A label-free "SEF-FRET" fluorescent sensing platform for ultrasensitive DNA detection based on AgNPs SAMs

In this paper, deoxyribonucleic acid (DNA) with different lengths were used to control the distance between carbon dots (CDs) and silver nanoparticles (AgNPs) in self-assembled multilayers (SAMs). Surface-enhanced fluorescence and fluorescence resonance energy transfer (SEF-FRET) could be achieved based on changing DNA strands. The fluorescence intensity of CDs SAMs with 6-base DNA strands could be enhanced up to ca. 5.6 times by AgNPs. As-fabricated CDs SAMs with excellent luminescent properties, superior stability have been employed for the development of a label-free fluorescence sensing platform for DNA detection. Since DNA would hybridize with the complemented one which was attached on the surface of SAMs, resulting in a close distance between CDs and AgNPs, FRET could thus occur between AgNPs and CDs, resulting in quenching the fluorescence of CDs SAMs. This sensitive sensing platform could show excellent analytical performance for detecting DNA with a linear response ranging from 93.07 pM to 5.433 nM and a detection limit of 16.36 pM, which could be further employed to probe human blood samples. This could prove a promising method for the detection of DNA.