Protocrystallinity of Monodispersed Ultra-Small Templated Mesoporous Silica Nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Mesoporous silica nanoparticles (MSNs) are versatile materials for various applications.
• Controlling the size, morphology, and porosity of MSNs is crucial for optimizing their performance.
• Ultra-small MSNs offer unique advantages due to their high surface area-to-volume ratio.

Purpose of the Study:

• To synthesize monodisperse, semi-faceted ultra-small mesoporous silica nanoparticles (US-MSNs) with controlled characteristics.
• To investigate the structural ordering and porosity of the synthesized US-MSNs.
• To evaluate the potential of these US-MSNs as supports for separation and catalysis.

Main Methods:

• Synthesis via short-time hydrolysis of tetraethoxysilane (TEOS) at room temperature.
• Nucleation quenching through dilution and two-step pH adjustment for stabilization.
• Pore size control using cetyltrimethylammonium bromide (CTAB) and F127 surfactant.
• Characterization using dynamic light scattering (DLS), scanning transmission electron microscopy (STEM), and 3D high-resolution transmission electron microscopy (3D HR-TEM).

Main Results:

• Successfully synthesized monodisperse US-MSNs (20-25 nm) with controlled pore sizes.
• Observed partial ordering and a protocrystalline state with coexisting four-, five-, and sixfold patterns.
• Achieved a hierarchical porosity with internal pores (3.9 ± 0.2 nm) and packing voids (68 ± 7 nm) after calcination.
• Harvested a powder with approximately 60% silica yield after one month via flocculation and centrifugation.

Conclusions:

• The developed method allows for the controlled synthesis of US-MSNs with tunable porosity.
• The protocrystalline nature and hierarchical porosity are key features for advanced applications.
• These US-MSNs show significant potential as supports in separation and catalysis due to their unique structural properties.