sensitive membranes sensors can be used to determine potassium, sodium, and chloride ions activity while being used as a biomarker to gauge human health. The potentiometric based ion-sensitive membrane systems can be coupled with various techniques to create a sensitive tool for the fast and early detection of cancer biomarkers and other critical biological compounds. This paper discusses the application of potentiometric-based biosensors and classifies them into four major categories: photoelectrochemical potentiometric biomarkers, potentiometric biosensors amplified with molecular imprinted polymer systems, wearable potentiometric biomarkers and light-addressable potentiometric biosensors. This review demonstrated the development of several innovative biosensor-based techniques that could potentially provide reliable tools to test biomarkers. Some challenges however remain, but these can be removed by coupling techniques to maximize the testing sensitivity., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Organophosphorus insecticide fenamiphos (FEN) is utilized to control the detrimental nematode pests. In this report, a novel molecular imprinted electrochemical sensor for insecticide FEN detection was prepared. The molecular imprinted sensor was prepared based on Co 3 O 4 nanowire and core-shell Co 3 O 4 @MOF-74 nanocomposite. Firstly, hydrothermal method followed by thermal annealing was applied for the preparation of Co 3 O 4 nanowire. Then, solvothermal technique was used in no presence of metal salts to prepare core-shell Co 3 O 4 @MOF-74 nanocomposite. In addition, several solvothermal cycles were tried to optimally adjust the reaction efficiency. After the modification of the clean carbon electrode surfaces with Co 3 O 4 @MOF-74 nanocomposites, the molecular imprinted electrodes based on Co 3 O 4 @MOF-74 nanocomposites were prepared in presence of 100.0 mM pyrrole as monomer and 25.0 mM FEN as analyte molecule between +0.30 V and +1.50 V by cyclic voltammetry (CV). The prepared molecularly imprinted sensor based on Co 3 O 4 nanowire and core-shell Co 3 O 4 @MOF-74 nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), x-ray diffraction (XRD) method, x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and CV. The quantification limit (LOQ) and the detection limit (LOD) were obtained as 1.0 × 10 -11 M and 3.0 × 10 -12 M, respectively, by using the developed sensor. Hence, the developed molecularly imprinting electrochemical sensor having high selectivity, stability and reproducibility was presented in this study for insecticide FEN detection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

In this study, for the first time, stainless steel meshes coated with poly(ethylene glycol) and carbon nanotubes (PEG-CNT) by sol-gel technique were used as the adsorbent for solid-phase extraction. The coated stainless steel is loaded onto a cartridge and used to isolate and extract organophosphorus pesticides (OPPs) from water and fruit juice samples. Effective extraction parameters such as sample volume, desorption solvent, and desorption solvent volume were studied and investigated. Under optimal conditions, the linearity of the method was obtained in the range of 0.03 to 80 ng mL -1 and also the limits of detection (LODs) of the method were ranged from 0.01 to 0.03 ng mL -1 . The repeatability of the method was evaluated at three concentration levels (0.1, 1, and 50 ng mL -1 ), and the relative standard deviation (RSD%) of the method was obtained in the range of 3.8 to 4.8%. Finally, the proposed method was used to analysis of OPPs in real water and fruit juice samples, with relative recovery in the range of 94.3 to 99.8%., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Here, an ultrasensitive non-enzymatic glucose sensor was fabricated using a facile and low price electro-deposition method. At first, thiol-functionalized magnetic nanoparticles cast onto the glassy carbon electrode (GCE) surface to provide a stable substrate with the high surface area. Then, CuO nanoparticles and Ag nanoparticles electrodeposit on the surface of Fe 3 O 4 -SH/GCE to obtain the final modified GCE. The characterization of electro-synthesized nanoparticles and the modified GCE was done by different related techniques such as field emission scanning electronic microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed electrode was applied to the electrochemical sensing of glucose. By employing the optimum conditions on the preparation of modified electrode such as time and potential for electrosynthesis of two different nanoparticles, high reproducibility of measurement and sensor preparation were achieved. The thus optimized simple glucose sensor could be provided stable responses in a wide linear range from 0.06 to 1000 μM with detection limit 15 nM, indicating its potential application for real biological samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The stainless steel mesh, in the form of the disk, was coated with graphene oxide and poly(dimethylsiloxane) (GO-PDMS) by sol-gel technique. The coated stainless steel meshes are loaded in the mini-column as solid-phase extraction cartridge for the fast isolation and preconcentration of polycyclic aromatic hydrocarbons (PAHs) from real water samples. The extracted PAHs (naphthalene, acenaphthene, acenaphthylene, anthracene, benz[a]anthracene, fluorene, and pyrene) were quantified by gas chromatography-mass spectrometry. The operation parameters affecting the extraction efficiency including sample volume, desorption conditions, and ionic strength were investigated. At optimized conditions, the linearity of this method is obtained from 0.001 to 20 ng mL -1 with 0.2 to 1.0 pg mL -1 limit of detection. For 5 replicates at 3 spiking levels (0.1, 1, and 10 ng mL -1 ), the relative standard deviations between 4.0 and 6.3% were achieved. The absolute extraction recovery varied from 89.1 to 94.7%. The enrichment factors were in the range of 2227-2367. The method has been employed in the determination of PAHs in the real water samples including well water, tap water, river water, and wastewater. Relative recoveries are between 95.2 and 100.9%. Graphical abstractSchematic representation of the SPE procedure using the self-assembly SPE cartridge.

In this study, a novel nanocomposite of graphene oxide/zinc based metal-organic framework (GO/MOF) was prepared through a simple solvothermal method. The electrochemical As(III) sensing capability of the nanocomposite was explored by casting the GO/MOF on a glassy carbon electrode (GCE), followed by an electrochemically reduction of GO. As(III) detection was performed by the differential pulse anodic stripping voltammetry (DPASV) method after closed-circuit mode. The present sensor showed excellent electrochemical performance such as a wide linear range from 0.2 to 25 ppb (μg/L), low detection limit (S/N = 3) of 0.06 ppb and good reproducibility with a relative standard deviation (RSD) value of 2.1%. The detection limit of As(III) is lower than the threshold value set by the Environmental Protection Agency (EPA) in drinking water. A good selectivity for As(III) detection by the proposed Gr/MOF-GCE was also demonstrated. Finally, this platform was employed for the As(III) monitoring in environmental water samples, and the accuracy of obtained results were confirmed by inductively coupled plasma-optical emission spectrometer (ICP-OES) system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Interest in functionalized carbon nanotubes for many applications arises from a variety on the kind of modification atoms or molecules that are attached to it. Dopamine, the feel-good hormone, release by neurons and playing an important role in body systems. Abnormal dopamine levels cause nerve disorders such as Parkinson's disease and schizophrenia., Objectives: The aim of this study was the design and fabrication of electrochemical sensor based on MWCNTs and Pd nanoparticles for detection and determination of dopamine in biological samples., Methods: For this purpose, we report the synthesis of pramipexole-functionalized MWCNTs (pp-MWCNTs) for efficient capture of palladium nanoparticles and fabrication of Pd/pp-MWCNTs nanocomposite. Morphological and structural characteristics of the nanocomposites were characterized using various techniques including field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT-IR)., Results: This newly synthesized nanocomposite may have numerous applications in nanotechnology and sensing. We show that the synthesized nanocomposite reported here will be applicable for modifications of bare glassy carbon electrode (Pd/pp-MWCNTs/GCE) to sense of dopamine electrochemically. Two linear calibrations for dopamine are obtained over ranges of 0.01 to 10 μM and 10 to 200 μM with a detection limit of 1.4 nM. The Pd/pp-MWCNTs/GCE shows high stability and sensitivity, and an acceptable decrease of over-potential for the electrooxidation of dopamine that decreases interference in the analysis. The proposed Pd/pp-MWCNTs nanocomposite can be used as a voltammetric detector for dopamine monitoring in routine real sample analysis., Conclusions: The proposed sensor showed high sensitivity and selectivity in sensing dopamine in biological samples. Graphical abstract Preparation of Pd/pp-MWCNTs/GCE for detection of dopamine.

A magnetic sorbent was fabricated by coating the magnetized graphene oxide with polystyrene (PS) to obtain a sorbent of the type GO-Fe 3 O 4 @PS. The chemical composition and morphology of the sorbent were characterized. The sorbent was employed for the enrichment of polycyclic aromatic hydrocarbons (PAHs) from water samples. Various parameters affecting the enrichment were investigated. The PAHs were then quantified by gas chromatography with flame ionization detection. Linear responses were found in the range of 0.03-100 ng mL -1 for naphthalene and 2-methylnaphthalene, and of 0.01-100 ng mL -1 for fluorene and anthracene. The detection limits (at an S/N ratio of 3) range between 3 and 10 pg mL -1 . The relative standard deviations (RSDs) for five replicates at three concentration levels (0.05, 5 and 50 ng mL -1 ) of analytes ranged from 4.9 to 7.4%. The method was applied to the analysis of spiked real water samples. Relative recoveries are between 95.8 and 99.5%, and RSD% are <8.4%. Graphical abstract A magnetic sorbent was fabricated by polystyrene coated on the magnetic graphene oxide for the extraction and preconcentration of PAHs in water samples prior to their determination by gas chromatography with flame ionization detection.

The present study describes an electrochemical aptamer-based method for the determination of bisphenol A (BPA). It is making use of gold nanoparticles (AuNPs) immobilized on a conjugate between multiwalled carbon nanotubes and thiol-functionalized magnetic nanoparticles (MWCNT/Fe 3 O 4 -SH) that are modified with an aptamer. The nanocomposite was characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, elemental mapping analysis and energy dispersive X-ray diffraction. The aptasensor, typically operated at 0.20 V (vs. Ag/AgCl), has a linear response in the 0.1 to 8 nM BPA concentration range, a low detection limit (0.03 nM), and high sensitivity (86.43 μA nM -1  cm -2 ). Voltammetric experiments were performed by using the hexacyanoferrate redox system as an electrochemical probe. The results indicate that the presence of AuNPs, magnetic nanoparticles and MWCNTs results a synergistic electrochemical augmentation. The method is highly selective, sensitive, efficient and environmentally friendly. The method was successfully applied to the determination of BPA in spiked real samples. Graphical abstract Aptasensor fabricated by MWCNT/Fe 3 O 4 -SH@Au nanocomposite and anti-BPA aptamer. The conformation of aptamer change after BPA binding, triggering a decrease in the electron transfer of Fe(CN) 6 3- / 4- on the electrode surface. The observed decline was detectable as a function of BPA concentration.

The authors describe the preparation of Fe 3 O 4 nanoparticles coated with poly(p-phenylenediamine-co-thiophene). The resulting nanoparticles (NPs) are shown to be viable sorbents for use in magnetic solid-phase extraction (MSPE) of organophosphorus pesticides (OPPs). The coated NPs were characterized by BET, FTIR, scanning electron microscopy and transmission electron microscopy. Following sorption of OPPs and subsequent desorption with dichloromethane, the OPPs were quantified by GC in combination with FID. Under optimal conditions, the preconcentration factors range from 118 to 163. Other figures of merit include (a) a linear response between 0.3 and 500 ng mL -1 ; (b) detection limits (at an S/N ratio of 3) between 0.1 and 0.3 ng mL -1 , and (c) a precision (for n = 5) between 4.7 and 8.1% at concentration levels of 1, 10 and 100 ng mL -1 ). The nanocomposites can be reused up to 8 times. The method was applied to the analysis of spiked environmental water samples and fruit juices and gave relative recoveries in the range of 88.1 to 99.2%. Graphical abstract Schematic presentation of the synthesis of core-shell magnetic nanoparticles (MNPs) of the type poly(pPDA-co-Th)@Fe 3 O 4 , and their application as a sorbent for magnetic solid-phase extraction (MSPE) of organophosphorus pesticides.

Graphene oxide (GO) was conjugated to magnetite nanoparticles and then coated with poly(methyl methacrylate) to obtain a nanomaterial of the type PMMA@GO-Fe 3 O 4 , which is shown to be a viable sorbent for magnetic solid-phase extraction. The nanocomposite was characterized by SEM, TEM, XRD, VSM and FTIR spectroscopy. It was applied to the extraction of the aromatic amines aniline, N,N-dimethylaniline, o-toluidine, and 3-chloroaniline. Under optimal conditions, the preconcentration factors range from 139 to 173. Following desorption with dichloromethane, the amines were quantified by GC. Analytical figures of merit include (a) a linear range extending from 0.007-100 ng mL -1 , (b) detection limits between 2 and 6 pg mL -1 ; and (c) relative standard deviations between 5.9 and 8.6% (for n = 5; at 0.05, 5.0 and 50 ng mL -1 levels, respectively). The method was successfully applied to the determination of aromatic amines in spiked real water samples and gave recoveries in the range of 90.3%-99.0%. Graphical abstract A magnetic sorbent was fabricated by deposition of poly(methyl methacrylate) onto Fe 3 O 4 -magnetized graphene oxide. It was applied to the extraction and preconcentration of aromatic amines from water samples prior to their gas chromatography-flame ionization detector (GC-FID) determination.

The application of magnetized graphene (G) layers synthesized on the carbon nanofibers (CNFs) (m-G/CNF) was investigated as novel adsorbent for the magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). Six important parameters, affecting the extraction efficiency of PAHs, including: amount of adsorbent, adsorption and desorption times, type and volume of the eluent solvent and salt content of the sample were evaluated. The optimum extraction conditions were obtained as: 5min for extraction time, 20mg for sorbent amount, dichloromethane as desorption solvent, 1mL for desorption solvent volume, 5min for desorption time and 15% (w/v) for NaCl concentration. Good performance data were obtained at the optimized conditions. The calibration curves were linear over the concentration ranges from 0.012 to 100ngmL(-1) with correlation coefficients (r) between 0.9950 and 0.9967 for all the analytes. The limits of detection (LODs, S/N=3) of the proposed method for the studied PAHs were 0.004-0.03ngmL(-1). The relative standard deviations (RSDs) for five replicates at two concentration levels (0.1 and 50ngmL(-1)) of PAHs were ranged from 3.4 to 5.7%. Appropriate relative recovery values, in the range of 95.5-99.9%, were also obtained for the real water sample analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Silver (Ag) nanoparticles were electrochemically deposited on the film of a metformin functionalized multi-walled carbon nanotube modified glassy carbon electrode (Met-MWCNT/GCE), which fabricated an Ag@Met-MWCNT nanocomposite sensor (Ag@Met-MWCNT/GCE) to detect entacapone (ENT). The Ag@Met-MWCNT nanocomposite was characterized by field emission scanning electrochemical microscopy (FESEM), X-ray diffraction (XRD) analysis, FT-IR and electrochemical tests. The modified electrode showed a large electrocatalytic activity for reduction of ENT. This improved activity indicates that Met@MWCNT plays a crucial role in the dispersion and stabilization of Ag nanoparticles on GCE. Under the optimized conditions the linear range for the detection of the ENT was obtained to be 0.05 to 70.0μM with a low detection limit of 15.3nM. The proposed sensor can effectively analyse ENT concentration in pharmaceutical formulations and human urine samples, avoiding interference, and is a promising ENT sensor due to good sensitivity, stability and low cost., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this work, a sensitive amperometric biosensor for hydrogen peroxide based on synergetic catalysis of hemoglobin and porous Pd@Fe3O4-MWCNT nanocomposite has been constructed. With attention to the utilities of large surface area and outstanding catalytic performance, Pd@Fe3O4-MWCNT nanocomposite was employed as the nano-stabilizer for the immobilization of hemoglobin (Hb). The immobilized Hb on the surface of nanocomposite as an electrochemical biosensor efficiently catalyzed the reduction of hydrogen peroxide, amplified the electrochemical signal and enhanced the sensitivity. Results of voltammetry and electrochemical impedance examinations showed that the nanocomposite could enhance the electron conductivity and provide more sites for the immobilization of Hb. A linear response from 0.2-500 µM with detection limit of 0.063 µM for hydrogen peroxide was achieved. The apparent Michaelis-Menten constant Kapp(M) value was 21 µM. Thus, the nanocomposite could be applied for fabrication of a third generation biosensor for hydrogen peroxide with high sensitivity, selectivity and low detection limit. The excellent performance of the biosensor indicated its promising prospect as a valuable tool in simple and fast hydrogen peroxide detection in environmental and clinical applications., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In the present work, a simple and effective method based on magnetic separation has been developed for the extraction of monocyclic aromatic amines in water and urine samples using poly(para-phenylenediamine) modified with Fe3O4 nanoparticles (PpPD/Fe3O4) as an adsorbent. The chemical structures of the sorbent were characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrophotometer (FT-IR). Various parameters affecting on the extraction efficiency of desired analytes, such as pH of solution, desorption conditions, extraction time, salt effect and amount of adsorbent have been investigated and optimized. The obtained optimal conditions were: sample pH, 6; amount of sorbent, 20mg; sorption time, 2min; elution solvent and its volume, dichloromethane and chloroform (3:1 v/v), 250μL; elution time, 30s and without addition of NaCl. Under the optimum conditions, detection limits in the range of 0.007-0.01ngmL(-1) were obtained by gas chromatography-flame ionization detector (GC-FID). The calibration curves were linear in the range 0.05-100ngmL(-1) with a correlation coefficient better than 0.9953. In addition, a satisfactory reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 5.9 and 7.3%, respectively. The proposed procedure has been successfully applied to the determination of target analytes in water and urine samples. The results demonstrated that the developed method is simple, inexpensive, accurate and remarkably free from interference effects., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A simple and sensitive sensor was proposed for the rapid determination of tiopronin (TP) using a carbon paste electrode (CPE) modified with synthesized nanocrystalline Ni50-Fe50 alloys (nano-Ni50-Fe50) and ferrocene carboxylic acid (FcCa). The synthesized nano-Ni50-Fe50 was characterized by different methods such as TEM, SEM and XRD. The electrochemical oxidation of TP on the nano-Ni50-Fe50/FcCa carbon paste electrode (nano-Ni50-Fe50/FcCa/CPE) was studied. The nano-Ni50-Fe50/FcCa/CPE exhibited good electrocatalytic properties towards oxidation of TP in phosphate buffer solution (pH7.0) with an overpotential of about 500 mV lower than that of the bare electrode. The rate constant for the catalytic oxidation of TP was evaluated by rotating disk voltammetry and the value of kc was found to be 3.2 × 10(7) cm(3)mol(-1)s(-1). Using differential pulse voltammetry (DPV), the determination of TP was explored at the modified electrode. The results indicated that the differential pulse response of TP was linear with its concentration in the range of 0.01-50.0 μM. The detection limit was 7.46 nM (S/N=3). The proposed sensor was successfully applied for the determination of TP in tablet and urine samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The new nanocomposite films based on poly(styrene-alternative-maleic anhydride) grafted to 3-aminobenzoic acid (PSMA-g-3ABA) and multi-walled carbon nanotubes (MWCNTs) were applied to immobilize hemoglobin (Hb) for biosensor fabrication (PSMA-g-3ABA/MWCNTs). Electrochemical impedance spectroscopy was used to confirm the adsorption of Hb onto the surface of PSMA-g-3ABA/MWCNTs. The immobilized Hb maintains its bioactivities and displays an excellent electrochemical behavior. The biosensor was used to catalyze the reduction of hydrogen peroxide. The electrocatalytic response showed a linear dependence on the H2O2 concentration ranging widely from 1.0×10(-6)M to 5.0×10(-4)M with a detection limit of 3.2×10(-7)M. The apparent Michaelis-Menten constant of Hb on the modified electrode was estimated to be 0.22mM. The proposed method opens a way to develop biosensors by using nanostructured materials with low electrical conductivity., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The novel biocompatible poly(p-phenylenediamine) (PpPDA)-Fe3O4 nanocomposite (PpPDA@Fe3O4) was synthesized via emulsion polymerization. The PpPDA@Fe3O4 nanocomposite was characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). The PpPDA@Fe3O4 nanocomposite was then used as substrate for the immobilization of hemoglobin (Hb) and their bioelectrochemical behaviors were studied. Electrochemical impedance spectroscopy was used to confirm the adsorption of Hb onto the surface of PpPDA@Fe3O4 nanocomposite. The Hb immobilized on PpPDA@Fe3O4 nanocomposite retained its near-native conformations as characterized by the FT-IR. A pair of well-defined redox peaks of Hb was obtained at the Hb-PpPDA@Fe3O4 modified glassy carbon electrode (Hb-PpPDA@Fe3O4/GCE) through direct electron transfer between the protein and the underlying electrode. The proposed biosensor showed good reproducibility and high sensitivity to H2O2 with the detection limit of 0.21 µM (S/N=3). In the range of 0.5-400.0 µM, the catalytic reduction current of H2O2 was proportional to its concentration. The apparent Michaelis-Menten constant of Hb on the PpPDA@Fe3O4 nanocomposite was estimated to be 0.088 mM, showing its high affinity., (Copyright © 2014 Elsevier B.V. All rights reserved.)

For the first time, the catalytic activity of phenobarbital (PB) in presence of acetaminophen (AC) was studied at the surface of modified electrode which prepared by incorporation of multi-walled carbon nanotube (MWCNT) and Pt-nanoparticles into a paste matrix. Preparation of this electrode was very simple and modified electrode showed an excellent character for electrocatalytic oxidization of acetaminophen and phenobarbital. Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of AC and PB has been explored at the modified electrode. Differential pulse voltammetry peak currents of AC and PB increased linearly with their concentrations at the ranges of 0.5-100 μM and 0.4-60 μM, respectively. Also, the detection limits for AC and PB were 0.17 μM and 0.1 μM, respectively. The method has been found selective and successfully implemented for the determination of AC and PB in human urine and pharmaceutical samples using standard addition method. The electrode exhibited an efficient catalytic response with good reproducibility and stability., (Copyright © 2012 Elsevier B.V. All rights reserved.)