Viscosity to entropy density ratio ($\eta$/s) in nanoliquid

MM Islam and A De and D Pandit and B Dey and N Sakib and S Bhattacharya, PHYSICS AND CHEMISTRY OF LIQUIDS, 60, 667-681 (2022).

DOI: 10.1080/00319104.2022.2031195

We present the coefficient of viscosity (eta), entropy (S) and viscosity to entropy density (s) ratio (eta/s) for aqueous silver nanoparticle (AgNP) solution at temperatures T = 273-300 K performing experiments and examining the same with discrete dipole approximation (DDA) simulation. The experimental UV-Visible dipole extinction spectra of the nanoliquid, matched with simulations, explore cluster morphologies. The latter is used for the calculation of eta (cluster volume fraction similar to 4-10%; NP, cluster radii 8-15 nm and 35-55 nm, respectively). In addition, dimer (AgNP-AgNP) formation free energy and S are explored at those T's. We determine eta/s ratio exploiting nanoparticle behaviour. The value of eta/s is found lower than that of water and similar to strongly correlated liquid He-4, owing to higher S for NP agglomeration. Our results of eta, S and eta/s are also corroborated from hard sphere model calculation. This, to the best of our knowledge, is the first attempt to determine eta/s in NP.

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