Optical Properties of Ultrashort Semiconducting Single-Walled Carbon Nanotube Capsules Down to Sub-10 nm

TL;DR

This study demonstrates the production and optical characterization of ultrashort single-walled carbon nanotubes, revealing quantum confinement effects and their potential as quantum dot-like structures.

Contribution

The paper introduces a method to produce and separate ultrashort SWNTs down to 7.5 nm and investigates their optical properties, highlighting quantum confinement effects.

Findings

Ultrashort SWNTs exhibit a blue shift in optical peaks.

Length separation achieved via density gradient ultracentrifugation.

Ultrashort SWNTs behave as quantum dot-like structures.

Abstract

Single-walled carbon nanotubes (SWNTs) are typically long (>100 nm) and have been well established as novel quasi one-dimensional systems with interesting electrical, mechanical, and optical properties. Here, quasi zero-dimensional SWNTs with finite lengths down to the molecular scale (7.5 nm in average) were obtained by length separation using a density gradient ultracentrifugation method. Different sedimentation rates of nanotubes with different lengths in a density gradient were taken advantage of to sort SWNTs according to length. Optical experiments on the SWNT fractions revealed that the UV-vis-NIR absorption and photoluminescence peaks of the ultrashort SWNTs blue-shift up to 30 meV compared to long nanotubes, owing to quantum confinement effects along the length of ultrashort SWNTs. These nanotube capsules essentially correspond to SWNT quantum dots.