Setyan A, Sauvain J-J, Rossi M J
Institut Universitaire Romand de Santé au Travail (IST), Université de Lausanne et Université de Genève, CH-1011 Lausanne, Switzerland.
Phys Chem Chem Phys. 2009 Aug 7;11(29):6205-17. doi: 10.1039/b902509j. Epub 2009 May 15.
Six gases [N(CH(3))(3), NH(2)OH, CF(3)COOH, HCl, NO(2) and O(3)] were selected to probe the surface of seven different types of combustion aerosol samples (amorphous carbon, flame soot) and three types of TiO(2) nanoparticles using heterogeneous, i.e. gas-surface reactions. The gas uptake to saturation of the probes was measured under molecular flow conditions in a Knudsen flow reactor and expressed as a density of surface functional groups on a particular aerosol, namely acidic (carboxylic) and basic (conjugated oxides such as pyrone, N-heterocycle and amine) sites, carbonyl (R(1)-C(O)-R(2)) and oxidizable (olefinic, -OH) groups. The limit of detection was generally well below 1% of a formal monolayer of adsorbed probe gas. With few exceptions most investigated aerosol samples interacted with all probe gases to various extents which points to the coexistence of different functional groups on the same aerosol surface such as acidic and basic groups. Generally, the carbonaceous particles displayed significant differences in surface group density: Printex 60 amorphous carbon had the lowest density of surface functional groups throughout, whereas Diesel soot recovered from a Diesel particulate filter had the largest. The presence of basic oxides on carbonaceous aerosol particles was inferred from the ratio of uptakes of CF(3)COOH and HCl owing to the larger stability of the acetate compared to the chloride counterion in the resulting pyrylium salt. Both soots generated from a rich and a lean hexane diffusion flame had a large density of oxidizable groups similar to amorphous carbon FS 101. TiO(2) 15 had the lowest density of functional groups studied for all probe gases among the three TiO(2) nanoparticles despite the smallest size of its primary particles. The technique used enabled the measurement of the uptake probability of the probe gases on the various supported aerosol samples. The initial uptake probability, gamma(0), of the probe gas onto the supported nanoparticles differed significantly among the various investigated aerosol samples but was roughly correlated with the density of surface groups, as expected.
选择了六种气体[N(CH(3))(3)、NH(2)OH、CF(3)COOH、HCl、NO(2)和O(3)]，通过非均相（即气-固表面反应）来探测七种不同类型的燃烧气溶胶样品（无定形碳、火焰烟灰）和三种类型的TiO(2)纳米颗粒的表面。在克努森流动反应器中，于分子流条件下测量探针气体的饱和吸附量，并表示为特定气溶胶上表面官能团的密度，即酸性（羧基）和碱性（共轭氧化物，如吡喃酮、N-杂环和胺）位点、羰基（R(1)-C(O)-R(2)）和可氧化（烯属、-OH）基团。检测限通常远低于吸附探针气体单分子层的1%。除少数例外，大多数研究的气溶胶样品与所有探针气体都有不同程度的相互作用，这表明同一气溶胶表面存在不同的官能团，如酸性和碱性基团。一般来说，碳质颗粒在表面基团密度上表现出显著差异：Printex 60无定形碳的表面官能团密度始终最低，而从柴油颗粒过滤器回收的柴油烟灰的表面官能团密度最大。由于所得吡喃鎓盐中醋酸根离子比氯离子更稳定，通过CF(3)COOH和HCl的吸附量之比推断出碳质气溶胶颗粒上存在碱性氧化物。富和贫己烷扩散火焰产生的两种烟灰都有大量类似于无定形碳FS 101的可氧化基团。尽管TiO(2) 15的初级颗粒尺寸最小，但在三种TiO(2)纳米颗粒中，其对所有探针气体的官能团密度最低。所采用的技术能够测量探针气体在各种负载气溶胶样品上的吸附概率。在各种研究的气溶胶样品中，探针气体在负载纳米颗粒上的初始吸附概率γ(0)有显著差异，但正如预期的那样，大致与表面基团密度相关。
