Stability of Substituted Phenyl Groups Electrochemically Grafted at Carbon Electrode Surface
Bibliographic record
Abstract
The electrochemical reduction of an aryl diazonium tetrafluoroborate salt, dissolved in acetonitrile, at a carbon electrode surface allowed the grafting of aryl groups with the formation of a carbon-carbon bond. Groups such as 4-carboxyphenyl, 4-nitrophenyl, 4-diethylaniline (DEA), and 4-bromophenyl were grafted at a glassy carbon electrode surface. The stability of these grafted groups, present at the glassy carbon electrode surface, was studied at various electrode potentials in aqueous media. In appropriate experimental conditions, the as-grafted groups severely inhibit the cyclic voltammetry response of selected redox probes. Thus, the reappearance and/or increase of an electrochemical response, after polarization, was taken as an indication that a modification of the grafted layer occurred. Our results demonstrated that polarization at very positive (ca. 1.8 V) and negative (ca. -2 V) potentials is needed to observe an electrochemical response. Electrochemical impedance and X-ray photoelectron spectroscopies were also used to investigate the stability of the grafted layers. The impedance data usually tracks fairly well the cyclic voltammetry results, although the former appears to be more sensitive to changes that are occurring upon polarization of the modified electrode. Interestingly, the XPS data indicate clearly that the grafted layer is not always completely removed at the extreme positive and negative potentials investigated. A mechanism was proposed to explain the transformation occurring during polarization of the modified electrode and involves desorption of the substituted aryl groups during the concomitant hydrogen, oxygen, or chlorine evolution and finally leaving close to a covalently bonded monolayer of the grafted species at the electrode surface.
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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 | 0.001 |
| 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 | 0.001 | 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".