Fe7S8 nanosheets- catalyzed colorimetric and fluorescence dual ratio sensing for high selectivity detection of ascorbic acid

By using Fe 7 S 8 nanosheets (NSs) as catalyst, O -phenylenediamine (OPD) as chromogenic substrate, H 2 O 2 as oxidant, and ascorbic acid (AA) as regulator, a dual ratio colorimetric and fluorescence sensing system for determining AA was constructed. The inherent peroxidase like activity of Fe 7 S 8 NSs enables it to catalyze the oxidation of OPD in the existence of H 2 O 2 , resulting in the formation of yellow-colored 2, 3-diaminophenazine (DAP) with a characteristic absorption peak at 450 nm and a fluorescence emission peak at 560 nm. However, the presence of AA could suppress the oxidation of OPD and induce the generation of quinoxaline derivative (QXD) 3-(dihydroxyethyl) furo [3,4-b] quinoxaline-1-one with absorption and fluorescence emission peaks located at 345 and 435 nm, respectively. Thus, employing the absorption of QXD at 345 nm and emission at 435 nm as the reporting signals, and the absorption of DAP at 450 nm and emission at 560 nm as the reference signals, a ratio colorimetric ( A 345 / A 450 ) and ratio fluorescence ( F 435 / F 560 ) dual signal detection method for AA was developed. Under the optimized conditions, the value of A 345 / A 450 was found to be linear with AA concentration in the ranges of 1.0–40 μM and 40–100 μM, and the value of F 435 / F 560 was strongly correlated with AA concentration in the ranges of 1.0–30 μM and 30–100 μM. When applied for the assay of AA in human serum samples, an acceptable recovery ranging from 93.1 to 106.6 % was obtained, confirming the potential of the sensing system in practical applications.