Opening of large band gap in metallic carbon nanotubes by mannose functionalized dendrimers: Experiments and theory

TL;DR

This study demonstrates experimentally and theoretically that wrapping metallic carbon nanotubes with mannose-functionalized dendrimers induces a significant metal-to-semiconductor transition with a large band gap of about 0.45 eV.

Contribution

It provides the first direct experimental evidence of supramolecular control over band gap opening in single-walled carbon nanotubes using functionalized dendrimers, supported by detailed theoretical modeling.

Findings

Measured a band gap of ~0.45 eV in SWNT-DM complexes.

Confirmed semiconductor behavior through STS, FET, and Raman spectroscopy.

Theoretical calculations attribute band gap opening to asymmetric strain from complexation.

Abstract

Despite many theoretical schemes, the direct experimental observation of supramolecular control on band gap opening in single-walled carbon nanotubes (SWNT) is still lacking. We report experimental and theoretical demonstration of metal to semiconductor transition with precisely measured large band gap in SWNTs due to the wrapping of mannose functionalized poly (propyl ether imine) dendrimer (DM) molecules. Semiconductor behaviour of SWNT-DM complex is comprehensively established with a band gap value of ~ 0.45 eV measured using scanning tunnelling spectroscopy (STS), ionic liquid top gated field effct transistor (FET) characteristics and Raman spectroscopy. Further, a validated molecular picture of SWNT-DM complex obtained from fully atomistic molecular dynamic (MD) simulations was used to carry out ab-initio density functional theory (DFT) and GW calculations of the electronic structure, evaluating experimentally estimated band gap value. We attribute this large band gap opening in SWNTs to the complexation induced asymmetric strain developed in the carbon-carbon bond length.