Preparation And Properties Of Fluorescent Photonic Crystal Film Based On Silica Colloid/Carbon Dots

Since conception of photonic crystal has been created put forward,preparation and application of various kinds of three-dimensional photonic crystals have attracted much attention due to their unique optical properties and potential value in the optical device.Scientists focus on fluorescent photonic crystal because of its photonic band gap and excellent fluorescence properties.The key problem of fluorescent photonic crystal is how to introduce fluorescent substance into photonic crystal.Compared to conventional fluorescent substance such as organic dye and inorganic nanocrystal,carbon dots have been chosen as the fluorescent substance,which have more advantages,including easy operation,good biocompatibility and nontoxicity,photoluminescence stability etc.Herein,carbon dots have been loaded on photonic crystal in three different methods.The prepared fluorescent photonic crystal films have two optical pattern characteristics:structure color and fluorescent properties.The prepared photonic crystal films can not only detect metal ions,but also enhance the efficiency of dye-sensitized solar cells as the back-reflecting layers.The transmission electron microscope,scanning electron microscope,fiber optic spectrometer and fluorescent spectrometer have been used for analyzing the morphology,element and microstructure.The main results are listed as follows:(1).The fluorescent photonic crystal films prepared by hydrothermal-vertical deposition method.The hydrothermal method has been used for synthesizing fluorescent silica/CDs composite colloids,the fluorescent photonic crystal film has been prepared through vertical deposition method.This method shows many advantages,such as easy operation and short preparation time.The prepared photonic film can show brightly color and good fluorescent properties.Compared to the traditional method,carbon dots cover on the silica colloids tightly,which can ensure the fluorescence stability.When Fluorescent photonic crystal films are used as the back-reflecting layers of dye-sensitized solar cells,the open-circuit voltage increases from 0.75 V to 0.77 V,the short-circuit current increase from 7.64 mA/cm~2 to 8 mA/cm~2,the photoelectric conversion efficiency increase from 4.13%to 4.23%.(2).The fluorescent photonic crystal films prepared by calcination-vertical deposition method.The calcination method has been used for preparing silica/carbon dots composite colloids,the fluorescent photonic crystal film has been prepared via vertical deposition method.Carbon dots are synthesized in the microspheres or on the surface of the nanoparticle via calcination,which ensure the fluorescence stability of fluorescent photonic crystal film.The silane coupling agent in composite colloids can be carbonization to form carbon dots,which is evenly distributed into and onto the composite microspheres.The obtained fluorescent photonic crystal films not only show brilliant structural colors,but have good fluorescent properties.While detecting metal ions by fluorescent spectra,the fluorescence attenuation intensity is linearly dependent on the concentration of metal ions Cu(II)ions when the concentration is between 10 nmol/L to 0.1 mol/L.Fluorescent photonic crystal films are used as the back-reflecting layers of dye-sensitized solar cells can lead to the enhancement of short-circuit current(from 7.19 mA/cm~2 to 7.45 mA/cm~2)and the photoelectric conversion efficiency(from 4.13%to 4.21%).(3).The fluorescent photonic crystal films prepared by co-assembly and vertical deposition method.The monodispersed silica colloids and carbon dots have been prepared by st?ber method and hydrothermal method,respectively.The fluorescent photonic crystal films are prepared by co-assembly and vertical deposition method.The obtained fluorescent photonic crystal films not only show brilliant structural colors,but have good fluorescent properties.Compared to the infiltrating methods,this method can improve the distribution of substance and the optical properties,such as structure and fluorescent intensity.The prepared fluorescent photonic crystal film can detect metal ions by two different modes:fluorescence mode and reflection mode.While detecting by fluorescent spectra,the fluorescence attenuation intensity is linearly dependent on the concentration of metal ions when the concentration is between 100 nmol/L to 1 mmol/L,the detection limit is 0.1 nmol/L.While detecting by reflection spectra,the blue shift of reflection peak is linearly dependent on the concentration of metal ions when the concentration is between 1 nmol/L to 100?mol/L.The fluorescent photonic crystal films show good selectivity for detecting Fe(?)ions.Fluorescent photonic crystal which are the back-reflecting layers of dye-sensitized solar cells can enhance the open-circuit voltage from0.67 V to 0.69 V,enhance the short-circuit current from 8.47 mA/cm~2 to 8.91mA/cm~2,enhance the photoelectric conversion from 4.02%to 4.27%.