Fabrication Of Colloidal Photonic Crystals And Their Applications For Anti-counterfeiting And Temperature Detection

Colloidal photonic crystals(colloidal crystals)have broad application prospects in display,printing,sensing,anti-counterfeiting,solar cells and photocatalysis due to their unique periodic structure,special photonic band gap and structural color.Monodisperse silicon dioxide(SiO₂)and polystyrene colloidal particles are commonly used colloidal assembly elements.However,the lack of function of these colloidal particles seriously limits the application range of colloidal crystals.Therefore,the preparation of monodisperse colloidal particles with new functions and the construction of new responsive colloidal crystals will greatly promote the development and application of responsive colloidal crystals,which has important scientific research value.This thesis is divided into five chapters.Respectively introduced the research background of the colloidal crystal(first chapter),fluorescence SiO₂colloidal crystal preparation and application for anti-counterfeiting(chapter 2),light,water,double the response"SiO₂/polymer"the preparation of colloid crystals and applications for anti-counterfeiting(chapter 3),the SiO₂/ethylene glycol/polymer colloidal crystal gel preparation and temperature detection application(chapter 4).In Chapter 2,a new kind of photo-luminescent photonic crystals(PLPCs)with brilliant PL and structural colors were prepared by the self-assembly of dye-doped silica particles.the conventional photonic crystals(PCs)are usually prepared by the self-assembly of silica or polystyrene particles.However,their applications are limited significantly due to the lack of the functions of the building blocks.The PL and structural colors of PCs can be well-controlled by altering the species of dyes and the size of the particles,respectively.Based on these advantages,PLPC patterns with encrypted information were fabricated through the combination of PLPCs and PCs with similar structural colors but diverse PL colors.These patterns can reversibly hide and display the encrypted information under sunlight and UV illumination,respectively.This work paves a new way for constructing functional PCs and will promote their applications in anti-counterfeiting,smart labels,and optical devices.In Chapter 3,invisible photonic crystal prints(IPCPs)are appealing for anti-counterfeiting and information protection due to their capability in hiding and showing the encrypted information under specific conditions.Herein,the dual-modal IPCPs based on responsive photonic crystals(PCs)with tunable photoluminescent(PL)and structural colors are reported.The responsive PCs are prepared by the self-assembly of dyes doped silica particles into non/swellable polymers.The independent design and control over the optical response of the PL of the particles and structural colors of PCs enable the successful encryption of dual-modal patterns.Under normal conditions,the as-fabricated IPCP shows a fake pattern with uniform structural colors and thus hides the encrypted pattern due to the similar particles size,lattice constant,and refractive index of each region.In striking contrast,PL and structural colors-based new patterns can be instantly and reversibly revealed when the IPCP is exposed to UV illumination or soaked in water.This work provides a new concept in designing and fabricating dual-modal IPCPs,and facilitates their applications in the fields of color display,antifake package,and multilevel anti-counterfeiting.In Chapter 4,the application of traditional colloidal crystal temperature sensor in high temperature environment is difficult.Therefore,we designed and prepared the silica/ethylene glycol/polyethylene glycol methacrylate(SiO₂/PEGMA/EG)colloidal crystal detection test paper by structure design and used it for the detection of high environmental temperature,which Overcome the difficulty of the colloidal crystal temperature sensor in high temperature environment application.After our investigation,it was found that SiO₂/PEGMA/EG colloidal crystal in the process of EG volatilization,lattice spacing became smaller,and reflection wavelength blue shift,and intensity of reflection peak becomes low.The process of EG volatilization was recorded by continuous dynamic spectrum,and the dynamic reflection spectrum pattern of temperature detection was obtained.Using its spectral pattern,the temperature range of 30?-90?can be accurately distinguished within 30 s.