Table 2.

Representative examples of recent developed fluorescence assays for the determination of antioxidants in food samples.

Strategy	Nanomaterial	Antioxidants	LOD	Linear Range	Food Matrix	Advantages/Disadvantages	Ref.
CdTe QDs fluorescence quenching inhibition	CdTe sodium periodate	Catechin, quercetin, rutin, chlorogenic acid, gallic acid, caffeic acid	0.63 nM	0–4.24 µM	Tea, lemon balm, peppermint, lime, chamomile, and coffee infusions	More sensitive, selective/Failure to report stability, reproducibility, incubation time	[67]
Polyaniline quenched CdTe QDs fluorescence	CdTe QDs	Glutathione, ascorbic acid	50, 100 nM	2–40 µM	Not reported	Simple, sensitive, label-free, stable, selective/Failure to report reproducibility, incubation time, food matrix	[68]
Glutathione-capped CdTe quantum dots	CdTe QDs	Glutathione	0.00005 mM	0.0001–0.005 mM	Juice beverages	Very low consumption of reagents, reproducible/Failure to report incubation time, stability	[69]
Fluorescence quenching of the QDs	CdSe/ZnS QDs and graphene	tert-butylhydroxy-anisole, tert-butylhydroxy-toluene, tert-butylhydroquinone, Propyl gallate, sesamol, ferulic acid, daidzein, carnosol	0.7 µM	2–27 µM	Not reported	High sensitivity, accuracy, rapid detection/Failure to report stability, reproducibility, incubation time	[70]
Graphene QDs quenching on paper	Graphene QDs	Morin, myricetin, quercetin, kaempherol	6.67 × 10−5 M (UV), 2.35 × 10−5 M (UV LED)	1.66 × 10−5 to 1.33 × 10−4 M (UV), 1.66 × 10−5 to 2.50 × 10−4 M (UV LED)	Wine samples	Simple, inexpensive, rapid sensing systems, sensitive, reproducible, stable/Failure to report incubation time	[71]
Reduction of Cu2+ to Cu+	Graphene QDs	Ascorbic acid	0.094 µM	0.3–10 µM	Not reported	Rapid, sensitive, low-cost, simple, highly efficient, selective, stable/Failure to report reproducibility, short incubation time (1 min)	[72]
Reaction between (GQDs) and squaric acid (SQA)-iron(III)	Graphene QDs	Ascorbic acid	0.2 µM	1–95 µM	Fruit juices	Simple, sensitive, selective, rapid, label free, versatile, not require high toxic metal (e.g., Cr(VI)) and high-cost enzyme, satble, short incubation time (1 min)/ Failure to report reproducibility	[73]
Benzoquinone in the presence of hydroxyl radicals caused quenching of GQDs)	Graphene QDs	Ascorbic acid	0.32 µM	1.11–300 µM	Human serum	Simple, low cost, higher sensitivity, selectivity, rapid, stable/Failure to report incubation time, reproducibility, without evaluation food matrix	[74]
Graphene QDs Hypochlorite hybrid system	Graphene QDs	Ascorbic acid	1.4 µM	8–60 µM	Commercial drinks (Orange juice, Apple juice, Tea)	High recovery, stability, short incubation time (30 min), robust, sensitive/Failure to report reproducibility	[75]
Quenching graphene QDs by Cr(VI)	Graphene QDs	Ascorbic acid	0.0037 µM	0.05–500 µM	Water samples	Simple, rapid, sensitive, selective, short incubation time (5 min)/Failure to report stability, reproducibility	[76]
Glutathione binding Hg2+	Graphitic carbon nitride quantum dots (g-CN QD)	Glutathione	37 nM	0.16–16 µM	Not reported	High selectivity, sensitivity, cost-effectivity, rapidity, stable, short incubation time (5 min)/Failure to report reproducibility, not evaluation in food matrix	[77]
Aluminium(III)-quercetin complex	Not reported	Quercetin	0.3 mg L−1	1.5–60.5 mg L−1	Apple juices	Sensitive, selective, accurate, short incubation time (30 min)/Failure to report stability, reproducibility	[78]