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Thermoelectric effect and its dependence on molecular length and sequence in single DNA molecules.

Li Y, Xiang L, Palma JL, Asai Y, Tao N - Nat Commun (2016)

Bottom Line: The thermoelectric effect is small and insensitive to the molecular length in the hopping regime.In contrast, the thermoelectric effect is large and sensitive to the length in the tunnelling regime.We describe the experimental results in terms of hopping and tunnelling charge transport models.

View Article: PubMed Central - PubMed

Affiliation: Center for Bioelectronics and Biosensors, Biodesign Institute, Arizona State University, Tempe, Arizona 85287-5801, USA.

ABSTRACT
Studying the thermoelectric effect in DNA is important for unravelling charge transport mechanisms and for developing relevant applications of DNA molecules. Here we report a study of the thermoelectric effect in single DNA molecules. By varying the molecular length and sequence, we tune the charge transport in DNA to either a hopping- or tunnelling-dominated regimes. The thermoelectric effect is small and insensitive to the molecular length in the hopping regime. In contrast, the thermoelectric effect is large and sensitive to the length in the tunnelling regime. These findings indicate that one may control the thermoelectric effect in DNA by varying its sequence and length. We describe the experimental results in terms of hopping and tunnelling charge transport models.

No MeSH data available.


Seebeck coefficients of DNA with different molecular lengths and sequences.The black squares are the Seebeck coefficients of A(CG)nT (n=1, 2, 3). The blue triangles are the Seebeck coefficients of ACGC(AT)mGCGT (m=1–4) and ACGC(AT)m−1AGCGT (m=1−3) sequences, showing a transition when the AT block length is longer than 4 base pairs. The solid and dashed lines are guides to eye.
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f4: Seebeck coefficients of DNA with different molecular lengths and sequences.The black squares are the Seebeck coefficients of A(CG)nT (n=1, 2, 3). The blue triangles are the Seebeck coefficients of ACGC(AT)mGCGT (m=1–4) and ACGC(AT)m−1AGCGT (m=1−3) sequences, showing a transition when the AT block length is longer than 4 base pairs. The solid and dashed lines are guides to eye.

Mentions: Figure 4 summarizes the Seebeck coefficients of DNA with different lengths and sequences, from which we can draw several important conclusions. First, the Seebeck coefficients are positive for all the DNA sequences in both the tunnelling and hopping regimes studied here. It has been predicted that a positive Seebeck coefficient corresponds to hole-dominated charge transport and a negative Seebeck coefficient signals electron-dominated charge transport2. The observation of positive Seebeck coefficients here indicates that holes dominate charge transport in DNA. This is expected because the DNA HOMO level is close to the electrode Fermi level compared with its LUMO level, and is also consistent with the previous experiments1416181935. However, the prediction of the Seebeck coefficient sign is based on a coherent tunnelling model, which is not necessarily applicable to hopping transport. The data shown in this indicate that this prediction appears to be valid also in the hopping regime. Second, the Seebeck coefficients of DNA in the hopping regime (in A(CG)nT) are small, and weakly depend on the molecular length compared with other organic molecules3637. Last, inserting a short AT block (shorter than 5 AT base pairs) into the middle of A(CG)nT leads to a much greater Seebeck coefficient, and it increases with the AT block length. However, when the AT block is longer than 5 AT base pairs, the Seebeck coefficient drops to the level of A(CG)nT and become insensitive the AT length. This transition coincides with the observed tunnelling–hopping transition near 4–5 AT base pairs, which strongly suggests that the thermoelectric effect is large in the tunnelling regime and small in the hopping regime. We discuss these observations below.


Thermoelectric effect and its dependence on molecular length and sequence in single DNA molecules.

Li Y, Xiang L, Palma JL, Asai Y, Tao N - Nat Commun (2016)

Seebeck coefficients of DNA with different molecular lengths and sequences.The black squares are the Seebeck coefficients of A(CG)nT (n=1, 2, 3). The blue triangles are the Seebeck coefficients of ACGC(AT)mGCGT (m=1–4) and ACGC(AT)m−1AGCGT (m=1−3) sequences, showing a transition when the AT block length is longer than 4 base pairs. The solid and dashed lines are guides to eye.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835548&req=5

f4: Seebeck coefficients of DNA with different molecular lengths and sequences.The black squares are the Seebeck coefficients of A(CG)nT (n=1, 2, 3). The blue triangles are the Seebeck coefficients of ACGC(AT)mGCGT (m=1–4) and ACGC(AT)m−1AGCGT (m=1−3) sequences, showing a transition when the AT block length is longer than 4 base pairs. The solid and dashed lines are guides to eye.
Mentions: Figure 4 summarizes the Seebeck coefficients of DNA with different lengths and sequences, from which we can draw several important conclusions. First, the Seebeck coefficients are positive for all the DNA sequences in both the tunnelling and hopping regimes studied here. It has been predicted that a positive Seebeck coefficient corresponds to hole-dominated charge transport and a negative Seebeck coefficient signals electron-dominated charge transport2. The observation of positive Seebeck coefficients here indicates that holes dominate charge transport in DNA. This is expected because the DNA HOMO level is close to the electrode Fermi level compared with its LUMO level, and is also consistent with the previous experiments1416181935. However, the prediction of the Seebeck coefficient sign is based on a coherent tunnelling model, which is not necessarily applicable to hopping transport. The data shown in this indicate that this prediction appears to be valid also in the hopping regime. Second, the Seebeck coefficients of DNA in the hopping regime (in A(CG)nT) are small, and weakly depend on the molecular length compared with other organic molecules3637. Last, inserting a short AT block (shorter than 5 AT base pairs) into the middle of A(CG)nT leads to a much greater Seebeck coefficient, and it increases with the AT block length. However, when the AT block is longer than 5 AT base pairs, the Seebeck coefficient drops to the level of A(CG)nT and become insensitive the AT length. This transition coincides with the observed tunnelling–hopping transition near 4–5 AT base pairs, which strongly suggests that the thermoelectric effect is large in the tunnelling regime and small in the hopping regime. We discuss these observations below.

Bottom Line: The thermoelectric effect is small and insensitive to the molecular length in the hopping regime.In contrast, the thermoelectric effect is large and sensitive to the length in the tunnelling regime.We describe the experimental results in terms of hopping and tunnelling charge transport models.

View Article: PubMed Central - PubMed

Affiliation: Center for Bioelectronics and Biosensors, Biodesign Institute, Arizona State University, Tempe, Arizona 85287-5801, USA.

ABSTRACT
Studying the thermoelectric effect in DNA is important for unravelling charge transport mechanisms and for developing relevant applications of DNA molecules. Here we report a study of the thermoelectric effect in single DNA molecules. By varying the molecular length and sequence, we tune the charge transport in DNA to either a hopping- or tunnelling-dominated regimes. The thermoelectric effect is small and insensitive to the molecular length in the hopping regime. In contrast, the thermoelectric effect is large and sensitive to the length in the tunnelling regime. These findings indicate that one may control the thermoelectric effect in DNA by varying its sequence and length. We describe the experimental results in terms of hopping and tunnelling charge transport models.

No MeSH data available.