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Three-dimensional (3D) molecularly imprinted polymer (MIP) arrays were used for electrochemical sensor to detect sulfadimidine (SM2) residue in food. NiCo2O4 nanoneedle arrays were decorated on the free-standing and highly conductive 3D graphene by a hydrothermal process. Polypyrrole (PPy) was coated onto NiCo2O4 nanoneedle arrays via electropolymerization in the presence of template molecule SM2 to obtain MIP/NiCo2O4 nanoneedle/3D graphene electrode. The desirable detectability of the composite electrode can be ascribed to the unique structure and the synergistic effects of the components: Nanoneedle arrays on 3D graphene offered the matrix to MIP and each nanoneedle as sensing unit was accessible to analyte, resulting in high specific surface area, desirable conductivity, short ion diffusion path and excellent adsorption capacity, which could powerfully boost the electrochemical property for the detection of SM2. Under optimized conditions, a wide linear range over SM2 of 0.2-1000 ng/mL with a detection limit of 0.169 ng/mL (S/N = 3) was obtained. The developed sensor also had favorable recovery of 92.3-102.23% and the relative standard deviation of 2.27-4.10%. The MIP array sensor provided an efficient tool for the selective and rapid detection of SM2 in food. [ABSTRACT FROM AUTHOR]

PPy/PANI double-layer nanotubes anchored reduced graphene oxide (rGO) nanosheets with three-dimensional architecture (3DGP) have been obtained for supercapacitors applications. The freestanding electrode yields specific capacitance (542 F g at current density of 1 A/g) and excellent cycle stability (92.1% capacitance retention after 2000 cycles in a three-electrode cell configuration). The further assembled symmetric supercapacitor device exhibits a high energy density of 20.8 W h kg at a power density of 250 W kg and good cycle stability (capacitance loss of 7% up to 2000 cycles). The exceptional electrochemical performance of 3DGP can be ascribed to the unique structure and the synergistic effects of the components: (1) Integrating the highly capacitance matrix PPy/PANI coaxial nanotubes hybrid in rGO to enhance the reversible faradic reactions can boost the utilization rate of the electrode materials and circumventing the predicament of pseudo materials. (2) The desirable π- π interactions between highly conductive rGO films and polymer chains construct a high-performance network, which facilitates rapid transport of the electrolyte ions in the electrode. (3) The as-prepared electrode materials fabricated into electrodes directly decrease the 'dead weight,' for the addition of binder and conductive agents can be avoided. [ABSTRACT FROM AUTHOR]

In this work, we reported the highly ordered NiCoO nanoneedle@polypyrrole arrays anchored on three-dimensional graphene (NiCoO@PPy/3D graphene) for high-sensitivity detection of trace lead ions (Pb). The 3D graphene was prepared by a hydrothermal process and then decorated with NiCoO nanoneedle arrays by another hydrothermal process. This two-step hydrothermal method is simple and mild. Furthermore, the highly conductive PPy was coated on NiCoO via a chemical vapor-phase polymerization to prepare NiCoO@PPy/3D graphene. The free-standing NiCoO@PPy/3D graphene can be directly utilized as 3D electrochemical working electrode without being decorated onto working electrode like Au and glassy carbon electrode. High conductivity, large specific surface area, short ion diffusion path and excellent adsorption capacity of NiCoO@PPy/3D graphene efficiently improved electrochemical property for the detection of Pb. Using square-wave anodic stripping voltammetry (SWASV), a linear range between the currents and the concentrations of Pb of 0.0125-0.709 μM with a high sensitivity of 115.621 μA μM was obtained. The limit of detection can reach to 0.2 nM. In addition, the fabricated sensor of Pb also had good selectivity, reproducibility and long-term stability. Finally, NiCoO@PPy/3D graphene electrode was utilized for determining Pb in tap water sample using the standard addition method, revealing a promising application for the quantitative detection of certain concentration ranges of Pb in real sample. [ABSTRACT FROM AUTHOR]