Photoluminescent inkjet ink containing ZnS:Mn nanoparticles as pigment

Abstract

An inorganic nanoparticle suspension, for use in an inkjet ink, has been prepared using chemically synthesised ZnS:Mn nanoparticles with acrylic acid (AA) as a dispersant. AA was also used as a polymeric binder for the jetted ink, by heat-initiated polymerisation of the AA monomer into solid poly(acrylic acid) (PAA). The AA/ZnS:Mn nanoparticle suspension was mixed with surfactant and two co-solvents to achieve the appropriate rheological properties for jetting. The AA suspension, inks, and jetted films of PAA and ZnS:Mn showed strong orange-red photoluminescence (PL) at 600 nm under ultraviolet laser excitation. The emission colour of the ZnS:Mn nanophosphors was tunable over a wide range of wavelengths by using different excitation wavelengths. The most intense PL was observed for jetted inks containing approximately 0.8 w/w% ZnS:Mn nanoparticles. Addition of a cross-linking agent to the inks significantly improved the mechanical resilience of the polymerised films. All suspensions, inks and films were prepared using simple wet chemical methods and low-temperature processing, making them an inexpensive alternative to semiconductive conjugated polymers and suitable for use on temperature-sensitive substrates, such as polymers and paper.