Preparation And Properties Of Concentric-layered Magnetic Structural Color Microspheres

Structural color microspheres are angle independent structural materials.They are widely used in sensor,display and other fields.Magnetic particles have many special characters.Combining Structural color microspheres with magnetic particles will improve their value in medical detection,micro-motor and material separation.The existing magnetic photonic crystal microspheres are mostly prepared by self-assemble method.They are often with uneven color,fragile structure and weak magnetism,which limit the application of structural color microspheres.To solve these problems,Al₂O₃ and ZnO films were alternately deposited on the surface of magnetic microspheres by atomic layer deposition?ALD?to prepare concentric-layered structural color microspheres.The microspheres have stable structure,uniform color and strong magnetism.The special properties of ZnO make it possible to achieve multifunctional sensor by the microspheres.Firstly,concentric-layered magnetic structural color microspheres based on thin-film interference were prepared by ALD.Al₂O₃ and ZnO films were deposited on the surface of magnetic microspheres.The ALD cycle number of Al₂O₃ was 400 and the ALD cycle number of ZnO was 800,1000,1100 and 1200.Four kinds of sample with the color of purple,blue,green and yellow were prepared.As the thickness of ZnO lawyer increases,the wavelength of the reflection peak changes from 433 nm to 580 nm.The maximum reflectivity of the sample is 15%.The angle-resolved reflection spectra show that the color of microspheres is angle independent.The microspheres have excellent mechanical stability,their reflection spectra didn't change after solvent soak test,particle erosion test and light aging test.It is because of the atoms in oxide film are connected by stable chemical bonds.The magnetic iron cores bring strong magnetic to the magnetic structural color microspheres.It is possible to achieve assembling and movement under the control of magnetic field.In addition,ZnO is an excellent material for multifunctional sensor.Multifunctional sensor devices were made up of the structural color microspheres.The devices have a sensitive response to temperature,breath,UV,IR and alternating magnetic field due to the photoelectric effect and pyroelectric effect of ZnO.Secondly,magnetic structural color microspheres based on 1-D photonic crystal with better Optical performance were prepared.Al₂O₃ and ZnO films were alternately deposited on the surface of magnetic microspheres to prepare photonic crystal film.The color of the magnetic structural color microspheres is uniform and angle-independent due to its special concentric-layered structure.The maximum reflectivity of the sample is 33%due to the multiple reflections by the several films,much higher than the magnetic structural color microspheres based on thin-film interference.Magnetic structural color microspheres based on 1-D photonic crystal is more suitable for sensor and display due to their excellent optical performance.Stability test,magnetic test and sensing test show that magnetic structural color microspheres based on 1-D photonic crystal also have excellent mechanical stability,Magnetic-movement characteristic and multifunctional sensor performance.The magnetic structural color microsphere can be applied in micro-motor,UV/IR detector and breath monitoring.