Theoretical Study Of Statistical Physics Properties Of Cation Effects On Carbon-Based Nanomaterials In Solution Via Hydrated Cation-? Interaction

In 1981,Sunner and cooperators found there is a strong interaction between non-polar benzene and K+ in vacuum.This new type non-covalent bond between cations and nonpolar aromatic rings was named as cation-? interaction.However,there is a strong screen effect for the cation-? interaction from water molecules in aqueous solu-tion,making the hydrated cation-? interaction much weaker than cation-? interaction in vacuum,which results in an underestimate for the cation-? interaction for a long time.Since 2008,our research group has conducted in-depth theoretical studies about the internal relation between aromatic rings on graphene and its derivatives,and declared that,though impaired by the aqueous solution,the hydrated cation-? interaction be-tween cations in solution and carbon-based nanomaterials shouldn't be neglected.This paper shows the unexpected properties on the aromatic ring containing carbon-based nanomaterials in salty solution,from the hydrated cation-? interaction,including these following three works:1.Using different kinds of cations,the internal spacing of graphene oxide mem-branes are precisely controlled.Through ab initio computations,it reveals that hydrated cation is more easily adsorbed where the aromatic rings and oxide groups coexist.The adsorption makes the hydrated cation become a pier between the GOMs.The radiuses of hydrated cations are different,suggesting that cations could be used to produce a wider range of interlayer spacings.Among the hydrated cations,the hydrated K+ has the smallest radius,which results in the narrowest interlayer spacing of the cation con-trolled GOMs.The K+ controlled GOMs can efficiently and selectively exclude the other cations,including the other K+ in solution.Further studies reveal the cationic control of interlayer spacing method can also be applied on graphene membranes.This work gives a new way on ion sieving and water desalting of graphene like membranes.2.Through MD simulations added with hydrated cation-? interaction correction,it reveals that,the ions would adsorb on the graphene surface and crystallize with more Na+ than Cl,even in the dilute NaCl solution.Furtuer studies based on ab initio compu-tation provide several stable crystal structures of Na-Cl cluster with graphene,including two-dimensional unconventional stoichiometries structures as Na2Cl and Na3Cl.Orbit analysis and Mulliken charge distribution reveals the in-depth mechanism that how these abnormal crystal structure can stably exist on graphene or between the graphene membranes.The cooperator confirmed the existence of these two-dimensional uncon-ventional stoichiometries structures,with XRD,EDS and EELS experiments.Na2Cl and Na3Cl,containing different electronic structure with standard NaCl,may have brand new characteristic in electronic,magnetic and optics.3.The coffee ring effect is a physical phenomenon that,with the evaporating,the precipitation of suspensions would form a ring.The Coffee effect has disadvantages in spray coating and printing,which influences the scientific researches and industry pro-ductions.Cooperators found that,adding slight salts(e.g.NaCl,KCl)in the suspension drop on the graphene,the coffee ring effect would be effectively suppressed.Based on the MD simulation added with the hydrated cation-? interaction correction,I found the suspensions deposit more homogeneous,and without "coffee ring" pattern in the mixture drop during the evaporation.Further studies show the cations can induce the suspensions in the solution reaching the bottom of the drop,and adsorbed on the surface with aromatic rings.This prevents the transport of suspensions from the drop center to the edge,which suppresses the appearance of coffee ring.