Fabrication of fluorescence enhancement of quantum dots on a gold colloid formed film for oligonucleotide DNA detection

A new method based on metal-enhanced quantum dot (QD) fluorescence on a gold colloid formed film has been developed for DNA detection. Gold nanoparticles (Au NPs) with negative charge were uniformly spread on a polylysine-modified glass substrate through electrostatic adsorption to form an Au NP film. The surface plasma resonance of the Au NP film was tuned by heating in an oven for 5 min at 70 °C to match with the fluorescence emission of QDs. DNA was chosen as a spacer to study the distance effect on the metal-enhanced fluorescence of QDs. The maximum enhancement was achieved when the base number of the DNA spacer was 37 (about 12.6 nm). A three segment system based on the optimal length of the DNA spacer has been developed for DNA detection. The lowest detectable limit with this system was 50 nM.