Characterization of the Microenvironments of PRODAN Entrapped in Tetraethyl Orthosilicate Derived Glasses
Bibliographic record
Abstract
6-Propionyl-2-(dimethylamino)naphthalene (PRODAN) has been widely used to probe the internal environment of sol−gel derived glasses. It is generally assumed that the entrapped probe reports primarily on the internal solvent environment, through changes in emission wavelength, lifetime, or anisotropy. However, we show that other effects, such as aggregation of the probe and adsorption of the probe onto the silica surface, can also alter the emission properties of PRODAN, providing further information on the evolution of sol−gel derived glasses. Both the steady-state and time-resolved fluorescence properties of PRODAN were examined when the probe was entrapped in tetraethyl orthosilicate (TEOS) derived glasses. The glasses were prepared using a two-step method that is commonly used for protein entrapment, and aged either in air without washing (dry-aged), in air after a washing step (washed), or in buffer (wet-aged). For all aging methods, the changes in the emission properties of the probe were consistent with at least three discrete microenvironments, reflecting free monomers, free aggregates, and adsorbed species (monomers and/or aggregates), the proportion of which changed as a function of drying time and conditions. The monomeric form of the probe underwent a polarity-sensitive emission shift that reflected changes in the internal solvent composition. However, the aggregates/adsorbates contributed unique features to both the steady-state and time-resolved emission properties of PRODAN that gave insights into changes in the solubility of the probe, consistent with loss of internal solvent as aging of the glass proceeded. This study clearly shows that significant new information can be obtained from studies of PRODAN emission, and demonstrates that time-resolved fluorescence measurements are critical to properly elucidate the environment(s) present within the sol−gel derived materials.
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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) | 0.000 | 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 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".