The UV/VIS spectra for the solution contain ZnO@SiO2 and ZnO@
SiO2@mSiO2 NPs in HY surfactant Fig. 6(a–c). HY surfactant was used
to obtain a homogenous solution of un-coated and coated silica zinc
oxide particles. Two peaks at 359, 290 nm are shown in Fig. 6(a–c),
that characteristic for the presence of ZnO nanoparticles [22,33]. It is
found that there is a decreasing of the absorption band intensities as
the number of shells of coated silica is build up on zinc oxide (ZnO@
SiO2 to ZnO@SiO2@mSiO2). There was a shift of the absorption band at
307 nm for the free uncoated ZnO to shorter wavelength at 290 nm
for ZnO@SiO2 and at 283 nm for ZnO@SiO2@mSiO2 . The blue shift of
the absorption band 307 nm to shorter wavelength is probably due to
decreasing of the particle size. No peaks are observed for the ZnO free
coated silica-mesosilica indicating the absence of the shell core of zinc
oxide (Fig. 7b) when treated with HCl acid in comparison with that of
ZnO@SiO2(Fig. 7b).