TEM micrographs were acquired on a transmission electron microscope (JEM-2100, JEOL, Japan) with an accelerating voltage of 100–120kV in conjunction with selected area electron diffraction (SAED). SEM micrographs were obtained using a scanning electron microscope (JSM-6400, JEOL, Japan) with an accelerating voltage of 15kV. A drop of the nanoparticle suspension was placed on a glass slide and dried overnight. After mounting the slide on aluminum pin,thesamplewascoatedwithagoldlayerundervacuumat20kV for 90s. The coated sample was then mounted on an SEM stud for visualization. For both SEM and TEM, the micrographs shown are representative of at least 6 fields of view per sample, and 3 independent samples.