6533b856fe1ef96bd12b1c86

RESEARCH PRODUCT

Acid–Base Properties and Surface Charge Distribution of the Water-Soluble Au102(pMBA)44 Nanocluster

Jaakko KoivistoTanja LahtinenHannu HäkkinenGerrit GroenhofSerena DonniniXi ChenMika Pettersson

subject

Base (chemistry)acid–base propertiesInorganic chemistryProtonation02 engineering and technology010402 general chemistry01 natural sciencescharge distributionMolecular dynamicsDeprotonationCluster (physics)Surface chargePhysical and Theoretical Chemistryta116chemistry.chemical_classificationChemistryCharge density021001 nanoscience & nanotechnology0104 chemical sciencesSurfaces Coatings and FilmsElectronic Optical and Magnetic MaterialsGeneral EnergyPhysical chemistryTitration0210 nano-technologygold nanoclusters

description

The pKa of the p-mercaptobenzoic acid (pMBA) ligands in the Au102(pMBA)44 nanocluster was measured by using acid–base and IR titration. The observed macroscopic pKa = 6.18 ± 0.05 is significantly more basic than that of free pMBA (pKa = 4.16), and the protonation behavior is anticooperative according to the Hill coefficient n = 0.64 ± 0.04. The cluster is truly water-soluble when more than 22 and insoluble when fewer than 7 ligands are in the deprotonated state. In order to obtain more insight into the anticooperative character, the cluster was modeled at pH ∼6.2 using constant pH molecular dynamics simulations. The pKa values of the individual pMBAs are in the range of 5.18–7.58, depending on the positions of the ligands, generating a nonuniform charge distribution on the cluster surface. The cluster interactions with inorganic and biological environment depend on the surface charge distribution, stressing the importance of understanding the protonation state of the cluster.

yearjournalcountryeditionlanguage
2016-05-04Journal of Physical Chemistry C
10.1021/acs.jpcc.6b00922https://doi.org/10.1021/acs.jpcc.6b00922