Preparation And Response Properties Study Of 3D Hybrid Colloidal Photonic Crystals

In nature,many fantastic and naturally ordered micro-and nano-structures,such as those found in the wings of Morpho butterflies,peacock feathers,and chameleon skin,have always inspired scientists to mimic them by designing and optimizing material structures.Among them,artificial periodic arrays with tunable optical properties,colloidal photonic crystals,have received much attention.When the wavelength of light modulated by a photonic crystal falls within the visible range,it exhibits bright structural colors.Compared to traditional pigments or dyes based on light absorption,the physically generated structural colors have many advantages,such as resistance to light bleaching and environmental friendliness.Since the optical properties of photonic crystals are modulated by refractive index and lattice constant,they can be hybridized with functional materials to form intelligent materials that respond to external stimuli and dynamically change their structural colors.Therefore,these materials have broad applications in sensing and detection,anti-counterfeiting,printing,and display.With the continuous increase of practical demands,new requirements have been put forward for responsive hybrid colloidal photonic crystals.To meet the needs of different realistic scenarios,finding suitable assembly elements and functional filling materials to increase the types of responsive hybrid colloidal photonic crystals has become an urgent demand for people.This study aims to construct a variety of novel responsive 3D hybrid colloidal photonic in various ways and to conduct in-depth research on their optical properties.Subsequently,their applications in anti-counterfeiting and sensing analysis will be investigated by utilizing their optical properties and the response performance of the filling matrix.The specific contents are as follows:In the second Chapter,we aim to prepare a new type of photonic crystal with tunable optical properties.We first prepare a series of hollow silica（h-SiO₂）with different sizes and shell thicknesses.We then use these particles to construct liquid and gel-based ternary（air,SiO₂,propylene carbonate/resin）non-close-packed photonic crystals and investigate their optical properties.The results show that the optical properties of this ternary non-close-packed photonic crystal can be easily adjusted by varying the h-SiO₂ shell thickness.As the shell thickness of the h-SiO₂ increases from15 nm to 40 nm,the color purity of the photonic crystal structural color can be tuned from 53%to 82%,and the transparency of the photonic crystal film can be tuned from96%to 91%.Due to the existence of cavities and the index matching of the resin and SiO₂,the prepared h-SiO₂ photonic crystal film is highly transparent and can show bright structural colors when it responds to water.Furthermore,a patterned film is obtained using an electric field,and the patterned information is invisible until wetted by water.In the third Chapter,we aim to solve the problem of low structural color saturation of photonic crystals in practical visual observation due to multiple incoherent scattering effects.Herein,by controlling the calcination time of PS@SiO₂nanoparticles,we obtain h-SiO₂ with different in situ generated carbon black contents（C@SiO₂）and assemble them into photonic crystal inks.Photonic crystal inks have excellent saturation and high crystallinity due to the in-situ generated carbon black capable of absorbing incoherently scattered light without affecting particle assembly.Photonic crystal inks are further converted into non-close-packed photonic crystal films with highly saturated structural colors by photopolymerization of resins.This photonic crystal film can be swollen by an ethanol-water mixture,resulting in structural color changes and shifts in reflection peaks.Moreover,the photonic crystal film can dynamically change from a dry opaque state to an ethanol-wetted translucent state.Such solvent-responsive photonic crystal films with highly saturated structural colors are expected to be used in alcohol sensors and color anti-counterfeiting labels.In the fourth Chapter,we aim to develop a new sensor with a low price,simple operation,and simultaneous detection and removal of Hg²⁺.Herein,a cysteamine-functionalized biomimetic chromotropic hydrogel capable of simultaneously naked-eyes detecting and adsorbing Hg²⁺is ingeniously constructed.Benefiting from the specific recognition of Hg²⁺by thiol groups on the hydrogel,the maximum adsorption capacity of the hydrogel is 0.3123 mmol·g^-1 at pH=5.In addition,the adsorption kinetic model and isotherm are consistent with the pseudo-second-order and Langmuir model,respectively,indicating that the adsorption behavior is dominated by monolayer chemisorption.Furthermore,sensitive and selective detection of Hg²⁺（the limit of detection（LOD）is 0.3 n M,3σ）can be easily achieved by observing the color change of the biomimetic chromotropic hydrogel with the naked eye or recording the change in the reflection peak position by a fiber spectrometer.More importantly,Cys-BCH has good regeneration performance and can be applied to detect Hg²⁺in actual water samples.In the fifth Chapter,we aim to design an inverse opal photonic crystal hydrogel microsphere sensor that can rapidly detect H₂O₂ concentration for naked-eye detection.To achieve this goal,we prepare an inverse opal photonic crystal hydrogel microsphere cross-linked by disulfide bonds using microfluidic technology and template replication technology.Subsequently,we use dithiothreitol reduction to break the disulfide bonds in the microspheres,inducing redshift and swelling of the photonic crystal hydrogel microspheres.This process ultimately forms a sensor that responds to H₂O₂.In addition,we construct an H₂O₂/Fe²⁺Fenton reaction solution system to accelerate the sensor response rate significantly.Finally,by optimizing the pH value and temperature of the Fenton system,we develop a sensor capable of rapid naked-eye detection of H₂O₂within the concentration range of 2% to 25%,with good cyclic performance.