Oxygen-doped carbon nanotubes for near-infrared fluorescent labels and imaging probes

Masako Yudasaka,Toshiya Okazaki,Tsukasa Takeuchi,Jaeho Kim,Hajime Sakakita,Yoko Iizumi

doi:10.1038/s41598-018-24399-8

Masako Yudasaka, Toshiya Okazaki + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-24399-8

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Abstract

Chemical modification of carbon nanotube surface can controllably modulate their optical properties. Here we report a simple and effective synthesis method of oxygen-doped single-walled carbon nanotubes (o-SWCNTs), in which a thin film of SWCNTs is just irradiated under the UV light for a few minutes in air. By using this method, the epoxide-type oxygen-adducts (ep-SWCNTs) were produced in addition to the ether-type oxygen-adducts (eth-SWCNTs). The Treated (6, 5) ep-SWCNTs show a red-shifted luminescence at ~1280 nm, which corresponds to the most transparent regions for bio-materials. Immunoassay, fluorescence vascular angiography and observation of the intestinal contractile activity of mice were demonstrated by using the produced o-SWCNTs as infrared fluorescent labels and imaging agents.

Highlights

Since single-walled carbon nanotubes (SWCNTs) have diameters of 1–2 nm and lengths of several micrometers, and their optical properties show unique one-dimensional aspects[1] such as optical transitions between van Hove singularities[2], large exciton effects[3] and length-dependent plasmon absorptions[4]
We reported on a simple and efficient fabrication method of o-SWCNTs
Ultra-violet irradiation on the SWCNT thin film with a conventional UV-ozone cleaner led to sufficient amounts of o-SWCNTs for a few minutes

Summary

Introduction

Since single-walled carbon nanotubes (SWCNTs) have diameters of 1–2 nm and lengths of several micrometers, and their optical properties show unique one-dimensional aspects[1] such as optical transitions between van Hove singularities[2], large exciton effects[3] and length-dependent plasmon absorptions[4]. Covalent doping of the nanotube surface with a low concentration of oxygen atoms is an effective method of controlling nanotube optical properties[10,12,13]. A comparison of the experimental observations with the calculated energy shifts suggests that the ether-type oxygen adducts (eth-SWCNTs) are mainly produced with this solution method[10,13]. The o-SWCNTs fabricated with this method show two PL peaks, indicating that the epoxide-type oxygen adducts (ep-SWCNTs) are produced as well as eth-SWCNTs15,16. This method provides an easy route toward fabrication of photostable o-SWCNTs in solid-state matrices, it may not be easy to fabricate them in large quantities.

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