Ionic Liquid for in situ Vis/NIR and Raman Spectroelectrochemistry: Doping of Carbon Nanostructures

Abstract

1-butyl-3-methylimidazolium tetrafluoroborate (an ionic liquid) is an advantageous electrolyte for the study of charge-transfer reactions at single-walled carbon nanotubes (SWCNTs) and fullerene peapods (C 60 @SWCNT). Compared to traditional electrolyte solutions, this medium offers a broader window of electrochemical potentials to be applied, and favorable optical properties for in situ Vis/NIR and Raman spectroelectrochemistry of nano-carbon species. The electrochemistry of both nanotubes and peapods is dominated by their capacitive double-layer charging. Vis/NIR spectroelectrochemistry confirms the charging-induced bleaching of transitions between Van Hove singularities. At high positive potentials, new optical transitions were activated in partly filled valence band. The bleaching of optical transitions is mirrored by the quenching of resonance Raman scattering in the region of tube-related modes. The Raman frequency of the tangential displacement mode of SWCNT shifts to blue upon both anodic and cathodic charging in the ionic liquid. The Raman modes of intratubular C 60 exhibit a considerable intensity increase upon anodic doping of peapods.

Spectroelectrochemistry of Carbon Nanotubes

“…Neglecting the potentiostatic conditions [14] may cause principal errors. [14][15][16] The spectra are usually recorded at a constant applied electrode potential, but measurements were also carried out during slow potential scans [17,18] or slow galvanostatic charging. [19] The nanotube sample is usually a thin solid film on a working electrode support, such as Pt, Au, Hg, indium-tin oxide (ITO) and so forth, but a self-standing buckypaper can also be used.…”

Ionic Liquids for Soft Functional Materials with Carbon Nanotubes

“…Another advantage is a broader window of ionic liquids in applicable electrochemical potential than those of traditional electrolyte solutions, which enables electrochemical doping of carbon nanotubes. [25] Bucky-gel-modified electrodes can readily be fabricated from a variety of CNTs and ionic liquids. [26][27][28][29][30][31][32][33] For example, Dong and co-workers fabricated either gold or glassy carbon electrodes coated with a bucky gel prepared from multi-walled carbon nanotubes (MWNTs) and…”

Electronic properties of pristine and modified single-walled carbon nanotubes

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“…[177,198] [233,234,243,244] ËÎË ÕÑÐÍÖá ÒÑÎÖÒÓÑÊÓÂÚÐÖá ÒÎÈÐÍÖ ÒÎÂÕËÐÞ [247,248]. ±ÓË àÕÑÏ ËÔÒÑÎßÊÖáÕ ÓÂÔÕÄÑÓÞ àÎÇÍÕÓÑÎËÕÑÄ Ä ÄÑAEÇ [233], ÂÙÇÕÑÐËÕÓËÎÇ [234,243,247,248] ËÎË ËÑÐÐÞØ ÉËAEÍÑÔÕâØ [244]. ¢ÞÎÑ ÒÑÍÂÊÂÐÑ, ÚÕÑ AEÂÐÐÞÇ àÕËØ ËÊÏÇÓÇ-ÐËÌ ÔÑÅÎÂÔÖáÕÔâ Ô ÓÇÊÖÎßÕÂÕÂÏË, ÒÑÎÖÚÇÐÐÞÏË ÒÓË ËÔÔÎÇAEÑÄÂÐËË°³¯´, ËÐÕÇÓÍÂÎËÓÑÄÂÐÐÞØ ÂÍÙÇÒÕÑÓÂÏË Ë AEÑÐÑÓÂÏË àÎÇÍÕÓÑÐÑÄ [35,190,218,221] [ 347,348] ¬ÄÂÐÕÑÄÑ-ØËÏËÚÇÔÍËÇ ÓÂÔÚÈÕÞ ²ÂÔÚÈÕ ÊÑÐÐÑÌ ÔÕÓÖÍÕÖÓÞ ÔÄËAEÇÕÇÎßÔÕÄÖÇÕ Ñ AEÑÐÑÓÐÑÏ ÎÇÅËÓÑÄÂÐËË°³¯´.…”