# Stöber synthesis of monodisperse silica spheres

> Tetraethyl orthosilicate (TEOS) is added to a stirred mixture of ethanol, water and ammonia. Ammonia catalyses the hydrolysis of TEOS to silicic acid and its condensation into Si–O–Si; nuclei form and then grow evenly, giving a milky suspension of uniform silica spheres. Stöber, Fink and Bohn obtained diameters from below 0.05 µm to 2 µm by choosing the alcohol, ammonia and water amounts.

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- Updated: 2026-10-14
- Category: Nanomaterial synthesis
- Method: Silica synthesis, bottom-up
- Starting materials: TEOS (Si(OC₂H₅)₄) in ethanol with water and ammonia
- Product: Monodisperse amorphous silica spheres in suspension
- Typical size: From below 0.05 µm to 2 µm in diameter (Stöber, Fink & Bohn)
- Key result: Very uniform, smooth, amorphous spheres
- Scalability: High: simple reagents, one pot
- Figure: 1920 × 1080 px, 73 editable layers (16 generated objects with settings)

## Steps

1. **Medium**: Ethanol, water and ammonia, stirred
2. **Add TEOS**: Hydrolysis: Si(OC₂H₅)₄ + 4H₂O → Si(OH)₄ + 4C₂H₅OH
3. **Condensation and nucleation**: Si–OH groups condense into Si–O–Si; small nuclei form
4. **Growth**: The nuclei grow evenly into uniform spheres; the suspension turns milky
5. **Collect**: Centrifuge and wash, or use the suspension directly

## Strengths

- Excellent size uniformity
- Size tunable by ammonia, water and alcohol
- Easy surface chemistry (silanols)

## Limitations

- Large spheres are harder to keep monodisperse
- Dilute suspensions; ethanol-heavy
- Particles are microporous rather than ordered-porous

## Uses

- Colloidal and photonic crystals
- Cores for core–shell particles
- Coatings and fillers
- Model colloids

## References

1. Stöber, Fink & Bohn, “Controlled growth of monodisperse silica spheres in the micron size range”, J. Colloid Interface Sci. 1968. https://doi.org/10.1016/0021-9797(68)90272-5 (method origin)
2. Hench & West, “The sol-gel process”, Chem. Rev. 1990. https://doi.org/10.1021/cr00099a003 (further reading)

Credit: Redrawn and simplified after Stöber, Fink & Bohn, J. Colloid Interface Sci. 1968 (doi:10.1016/0021-9797(68)90272-5).

## Questions

**What does the “Stöber synthesis of monodisperse silica spheres” template show?** Tetraethyl orthosilicate (TEOS) is added to a stirred mixture of ethanol, water and ammonia. Ammonia catalyses the hydrolysis of TEOS to silicic acid and its condensation into Si–O–Si; nuclei form and then grow evenly, giving a milky suspension of uniform silica spheres. Stöber, Fink and Bohn obtained diameters from below 0.05 µm to 2 µm by choosing the alcohol, ammonia and water amounts.

**What are the steps shown in “Stöber synthesis of monodisperse silica spheres”?** 1. Medium: Ethanol, water and ammonia, stirred. 2. Add TEOS: Hydrolysis: Si(OC₂H₅)₄ + 4H₂O → Si(OH)₄ + 4C₂H₅OH. 3. Condensation and nucleation: Si–OH groups condense into Si–O–Si; small nuclei form. 4. Growth: The nuclei grow evenly into uniform spheres; the suspension turns milky. 5. Collect: Centrifuge and wash, or use the suspension directly.

**What are the starting materials and the product?** Starting materials: TEOS (Si(OC₂H₅)₄) in ethanol with water and ammonia. Product: Monodisperse amorphous silica spheres in suspension.

**Which papers is “Stöber synthesis of monodisperse silica spheres” based on?** Stöber, Fink & Bohn, “Controlled growth of monodisperse silica spheres in the micron size range”, J. Colloid Interface Sci. 1968 (doi:10.1016/0021-9797(68)90272-5); Hench & West, “The sol-gel process”, Chem. Rev. 1990 (doi:10.1021/cr00099a003).

**Can I edit the “Stöber synthesis of monodisperse silica spheres” template?** Yes. Open it in the LabCanvas editor: all 73 layers are editable, including 16 generated objects (structures, plots, equipment) with their own settings. Change the text, colours and layout, then export PNG, TIFF, SVG or PDF.

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