Single Er3+, Yb3+: KGd3F10 Nanoparticles for Nanothermometry

Abstract

Among several optical non-contact thermometry methods, luminescence thermometry is the most versatile approach. Lanthanide-based luminescence nanothermometers may exploit not only downshifting, but also upconversion (UC) mechanisms. UC-based nanothermometers are interesting for biological applications: they efficiently convert near-infrared radiation to visible light, allowing local temperatures to be determined through spectroscopic investigation. Here, we have synthesized highly crystalline Er3+, Yb3+ co-doped upconverting KGd3F10 nanoparticles (NPs) by the EDTA-assisted hydrothermal method. We characterized the structure and morphology of the obtained NPs by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and dynamic light scattering. Nonlinear spectroscopic studies with the Er3+, Yb3+: KGd3F10 powder showed intense green and red emissions under excitation at 980 and 1,550 nm. Two- and three-photon processes were attributed to the UC mechanisms under excitation at 980 and 1,550 nm. Strong NIR emission centered at 1,530 nm occurred under low 980-nm power densities. Single NPs presented strong green and red emissions under continuous wave excitation at 975.5 nm, so we evaluated their use as primary nanothermometers by employing the Luminescence Intensity Ratio technique. We determined the temperature felt by the dried NPs by integrating the intensity ratio between the thermally coupled 2H11/2→4I15/2 and 4S3/2→4I15/2 levels of Er3+ ions in the colloidal phase and at the single NP level. The best thermal sensitivity of a single Er3+, Yb3+: KGd3F10 NP was 1.17% at the single NP level for the dry state at 300 K, indicating potential application of this material as accurate nanothermometer in the thermal range of biological interest. To the best of our knowledge, this is the first promising thermometry based on single KGd3F10 particles, with potential use as biomarkers in the NIR-II region.

Er3+-Yb3+ co-doped nanoparticles as contrast agents for near infrared biomedical photoacoustic imaging application

“…In Figures 5(a) and (b) one can see the results for the core NP at two different wavelengths: 980 nm, which excites more efficiently the Yb 3+ ion and, by energy transfer, excites the Er 3+ ion (see refs. 2,14 ); 520 nm directly excites the Er 3+ ion, as can be seen in the simplified diagram energy of Figure 6. The obtained PA signal is one order of magnitude more intense at 520 nm at lower fluence and even at lower concentration (7.5 mg/ml) compared to excitation at 980 nm and higher concentration (15 mg/ml).…”

“…Synthesis of core-shell systems 5% Er 3+ , 20% Yb 3+ co-doped KGd3F10 cores were prepared by an ethylenediaminetetraacetic acid (EDTA)-assisted hydrothermal synthesis as well described by de Oliveira Lima et al 14 . First, the core@shell Er 3+ , Yb 3+ : KGd3F10@SiO2 particles were prepared through Stöber method 15 , dispersing 50 mg of Er 3+ , Yb 3+ : KGd3F10 cores in 35 mL of anhydrous ethanol (≤0.005% H2O -Synth) and kept in ultrasonic bath for 30 minutes.…”

“…We have used the 5% Er 3+ , 20% Yb 3+ co-doped KGd3F10 particles prepared, studied and reported from de Oliveira Lima et al 14 . Figure 1 shows the XRD patterns of Er 3+ , Yb 3+ co-doped KGd3F10 cores and Er 3+ , Yb 3+ : KGd3F10@SiO2 coreshell samples.…”

2D Thermal Maps Using Hyperspectral Scanning of Single Upconverting Microcrystals: Experimental Artifacts and Image Processing

“…Also, because transistors and several other electronic devices are reaching dimensions of just a few nanometers, thermometers at the nanoscale can be used to detect several failure mechanisms, such as fabrication defects or short circuits . In the recent literature, lanthanide (Ln 3+ )-doped materials are among the most promising candidates for contactless temperature sensors at the micro- and nanoscale over a wide temperature range. ,− Ln 3+ -doped materials often combine high accuracy, high photostability, and low toxicity, allowing high spatial and thermal resolutions when performing temperature sensing at the single-particle level. , It is worth noting that, besides nanothermometry, there is a broad range of other relevant applications that require understanding and exploiting the properties of Ln 3+ -doped materials. Some remarkable examples include solar energy conversion, super-resolution microscopy, quantum computing, fingerprint imaging, and biological applications …”

“…1,4−6 Ln 3+ -doped materials often combine high accuracy, high photostability, and low toxicity, 7 allowing high spatial and thermal resolutions when performing temperature sensing at the single-particle level. 8,9 It is worth noting that, besides nanothermometry, there is a broad range of other relevant applications that require understanding and exploiting the properties of Ln 3+ -doped materials. Some remarkable examples include solar energy conversion, 10 super-resolution microscopy, 11 quantum computing, 12 fingerprint imaging, 13 and biological applications.…”