Tetrahedral DNA nanocaged gold nanoclusters with enhanced optical features for accurate ion quantification.

Despite great progress of fluorescent gold nanoclusters (AuNCs), challenges still exist to improve their stability and optical performances. We herein fabricate a unique strategy by encapsulating DNA-templated AuNCs with additional three-dimensional tetrahedral DNA nanocage, enabling controlled spatial confinement and enhanced fluorescence emission. Phosphorothioate-modified DNA template is designed with sequences to be connected with the internal framework of DNA tetrahedron, which guides the encapsulation. Due to the rigid DNA nanostructure, restriction of intramolecular motion (RIM) occurs, which contributes to the reduction in non-radiative decay of the excited state and the enhancement of fluorescence emission. The nanocaged AuNCs exhibit more stable conformation, which are successfully applied for highly sensitive detection of heavy metal ions including Ag+, Hg2+, and Pb2+. The nanomaterials are demonstrated to be promising fluorescent reagents and applicable for intracellular bioimaging, which hold great potential value for practical ion identification.