does gas sensing depend on nano particle size? why an how? nano-poly-crystalline material also useful or has influence on gas sensing?
There are a lot of interesting works about gas sensing applications of zinc oxide quantum dots, nanorods and nanowires. It has been explained why ZnO nanostructures are efficient system for gas sensing (it is due to variations of some electrical properties of ZnO because of the adsorption of molecules on its surfaces).
It could be useful for you to read a paper by Li Li, Heqing Yang et al. 2010, DOI 10.1007/s00339-009-5457-y.
It has been reported about how the size of the nanoparticles/nanostructure influences the sensing properties of these devices. I suggest to you to read Wang, J.X. et al. 2006, doi:10.1088/0957-4484/17/19/037; Huang, J. et al. 2009 doi:10.3390/s91209903.
Nanoparticle size, morphology and crystalinity DO have an effect on gas sensing properties. Gas/nanoparticle interaction occurs on the surface of the particles, so if you have more surface area that is accesible to the gas, your material will be better for gas sensing, in principle (smaller particles have more surface). Crystallinity also plays a roll since, in general, gas molecules interacts with specific groups on your particle, so its better that most of these groups are on the surface.
Metal oxide gas sensors are predominant solid-state gas detecting devices for
domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties.
Dear Umesh both particle/grain size and crystallinity do affect the sensing properties.....You are requested to go through the following articles which will answer your queries....
Dear Umesh,
According to VRH mechanism/FTS mechanism which are more recently explain the conductivity mechanism describe that the disordered materials like conducting polymers or polymer nano-composites shows variation in conductivity when polar substance expose on the polymer nano-composite films.
(i) Normally coulombic interaction interlocked the charge carriers during the polymerization of polymer nano-composites due to solvents/oxidizing reagents and gaseous molecules decrease the field dependent effect and hence increases the conductivity.
(ii) The so formed nano-composites change the morphology of the substance and decreasing the hopping length and increasing the charge mobility.
Best of Luck.
Dear Umesh,
"increased crystallinity" in nano-poly-crystalline metal oxide increases (through increased mobility of) carriers conductivity. Thus conductivity is more (clearly) sensitive to influences on external (to backbone crystals) scattering surface ("conductivity error") factors, such as nanogas size precipitations and their morphology e.g. resulting in better gas sensing etc.
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