Diatom frustules decorated with zinc oxide nanoparticles for enhanced optical properties
Zinc oxide (ZnO) nanoparticles were synthesized on diatomite (DE) surface by a low
temperature sol gel technique, starting from zinc acetate dihydrate (Zn(CH3COO)2?·?2H2O)
solution in water/ethyl alcohol, in presence of triethanolamine (TEA) with functions of Zn2+
chelating agent, catalyst and mediator of nanoparticle growth on DE surface. Microstructural
features were investigated by field emission scanning electron microscopy and x-ray diffraction.
ZnO crystalline nanoparticles, well distributed both on the surface and into the porous
architecture of diatomite, were obtained just after the synthesis carried out at 80 °C without the
need of calcination treatments. The optical properties of ZnO/DE hybrid powders were
measured for the first time by means of photoacoustic spectroscopy (PAS). A new method to
retrieve both the optical absorption and scattering coefficients from PAS is here discussed for
powder aggregates. The fingerprint of the zinc oxide nanoparticles has been highlighted in the
Mie scattering resonance in the UV–Vis range, and in the enhancement of the optical absorption
with respect to diatomite.