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Single-entity electrochemistry is of fundamental importance and shows promise for ultrasensitive biosensing applications. Recently, we have demonstrated that various charged nanoparticles can be detected individually based on the non-redox open-circuit potential (OCP) changes induced by their collision events on a floating carbon nanoelectrode (CNE). Unlike the widely used amperometry approach, the potentiometric method provides the label-free detection of individual nanoscale entities without redox mediators in the solution. However, the CNE lacks specificity for molecular recognition during the collision events because of the limited methods of surface functionalization for carbon surfaces. Herein, we used surface-functionalized gold nanoelectrode (GNE) to overcome this limitation of CNE. The GNE modified with Raman reporter molecule also enabled surface-enhanced Raman spectroscopy (SERS) measurements. By using simultaneous time-resolved OCP and SERS measurements, both the OCP and SERS signals induced by the “hit-n-run” type of gold nanoparticle (GNP) collision events can be better understood. Also, by introducing a zwitterionic molecule, we formed near “stealth” surface and demonstrated that the non-specific adsorptions of GNPs to the surface of GNE have been suppressed, allowing continuous detection of hit-n-run events for over 30 min.
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Modulating and probing the dynamic intermolecular interactions in plasmonic molecule-pair junctions
Reversible intermolecular interactions play critical roles in nature. However, it is still challenging to monitor the dynamic intermolecular interactions at the single-molecule level in aqueous solution. Here, we studied the dynamic changes of intermolecular interactions at the carboxyl/carboxyl interfaces between a pair of molecules trapped in a plasmonic nanocavity formed between a gold nanoparticle (GNP) and a gold nanoelectrode (GNE). The development of intermolecular interactions, including the appearance of hydrogen bonds (h-bonds), during and after single GNP collision events on the GNE, was monitored by time-resolved surface-enhanced Raman spectroscopy at a tens of milliseconds time resolution. Spectral fingerprints of the carboxyl group corresponding to non-specific intermolecular interactions and h-bonds are identified. Furthermore, we demonstrated that the strength of intermolecular interaction could be mechanically modulated by changing the applied bias at the GNE, which resulted in small and controllable changes in the nanogap distance. Unlike non-specific intermolecular interactions, the intermolecular h-bonds can only be formed stochastically and are more sensitive to the gap distance modulation. This report demonstrates a new approach to modulate and probe intermolecular interactions within nanogaps.
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- Award ID(s):
- 1647837
- PAR ID:
- 10134088
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 21
- Issue:
- 29
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 15940 to 15948
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9CP02030F
