The Self-Catalytic Preparation Of ZnO/SiO₂ And Ag-ZnO/SiO₂ Nanocomposites And Their Functionalization

Among many nano-metal particles, zinc oxide nanopartilces have become a hot research topic. It is a semiconductor with a band gap of 3.752 e V. At room temperature, the machine binding energy of Zn O nanoparticles is 60 me V, with properties very stable under various conditions. From a lot of reports, Zn O nanoparticles are widely applied in the fields of study of photo electronics, catalysis and sensor indication. Zn O nanoparticles have unique properties in optics and photocatalysis, and when the size of Zn O nanoparticles is changed, the luminescence peak will also change. In this paper,we use a new molecular self catalytic method to prepare Zn O/SiO₂ nano composite. Using reactive molecular self catalytic groups, catalytic plus the hydrolysis and condensation of silicon source, the preparation of nanometer zinc oxide precursor body is produced from the hydrolysis of Si-O-Si network system wrapped inside. Finally, Zn O/SiO₂ nanoparticles were prepared by high temperature calcination in situ method. In the synthesis process, the size distribution and morphology of the product can be controlled by changing the position of the catalytic group in the molecule and the addition order and method of the silicon source. The main research work of this paper is as follows.1.β-alanine and zinc oxide were used to prepare beta alanine zinc metal salt in the70 ℃ water bath. Then the TEOS was added to the beta alanine zinc water and ethanol mixed solution. Under the catalytic action of the protonated amino group in the metal salt of zinc, the hydrolysis condensation of SiO₂ was formed by TEOS and the precursor molecule beta alanine zinc was wrapped in it. The organic chain was removed by high temperature in situ method and the Zn O/SiO₂ nanocomposite was formed. The composition and microstructure characterization of Zn O/SiO₂ nanocomposites were characterized by Fourier Transform Infrared Spectroscopy（FT-IR）, Nuclear Magnetic Resonance Spectroscopy（1H-NMR）,Scanning Electron Microscope（SEM）, Transmission Electron Microcopy（TEM）, X-ray Diffraction（XRD）, N2 Adsorption-Desorption Isotherms and Ultraviolet-visible Spectrum（UV-Vis）. It was proved that the Zn O/SiO₂ nano composite material with fluorescence and photocatalytic activity could be successfully synthesized by thecontinuous self catalysis of the catalyst group in the precursor of zinc metal.2. Using zinc oxide and bromine acetic acid at 40℃ water bath, zinc metal organic salt bromine zinc acetate were prepared. Then the mixed silicon source,3-aminopropyl triethoxy silane（APTES） and tetraethyl orthosilicate（TEOS） ethanol solution gradually were added to the acetic acid zinc bromide water and ethanol mixed solution. APTES used amino protonation in its molecular chain as catalytic group, so that Si-O-Si network could be formed by continuous self catalytic hydrolysis and condensation of silicon source. As a result, the precursors of organic salts of zinc acetate in the network were in the interior of the network. Zn O/SiO₂ nanocomposites were obtained by in situ high temperature calcination. By means of the corresponding characterization methods, it is proved that the Zn O/SiO₂ nano composite material with fluorescence and photocatalytic activity can be obtained by molecular self catalysis when the catalytic groups are located in the external source of silicon.3. Improve the catalytic properties of ZnO/SiO₂ nano composite materials, expand the scope of the use of the catalyst. The silver element could be introduced in the APTES molecular chain because of the Br site in the molecular chain of silicon source. The prepared Zn（BA） 2/SiO₂ precursor was soaked in saturated solution of Ag NO3, Centrifugal filtration. After high temperature in situ calcination,Ag-Zn O/SiO₂ bimetallic nanocomposites were obtained. Through a series of characterization methods, it was proved that the bimetallic nanoparticles were successfully prepared, the nanocomposites had good catalytic properties and wide application range.