Cooperative Regulation of Defect-Mediated Molecular Recognition With Single-Walled Carbon Nanotubes.

Defects are increasingly recognized as powerful modulators of the chemistry and photophysics of fluorescent single-walled carbon nanotubes (SWCNTs), enabling tunable optical responses toward exogenously introduced analytes. However, defect-mediated interactions arise not solely from defects, but from the interplay among multiple interconnected system variables, including defect type and density, analyte identity and size, corona composition and conformation, SWCNT chirality, and the surrounding environment. In this forward-looking perspective, we discuss how these variables collectively govern the fluorescence modulation and molecular recognition behavior of defect-engineered SWCNTs. We first summarize major strategies for defect introduction and recent advances in defect quantification. Subsequently, through case-by-case analyses, we examine how systematic variation of individual parameters reshapes analyte-SWCNT interactions and sensing outcomes. Specifically, we discuss systems exhibiting analyte-dependent fluorescence modulation, defect-enabled ratiometric sensing, analyte-size-dependent interactions, corona-dependent defect reactivity, and the cooperative behavior of multiple defect types within the same nanotube framework. Finally, we highlight key challenges associated with defect heterogeneity, predictability, and controllable molecular recognition, while outlining emerging opportunities involving programmable nanosensing, artificial intelligence-assisted design, and multifunctional imaging platforms. Overall, this perspective emphasizes that defect-mediated sensing in SWCNTs is fundamentally governed by the cooperative interplay of multiple system variables.