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Recognition properties of cucurbit[7]uril self-assembled monolayers studied with force spectroscopy
Alberto Gomez-Casado1, Pascal Jonkheijm, Jurriaan Huskens
1Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500AE, Enschede, The Netherlands.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 13, 2011
Summary
Specific interactions between cucurbit[7]uril (CB[7]) monolayers and adamantyl guests on gold are stronger and more stable than non-specific binding. This explains the utility of CB[n] monolayers for surface immobilization.
Area of Science:
- Supramolecular chemistry
- Surface science
- Nanotechnology
Background:
- Self-assembled monolayers (SAMs) are crucial for surface functionalization.
- Cucurbiturils (CB[n]) are macrocyclic hosts with unique binding properties.
- Understanding host-guest interactions at the single-molecule level is key for designing advanced materials.
Purpose of the Study:
- To quantify and compare specific (host-guest) and unspecific (substrate-guest) interactions.
- To investigate the binding stability of adamantyl guests to cucurbit[7]uril (CB[7]) monolayers on gold (Au) substrates.
- To elucidate the role of CB[7] monolayer coverage and interaction strength in surface immobilization.
Main Methods:
- Dynamic force spectroscopy (DFS) was employed to probe single-molecule interactions.
- Analysis of dissociation rate constants for adamantyl-gold (Ad-Au) and adamantyl-cucurbit[7]uril (Ad-CB[7]) interactions.
- Determination of the probability of observing specific Ad-CB[7] interactions.
Main Results:
- Specific Ad-CB[7] interactions exhibit a lower dissociation rate constant (0.03 s⁻¹) compared to unspecific Ad-Au interactions (0.3 s⁻¹), indicating greater stability.
- The observed probability of specific interactions (40 ± 9%) correlates with reported CB[7] surface coverages.
- The enhanced strength and stability of Ad-CB[7] binding were confirmed.
Conclusions:
- Specific host-guest interactions mediated by CB[7] monolayers are significantly more stable than non-specific binding to the gold substrate.
- Despite imperfect surface coverage, the robust nature of CB[7]-adamantyl interactions enables their successful application as immobilization platforms.
- These findings provide fundamental insights into the design and application of supramolecular systems for surface engineering.
