Long-lived Ag106+ luminescence and a split DNA scaffold

Abstract

Molecular silver clusters emit across the visible to near-infrared, and specific chromophores can be formed using DNA strands. We study C4AC4TC3G that selectively coordinates and encapsulates Ag106+, and this chromophore has two distinct electronic transitions. The green emission is strong and prompt with ϕ = 18% and τ = 1.25 ns, and the near-infrared luminescence is weaker, slower with τ = 50 µs, and is partly quenched by oxygen, suggesting phosphorescence. This lifetime can be modulated by the DNA host, and we consider two derivatives of C4AC4TC3G with similar sequences but distinct structures. In one variant, thymine was excised to create an abasic gap in an otherwise intact strand. In the other, the covalent phosphate linkage was removed to split the DNA scaffold into two fragments. In relation to the contiguous strands, the broken template speeds the luminescence decay by twofold, and this difference may be due to greater DNA flexibility. These modifications suggest that a DNA can be structurally tuned to modulate metastable electronic states in its silver cluster adducts.

Probing emission of a DNA-stabilized silver nanocluster from the sub-nanosecond to millisecond timescale in a single measurement

“…The latter was previously demonstrated by Petty et al and must be the case when all states are connected in a classic three-level system. 12 To verify whether the microsecond lived luminescent state of DNA-Ag 16 NC is capable of OADF, experiments were conducted by co-illuminating with a primary (520 nm) and a secondary (850 nm) excitation source able to regenerate the uorescent state (Fig. 1b).…”

“…11,12 While nanosecond decay times have been reported for DNA-AgNCs using time-correlated single photon counting (TCSPC), longer lived microsecond luminescence has only been very recently reported using pulsed Xe ash lamps or burst mode measurements. [11][12][13] DNA-AgNCs have long been known to possess microsecond lived dark states, which manifest themselves as uorescence blinking in single molecule and uorescence correlation experiments. [14][15][16] Considered to be non-emissive, these dark states have been utilized to generate background-free imaging capabilities by modulating the uorescence intensity output or by exploiting a process called optically activated delayed uorescence (OADF).…”

“…As such, DNA-AgNCs, with emission spanning the visible 6,7 and near-infrared (NIR) 8,9 range, have been prepared with decay times in the nano-10 and microsecond regimes. 11,12 While nanosecond decay times have been reported for DNA-AgNCs using time-correlated single photon counting (TCSPC), longer lived microsecond luminescence has only been very recently reported using pulsed Xe ash lamps or burst mode measurements. [11][12][13] DNA-AgNCs have long been known to possess microsecond lived dark states, which manifest themselves as uorescence blinking in single molecule and uorescence correlation experiments.…”

“…Time gating allows one to extract the OADF signal and generate a background free Anti-Stokes signal. 17 The recent discovery of microsecond emission from DNA-AgNCs, 11,12 led us to wonder whether these states are also able to generate OADF.…”

DNA Stabilizes Eight-Electron Superatom Silver Nanoclusters with Broadband Downconversion and Microsecond-Lived Luminescence

“… 22 Similarly, Petty et al reported an unpurified Ag N -DNA with dual green fluorescence and NIR phosphorescence. 37 In contrast, 800-Ag N -DNA and 760-Ag N -DNA show only microsecond-lived luminescence with no significant nanosecond-lived fluorescence. This suggests that the electronic structures of 800-Ag N -DNA and 760-Ag N -DNA differ from most previously investigated Ag N -DNAs characterized by nanosecond-lived fluorescence.…”