Effect of tight flavin mononucleotide wrapping and its binding affinity on carbon nanotube covalent reactivities

Abstract

The controlled functionalization of single-walled carbon nanotubes (SWNTs) is a key to using them in high-end applications. We show that nanotube reactivity after covalent diazonium modification is governed by a chirality-specific surfactant binding affinity to SWNTs. Both metallic and semiconducting SWNTs tightly organized by a helical flavin mononucleotide (FMN) assembly exhibit two hundred times slower reactivity toward 4-methoxy benzenediazonium (4-MBD) than those wrapped by sodium dodecyl sulfate and this reactivity enables chirality- and metallicity-specific behaviours to be probed, as confirmed by absorption, Raman, and photoluminescence (PL) spectroscopy. Each reaction kinetic of the two-step SWNT PL decays originating from electron transfer and the covalent reaction of 4-MBD, respectively, is inversely proportional to the binding affinity (Ka) between FMN and the SWNTs. The observed marginally higher reaction rate of the metallic nanotube compared to the semiconducting one results from the weaker Ka value of the metallic nanotubes with FMN. An enrichment demonstration of a few nanotube chiralities using selective and slow covalent diazonium chemistry demonstrates the importance of the binding affinity between the surfactant and the SWNTs. The study provides a handle on chirality-specific covalent chemistry via surfactant-SWNT binding affinity and impacts on future-sensing schemes.

Triazine‐Carbon Nanotubes: New Platforms for the Design of Flavin Receptors

“…Higher association constants between flavins and 2,4‐diamino‐1,3,5‐triazines with different aromatic substituents are observed as a consequence of the increase in the π‐overlap between these compounds (values from 394 to 17 600 L mol −1 ) . Nanotubes are easily able to form π‐π interactions even with flavins and the high values of the association constants in our system could be due to the presence of π‐π stacking together with the formation of hydrogen bonds.…”

Affinity-mediated sorting order reversal of single-walled carbon nanotubes in density gradient ultracentrifugation

“…This indicates that binding affinity plays a role for FMN-based nanotube sorting in DGU. We speculate that the above preferential sorting of the (8, 6) tube in DGU compared to the (9, 4) and (8, 4) tubes originates from the higher stability of the FMN-(8, 6) tube, along with the initial chirality abundance in online supplementary figure S1 [11,29,28]. In fact, there is a dynamic equilibrium between free FMN and FMN on SWNTs.…”

Recent Advances in Structure Separation of Single‐Wall Carbon Nanotubes and Their Application in Optics, Electronics, and Optoelectronics

“…[128] The formation of a helical ribbon of flavin mononucleotide (FMN) around nanotubes was attributed to the cooperative hydrogen bonding between adjacent flavin moieties under concentric 𝜋-𝜋 interactions with nanotube surfaces. [128] Although the nucleotides have demonstrated certain ability for the structure recognition of SWCNTs in subsequent studies, [129,[158][159][160][161] their efficiencies for dispersion and separation are still limited, compared with the widely used ssDNA and conjugated polymers mentioned above.…”