Preparation And Research Of Photonic Crystal Films Based On Solvent Extraction

Photonic crystal has been widely used in photochemistry,color display,and sensors,because of its unique structure and properties.The colloidal self-assembly method to get photonic crystal has attracted great attentions due to its simple operation,economical application,and other advantages.Many methods have been successfully developed to fabricate photonic crystal films,such as gravity sedimentation,vertical deposition,and floating self-assembly.However,it is still a challenge to fabricate smooth photonic crystals films with controllable thickness.This paper proposes a new method for fabricating photonic crystal films based on solvent extraction.Unlike the conventional way,in which water was removed from the colloidal suspension through evaporation,solvent extraction was used to completely remove water from the aqueous dispersion.In order to prepare a uniform photonic crystal film with controllable thickness,a two-substrate device is designed.The research details are as follows:?1?PS photonic crystal films were prepared by solvent extraction with n-octanol as extractant,and the effects of different experimental conditions on the growth rate of photonic crystals were investigated.The results show that the growth rate of photonic crystals increases with the increase of temperature and the concentration of the suspension.The main reason is that the solvent extraction ratio increases with the increase of temperature.It was found that the thicknesses of photonic crystal films can be successfully controlled by adjusting the space between the two substrates.?2?The mechanism of self-assemble of photonic crystal was studied by measuring the spectrum at the interface between the photonic crystal and the colloidal suspension.The results showed that the PS microspheres dispersed in water experienced three states:disorder,non-close-packed colloidal crystal,and close-packed colloidal crystal?photonic crystal?under the driving of solvent convection.In addition,the indicator Rhodamine B was added to the extractant to measure the spectra of different regions of the photonic crystal during the growth process.No absorption peak of Rhodamine B was detected in the photonic crystal during the growth of the crystal,which indicated that the oil-water interface between the PS aqueous suspension and n-octanol always keeps at the bottom of the substrates and it doesn't move upwards with the photonic crystal growing up.?3?SiO₂ photonic crystal films were successfully fabricated by solvent extraction method.The growth rate of the SiO₂ photonic crystal was found to be proportional to the temperature.In addition,it was also found that the photonic bandgap of the photonic crystal has a blue shift after annealing.