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Length-dependent conductance of oligothiophenes.

Length-dependent conductance of oligothiophenes.

Journal of the American Chemical Society (2014-07-09)

Brian Capozzi, Emma J Dell, Timothy C Berkelbach, David R Reichman, Latha Venkataraman, Luis M Campos

ABSTRACT

We have measured the single-molecule conductance of a family of oligothiophenes comprising 1-6 thiophene moieties terminated with methyl-sulfide linkers using the scanning tunneling microscope-based break-junction technique. We find an anomalous behavior: the peak of the conductance histogram distribution does not follow a clear exponential decay with increasing number of thiophene units in the chain. The electronic properties of the materials were characterized by optical spectroscopy and electrochemistry to gain an understanding of the factors affecting the conductance of these molecules. We postulate that different conformers in the junction are a contributing factor to the anomalous trend in the observed conductance as a function of molecule length.

MATERIALS

Product Number

Brand

Product Description

Sigma-Aldrich

3-Hexylthiophene, ≥99%

Sigma-Aldrich

Triethylamine, BioUltra, ≥99.5% (GC)

Sigma-Aldrich

Triethylamine, for protein sequence analysis, ampule, ≥99.5% (GC)

Sigma-Aldrich

2,2′-Bithiophene, 99%

Sigma-Aldrich

Triethylamine, for amino acid analysis, ≥99.5% (GC)

Sigma-Aldrich

Triethylamine, puriss. p.a., ≥99.5% (GC)

Sigma-Aldrich

Triethylamine, ≥99.5%

Sigma-Aldrich

Triethylamine, ≥99%

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Triethylamine, ≥99.5%

Supelco

Triethylamine, analytical standard

Sigma-Aldrich

Thiophene, ≥99%

Sigma-Aldrich

Potassium carbonate, 99.995% trace metals basis

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Potassium carbonate, BioUltra, anhydrous, ≥99.0% (T)

Sigma-Aldrich

2,2′:5′,2′′-Terthiophene, 99%

Supelco

Thiophene, analytical standard

Sigma-Aldrich

Potassium carbonate, meets USP testing specifications

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Potassium carbonate, anhydrous, free-flowing, Redi-Dri^™, ReagentPlus^®, 99%

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Potassium carbonate, BioXtra, ≥99.0%

Sigma-Aldrich

Potassium carbonate, anhydrous, powder, 99.99% trace metals basis

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Potassium carbonate, ReagentPlus^®, 99%

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Potassium carbonate, anhydrous, free-flowing, −325 mesh, Redi-Dri^™, reagent grade, ≥98%

Sigma-Aldrich

Potassium carbonate, meets analytical specification of Ph. Helv., puriss., anhydrous, granulated, 99-101% (calc. to the dried substance)

Sigma-Aldrich

Potassium carbonate, puriss. p.a., ACS reagent, anhydrous, ≥99.0% (T)

Sigma-Aldrich

Potassium carbonate, anhydrous, free-flowing, Redi-Dri^™, ACS reagent, ≥99%

Sigma-Aldrich

Potassium carbonate, ACS reagent, ≥99.0%

Sigma-Aldrich

Potassium carbonate, reagent grade, ≥98%, powder, −325 mesh