High-pressure triggered quantum tunneling tuning through classical percolation in a single nanowire of a binary composite

In the era of miniaturization,the one-dimensional nanostructures presented numerous possibilities to realize operational nanosensors and devices by tuning their electrical transport properties.Upon size reduction,the physical properties of materials become extremely challenging to characterize and understand due to the complex interplay among structures,surface properties,strain effects,distribution of grains,and their internal coupling mechanism.In this report,we demonstrate the fabrication of a single metal-carbon composite nanowire inside a diamondanvil-cell and examine the in situ pressure-driven electrical transport properties.The nanowire manifests a rapid and reversible pressure dependence of the strong nonlinear electrical conductivity with significant zero-bias differential conduction revealing a quantum tunneling dominant carrier transport mechanism.We fully rationalize our observations on the basis of a metal-carbon framework in a highly compressed nanowire corroborating a quantum-tunneling boundary,in addition to a classical percolation boundary that exists beyond the percolation threshold.The structural phase progressions were monitored to evidence the pressure-induced shape reconstruction of the metallic grains and modification of their intergrain interactions for successful explanation of the electrical transport behavior.The pronounced sensitivity of electrical conductivity to an external pressure stimulus provides a rationale to design low-dimensional advanced pressure sensing devices.

Dehydro-Diels-Alder reaction and diamondization of bowl-shaped clusters C_(18)Te_(3)Br_(4)(Bu-O)_(6)

Dehydro-Diels-Alder(DDA)reaction is a textbook reaction for preparing six-membered rings in solution but is scarcely seen in solid-state synthesis.In this work,using multiple characterization techniques,we demonstrate that the bowl-shaped clusters C_(18)Te_(3)Br_(4)(Bu-O)_(6) might experience a DDA reaction at room temperature and high pressure between 5.5 and 7.4 GPa.Above 17.0 GPa,it is found that the bonding conversion from the intramolecular sp^(2) to the intermolecular spa occurred,in the form of pressure-induced diamondization.The recovered samples from 20.0 and 36.1 GPa showed incomplete reversibility,while the decompression-induced graphitization of glassy carbon was observed during decompression from 46.5 GPa.The electrochemical impedance spectroscopy results indicated that the transport properties changed from grain boundary dominant to grain dominant due to the DDA reaction and the grain boundary effect disappeared as the intermolecular sp3 bonding building-up and carrier transmission channel formation above 17.0 GPa.The results in this study open a new route to construct the crystalline carbon materials with different transport properties.