In Situ Raman Spectroelectrochemical Study of ¹³C‐Labeled Fullerene Peapods and Carbon Nanotubes

Abstract C₆₀ fullerene peapods and double‐walled carbon nanotubes (DWCNTs) containing highly ¹³C enriched C₆₀ and inner tubes, respectively, are studied using Raman spectroscopy and in situ Raman spectroelectrochemistry in order to follow the influence of ¹³C enrichment on the vibrational pattern of these carbon nanostructures. The Raman response of ¹³C₆₀ after encapsulation in fullerene peapods differs from that of isotope‐natural species, ^NatC₆₀. The Raman A_g(2) mode of encapsulated ¹³C₆₀ is upshifted in frequency compared to that of the ^NatC₆₀ peapods with the same filling factor. The chemical doping of ¹³C₆₀ peapods (peapod=C₆₀@SWCNT) with K‐vapor leads to the downshift of the A_g(2) mode, similar to the case of ^NatC₆₀ peapods. The ¹³C₆₀ peapods were successfully transformed into DWCNTs, which confirms high filling of single‐walled (SW) CNTs with ¹³C₆₀. The DWCNTs exhibited distinctly downshifted G and D Raman modes for inner tubes, which proves that only inner tubes were enriched by ¹³C. The in situ Raman spectroelectrochemistry of ^NatC₆₀ exhibits strong anodic enhancement, while for ¹³C₆₀ peapods the enhancement is only weak. On the other hand, the electrochemical charging of the inner‐tube‐labeled DWCNTs (¹³C_i‐DWCNTs) followed the behavior of ordinary ^NatC_i‐DWCNTs as indicated by in situ Raman spectroelectrochemistry. In addition, the spectroelectrochemical behavior of the G mode of inner tubes in ¹³ C_i‐DWCNTs is followed from the start of the electrochemical doping, which was not feasible for ^NatC_i‐DWCNTs.