Cation Exchange: A Facile Method To Make NaYF<sub>4</sub>:Yb,Tm-NaGdF<sub>4</sub> Core–Shell Nanoparticles with a Thin, Tunable, and Uniform Shell
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Bibliographic record
Abstract
Cation exchange was performed on up-conversion NaYF 4:Yb,Tm nanoparticles, resulting in NaYF 4:Yb,Tm-NaGdF 4 core–shell nanoparticles as indicated by electron energy-loss spectroscopy 2D mapping. Results show that core–shell nanoparticles with a thin, tunable, and uniform shell of subnanometer thickness can be made via this cation exchange process. The resulting NaYF 4:Yb,Tm-NaGdF 4 core–shell nanoparticles have an enhanced up-conversion intensity relative to the initial core nanoparticles. As potential magnetic resonance imaging (MRI) contrast agents, they were tested for their proton relaxivities. The r 1 relaxivity per Gd 3+ ion of the nanoparticles with a thin NaGdF 4 shell (ca. 0.6 nm thick) measured at 9.4 T was found to be 2.33 mM –1 ·s –1 . This r 1 relaxivity is among the highest in all the reported NaYF 4 –NaGdF 4 core–shell nanoparticles. The r 1 relaxivity per nanoparticle is 1.56 × 10 4 mM –1 ·s –1, which is over 4000 times higher than commercial Gd 3+ -complexes. The very high proton relaxivity per nanoparticle is critical for targeted MRI as such nanoparticles provide strong contrast even in low concentrations. The presented cation exchange method is a promising way to manufacture core–shell nanoparticles with up-conversion NaYF 4:Yb,Tm core and paramagnetic NaGdF 4 shell for bimodal imaging, i.e. MR and optical imaging.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it