A combined theoretical-experimental investigation of paramagnetic centres in chemically exfoliated graphene nanoribbons
Bibliographic record
Abstract
A combined experimental and theoretical study of the origin of paramagnetic centres in graphene nanoribbons (GNRs) is presented. GNRs were prepared from multi-wall carbon nanotubes by an oxidative method at various temperatures. Increasing the oxidation temperature led to GNRs of shorter length with no noticeable effect on the width. Electron spin resonance showed that the ribbon sizes influence both the spin density and type of paramagnetism, with longer ribbons being more prone to form localized paramagnetic centres and shorter ribbons exhibiting a significant paramagnetic contribution from extended states. The density of states for GNRs was calculated with varying dimensions and chiralities using a Hückel tight-binding method. The formation energies of zigzag edges and vacancies, which are expected to be responsible for paramagnetic centres, were evaluated. Our results indicate that longer GNRs favour formation of vacancies while shorter structures favour zigzag edges. This analysis explains the existence of localized paramagnetic centres in longer GNRs and paramagnetism due to electronic states delocalized along zigzag edges in shorter GNRs.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".