Ordered DNA-Wrapped Single-Chirality Carbon Nanotubes Enable an Unparalleled Sensing Platform for Copper Ion Detection

Copper is an essential trace metal in living organisms, but excessive copper intake poses significant risks to plants, animals, and human health throughout the food chain. Developing a sensitive, nondestructive, and real-time technique to assess copper uptake in plants is highly desirable, yet it remains a challenging task. Here, we demonstrate that purified single-chirality carbon nanotubes (scCNTs) wrapped with a periodically ordered DNA structure provide an unparalleled platform for copper detection. By screening five distinct purified DNA-scCNT species, we identified C₃GC₆GC₄-(7,5) as the most promising candidate. It demonstrated ultrasensitive and highly selective detection of Cu²⁺ ions, with a limit of detection of 1.20 pM, and showed no interference from 13 competing ions. This system functions by efficiently adsorbing Cu²⁺ ions onto the surface of the (7,5) nanotubes through an ordered DNA wrapping structure. The electron transfer from (7,5) to Cu²⁺ significantly quenches the nanotube fluorescence. Femtosecond transient absorption (fs-TA) measurements revealed that the electron transfer occurs on a femtosecond time scale. C₃GC₆GC₄-(7,5) was successfully applied as a nanosensor for real-time, rapid, and quantitative detection of Cu²⁺ uptake in living plants. Our findings highlight the superiority of purified DNA-scCNT sensors, establishing a paradigm for next-generation nanosensors.