Destabilization of PVA-stabilized Ag NPs: color changes at low aqueous concentrations, induced by aggregation and coalescence
Bibliographic record
Abstract
Abstract Aqueous concentrations of poly(vinyl alcohol) (PVA)-stabilized ∼10 nm silver nanoparticles (Ag NPs), in the 1000 ppm concentration range, have been shown to be highly stable at elevated temperatures. However, lower concentrations of these NPs undergo color changes, without precipitation, when heated or when held for extended periods of time at room temperature. We have studied their optical and morphological changes at 80 °C, using UV–vis spectra and TEM, and found that their color, at a concentration of 10 ppm, changes from yellow to claret-red to black without precipitation. Further, the plasmon resonance peak at ∼400 nm diminishes as a new peak develops at ∼550 nm. These changes occur as the previously well-dispersed NPs (yellow color) agglomerate to chains (claret-red color) and, finally, coalesce (black color). We discuss the cause of the instability.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".