Mapping purity of single-walled carbon nanotubes in bulk samples with multiplex coherent anti-stokes Raman microscopy

Impurity mapping in a distribution of single-walled carbon nanotube (SWNT) bundles was performed via multiplex coherent anti-Stokes Raman spectroscopy (MCARS). The Dover G-bands in the SWNT´s vibrational spectrum are acquired simultaneously and used to quantify the local purity in a spin-coated sample. This technique is faster than conventional Raman microscopy, however it needs the aid of a further data processing called maximum entropy method (MEM) to retrieve the vibrational spectrum. The acquired data set allows mapping of the same spatial region selecting different spectral components. This way, the mapping of purity is performed using the ratio D/G. Additionally, a RGB like construction was performed in order to obtain information about the SWNT´s dispersion.