The solution A was drop casted on the glass substrate and its surface morphology was analyzed by capturing the SEM images at different magnifications (Fig. S1, see Supplementary information). The silica particles with size
distribution in the range of 0.5–30 mm were observed. The surface of big size silica
particles shows porous as well asshriveled morphology, however small size silica particles show
smooth spherical shape. During drying, slow evaporation of solvent from the silica spheres may
cause little shrinkage of silicate shell and thus further condensation achieves a porous as well
as shriveled morphology on the surface of silica particles [19].