Neutron reflection from wet interfaces

Abstract

Neutron reflection is one of the few newly developed techniques capable of probing structure at wet surfaces, i.e. air/liquid, solid/liquid and liquid/liquid interfaces. Although neutron scattering is not intrinsically sensitive to surfaces, the grazing incidence geometry of neutron reflection and the possibility of varying neutron refractive indices by isotopic substitution, particularly H/D substitution, make reflection extremely sensitive to selected parts of many interfacial layers. The technique is able to probe the average structure along the surface normal in a number of situations where the layer is too disordered or complex to be investigated by other methods. The application of neutron reflection to small molecules, surfactants, polymers and polymer–surfactant mixtures at the air/water interface, and examples of the behaviour of surfactants, proteins and polymers at the buried solid/liquid interface are described. Where appropriate the scope of neutron reflection relative to other new techniques is assessed.