Au–Ag nanoparticles as red pigment in ceramic inks for digital decoration

Novel pigments, consisting of Au–Ag mixed nanoparticles, were developed for digital decoration by ink-jet printing of ceramic wares. Special attention was paid to set up a microwave assisted synthesis route, with a low environmental impact, easily transferable to large-scale production. Several suspensions, based on Au, Ag and Au–Ag mixed nanoparticles were prepared, trying to get a core-shell assemblage, and the synthesis parameters like metal concentration, Ag/Au ratio, time, temperature and chelating agent amount were optimized. The suspensions are stable over many months and a total reaction yield, assessed by ICP-AES analysis, was achieved. Particle size, shape, composition and optical properties were measured by DLS, TEM-EDS, XRD and UV–VIS spectroscopy. The so-prepared inks were applied on ceramic tiles simulating the ceramic process and the colour performance, assessed by colourimetry, were expressed in the CIELab parameters.

► AuAg core-shell nanosuspensions are synthesized by using a microwave assisted route.
► The synthesis is eco-friendly and easily transferable to large scale production.
► Prepared systems are suitable as red inks for digital decoration on ceramic wares.
► Nanosuspensions show high stability, total reaction yield and lots of red shades.
► The chance of reducing Au content in favour of Ag represents a great cost advantage.