Fabrication of cobalt aluminate nanopigments by coprecipitation method in threonine waterborne solution

A novel cobalt aluminate (CoAl2O4) nanopigments with bright blue color and good dispersibility was fabricated via a coprecipitation process of threonine. Threonin acts as coordination and structure-directing reagents for the nucleation and assembly of hydroxide precursor, limitation of the CoAl2O4 nanoparticle growth during calcination process, and fine-tuning the molar ratio of Co/Al in final products. The products were characterized with XRD, FESEM, TEM, FTIR, DLS, EDX, ICP-AES and UV-vis. The particle size, colorimetric values and printing ink of CoAl2O4 nanopigments with different amount of threonine and without threonine were investigated. The study exhibited that the CoAl2O4 nanopigments with 0.1-0.2 mol/L threonine showed a smaller size of 10-20 nm, better dispersion and color property than other test samples. The coloration mechanism of the CoAl2O4 nanopigments is also discussed.