Gravimetric and density profiling using the combination of surface acoustic waves and neutron reflectivity.
A new approach is described herein, where neutron reflectivity measurements that probe changes in the density profile of thin films as they absorb material from the gas phase have been combined with a Love wave based gravimetric assay that measures the mass of absorbed material. This combination of techniques not only determines the spatial distribution of absorbed molecules, but also reveals the amount of void space within the thin film (a quantity that can be difficult to assess using neutron reflectivity measurements alone). The uptake of organic solvent vapours into spun cast films of polystyrene has been used as a model system with a view to this method having the potential for extension to the study of other systems. These could include, for example, humidity sensors, hydrogel swelling, biomolecule adsorption or transformations of electroactive and chemically reactive thin films. This is the first ever demonstration of combined neutron reflectivity and Love wave-based gravimetry and the experimental caveats, limitations and scope of the method are explored and discussed in detail.
Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK.
Daniel T W
DTW
Toolan
Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France.
Robert
R
Barker
School of Engineering, University of Bradford, Bradford BD7 1DP, UK.
Tim
T
Gough
Aston Institute of Materials Research, Aston University, Birmingham B4 7ET, UK.
Paul D
PD
Topham
Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, UK.
Jonathan R
JR
Howse
Division of Biomedical Engineering, Rankine Building, University of Glasgow, Glasgow G12 8QQ, UK. Electronic address: andrew.glidle@gla.ac.uk.
Andrew
A
Glidle
Interfacial characterisation; Love wave gravimetry; Neutron reflectivity; Thin film microstructure