title: Optically Detected Degradation of NaYF4:Yb,Tm-Based Upconversion Nanoparticles in Phosphate Buffered Saline Solution.
abstract: In a proof-of-concept study, we assessed different analytical and spectroscopic parameters for stability screening of differently sized β-NaYF4:20 mol % Yb3+, 2 mol % Tm3+upconversion nanoparticles (UCNPs) exemplarily in the bioanalytically relevant buffer phosphate buffered saline (PBS; pH 7.4) at 37 and 50 °C. This included the potentiometric determination of the amount of released fluoride ions, surface analysis with X-ray photoelectron spectroscopy (XPS), and steady-state and time-resolved fluorescence measurements. Based on these results, the luminescence lifetime of the 800 nm upconversion emission was identified as an optimum parameter for stability screening of UCNPs and changes in particle surface chemistry.
authors.affiliation: 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: Division 1.10 Biophotonics, Federal Institute of Materials Research and Testing (BAM) , 12489 Berlin, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Kraft
authors.affiliation: Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Kovač
authors.affiliation: Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.|Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Blaž
authors.initials: B
authors.lastname: Belec
authors.affiliation: Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Ponikvar-Svet
authors.affiliation: Division 1.10 Biophotonics, Federal Institute of Materials Research and Testing (BAM) , 12489 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Würth
authors.affiliation: Jožef Stefan Institute , Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Darja
authors.identifier: 0000-0003-4154-4592
authors.initials: D
authors.lastname: Lisjak
authors.affiliation: Division 1.10 Biophotonics, Federal Institute of Materials Research and Testing (BAM) , 12489 Berlin, Germany.
authors.forename: Ute
authors.identifier: 0000-0002-0944-1115
authors.initials: U
authors.lastname: Resch-Genger