Preparation, Characterization And Photocatalytic Activities Of CdS-modified SBA-15

Nanomaterials and mesoporous meterials are two important parts of nanostructrued materials, and have attracted extensive attention due to their great potential applications. The research in mesoporous materials is mainly focused on the synthesis of mesoporous meterials with novel structures and functionalities. In the field of nanomaterials, the morphology control and assembly of low-dimensional nanomaterials dominate the scientific research. In this thesis, the synthesis of low-dimensional nanomaterials was carried out via a layer-by-layer self-assembly technique and a templating approach by employing mesporous silicas as hard templates.In recent years, many literatures have been reported on synthesize CdS nanomaterials in the channel of mesoporous materials. Some efforts have been carried out to graft CdS onto the SBA-15 inner surface. Nevertheless, the uniform and size of the CdS in the mesoporous materials fabricated by using directly grafting method is not satisfied.In the current work, SAB-15 mesoporous silica was modified with CdS on the inner pore surface by employing layer-by-layer self-assembly and "two-step method". SBA-15 is firstly functionalized with charged polymers onto the inner pore surface through layer-by-layer self-assembly process. Then the precursors of CdS species (Cd (Ac) ₂·2H₂O) were introduced into the functionalized pore surface of SBA-15, through the reaction with pendant -SO₃^2- in polymer. The product was further treated with H₂S to form CdS nanoparticles on the inner pore surface of SBA-15. The nanostructured wurtzite CdS materials distribute uniformly in the channel of the mesoporous host. Compared with traditional "directly grafting" synthetic methodology, the particle size and size distributing of CdS were more effectively controlled by the method we used, which resulted in small particle size about 2 nm,while in the "directly grafting" process, the size of CdS was bigger than 4nm.In Chapter 3, the external surface of SBA-15 was passivated with phenyltrimethoxysilane firstly to prevent the CdS from accumulating on it, and the product was denoted as Ph-SBA-15, then Ph-SBA-15 was functionalized with charged polymers onto the inner pore surface, and CdS nanoparticles was synthesized in the channel of SBA-15. The results of XRD and nitrogen adsorption-desorption measurement indicate that the size of CdS synthesized by this method is more smaller and uniformer.than that of CdS synthesized in Chapter 2.All the samples were characterized by FTIR spectroscopy, UV-vis diffused reflectance spectroscopy, powder X-ray diffraction and nitrogen adsorption-desorption measurement.