The light-up fluorescence of AgNCs in a "DNA bulb"

In this presented work, a series of designs and experiments have been constructed to study how a DNA structure affected the fluorescence of silver nanoclusters (AgNCs). A "bulb"-like DNA structure was firstly used as the synthesizing template, and bright green-emitting AgNCs were obtained with a quantum yield of 17.2%. The "DNA bulb" structure was assembled using three single-stranded oligonucleotides (ssDNAs), with a flexible ssDNA part serving as the "filament". The results seemed intriguing as luminous AgNCs could be obtained only when the complete spatial structure was formed. To further investigate the role of the "bulb" structure, thirteen cytosine-rich sequences were employed as the "filament", respectively. Interestingly, the fluorescence intensities of AgNCs were all enhanced after the "filament" ssDNA was integrated into the "bulb" structure. The enhancement was as much as 175.2-fold, and the minimum enhancement was 1.3-fold. Spectral analyses were then conducted to give an understanding of the role of cytosine. When the sequences in the "bulb shell" were changed, the "DNA bulb" structure still showed an enhancing effect. Finally, the green-emitting AgNCs were utilized toward the selective detection of Hg²⁺ to demonstrate potential applications.