Transistor Effects and In Situ STM of Redox Molecules at Room Temperature

Albrecht, Tim; Guckian, Adrian; Ulstrup, Jens; Vos, Johannes G.

doi:10.1109/tnano.2005.851280

Cited by 44 publications

(69 citation statements)

References 22 publications

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“…Albrecht et al [13,[15][16][17] ET > 10 6 s −1 and feature electrochemical STM enhancement with a maximum above the off resonance tunneling current and a peak potential that depends on the electrochemical overpotential, η = E S − E 0 ′ and tip-substrate bias, E bias , with a width of 200-300 mV from confined space in the nano-gap between substrate and tip. Also, a systematic linear variation of peak potential in the tunneling current over potential curve with E bias has been observed [35].…”

Section: Et In Electrochemical Experimentsmentioning

confidence: 99%

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Electrochemical gating of single osmium molecules tethered to Au surfaces

Herrera

Adam

Ricci

et al. 2015

J Solid State Electrochem

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The electrochemical study of electron transport between Au electrodes and the redox molecule Os[(bpy) 2 (PyCH 2 NH 2 CO-]ClO 4 tethered to molecular linkers of different length (1.3 to 2.9 nm) to Au surfaces has shown an exponential decay of the rate constant k ET 0 with a slope β = 0.53 consistent with through bond tunneling to the redox center. Electrochemical gating of single osmium molecules in an asymmetric tunneling nano-gap between a Au(111) substrate electrode modified with the redox molecules and a Pt-Ir tip of a scanning tunneling microscope was achieved by independent control of the reference electrode potential in the electrolyte, E ref − E s , and the tipsubstrate bias potential, E bias . Enhanced tunneling current at the osmium complex redox potential was observed as compared to the off resonance set point tunneling current with a linear dependence of the overpotential at maximum current vs. the E bias . This corresponds to a sequential two-step electron transfer with partial vibration relaxation from the substrate Au(111) to the redox molecule in the nano-gap and from this redox state to the Pt-Ir tip according to the model of Kuznetsov and Ulstrup (J Phys Chem A 104: 11531, 2000). Comparison of short and long linkers of the osmium complex has shown the same two-step ET (electron transfer) behavior due to the long time scale in the complete reduction-oxidation cycle in the electrochemical tunneling spectroscopy (EC-STS) experiment as compared to the time constants for electron transfer for all linker distances, k ET 0 .

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Section: Et In Electrochemical Experimentsmentioning

confidence: 99%

“…In situ electrochemical metal/molecule/metal scanning tunneling spectroscopy (EC-STS) of redox active molecules has been reported by the groups of Ulstrup [13][14][15][16][17] …”

Section: Introductionmentioning

confidence: 99%

Electrochemical gating of single osmium molecules tethered to Au surfaces

Herrera

Adam

Ricci

et al. 2015

J Solid State Electrochem

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“…In the electrochemical scanning tunneling spectroscopy configuration (i.e., STM tip not chemically attached to the molecule) there is now a collection of examples displaying a clear maximum in their tunneling current (I tunneling ) vs electrochemical potential relations. 13,15,[23][24][25][26][27]29,39 These have been well-modeled in terms of the KU relationship for two-step electron/hole transfer through the redox center in the STM−substrate gap. The situation is far from clear for measurements made in the in situ electrochemically gated BJ configuration (i.e., when the electrochemically active bridge molecule is chemically attached at one end to the STM tip and at the other end to the substrate).…”

Section: ■ Introductionmentioning

confidence: 99%

Single-Molecule Electrochemical Gating in Ionic Liquids

et al. 2012

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The single-molecular conductance of a redox active molecular bridge has been studied in an electrochemical single-molecule transistor configuration in a room-temperature ionic liquid (RTIL). The redox active pyrrolo-tetrathiafulvalene (pTTF) moiety was attached to gold contacts at both ends through −(CH2)6S– groups, and gating of the redox state was achieved with the electrochemical potential. The water-free, room-temperature, ionic liquid environment enabled both the monocationic and the previously inaccessible dicationic redox states of the pTTF moiety to be studied in the in situ scanning tunneling microscopy (STM) molecular break junction configuration. As the electrode potential is swept to positive potentials through both redox transitions, an ideal switching behavior is observed in which the conductance increases and then decreases as the first redox wave is passed, and then increases and decreases again as the second redox process is passed. This is described as an “off–on–off–on–off” conductance switching behavior. This molecular conductance vs electrochemical potential relation could be modeled well as a sequential two-step charge transfer process with full or partial vibrational relaxation. Using this view, reorganization energies of ∼1.2 eV have been estimated for both the first and second redox transitions for the pTTF bridge in the 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIOTf) ionic liquid environment. By contrast, in aqueous environments, a much smaller reorganization energy of ∼0.4 eV has been obtained for the same molecular bridge. These differences are attributed to the large, outer-sphere reorganization energy for charge transfer across the molecular junction in the RTIL.

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“…Here, the electrochemical gating of the charge transport through a surface-bound PTM radical has been explored using an electrochemical scanning tunnelling spectroscopy (EC-STS) technique. We demonstrated current enhancement due to the redox-mediated electron tunnelling (RMET) mechanism [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] involving the PTM radical as the active redox-centre. Our results show that, in comparison with other redox-active moieties, the PTM radical is among the most efficient redox mediators in RMET, demonstrating its applicability as an active electronic component in electronic devices of nanoscale size.…”

mentioning

confidence: 99%