Green Synthesis of Fluorescent Carbon Dots through Solvothermal Treatment of Buchnania lanzan Leaf Extract

Abstract

In the present work, we synthesized fluorescent carbon dots (CDs) through solvothermal treatment of Buchnania lanzan leaf extract at 160 °C for 4 h in an oven. Here, Buchnania lanzan leaves served as a renewable source of carbon. The obtained blackish brown CD solution was centrifuged, and the supernatant was filtered through a syringe filter (0.22 µm). Further, the CD solution was dried in a vacuum oven to obtain a powder. The synthesized CDs were characterized by different techniques including UV–visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared (FTIR), zeta potential and X-ray diffraction (XRD). The as-prepared CD solution was found to be brownish colored in daylight while exhibiting green fluorescence under UV light. The UV–visible absorption spectrum displayed characteristic shoulder peaks of CDs at 257 nm and at 356 nm. In the fluorescence spectra, excitation-dependent emission behavior of the CDs was seen, which is one of the distinct characteristics of CDs. The negative zeta potential and characteristic peaks in FTIR suggested the presence of carbonyl, amine and hydroxyl functional groups on the CD surface. The XRD spectrum exhibited a broad peak at 2θ=19°, suggesting the amorphous nature of the CDs, similar to what has been reported in earlier works. As we synthesized surface-functionalized fluorescent carbon dots from a renewable and abundant precursor, this method can be highly useful in the large-scale synthesis of carbon dots with reduced costs and will find potential applications in the fields of drug delivery, bioimaging, etc.