2.2. Preparation of Ni(OH)2@GO nanosheets
The 0.1 mg mL-1 GO nanosheets were prepared by diluting the GO gel and then dispersed by ultrasonication. The Ni(OH)2 nanosheets were prepared following a previous method by quickly adding 2-aminoethanol (3.0 mM) aqueous solution into an equivalent volume of Ni(NO3)2 (2.0 mM) aqueous solution and then aging for 0.5 h at 20 °C. The Ni(OH)2@GO nanosheets were prepared by mixing the GO dispersion with the Ni(OH)2 dispersion. The structure of the three kinds of nanosheets was characterized by atomic force microscope (AFM, 5500, Agilent Technologies, USA) under the tapping mode. Transmission electron microscope (TEM, JEM-2100, JEOL, Japan) was also employed to observe the inner structure. The TEM samples were prepared by dropping the nanosheets dispersion on a copper grid coated with a carbon film and drying in air. Moreover, the width distribution of the nanosheets was measured by dynamic light scattering (DLS, Autosizer 4700, Malvern, UK) at 20 °C.