Fabrication And Mechanism Of Responsive Photonic Crystals With Fluorescent Properties

Photonic crystals(PCs)are a kind of materials with periodic structure,which possess photonic band gap(PBG)and structural color.With external stimuli,PBG of responsive PCs could shift and it causes the change of structural color.Based on this special property,responsive PCs have broad application prospects.In recent years,many researchers devote themselves to the research of fluorescence technology and make it have a wide range of applications in the fields of sensors,environmental monitoring,fluorescent marking,anti-counterfeiting,full-color display and information storage.Now,there are many reports about the PCs with combination of fluorescent materials,which not only have the structural color but also have the fluorescence characteristics.These new materials could expand the signal expression ability of PCs in other fields.However,there are few researches about responsive fluorescent photonic crystals assembled of polymer spheres.Therefore,we fabricated a series of responsive PCs with fluorescence characteristics assembled with polymer spheres and investigated the tuning mechanisms.The main researches are as follows:1.Photosensitive monomers with carbamate groups that response to 254 nm ultraviolet(UV)light and with spiropyran groups that response to 365 nm UV light were designed and prepared.And their optical properties were studied.Then,two kinds of photosensitive monomers were grafted to the shell of polymer spheres to form the reactive core-shell colloidal spheres,respectively.2.We fabricated PCs assembled with core-shell colloidal spheres modified by photosensitive monomers with carbamate groups via the vertical deposition method,spray coating and roll printing.The influence factors of assembling PCs were investigated and the optimum assembly conditions were confirmed.Furthermore,we study the optical properties of PCs.The relationship between photonic band gap and fluorescence intensity was explored,and fluorescence enhancement mechanism of PCs was investigated.The fluorescence enhancement of PCs was attributed to most overlapping between emission band and photonic band gap.3.A series of photonic crystal fluorescent arrays and dual mode display materials with three primary colors were fabricated based on PCs that response to 254 nm UV light.Herein,fluorescent arrays were obtained through local exposure on the PCs covered with mask,which were assembled by the vertical deposition method.Two dimentional(2D)multi-color patterns assembled from core-shell colloidal spheres with different diameters were obtained through selective spray coating on the glass and paper substrates.Colloidal spheres with different diameters were ejected towards three dimentional(3D)temples fabricated by a 3D-printer,and 3D multi-color patterns were obtained.These photonic crystal patterns not only have structural colors under visible light but also exhibit fluorescence after UV irradiation and chemical treatment.This is because the photosensitive monomers restricted in the shell were photo-decomposed to produce amino groups with UV irradiation and exhibit fluorescence after fluorescamine treatment.4.We prepared inverse opal films with specific response modified by the photosensitive monomers with carbamate group,and their responsive mechanisms were investigated.With UV irradiation,the carbamate groups in the inverse opal were decomposition and the hydrophilic amino groups were generated.Thus,the lattice spacing and refractive index of inverse opal changed,and the photonic band gap occurred red shift.Based on the humidity responsive characteristics of inverse opal films,we fabricated inverse opal patterns through local exposure.With UV irradiation,the inverse opal films in the exposure field were photo-decomposed,and the hydrophilic amino groups were generated.The photonic band gap occurred red shift after vapour treatment.However,the photonic band gap of the inverse opal films in the other field had no shift after vapour treatment.Thus,the patterns were fabricated.When the films became dry,the patterens disappeared.5.Reversible light-and electrothermal-responsive photonic crystal devices were prepared on the glass and paper substrate based on PCs that response to 365 nm UV light and the patterned graphite layer.After UV irradiation,the photosensitive monomer restricted in the shell of spheres had a ring-opened reaction and exhibit fluorescence.After applying the voltage in the local area,PCs had a ring-closed reaction and the fluorescence disappeared due to the increasing temperature.However,the PCs in the area without applying the voltage still exhibit fluorescence.Then the fluorescent patterns were formed.When the voltage was switched off,the PCs exhibit fluorescence after UV irradiation due to the ring-opened reaction of the photosensitive monomer restricted in the shell of spheres,and the fluorescent patterns disappeared.Herein,it has a dynamic display effect based on the reversible light and electrical response of the photonic crystal device.