Efficient near-infrared up-conversion photoluminescence in carbon nanotubes.

Naoto Akizuki,Shinichiro Mouri,Kazunari Matsuda,Yuhei Miyauchi,Shun Aota

doi:10.1038/ncomms9920

Abstract

Photoluminescence phenomena normally obey Stokes' law of luminescence according to which the emitted photon energy is typically lower than its excitation counterparts. Here we show that carbon nanotubes break this rule under one-photon excitation conditions. We found that the carbon nanotubes exhibit efficient near-infrared photoluminescence upon photoexcitation even at an energy lying >100–200 meV below that of the emission at room temperature. This apparently anomalous phenomenon is attributed to efficient one-phonon-assisted up-conversion processes resulting from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states. These findings may open new doors for energy harvesting, optoelectronics and deep-tissue photoluminescence imaging in the near-infrared optical range.

Highlights

Photoluminescence phenomena normally obey Stokes’ law of luminescence according to which the emitted photon energy is typically lower than its excitation counterparts
The observed phenomena are attributed to efficient excitonic up-conversion processes gaining energy by absorbing high-energy (B100–200 meV) optical phonons characteristic in carbon nanotubes, the phonon energy much exceeds the ambient thermal energy and corresponding phonon number available for the up-conversion is considerably small
This apparently anomalous process stems from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states

Summary

Introduction

Photoluminescence phenomena normally obey Stokes’ law of luminescence according to which the emitted photon energy is typically lower than its excitation counterparts. We found that the carbon nanotubes exhibit efficient near-infrared photoluminescence upon photoexcitation even at an energy lying 4100–200 meV below that of the emission at room temperature This apparently anomalous phenomenon is attributed to efficient one-phononassisted up-conversion processes resulting from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states. The observed phenomena are attributed to efficient excitonic up-conversion processes gaining energy by absorbing high-energy (B100–200 meV) optical phonons characteristic in carbon nanotubes, the phonon energy much exceeds the ambient thermal energy (only B26 meV) and corresponding phonon number available for the up-conversion is considerably small This apparently anomalous process stems from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states. These findings may lead to new opportunities for near-infrared and thermal energy harvesting, optoelectronics and deep-tissue up-conversion photoluminescence imaging using conventional silicon-based image sensors and low-cost nearinfrared light sources

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Results

Conclusion