Probing the location of light-responsive silica particles at air-liquid interface using neutron reflectometry

The possibility to break on demand a stable emulsion is pivotal for their formulations in many industrial applications. In contrast to
classical Pickering emulsions, these smart emulsions responds to changes in their environment. Recently, we develop an innovative light-
responsive water-in-oil (w/o) Pickering system based on azobenzene-modified silica particles as the stabiliser. A key aspect that must be known is where the particle sits in the interface. This will allow us to predict a-priori which kind of emulsion (oil-in-water or vice-versa) and how stable it will be. Since the particle adsorption, packing and its position with respect to the interface depends on the irradiation light, it is essential to probe it in-situ. This makes most of the available techniques not suitable since they all request the deposition and treatment of the particles. Here we propose to use neutron reflectometry to access the particle position at air-water and air-oil interface using the Langmuir trough environment. We will perform measurements at different contrasts and fit the data with model based on a combination of slabs, Gaussian and Log-normal curves.