A novel approach to the synthesis of Zn 2 SiO 4 :Mn luminescent nanoparticles

In this study, manganese doped zinc sulfide nanoparticles with luminescence properties (Mn 2+ ions) were synthesized together with silica-aerogel particles. The effect of temperature variations on the optical properties of the composite was investigated. X-ray diffraction patterns (XRD) showed the transformation of ZnS (sphalerite) to Zn 2 SiO 4 (willemite) after heat treatment. Both silica aerogel and as-deposited SiO 2 –ZnS:Mn nanocomposites contained nanoparticles with emission wavelength of up to 30 nm. The heat treatment caused an obvious increase in the particle size to nanometer scale. Photoluminescence (PL) spectra revealed that ZnS:Mn possesses an emission peak at 590 nm, which was quenched by increasing the Mn content above 2.5% mol. In the as-deposited SiO 2 –ZnS:Mn spectra, an extra peak in the blue region was observed which is related to the silica structure. However, the heat treatment led to the appearance of strong green emission peak at 527 nm due to the formation of willemite which was quenched at higher temperatures due to the change of structure from willemite to tridymite. Finally, two luminescent inks were produced by as-deposited and heat treated SiO 2 –ZnS:Mn nanocomposites in water-based solvents as security inks.