With tunable bandwidth of negative permittivity, graphene-silicon carbide (GR-SiC) ceramics were sintered by spark plasma sintering process. Compositions and structure were investigated by field emission scanning electron microscopy and Raman spectroscopy. With its content increasing, GR interconnected into "GR clusters" with larger lateral dimensions, which tended to be connected into conductive pathways instead of agglomeration under the action of ball milling. Permittivity, alternating current conductivity (σac), dielectric loss and imaginary reactance were analyzed in detail. When the GR content exceeded 6.30 wt%, a significant electrical percolation phenomenon occurred, and the conductive mechanism changed from electronic jump conduction to a metal-like conduction. Fano-like resonance, appertained to permittivity, exhilaratingly transformed into the Lorentz model. Owing to the mutual dielectric screening between SiC and GR, the bandwidth of negative permittivity became wider and can be tuned via the GR content.

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A fast method based on Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) modified QuEChERS integrated to dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry was established for the determination of 8 organochlorine pesticides (OCPs) in green leafy vegetables. The factors involved in the purification by QuEChERS and concentration by DLLME were optimized. In the QuEChERS process, Fe3O4 MNPs were used as a new impurity adsorbent after the sample extraction procedure by acetonitrile, which achieved phase separation rapidly. Carbon black was used as an alternative to costly graphitized carbon black without affecting the recovery. In the process of DLLME, 1 mL of the extract obtained by QuEChERS was used as the dispersive solvent, 40 μL of chloroform was used as the extractive solvent, and 4 mL of water was added. Making them mix well, then the dispersed liquid-liquid microextraction concentration was subsequently carried out. The enrichment factors of 8 OCPs ranged from 22.8 to 36.6. The recoveries of the proposed method ranged from 78.6% to 107.7%, and the relative standard deviations were not more than 7.5%. The limits of detection and limits of quantification were 0.15–0.32 μg/kg and 0.45–0.96 μg/kg, respectively. The method has been successfully applied to the determination of OCPs in green leafy vegetable samples.

Ethylenediaminetetraacetic acid (EDTA) groups are successfully linked to magnetic graphene oxide (MGO) by a silanization reaction between N‐(trimethoxysilylpropyl) ethylenediaminetriacetic acid and OH on the surface of MGO. The EDTA‐modification enhances the adsorption capacity of MGO because of the chelating ability of EDTA. The adsorption behavior of Pb(II) and the effects of solution conditions such as contact time, initial Pb(II) concentration, and pH (1–9) are investigated. The adsorption capacity for Pb(II) removal is found to be 211.3 mg g−1 and the adsorption process is completed at pH 6.8 within 50 min. The process is shown to follow a pseudo‐second‐order kinetic rate. The isothermal data reveal that the adsorption process of Pb(II) is well‐matched with the Freundlich model. In addition, the magnetic composite can be effectively and simply separated by an external magnetic field. Therefore, MGO‐EDTA can potentially serve as an adsorbent for the separation and removal of Pb(II) from water.