Abstract
We present a systematic study on the properties of Na(Y,Gd)F4-based upconverting nanoparticles (UCNP) doped with 18% Yb3+, 2% Tm3+, and the influence of Gd3+ (10–50 mol% Gd3+). UCNP were synthesized via the solvothermal method and had a range of diameters within 13 and 50 nm. Structural and photophysical changes were monitored for the UCNP samples after a 24-month incubation period in dry phase and further redispersion. Structural characterization was performed by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as dynamic light scattering (DLS), and the upconversion luminescence (UCL) studies were executed at various temperatures (from 4 to 295 K) using time-resolved and steady-state spectroscopy. An increase in the hexagonal lattice phase with the increase of Gd3+ content was found, although the cubic phase was prevalent in most samples. The Tm3+-luminescence intensity as well as the Tm3+-luminescence decay times peaked at the Gd3+ concentration of 30 mol%. Although the general upconverting luminescence properties of the nanoparticles were preserved, the 24-month incubation period lead to irreversible agglomeration of the UCNP and changes in luminescence band ratios and lifetimes.
Highlights
Upconverting nanoparticles (UCNP) have the ability to convert multiple absorbed photons with lower energy into light with higher energy (NIR, visible or UV) [1, 2]
Despite the presence of Gd3+, the raw X-ray diffraction (XRD) diffractograms have shown the presence of both phases in all UCNP samples
To separately analyze the content of the two crystal phases, a Parallel Factor Analysis (PARAFAC) deconvolution algorithm was applied to the raw diffractograms [32]
Summary
Upconverting nanoparticles (UCNP) have the ability to convert multiple absorbed photons with lower energy (usually in the NIR range) into light with higher energy (NIR, visible or UV) [1, 2]. Besides the influence of the G d3+ on the photophysical properties, it is frequently used as a contrasting agent for magnetic resonance imaging (MRI) studies [25, 26], doping the UCNP with G d3+ ions offers a possibility for creating multimodal luminescent reporters For such applications, and in general for applications in biosensing, the shelf life of the potential probes becomes a critical issue. Redispersing them in an organic solvent in combination with a subsequent phase transfer to water, such a storage layout could be an alternative strategy to facilitate an economically required longer shelf life of UCNP Taking this into account, we decided to study the effect of various doping concentrations of Gd3+ as well as dry storage over a long period of time on the photophysical properties of Na(Y,Gd)F4:Yb3+,Tm3+ UCNP. A comparison of structural and photophysical properties of oleatecapped Na(Y,Gd)F4:Yb3+,Tm3+ right after synthesis and after 24 months of dry storage has been performed as well
Sign-in/Register to view highlights & summary 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.
