title: Selective response of mesoporous silicon to adsorbants with nitro groups.
abstract: We demonstrate that the electronic structure of mesoporous silicon is affected by adsorption of nitro-based explosive molecules in a compound-selective manner. This selective response is demonstrated by probing the adsorption of two nitro-based molecular explosives (trinitrotoluene and cyclotrimethylenetrinitramine) and a nonexplosive nitro-based aromatic molecule (nitrotoluene) on mesoporous silicon using soft X-ray spectroscopy. The Si atoms strongly interact with adsorbed molecules to form Si-O and Si-N bonds, as evident from the large shifts in emission energy present in the Si L(2,3) X-ray emission spectroscopy (XES) measurements. Furthermore, we find that the energy gap (band gap) of mesoporous silicon changes depending on the adsorbant, as estimated from the Si L(2,3) XES and 2p X-ray absorption spectroscopy (XAS) measurements. Our ab initio molecular dynamics calculations of model compounds suggest that these changes are due to spontaneous breaking of the nitro groups upon contacting surface Si atoms. This compound-selective change in electronic structure may provide a powerful tool for the detection and identification of trace quantities of airborne explosive molecules.
authors.affiliation: Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada. john.mcleod@usask.ca
authors.forename: John A
authors.initials: JA
authors.lastname: McLeod
authors.forename: Ernst Z
authors.initials: EZ
authors.lastname: Kurmaev
authors.forename: Peter V
authors.initials: PV
authors.lastname: Sushko
authors.forename: Teak D
authors.initials: TD
authors.lastname: Boyko
authors.forename: Igor A
authors.initials: IA
authors.lastname: Levitsky
authors.forename: Alexander
authors.initials: A
authors.lastname: Moewes