Carbon nanotubes dispersed in aqueous solution by ruthenium(ii) polypyridyl complexes

Abstract

Cationic ruthenium(II) polypyridyl complexes with appended pyrene groups have been synthesized and used to disperse single-walled carbon nanotubes (SWCNT) in aqueous solutions. To this end, planar pyrene groups enable association by means of π-stacking onto carbon nanotubes and, in turn, the attachment of the cationic ruthenium complexes. Importantly, the ionic nature of the ruthenium complexes allows the formation of stable dispersions featuring individualized SWCNTs in water as confirmed in a number of spectroscopic and microscopic assays. In addition, steady-state photoluminescence spectroscopy was used to probe the excited state interactions between the ruthenium complexes and SWCNTs. These studies show that the photoluminescence of both, that is, of the ruthenium complexes and of SWCNTs, are quenched when they interact with each other. Pump-probe transient absorption experiments were performed to shed light onto the nature of the photoluminescence quenching, showing carbon nanotube-based bands with picosecond lifetimes, but no new bands which could be unambigously assigned to photoinduced charge transfer process. Thus, from the spectroscopic data, we conclude that quenching of the photoluminescence of the ruthenium complexes is due to energy transfer to proximal SWCNTs.

A Diethyleneglycol‐Pyrene‐Modified Ru(II) Catalyst for the Design of Buckypaper Bioelectrodes and the Wiring of Glucose Dehydrogenases

“…As shown in Figure A, the addition of RuPEG to a suspension of MWCNTs improved the dispersion of MWCNTs after sonication for 10 min and centrifugation, underlining the surfactant properties of the Ru complex towards MWCNTs. Improved solubility of modified CNTs has already been demonstrated using polypyridyl‐ruthenium complexes bearing pi‐extended ligands and pyrene anchors but never with a diethyleneglycol chain which can improve the hydrophilicity and biocompatibility of the formed CNT composite. Thus, highly stable and flexible BPs could be obtained following vacuum filtration of a 6 mg mL −1 RuPEG ‐modified MWCNTs dispersion onto a PTFE membrane.…”

The development of anticancer ruthenium(ii) complexes: from single molecule compounds to nanomaterials

“…Multi-walled carbon nanotubes ( MWCNT ) contain several graphene sheets, leading to multiple concentric tubes of different diameters. 295,296 Carbon nanotubes have unique properties that make them a highly promising system for biomedical application, as they can be used to deliver therapeutic drugs and diagnostic agents into cells. 297,298 However, carbon nanotubes can also absorb light in the near-infrared region as photosensitizers and can kill cancer cells by localized photothermal effects.…”