| Since the discovery of the ordered mesoporous silica MCM-41, which reported by the Mobile's scientists in 1992, more and more researchers have devoted themselves to the synthesis, characterization and applications of mesoporous materials. Over the past two decades, one could tailor and pre-design the pore structure, mesoscale arrangement and composition of ordered mesoporous materials to same degree, and find some potential applications. However, there are still two points must be paid attention to. Firstly, there are still many mesoporous materials which could not be prepared by the current technology, and the complex processes and high cost limit their practical applications; Secondly, compared to the achievements in synthesis, the practical application of mesoporous materials is relative backward, and most of the research results are merely in the laboratory stages. Therefore, in the future, one must continue to improve the synthesis technique of mesoporous materials, while increasing the emphasis on their practical applications. In this dissertation, we synthesized several different types of mesoporous materials, and studied their gas sensing (H2O, H2S) and fluorescence properties. By this way, we hope to find out the relationship between the structure and the properties of mesoporous materials, which can be beneficial to the future design of functional materials.With the development of science and society, chemical sensors have been widely used in human daily life and industrial production. Besides, benefit from the high surface area, regularly arranged mesoporous with various topologies, tunable pore size and large pore volume, mesoporous materials have attracted more and more attention from materials scientists in chemical sensors. However, current research mainly focuses on the field of detection of toxic substances, while there are few works on humidity sensors, which exert great influences on a variety of industries and make human life comfortable as well. Here, we studied the humidity sensitive characteristics of several mesoporous materials, and try to find out the relationship between mesoporous structure and their properties.Inspired by the view of that electrolyte/ceramic composite can greatly improve the humidity sensitive properties, we propose to use mesoporous silica materials instead of ceramic electrolyte to develop humidity-sensing materials. In chapter 2, Li+ doped SBA-16 with three dimension cubic mesostructure and inerratic polyhedron morphology has been successfully investigated as humidity-sensing material. After doping of 10% (wt) lithium chloride, the impedance of SBA-16 has changed more than three orders of magnitude over almost the whole humidity range, with fast response time, and relatively low hysteresis. Through the analysis of the nature of the Li-doped SBA-16, we recognized that in addition to the high specific surface area, morphology and structure optimization of the sample also play important roles in improving the humidity sensitive performance of mesoporous materials.Lithium chloride is one of the oldest electrolyte humidity sensing materials, which shows good characteristic properties at relatively low RH%. Here, the instability of lithium chloride under high humidity is ingeniously avoided by the combination of inorganic skeleton and organic template, and LiCl-doped SBA-16 materials exhibit better capability over the whole range of RH%. However, taking into account the shortcomings of the electrolyte, doped one may be accompanied with long-term instability. Therefore, two types of non-doped mesoporous humidity-sensing materials were studied in chapter 3. Considering that microwave digestion(MWD) is a new effective technique to remove organic surfactant, which shows many advantages over other methods, such as lower structural shrinkage, larger pores, additional pores in the silica wall, and shorter working time, especially, it brings in large numbers of hydroxyl groups, which may facilitate the improvement of its humidity sensing property, herein, we presented the investigation on the humidity sensing properties of mesoporous silica treated by MWD. Moreover, we also studied the humidity sensitive properties of mesoporous cerium oxide. In this chapter, we found two kinds of non-doped humidity sensing materials. And, through the study on structure and humidity sensing properties, we confirmed that the morphology and structure optimization of the mesoporous materials indeed improve the performance of mesoporous materials, and this may be benefit to the design of other functional materials.Hydrogen sulfide is a kind of colorless and toxic gas,with rotten eggs smell. It is mainly originated from iron and steel, oil refining, pharmaceutical, paper and solid waste, as well as life waste, and harm for the lives of people and animals. In chapter 4, we reported a simple and effective method for in-suit synthesis of Pt-doped mesoprous In2O3, which was successfully controlled in both nanometer (meso-structure) and micrometer (morphology) scale. And the H2S sensor based on Pt-doped mesoporous In2O3 was also investigated, which exhibited excellent sensing properties and could respond to 2 ppm H2S at reduced working temperature. This further proves that except for the high specific surface area, the optimization of the morphology and structure of mesoporous materials play an important role in improving the performance of the materials, which is in favor of the designing of other functional materials.In the previous chapter, we studied the relationship between structure and gas sensing (H2O, H2S) of several mesoporous materials. However, it is mainly focused on the efficient use of the pore surface, and not concerns the effect of the pore itself. In chapter 5, Rhodamine B, a fluorescent dye, was introduced into the pores of three different mesoporous silica materials with surface amino modification, and the photoluminescence (PL) of the samples was studied. For the first time, it was observed that not only the size, but also the structure and the curvature of the mesopore have a great influence on PL properties of the host-guest materials, and this have some important guiding significance for the future design of solid dye lasers. |
