Covalent introduction of photoluminescent defect states in carbon nanotubes is introducing new functionality such as room-temperature single photon emission^1,2 and associated novel photophysical behaviors. Harnessing defect-state emission will depend on a thorough understanding of their electronic structure^3,4 and relaxation dynamics.⁵ While providing relaxation timescales and mechanistic insight,⁵ study of photoluminescence relaxation can also be a route to obtaining complementary information on electronic structure and relaxation pathways. We present here a study of how relaxation dynamics are affected by dielectric environment. Changes in relaxation times with dielectric constant of the solvent will be discussed as evidence for an electronic to vibrational energy transfer from the defect-trapped exciton to the solvent degrees of freedom. Solvent interactions are thus seen to be an important component of relaxation that also includes multi-phonon decay processes.⁵ Wavelength-dependent changes in relaxation times provide insight into the effects of both thermal detrapping and transition oscillator strength on decay times. Wavelength dependence will also be discussed in the context of temperature-dependent relaxation measurements.

References

1. Ma, X. et al.; Nat. Nanotechnol., 10, 671 (2015).
2. He, X. et al.; Nat. Photon., 11, 577 (2017).
3. Ma, X. et al.; ACS Nano, 8, 10782 (2014).
4. He, X. et al.; ACS Nano, DOI: 10.1021/acsnano.7b03022 (2017)
5. Hartmann, N. F. et al.; ACS Nano, 10, 8355 (2016).