Effects of single layer graphene and graphene oxide modification on the properties of phthalocyanine blue pigments

Two copper phthalocyanine blue pigments, C.I. Pigment Blue 15 (B) and C.I. Pigment Blue 15:3 (BGS), were modified with Single layer graphene(G) or graphene oxide(GO). The modified pigments were then characterized using FTIR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption isotherms and thermogravimetric analysis. The modifications did not affect the chemical structure of the original pigments but non-covalent interactions between the phthalocyanine pigments and the G (or GO) did form. This greatly reduced aggregation and resulted in more uniform particle size distributions. Modification with both G and GO also resulted in a sharp decreases in the phthalocyanine emission intensities and there were small red-shifts in the absorption peaks. The modification of the pigments also improved their color strengths (116.6-121.4% for B and 106.0-108.8% for BGS), and modification with G improved the color purity. Finally, modification with GO improved the wettability of the original pigments. This is due to the abundant hydroxyl and carboxylic acid groups in graphene oxide.