3.3. Synthesis of HSSNs. The HSSNs could be synthesized
by changing the applied solvent to EtOH. As shown in Figure
1, monodispersed HSSNs with a relatively uniform size and a
smooth surface were obtained. The average diameter of the
particles in Figure 1 was 365 ± 49 nm. The hollow structure of
these spherical particles can be revealed by the contrast
between the dark outlier and the pale inner in the spheres
(Figure 7A). The hollow structure was also observed in broken