We show that the plasmon modes of
vertically stacked Ag–SiO2–Ag nanodisks can
be understood and classified as hybridized
surface and edge modes. We describe their universal dispersion relations
and demonstrate that coupling-induced spectral shifts are significantly
stronger for surface modes than for edge modes. The experimental data
correspond well to numerical simulations. In addition, we estimate
optical intensity enhancements of the stacked nanodisks in the range
of 1000.
Understanding of the phase transition dynamics of substrate tethered brushes of thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) is important for their application as, e.g., cell substrates with spatially selective cell affinity or drug delivery systems. But characterization of the brushes phase transition time is hampered by the low amount of involved pNIPAM. Here, by the simultaneous use of time resolved nanoplasmonic heating and sensing, we are able to measure a transition time of 160±20 μs for a 30 nm thick substrate tethered brush. The plasmon-induced temperature jump can be quantitatively deduced from the measured data. Nanoplasmonic platforms as applied here could serve as local and fast probes for a variety of dynamic processes in stimuli responsive molecules or polymers.
A gold nanoparticle is scanned with a dielectric tip while optical scattering spectra are acquired for each tip position to map plasmon resonance changes.
We analyze the photoluminescence intermittency (blinking) of single colloidal CdSe/ZnS quantum dots (QDs). Two distinct emission levels, a bright on-state and a low-intensity gray state, correspond to monoexponential decay times of 58[Formula: see text]ns and 4[Formula: see text]ns, respectively. The ratio gray/on states increases upon increasing excitation intensity. Conversely, the gray/on level intensity ratio increases upon coupling to a plasmonic nanostructure, while the states maintain their monoexponential character. Corroborated by data from a CdSeTe/ZnS QD, our results demonstrate that type I QDs can indeed show a gray (rather than completely dark) emission level with a distinct monoexponential decay, a point that is discussed controversially in the literature.
The combination of single photon emitters (quantum dots) and tailored metal nanoparticles with defined size and shape allows a detailed study of the interaction between light and matter. The enhanced optical near-field of the nanoparticles can strongly influence the absorption and emission of nearby fluorescent quantum dots. We show that a controlled spatial arrangement enables the analysis and understanding of polarization dependent coupling between a metal nanoparticle and few or single fluorescent quantum dots. Modifications in the fluorescence spectrum and lifetime are analyzed and compare well with simulations.The reduction of the fluorescence lifetime in such systems is usually in the order of 3-10. However, much larger reductions are to be expected if the quantum dots are positioned in a nanometric gap between two plasmonic nanoparticles, eventually leading to hot luminescence. We approach this regime experimentally and present first results from lithogaphically fabricated gold particle-pairs with controlled gap widths in the range of 1-20nm.
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