Microwave-assisted green synthesis of multi-functional carbon quantum dots as efficient fluorescence sensor for ultra-trace level monitoring of ammonia in environmental water

This study reports a facile green preparation of self-assembled multi-functional carbon quantum dots (CQDs) via direct pyrolysis technique coupled with microwave-assisted synthesis using Ziziphus Mauritiana stone biomass (as a bio-resource precursor). The synthesized multi-functional CQDs was characterized using FT-IR, XRD, XPS, TEM, and fluorescence spectroscopy techniques. The results exhibit that the prepared CQDs are spherical-shaped with an average diameter of 2-4 nm and showed bright bluish-green emissions property with stable dispersion and high photostability in the aqueous medium. Furthermore, the emission properties of CQDs were examined by quenched with ammonia (NH3) and other molecules in aqueous media. Results indicated that the developed CQDs showed effective fluorescent for the selective and sensitive detection (sensor) of NH3 with a detection limit of 10 nM. Thus, the presented procedure is a simple, low-cost, efficient, chemical-free synthesis of CQDs and can be applied as selective and sensitive (sensor) monitoring of NH3 concentration in aquatic environmental samples.