Capsulate structure effect on SWNTs doping in RbxAg1-xI@SWNT composites

Abstract

The paper reports the relationship between single-walled carbon nanotube (SWNT) doping and capsulate crystal structure in RbxAg1-xI@SWNT composites. The structures of one dimensional (1D) RbI, AgI and RbAg4I5 crystals inside single-walled carbon nanotubes were established by high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy (HAADF HRSTEM), and confirmed by image simulation. Opposite to one-dimensional RbI and AgI, inheriting the structure of bulk analogues, 1D RbAg4I5 forms a new phase within a confined space of the SWNT channel, which differs from the bulk RbAg4I5 structure and can be described by a deformed cubic 1D lattice. X-ray absorption, XPS, optical absorption and Raman spectroscopies were used for comprehensive study of the composites' electronic structures. The study reveals the donor behavior of RbI capsulate and the acceptor behavior of RbAg4I5 and AgI. Quantification of doping levels indicated the prevalence of the effect of the chemical composition of the capsulate on the overall doping efficiency, while a structural effect is mostly prominent in potential distribution on nanotube walls and partial charges on SWNT atoms.