Facile synthesis and characterisation of green luminescent carbon nanodots prepared from tender coconut water using the acid‐assisted ultrasonic route

Abstract

In the present investigation, the authors have adopted a simple and economical method for the synthesis of bright green photoluminescent carbon nanodots (CNDs) from tender coconut water via acid-assisted ultrasonic route. Tender coconut water is used as a less expensive and eco-friendly carbon precursor to produce well-dispersed CNDs possessing a hybrid structural behaviour of both nanocrystalline and amorphous carbon phases. The monodispersed CNDs with spherical morphology and particle size (4 ± 1 nm) were confirmed with the aid of high-resolution transmission electron microscopy. The functional groups attached to CNDs are held responsible for the fluorescence nature and mono-dispersion that were assessed using Fourier transform infrared spectroscopy. The green fluorescence nature of CNDs was evaluated at a maximum emission at 510 nm with an excitation wavelength of 450 nm, using ultraviolet–visible absorption spectrum and photoluminescence spectra. The CNDs with a carbon core and chemical groups over their surface exhibited a fluorescence quantum yield of 60.18%. The stability, low-cost precursor, rapid reaction and uniform dispersion without chemical functionalisation makes these CNDs synthesised from tender coconut water more advantageous than other sources. This research mainly emphasis on synthesis and characterisation of CNDs with a detailed mechanism for CND formation.