Sensitive detection of picric acid based on creatinine-capped solid film assembled by nitrogen-doped graphene quantum dots and chitosan

Picric acid (PA) was sensitively detected via changed fluorescence of nitrogen-doped graphene quantum dots (N-GQDs) solid film in this paper. The mixture of N-GQDs and chitosan was firstly deposited on the silica slides to form N-GQDs solid film. Then creatinine was capped outside the solid film to enhance the selectivity to PA according to Jaffé reaction. The prepared solid film can provide strong fluorescence signal due to the strong blue emission of N-GQDs. PA can quench the fluorescence signal of creatinine/N-GQDs-chitosan solid film greatly due to the electron transfer among PA, creatinine and N-GQDs. Under the optimal condition, the fluorescence intensity of solid film was related linearly to the concentration of PA in the range of 2.0-200.0 ng/mL with a detection limit of 1.24 ng/mL. The selectivity of fluorescence quenching of the fluorescent solid film for PA was enhanced. Moreover, the potential application of the proposed methodology for the sensing of PA in water was demonstrated with a satisfactory result. The fluorescence intensity of film sensor was investigated and showed high stability in four weeks. To the best of our knowledge, it was the first report of PA detection by using the quenched fluorescence of N-GQDs solid film.