Preparation and characterization of multiwall carbon nanotube/polypyrrole coaxial fibrils

Multiwall carbon nanotube (MWNT)/polypyrrole (PPy) fibrils were fabricated by template-free in situ electrochemical deposition of PPy over MWNTs, and characterized by electron microscopy and electrical measurements. Scanning and transmission electron microscopy studies reveal that PPy coating on the surface of nanotube is quite uniform throughout the length, with the possibility of forming unique Y-junctions. Current (I)-voltage (V) characteristics at various temperatures show nonlinearity due to tunneling and hopping contributions to transport across the barriers. AC conductivity measurements (300-4.2 K) show that the onset frequency scales with temperature, and the nanoscale connectivity in MWNT/PPy fibrils decreases with the lowering of temperature.     

Molecular dynamics simulations of carbon nanotube/silicon interfacial thermal conductance

Using molecular dynamics simulations with Tersoff reactive many-body potential for Si-Si, Si-C, and C-C interactions, we have calculated the thermal conductance at the interfaces between carbon nanotube (CNT) and silicon at different applied pressures. The interfaces are formed by axially compressing and indenting capped or uncapped CNTs against 2 x 1 reconstructed Si surfaces. The results show an increase in the interfacial thermal conductance with applied pressure for interfaces with both capped and uncapped CNTs. At low applied pressure, the thermal conductance at interface with uncapped CNTs is found to be much higher than that at interface with capped CNTs. Our results demonstrate that the contact area or the number of bonds formed between the CNT and Si substrate is key to the interfacial thermal conductance, which can be increased by either applying pressure or by opening the CNT caps that usually form in the synthesis process. The temperature and size dependences of interfacial thermal conductance are also simulated. These findings have important technological implications for the application of vertically aligned CNTs as thermal interface materials.     

Microtubule dynamics regulated by stathmin

Microtubules perform a variety of functions which lead to the complex regulation of intracellular transport and cell division. However, the regulation of microtubule growth is not clearly known. Based on a recent experimental finding, we explore the possibility of spatial regulation of microtubule growth by stathmin–tubulin interaction gradients. Computer simulation of the model with stathmin–tubulin interaction gradients gave regulated growth as seen in experiments. In future, the stathmin–tubulin interaction gradients can be made dynamic and its impact on the microtubule growth can be explored.     

Electrochemical Fluorescence Switching from a Patternable Poly(1,3,4‐oxadiazole) Thin Film

A highly soluble poly(1,3,4‐oxadiazole) (POD) substituted with long alkyl chains was examined for electrochemical fluorescence switching. The high solubility of the polymers enabled a simple fabrication of an electrochemical cell, which showed reversible fluorescence switching between dark (n‐doping) and bright (neutral) states with a maximum on/off ratio of 2.5 and a cyclability longer than 1 000 cycles. Photochemical cleavage of the oxadiazole in POD allowed photo‐patterning of the POD film upon exposure to UV source. The patterned POD films displayed patterned image reversibly under a step potential of +1.8/−1.8 V.