Graphene quantum dots as sensor for phenols in olive oil

• A fluorescence based methodology for total phenol determination is proposed.
• The influence of parameters such as pH, type of solvent and nanoparticles concentration is crucial in the sensing mechanism.
• The developed GQDs sensor is rapid, sensitive and highly reproducible.
• Real samples of olive oil were employed in order to testify the viability of the phenol sensor.

A new method for the determination of the phenol fraction of olive oil is reported. An optical nanosensor based on graphene quantum dots, obtained by pyrolysis of citric acid, was specifically developed for this purpose. The ensuing fluorescence sensing method, which is simple, and highly sensitive and reproducible, was used here to determine gallic acid and oleuropein as model analytes commonly found in olive oils, as well as the phenolic concentration of olive oil real samples. The detection limits were lower than 0.12 mg L−1 and the precision, expressed as relative standard deviation, lower than 1.7%.