Tailoring the Spectral Properties of Single-Wall Carbon Nanotube Samples through Structure-Selective Photochemistry

Abstract

The structural heterogeneity in mixed SWCNT samples results in extensive spectral complexity that can hamper a range of basic and applied research efforts. One approach to solving this problem is post-growth sorting, which unfortunately involves well known challenges. Here we report a photochemical strategy for spectral tailoring that uses monochromatic near-infrared (NIR) irradiation to selectively alter semiconducting (n,m) species based on their distinct and characteristic E11 optical transitions. This process does not physically isolate the targeted species, but it allows optical properties of the mixture to be modified without the need for physical separations. Our method achieves selective fluorescence quenching in aqueous dispersions of SWCNTs through irradiation of E11 transitions by NIR diode lasers in the presence of dissolved oxygen. Fluorescence emission from SWCNT species with transitions near the excitation wavelength is significantly and permanently suppressed, while the corresponding E11 absorptions are bleached and Raman D bands intensify. Results will be presented for several different oxygen headspace pressures and for wavelength-dependent irradiation data, which suggest a threshold consistent with the involvement of singlet O2. The method of near-IR photochemical tailoring may be useful for controlling SWCNT emission spectra in applications such as spectral bar-coding and strain sensing.