Fluorescent nitrogen and phosphorus co-doped carbon dots (NPCDs) were prepared via a hydrothermal method with citric acid and O -phosphorylethanolamine as precursors. The overlap between the absorption spectrum of riboflavin and the fluorescence emission spectrum of the NPCDs and the relative proximity of the NPCDs to riboflavin due to hydrogen bonding facilitated the formation of a NPCDs/riboflavin fluorescence resonance energy transfer (FRET) system. Thus, a ratiometric fluorescence method for the detection of riboflavin based on the formation of this NPCDs/riboflavin FRET system was developed. The method displayed a sensitive and selective response to riboflavin in the range 0.5–50 μmol/L with a detection limit of 0.17 μmol/L. It was also found to be suitable for the detection of riboflavin in milk and riboflavin pharmaceutical tablets.
Illustration of the preparation of NPCDs and the ratiometric fluorescence detection of riboflavin using the NPCDs/riboflavin FRET system
Xiao-Lei Zhang,Xue Li,Xiao-Tong Li,Ye Gao,Fang Feng,Gong-Jun Yang
The Au nanoclusters@graphene quantum dots nanocomposite as an electrochemiluminescence (ECL) luminophore was synthesized through amide coupling reaction between Au nanoclusters (Au NCs) and graphene quantum dots (GQDs). The ECL intensity of the as-prepared Au NCs@GQDs was enhanced for 2.6-fold compared with that of Au NCs or 40-fold compared with that of GQDs, which was due to the ECL resonance energy transfer between GQDs as a donor and Au NCs as an acceptor, and excellent electrical conductivity of GQDs. In addition, the synergistic effect likewise improved stability of the ECL signal. A type of “signal-off” solid-state ECL sensor for detection of pentoxifylline was fabricated based on the selective quenching effect of pentoxifylline on the ECL signal of Au NCs@GQDs in alkaline medium. The sensor showed excellent sensitivity and wide linearity for pentoxifylline determination in the range from 7.0 × 10 −7 to 1.2 × 10 -4 mol/L with the detection limit of 9.0 × 10 -8 mol/L (S/N = 3). The proposed method was successfully applied for pentoxifylline detection in pharmaceutical tablet with satisfactory results.
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