Binding of carboxylates to gold nanoparticles: A theoretical study of the adsorption of formate on Au20

Using density functional theory, Au20–formate complexes are investigated as a model of carboxylate–gold nanoparticle binding. Formate preferentially interacts with low-coordinated apex gold atoms. In the gas phase, only two anions bind to the Au20 core; incremental binding energies decrease sharply as the number of complexed carboxylates increases. As additional carboxylates bind, electron density builds up on uncomplexed apex atoms. In implicit water solvent, the incremental binding energies for the first four carboxylates are essentially constant (68–77 kJ/mol at the BP86/TZP level of theory); the fifth and sixth carboxylates are non-bonding.