Mesoporous silica SBA-15 sheet with perpendicular nanochannels

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Free-standing mesoporous silica sheets with perpendicular nanochannels are highly sought after for applications in catalysis, masks, and separation.
• Existing methods often struggle to achieve controlled perpendicular orientation and thin sheet morphology.

Purpose of the Study:

• To synthesize free-standing thin sheets of mesoporous silica (SBA-15) with perpendicular nanochannels (SBA⊥).
• To investigate the influence of synthesis parameters on the structure and morphology of SBA⊥.
• To understand the templating mechanism involving a three-component amphiphile system.

Main Methods:

• Utilized a three-component amphiphile system: sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (C16TMAB), and Pluronic-123 (P123).
• Templated the condensation of sodium silicates using the amphiphile system.
• Varied experimental parameters including SDS/C16TMAB ratio, temperature, and pH to study their effects on SBA⊥ formation.

Main Results:

• Successfully synthesized SBA⊥ with uniform pore size (~9 nm), homogeneous sheet thickness (60-300 nm), and micron-scale dimensions.
• Identified optimal synthesis conditions: SDS/C16TMAB ratio of 1.5 and temperature ≥40°C.
• Demonstrated pH-dependent morphology and elucidated the role of catanionic vesicles formed by SDS/C16TMAB in templating perpendicular nanochannels.

Conclusions:

• The balanced interaction between P123/silicate and the confined surfactant bilayers of C16TMAB/SDS is crucial for forming perpendicular nanochannels.
• Low temperature and pH conditions promote segregation of PPO and PEO-oligosilicate segments, enabling control over sheet thickness.
• The study provides insights into controlling mesoporous silica structure and morphology via microphase separation principles under confinement.