Fluorescence resonance energy transfer from NaYF4:Yb,Er to nano gold and its application for glucose determination

This manuscript proposes a fluorescence resonance energy transfer (FRET) system which could be used for the rapid, selective, and sensitive detection of glucose levels. In this system, chitosan modified gold nanoparticles (AuNPs-CS) serve as a quencher. Because concanavalin A (conA) and chitosan (CS) have specific binding sites, FRET could occur between conA modified NaYF4:Yb, Er (NaYF-conA) and CS modified gold nanoparticles (AuNPs-CS), and lead to the fluorescence quenching of NaYF4:Yb, Er (NaYF). The system switches to the “off” state. However, glucose have stronger binding energy with conA than CS with conA. When glucose is added into the AuNPs-CS and NaYF-conA system, the AuNPs-CS detaches from NaYF-conA, the fluorescence of NaYF is recovered, and the system switches to the “on” state. Thus, a new method for determining glucose levels is proposed by measuring the fluorescence intensity. This method shows a linear response to glucose in the range of 0.40-1.87 μmol/L, with good linear relationship (R = 0.98, n = 7). The limit of detection is as low as 0.02 μmol/L.