Isolation of Carboxylic Acid-Protected Au<sub>25</sub> Clusters Using a Borohydride Purification Strategy
Bibliographic record
Abstract
We report the synthesis of 11-mercaptoundecanoic acid (11-MUA) and 16-mercaptohexadecanoic acid (16-MHA) protected Au25 clusters with moderate yields (∼15%) using a NaBH4 purification strategy. UV-vis spectroscopy, transmission electron microscopy (TEM), and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry were employed to study the entire process of the isolation of 11-MUA-protected Au25 clusters from a polydisperse Au cluster solution. UV-vis and TEM data clearly show the formation of a polydisperse mixture, which upon the addition of NaBH4 leads to the growth and precipitation of non-Au25 clusters, leaving the Au25 clusters behind. MALDI MS shows the molecular ion peak for the 11-MUA-protected Au25 cluster. 11-MUA-protected Au25 clusters in THF were purified by slowly increasing the pH of the solution, which leads to the complete deprotonation of carboxyl groups on the surface and eventually precipitation of Au25 clusters. Further protonation of these clusters by acetic acid leads to their solubilization in THF. These results show that, owing to the inherent stability of Au25 clusters, a NaBH4 purification strategy can be used to isolate Au25 clusters with surface carboxylic acid functionalities from a polydisperse Au cluster solution.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 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".