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Based on the modulated electronic properties of Fe3O4-graphene (Fe3O4/GN composite) as well as the outstanding complexation between Pb2+ and natural substances garlic extract (GE), a novel electrochemical sensor for the determination of Pb2+ in wastewater was prepared by immobilization of Fe3O4/GN composite integrated with GE onto the surface of glassy carbon electrode (GCE). Fe3O4/GN composite was employed as an electrochemical active probe for enhancing electrical response by facilitating charge transfer while GE was used to improve the selectivity and sensitivity of the proposed sensor to Pb2+ assay. The electrochemical sensing performance toward Pb2+ was appraised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV). Under the optimized condition, the sensor exhibited two dynamic linear ranges (LDR) including 0.001 to 0.5 nM and 0.5 to 1000 nM with excellent low detection limit (LOD) of 0.0123 pM (S/N = 3) and quantification limit (LOQ) of 0.41 pM (S/N = 10). Meanwhile, it displayed remarkable stability, reproducibility (RSD of 3.61%, n = 3), and selectivity toward the assay for the 100-fold higher concentration of other heavy metal ions. Furthermore, the novel sensor has been successfully employed to detect Pb2+ from real water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A lead-chelating ligand, 2,2′-((1E)-((4-((2-mercaptoethyl)thio)-1,2phenylene)bis(azany-lylidene))bis(methanylylide-ne))diphenol (ETBD), was immobilized on a nanocomposite FeO@Au/MoS/GN possessing a large surface area to produce a biomimetic sensor. The ETBD molecules act as specific receptor binding sites for Pb, resulting in the highly selective Pb response by square wave voltammetry (SWV). In order to obtain highly sensitive analysis, MoS/GN was utilized as a substrate material, which enhances sensing performance and provides sites for FeO@Au, and the core-shell FeO@Au can interconnect and produce conductivity between the recognition element and nanomaterials. Due to the integration of the properties of FeO@Au, MoS/GN and ETBD, the proposed biomimetic electrochemical sensor exhibits a wide linear response range from 4 × 10 to 2 × 10 mol/L with a low detection limit of 3.38 × 10 mol/L, which shows great promise for the determination of ultra-trace Pb in real samples. [ABSTRACT FROM AUTHOR]

A novel, sensitive, and selective electrochemical sensor based on oxime-functionalized gold nanoparticles (AuNPs) and nitrogen-doped graphene (NG) composites (NG/AuNPs) was developed for the direct electrochemical detection of dimethoate, a non-electroactive organophosphorus pesticide (OP). 2-(4-Mercaptobutoxy)-1-naphthaldehyde oxime (MNO), a new organic molecule containing -SH and oxime synthesized by our group, was decorated onto electrodes through the S-Au bond between -SH of MNO and AuNPs. NG/AuNPs were modified on the electrode to provide acting sites for MNO and to amplify current response. The results indicated that the reduction current of MNO was increased, and the selectivity, sensitivity, and stability of the sensor were improved. Dimethoate was detected by using MNO as an electroactive probe through the nucleophilic substitution between oxime and dimethoate. Under optimal conditions, the sensor displayed a linear range from 1 × 10 to 4 × 10 M with a low detection limit of 8.7 × 10 M ( S/ N = 3). Results indicated that the sensor was successfully applied to detect dimethoate in water, tomato, and orange samples. Interference study analyses were investigated using the prepared electrode, which exhibited an acceptable result. [ABSTRACT FROM AUTHOR]

A new type of graphene-CoO functionalized porphyrin was synthesized and used for selective and sensitive detection of methyl parathion (MP). CoO nanoparticles were firstly modified onto graphene oxide sheets and the porphyrin/CoO/graphene nanocomposites were then synthesized by self-assembly decoration of anion porphyrin on CoO-modified graphene sheets by π-π stacking. By dexterously controlling the electrochemical reduction variables and optimizing the electrode preparation parameters, with the satisfactory conductivity, strong adsorption toward MP, the developed novel sensor fabricated with the as-synthesized nano-assembly for determination of MP shows some satisfactory properties such as a wide linear concentration range (from 4.0 × 10 M to 2.0 × 10 M), low detection limit (1.1 × 10 M), favorable repeatability, long-time storage stability, and satisfactory anti-interference ability. It also had high precision for the real sample analysis, which indicated the good perspective for field application. [ABSTRACT FROM AUTHOR]

Glassy carbon electrodes (GCEs) modified with l-cysteine ( l-cys)/gold nanoparticles (AuNPs)/nitrogen-doped graphene (NG) composite were prepared to fabricate a novel electrochemical sensor for lead. AuNPs were uniformly dispersed into NG and l-cys was successfully decorated on AuNPs through the S-Au bond. The l-cys/AuNPs/NG exhibited a well-distributed nanostructure and high responsivity toward Pb(II). The results indicated that l-cys/AuNPs/NG/GCE exhibited the highest peak current, reflecting that the l-cys/AuNPs/NG composites showed the best response signal toward Pb. Under optimized conditions, a linear relationship between the current intensity and Pb concentration was obtained in a range of 0.5-80 μg L with a detection limit of 0.056 μg L (S/N = 3). The analytical interference procedure and practical application were investigated using the prepared electrode, which exhibited an acceptable result. [ABSTRACT FROM AUTHOR]