Ultrashort Carbon Nanotubes with Luminescent Color Centers are Bright NIR-II Nano-Emitters

TL;DR

This paper introduces ultrashort carbon nanotubes functionalized with luminescent color centers as highly bright, nanoscale NIR-II emitters suitable for deep tissue bioimaging, surpassing traditional visible emitters in brightness.

Contribution

It demonstrates that ultrashort carbon nanotubes with luminescent color centers are unexpectedly bright in NIR-II, with high quantum yields and applications in high-resolution deep tissue imaging.

Findings

Ultrashort carbon nanotubes exhibit brightness exceeding quantum dots in NIR-II.

Photoluminescence quantum yields can reach up to 20% for single nanotubes.

Nanoscale imaging in thick brain tissue achieved using these nanotubes.

Abstract

In the fields of bioimaging, photonics, and quantum science, it is equally crucial to combine high brightness with nanoscale size in short-wave infrared (SWIR) emitters. However, such nano-emitters are currently lacking. Here, we report that when functionalized with luminescent color centers, ultrashort carbon nanotubes with length much shorter than 100 nm, are surprisingly bright in the near-infrared second-biological window (NIR-II) of the SWIR domain. We discuss the origin of this exceptional brightness based on the uncontrollable presence of quenching defects in dispersed carbon nanotubes. We further investigate the nonlinear photoluminescence behavior of color centers functionalized carbon nanotubes in response to varying excitation conditions, spanning from ensemble measurements to single-nanotube experiments. We discuss how this behavior influences the determination of their photoluminescence quantum yields, which can reach values as high as 20% for ultrashort ones detected at the single nanotube level. Notably, the corresponding NIR-II brightness exceeds that of well-known visible emitters, including quantum dots. After rendering them biocompatible, we demonstrate point-spread function engineering and high-resolution, 3-dimensional single-particle tracking using these bright ultrashort carbon nanotubes allowing nanoscale imaging in the NIR-II window within thick brain tissue.