Influence of precursor chemistry in the property of carbon nanodots and its application for the degradation of methyl orange

Abstract

Carbon nanodots (CNDs) are interesting materials from renewable sources that exhibit unique fluorescence property. This study reports that sulfated carrageenan (ᴋ-, ɩ-, λ-) as carbon precursors for CNDs impart unique properties not observed in a non-sulfated source. Hydrothermal process afforded CNDs having quasi-spherical shapes (TEM), nano sizes (TEM: 3.8 nm; DLS 1.0–2.3 nm), luminous green property under UV light, and presence of sulfur in CNDs (EDS, FTIR). The CNDs were embedded in a carrageenan film matrix to prevent its aggregation and to improve its stability affording brown-colored free-standing films that have better stability (zeta potential) compared to bare CNDs in solution. The CNDs from carrageenan exhibited unique acidic property in water, which is not observed in CNDs from galactose indicating that the sulfate-laden carrageenan precursor imparts unique property to the CNDs. Degradation activity on methyl orange (MO) dye was only observed for CNDs derived from carrageenan and not from galactose confirming the critical role of precursor chemistry in imparting unique acidic properties to the resulting CNDs. The study demonstrated the difference in the carrageenan-based CNDs compared to those prepared from simple sugar and showed its application for the degradation of dyes without the need for direct exposure to sunlight.