Synthesis and electrical conductivity of perchlorate-doped TTF–diamide nanofibers with double and triple helix structures

We synthesized 4,5-bis(octadecylthio)-4[prime or minute],5[prime or minute]-bis(ethylcarbamoyl)tetrathiafulvalene and measured the electrical conductivity of its perchlorate (ClO4-)-doped nanofibers, which have double and triple helix structures. The nanostructure of the bis(octadecylthio)-TTF-diamide and its ClO4--doped fibers in a 3 : 1 ratio was deduced in relation to the X-ray crystal structure of bis(methylthio)-TTF-diamide. The doubly coiled nanofibers form when initially formed spiral ribbons of lamellarly arranged TTF-diamide perchlorate split in the middle, and a further split of the double helix produces the triplex structure. Temperature-dependent conductance and current-voltage (I-V) characteristics of the coiled fibers were measured in the temperature (T) range of 70-300 K. The conductance decreased with a decrease in T, and the I-V characteristics were nonlinear over the entire T range. The results were analyzed by using a modified fluctuation-induced tunneling conduction model, where the barrier height and width were linearly dependent on the electric field.