Additive and enhanced fluorescence effects of hairpin DNA template-based copper nanoparticles and their application for the detection of NAD(.).

DNA is an excellent molecular scaffold for the preparation of copper nanoparticles (CuNPs). However, screening and designing an efficient template for the formation of fluorescent CuNPs remains a challenge. Herein, we synthesized CuNPs using a novel hairpin DNA template with a poly T loop and a random double strand stem which performs efficient in the formation of fluorescent CuNPs. Besides, the additive and enhanced effects between the loop and stem sequences on the fluorescence of induced CuNPs was first proposed and investigated. On comparing different sequences, we found that both the circular poly T sequence on the loop region and the stem sequence play important roles in this fluorescence enhancement effect. A label-free analytical system for the quantitative detection of NAD(+) was designed, demonstrating excellent sensitivity. Based on our design concept proposed herein, any random double-stranded DNA can be used for the design of efficient templates for the formation of fluorescent CuNPs in biochemical sensing.