Professor Guo Xuefeng’s Group makes process in the Single-molecule Devices

DEC . 07 2016
Peking University, Nov.28, 2016: Single-molecule electronic devices investigate the properties of individual molecules in a unique way and have a wide use in the dynamic measurements. Also they have some requirements: the labels, the highly precise fabrication and the fast measure time.
Recently, Professor Guo Xuefeng’s group, from College of Chemistry and Molecular Engineering of PKU, developed a new way of single-molecule electronic devices by graphene-molecule single-molecule junction and SiNW (One dimensional silicon nanowires)-based single-molecule electrical biosensors. The corresponding researchers were reported in the scientific journal Angewandte Chemie International Edition and Science Advances.
In previous work, Professor Guo’s Group had fabricated SiNW-based single-molecule electrical biosensors by a three-step process and developed a direct, real-time electrical approach of sensing intermolecular interactions in biological systems with single-molecule sensitivity (Angew. Chem. Int. Ed. 2014, 53, 5038). In this study, they used such a high-gain, field-effect-based single-molecule methodology to achieve measurements of hairpin hybridization kinetics with sufficiently high signal-to-noise ratio and bandwidth. With this method, they found a strong temperature dependent two-level current oscillations, which revealed the thermodynamic and kinetic properties of hairpin DNA hybridization. And the results were in agreement with the optical results.

Diagram of single-hairpin DNA-decorated SiNW biosensors
Besides, at low temperature, they found that the conductance of the dive had successive stepwise increases and decreases on a microsecond timescale, indicating a base-by-base unfolding/folding process. Based on this, they constructeda kinetic zipper model for DNA hybridization/dehybridization at the single base-pair level. The research was reported in the scientific journal Angewandte Chemie International Edition (Angew. Chem. Int. Ed. 2016, 55, 9035)
Guo’s group has been investigating the fabrication of carbon electrode-molecule single-molecule junctions (CEM-SMJs) for a long period of time, and they successfully solved the problems of fabrication and stability. Based on this, Guo’s group developed graphene-molecule SMJ into a single-molecule photoelectronic device (Science 2016, 352, 1443; Angew. Chem. Int. Ed. 2013, 52, 8666) and biosensor (Angew. Chem. Int. Ed. 2012, 51, 12228; Chem. Sci. 2015, 6, 2469; J. Mater. Chem. B 2015, 3, 5150).

Schematic representation of the system
Recently, Guo’s group cooperated with J. Fraser Stoddart (2016 chemistry Nobel Prize winner) from Northwestern University to transduce the physical pseudorotaxane (de)formation process between the electron-richcrown ether and a dicationic guest into real-time electrical signals. Compared with the traditional research methods like MS and NMR, this approach has advantages such as simple fabrication, low cost, no fluorescent labeling/bleaching problems, and direct real-time measurements at single-molecule sensitivity levels. Also it can establish a route to develop single-molecule dynamics investigations with microsecond resolution for a broad range of both chemical and biochemical applications. This research was reported in the scientific journal Science Advances (Sci. Adv. 2016, 2, e1601113).
Written by: Li Yao
Edited by: Wang Qian
Source: PKU News (Chinese)