  Photoluminescent carbon nanotubes are expected to become versatile
room-temperature single-photon sources that have applications in quantum
information processing. Quantum emission from carbon nanotubes is often induced
by localization of excitons or exciton-exciton annihilation. Here, we modify
the local energy landscape of excitons by decorating nanoscale pentacene
particles onto air-suspended single-walled carbon nanotubes. Directional
exciton diffusion from the undecorated region to the decorated site is
demonstrated, suggesting exciton trapping induced by local dielectric screening
from pentacene particles. Photoluminescence and photon correlation measurements
on a representative carbon nanotube reveal enhanced exciton-exciton
annihilation and single-photon emission at room temperature. Pentacene
particles are shown to promote strong photon antibunching at the decorated
site, indicating that noncovalent functionalization using molecules can be an
effective approach for energy landscape modification and quantum emission in
carbon nanotubes.
