Near-infrared photophysics of decanucleotide-templated silver nanoclusters

DNA-templated silver nanoclusters (DNA-AgNCs) represent a unique class of fluorescent nanostructures whose photophysical properties are determined by the nucleotide sequence. Their small size, biocompatibility, and sequence-programmable emission make them of interest for biomedical imaging, particularly within the near-infrared transparency window where tissue scattering and autofluorescence are minimised. Herein, three decanucleotide-templated AgNCs emitting in the near-infrared (NIR) region are reported, with emission maxima at 739 nm, 700 nm, and 666 nm. The sequences were selected and minimally altered from previously reported motifs to compare the photophysical behaviour of the resulting DNA-AgNCs. The steady-state and time-resolved properties of the HPLC-purified species were characterised in detail. The average lifetimes ranged from 1.77 ns to 3.27 ns, and the hydrodynamic volumes suggest structures stabilised by two DNA strands. Temperature-dependent measurements revealed that two of the clusters display less than 10% lifetime variation between 5 °C and 35 °C, indicating low nonradiative contributions. Notably, a cluster derived from a modified sequence of a previously reported NIR emitter displayed improved thermal stability while maintaining comparable emission properties, highlighting the sensitivity of these systems to small sequence alterations.