Noncovalent Monolayer Modification of Graphene Using Pyrene and Cyclodextrin Receptors for Chemical Sensing

Abstract

Surprisingly few details have been reported in the literature that help the experimentalist to determine the conditions necessary for the preparation of self-assembled monolayers on graphene with a high surface coverage. With a view to graphene-based sensing arrays and devices and, in particular, in view of graphene-based varactors for gas sensing, graphene was modified in this work by the π−π interaction-driven self-assembly of 10 pyrene and cyclodextrin derivatives from solution. The receptor compounds were pyrene, pyrene derivatives with hydroxyl, carboxyl, ester, ammonium, amino, diethylamino, and boronic acid groups, and perbenzylated α-, β-, and γ-cyclodextrins. Adsorption of these compounds onto graphene was quantified by contact-angle measurements and X-ray photoelectron spectroscopy. Data thus obtained were fitted with the Langmuir adsorption model to determine the equilibrium constants for surface adsorption and the concentrations of self-assembly solutions needed to form dense monolayers on graphene. The equilibrium constants of all pyrene derivatives fell into the range from 10 3.4 to 10 4.6 M −1 . For the perbenzylated α-, β-, and γcyclodextrins, the equilibrium constants are 10 3.24 , 10 2.97 , and 10 2.95 M −1 , respectively. Monolayers of 1-pyrenemethylammonium chloride on graphene were confirmed to be stable under heating to 100 °C in a high vacuum (2 × 10 −5 Torr).

Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

“…Functionalized CDs can also alter the formation of the inclusion complex and therefore the functionalized groups can be selected to tailor the binding between the CD and the target analyte, to give improved sensitive and selective detection. Furthermore, aromatic functional groups can be utilized to form dense self-assembled monolayers using noncovalent π-π interactions [54]. These approaches are illustrated in the schematic presented in Figure 4b.…”

Chemically Functionalised Graphene FET Biosensor for the Label-free Sensing of Exosomes

“…Figure 1 also shows the molecular structure of 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE), which is a heterobifunctional linker. The pyrene group stacks with graphene by π − π overlap to form a self-assembled monolayer with homogenous coverage 29 , whilst the N-hydroxysuccinimide (NHS) ester is able to react with primary amines present on a range of biomolecules, such as antibodies.

Figure 1Schematic of the functionalised biosensor with microfluidic integration, showing the different doping levels of the covered and uncovered graphene as a result of exosome binding. Schematic of the basic structure of an exosome and molecular structure of 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE).

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Harnessing selectivity in chemical sensing via supramolecular interactions: from functionalization of nanomaterials to device applications

“…In particular, graphene's extended sp 2 -hybridized carbon network makes it especially suitable for functionalization with planar aromatic molecules via p-p stacking. 69,70,80 Pyrene-derivatives bearing a functional substituent or receptor moiety can functionalize graphene without disrupting its extended honeycomb structure and resulting outstanding electronic properties. The majority of applications though that use of pyrene-derivatives to functionalize graphene still relies on the immobilization of bioreceptors for biosensing.…”