A Facile Synthesis and Characterization of Monodisperse Spherical Pigment Particles with a Core/Shell Structure

In this paper, a facile sol–gel process for producing monodisperse, spherical, and nonaggregated pigment particles with a core/shell structure is reported. Spherical silica particles (245 and 385 nm in diameter) and Cr 2 O 3 , α‐Fe 2 O 3 , ZnCo 2 O 4 , CuFeCrO 4 , MgFe 2 O 4 , and CoAl 2 O 4 pigments are selected as cores and shells, respectively. The obtained core/shell‐structured pigment samples, denoted as SiO 2 @Cr 2 O 3 (green), SiO 2 @α‐Fe 2 O 3 (red), SiO 2 @MgFe 2 O 4 (brown), SiO 2 @ZnCo 2 O 4 (dark green), SiO 2 @CoAl 2 O 4 (blue), and SiO 2 @CuFeCrO 4 (black), are well characterized by using X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and UV‐vis diffuse reflection, as well as by investigating the magnetic properties. The results of XRD and high‐resolution TEM (HRTEM) demonstrate that the pigment shells crystallize well on the surface of SiO 2 particles. The thickness of the pigment shell can be tuned by the number of coatings, to some extent. These pigment particles can be well dispersed in some solvents (such as glycol) to form relatively more stable suspensions than the commercial products. Apart from the color characteristics, some of pigments like SiO 2 @Cr 2 O 3 , SiO 2 @MgFe 2 O 4 , and SiO 2 @CuFeCrO 4 also show magnetic properties with coercivities of 1098 Oe (5 K), 648 Oe (5 K), and 91 Oe (298 K), respectively.