Electronic Properties of Graphene Nanoribbon on Si(001) Substrate

We show by first-principles calculations that the electronic properties of zigzag graphene nanoribbons (Z-GNRs) adsorbed on Si(001) substrate strongly depend on ribbon width and adsorption orientation. Only narrow Z-GNRs with even rows of zigzag chains across their width adsorbed perpendicularly to the Si dimer rows possess an energy gap, while wider Z-GNRs are metallic due to width-dependent interface hybridization. The Z-GNRs can be metastably adsorbed parallel to the Si dimer rows, but show uniform metallic nature independent of ribbon width due to adsorption induced dangling-bond states on the Si surface.Comment: 13 pages, 3 figure

Dynamic hydration valve controlled ion permeability and stability of NaK channel

The K^+^, Na^+^, Ca^2+^ channels are essential to neural signalling, but our current knowledge at atomic level is mainly limited to that of K^+^ channels. Unlike a K^+^ channel having four equivalent K^+^-binding sites in its selectivity filter, a NaK channel conducting both Na^+^ and K^+^ ions has a vestibule in the middle part of its selectivity filter, in which ions can diffuse but not bind specifically. However, how the NaK channel conducts ions remains elusive. Here we find four water grottos connecting with the vestibule of the NaK selectivity filter. Molecular dynamics and free energy calculations show that water molecules moving in the vestibule-grotto complex hydrate and stabilize ions in the filter and serve as a valve in conveying ions through the vestibule for controllable ion permeating. During ion conducting, the water molecules are confined within the valve to guarantee structure stability. The efficient exquisite hydration valve should exist and play similar roles in the large family of cyclic nucleotide-gated channels which have similar selectivity filter sequences. The exquisite hydration valve mechanism may shed new light on the importance of water in neural signalling

Enhanced Gas-Flow-Induced Voltage in Graphene

We show by systemically experimental investigation that gas-flow-induced voltage in monolayer graphene is more than twenty times of that in bulk graphite. Examination over samples with sheet resistances ranging from 307 to 1600 {\Omega}/sq shows that the induced voltage increase with the resistance and can be further improved by controlling the quality and doping level of graphene. The induced voltage is nearly independent of the substrate materials and can be well explained by the interplay of Bernoulli's principle and the carrier density dependent Seebeck coefficient. The results demonstrate that graphene has great potential for flow sensors and energy conversion devices