Mechanical response of metal nanowires has recently attracted a lot of interest due to their ultra-high strengths and unique deformation behaviours. Atomistic simulations have predicted that face-centered cubic metal nanowires deform in different modes depending on the orientation between wire axis and loading direction. Here we report, by combination of in situ transmission electron microscopy and molecular dynamic simulation, the conditions under which particular deformation mechanisms take place during the uniaxial loading of [110]-oriented Au nanowires. Furthermore, by performing cyclic uniaxial loading, we show reversible plastic deformation by twinning and consecutive detwinning in tension and compression, respectively. Molecular dynamics simulations rationalize the observed behaviours in terms of the orientation-dependent resolved shear stress on the leading and trailing partial dislocations, their potential nucleation sites and energy barriers. This reversible twinning–detwinning process accommodates large strains that can be beneficially utilized in applications requiring high ductility in addition to ultra-high strength.

We have investigated the electronic structure of capped carbon nanotubes under electric fields by density functional calculations. The calculated effective work function of the capped armchair nanotubes decreases linearly with increasing electric fields, whereas that of the metal tip decreases quadratically. We analyzed the density of states, highest occupied molecular orbitals (HOMO’s) and lowest unoccupied molecular orbitals (LUMO’s) for various charged states under electric fields. While the HOMO and the LUMO are not localized at the cap for a neutral state, the HOMO and LUMO of a negatively charged state are localized at the cap, particularly under electric fields. This localization plays an important role in the field emission. The Mulliken charge population shows that the charge accumulation is not dependent on the local atomic geometry but on the sharpness of the tip.

We report an ultrasensitive and selective single nanowire‐on‐film (SNOF) surface‐enhanced resonance Raman scattering (SERRS) sensor for Hg²⁺ detection based on structure‐switching double stranded DNAs (dsDNAs). Binding of Hg²⁺ induces conformational changes of the dsDNAs and let a Raman reporter get close to the SNOF structure, thereby turning on SERRS signal. The well‐defined SNOF structure provides a detection limit of 100 pM with improved accuracy in Hg²⁺ detection. This sensor is stable over a considerable amount of time and reusable after simple treatment. Since this SNOF sensor is composed of a single Au NW on a film, development of a multiplex sensor would be possible by employing NWs modified by multiple kinds of aptamers.