Sulfur doped fluorescent carbon dots as nanosensors for rapid and sensitive monitoring of calcium in hard water

Alexandre Loukanov, Polina Mladenova, Hibiki Udono, Z. Miskolczy, Anatoly Angelov, L. Biczók, Seiichiro Nakabayashi

Research output: Contribution to journalArticle

4 Citations (Scopus)


Herein, we have developed carbon nanodots (C-dots) doped with sulfur as fluorescent nanosensor for rapid and sensitive determination of dissolved calcium ion concentrations and water hardness in natural aqueous media. The nanoparticles were synthesized via green microwave assisted pyrolysis of citric acid and cysteamine mixture. They exhibited highly intensive blue fluorescence under irradiation with UV light (365 nm excitation) with high quantum yield (~ 49 %). The specific sensor selectivity to dissolved Ca2+ arose from the variety of organic functional groups on the nanoparticle surface and the presence of sulfur. The detection process was based on quenching of C-dots photoluminescence and linear relationship between concentration of Ca2+ ions and fluorescence intensity. On the other hand, the fluorescence of the amino-passivated C-dots without sulfur was sensitive to the total amount of bicarbonate in the solution. In addition, the presence of polar organic groups at the surface facilitated the good dispersibility of C-dots in natural aqueous media, particularly in groundwater with diversity of ionic strength and salts. The nanoparticles could be regenerated and multiply re-used by rinsing with hydrochloric acid solution and purification with desalting column. Furthermore, the quantity of calcium ions in mineral water determined by C-dots agreed well with the Ca2+ content of the sample, suggesting the potential application of the developed carbon nanodots.

Original languageEnglish
Pages (from-to)473-479
Number of pages7
JournalJournal of Chemical Technology and Metallurgy
Issue number3
Publication statusPublished - Jan 1 2018



  • Calcium detection
  • Carbon nanodots
  • Water hardness monitoring

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

Cite this