Luminescent supraparticles as potential multifunctional sensors

Abstract

Lanthanoid-doped nanoparticles have multiple emerging applications due to unique ultraviolet- and near infrared-excited luminescence, showing tuneable applicability via adapting morphology, dopant composition, and surface functionalisation. However, formation of solids with adjustable emissions according to the excitation wavelength to combine multiple photophysical properties is often a complex synthetic task, demanding repeated epitaxial growth procedures over the surface of the particles. To overcome such difficulties, we propose the elaboration of new methodologies to promote the controlled aggregation of luminescent nanoparticles into structures known as supraparticles. We intend to synthesise submicrometric (200-400 nm) structures based on the combination of rare earth vanadate nanoparticles (40-50 nm) of different compositions. These structures will be able to provide two orthogonal sets of emissions selectively activated according to the excitation wavelength (i.e., 980 nm for YVO4:Yb3+/Tm3+/Ho3+ or 1550 nm for YVO4:Er3+). The relative intensities of the emission sets of the supraparticles will be controlled by adjusting the proportion between the nanoparticle building blocks. Hence, whilst one of the emissions sets can be used for optical monitoring of the local temperature, the second emission set can be used to excite photochemically active dyes anchored at the surface of the supraparticles. Therefore, we intend to obtain multifunctional systems combining thermometry and localised generation of reactive oxygen species, with great potentiality as new tools for photodynamic therapy applications. (AU)