Fig. 6

Applications of carbon nanotubes (CNTs) as biosensors. A The plant serves as a fluidic device and an environmental sampler. Water and other analytes are carried by the roots into the stem and toward the leaf tissues via the plant vasculature when the leaves transpire. Bombolitin II-modified single-walled carbon nanotubes (B-SWCNTs), serving as an active sensor, and polyvinyl alcohol-modified SWNCTs (P-SWCNTs), serving as a reference sensor, infiltrate the leaves via the abaxial surface on each side of the leaf midrib [206]. B After infiltration, SWCNTs are found within the leaf parenchyma tissues, as evidenced by the fluorescence detected when the leaf was excited at 785 nm. Scale bar = 0.2 mm [206]. C Because of the nanomaterial carbon lattice, analyte interaction with SWCNT sensors generates fluctuations in near-infrared (NIR) fluorescence intensity or wavelength shifts. H₂O₂ monitoring in vivo was accomplished using SWCNT NIR fluorescence intensity fluctuations in Arabidopsis leaf slices with high spatial (> 0.5 m) and temporal (> 0.5 s) resolution [208]. D Plant leaves embedded with SWCNTs act as nitroaromatic detectors, such as for picric acid. Internal controls consist of P-SWCNTs (black arrows), whereas B-SWCNTs (red arrows) monitor picric acid in real time with high spatiotemporal resolution [206]. E Plant subcellular sensors based on smart nanobiotechnology can monitor plant chemical signaling using phenotyping technology, which could aid in the selection of desirable plant features for high yield and stress tolerance [211]