Metal nanoparticles decorated single-walled carbon nanotubes (SWNTs) can lead to considerable enhancement in sensing performance towards different gas analytes, however the sensing mechanism was not clearly elucidated. The detailed sensing mechanism of hybrid gold-SWNT nanostructures toward hydrogen sulfide was investigated using field effect transistor (FET) transfer characteristics. At low H 2 S concentrations ( 100 ppb V ), FET transfer characteristics show that the gold nanoparticles at the surface of SWNTs acted as nano-Schottky barriers to predominately modulate transconductance upon exposure to unfunctionalized SWNTs on gold electrodes which showed little or no response upon exposure. Although the sensitivity of Au/SWNT toward H 2 S was strongly dependent upon the size and number of gold nanoparticles, the sensing mechanism was independent of it.

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The universal binding energy relation (UBER), derived earlier to describe the cohesion between two rigid atomic planes, does not accurately capture the cohesive properties when the cleaved surfaces are allowed to relax. We suggest a modified functional form of UBER that is analytical and at the same time accurately models the properties of surfaces relaxed during cleavage. We demonstrate the generality as well as the validity of this modified UBER through first-principles density functional theory calculations of cleavage in a number of crystal systems. Our results show that the total energies of all the relaxed surfaces lie on a single (universal) energy surface, that is given by the proposed functional form which contains an additional length-scale associated with structural relaxation. This functional form could be used in modelling the cohesive zones in crack growth simulation studies. We find that the cohesive law (stress-displacement relation) differs significantly in the case where cracked surfaces are allowed to relax, with lower peak stresses occurring at higher displacements.

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Carbon Nanotubes based sensors are gammg popularity due to their high selectivity, sensitivity, fast response and recovery time, low operating temperatures and low power