Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.
Chemistry. 2012 Mar 5;18(10):2912-22. doi: 10.1002/chem.201102084. Epub 2012 Jan 30.
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.
我们证明了介孔硅的电子结构会受到硝基爆炸物分子以化合物选择性的方式吸附的影响。这种选择性响应通过使用软 X 射线光谱探测两种硝基分子爆炸物（三硝基甲苯和环三亚甲基三硝胺）和一种非爆炸硝基芳香族分子（硝基甲苯）在介孔硅上的吸附来证明。从 Si L（2,3）X 射线发射光谱（XES）测量中存在的发射能的大位移可以明显看出，Si 原子与吸附分子强烈相互作用，形成 Si-O 和 Si-N 键。此外，我们发现介孔硅的能隙（带隙）会根据吸附剂而变化，这是根据 Si L（2,3）XES 和 2p X 射线吸收光谱（XAS）测量来估计的。我们对模型化合物的从头算分子动力学计算表明，这些变化是由于硝基基团在接触表面 Si 原子时自发断裂引起的。这种电子结构的化合物选择性变化可能为检测和识别空气中痕量爆炸分子提供一种强大的工具。
