Abstract
The upconversion (UC) phenomenon is one of the most frequently investigated in lanthanide ions (Ln3+)-doped phosphors. Usually, to obtain UC luminescence, two types of dopants are used: one is a sensitizer, and the other one is an activator, e.g., Yb3+/Er3+. Exceptional UC luminescence can also be presented by systems doped with one type of Ln3+ ions, which are characterized by self-sensitization properties, for instance, Er3+ ions. Herein, the structural and spectroscopic properties of SrF2 nanoparticles (NPs) doped with Er3+ ions in concentration from 2.1 to 29.0% were investigated. The SrF2:Er3+ samples, synthesized using the hydrothermal method, were characterized by the crystalline structure and sizes of their formed NPs below 18 nm. The UC emission under 975 and 1532 nm excitations was observed, wherein the most intense luminescence was registered for SrF2:11.7%Er3+ NPs under 975 nm excitation and for SrF2:4.7%Er3+ NPs under 1532 nm excitation. The UC mechanisms were proposed on the basis of the measured dependencies of integral luminescence intensities on the laser power densities and luminescence lifetimes. The thermometric properties of ratiometric luminescent thermometers based on luminescence intensity ratios (LIRs) from 2H11/2 and 4S3/2 thermally coupled levels in SrF2:Er3+ were evaluated in the 273–373 K temperature range. The interesting temperature dependencies of the UC emission from 4I9/2 and 4I11/2 states were registered; these have not been previously reported.
Highlights
Materials exhibiting the upconversion (UC)phenomenon, which is a conversion of low-energy photons, usually from the near-infrared (NIR) range, to high-energy ones, from the ultraviolet (UV) to the visible range have attracted considerable attention because of the multitude of potential applications.[1]
UC systems based on lanthanide ions (Ln3+) have been the subject of many research studies owing to their unique properties
The unique properties of upconverting Ln3+-doped materials have resulted in the use of these materials in many areas such as solar cells,[3] displays,[4] lasers,[5] pressure or temperature sensors,[6,7] security markers,[8] and fingerprint identification.[9]
Summary
Materials exhibiting the upconversion (UC)phenomenon, which is a conversion of low-energy photons, usually from the near-infrared (NIR) range, to high-energy ones, from the ultraviolet (UV) to the visible (vis) range have attracted considerable attention because of the multitude of potential applications.[1]. Only one report, which presents a system doped with Er3+ ions, characterized by the intense UC luminescence in the NIR region connected with both 4I9/2 → 4I15/2 and the 4I11/2 → 4I15/2 transitions caused by the excitation in the 1450−1650 nm range has been published.[53] It is worth underlining that the intense UC emission of the prepared SrF2:Er3+ NPs appearing in the range of the first biological window can be used in medical applications.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
