Structural and morphological features of concentric iron oxide/carbon nanotubes obtained from phospholipids
Biologically active 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) nanotube-forming phospholipids (PLs) have been utilized as templates to prepare ferromagnetic nanotubes (FMNTs). Combining X-ray diffraction (XRD), selected area electron diffraction (SAD), high-resolution transmission electron microscopy (HRTEM), Raman, and Mossbauer spectroscopy measurements, FMNTs morphological features and chemical composition were determined. These studies showed that FMNTs consist of iron oxide/carbon/iron oxide concentric nanotubes with the amorphous carbon phase sandwiched between two iron oxide layers. The iron oxide phase consists of nanocrystalline magnetite (Fe3O4) which coexist as tetrahedral Fe3+ and octahedral Fe2.5+ sites containing minute quantities of hematite (alpha-Fe2O3) phase. The carbon phase consists of amorphous carbon forming an amorphous carbon nanotube (ACNT). Magnetic measurements showed that saturation magnetization (M-s) of FMNTs is 79 emu/g, but upon removal of the iron oxide outer and inner layers, ACNTs become paramagnetic. The electrical resistivity (rho) of single FMNT is 3.3 x 10(-2) Omega.m, which decreases to 5.06 x 10(-4) Omega.m for ACNT. These magneto-electric properties can be easily tailored, depending upon desired applications and needs.