Cyan color-emitting nitrogen-functionalized carbon nanodots (NFCNDs) from Indigofera tinctoria and their catalytic reduction of organic dyes and fluorescent ink applications

Abstract

The present study reports the synthesis of nitrogen-functionalized carbon nanodots (NFCNDs) by a low-cost hydrothermal method using the leaf extract of Indigofera tinctoria as a novel carbon precursor. The synthesized NFCNDs were characterized by diverse spectroscopic techniques. The optical properties of N-CNDs were analyzed by UV-visible and fluorescence spectroscopic studies. The quantum yield (QY) for the prepared NFCNDs was found to be 12.6%. The surface morphology, functional groups, and crystallinity of NFCNDs were evaluated by HR-TEM, FT-IR, XRD and Raman spectroscopic methods, respectively. The Raman results revealed the moderate graphite structure of NFCNDs, and the calculated I_D/I_G value was 0.49. The spherical appearance of the synthesized NFCNDs was confirmed by HR-TEM, and the calculated size of the NFCNDs was 4 nm. The XRD and SAED pattern results gives an evidence for the amorphous nature of the prepared NFCNDs. The thermal stability of NFCNDs was studied by TGA analysis. The resulting NFCNDs acted as a green nanocatalyst and thus efficiently improved the reducing capability of sodium borohydride (NaBH₄) in the catalytic reduction of methylene blue (MB) and methyl orange (MO) dyes. Furthermore, the bright cyan emission characteristics of synthesized NFCNDs were utilized as a labeling agent in anti-counterfeiting applications.