The role of spacer sequence in modulating turn-on fluorescence of DNA-templated silver nanoclusters

Abstract

Guanine activation of fluorescence in DNA templated silver nanoclusters (AgNCs) is an interesting physical phenomenon which has yet to be fully understood to date. While the individual role of cytosine and guanine has been established, there is still a knowledge gap on how the AgNC–DNA system switches from dark to bright state. Here, we present evidence on the universal role of the DNA spacer sequence in physically separating two Ag+-binding cytosine sites to maintain the dark state while holding them together for structural re-organization by the guanine-rich strand to activate the bright state. The extent of turn-on signal could be modulated by adjusting the spacer length and composition. The ATATA spacer sequence was found to have negligible dark state fluorescence and a turn-on effect of 2440-fold, which was almost five times of the highest factor reported to date.

Efficient Editing of Silver Nanoclusters by Changing Simply One Cytosine in a DNA Template

“…When the cytosine was placed in position 8, 6, 5, or 4, the obtained templates YS‐3, YS‐4, YS‐5, and YS‐6 were used to form different species with λ ex / λ em =555/626, 630/708, 610/688, and 605/690 nm, respectively (Figure 1C–F), implementing the expected tunable emission. The introduction and moving of one cytosine in the spacer in the emitter can modify the initial structure of AgNCs, which is attributed to the role of spacer in limiting the unordered growth of AgNCs and facilitating the interaction of polycytosine motif [13] …”

The spatial organization of trace silver atoms on a DNA template

“…(G) G enhancer-induced folding of the DNA template secondary structure for forming bright AgNCs. 74,75 changes from 400 nm (violet cluster) to 730 nm (near-infrared cluster), which is attributed to the silver-mediated intermolecular antiparallel cluster dimer with twice silver stoichiometry alteration 68,69 (no. 5 in Table 2).…”

Establishing empirical design rules of nucleic acid templates for the synthesis of silver nanoclusters with tunable photoluminescence and functionalities towards targeted bioimaging applications

“…11,[28][29][30] Since the seminal work of using DNA molecules as stabilizers (or templates) to form photoluminescent silver nanoclusters (AgNCs) by Dickson and coworkers in 2004, 31 the fundamental study and applications of DNA-templated AgNCs (DNA-AgNCs) have witnessed dramatic advancements in recent years. [32][33][34][35][36] These DNA-AgNCs are typically smaller than 2 nm, 37 approaching the Fermi wavelength of electrons. Due to strong quantum connement, the continuous density of states present in the bulk metals are broken up into discrete energy levels which give rise to optical, electrical and chemical properties distinctly different from those of the bulk metal and metal nanoparticles of larger sizes.…”