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Zwitterion Additives in the Stöber Process for Particle Size Tuning and Silica Surface Decoration
Bricker D Like1, Izabella R Wallingford1, Matthew J Panzer1
1Department of Chemical and Biological Engineering, Tufts University, Medford, Massachusetts02155, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 20, 2026
Summary
Small-molecule zwitterions (ZIs) like trimethylglycine, l-carnitine, and l-α-glycerophosphorylcholine were added to silica nanoparticle synthesis. This method successfully reduced particle size and modified surfaces with zwitterionic moieties.
Area of Science:
- Materials Science
- Nanotechnology
- Surface Chemistry
Background:
- Zwitterionic colloidal materials offer unique antifouling and biocompatible properties.
- Silica nanoparticles are versatile materials with broad application potential.
- Surface modification is key to tailoring nanoparticle functionality.
Purpose of the Study:
- To investigate the efficacy of small-molecule zwitterions (ZIs) as additives in the Stöber process for silica nanoparticle synthesis.
- To characterize the impact of ZIs on silica particle size and surface properties.
- To explore the potential of ZIs for creating zwitterionic surface-modified silica nanoparticles.
Main Methods:
- Utilized the Stöber process with tetraethylorthosilicate (TEOS) as the silica precursor.
- Incorporated three small-molecule zwitterions: trimethylglycine (TMG), l-carnitine (CAR), and l-α-glycerophosphorylcholine (GPC).
- Characterized silica particle size using dynamic light scattering (DLS) and scanning electron microscopy (SEM).
- Analyzed surface properties and ZI presence using zeta potential measurements (PALS) and X-ray photoelectron spectroscopy (XPS).
Main Results:
- ZI additives reduced average silica particle size, with GPC causing a 46% reduction at the highest concentration.
- Zwitterionic moieties were successfully grafted onto the silica particle surfaces, evidenced by zeta potential values near 0 mV.
- XPS confirmed the presence of quaternary ammonium groups, with TMG showing a higher surface concentration compared to GPC and CAR.
Conclusions:
- Small-molecule zwitterions are effective additives for controlling silica nanoparticle size and surface modification via the Stöber process.
- This method provides a straightforward route to producing zwitterionic surface-modified silica nanoparticles.
- The findings highlight the potential of ZIs in advanced silica preparation and functionalization for diverse applications.
