Mesoporous structures from supramolecular assembly of in situ generated ZnS nanoparticles

A stable mesoporous network formed by nanoparticles of ZnS was achieved by an ultrasound-mediated fabrication method. The ZnS nanoparticles were generated in situ during the sonication, and dodecylamine was used as the structure-directing agent. All the synthesized materials were characterized using X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), electron diffraction, energy dispersive analysis of X-rays, Fourier transform infrared, UV-vis diffuse reflectance spectroscopy, and thermal analyses. After the template extraction, the obtained mesoporous ZnS possessed a high surface area of 210 m²/g with an average pore diameter of 28 Å. HRTEM analysis revealed a mesostructure consisting of closely spaced ZnS nanocrystallites of ∼3 nm size. The individual nanocrystallites showed typical lattice spacings corresponding to the cubic phase of ZnS. The existence of ZnS particles in a compact structure resulted in a dramatic increase in the thermal stability of the cubic phase. As revealed from optical absorption measurements, the ZnS nanoparticles exhibited quantum-size effect with a blue shift in the band gap. Finally, a systematic analysis was carried out to find the role of ultrasound on the supramolecular assembling process that leads to the generation of a mesostructure.