{
  "abstract": "Interactions between water and organic molecules in sub-10 nm clusters surrounded by air play a key role in the chemistry and microphysics of secondary organic aerosol (SOA). However, water-organic interactions in such small clusters are difficult to probe experimentally and remain poorly constrained. Here, we use molecular dynamics simulations to examine morphology, molecular interactions, and water evaporation energetics of nanoclusters formed by nine representative SOA compounds across sizes and water contents. Nanocluster water affinity depends on size and water content, with distinct controlling mechanisms emerging during RH-driven drying. At high and moderate water contents, clusters larger than 4 nm follow a Kelvin baseline based on their bulk-mixture surface tension. In contrast, sub-4 nm organic-shell clusters sometimes retain water much less strongly than expected based on the Kelvin relation as their phase-mixing state changes with cluster size. At low water content, loss of water-network connectivity fragments the water domain into isolated pockets, shifting control of water retention to specific water-organic and water–water interactions, ionic coordination, and steric accessibility, producing species-dependent water affinity that bulk hygroscopicity cannot predict. These results identify where continuum descriptions break down and inform the representation of water in SOA nanoclusters in atmospheric models.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Civil and Environmental Engineering",
    "Princeton University",
    "Department of Geophysical Sciences",
    "University of Chicago",
    "High Meadows Environmental Institute, Princeton Univerisity"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Jiaqi Wen",
      "orcid": "0009-0002-6256-9668"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Xiaohan Li",
      "orcid": "0000-0003-2370-576X"
    },
    {
      "affs": [
        0,
        1,
        4
      ],
      "name": "Ian C. Bourg",
      "orcid": "0000-0002-5265-7229"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/449dpswzmbhwc.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010102/v1",
  "fulltext_url": null,
  "id": "449dpswzmbhwc",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010102/v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1902|Atmospheric chemistry and aerosols"
    ]
  ],
  "openalex": "W7220950530",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010102/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-08",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/449dpswzmbhwc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:22Z",
      "native_id": "10.26434/chemrxiv.15010102",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010102/v1"
    }
  ],
  "subjects": [
    {
      "field": "earth",
      "origin": "openalex:1902|Atmospheric chemistry and aerosols",
      "subfield": "atmospheric"
    }
  ],
  "title": "From Bulk Hygroscopicity to Nanoscale Water Activity: Breakdown of Continuum Theories in Sub-4 nm Secondary Organic Aerosols",
  "title_text": "From Bulk Hygroscopicity to Nanoscale Water Activity: Breakdown of Continuum Theories in Sub-4 nm Secondary Organic Aerosols",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:22Z",
  "url": "https://research.draconitic.com/paper/449dpswzmbhwc",
  "venue": "ChemRxiv",
  "versions": []
}