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Single-molecule identification via electric current noise.

Tsutsui M, Taniguchi M, Kawai T - Nat Commun (2010)

Bottom Line: Label-free and real-time single-molecule detection may aid the development of high-throughput biosensing platforms.We found increased current oscillations synchronous to electric field excitations of characteristic molecular vibrational modes that contribute to inelastic electron tunnelling.This finding demonstrates a large contribution of charge interaction with nuclear dynamics on noise properties of single-molecule bridges and suggests a potential use of inelastic noise as a valuable molecular signature for single-molecule identification.

View Article: PubMed Central - PubMed

Affiliation: The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.

ABSTRACT
Label-free and real-time single-molecule detection may aid the development of high-throughput biosensing platforms. Molecular fluctuations are a source of noise that often hinders single-molecule identification by obscuring the fine details of molecular identity. In this study, we report molecular identification through direct observation of quantum-fluctuation-induced inelastic noise in single organic molecules. We investigated current fluctuations flowing through a single molecule that is chemically connected to two electrodes. We found increased current oscillations synchronous to electric field excitations of characteristic molecular vibrational modes that contribute to inelastic electron tunnelling. This finding demonstrates a large contribution of charge interaction with nuclear dynamics on noise properties of single-molecule bridges and suggests a potential use of inelastic noise as a valuable molecular signature for single-molecule identification.

No MeSH data available.


Related in: MedlinePlus

A measurement scheme for characterizing current fluctuations in single-molecule junctions.(a) A schematic illustration showing a measurement circuit used to investigate the high-field conductance fluctuations in Au–HDT–Au single-molecule junctions at 4.2 K. (b) IET spectrum of the HDT single-molecule junction formed by a self-breaking technique at 4.2 K. The peaks indicated by arrows can all be assigned to the IETS-active molecular vibrational modes (Supplementary Figs S1–S3 for details). (c) An example of I–Vb characteristics acquired for HDT single-molecule junctions at 1.3 mG0 conductance state. (d) Differential conductance numerically derived from the I–Vb curve in b, revealing considerable fluctuations at high Vb regimes. (e) 50-point current measurements conducted for evaluating the bias voltage-induced conductance fluctuations observed in HDT single-molecule junctions. (f) A magnified view of the plots in e. Black and red dots are the 50-point current data measured at each Vb and the corresponding average current <I>. Error bars denote s.d.
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f1: A measurement scheme for characterizing current fluctuations in single-molecule junctions.(a) A schematic illustration showing a measurement circuit used to investigate the high-field conductance fluctuations in Au–HDT–Au single-molecule junctions at 4.2 K. (b) IET spectrum of the HDT single-molecule junction formed by a self-breaking technique at 4.2 K. The peaks indicated by arrows can all be assigned to the IETS-active molecular vibrational modes (Supplementary Figs S1–S3 for details). (c) An example of I–Vb characteristics acquired for HDT single-molecule junctions at 1.3 mG0 conductance state. (d) Differential conductance numerically derived from the I–Vb curve in b, revealing considerable fluctuations at high Vb regimes. (e) 50-point current measurements conducted for evaluating the bias voltage-induced conductance fluctuations observed in HDT single-molecule junctions. (f) A magnified view of the plots in e. Black and red dots are the 50-point current data measured at each Vb and the corresponding average current <I>. Error bars denote s.d.

Mentions: We explored high-field conductance fluctuations in 1,6-hexanedithiol (HDT) single molecules trapped between two Au nanoelectrodes (HDT single-molecule junctions) using a self-breaking technique at 4 K under a low applied voltage of 0.2 V (Fig. 1a,b; Supplementary Figs S1–S3). Figure 1c shows an I–Vb curve measured by a direct current (DC) method. The linear characteristics represent tunnelling electron transport through an HDT molecule, with a large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap exceeding 6 eV that yields a high carrier injection barrier at the metal–molecule interfaces when bonded to Au electrodes. In addition, we observe that current tends to become unstable with increasing Vb. Correspondingly, the numerical differential conductance exhibits considerable fluctuations at high-Vb regimes (Fig. 1d). We note that the magnitude of the fluctuations is enhanced with increasing Vb.


Single-molecule identification via electric current noise.

Tsutsui M, Taniguchi M, Kawai T - Nat Commun (2010)

A measurement scheme for characterizing current fluctuations in single-molecule junctions.(a) A schematic illustration showing a measurement circuit used to investigate the high-field conductance fluctuations in Au–HDT–Au single-molecule junctions at 4.2 K. (b) IET spectrum of the HDT single-molecule junction formed by a self-breaking technique at 4.2 K. The peaks indicated by arrows can all be assigned to the IETS-active molecular vibrational modes (Supplementary Figs S1–S3 for details). (c) An example of I–Vb characteristics acquired for HDT single-molecule junctions at 1.3 mG0 conductance state. (d) Differential conductance numerically derived from the I–Vb curve in b, revealing considerable fluctuations at high Vb regimes. (e) 50-point current measurements conducted for evaluating the bias voltage-induced conductance fluctuations observed in HDT single-molecule junctions. (f) A magnified view of the plots in e. Black and red dots are the 50-point current data measured at each Vb and the corresponding average current <I>. Error bars denote s.d.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3105297&req=5

f1: A measurement scheme for characterizing current fluctuations in single-molecule junctions.(a) A schematic illustration showing a measurement circuit used to investigate the high-field conductance fluctuations in Au–HDT–Au single-molecule junctions at 4.2 K. (b) IET spectrum of the HDT single-molecule junction formed by a self-breaking technique at 4.2 K. The peaks indicated by arrows can all be assigned to the IETS-active molecular vibrational modes (Supplementary Figs S1–S3 for details). (c) An example of I–Vb characteristics acquired for HDT single-molecule junctions at 1.3 mG0 conductance state. (d) Differential conductance numerically derived from the I–Vb curve in b, revealing considerable fluctuations at high Vb regimes. (e) 50-point current measurements conducted for evaluating the bias voltage-induced conductance fluctuations observed in HDT single-molecule junctions. (f) A magnified view of the plots in e. Black and red dots are the 50-point current data measured at each Vb and the corresponding average current <I>. Error bars denote s.d.
Mentions: We explored high-field conductance fluctuations in 1,6-hexanedithiol (HDT) single molecules trapped between two Au nanoelectrodes (HDT single-molecule junctions) using a self-breaking technique at 4 K under a low applied voltage of 0.2 V (Fig. 1a,b; Supplementary Figs S1–S3). Figure 1c shows an I–Vb curve measured by a direct current (DC) method. The linear characteristics represent tunnelling electron transport through an HDT molecule, with a large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap exceeding 6 eV that yields a high carrier injection barrier at the metal–molecule interfaces when bonded to Au electrodes. In addition, we observe that current tends to become unstable with increasing Vb. Correspondingly, the numerical differential conductance exhibits considerable fluctuations at high-Vb regimes (Fig. 1d). We note that the magnitude of the fluctuations is enhanced with increasing Vb.

Bottom Line: Label-free and real-time single-molecule detection may aid the development of high-throughput biosensing platforms.We found increased current oscillations synchronous to electric field excitations of characteristic molecular vibrational modes that contribute to inelastic electron tunnelling.This finding demonstrates a large contribution of charge interaction with nuclear dynamics on noise properties of single-molecule bridges and suggests a potential use of inelastic noise as a valuable molecular signature for single-molecule identification.

View Article: PubMed Central - PubMed

Affiliation: The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.

ABSTRACT
Label-free and real-time single-molecule detection may aid the development of high-throughput biosensing platforms. Molecular fluctuations are a source of noise that often hinders single-molecule identification by obscuring the fine details of molecular identity. In this study, we report molecular identification through direct observation of quantum-fluctuation-induced inelastic noise in single organic molecules. We investigated current fluctuations flowing through a single molecule that is chemically connected to two electrodes. We found increased current oscillations synchronous to electric field excitations of characteristic molecular vibrational modes that contribute to inelastic electron tunnelling. This finding demonstrates a large contribution of charge interaction with nuclear dynamics on noise properties of single-molecule bridges and suggests a potential use of inelastic noise as a valuable molecular signature for single-molecule identification.

No MeSH data available.


Related in: MedlinePlus