Ferrocene encapsulation in carbon nanotubes: Various methods of filling and investigation

Abstract

One of the most exciting properties of carbon nanotubes is their ability to encapsulate molecular species in their quasi-one dimensional channels. We present results on single-walled carbon nanotubes filled with ferrocene, the most stable and commercially available metallocene. For encapsulation of the ferrocene molecules we attempted two types of filling: a high temperature vapor-phase method and nano-extraction from ethanol. To confirm the encapsulation, double-walled carbon nanotubes were created from the samples by annealing. The inner tubes could be detected by Raman scattering via their radial breathing mode. These experiments confirmed that only the high-temperature annealing method was successful. The product was characterized by infrared attenuated total reflection (IR-ATR), Raman, ultraviolet-visible (UV-VIS) and Mössba-uer spectroscopy. By the latter method other iron-containing phases were observed. Mössbauer spectra proved that no charge transfer occurs between the nanotube and the ferrocene molecules.

Adsorption of Ferrocene on Carbon Nanotubes, Graphene, and Activated Carbon

“…Before metallocenes or other adsorbates could be introduced into CNTs, the nanotubes had to be opened by burning them at 440–570 °C for 20–30 min. ,,− Subsequently, the nanotubes were subjected to metallocenes in the liquid or vapor phase and heated to 100–200 °C under vacuum for 24 h to remove any exterior adsorbed metallocene . An alternative but still demanding method of opening the ends of the nanotubes to expose the interior by treatment with nitric acid has been described …”

Advances in tailoring the electronic properties of single-walled carbon nanotubes

“…x N@C 80 [277][278][279]), exohedral fullerenes (complex compounds of С 60 with Re and Os carbonyls) [280][281][282] and functionalized fullerenes (Sc 3 N@C 80 with organic groups [277] and C 60 with an organic complex compound of cadmium [283]), metallocenes (ferrocene) [258,284], metal acetylacetonates (acetylacetonates of platinum (II) [266,270] and cobalt (II) [285]) and other molecules (porphyrin complex compounds of zinc (II) and platinum (II) [286,287], rhodamine [287], chlorophyll [287], -carotene [288,289]) ( Table 1). The filling of the SWCNT channels with solutions of metal halogenides 71 (FeCl 3 [290,291], RuCl 3 [6], PtCl 4 [19]), metal nitrates (AgNO 3 [19,22,46,293,294,296], Cu(NO 3 ) 2 [293,295], Bi(NO 3 ) 3 [20], UO 2 (NO 3 ) 2 [45]) and metal acetates (UO 2 (CH 3 COO) 2 [45]) with further chemical transformation of salts (see section 5.2.5) allowed synthesizing metallic nanoparticles inside the SWCNT channels.…”

Synthesis and Properties of Single-Walled Carbon Nanotubes Filled with Metal Halogenides and Metallocenes

“…In a typical experiment, the SWCNTs were mixed with the powder of substances, sealed in an ampoule under vacuum, and heated at low temperatures (50-200°C) during several days. This method allowed filling SWCNTs with ferrocene [44,[76][77][78][79][80][81][82][83][84][85][86], cobaltocene [87,88], nickelocene [89][90][91][92], and cerocene [93,94]. It should be noted that ferrocene was also incorporated inside SWCNTs by the liquid phase method using its solution in acetone [95].…”