Triphenylphosphine Oxide: A Versatile Covalent Functionality for Carbon Nanotubes

Abstract

Broadening the scope of functionalities that can be covalently bound to single‐walled carbon nanotubes (SWCNTs) is crucial for enhancing the versatility of this promising nanomaterial class in applied settings. Here we report the covalent linkage of triphenylphosphine oxide [Ph3P(O)] to SWCNTs, a hitherto overlooked surface functionality. We detail the synthesis and structural characterization of a new family of phosphine oxide‐functionalized diaryliodonium salts that can facilitate direct Ph3P(O) transfer and afford novel SWCNTs with tunable Ph3P(O) content (SWCNT‐P). The molecularly‐distributed and robust nature of the covalent Ph3P(O) attachment in SWCNT‐P was supported by a combination of characterization methods including Raman, infrared, UV‐Vis‐NIR and X‐ray photoelectron spectroscopies coupled with thermogravimetric analysis. Electron microscopy further revealed the effectiveness of the Ph3P(O) moiety for de‐bundling SWCNTs to yield SWCNT‐P with superior dispersibility and processability. Finally, electrochemical studies established that SWCNT‐P is sensitive to the presence of Li+, Na+ and K+ wherein the Gutmann‐Beckett Lewis acidity parameters of the ions were quantitatively transduced by Ph3P(O) to electrochemical responses. This work hence presents a synthetic, structural, spectroscopic and electrochemical foundation for a new phosphorus‐enriched responsive nanomaterial platform featuring the Ph3P(O) functionality.