Preparation And Properties Research On ZnO And NiFe₂O₄ Three-dimensional Photonic Crystals

Photonic crystal is a kind of orderly structure in essence,periodically in space by different medium.The special structure endows the photonic crystal materials with many features such as photonic bandgap,photonic local effect,etc.Among them,the photonic band gap character is the basic characteristic which is similar to the band gap in the semiconductor band structure.The electronic photonic band gaps could modulate photons easily.In this thesis,the preparation of polymethyl methacrylate?PMMA?,ZnO opal photonic crystal materials and ZnO,NiFe₂O₄ inverse opal photonic crystal materials were introduced.The influence of the structure on the performance was explored by several characterization methods.The relation of the microstructures and performances were discussed to develop more potential applications of photonic crystal in the future.?1?The monodispersed polymethyl methacrylate?PMMA?microspheres with controllable diameters were prepared by free-soap emulsion polymerization,and then the influencing factors of microsphere synthesis and the structural color generating from PMMA photonic crystals were characterized by XRD,SEM,FT-IR,UV-Vis reflection spectrum.The results indicate that the obtained microsphere is amorphous solid with smooth surface,ranging from 100 nm to350 nm.The particle size of the microsphere is mainly affected by four factors such as the concentration of the methyl methacrylate monomer?MMA?,the amount of the initiator potassium persulfate?KPS?,the reaction temperature and the stirring speed.The microspheres particle size will increase with the increase of monomer content,simultaneously show a trend of decrease after increase with the increase of stirring speed and the quantity of the initiator added.The optimal reaction temperature is 75 oC.Moreover,the structural color shows a proportional redshift trend with the increase of the microspheres diameters.The defects and excessive heating reduce the effective refractive index of thephotonic crystal and then the structural color brightness.?2?ZnO colloidal microspheres with good monodispersity and uniform particle size were prepared by a two-step sol-gel method,and then the influencing factors of particle size and the structural color generating from Zn O photonic crystals were characterized by XRD,SEM,TEM,FT-IR,TG-DSC and UV-Vis reflection spectrum.The results show that the obtained samples are pure wurtzite structure zinc oxide.ZnO microspheres are reunited by zinc oxide particles,ranging from 150 nm to 500 nm.The microsphere surface is slightly rough.The particle size decreases with the increase of the precursor amount.The obtained microspheres containing 30% organic residues,calcination process can result in a slight contraction of the microspheres.The Zn O structural color layers obtained by gravity deposition assembly become thicker with the higher emulsion concentration,but which is more heat-resistant than the structural color layer of PMMA.?3?ZnO material with an inverse opal structure was successful prepared by the template method,using the homemade PMMA photonic crystals as templates and the metal nitrate mixture liquid as precursors.The samples were then characterized by the XRD,SEM,TEM,TG,DRS and the affecting factors of morphology and photocatalytic properties were also discussed.The results show that the obtained samples are pure wurtzite structure zinc oxide.Three factors influence the morphology of the ZnO inverse opal such as precursor concentration,impregnation times and template-removing temperature.Especially,the exorbitant template-removing temperature results in structural collapse.Photocatalytic performance analysis indicates that the inverse opal has ordered connected pore structure and the slow light effect which could improve the utilization rate of light and organic dye transfer efficiency,making the photocatalytic performance better than the ZnO materials pepared under the same reaction conditions.?4?NiFe₂O₄ material with an inverse opal structure was successful prepared by the template method and then XRD,SEM,TEM,VNA were used to characterize the as-prepared samples.The results indicate that the samples are pure spinel structure nickel ferrites.NiFe₂O₄ inverse opal materials have three dimentional ordered pore structure.The smooth wall is made up of NiFe₂O₄ particles with the average size of 27 nm.The pore size is ranging from 70 nm to200 nm.Comparing with the reflection loss value?17.4 d B?of the NiFe₂O₄ particles with the same sample thickness,the NiFe₂O₄ inverse opal materials show more excellent performance with a reflection loss of 27.5 dB.