CNT array-induced nanobubble assembly, nanodisk fabrication and enhanced spectral detection of CNT bundle density

Alignment, functionalization and detection of carbon nanotube (CNT) bundles are vital processes for utilizing this one-dimensional nanomaterial in electronics. Here, we report a polymer-assisted wet shearing method to acquire super-aligned crater-patterned CNT arrays by nanobubble (NB) self-assembly with a “migrate and aggregation” mechanism and use craters to controllably mold even-sized nanodisks periodically along CNT bundles with tunable densities. This green, low-cost method can be extended to diverse substrates and fabricate different nanodisks. As an example, the Ag-nanodisk-patterned CNT arrays are utilized as substrates of surface-enhanced Raman scattering (SERS) for rhodamine 6G (R6G) and methylene blue (MB) in which a linear correlation is found between the SERS intensity and the CNT bundle density due to the periodic distribution of hot spots, enabling a spectral detection of CNT bundles and their densities by conventional dye molecules. Distinguishing from routine morphological characterization, this spectral method possesses an enhanced accuracy and a detection range of 0.1–2 µm⁻¹, showing its uniqueness in the detection of CNT bundle density since the intensity of traditional spectral merely relates to the quantity of CNTs, exhibiting its potential in future CNT-bundle-based electronics.