▎ 摘　　要

We have prepared sulfonated graphene (SG) by diazonium coupling technique and it has been characterized by UV-vis absorption spectroscopy, Raman spectroscopy, electron microscopy, energy-dispersive spectroscopy (EDS), EDS elemental mapping, X-ray photoelectron spectroscopy (XPS), and FTIR spectroscopy. The photoluminescence (PL) property of SG at different pH (pH 4, 7, and 9.2) has been investigated and SG shows highest PL-intensity and quantum yield at pH 4 compared to those at higher pH and that of GO at pH 4. Due to the strong overlap between the emission spectrum of SG and absorption spectrum of riboflavin (RE, vitamin B-2) at pH 4, it has been tactfully used as donor for the fluorescence resonance energy transfer (FRET) process. However, graphene oxide (GO) does not exhibit any FRET with RE at an identical condition due to its much lower quantum yield. We have demonstrated a selective detection of vitamin B-2 in presence of nucleic acid (DNA, RNA), protein (BSA), amino acid (Lysine) and other water-soluble vitamins (Becosules, Zevit capsules) based on the spontaneous FRET from PL-active SG (donor) to RE (acceptor). The calibration curve indicates excellent affirmation to detect vitamin B-2 using FRET and it is superior to the ordinary fluorescence method of detecting RE in presence of different biomolecules.