Fluorescent resonance energy transfer of organic fluorescent dyes with gold nanoparticles and their analytical application

Abstract

We report five effective fluorescence resonance energy transfer (FRET) systems based on gold nanoparticles (AuNPs) and organic fluorescent dyes, including ionic [fluorescein sodium (FS) and Eosin B (EB)] and cationic [rhodamine 6G (Rh6G), acridine orange (AO), and safranine T (ST)] fluorescent dyes. The fluorescence intensity of the five FRET systems demonstrates that efficient quenching is possible. The quenching efficiencies of Rh6G and FS by FRET were nearly 100%, 89% for AO, 60% for EB, and 55% for ST. A series of UV absorbance spectra and fluorescence emission spectra were used to explain the mechanism of fluorescence quenching. We found that there were different degrees of overlap between the absorption spectrum of the AuNPs and the emission spectrum of fluorescence dyes. This outcome indicates that highly efficient FRET is the possible mechanism of fluorescence quenching. We applied the FRET system to establish a sensitive and simple strategy for the determination of mercury (Hg2+). The maximum excitation was at 523 nm (λex = 523 nm). The enhanced fluorescence intensity at 551 nm was proportional to the concentration of Hg2+ with a range of 0.44–100 nmol L−1. The detection limit was 0.13 nM. The linear regression equation was ΔF = 27.05c (nmol L−1) − 79.88, and the regression coefficient was 0.9954. The proposed method has high sensitivity and convenience and does not require complex and expensive instruments.