Direct Measurement of Surface Termination Groups and Their Connectivity in the 2D MXene V<sub>2</sub>CT<sub><i>x</i></sub> Using NMR Spectroscopy
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
The MXenes are a class of 2D materials composed of transition-metal sheets alternating with carbide/nitride sheets, stacked just a few atoms thick. MXenes discovered thus far also have a surface termination layer that is likely a mixture of hydroxides and fluorides. While reasonable structural models based on X-ray diffraction and transmission electron microscopy data exist, the exact nature and distribution of the surface termination species are not well understood. Here, 1 H, 19 F, and 13 C solid-state NMR spectroscopies are used to investigate the model MXene V 2 CT x, where T signifies the surface termination groups. 1 H NMR experiments provide direct proof of hydroxide moieties in the surface layer by measuring interactions with the MXene surface. Furthermore, 1 H NMR spectroscopy shows a significant amount of water hydrogen bonded to the surface hydroxide layer. 19 F NMR experiments show fluoride moieties bonded to the MXene surface, with extremely unusual 19 F spectra caused by strong interactions with the metallic/semiconducting MXene. 13 C NMR observes the sample from the center of the MXene layer and shows that the 13 C chemical shift is extremely sensitive to the MAX → MXene transformation. Nuclear-spin magnetization transferred from 1 H nuclei in the hydroxide surface termination layer to 13 C nuclei in the center of the MXene sheet yields further evidence of this connectivity. The multinuclear NMR experiments provide direct experimental verification of the structural models and depict the MXene V 2 CT x as infinite sheets of small-bandgap V 2 C sheets terminated by a mixed hydroxide/fluoride layer embedded in a matrix of strongly hydrogen-bonded water molecules.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.004 | 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