title: Depth profiling of sterically-stabilised polystyrene nanoparticles using laser ablation/ionisation mass spectrometric methods.
abstract: An aerodynamic lens has been used to introduce polystyrene nanoparticles into an apparatus that combines laser vaporisation with mass spectrometric measurements of ion intensity. The particles have a mean diameter of 129 nm and are sterically-stabilised with poly(ethylene glycol) which coats the surface to a depth of approximately 5 nm. Measurements have been made at wavelengths of 266, 355, and 523 nm, and over a range of laser powers. The results provide clear evidence that depth profiling can be achieved by changing the wavelength of the ablating radiation, but that changes in power at a single wavelength have little influence on the range of ions observed. At 523 nm the mass spectra are predominantly derived from surface-bound material, whilst at 266 nm the dominant contribution is from ions related to the polystyrene core of the particles. It is proposed that these differences in behaviour can be equated with existing models of the laser ablation process.
authors.affiliation: Department of Chemistry, University of Sussex, Falmer, Brighton, UK.
authors.forename: Albert
authors.initials: A
authors.lastname: Pegus
authors.forename: David
authors.initials: D
authors.lastname: Kirkwood
authors.forename: Dean B
authors.initials: DB
authors.lastname: Cairns
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Stace