Ultra-pH-Sensitive Small Molecule Probe Showing a Ratiometric Fluorescence Color Change

Junjie Cui, Gayoung Kim, Sehoon Kim, Ji Eon Kwon, Soo Young Park

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


We synthesized an amphiphilic small molecule 1 by attaching oligo(ethylene glycol) (OEG) and N,N-diethylamine (DEA) units to a fluorescent dicyanodistyrylbenzene (DCS) core. The molecule is fully soluble in aqueous solution at low pH (pH<4.3) by protonation of the DEA groups; but, above pH 4.3, it self-assembles to form nanoparticles due to increased hydrophobicity upon deprotonation, leading to a ratiometric fluorescence color change from green emission in the monomeric form (λem,max=538 nm) to red emission in the aggregated form (λem,max=646 nm). It should be noted that the ratio of emission intensities at 538 nm and 646 nm (R=I538/I646) changes drastically about 42-fold within a very narrow pH range of 4.3–4.6.

Original languageEnglish
Pages (from-to)393-397
Number of pages5
Issue number6
Publication statusPublished - 2020 Jun 1
Externally publishedYes


  • amphiphiles
  • bioimaging
  • fluorescence switching
  • pH responsiveness
  • self-assembly
  • supramolecular chemistry

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Analytical Chemistry


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