Carbon-based nanomaterials, particularly carbon dots (C-dots) have attracted the researchers interest due their excellent luminescence, photostability and biocompatibility, encouraging their use in several areas such as biomedicine, (bio)sensors, photocatalysis and optoelectronics.

C-dots could be prepared by a variety of methods (top-down and bottom-up approaches), using a great diversity of carbon sources. Bottom-up processes based on the use of waste materials for producing C-dots are particularly attractive since an effective reduction of environmental impacts of those wastes may be foreseen, while high-valued nanomaterials can be simultaneously obtained.

Coffee is one of the most consumed brews all over the world, generating large amounts of coffee waste, a source of a serious environmental problem due to the high content of organic matter such as caffeine, phenols, tannins, and sugars.

Herein, we explore the valorization of coffee grounds generated from automatic and vending machines for production of C-dots through a one-pot monomode microwave-assisted method.

Structural and photophysical characterization of the as-synthesized nanomaterials have been carried out, and their potential applications as sensing materials for pollutants and explosives (e.g. nitroanilines and nitroaromatics) were evaluated by fluorescence and absorption techniques.