Probing the Structure of NaYF<sub>4</sub> Nanocrystals using Synchrotron-Based Energy-Dependent X-ray Photoelectron Spectroscopy
Bibliographic record
Abstract
Understanding the structure and chemical speciation of the synthesized lanthanide-doped NaYF 4 nanocrystals is of paramount importance to improve and optimize their physical and chemical properties. Hence in this work we employ synchrotron-based high-resolution X-ray photoelectron spectroscopy (XPS) measurements to analyze lanthanide-doped and undoped NaYF 4 nanocrystals. These measurements revealed that there are two doublets for the yttrium ions in the nanocrystal instead of the single doublet in case all Y 3+ ions have the same chemical environment, generally observed around a binding energy of 160 eV (3d photoelectrons of Y 3+ ). This second doublet (binding energy ∼ 157.5 eV) was convoluted with the first doublet (binding energy ∼ 160 eV), and the intensity of this doublet increased with a decrease in excitation X-ray energy. The second doublet was confirmed to belong to the yttrium ions as doped and undoped NaYF 4 nanocrystals exhibit this second peak. The peaks were deconvoluted showing that the second peak is also a doublet with the ratio of the peaks being 2:3. This is exactly the same as what we have observed for the first doublet of the 3d photoelectrons of yttrium ions. In addition, we observe an increase in intensity of the second doublet in comparison to the original 3d doublet of the yttrium ions as the excitation energy is decreased. This suggests that the second doublet is from surface yttrium ions in the NaYF 4 nanocrystal. To confirm our hypothesis, a shell of NaYbF 4 or NaTmF 4 was grown over the NaYF 4 nanocrystal and the second doublet for the yttrium ions was not observed. This is an additional confirmation that the second doublet is indeed from the surface yttrium ions. This implies that the yttriums on the surface of the nanocrystals have a (slightly) different chemical speciation than their counterparts inside the nanocrystals. We attribute the new chemical speciation of surface yttrium ions to the different chemical environment they encounter than their counterparts inside the nanocrystal.
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How this classification was reachedexpand
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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".