Synthesis of Hollow Doughnut Shape Mesoporous Silica Nanoparticle: A Case of Self-Assembly Composite Templates.

The new class of silica nanoparticles with unprecedented structural morphology is synthesized by hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of cetyltrimethylammonium bromide (CTAB), l-arginine, and ammonium metatungstate (AMT) composite template, all in aqueous ethanol. The morphology of the synthesized mesoporous silica nanoparticles (MSNs) can be tuned from a spherical to a hollow doughnut shape through a hollow sphere by controlling the concentration of AMT in the composite template. The formation mechanism of the hollow doughnut shaped MSNs (hd-MSNs) is well-explored by means of zeta potential, high-resolution transmission electron microscopy (HRTEM) with elemental mapping analysis, and X-ray photoelectron spectroscopy. The unique structure of the hd-MSNs as well as their high thermal and mechanical stability is expected to result in their application in shape-selective catalysis, drug-delivery, and sensors.