NEW PUBLICATION: Single-Molecule Characterization

Single-Molecule Characterization of Near-Infrared-Emitting Silver Nanoclusters. EN Hooley , V Paolucci , Z Liao , MRC Temboury and T Vosch, Adv. Optical Materials. 2015, 3, 1109–1115. DOI: 10.1002/adom.201500048

Abstract: In this paper, single molecule spectroscopy is used to probe the photophysical heterogeneity of near-infrared emitting silver nanoclusters stabilized in single stranded DNA containing 24 cytosines (C24-AgNCs). Focusing on this subset of emitters allows us to address and correlate their photophysical parameters. The results suggest that for these near-infrared emitting C24-AgNCs, the broad range of observed photophysical properties is due to the spectral heterogeneity of two species, one of which has a broad range of emission maxima and decay times. This conclusion is drawn by analyzing the results of a large number of single C24-AgNCs where, for the first time, emission maxima, fluorescence decay times, fluorescence intensity, blinking, and photon antibunching are determined simultaneously. The single molecule measurements also reveal that some of the C24-AgNCs can change their spectral properties during the measurement, while photon antibunching measurements verified that all the analyzed C24-AgNCs behave as single emitters. While the overall spectral heterogeneity can be related to the immobilization in the polymer film and/or intrinsic heterogeneity of the C24-AgNCs emitters, the exact origin of the dynamical changes has not been fully determined. However, changes in the AgNCs geometry, local environment, or changes in the DNA conformation are possible explanations.