Figure 4From: Synthesis of multi-shelled ZnO hollow microspheres and their improved photocatalytic activityLow- and high-magnification SEM images of the triple-, double-, and single-shelled ZnO hollow spheres and ZnO nanoparticles. (a, e) Triple-, (b, f) double-, (c, g) and single-shelled ZnO hollow spheres and (d, h) ZnO nanoparticles.Back to article page