Abstract
Here, the ability of a novel near-infrared dye to noncovalently self-assemble onto the surface of single-walled carbon nanotubes (SWCNTs) driven by charge-transfer interactions is demonstrated. Steady-state, Raman, and transient absorption spectroscopies corroborate the electron donating character of the near-infrared dye when combined with SWCNTs, in the form of fluorescence quenching of the excited state of the dye, n-doping of SWCNTs, and reversible charge transfer, respectively. Formation of the one-electron oxidized dye as a result of interactions with SWCNTs is supported by spectroelectrochemical measurements. The ultrafast electronic process in the near-infrared dye, once immobilized onto SWCNTs, starts with the formation of excited states, which decay to the ground state via the intermediate population of a fully charge-separated state, with characteristic time constants for the charge separation of 1.5 ps and charge recombination of 25 ps, as derived from the multiwavelength global analysis. Of great relevance is the fact that charge-transfer occurs from the hot excited state of the near-infrared dye to SWCNTs.
Highlights
Several attempts were made to attach different molecular building blocks onto the surface of CNTs, such as Hybrid nanostructures consisted of a carbon nanotube (CNT) methylene blue,[14] methyl orange,[15] porphyrin,[16,17] polymcore and an organic dye shell or, vice versa, an organic dye ethine,[18] amphiphiles,[19] DNA,[20] etc
Mixtures of the NIR dye and SWCNTs in 2-propanol revealed unexpectedly good stability compared to the neat SWCNTs dispersion of the same concentration
Our results suggest that the fluorescence quenching is due to an electron transfer event between 1859 and SWCNTs once the excited state is formed
Summary
Several attempts were made to attach different molecular building blocks onto the surface of CNTs, such as Hybrid nanostructures consisted of a carbon nanotube (CNT) methylene blue,[14] methyl orange,[15] porphyrin,[16,17] polymcore and an organic dye shell or, vice versa, an organic dye ethine (astraphloxin),[18] amphiphiles (with nitrilotriacetic acid encapsulated in a CNT shell became a subject of growing or pyridinium heads),[19] DNA,[20] etc. It was clarified that the research interest in recent years.[1,2,3,4,5] CNTs are known as main mechanisms of adsorption onto CNTs depend on whether the dyes are cationic or anionic, and that possible interactions between CNTs and dyes can be due to hydrophobic, van der. As a matter of fact, efficient charge-generation and good photoconductivity of some NIR dyes gave rise to their application in photocopying (xerography),[28] laser printing,[29] and photodetecting.[30,31,32] The excellent optical properties of the employed NIR dye, along with the observed charge-transfer dye-CNT interaction, opens up a new perspective for application of this electron donor-acceptor pair in photovoltaics
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