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Dynamic Covalent Silica Nanoparticles for pH-Switchable Pickering Emulsions.

Gaihuan Ren1, MaoXin Wang1, Lei Wang2

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Summary

pH-responsive dynamic covalent silica nanoparticles enable switchable wettability for creating and breaking oil-water Pickering emulsions. This controllable process offers efficient emulsion separation by adjusting acidity.

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Area of Science:

  • Materials Science
  • Colloid and Surface Chemistry
  • Nanotechnology

Background:

  • Dynamic covalent chemistry offers responsive materials.
  • Surfactants are crucial for stabilizing emulsions.
  • Pickering emulsions utilize solid nanoparticles as stabilizers.

Purpose of the Study:

  • To fabricate pH-switchable silica nanoparticles.
  • To investigate their use in creating and destabilizing Pickering emulsions.
  • To demonstrate the potential for effective oil-water separation.

Main Methods:

  • Synthesized dynamic covalent silica (SiO2-B) nanoparticles via imine bonds.
  • Characterized nanoparticles using FTIR, elemental analysis, contact angle, and zeta potential.
  • Formed and destabilized oil-in-water (O/W) Pickering emulsions by adjusting pH.
  • Analyzed emulsion properties using conductivity, optical microscopy, and confocal microscopy.

Main Results:

  • SiO2-B nanoparticles exhibited switchable wettability between pH 3.5 and 7.8.
  • At pH 7.8, nanoparticles stabilized O/W Pickering emulsions.
  • Lowering pH to 3.5 dissociated imine bonds, leading to emulsion destabilization and phase separation.
  • Successful alternating stabilization and separation over three cycles were achieved.

Conclusions:

  • pH-switchable silica nanoparticles are effective stabilizers for Pickering emulsions.
  • The dynamic covalent bond allows for controlled emulsion formation and separation.
  • These systems show promise for applications in efficient oil-water separation.