Dual mode : thermometry and drug release vehicles based on hollow Y2O3:Er,Yb and Y2O2SO4:Er,Yb spheres

Doping, in general, is a widely used strategy in materials design that entails incorporating atoms or ions into host lattices to achieve desired properties and functions. Rare earth (RE3+) activated phosphors are gaining popularity due to their efficient luminescence, which can be used in cathode ray tubes (CRT), tricolor lamps, white light-emitting diodes (WLEDs), and field emission display (FED) devices, as well as in biomedical applications. In addition, such materials have been studied as potential temperature probes for use in luminescence thermometry. Trivalent erbium (Er3+) is a remarkable ion having upconversion properties due to its ladder-like energy levels, and it has been regarded as one of the most promising RE3+ candidates for luminescence thermometers due to its intense green emissions from thermally coupled 4S3/2 and 2H11/2 emitting levels. Furthermore, the RE3+ ion of choice is frequently combined with Yb3+ ion to benefit from its high absorption cross-section in the NIR, which favors energy transfer-induced upconversion processes to their RE3+ ions. Moreover, some of such phosphors are useful for drug delivery, due to their exceptional properties such as low density, large specific surface area, and good permeability, as well as their high loading capacity and diffusibility for drug molecules. Here we describe the fabrication of Y2O3 hollow spheres doped with Yb3+ and Er3+ ions abide by the sequential templating process accompanying a simple hydrothermal treatment followed by heat treatment. In addition, we demonstrate the preparation of Y2O2SO4 doped with Yb3+ and Er3+ using a simple one-pot hydrothermal method. In this work these two different inorganic hollow phosphors were extensively investigated and showed to have excellent upconversion luminescence properties and could be effectively used as optical temperature sensors in the biological range (288.15 – 333.15 K). Additionally, they could be used for simultaneous drug delivery, employing doxorubicin (DOX) as a model cancer drug.