Polar Express: Rapid Functionalization of Single-Walled Carbon Nanotubes in High Dipole Moment Media

TL;DR

This study explores how different solvents influence the covalent functionalization of semiconducting SWCNTs, revealing that polar solvents significantly affect their structure and optical properties, enabling improved biomedical detection.

Contribution

The paper uncovers the role of solvent environment in SWCNT functionalization and introduces a hybrid modeling approach to understand and control this process.

Findings

Polar solvents induce structural reorganization of polymer molecules on SWCNTs.

Solvent and dispersant choice affect the kinetics and course of covalent modification.

Tailored SWCNTs enable effective optical detection of cholesterol.

Abstract

Fluorescent semiconducting single-walled carbon nanotubes (SWCNTs) hold considerable promise for photonics. Furthermore, the optical characteristics of the material can be significantly improved by covalent modification, which generates new spectral features in the near-infrared region and enhances its photoluminescence quantum yield. However, despite the dynamic development of this research domain, the importance of the solvent environment in which the SWCNT functionalization is conducted remains relatively unexplored. In this work, the complex relationships between solvent, dispersant, and SWCNTs were untangled to unravel the underlying phenomena. Through a systematic investigation of SWCNT reactivity in a broad spectrum of solvents, supported by multi-scale modeling enabled by our new implementation of a hybrid functional within SIESTA, we discovered that both the solvent medium and the dispersant enabling SWCNT solubilization affect not only the kinetics but also the course of the covalent modification of SWCNTs. Polar solvents proved to induce significant structural reorganization of polymer molecules on the SWCNT surface and enhance charge redistribution at the polymer-SWCNT interface. Consequently, we achieved a high degree of control over the optical properties of SWCNTs, and the tailored SWCNTs enabled facile optical detection of cholesterol, a significant risk factor for cardiovascular diseases.