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PreprintCC BYChemRxiv

Surface charge mosaic of a water-soluble Au25(p-MBA)18 nanocluster induced by environment’s pH

  • Miia M. Moilanen1,2
  • Noora Aho3,4,5,6
  • María Francisca Matus7,2
  • Emmi Pohjolainen7,2
  • Hannu Häkkinen1,2,7
  • Hannu Hakkinen
7 affiliations
  1. 1Department of Chemistry, Nanoscience Center
  2. 2University of Jyväskylä
  3. 3Computational Physics Laboratory
  4. 4Tampere University
  5. 5Theoretical Physics and Center for Biophysics
  6. 6Saarland University
  7. 7Nanoscience Center
Open at sourceDOICite

Abstract

Water-soluble monolayer-protected gold nanoclusters (AuNCs) are widely regarded as promising nanomaterials for biological and biomedical applications, yet the impact of environment’s pH on their surface charge distribution is poorly understood, hampering efforts to rationally design the cluster size and ligand chemistry for optimizing reactivity and solvation. To investigate the pH-effect, we used constant-pH molecular dynamics simulation method for statistical sampling of ligand charge distributions in a water-soluble gold nanocluster protected by para-mercaptobenzoic acid ligands, Au25(p-MBA)18, in a wide pH range of 1 to 11. The results showed three macroscopic pKa values for the ligand layer: 2.25 ± 0.01, 5.68 ± 0.02, and 6.23 ± 0.04, and indicated anticooperative deprotonation behavior with Hill coefficients ranging from 0.74 to 0.34. The ligand layer pattern and interligand interactions through π–π stacking explained the observed order of the ligand deprotonation. These results uncover ligand-specific deprotonation behavior of Au25(p-MBA)18, enabling precise tuning of its functional performance across diverse applications in biological environment.

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Cite

BibTeXRIS
BibTeX
@misc{moilanen2026surface,
  title = {{Surface charge mosaic of a water-soluble Au25(p-MBA)18 nanocluster induced by environment’s pH}},
  author = {Miia M. Moilanen and Noora Aho and María Francisca Matus and Emmi Pohjolainen and Hannu Häkkinen and Hannu Hakkinen},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15009514/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009514/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Surface charge mosaic of a water-soluble Au25(p-MBA)18 nanocluster induced by environment’s pH
AU  - Miia M. Moilanen
AU  - Noora Aho
AU  - María Francisca Matus
AU  - Emmi Pohjolainen
AU  - Hannu Häkkinen
AU  - Hannu Hakkinen
PY  - 2026
DA  - 2026/09/28
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15009514/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009514/v1
AB  - Water-soluble monolayer-protected gold nanoclusters (AuNCs) are widely regarded as promising nanomaterials for biological and biomedical applications, yet the impact of environment’s pH on their surface charge distribution is poorly understood, hampering efforts to rationally design the cluster size and ligand chemistry for optimizing reactivity and solvation. To investigate the pH-effect, we used constant-pH molecular dynamics simulation method for statistical sampling of ligand charge distributions in a water-soluble gold nanocluster protected by para-mercaptobenzoic acid ligands, Au25(p-MBA)18, in a wide pH range of 1 to 11. The results showed three macroscopic pKa values for the ligand layer: 2.25 ± 0.01, 5.68 ± 0.02, and 6.23 ± 0.04, and indicated anticooperative deprotonation behavior with Hill coefficients ranging from 0.74 to 0.34. The ligand layer pattern and interligand interactions through π–π stacking explained the observed order of the ligand deprotonation. These results uncover ligand-specific deprotonation behavior of Au25(p-MBA)18, enabling precise tuning of its functional performance across diverse applications in biological environment.
ER  -