One-pot hydrothermal green synthetic approach of fluorescent carbon dots as optical probes for 2-nitrophenol

Abstract

The pursuit of a cost-effective and green synthetic approach to chemical sensors and their application in the sensing of toxic and harmful  substances is a never-ending exercise for scientists and researchers. Preparation of fluorescent carbon dots (C-dots) from biomass using  water as a solvent and a hydrothermal autoclave to provide the required synthesis temperature offers a cheap and environmentally  friendly synthetic approach. Herein, we report a faster, less costly and ecofriendly hydrothermal synthetic approach of carbon dots from  Citrullus vulgaris peels as a precursor. The as-prepared carbon dots exhibited hydroxyl, carbonyl and amide functional groups on the  surface and an amorphous structure with a particle size distribution of 1.7–3.0 nm. Moreover, the carbon dots displayed intense blue  emission fluorescence at 470 nm after excitation at 400 nm. The as-prepared carbon dots demonstrated effective application without  further modification towards the selective and sensitive optical recognition of 2-nitrophenol used in the manufacture of explosives. A  limit of detection of 2.28×10−7 M was achieved, and no fluorescence quenching was observed in the presence of other nitroaromatic and  benzene derivatives indicating excellent selectivity towards 2-nitrophenol. Finally, further studies are required to investigate the potential for the as-prepared carbon dots to monitor nitroaromatic pollutants in real environmental systems.

Significance:

• Terrorism is an ever- increasing problem, and law enforcement agencies are continuously searching for and detecting explosives hidden in travel luggage,  mail packages, vehicles and aircrafts using sophisticated equipment which are not available in developing countries such as Botswana.

•  This work unveils a facile and environmentally friendly approach towards the detection of 2-nitrophenol used in the manufacture of  explosives by employing highly luminescent C-dots obtained from locally available agricultural waste.

• The utilisation of agricultural  waste can help advance a sustainable waste management programme and promote a circular economy