Preparatoin and Function of Molecular Sieving Silica Overlayr

苯甲醛被吸附在诸如氧化锡的碱性金属氧化物上以形成稳定的苯甲酸根阴离子。另一方面，硅醇盐的化学气相沉积形成二氧化硅的单层以完全覆盖表面。将这两种现象结合起来，研究了一种新的制备具有分子筛性能的SiO2覆盖层的方法：在吸附苯甲酸根阴离子后，在氧化锡上进行硅醇盐的化学气相沉积，使预吸附的物种起到模板剂的作用并最终被去除，并在初步实验的基础上确定了制备条件。苯甲醛的吸附行为为化学吸附，且受温度控制。硅醇盐的沉积量由锚定在表面上的醇盐的水解来控制。首次考察了由此制备的样品对不同分子尺寸的吸附物的吸附性能。观察到了分子筛效应，即比模板分子大的分子不易被吸附，并考察了其在气敏传感器中的应用。为此目的，约一半的模板覆盖率和另一半的二氧化硅收敛率是合适的。在这种样品上，对各种醛、醇、烷烃和芳烃的传感性能受分子大小的控制，并且用萘醛代替苯甲醛作为模板。同时也得到了分子筛的性质，并阐明了分子筛的性质受模板分子大小的控制。研究表明，氧化硅在氧化铝表面的化学气相沉积产生了固体酸性，而酸性受微观结构的控制。预吸附模板剂的浓度对二氧化硅的酸性有很大的影响，表明二氧化硅的微观结构受模板剂分子的控制。

Benzaldehyde is adsorbed on such a basic metal oxide as tin oxide to form a stable benzoate anion. On the other hand, the chemical vapor deposition of silicon alkoxide forms a monolayr of silica to cover the surface completely. By combining these two phenomena, a novel technique was investigated to obtain a silica overlayr possessing a molecular sieving property : the chemical vapor deposition of silicon alkoxide was done on tin oxide after the benzoate anion had been adsorbed, and the pre-adsorbed species playd a role of template and was finally removed.The conditions of preparation was determined based on the preliminary experiments. The adsorption behavior of benzaldehyde was that of the chemisorption and controlled by the temperature. The deposition amount of silicon alkoxide was controlled by the hydrolysis of alkoxide anchored on the surface.The adsorption property of thus prepared sample was first examined for the adsorbates with various molecular sizes. The molecular sieving property was observed : the molecule larger than the template molecule became hard to be adsorbed.The application to the gas sensor was then examined. For this purpose, about a half of the coverage by the template and another half of the converge by silica were suitable. On such a sample, the sensing property was controlled by the molecular size for various aldehydes, alcohols, alkanes and aromatic hydrocarbons.Furthermore, naphtaldehyde was used as the template in place of the benzaldehyde. The molecular sieving property was also obtained, and clarified to be controlled by the template molecular size.Alumina was also used as the support. It has been clarified that the chemical vapor deposition of silica on alumina generated the solid acidity, and the acidity was controlled by the microstructure. The density of pre-adsorbed template strongly affected the acidity, showing the microstructure of silica was controlled by the template molecule.