Year: 2026
Type: preprint
Abstract: Covalent sp 3 quantum defects in single-walled carbon nanotubes (SWCNTs) unlock powerful capabilities for quantum nanosensors, bioimaging, and optoelectronic devices. However, the chemical diversity of accessible quantum defects has been constrained by dependence on aryl diazonium salts, which are inherently unstable, prone to side reactions, and of which only a few dozen are commercially available, limiting color center/quantum well defect engineering to a narrow slice of chemical space. A recently developed handle-free Fenton-based approach expanded defect diversity across over 200 small molecules but is limited to small, polar, and aliphatic substrates, leaving aryl rings and extended alkyl chains largely inaccessible. Here, we report a boronic acid deboronation strategy that directly addresses this gap. Under Fenton oxidative conditions, both aryl and alkyl boronic acids undergo homolytic C-B cleavage to generate carbon-centered radicals that add covalently to the SWCNT sidewall under mild, aqueous conditions. With thousands of structurally diverse boronic acids commercially available as bench-stable solids, this chemistry opens access to a quantum defect library orders of magnitude larger than previously achievable using aryl diazonium salts. We observed this generality across more than 50 substrates spanning electron-donating, electron-withdrawing, and heteroaromatic structures, and establish a linear Hammett correlation between substituent electronics and defect-state emission wavelength that enables predictive control over defect photophysics. Furthermore, by employing meta and para positional isomers of representative substrates, this work provides the first systematic investigation of mesomeric versus inductive substituent effects on both the extent of SWCNT covalent functionalization and the resulting quantum well depth. To demonstrate the utility of this expanded defect library, we rationally designed four NIR-fluorescent SWCNT pH nanosensors spanning a pK a range of 5.2 to 7.2. This work establishes boronic acid deboronation as a practical and scalable route to SWCNT quantum defects for sensing, bioimaging, optoelectronic, and quantum photonic applications.
Source: ChemRxiv
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7161822979