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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]

Here, a supramolecular self-assembly hydrogel was designed for SnO-based anode through electrostatic interaction and ionic bonding between poly(allylamine hydrochloride) (PAH) chain and gelator phytic acid. Microrheology measurement was employed to investigate the self-sorting mechanism of the hierarchical nanostructured PAH. Results confirmed that ionically cross-link PAH improves the structural integrity of SnO nanospheres due to the reversible ionic bonding and thus increases the lifetime of the electrodes obviously. Besides, multi-walled carbon nanotubes (MWCNTs) were applied to improve the electrochemical performance of hollow SnO nanospheres due to their high conductivity. Results confirmed that the conductive network constructed by MWCNTs reduces the polarization of the composites while increases the specific capacity of the electrodes. Attributed to the synergistic effect of PAH-60 and MWCNTs, the composite electrodes show excellent electrochemical performance with a reversible capacity of 574 mAh g after 100 cycles at 100 mA g, a discharge capacity of 321 mAh g at 2000 mA g and a spring-back capacity of 506 mAh g at 200 mA g. Additionally, the prepared composite electrodes were observed to have a complete network structure after rate capability test, demonstrating a superior structural stability. [ABSTRACT FROM AUTHOR]

A novel MWCNT/long nanotubular TiO(B) loaded with SnO nanocrystals (SnONC/TiO(B)NT/MWCNT) ternary composite has been prepared by two-step hydrothermal method and used as the anode material for the first time. In this work, the mechanical stirring improved the diffusion and surface reaction rates of reactants and promoted the appearance of longer intermediate TiO(B) nanosheets, leading to the formation of TiO(B) nanotubes with a length of ~9 μm. Among the SnONC/TiO(B)NT/MWCNT composite, the wrapping and mechanical supporting functions of TiO(B) nanotubes can effectively avoid the pulverization and aggregation of SnO nanocrystals (SnONC) in lithium-ion charging and discharging process. Moreover, the synergistic effects of nanotubular TiO(B) coating layer and three-dimensional interconnected network structure composed of TiO(B) nanotubes and MWCNT were taken to mitigate volume expansion of SnONC and improve the transport of lithium ion and electron in the network. Tested as anode materials, the SnONC/TiO(B)NT/MWCNT composite maintained 211 mAh g at 3000 mA g after three testing processes with alternative current density of 200 and 3000 mA g and could rebound to 338 mAh g at a current density of 200 mA g, indicating an effective way to optimize electrochemical properties of SnO as anode material. [ABSTRACT FROM AUTHOR]