Oxygen sensing properties of room temperature phosphorescent halogenated hexahydroxanthene derivatives
Why this work is in the frame
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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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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) | 0.000 | 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 it