Dear colleagues
Sweet greetings
In pH sensor application, the sensing characteristics depend basically on the surface site density (NS), I want to know what are these sites represent? Are they the number of particles or atoms available on the surface which allowed ion-exchange with the proton? Or may be they are the positions on the surface (on the particle itself) that expose to the electrolyte, which means that one particle could have more than one site, as shown in the attached schematic? For the latter, is the surface site density has a relation with the orientation?
Thank you
Fayroz
Dear Fayroz,
Ns is the numerical density of sites [m-2] available for proton exchange, hence a particle can have multiple sites.
I suggest you to read this publication:
https://research.utwente.nl/en/publications/a-general-model-to-describe-the-electrostatic-potential-at-electr
It is a rather complex paper but really exhaustive in the description of the "site-binding model" (introduced by Yates in 1973):
http://pubs.rsc.org/en/Content/ArticleLanding/1974/F1/f19747001807#!divAbstract
Furthermore, we recently developed a slightly simplified electrostatic model for pH sensing in Electrolyte-Gated Organic Field-Effect Transistors that may be suitable for your specific problem:
http://pubs.acs.org/doi/abs/10.1021/acsami.6b06952?src=recsys
I hope this answer was helpful, let me know if you solve your problem.
Sincerely,
Michele
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