Modulation Of Far-and Near-field Light By Photonic Crystals Based On SiO₂ And PEGDA-ETPTA

As a major photon control material,not only can photonic crystals(PCs)use the selective reflection of the photonic stop band(PSB)to control the far-field incident light,but also can modulate the spontaneous emission of near-field emitters by the ability of the PSB to redistribute the density of light states.Regarding the regulation of far-field incident light,the researchers use its characteristic of reflecting light with a specific wavelength to in-depth study the structural color-generating properties and applications of PCs;In terms of spontaneous regulation of near-field emitters,composite structures combining PCs with perovskite(PVK)quantum dots(QDs)have attracted extensive attention from researchers in recent years.However,the above-mentioned research still had the following problems:One is that the research on far-field light control is limited to the study of the PSB performance in the reflection direction,while more possibilities of PCs in optical regulation are ignored.The other is that the existing composite structure of PCs and PVK QDs cannot overcome the disadvantage of poor stability of PVK QDs,which limits the possibility of further practical application.In view of the above problems,this paper demonstrated the optical control performance of the transmission/reflection two-way PC in detail,and prepared the structure of PC with transmission/reflection dual mode and double-sided color rendering.Then the composite structure of inverse opal PCs and all-inorganic halide PVK QDs was constructed.It realized the regulation of fluorescence intensity and lifetime,and used a unique ordered structure to greatly enhance the stability of PVK QDs.(1)Using 295 nm SiO₂ spheres as the building bulk,the opal PCs with different ordered layer thicknesses were prepared by the continuous dip-coating.The transmission/reflection optical properties of PCs films with different ordered layer thicknesses were explored and the performance in structural color-generation were investigated.It was found that the reflectivity of PCs could be more than 50%when the thickness of the ordered layer of the PCs were about 5?m.Meanwhile,the transmission peak-to-valley difference ratio was as high as 40%.Due to the appropriate PSB balanced the reflectance and transmittance,this PC film could exhibit excellent optical control capabilities in both reflection/transmission directions,and output beautiful,high-saturation structural colors.Thus,the transmission/reflection two-way structure color films were successfully constructed.On this basis,PCs that assembled on the cylindrical cup successfully simulated the effect of Lycurgus cup interacting with light.When the cup was lit from the front,the cup wall reflected emerald green.And when incident light was incident from the back of the cup,the cup wall transmitted a complementary magenta structural color.Further,in order to overcome the disadvantage that opal PCs can only assembly on the hard matrix to control light,the soft inverse opal PCs films with the ability to control light bi-directionally were also designed and prepared.By changing the interaction way between the film and the light,an effect similar to a dichroic mirror appeared.This optical effect of PCs also provided new potential in the fields of multi-directional banknote anti-counterfeiting and dichroic mirrors.(2)Using the ability of PCs for near-field and far-field luminescence control,the near-field controlled and the far-field controlled composite structures of inverse opal PCs and PVK QDs were designed and constructed to improve the stability and regulate of luminescence of PVK QDs.In the far-field controlled composite structure,the PC was located at the bottom layer,and the PVK QDs were in the upper layer of the polymer.Using the PC as a reflective substrate to reflect the fluorescence of the PVK QDs,the fluorescence intensity of PVK QDs was enhanced by 3.5 times.But this structure did not play a positive role in improving stability.In the near-field controlled composite structure,the PVK QDs were dispersed in the pore structure of the inverse opal.This composite structure used the porous structure of inverse opal to avoid agglomeration and fluorescence quenching of PVK QDs,and the hydrophobicity of the polymer film also prevented the PVK QDs from directly contacting the moisture in the air.Both of effects could greatly improve the stability of the PVK QDs simultaneously.The composite film could be stored stably for four months,and the fluorescence intensity only dropped by 20%.In addition,by designing the fluorescence peak of the PVK QDs to fall exactly at the edge of the blue band of photonic stop band,the fluorescence emission peak intensity was increased by 2.8times and the fluorescence lifetime was shortened to?₁=0.87 ns,due to the redistributed spontaneous emission.Not only did the near-field controlled composite structure improve the stability of PVK QDs,but also manipulate the luminescence of PVK QDs.