3.2.1. Hollow Tadpole-like Silica N

3.2.1. Hollow Tadpole-like Silica Nanomaterials. At the
initial stage (5 min after the addition of TEOS), the products
showed hollow hemispheres with one side open (Figure 5A).
After 10 min of reaction, the silica shell grew thicker at one
side, forming a head of the tadpole (Figure 5B). With an
increase of the reaction time to 20 min, the length of the
nanomaterials increased dramatically (Figure 5C) and a hole
formed at the tail. The length of the tadpole kept growing
within 1 h (Figure 5D) until the hole at the end of the tail was
closed. With a further increase in the reaction time to 16 h, the
size of the tadpole only showed slight changes.
3.2.2. HSiNWs. At the early stage of hollow nanowire growth
(1 h), the produced hollow nanomaterials were more likely to
have spherical shapes, as shown in Figure 6A. It is worth noting