Gum Arabic-stabilized upconverting nanoparticles for printing applications

Upconverting nanoparticles (UCNPs) have been proposed for a variety of applications ranging from biomedical probes to luminescent sensors and security tags. Yet, bringing UCNPs into real-life, technologically relevant products requires implementation into industry-friendly processes. The need for stable dispersions, clean films or dry powders challenges users who look for a way to use UCNPs. In this work, an ink formulation was developed that offers a straightforward way to print UCNPs on glass and metallic substrates. The use of Gum Arabic as biocompatible emulsifier allowed to implement the NaGdF₄:Er,Yb/NaGdF₄ core/shell UCNPs into water-based ink formulations without the need of complex surface chemistry. The formulation, based on water, glycerin, and propanediol, exhibited good stability and applicability for printing with a commercial aerosol jet printer. Bright upconversion emission was retained upon printing, and the obtained UCNP films were used in proof-of-concept luminescent thermal sensing.