Fabrication Of Ultra-sensitive Optical Fiber Based Humidity Sensor Using TiO2 thin Film

On the applicability of cluster models to study the chemical reactivity of carbon nanotubes

“…They found that the addition energy to the (8,8) tube was 4 kcal/mol more favorable as compared with the (14,0) SWCNT. Nevertheless, our results for the (12,12) and (20,0) SWCNTs evidence that the metallic tube is almost twice as reactive as the semiconducting tube. It is worth mentioning that the diameter of the (12,12) SWCNT is 0.5 Å longer in comparison with the (20,0) tube, supporting the larger reactivity of metallic nanotubes.…”

“…Nevertheless, our results for the (12,12) and (20,0) SWCNTs evidence that the metallic tube is almost twice as reactive as the semiconducting tube. It is worth mentioning that the diameter of the (12,12) SWCNT is 0.5 Å longer in comparison with the (20,0) tube, supporting the larger reactivity of metallic nanotubes. The adsorption energies obtained by means of infinite models show a smooth convergence towards the value computed for graphene, although this is not always the case for the semiconducting nanotubes.…”

“…The semiconducting nanotubes are far more reactive than the metallic ones, in agreement with previous works. 10,12 Going from the (10,0) to the (14,0) SWCNT, the addition energy is increased by 17.4 kcal/mol. Such dramatic change was completely unexpected as the reactivity of nanotubes usually decreases upon diameter increase.…”

“…To simulate infinite SWCNTs, we have undertaken periodic boundary calculations for the (5,5), (6,6), (8,8), (12,12), (15,15), (10,0), (14,0), (20,0), and (25,0) SWCNTs. Three unit cells were used to model the metallic tubes and two for the semiconducting ones.…”

“…Cluster model B3LYP based calculations by Galano 10 and by Shukla and Mishra 12 point to the semiconducting nanotubes as the best radical scavengers. For the addition of OCH 3 to nanotubes with diameters as large as 1.1 nm 10 and for the addition of OH to the (10,0) and (5,5) SWNCTs, 12 it was found that reaction energies were significantly more negative ([20 kcal/mol) for the semiconducting nanotubes. However, for the addition of OH and SH radicals to (5,5) and (10,0) SWCNTs, we have reported periodic PBE calculations which indicated that the metallic nanotubes are more reactive.…”