Ortho-substituted aryldiazonium design for defect configuration-controlled photoluminescent functionalization of chiral single-walled carbon nanotubes

Defect functionalization using chemical modification of single-walled carbon nanotubes (SWCNTs) is promising, especially for near-infrared photoluminescence (NIR PL) over 1000 nm in advanced telecom and bio/medical applications. The covalent attachment of modifier molecules is utilized to create sp3 carbon defects in the sp2 carbon lattice for bright, red-shifted PL generation. The positional difference in proximal sp3 carbons, known as the defect binding configuration, can dominate NIR PL properties; however, the defect arrangement chemistry remains unelucidated. We developed aryldiazonium modifiers with -conjugated ortho-substituents (phenyl and acetylene groups) to introduce molecular interactions with nanotube sidewalls into the chemical reaction process for defect formation. Single defect emissions of ~1230–1270 nm selectively appeared in the functionalized chiral SWCNTs, showing a different binding configuration from those observed for typical aryl- or alkyl- functionalized chiral tubes emitting approximately 1150-nm PL. Moreover, the acetylene-based substituent design allows PL brightening and subsequent molecular modification using click chemistry.