Porous silica spheres were prepared with solid nanosilica microspheres as raw materials.In the preparation,poly(vinyl pyrrolidone) was used to protect the near surface layer,and NaOH was used to selectively etch the interior of the silica spheres.The porous silica spheres were characterized by thermogravimetric analysis,scanning electron microscopy and transmission electron microscopy,respectively.The results indicate that before and after NaOH etching,there exists porous micro-channel in silica sphere,and ...