Single-molecule sensing of environmental pH--an STM break junction and NEGF-DFT approach.
Angew Chem Int Ed Engl
; 53(4): 1098-102, 2014 Jan 20.
Article
em En
| MEDLINE
| ID: mdl-24339362
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 (≈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.
Texto completo:
1
Base de dados:
MEDLINE
Idioma:
En
Ano de publicação:
2014
Tipo de documento:
Article