Issue 31, 2022

Light-responsive Pickering emulsions based on azobenzene-modified particles


Light-responsive particle-stabilised (Pickering) emulsions can in principle be selectively emulsified/demulsified on-demand through the remote application of light. However, despite their wide-ranging potential in applications such as drug delivery and biphasic catalysis, their rational design is extremely challenging and there are very few examples to date. Herein, we investigate a model system based on silica particles functionalised with azobenzene photoswitches to understand the key factors that determine the characteristics of light-responsive Pickering emulsions. The particle hydrophobicity is tuned through judicious variation of the spacer length used to graft the chromophores to the surface, the grafting density, and irradiation to induce transcis photoisomerisation. For select emulsions, and for the first time, a reversible transition between emulsified water-in-oil droplets and demulsified water and oil phases is observed with the application of either UV or blue light, which can be repeatedly cycled. A combination of surface energy analysis and optical microscopy is shown to be useful in predicting the stability, and expected light-response, of a given emulsion. Using the observed trends, a set of design rules are presented which will help facilitate the rational design, and therefore, more widespread application of light-responsive Pickering emulsions.

Graphical abstract: Light-responsive Pickering emulsions based on azobenzene-modified particles

Supplementary files

Article information

Article type
27 May 2022
03 Jul 2022
First published
26 Jul 2022
This article is Open Access
Creative Commons BY license

Soft Matter, 2022,18, 5770-5781

Light-responsive Pickering emulsions based on azobenzene-modified particles

K. D. Richards and R. C. Evans, Soft Matter, 2022, 18, 5770 DOI: 10.1039/D2SM00697A

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