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Tracking Confined Reaction Based on Host-Guest Interaction Using Single-Molecule Conductance Measurement
Saisai Yuan1, Qiaozan Qian1, Yu Zhou1
1State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
Scanning tunneling microscope-break junction (STM-BJ) offers sensitive detection of confined reactions at micromolar concentrations, surpassing nuclear magnetic resonance (NMR) limitations. This technique reveals reaction kinetics and the impact of electric fields on supramolecular chemistry.
Area of Science:
- Supramolecular Chemistry
- Nanotechnology
- Physical Chemistry
Background:
- Host-guest interactions are fundamental to supramolecular chemistry and confined reactions.
- Studying dynamic processes in confined reactions at low concentrations (micromolar or lower) is challenging.
- Traditional methods like nuclear magnetic resonance (NMR) struggle with sensitivity at these low concentrations.
Purpose of the Study:
- To develop and demonstrate a novel method for characterizing confined reaction dynamics at micromolar concentrations.
- To compare the sensitivity and quantitative capabilities of scanning tunneling microscope-break junction (STM-BJ) with NMR for studying confined reactions.
- To investigate the influence of a strong electric field on reaction kinetics within a nanoconfined environment.
Main Methods:
- Utilized the scanning tunneling microscope-break junction (STM-BJ) technique to monitor the dimerization of 1,2-bis(4-pyridinyl) ethylene within cucurbit[8]uril.
- Employed in situ single-molecule electrical measurements to detect reaction kinetics.
- Performed nuclear magnetic resonance (NMR) spectroscopy for comparative analysis of reaction kinetics.
Main Results:
- STM-BJ successfully detected electrical signals from reactants at concentrations as low as 5 × 10⁻⁶ M, enabling quantitative kinetic analysis.
- NMR measurements failed to detect characteristic signals below 0.5 × 10⁻³ M, highlighting its limitations at micromolar concentrations.
- The strong electric field present in the STM-BJ nanogap was observed to accelerate the confined reaction rate.
Conclusions:
- Single-molecule STM-BJ techniques provide superior sensitivity for tracking confined reactions compared to NMR, especially at micromolar concentrations.
- STM-BJ is a powerful tool for studying the kinetics of host-guest interactions in supramolecular chemistry.
- The study demonstrates the potential of STM-BJ to investigate the effects of extreme electric fields on reaction kinetics in confined systems.
