Ultrathin NiS/Ni(OH) Nanosheets Filled within Ammonium Polyacrylate-Functionalized Polypyrrole Nanotubes as an Unique Nanoconfined System for Nonenzymatic Glucose Sensors.

Ultrathin two-dimensional NiS/Ni(OH) nanosheets (NiS/Ni(OH) NSs) were successfully filled within the hollow interiors of ammonium polyacrylate-functionalized polypyrrole nanotubes (NHPA/PPyNTs) by a simple solvothermal method. This kind of novel hierarchical nanostructures with typical structural features of a nanoconfined system, denoted by NiS/Ni(OH)/NHPA/PPyNTs, were prepared by two main sections: polyacrylic acid (PAA) was first polymerized on PPyNTs containing vinyl groups, and the obtained PAA/PPyNTs exhibited a typical Janus structure, whose external surface was covered with carboxyl groups and the internal surface was still covered with PPy chains; second, Ni ions as a precursor were facilely combined with -NH- segments in PPy chains by the coordination interaction under the solvothermal environment; therefore, NiS/Ni(OH) NSs (<1 nm) were well distributed on the internal surface of NHPA/PPyNTs by the in situ growth. Because of the synergistic effects of ionizable NHPA, PPy with good conductivity, NiS and Ni(OH) with electrocatalytical activity, as well as the nanoconfinement effect, the obtained NiS/Ni(OH)@NHPA/PPyNTs exhibited excellent electrocatalytic performance for detecting glucose. Sufficiently thin shells composed of ionizable NHPA and good conductive PPyNTs can not only promote the electronic transmission effectively during the electrochemical detection of glucose but also hardly limit the transport of glucose and products. In addition, ultrathin NiS/Ni(OH) NSs may further enhance the electrocatalytic performance for glucose because of the more exposed active sites with the large surface area. Therefore, NiS/Ni(OH)@NHPA/PPyNTs can be applied as a good electrode material with stability and sensitivity for building a nonenzymatic glucose sensor.