Facile Synthesis of Monodispersed SiO₂@Fe₃O₄ Core-Shell Colloids for Printing and Three-Dimensional Coating with...

Amorphous photonic structures (APSs) with short-range ordered arrangement have attracted great interest because of their wide view angles. However, the presented methods for the APSs color printing and 3D coating on different substrates and curvatures are lack of control. Here, APSs with angle-independent structural colors were fabricated by the self-assembly of SiO₂@Fe₃O₄ core-shell nanostructures, which were prepared by the hydrolysis of Fe(acac)₃ on the silica surfaces. The size of SiO₂@Fe₃O₄ core-shell colloids can be controlled well through the tuning of SiO₂ particle size, whereas the coverage of Fe₃O₄ on silica surfaces can be precisely tailored through altering the mass ratio between Fe₃O₄ precursor and SiO₂. APSs with only short-range ordered structures, uniform noniridescent structural colors, and high color visibility can be obtained through the self-assembly of SiO₂@Fe₃O₄ colloids of different particle sizes in a few minutes. They are mainly attributed to the weak electrostatic repulsion interactions between SiO₂@Fe₃O₄ colloids because of the partial coverage of Fe₃O₄ on silica surfaces and absorption of the incoherent multiple scattering of visible light from Fe₃O₄. Moreover, SiO₂@Fe₃O₄ colloids show good adhesion to various substrates, such as paper, glass, plastics, resins, ceramics, and wood, which facilitates the formation of uniform APSs on different substrates. Multicolor prints and 3D coating of APSs on substrates with different curves and roughness can be realized on the basis of the fast assembly of SiO₂@Fe₃O₄ colloids.