The Analysis and Interpretation of Neutron and X-ray Specular Reflection

Abstract

Methods of analysing neutron and X-ray specular reflection from interfacial systems are reviewed. Normally, the profile of the scattering-length density is determined in such experiments but here particular emphasis is given to the determination of the interfacial composition profile using partial structure factors and simultaneous fitting of sets of reflectivity profiles from a given structure, obtained either by isotopic substitution or by the use of neutrons and X-rays together. Aspects of the analysis of reflectivity data in terms of the resolution of the experiment, the phase problem and the possible ways of describing the structure of an interface are considered with reference to an unusually large set of independent data from isotopic species of a monolayer of hexadecyltrimethylammonium bromide adsorbed at the air/water interface. Data from another surfactant, the monododecyl ether of triethylene glycol, is used to assess the optimum choice of isotopic composition for combining a single set of neutron data with an X-ray reflectivity profile from an adsorbed layer at the air/water interface.

Interfacial assembly of proteins and peptides: recent examples studied by neutron reflection

“…The principle of specular neutron reflection has been described in a number of reviews (Penfold & Thomas 1990;Lu et al 1996Lu et al , 2000Penfold et al 1997;Lu & Thomas 1998). The reflection of neutrons at a flat surface is comparable to light reflection.…”

“…The kinematic approximation as outlined in equations (2.2) -(2.4) depicts a straightforward relation between neutron reflectivity in abstract space and interfacial structure in real space, and has been extensively used to analyse reflectivity profiles measured at the air -water interface by means of partial structure factors (Penfold & Thomas 1990;Lu et al 1996Lu et al , 2000Penfold et al 1997;Lu & Thomas 1998). However, the advantage of such an approach becomes less obvious when used for resolving the interfacial structure at the solid -water interface due to more complex structural correlations.…”

Adsorbed and free lipid bilayers at the solid-liquid interface

“…ies of nanometer-thick monomolecular layers of phospholipid molecules at the air-water interface [5][6][7][8]. However, bilayers of phospholipids are barely stable at the air-water interface [9] and require hydrophilic media on both sides.…”

Interfacial recognition of human prostate-specific antigen by immobilized monoclonal antibody: effects of solution conditions and surface chemistry

“…The background was found to be typically around 3 Â 10 26 in D 2 O. The software called DATAFIT using the kinematic approximation as outlined in the previous review papers has been used to analyse reflectivity profiles by means of partial structure factors [22,23,30,31]. Fitting was initiated with a uniform layer followed by adding additional layers until a satisfactory fit was obtained.…”