Thermodynamics of Adsorption on Graphenic Surfaces from Aqueous Solution

• DOI: 10.1021/acs.jctc.8b00830
• Publication Date: 2018-12-28T21:26:10Z
• Authors: E. R. Azhagiya Si...; Yuntao Zhang; Geraldine Magnin; Ingrid Miranda-Ca...; Logan Coates; Ravindra Thakkar; Horacio Poblete; Jeffrey Comer
• Keywords: Alkylbenzenes

Adsorption of organic molecules from aqueous solution to the surface carbon nanotubes or graphene is an important process in many applications these materials. Here we use molecular dynamics simulation, supplemented by analytical chemistry, explore detail adsorption thermodynamics a diverse set aromatic compounds on graphenic materials, elucidating effects solvent, coverage, curvature, defects, and functionalization hydroxy groups. We decompose free energies into entropic enthalpic components find that different classes compounds-such as phenols, benzoates, alkylbenzenes-can easily be distinguished relative contributions entropy enthalpy their energies. Overall, dominates for more hydrophobic compounds, while plays greatest role hydrophilic compounds. Experiments independent simulations using two force field frameworks (CHARMM Amber) support robustness conclusions. determine concave curvature generally associated with greater affinity, favorable enthalpy, contact area, convex reduces both area. Defects surfaces can create resulting localized binding sites. As becomes covered solutes, affinity adsorbing additional solute increases until complete monolayer formed, driven partially canceled less entropy. Similarly, hydroxylation leads preferential solutes remaining regions bare graphene, entropy, but compensated increase interactions.