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 ID/IG 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.
Highlights
Carbon-based nanomaterials such as carbon nanotubes,[1] graphene oxide,[2] fullerenes,[3] and carbon nanodots[4,5] have been playing vital roles in science and technology in the past two decades
The graphical representation of the hydrothermal synthesis of nitrogen-functionalized carbon nanodots (NFCNDs) is given in Scheme 1
The two main characteristic peaks appeared for NFCNDs at 271 nm and 304 nm, which correspond to the pi–pi* transition for the sp[2] carbon (C]C bonds) and n-pi* transitions of the carbonyl and amine functionalization on the NFCNDs surface, respectively.[42]
Summary
Carbon-based nanomaterials such as carbon nanotubes,[1] graphene oxide,[2] fullerenes,[3] and carbon nanodots[4,5] have been playing vital roles in science and technology in the past two decades. CNDs are quite divergent from other carbon-based nanomaterials due to their exclusive outstanding properties, such as high water dispersibility, strong chemical inertness, uorescence, excellent photostability, less toxic nature, excellent bio-compatibility, environmental. CNDs have been synthesized by various top-down methods, including laser ablation, ultrasonic treatment, arc-discharge, and electrochemical and chemical oxidation, and bottom-up methods such as hydrothermal carbonization, microwave irradiation, pyrolysis, and plasma treatment.[17] Among these synthesis methods, arc discharge and laser ablation processes need highly expensive instruments, whereas electrochemical oxidation and chemical oxidation need strong acids. The hydrothermal method is simplistic, quick, and economical, has a simple experimental setup, is and eco-friendly when compared to other synthesis methods. Using inexpensive and eco-friendly biomass sources such as Phyllanthus emblica, prickly pear cactus, rice bran, Coccinia indica, and sweet potatoes as carbon
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