Natural luminescent carbon nanoparticles extracted from coconut water

Abstract

The synthesis methods of carbon nanoparticles (CNPs) are of utmost importance to the commercialization of CNPs as they need to have an efficient cost-to-gain. In this paper, we report on a facile method for extracting CNPs out of a renewable and green source of coconut water without the need for any time or energy consuming synthesis procedure. Namely, the CNPs were essentially extracted by filtration of coconut water using a dialysis bag to remove long-chain carbohydrates and bulk contaminants. The obtained CNPs were characterized using several techniques including high-resolution transmission electron microscope (HRTEM), photoluminescence (PL) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), zeta potential analyzer, time-resolved photoluminescence lifetime measurement, and X-ray diffraction (XRD). It was found that the obtained CNPs have an average lateral size of 4.5 nm and interestingly, show UV and blue light emissions when excited optically by deep UV light. The latter indicates the potential application of these CNPs in optoelectronics. XPS data shows a C/O ratio of 65%/28% which is an expected result for the surface bonds of a CNPs and is in agreement with the FTIR data which demonstrates a dominance of carbon and oxygen-based function groups. The CNPs also demonstrate a long fluorescence lifetime of 5.3 ns which is relatively longer than that in literature.