Locating the bandgap edges of eumelanin thin films for applications in organic electronics
Bibliographic record
Abstract
Abstract BACKGROUND Bio‐sourced (natural) organic materials are often chemically and structurally disordered, such that their structure‐property relationships must be explored using model systems. Eumelanin is an interesting candidate among natural organic materials. RESULTS In this work, the locations of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of 5,6‐dihydroxyindole (DHI) and 5,6‐dihydroxyindole‐2‐carboxylic acid (DHICA) building blocks (monomers) of the black‐brown biopigment eumelanin, in film form, are studied. The films are fabricated by the spin‐coating technique (i.e., here indicated as DHI‐ and DHICA‐films), which is sometimes followed by ammonia‐induced solid‐state polymerization (i.e., indicated as AISSP‐DHI and AISSP‐DHICA films), as well as by thermal evaporation (i.e., evaporated DHI and DHICA films). From Ultraviolet photoemission spectroscopy (UPS), we deduced the ionization energies (EI) for all DHI‐ and DHICA‐based films to be in the range of 5.34‐5.56 eV and 5.35‐5.80 eV, respectively. The electron affinities (χE) are measurable using inverse photoemission spectroscopy (IPES) for DHI films (3.80 eV) and both evaporated DHI (4.0 eV) and DHICA (3.9 eV) films. On the other hand, the χE values of DHICA, AISSP‐DHI, and AISSP‐DHICA films are estimated with about 0.5 eV of uncertainty. UV‐visible spectroscopy reveals the preferred chromophoric bands for DHICA, AISSP‐DHICA, and DHI are in the range of 300‐330 nm, while AISSP‐DHI exhibits a broadened UV‐visible absorbance. CONCLUSION Our study paves the way for the design of suitable metal‐eumelanin interfaces for electronic applications. © 2021 Society of Chemical Industry (SCI).
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".