ULTRASENSITIVE DETECTION OF SILVER IONS IN AQUEOUS SOLUTION BY DNA BASED GOLD NANOPARTICLES

Abstract

In this study, three methods are developed to sensitively and selectively detect silver ions, including colorimetric method, fluorescence method and two-photon photoluminescence (TPPL) method. All these methods are based on the reaction between silver ions and cytosine base (C) in the DNA, which decreases the protection ability of single strand DNA for AuNPs, leading to the aggregation of AuNPs in the presence of salt. These three methods have different sensing mechanisms based on different properties of AuNPs, i.e. colorimetric method based on the the size and shape effect on LSPR, fluorescence method based on FRET and metal enhanced fluorescence effect between AuNPs and fluorescent substance (RITC), TPPL method based on the interparticle plasmon coupling and local field enhancement of AuNPs. All of the three methods display excellent sensitivity and selectivity. In addition, TPPL method demonstrates the best detection limit and range while colorimetric method performs the easiest detection process.