Optical detection of individual ultra-short carbon nanotubes enables their length characterization down to 10 nm.

Zhenghong Gao,Romain Faes,Philippe Poulin,Brahim Lounis,Christèle Jaillet,Fabien Moroté,Laura Oudjedi,Laurent Cognet

doi:10.1038/srep17093

Abstract

Ultrashort single-walled carbon nanotubes, i.e. with length below ~30 nm, display length-dependent physical, chemical and biological properties that are attractive for the development of novel nanodevices and nanomaterials. Whether fundamental or applicative, such developments require that ultrashort nanotube lengths can be routinely and reliably characterized with high statistical data for high-quality sample production. However, no methods currently fulfill these requirements. Here, we demonstrate that photothermal microscopy achieves fast and reliable optical single nanotube analysis down to ~10 nm lengths. Compared to atomic force microscopy, this method provides ultrashort nanotubes length distribution with high statistics, and neither requires specific sample preparation nor tip-dependent image analysis.

Highlights

Atomic force microscopy (AFM) are the most commonly employed techniques for morphological characterization of nanostructures including nanotubes
We demonstrate that photothermal imaging (PhI) allows the robust detection of Ultrashort single-walled carbon nanotubes (usCNTs) down to the range of 10 nm length and we show that the measured PhI signal amplitudes are proportional to nanotube lengths
In order to obtain non-functionalized usCNTs, Dai et al proposed an approach based on heavy sonication of fluorescein-polyethylene glycol coated SWCNTs26

Summary

Introduction

Atomic force microscopy (AFM) are the most commonly employed techniques for morphological characterization of nanostructures including nanotubes. An absorption cross-section of 3.2 × 10−17 cm2/C atom was precisely determined for (6,5) nanotubes at their second-order optical transition (S22)[18] Such direct absorption measurements performed on single SWCNTs are arduous because the weak signals have to be extracted from laser intensity fluctuations and contributions from environment scattering. Considering the case of a small diameter 10 nm long (6, 5) SWCNT excited at its S22 resonance, a simple calculation would indicate an absorption cross-section of the order of a few 10−14 cm[2] This simple calculation raises the question whether PhI might provide a quantitative measure of usCNT lengths in different sample preparations. By comparison with AFM, we demonstrate that PhI microscopy reliably provides fast characterization of usCNT samples with higher statistics

Methods

Results

Discussion

Conclusion