Creating fluorescent quantum defects in carbon nanotubes using hypochlorite and light

Ching-Wei Lin,R Bruce Weisman,Shengnan Huang,Sergei M Bachilo,Angela M Belcher,Uyanga Tsedev,Yu Zheng

doi:10.1038/s41467-019-10917-3

Ching-Wei Lin, R Bruce Weisman + Show 5 more

Open Access

https://doi.org/10.1038/s41467-019-10917-3

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Abstract

Covalent doping of single-walled carbon nanotubes (SWCNTs) can modify their optical properties, enabling applications as single-photon emitters and bio-imaging agents. We report here a simple, quick, and controllable method for preparing oxygen-doped SWCNTs with desirable emission spectra. Aqueous nanotube dispersions are treated at room temperature with NaClO (bleach) and then UV-irradiated for less than one minute to achieve optimized O-doping. The doping efficiency is controlled by varying surfactant concentration and type, NaClO concentration, and irradiation dose. Photochemical action spectra indicate that doping involves reaction of SWCNT sidewalls with oxygen atoms formed by photolysis of ClO− ions. Variance spectroscopy of products reveals that most individual nanotubes in optimally treated samples show both pristine and doped emission. A continuous flow reactor is described that allows efficient preparation of milligram quantities of O-doped SWCNTs. Finally, we demonstrate a bio-imaging application that gives high contrast short-wavelength infrared fluorescence images of vasculature and lymphatic structures in mice injected with only ~100 ng of the doped nanotubes.

Highlights

Covalent doping of single-walled carbon nanotubes (SWCNTs) can modify their optical properties, enabling applications as single-photon emitters and bio-imaging agents
It has been shown that single-wall carbon nanotubes (SWCNTs) with some types of sparse covalent doping give spectrally shifted emission arising from the trapping of mobile excitons at the defect sites
We describe a simple continuous flow reactor for efficiently preparing O-doped SWCNTs and demonstrate sensitive in vivo imaging in mice using short-wave infrared (SWIR) fluorescence from our doped samples

Summary

Introduction

Covalent doping of single-walled carbon nanotubes (SWCNTs) can modify their optical properties, enabling applications as single-photon emitters and bio-imaging agents. It has been shown that SWCNTs with some types of sparse covalent doping give spectrally shifted emission arising from the trapping of mobile excitons at the defect sites. Such intentionally doped nanotubes have been used to construct the first room temperature single-photon source emitting at telecom wavelengths[13,14,15], a key step for the development of quantum communications and cryptography[16,17]. We report here a simple, quick, and controllable way to efficiently generate oxygen-doped SWCNTs. Surfactant-suspended nanotubes in the presence of NaClO (bleach) are irradiated in the near-UV to induce photodissociation of ClO− and form the desired doped. We describe a simple continuous flow reactor for efficiently preparing O-doped SWCNTs and demonstrate sensitive in vivo imaging in mice using SWIR fluorescence from our doped samples

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