| Photonic crystal balls (PCBs) are a new kind of responsive photonic crystalmaterials. It can not only solve the disadvantages of photonic crystal films with planarstructure, such as crystal defects, small areas, poormechanical properties, lowthroughput assay, but also haveflexibleoptical orientation and good integration,whichprovides a new thought to design novel, multi-functional responsive optical materials,such as display devices, new sensors and other biological applications and so on.However, thereare stillsome deficiencies, which arenarrowrange of the tunability ofinitial structural colors, bad stability of the ordered crystal structure, the complex andlong-time preparation process to obtain a variety of structural colors. Moreover,thesePCBs are insensitive and low efficiency as some sensors and detections, which limitthe practical applications. To solve above problems, in this paper, we havepreparedFe3O4/PNIPAM multi-responsive magnetically switchable PCBs with wideband-gap range through choosing the long-range repulsion superparamagnetic andPVP modified Fe3O4nanoparticles as the assembly primitives, and have studied theresponsive properties of magnetic field, temperature and solvent. Based on this, wehave prepared (photonic crystal microspheres)/Pt Janus micro-motors by interfacechemical deposition method, and systematically studied the structural control and theinfluence on self-propelled motion properties from the Janus structure.Theas-obtained results are summarized below:(1) The long-range repulsion superparamagnetic and Fe3O4@PVP nanoparticlesare chose as the assembly primitives of ordered crystal structure,we have preparedFe3O4@PVP/PNIPAM PCBs through the facile combination of micro syringe andUV photopolymerization.The Fe3O4/PNIPAMPCBs had different structural colors byregulating the band gap under different external magnetic field. The PCBs showedoptical state with “on”/“off” when the direction of the magnetic field was parallel orperpendicular relative to the vertical incident light. The study on the temperatureresponse of red, yellow, green PCBs indicated that corresponding tunable rang ofband gap successively became wider with the temperature from10oC to35oC. Andthe widest tunable band gap range was90nm.The PCBs showed good sensitivity to the content and composition of alcohol in alcohol and water mixed solvent. Thediffraction peaks of PCBs appeared to mansard change from red shift to blue shift byincreasing alcohol molar concentration. The turning point of ethanol and watersolution was large lower than methanol and water solution. When the methanol molarconcentration changed from10%,50%to80%, in turn, the tunable band gap range ofPCBs were narrower down from88nm,40nm to33nm with the temperatureincreasing from10oC to35oC.(2)The photonic crystal microspheres (PCMSs) were prepared by inverseemulsion method. The emulsion droplets of PCMSs tended to stable with increasingthe surfactant content and the proportion of continuous phase and dispersed phase inturn. The PCMSs sizes decreased with the increase of stirring speed. When thestirring speed increased from150r/min to300r/min, the PCMSs sizes decreased withthe particle size distribution range of3~25m.(3)The Pt/PNIPAM magnetic PCMSs Janus micro-motorswere prepared throughthe Pt deposition on the surface of PCMSs by virtue of interface chemical deposition.For the first time, based on the swelling and shrinkage characteristics oftemperature-responsive PNIPAM gel under different temperature, the structure ofJanus PCMSs could be controlled by regulating the H2PtCl6concentration and thequantity of NaBH4at interface between thePCMSs and NaBH4reduction solution. Thedegree of swelling to shrinking of PNIPAM gel microsphere was larger, the amountof the Pt particles on the PCMSs surface increased. The amount and density of the Ptparticles on the PCMSs surface increased, and the Janus alloplasmic structureappeared obviously with the increase of H2PtCl6concentration. Correspondingly, theself-propelled motion of Janus PCMS was well. |
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