(Invited) Tuning the Properties of Luminescent Defects in Carbon Nanotubes for Applications

Abstract

Luminescent sp3-defects (also called quantum defects or organic color centers) in single-walled carbon nanotubes (SWCNTs) with their characteristic red-shifted emission and long photoluminescence (PL) lifetimes enable higher PL quantum yields and single-photon emission at room temperature. They can be created in a controlled manner on polymer-wrapped semiconducting nanotubes via diazonium chemistry in organic solvents with a variety of functional substituents [ACS Nano 2019, 13, 9259]. Here we show, how attaching the stable and neutral perchlorotriphenylmethyl (PTM) radical to such sp3-defects impacts their emissive properties in dispersion at room temperature as well as under strong magnetic fields at cryogenic temperatures. Furthermore, the type of defect emission (E11* or E11*-) is governed by the precise binding configuration for chiral (6,5) SWCNTs. We introduce a simple synthetic protocol to obtain exclusively the more red-shifted E11*--defect emission with even longer PL lifetime and high single-photon purity. This new functionalization method relies on nucleophilic addition instead of radical-based reactions and can be transferred to other polymer-sorted nanotubes, e.g. (7,5) and (10,5) SWCNTs. The achieved tunability and control of sp3-defect emission facilitates applications in electroluminescent devices, radiative pumping of exciton-polaritons in metal-clad microcavities [ACS Photonics 2020, DOI: 10.1021/acsphotonics.0c01129] or in-vivo imaging in the 2nd biological window.