Single molecule diagnostics via electric current noise

Recent progress in single molecule detection techniques has revolutionized our fundamental understanding of biological phenomena such as protein dynamics and DNA replications. In single molecule experiments, stochastic nature of molecular fluctuations in general acts as an inevitable source of noise that obscures fine details and complicates the identification of the molecular identity. In sharp contrast, we herein demonstrate for the first time the single-molecule diagnosis via molecular-vibration-induced current noise. We find that inelastic noise in a single-molecule tunneling junction increases in a stepwise fashion synchronous to the onsets of inelastic excitations of its distinct vibrational modes active in the electron-phonon interaction, which thereby enable single-molecule fingerprinting through examining the noise spectra. We are also able to identify the electron-phonon coupling strength and the symmetry of a single organic molecule from the distinct noise characteristics. As electron-vibration interactions exist in virtually any types of molecules, these findings suggest a potential use of inelastic noise as a useful molecular signature for single-molecule identifications with high specificity that may open new venues for practical realization of the “forth generation” DNA sequencer.

Nature Communications 1:138 doi: 10.1038/ncomms1141 (2010).