Label-Free Dynamic Detection of Single-Molecule Nucleophilic-Substitution Reactions

Chunhui Gu, Chen Hu, Ying Wei, Dongqing Lin, Chuancheng Jia, Mingzhi Li, Dingkai Su, Jianxin Guan, Andong Xia, Linghai Xie, Abraham Nitzan, Hong Guo*, Xuefeng Guo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


The mechanisms of chemical reactions, including the transformation pathways of the electronic and geometric structures of molecules, are crucial for comprehending the essence and developing new chemistry. However, it is extremely difficult to realize at the single-molecule level. Here, we report a single-molecule approach capable of electrically probing stochastic fluctuations under equilibrium conditions and elucidating time trajectories of single species in non-equilibrated systems. Through molecular engineering, a single molecular wire containing a functional center of 9-phenyl-9-fluorenol was covalently wired into nanogapped graphene electrodes to form stable single-molecule junctions. Both experimental and theoretical studies consistently demonstrate and interpret the direct measurement of the formation dynamics of individual carbocation intermediates with a strong solvent dependence in a nucleophilic-substitution reaction. We also show the kinetic process of competitive transitions between acetate and bromide species, which is inevitable through a carbocation intermediate, confirming the classical mechanism. This unique method creates plenty of opportunities for carrying out single-molecule dynamics or biophysics investigations in broad fields beyond reaction chemistry through molecular design and engineering.

Original languageEnglish
Pages (from-to)4156-4162
Number of pages7
JournalNano Letters
Issue number7
StatePublished - 11 Jul 2018
Externally publishedYes


FundersFunder number
National Key R&D Program of China
Natural Sciences and Engineering Research Council of Canada
National Natural Science Foundation of China21727806
Natural Science Foundation of Beijing MunicipalityZ181100004418003
Peking University
National Key Research and Development Program of China2017YFA0204901


    • Single-molecule detection
    • molecular electronics
    • nucleophilic substitution
    • reaction dynamics


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