Study On Preparation And Properties Of Super Paramagnetic Functional Molecules

The purpose of this paper is the preparation of a kind of functional molecules with superparamagnetism and analyze the coloring properties of the dispersions containing the functional molecules. Under the induction of the external magnetic field, the functional molecules dispersed in the solvent will automatically assemble into orderly photonic crystal structure which can present specific structural color. The samples prepared in this paper achieve the regulation of blue to red in the visible light range.The functional molecules are made by high temperature hydrolysis reaction. The polymer surfactants polyacrylic acid(PAA) are added into the reactants to improve the dispersion properties of the molecules. Under a high temperature alkaline environment, the ferric iron ion(Fe3+) are hydrolyzed and part of them are reduced. Eventually, the magnetic nanospheres are formed through the dehydration reaction. The silicon magnetic functional molecules with stable performance are obtained by the classic Stober Method in alkaline conditions. In the aspect of theoretical analysis, the structure generated by the magnetic assembly is modeled and set four structural parameters: the spherical radius R, the interplanar spacing M, the spherical pitch F on the same crystal face and the number of crystal planes C. The influence of every structural parameter to the crystal structure is analyzed by finite difference time domain method (FDTD). Characterization results show that the products is superparamagnetic, spherical and good dispersion in aqueous solution.The prepared products dispersed in water and not modified with silicon have low reflectivity about 8%. Their performance is not stable. The color rendering performance will be lost in 4 days. The products modified by silicon have a high color rendering property and the reflectivity can reach up to 30%. In addition, the products modified by silicon have more stable performance, which can be stored in more than 90 days and will not be changed over time. Meanwhile, spectrum control is reversible .With the increase of light intensity and the change of illumination angle, the diffraction of light will be changed and show anisotropy. Theoretical study shows the ideal color parameter combination of the structure through FDTD analysis, and also reveal that the change of the spectral reflectivity caused by the interplanar spacing M is consistent with the change of the magnitude of the external magnetic field in the experiment, which show that changing magnitude of the magnetic field actually change spacing of the nano functional molecules to present the diffraction phenomenon of different colors. At the same time, the other three structural parameters also have regular impact on structural color rendering. The nano functional molecules studied in this paper have important application prospect in optical anti-counterfeiting, dye, temperature sensor, humidity sensor, decoration and other fields.