Effect of tight flavin mononucleotide wrapping and its binding affinity on carbon nanotube covalent reactivitiesElectronic supplementary information (ESI) available: Supplementary Movies S1-S2, methods for normalization of absorption spectra, full explanation of XPS characterization, absorption spectra change of FMN- and SDS-SWNT after the addition of 4-MBD, XPS spectra, photoluminescence decay kinetics, cyclovoltammogram of 4-MBD, the overlap plot between the chirality-dependent potential & cov

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 ( K a ) between FMN and the SWNTs. The observed marginally higher reaction rate of the metallic nanotube compared to the semiconducting one results from the weaker K a 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. Nanotubes with tight helical flavin mononucleotide wrapping have effective passivation toward chemical stimuli. Their reactivity with covalent diazonium modification is inversely proportional to their chirality-specific surfactant binding affinity.