An overview of pioneering papers and the latest research on two-photon absorption and photoluminescence in plasmonic nanoparticles and ultrasmall nanoclusters.
Noble metal nanoclusters allow for the atomically-precise control of their composition. However, to create nanoclusters with pre-defined optical properties, comprehensive description of their structure-property relation is required. Here, we report the gold atom doping impact on one-photon and two-photon absorption (TPA) and luminescence properties of ligated silver nanoclusters via combined experimental studies and time-dependent density functional theory simulations (TD-DFT). We synthesized a series of Ag 25À x Au x -(DMBT) 18 nanoclusters where x = 0, 1 and 5-10. For Ag 24 Au 1 (DMBT) 18 we demonstrate that the presence of the central Au dopant strongly influences linear and non-linear optical properties, increasing photoluminescence quantum yield and two-photon brightness, with respect to undoped silver nanoclusters. With improved TPA and luminescence, atomically-precise AuAg alloys presented in our work can serve as robust luminescent probes e.g. for bioimaging in the second biological window.
Amyloids are broadly
investigated protein misfolding products with
characteristic β-sheet assemblies that have an important role
in neurodegenerative diseases (e.g., Alzheimer’s disease).
While they are usually visualized by staining with Thioflavin-T, Congo
Red, or other fluorescent markers, it still arouses a controversy
over possible staining molecule influence on the amyloid structure
or aggregation process. In this work we present, for the first time,
the polarization analysis of two-photon excited autofluorescence of
amyloids and confirm that polarization dependence of the observed
emission can be correlated with the orientation of fibrils. We show
the potential of two-photon excited autofluorescence for resolution
of molecular organization of fibrils within amyloid superstructures.
This label-free method is compatible with two-photon imaging already
applied in investigation of neurodegeneration model in mice.
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