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We have examined the conductive properties of carbon nanotube based thin films, which were prepared via dispersion in water by non-covalent functionalization of the nanotubes with xylan, a type of hemicellulose. Measurements of low temperature conductivity, Kelvin probe force microscopy, and high frequency (THz) conductivity elucidated the intra-tube and inter-tube charge transport processes in this material. The measurements show excellent conductive properties of the as prepared thin films, with bulk conductivity up to 2000 S cm. The transport results demonstrate that the hemicellulose does not seriously interfere with the inter-tube conductance.

The physical adsorption (physisorption) of proteins to surfaces is an important but incompletely understood factor in many biological processes and is of increasing significance in bionanotechnology as well. Avidin is an important protein because of strong avidin–biotin binding, which has been exploited in numerous applications. We have undertaken thorough experimentation on the physisorption of avidin, to chemically different flat surfaces of Si and graphite and also to the curved version of the latter, on multiwalled carbon nanotubes (MWNTs) of different diameters. The difference in the behavior of avidin on Si versus graphite is drastic; on Si, avidin deposits as single globular tetrameric units and maintains functionality, whereas on graphite, it forms irregular networks of two-layer thick filaments, where the first layer has lost its biological activity. On MWNTs, avidin also deposits as one-dimensional formations, or stripes, but these appear to order in a perpendicular arrangement to the MWNT axis. A better understanding of protein–surface interactions is essential for the development of robust and reliable methods for biofunctionalization of materials. This work also provides insights into the importance of the nanoscale surface architecture.

Merging biological and non-biological matter to fabricate nanoscale assemblies with controllable motion and function is of great interest due to its potential application, for example, in diagnostics and biosensing. Here, we have constructed a DNA-based bionanoactuator that interfaces with biological and non-biological matter via an electric field in a reversibly controllable fashion. The read-out of the actuator is based on motion-induced changes in the plasmon resonance of a gold nanoparticle immobilized to a gold surface by single stranded DNA. The motion of the gold nanoparticle and thus the conformational changes of the DNA under varying electric field were analyzed by dark field spectroscopy. After this basic characterization, another actuator was built utilizing hairpin-DNA coated gold nanoparticles, where the hairpin-DNA induced discrete transitions between two specific open-loop and folded-loop states. These two states and the transition dynamics between them were clearly visible in the actuator behavior. The demonstrated nanoactuator concept could be readily extended to inspection of conformational changes of other biomolecules as well. Besides, this concept enables other possibilities in applications like surface-enhanced Raman spectroscopy and fluorescence enhancement, since the specific wavelength of the plasmon resonance of the actuator can be tuned by the external voltage.

Abstract.To study the deformation behavior of the nanorods and further explore the deformation difference among nanorods, nanowires and bulk materials, the uniaxial tension of aluminum nanorod under different stretching rate was conducted by the molecular dynamics method. The effect of stretching rate on the tensile deformation of nanorod was investigated by considering the variation of the energy, engineering stress, yield stress, Youngs modulus changes with the strain. Further the deformation mechanism was discussed based on the study of the snapshots of the microstructure transformaiton at different stages. It was found that, when the stretching rate is under 9.26×10 9 s -1 , the deformation behavior of the aluminum nanorod was similar with that of aluminum nanowire and crystal at room temperature, and presents one necking fracture mechanism. We can obtain high yield strength and yield strain. However, when the strain rate exceeding 9.26×10 9 s -1 , the nanorod fractured near the boundaries and presents two necking mechanism, which is greatly different with that of the nano-wire or bulk materials.