| Porous materials, especially mesoporous materials, have attracted researchers'more and more attention due to their high surface area, ordered pore structure and narrow pore size distribution. Various porous materials with different composite, different pore structure and different pore size have been obtained by using different synthesis methods. However, in recent years, the application study for porous materials has been paid more attention in stead of the synthesis work. Many works about the application of porous materials in different fields such as optical device, biochemical sensors and environment detect and so on have been reported. In this thesis work, firstly, we synthesized mesoporous metal oxide by a hard- template method and study their optical properties. Secondly, several functional materials were encapsulated into different porous materials and their application property in humidity sensors or biosensor has been studied.Mesoporous metal oxides have potential application values in catalyze field, optical-electronics, electronic-magnetic and separation field and so on due to their some special properties such as high order, high surface area and well crystalline wall structure. Compared with single mesoporous metal oxides, double mesoporous metal oxides possess more better properties: 1) higher surface area; 2) pore size can be tailored in a certain range by adjusting the molar ratio of different metal oxides precursors and 3) the stability of double mesoporous metal oxides is obviously higher than that of single. In this work, we synthesized double metal oxides of MgO-ZnO and studied their optical propertied using mesoporous carbon CMK-3 as hard-template and metal nitrate as precursor. The study results demonstrated that mesoporous structure was formed only after the content of MgO was beyond 25%, and the pore size decreased with the increase of MgO content. Their photo luminescence property results indicated that the band-edge emission have a red shift then blue shift with the increase of MgO content. And the turning point is just at the MgO content of 25% which is a milestone these materials begin to form mesoporous structure. These entire phenomenons displayed that their optical property was affected by the pore structure.Besides of the important application in catalysis, adsorption and separation, another important application of mesoporous materials is that they can be used as host materials to encapsulate some functional materials to form host-guest materials. These host-guest materials are expected to have potential application value at nano-catalyze, electronic-sensing and biomedical and so on. At our work, conducting polymer poly-pyrrole was encapsulated into the channel of mesoporous silica SBA-15. The characterization of XRD, IR and N2-adsorption isotherm confirmed the formation of polypyrrole/SBA-15 host-guest materials. The study of humidity sensitive property indicated that the humidity sensing property of polypyrrole was improved after it was encapsulated into the pore of SBA-15. Namely, the impedance change range at the same humidity range for polypyrrole/SBA-15 was larger than that for pure polyprrrole. The main reasons are as follows: 1) the insulation nature of SBA-15 make the impedance value of Polypyrrole/SBA-15 at low relative humidity become larger. 2) Protons dissociated from water molecular interact with the imine center of pyrrole ring and transfer through the polypyrrole chains. 3) The formation of serial water layers at high relative humidity accelerated the transfer rate of H+ and H3O+, so the impedance value was decreased dramatically and the Polypyrrole/SBA-15 materials displayed better humidity sensitive property. In addition, based on this work, we also explored another two methods which can improve the humidity sensitive property of polypyrrole. The first one is to extend the polymerization time of polypyrrole. The study results demonstrated that the particle size of polypyrrole increased with the polymerization time. The increase of particle size make their surface area decreased and resulted that the interact chance between polypyrrole chains and water molecular also decreased which make the corresponding impedance increased. At high relative humidity, the appearance of large voids among polypyrrole particles and the formation of serial water layers make their impedance fall dramatically and so the polypyrrole with longer polymerization time displayed better humidity sensitive property. Dope method is also proved to be an effective method to improve the humidity sensitive property of polypyrrole. In our work, we found that Fe2+-doped polypyrrole displayed better humidity sensitive property than pure polypyrrole. The study of complex impedance spectrum demonstrated that the conduction of free Fe2+ at high relative humidity is the main contribution to the improvement of humidity sensitive property.As described above, the polypyrrole/SBA-15 host-guest materials get better humidity sensitive property. The encapsulation method provides a new way to explore new humidity sensor materials. LiCl, as a water-sensitive inorganic salt, is one of the earliest humidity sensor materials. However, it was easy to be disable at high humidity environment due to its high hygroscopic property. Therefore, in our work, we encapsulated it into the channel of as-synthesized mesoporous SBA-15 to form a host-guest composite material and study its humidity sensitive property. It was found that samples with different LiCl content displayed different humidity sensitive property. At optimized LiCl content, the sample with best humidity sensitive property was obtained. According to the analysis of humidity sensitive mechanism, the proton is the main conductive carrier at low relative humidity, and the free Li ion dominated the main conductive mode at high relative humidity. In addition, we also studied the humidity sensitive property of Li+ or K+- doped mesoporous silica SBA-15. Research results demonstrated that after doping with these ions, better humidity sensitive property was obtained.As a typical kind of biological larger molecular and special catalyst, enzyme plays an important role in human being life. The study of electrochemical property of enzyme plays an important role both in theory and in application. For the academic, the electron transfer process between enzyme and electrode surface share a similar mechanism with the redox reaction in human being body. For the application, the study of electrochemical property of enzyme play an instructive role in construct a biosensor. In our work, the electrochemical property of DMSO reductase in the presence of mediator was studied on the carbon nanotube- modified GC electrode. DMSO reductase is a Molybdenum-containing enzyme which can catalyze the reduce reaction from DMSO to DMS. During the reaction process, the oxygen atom of DMSO is transferred to molybdenum, and then is subsequently removed from molybdenum as water. So, DMSO reductase is to be considered as an ideal enzyme to construct a biosensor. Two different electrodes of DMSOR-CNT/GC and DMSOR/GC were prepared and their electrochemical response to the substrate of DMSO in the presence of mediator. The study results demonstrated that the catalytic current for both electrodes increased with the substrate concentration. However, at the same substrate concentration, the catalytic current of electrode DMSOR-CNT/GC is larger than that of DMSOR/GC, indicating that carbon nanotube can provide a beneficial microenvironment for the electron transfer between DMSO reductase and the glassy carbon electrode surface. This electrode is expected to be applicable in biosensor.
|
PDF Full Text Request