Atomic Force Microscopy Study of new Sensing Platforms: Cucurbit[ n ]uril ( n =6, 7) on Gold

Host-Guest Chemistry Meets Electrocatalysis: Cucurbit[6]uril on a Au Surface as a Hybrid System in CO2 Reduction

The rational control of forming and stabilizing reaction intermediates to guide specific reaction pathways remains to be a major challenge in electrocatalysis. In this work, we report a surface active-site engineering approach for modulating electrocatalytic CO₂ reduction using the macrocycle cucurbit[6]uril (CB[6]). A pristine gold surface functionalized with CB[6] nanocavities was studied as a hybrid organic–inorganic model system that utilizes host–guest chemistry to influence the heterogeneous electrocatalytic reaction. The combination of surface-enhanced infrared absorption (SEIRA) spectroscopy and electrocatalytic experiments in conjunction with theoretical calculations supports capture and reduction of CO₂ inside the hydrophobic cavity of CB[6] on the gold surface in aqueous KHCO₃ at negative potentials. SEIRA spectroscopic experiments show that the decoration of gold with the supramolecular host CB[6] leads to an increased local CO₂ concentration close to the metal interface. Electrocatalytic CO₂ reduction on a CB[6]-coated gold electrode indicates differences in the specific interactions between CO₂ reduction intermediates within and outside the CB[6] molecular cavity, illustrated by a decrease in current density from CO generation, but almost invariant H₂ production compared to unfunctionalized gold. The presented methodology and mechanistic insight can guide future design of molecularly engineered catalytic environments through interfacial host–guest chemistry.

Cucurbituril mediated single molecule detection and identification via recognition tunneling

Recognition tunneling (RT) is an emerging technique for investigating single molecules in a tunnel junction. We have previously demonstrated its capability of single molecule detection and identification, as well as probing the dynamics of intermolecular bonding at the single molecule level. Here by introducing cucurbituril as a new class of recognition molecule, we demonstrate a powerful platform for electronically investigating the host-guest chemistry at single molecule level. In this report, we first investigated the single molecule electrical properties of cucurbituril in a tunnel junction. Then we studied two model guest molecules, aminoferrocene and amantadine, which were encapsulated by cucurbituril. Small differences in conductance and lifetime can be recognized between the host-guest complexes with the inclusion of different guest molecules. By using a machine learning algorithm to classify the RT signals in a hyper dimensional space, the accuracy of guest molecule recognition can be significantly improved, suggesting the possibility of using cucurbituril molecule for single molecule identification. This work enables a new class of recognition molecule for RT technique and opens the door for detecting a vast variety of small molecules by electrical measurements.

A simple modular aptasensor platform utilizing cucurbit[7]uril and a ferrocene derivative as an ultrastable supramolecular linker

A simple modular aptamer-based sensor (aptasensor) platform was prepared by combining the merits of the rapid and efficient preparation of a self-assembled monolayer of cucurbit[7]uril (CB[7] SAM) and the strong and specific binding affinity of CB[7] to ferrocenemethylammonium (FA), as an ultrastable supramolecular linker, to immobilize aptamers on CB[7] SAM.