Synthesis of blue emissive fluorescent nitrogen doped carbon dots from Annona squamosa fruit extract and their diverse applications in the field of catalysis and bio-imaging

Fluorescent nitrogen-doped carbon dots (FNCDs) were prepared from the fruits of Annona squamosa by hydro thermal method, further they were characterized and studied for the reduction of Reactive Red-120 (RR-120) dye and bio-imaging. Functional groups, surface functionalities present in FNCDs and as well as nitrogen doping were studied using FT-IR and XPS techniques. The optical properties of FNCDs were assessed using UV-Visible and PL spectroscopy. The quantum yield of FNCDs was 14.16%. HR-TEM results revealed the spherical nature of FNCDs with 4 +/- 0.25 nm in size and AFM data revealed the height of FNCDs. The amorphous nature of FNCDs was confirmed from the results of XRD, Raman spectra and SAED patterns. TGA data brought out the thermal behavior of FNCDs. These FNCDs were tested for their catalytic role in the reduction of RR-120 dye by NaBH4. Results showed that FNCDs could catalyze the reduction of RR-120 dye within 12 min and the reduction products were analyzed using mass spectral data. The reduction reaction was explained on the basis of the LangmuirHinshelwood mechanism. The possible use of FNCDs as fluorescent probes in cell imaging was also explored by MTT assay.