Department of Chemistry, The Pennsylvania State University, University Park, 104 Chemistry Building, Pennsylvania 16802, USA.
Analyst. 2011 Sep 21;136(18):3797-802. doi: 10.1039/c1an15448f. Epub 2011 Jul 29.
Surface chemistry plays an important role in determining flux through porous media such as in the environment. In this paper diffusive flux of nanoparticles through alkylsilane modified porous alumina is measured as a model for understanding transport in porous media of differing surface chemistries. Experiments are performed as a function of particle size, pore diameter, attached hydrocarbon chain length and chain terminus, and solvent. Particle fluxes are monitored by the change in absorbance of the solution in the receiving side of a diffusion cell. In general, flux increases when the membranes are modified with alkylsilanes compared to untreated membranes, which is attributed to the hydrophobic nature of the porous membranes and differences in wettability. We find that flux decreases, in both hexane and aqueous solutions, when the hydrocarbon chain lining the interior pore wall increases in length. The rate and selectivity of transport across these membranes is related to the partition coefficient (K(p)) and the diffusion coefficient (D) of the permeating species. By conducting experiments as a function of initial particle concentration, we find that K(p)D increases with increasing particle size, is greater in alkylsilane-modified pores, and larger in hexane solution than water. The impact of the alkylsilane terminus (-CH(3), -Br, -NH(2), -COOH) on permeation in water is also examined. In water, the highest K(p)D is observed when the membranes are modified with carboxylic acid terminated silanes and lowest with amine terminated silanes as a result of electrostatic effects during translocation.
表面化学在决定多孔介质（如环境中的）通量方面起着重要作用。本文以不同表面化学性质的多孔介质中传输为模型，测量了纳米颗粒通过烷基硅烷修饰多孔氧化铝的扩散通量。实验是作为粒径、孔径、附着碳氢链长度和链端以及溶剂的函数进行的。通过监测扩散池接收侧溶液的吸光度变化来监测颗粒通量。一般来说，与未处理的膜相比，用烷基硅烷修饰的膜的通量增加，这归因于多孔膜的疏水性和润湿性的差异。我们发现，当内部孔壁的碳氢链长度增加时，无论是在己烷还是水溶液中，通量都会下降。这些膜的跨膜传输速率和选择性与分配系数 (K(p)) 和渗透物质的扩散系数 (D) 有关。通过进行初始粒子浓度的实验，我们发现 K(p)D 随着粒子尺寸的增加而增加，在烷基硅烷修饰的孔中更大，在己烷溶液中比在水中更大。还研究了烷基硅烷末端 (-CH(3), -Br, -NH(2), -COOH) 对水中渗透的影响。在水中，当膜用羧酸末端硅烷修饰时，K(p)D 最高，而当膜用胺末端硅烷修饰时，K(p)D 最低，这是由于在易位过程中存在静电效应。
