A sensitive colori/fluorimetric nanoprobe for detection of polyphenols using peroxidase-mimic plasma-modified MoO3 nanoparticles.

Herein, MoO3 nanoparticles were synthesized and modified using Argon cold plasma treatment (Ar-MoO3NPs) for the first time. Various characterization studies were performed using various methods, including SEM, XRD, and FTIR techniques. The catalytic activity of MoO3NPs before and after modification was investigated using fluorometric and colorimetric experiments. The results indicated that the enzyme-mimic activity of MoO3NPs increased after plasma-surface modification (1.5 fold). Also, a fluorometric method based on the oxidation of a non-fluorescent terephthalic acid by Ar-MoO3NPs in the presence of H2O2 and the production of a compound with a high emission was designed for polyphenols detection. Quercetin was used as a polyphenol standard for the optimization of the proposed system. Under the optimum conditions, the dynamic ranges of the calibration graphs and the detection limits were calculated for different polyphenols (µmol/L): quercetin (2-232, 12.22), resveratrol (2-270, 61.89), curcumin (39-400, 38.89), gallic acid (2-309, 21.5) and ellagic acid (39-309, 16.25). Also, the precision of the method, which was expressed as RSD%, was in the range of 0.286-1.19%. The proposed system could detect individual polyphenols and total polyphenols in three different fruit extracts (apple, orange, and grapes) with high sensitivity. The obtained total concentrations of polyphenols in real samples were comparable to those calculated by the spectrophotometric method. So, a novel and sensitive optical nanosensor for the detection of polyphenols was reported as an alternative to the routine Folin-Ciocalteu spectrophotometric technique.