Preparatoin and Function of Molecular Sieving Silica Overlayr

苯甲醛吸附在像氧化锡这样的碱性金属氧化物上，形成稳定的苯甲酸盐阴离子。另一方面，烷氧硅的化学气相沉积形成一层单层二氧化硅，完全覆盖表面。结合这两种现象，研究了一种具有分子筛分性能的二氧化硅覆盖层的新技术：在苯甲酸盐阴离子被吸附后，在氧化锡上化学气相沉积烷氧硅，预吸附的物质起模板作用，最终被去除。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行为，并受温度控制。醇氧硅的沉积量由固定在表面的醇氧硅的水解来控制。首先考察了所制备样品对不同分子大小的吸附剂的吸附性能。观察到分子的筛分特性：比模板分子大的分子很难被吸附。然后对气体传感器的应用进行了研究。为此，约一半的模板覆盖率和另一半的二氧化硅收敛是合适的。在这种样品上，对各种醛、醇、烷烃和芳香烃的传感性能由分子大小控制。此外，用萘醛代替苯甲醛作为模板。得到了分子筛的筛分性能，并明确了分子筛的筛分性能受模板分子大小的控制。氧化铝也被用作支撑。阐明了二氧化硅化学气相沉积在氧化铝上产生固体酸性，酸性受微观结构控制。预吸附模板的密度对酸度有较大影响，说明二氧化硅的微观结构受模板分子的控制。

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.