Leonid Rubinovich
Ben-Gurion University of the Negev, Israel
Title: The unique chemical-equilibrium in nano-systems: Confinement & quasi-confinement effects
Biography
Biography: Leonid Rubinovich
Abstract
Chemical-equilibrium involving a small number of molecules inside a confined nanospace can exhibit considerable deviations from the macroscopic thermodynamic limit due to reduced mixing entropy, as was predicted in several of our works using statistical-mechanics canonical partition-functions and the lattice-gas [1-3] as well as non-lattice [4] models. In particular, for exergonic addition and dimerization a considerable shift of the bimolecular reaction extent towards product formation is expected. This “nanoconfinement entropic effect on chemical-equilibrium” (NCECE) was verified by revised analysis [5] of reported measurements of DNA hybridization inside confined nano-fabricated chambers. More recently, we predicted enhancement of Ir dimerization inside Pd-Ir nanoparticles that can affect their catalytic properties [4].
Using the grand-canonical ensemble, the modeling has been recently extended to the more common “quasi-confined nanosystems” exchanging molecules with a macroscopic environment. As exemplified by dimerization of alkali metal vapors trapped inside pores by potential wells, the following conditions facilitate product-stabilizing NCECE effects under quasi-confinement (QNCECE): (i) limited nanospace capacity; (ii) significant host-guest interactions (deep potential wells); (iii) high-coverage of the nanospace (e.g., due to high external pressure or to low temperatures). In the case of low-coverage product destabilization is predicted because of monomer deficiency effects (opposite to the QNCECE).
The unique chemical-equilibria under confinement and quasi-confinement are anticipated for a wide range of nanospaces (nanopores, zeolites, nanotubes, fullerenes, micelles), and thus can have implications for the growing nanotechnological utilization of chemical syntheses conducted within nanoreactors