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Direct single-molecule dynamic detection of chemical reactions.

  • Author(s): Guan, Jianxin;
  • Jia, Chuancheng;
  • Li, Yanwei;
  • Liu, Zitong;
  • Wang, Jinying;
  • Yang, Zhongyue;
  • Gu, Chunhui;
  • Su, Dingkai;
  • Houk, Kendall N;
  • Zhang, Deqing;
  • Guo, Xuefeng
  • et al.
Abstract

Single-molecule detection can reveal time trajectories and reaction pathways of individual intermediates/transition states in chemical reactions and biological processes, which is of fundamental importance to elucidate their intrinsic mechanisms. We present a reliable, label-free single-molecule approach that allows us to directly explore the dynamic process of basic chemical reactions at the single-event level by using stable graphene-molecule single-molecule junctions. These junctions are constructed by covalently connecting a single molecule with a 9-fluorenone center to nanogapped graphene electrodes. For the first time, real-time single-molecule electrical measurements unambiguously show reproducible large-amplitude two-level fluctuations that are highly dependent on solvent environments in a nucleophilic addition reaction of hydroxylamine to a carbonyl group. Both theoretical simulations and ensemble experiments prove that this observation originates from the reversible transition between the reactant and a new intermediate state within a time scale of a few microseconds. These investigations open up a new route that is able to be immediately applied to probe fast single-molecule physics or biophysics with high time resolution, making an important contribution to broad fields beyond reaction chemistry.

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