Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume 53, Issue 4, Pages 1098-1102Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201308398
Keywords
density functional calculations; dyes; pigments; molecular electronics; pH sensors; sensing; single-molecule devices
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Funding
- National Science Foundation [CHE 0809838, CHE-1058896]
- FRQNT
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1058896] Funding Source: National Science Foundation
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Sensors play a significant role in the detection of toxic species and explosives, and in the remote control of chemical processes. In this work, we report a single-molecule-based pH switch/sensor that exploits the sensitivity of dye molecules to environmental pH to build metal-molecule-metal (m-M-m) devices using the scanning tunneling microscopy (STM) break junction technique. Dyes undergo pH-induced electronic modulation due to reversible structural transformation between a conjugated and a nonconjugated form, resulting in a change in the HOMO-LUMO gap. The dye-mediated m-M-m devices react to environmental pH with a high on/off ratio (approximate to 100:1) of device conductivity. Density functional theory (DFT) calculations, carried out under the non-equilibrium Green's function (NEGF) framework, model charge transport through these molecules in the two possible forms and confirm that the HOMO-LUMO gap of dyes is nearly twice as large in the nonconjugated form as in the conjugated form.
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