Oxygen sensing properties of room temperature phosphorescent halogenated hexahydroxanthene derivatives
Bibliographic record
Abstract
A series of halogenated hexahydroxanthene (XAN) derivatives, XAN-F, XAN-Cl, XAN-Br, XAN-I, and XAN-5F, were synthesized to investigate their room-temperature phosphorescence (RTP) and optical oxygen-sensing performance. Single-crystal X-ray diffraction revealed that heavier halogens (Br and I) induce nearly orthogonal dihedral angles between the xanthene and phenyl rings (84.87° for XAN-Br and 86.18° for XAN-I), enhancing molecular rigidity and spin–orbit coupling (SOC). This structural configuration promotes efficient intersystem crossing (ISC) and suppresses nonradiative decay, enabling pronounced RTP. In contrast, XAN-Ph without halogen substitution displayed fluorescence, while derivatives bearing lighter halogens (F, Cl, and 5F) exhibited only low-temperature phosphorescence. Thin films of XAN-Br and XAN-I containing 1 wt% Zeonex displayed strong RTP with lifetimes up to 4.48 ms. They also showed exceptional ISC quantum yields (93.02 % for XAN-Br and 93.51 % for XAN-I) and large vacuum-to-air photoluminescence intensity ratios (14.67 and 15.33, respectively). These features translated to excellent oxygen sensitivity, with Stern-Volmer quenching constants (K sv ) of 6.08 × 10 −5 and 1.11 × 10 −4 ppm −1 for XAN-Br and XAN-I, respectively. This high oxygen sensitivity arises from efficient triplet–triplet energy transfer from the XAN's triplet excited state to ground-state triplet oxygen, leading to nonradiative quenching. With their metal-free composition, efficient RTP, excellent oxygen responsiveness, and good solution-processability into thin films, XAN-Br and XAN-I represent promising candidates for use in optical oxygen sensors for biomedical diagnostics, food preservation, and environmental monitoring. • Six halogenated xanthene derivatives are designed for optical oxygen sensing. • XAN-Br and XAN-I films exhibit RTP and strong sensitivity to oxygen. • High Stern–Volmer constant (K sv ) up to 1.11 × 10 −4 ppm −1 is achieved. • Emission color shifts from blue/green to white to enable visual detection. • Simple, metal-free synthesis supports low-cost oxygen sensor development.
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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".