Lanthanide-activated SrF nanoparticles with a multishell architecture were investigated as optical thermometers in the biological windows. A ratiometric approach based on the relative changes in the intensities of different lanthanide (Nd and Yb) NIR emissions was applied to investigate the thermometric properties of the nanoparticles. It was found that an appropriate doping with Er ions can increase the thermometric properties of the Nd-Yb coupled systems. In addition, a core containing Yb and Tm can generate light in the visible and UV regions upon near-infrared (NIR) laser excitation at 980 nm. The multishell structure combined with the rational choice of dopants proves to be particularly important to control and enhance the performance of nanoparticles as NIR nanothermometers.
Eu 3+ doped CaF 2 and SrF 2 nanoparticles were synthesized through a facile hydrothermal technique, using citrate ions as capping agents and Na + or K + as charge compensator ions. A proper tuning of the reaction time can modulate the nanoparticle size, from few to several tens of nanometers. Analysis of EXAFS spectra indicate that the Eu 3+ ions enter into the fluorite CaF 2 and SrF 2 structure as substitutional defects on the metal site. Laser site selective spectroscopy demonstrates that the Eu 3+ ions are mainly accommodated in two sites with different symmetries. The relative site distribution for lanthanide ions depends on the nanoparticle size, and higher symmetry Eu 3+ sites are prevalent for bigger nanoparticles. Eu 3+ ions in high symmetry sites present lifetimes of the 5 D 0 level around 27 ms, among the longest lifetimes found in the literature for Eu 3+ activated materials. As a proof of concept of possible use of the Eu 3+ activated alkalineearth fluoride nanoparticles in nanomedicine, the red luminescence generated by two-photon absorption using pulsed laser excitation at 790 nm (in the first biological window) has been detected. The long Eu 3+ lifetimes suggest that the present nanomaterials can be interesting as luminescent probes in time-resolved fluorescence techniques in biomedical imaging (e.g., FLIM) where fast autofluorescence is a drawback to avoid.
Herein, the fabrication of multi‐responsive and hierarchically organized nanomaterial using core‐shell SrF2 upconverting nanoparticles, doped with Yb3+, Tm3+, Nd3+ incorporated into gelatin methacryloyl matrix, is reported. Upon 800 nm excitation, deep monitoring of 3D‐printed constructs is demonstrated. Addition of magnetic self‐assembly of iron oxide nanoparticles within the hydrogel provides anisotropic structuration from the nano‐ to the macro‐scale and magnetic responsiveness permitting remote manipulation. The present study provides a new strategy for the fabrication of a novel highly organized multi‐responsive material using additive manufacturing, which can have important implications in biomedicine.
Chemical approaches, either through vapor or solution routes, are applied to the preparation of tri-doped CaF2-based films for upconversion applications.
Multifunctional HydrogelsIn article number http://doi.wiley.com/10.1002/aisy.201900105, Adolfo Speghini, Tiziano Serra, and co‐workers report the fabrication of a 3D printed multi‐responsive and hierarchically organized material for deep monitoring and remote manipulation. This light and magnetic field responsive hydrogel holds promise for the generation of advanced bionic devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.