Stereostructural Effects in the Electrochemical Properties of Self-Assembled Monolayers
Bibliographic record
Abstract
Large-area metal/molecule/metal junctions based on self-assembled monolayers (SAMs) of organothiolates are of interest for the investigation of charge transport across ultrathin organic films and the fabrication of molecular electronic devices such as diodes and switches. Several reports demonstrate an odd-even dependency in the rate of charge transport across SAMs of the redox-active ferrocenylalkanethiolates Fc(CH2) n S1, 2 and insulating n-alkanethiolates CH3(CH2) n S3-6. This parity effect is attributed to small changes in the orientation of the terminal functional group (ferrocene or methyl) and in the alkyl chain packing in SAMs consisting of an odd versus even number of methylene repeat units (n odd or n even). These odd-even differences ultimately impact device performance. For instance, junctions comprising gold-supported Fc(CH2) n S SAMs (Figure 1) of n even present lower leakage currents and rectify current, while those of n odd do not.1, 2 We have sought experimental evidence for odd-even distinctions in the molecular organization of these SAMs using electrochemistry,7 infrared reflection-absorption spectroscopy (IRRAS), contact angle goniometry, and surface stress measurements8. The findings of these investigations will be presented in this talk. References: 1. Nerngchamnong, N.; Yuan, L.; Qi, D.-C.; Li, J.; Thompson, D.; Nijhuis, C. A., The Role of van der Waals Forces in the Performance of Molecular Diodes. Nat. Nanotechnol. 2013, 8, 113-118. 2. Yuan, L.; Thompson, D.; Cao, L.; Nerngchangnong, N.; Nijhuis, C. A., One Carbon Matters: The Origin and Reversal of Odd–Even Effects in Molecular Diodes with Self-Assembled Monolayers of Ferrocenyl-Alkanethiolates. J. Phys. Chem. C 2015, 119, 17910-17919. 3. Baghbanzadeh, M.; Simeone, F. C.; Bowers, C. M.; Liao, K.-C.; Thuo, M.; Baghbanzadeh, M.; Miller, M. S.; Carmichael, T. B.; Whitesides, G. M., Odd–Even Effects in Charge Transport across n-Alkanethiolate-Based SAMs. J. Am. Chem. Soc. 2014, 136, 16919-16925. 4. Thuo, M. M.; Reus, W. F.; Nijhuis, C. A.; Barber, J. R.; Kim, C.; Schulz, M. D.; Whitesides, G. M., Odd−Even Effects in Charge Transport across Self-Assembled Monolayers. J. Am. Chem. Soc. 2011, 133, 2962-2975. 5. Chen, J.; Giroux, T. J.; Nguyen, Y.; Kadoma, A. A.; Chang, B. S.; VanVeller, B.; Thuo, M. M., Understanding Interface (Odd–Even) Effects in Charge Tunneling using a Polished EGaIn Electrode. Phys. Chem. Chem. Phys. 2018, 20, 4864-4878. 6. Jiang, L.; Sangeeth, C. S. S.; Nijhuis, C. A., The Origin of the Odd–Even Effect in the Tunneling Rates across EGaIn Junctions with Self-Assembled Monolayers (SAMs) of n-Alkanethiolates. J. Am. Chem. Soc. 2015, 137, 10659-10667. 7. Feng, Y.; Dionne, E. R.; Toader, V.; Beaudoin, G.; Badia, A., Odd–Even Effects in Electroactive Self-Assembled Monolayers Investigated by Electrochemical Surface Plasmon Resonance and Impedance Spectroscopy. J. Phys. Chem. C 2017, 121, 24626-24640. 8. Dionne, E. R.; Dip, C.; Toader, V.; Badia, A., Micromechanical Redox Actuation by Self-Assembled Monolayers of Ferrocenylalkanethiolates: Evens Push More Than Odds. J. Am. Chem. Soc. 2018, 140, 10063-10066. Figure 1
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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 | 0.000 | 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".