Microwave assisted green synthesis of carbon dots from sweet flag (Acorus calamus) for fluorescent sensing of 4-nitrophenol

In this piece of work, a simple and cost-effective fluorescence sensor for the detection of 4-nitrophenol (4-NP) was developed from natural resource, sweet flag (Acorus calamus) through greener route by the use of microwave energy. 4-NP is identified as a potential water pollutant by EPA which can exert several hazardous effect in humans and other aquatic organisms and hence lower level detection of 4-NP is highly demanding. The as obtained carbon dots with excitation dependent fluorescence behaviour, designated as SFCDs, produced a noticeable quenching in fluorescence on interacting with 4-NP. Therefore, a simple and time-saving fluorescence sensing for the detection of 4-NP was developed. The observed turn-off in fluorescence of SFCDs with 4-NP was investigated through different experiments and finally accredited to a combination of both static quenching and inner filter effect (IFE). The proposed probe selectively detect the 4-NP with LOD of 0.207 µM and linear range of 0-14.28 µM, the detection limit was found to be lower than allowed concentration of this pollutant in drinking water. Furthermore, the same method has been practically applied for detecting 4-NP in natural water resources with good level of recovery percentages. As a whole, the developed method gives value addition to the sweet flag for the first time by its direct materialization through a completely greener route without using any hazardous chemicals. The good level of precision and accuracy with detection limits in micromolar range are promising to use the system as a fluoroprobe for detecting 4-NP, a primary pollutant found in natural water resources.