title: Dissolution Mechanism of Upconverting AYF4:Yb,Tm (A = Na or K) Nanoparticles in Aqueous Media.
abstract: The dissolution of upconverting AYF4:Yb,Tm (A = Na or K) nanoparticles (UCNPs) in aqueous media was systematically studied. UCNPs with a cubic structure and sizes of between 10 and 33 nm were synthesized solvothermally in ethylene glycol at 200 °C. The UCNPs of both compositions showed an upconversion fluorescence emission characteristic of Tm(3+). The effects of the A cation, the particle size, the temperature, the pH, and the composition of the aqueous medium on the dissolution of the UCNPs were evaluated. The degree of dissolution was determined from the fraction of dissolved fluoride (F(-)) using potentiometry. Unexpectedly, the composition of aqueous media had the most significant effect on the dissolution of the UCNPs. The highest degree of dissolution and rate were measured for the phosphate-buffered saline (PBS), which can be explained by the formation of stable lanthanide compounds with phosphates. The degree of dissolution was much lower in water and in the phthalate buffer, which was attributed to the release of F(-) as a result of the hydrolysis of the UCNPs' surfaces.
authors.affiliation: Department for Materials Synthesis, Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Darja
authors.initials: D
authors.lastname: Lisjak
authors.affiliation: Department for Materials Synthesis, Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.|Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Olivija
authors.initials: O
authors.lastname: Plohl
authors.affiliation: Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.|Department of Environmental Sciences, Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Janja
authors.initials: J
authors.lastname: Vidmar
authors.affiliation: Department of Complex Matter, Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Boris
authors.initials: B
authors.lastname: Majaron
authors.affiliation: Department of Inorganic Chemistry and Technology, Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Ponikvar-Svet