Ultrafast coherence transfer in DNA-templated silver nanoclusters

Sidsel Ammitzbøll Bogh,Miguel R Carro-Temboury,Donatas Zigmantas,Erling Thyrhaug,Tom Vosch,Charlotte Stahl Madsen

doi:10.1038/ncomms15577

Sidsel Ammitzbøll Bogh, Miguel R Carro-Temboury + Show 4 more

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https://doi.org/10.1038/ncomms15577

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Abstract

DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure and dynamics in these clusters. Here we report on a multidimensional spectroscopy investigation of the energy-level structure and the early-time relaxation cascade, which eventually results in the population of an emitting state. We find that the ultrafast intramolecular relaxation is strongly coupled to a specific vibrational mode, resulting in the concerted transfer of population and coherence between excited states on a sub-100 fs timescale.

Highlights

DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission
The steady-state absorption and emission spectra of Ag20NC in 50/50 citrate buffer/ethylene glycol at 77 K are shown in Fig. 1, overlaid with the laser spectrum used in the ultrafast spectroscopy experiments
The spectral features have alternately been interpreted as arising from plasmon resonances or from transitions in a ‘super-atom’

Summary

Introduction

DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. The broad and strongly red-shifted absorption bands characteristic of these NCs have been interpreted by treating the AuNCs as ‘super-atom’ cores with associated ligand-perturbed surface states[3,4,5] These studies have been greatly aided by available crystal structures of several AuNC species[5,6], allowing for meaningful electronic structure calculations. To elucidate some aspects of the electronic structure and dynamics of these NCs we focus on an AgNC investigated by Petty et al.[7,24,25] and Shultz et al.[26], which has relatively well-characterized steadystate optical properties This AgNC comprises 20 silver atoms and two C3AC3AC3TC3A DNA oligonucleotides, and is here referred to as Ag20NC. We determine the phenomenological electronic structure of the cluster, and further demonstrate that excited-state population relaxation in the Ag20NC system is ultrafast and proceed in conjunction with transfer of vibrational coherence between excited-state surfaces

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