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

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.

Synthesis of “Dahlia-Like” Hydrophilic Fluorescent Carbon Nanohorn as a Bio-Imaging PROBE

“…The fluorescence of HFCNH in the visible region can be attributed to the fluorescent centers produced from defects (oxygen or nitrogen functional groups) in sp 2 carbon of NCNR during chemical oxidation. This result is similar to that produced by the introduction of the defect structure in the nanodiamonds, resulting in bright fluorescence emission [31,32,33]. It has been proved that the functionalization of carbon materials with polar functional groups not only improves the water solubility, but also makes the energy trapping sites more emissive [34].…”

Creating fluorescent quantum defects in carbon nanotubes using hypochlorite and light

“…Such intentionally doped nanotubes have been used to construct the first room temperature single-photon source emitting at telecom wavelengths 13–15 , a key step for the development of quantum communications and cryptography 16,17 . The nanotube quantum defects are either ether-bridged oxygen atoms 18–20 , which leave all carbon atoms sp 2 -hybridized, or organic addends 21–23 , which convert nanotube atoms from sp 2 to sp 3 hybridization at the functionalization sites. Besides the ether conformation, oxygen doping is also known to generate epoxide adducts, which are less stable than the ether-bridged structures 18,24 .…”

“…Unlike pristine SWCNTs, those with sparse doping show significant Stokes shifts between their SWIR absorption and emission bands. This property allows bioimaging with SWIR excitation, reducing excitation scattering and suppressing autofluorescence from biological tissues 18,20 . The fluorescent quantum defects also brighten ultrashort SWCNTs 25 , which have potential biomedical advantages because of their size 26–28 but are otherwise nonemissive because of end quenching 25,29 .…”

Size-controlled bimodal in vivo nanoprobes as near-infrared phosphors and positive contrast agents for magnetic resonance imaging

“…A window that combines NIR-II and NIR-III is also collectively referred to as over 1000 nm wavelength near-infrared (OTN-NIR) window [12,18]. Various OTN-NIR probes, including NIR organic dye-loaded polymer micelles [17], singlewalled carbon nanotubes [19][20][21][22], Ag 2 S-based semiconductor quantum dots (QDs) [23,24], and rareearth-doped ceramic NPs (RED-CNPs) [25,26], have been demonstrated to be applicable in the in vivo bioimaging of deep tissues. Among these OTN-NIR nanoprobes, RED-CNPs are promising multimodal agents owing to their narrow spectral lines, high photostability, low toxicity, and long NIR luminescence lifetimes [27,28].…”