Preparation And Its Optical Sensing Properties Of ZIF-8 Photonic Crystal

Photonic crystal is a new type of optical material that is periodically arranged in space by two or more substances with different dielectric constants.Since their important characteristics of photonic band gap,photonic crystals are widely used in many fields such as photonic crystal sensors,solar cells,displays optical devices and so on.The traditional photonic crystal sensor has the following problems:(1)the introduce of functional materials resulting in poor structural stability;(2)the inability to distinguish between refractive index-like substances;(3)the difficulty in distinguishing between chemically similar substances and the size of molecules.MOFs is a new type of porous material with high specific surface area,large porosity and adjustable pore structure.In this paper,MOFs materials are assembled to photonic crystal sensors,which use the pores of MOFs to realize the choice of molecular size and the differentiation of similar refractive index materials that can not be achieved by traditional photonic crystal sensors.At the same time,they can realize the visual detection of common organic substances.In this work,different shapes of ZIF-8 with uniform size and particle size between 120 nm and 270 nm are prepared by adjusting surfactant CTAB.Next,the assembly conditions are optimized to obtain an optimal assembly process.On the basis of simple drop coating,ZIF-8 is dispersed in a mixed solution of different ratios,and according to the contact angle and the reflection spectrum,the ratio of the best dispersion solution is water:ethanol = 1:1.A layer of PDMS is cured on the glass sheet to enhance the bond between the sample and the substrate.The assembly temperature is optimized to 60°C,and a series of photonic crystals with different structural colors are prepared.Subsequently,the self-built device is used to test the response of the photonic crystal sensor to alkanes,benzenes,alcohol vapors,and the change of photonic crystal reflection peak position and recovery time is obtained.The results show that the reflection peaks of molecules larger than the ZIF-8 channel move below 10 nm,and the reflection peaks caused by molecules that can enter the ZIF-8 channel move above 30 nm.Therefore,the photonic crystal has the ability to distinguish molecules of different sizes.According to the difference in recovery time of the reflection peak position,it is possible to distinguish substances with similar refractive indices.In addition,the photonic crystal sensor enables visual inspection with good cycle stability.In order to study whether other MOFs can also be assembled into photonic crystal,another MOFs material(UiO-66)is synthesized.The effects of acetic acid concentration and raw material concentration on the morphology and particle size of UiO-66 are investigated.The best acetic acid concentration is 2.8 mol/L,and the UiO-66 size decrease as the concentration of the two increase.The assembly process of ZIF-8 successfully assembled UiO-66 into photonic crystal,which broadens the research ideas and application prospects of MOFs photonic crystal.