{
  "abstract": "Carbon dots (CDs) prepared from o -phenylenediamine (oPD) have attracted significant research interest, because they can exhibit blue, green, or red fluorescence depending on synthetic conditions and dopants. The red- and NIR-emitting oPD-based CDs are of particular interest because of their potential for bioimaging and biomedical applications. Efforts to understand the relationship between their structure and optical properties have led to the proposal of various hypotheses of the red luminescence, which are however difficult to support due to limited knowledge of their precise structural arrangement. Although in some oPD-based CDs, a molecular fluorophore 5,14-dihydroquinoxalino[2,3- b ]phenazine (DHQP) has been identified as a source contributing to the red emission of CDs, the complex synthesis-dependent photophysical properties of oPD-based systems seemingly pointed to more complicated mechanisms. However, here we show that the complex behavior of oPD-based CDs can be in fact almost universally explained solely by the formation of DHQP. Based on the comprehensive data analysis of more than 80 oPD-based red-emissive systems in works published during the past 10 years and a systematic investigation of DHQP emission under various conditions, we demonstrate that the optical properties of more than 95% of such systems can be rationalized by the presence of different protonation forms of DHQP and their solvatochromic behavior.",
  "abstract_shown": true,
  "affiliations": [
    "Faculty of Natural Sciences, Matej Bel University, Tajovského 40, Banská Bystrica, Slovakia, SK-974 01",
    "Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, Bratislava, Slovakia, SK-842 15",
    "Czech Advanced Technology and Research Institute (CATRIN), Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, Olomouc, Czech Republic, 779 00"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Jela Nociarova",
      "orcid": "0000-0002-5773-5249"
    },
    {
      "affs": [
        1
      ],
      "name": "Martin Ošťadnický"
    },
    {
      "affs": [
        0
      ],
      "name": "Alena Panáčková"
    },
    {
      "affs": [
        0
      ],
      "name": "Šimon Budzák",
      "orcid": "0000-0003-4811-8342"
    },
    {
      "affs": [
        0,
        2
      ],
      "name": "Miroslav Medveď",
      "orcid": "0000-0001-8599-1031"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/0bbp4v539kxcf.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15008236/v1",
  "fulltext_url": null,
  "id": "0bbp4v539kxcf",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008236/v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2505|Carbon and Quantum Dots Applications"
    ]
  ],
  "openalex": "W7207753798",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15008236/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-03",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/0bbp4v539kxcf.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:17Z",
      "native_id": "10.26434/chemrxiv.15008236",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008236/v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:2505|Carbon and Quantum Dots Applications",
      "subfield": "materials-polymers"
    }
  ],
  "title": "The origin of red luminescence in o-phenylenediamine-based carbon dots",
  "title_text": "The origin of red luminescence in o-phenylenediamine-based carbon dots",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:17Z",
  "url": "https://research.draconitic.com/paper/0bbp4v539kxcf",
  "venue": "ChemRxiv",
  "versions": []
}