KCS

Molecular spectroscopy has been widely used for identifying different molecules and compounds using various spectroscopy techniques like IR, Raman, and NMR. However, their use is often limited in nanoscience because of their resolution limit. Modulation of molecular orbitals in molecular systems is useful to tune the performance of electron/spin transport [1]. Electron/spin transport phenomena in molecular electronic/spintronic devices can be understood based on density functional theory (DFT) coupled to non-equilibrium Green function theory (NEGF) with which we have developed the Postrans program package [1,2]. We find that measuring two-dimensional conductance spectra of graphene nanoribbon (GNR) placed across a fluidic nanochannel leads to a fast DNA sequencing method [3]. As a single-stranded DNA (ssDNA) passes beneath the GNR, a single base interacts with the GNR via π-π stacking, giving a sharp conductance change due to Fano resonance. These unique resonance profiles reflecting the characteristic features and conformations of physisorbed molecules lead to two-dimensional molecular electronics spectroscopy (2D MES) [3,4]. The differential conductance with respect to bias and gate voltages not only distinguishes different types of nucleobases for DNA sequencing but also recognizes cancerous methylated nucleobases. This new 2D MES could open an exciting field to recognize single molecule signatures at atomic resolution. The advantages of the 2D MES over the 1D current analysis can be comparable to those of 2D NMR over 1D NMR analysis. [1] W. Y. Kim et al. Acc. Chem. Res. 43, 111 (2010). [2] W. Y. Kim et al. Nature Nanotech. 3, 408 (2008). [3] S. K. Min et al. Nature Nanotech. 6, 162 (2011). [4] A. C. Rajan et al. ACS Nano (2014). (in press). DOI: 10.1021/nn4062148