Silver nanoparticle on aluminum mirror: active spectroscopy and decay rate enhancement

IR luminescence of plexcitonic structures based on Ag2S/L-Cys quantum dots and Au nanorods

The luminescence properties of Ag₂S quantum dots passivated with L-Cysteine (Ag₂S/L-Cys QDs) are studied in the presence of Au nanorods passivated with cetyltrimethylammonium bromide molecules (Au/CTAB NRs). The effect of plasmonic Au/CTAB NRs on IR trap state luminescence (750 nm) is considered. It has been found that the direct interaction between the components of the plexcitonic nanostructure leads to a significant luminescence quenching of Ag₂S/L-Cys QDs, with the luminescence lifetime being constant. This is the evidence for photoinduced charge transfer. The spatial separation of the components of plexcitonic nanostructures due to the introduction of a polymer - Poly(diallyldimethylammonium chloride) (PolyDADMAC) provides a means to change their mutual arrangement and achieve an increase in the IR trap state luminescence intensity and a decrease in the luminescence lifetime from 7.4 ns to 4.5 ns. With weak plexcitonic coupling in the nanostructures [Ag₂S QD/L-Cys]/[PolyDADMAC]/[Au/CTAB NRs], the possibility of increasing the quantum yield of trap state luminescence for Ag₂S QDs due to the Purcell effect has been demonstrated.

The structural and luminescence properties of plexcitonic structures based on Ag2S/l-Cys quantum dots and Au nanorods

A technique of obtaining plexitonic structures based on Ag₂S quantum dots passivated with l-cysteine (Ag₂S/l-Cys QDs) in the presence of Au nanorods passivated with cetyltrimethylammonium bromide molecules (Au/CTAB NRs) with controlled luminescence properties has been developed. The structural and luminescence properties of Ag₂S/l-Cys QDs with Au/CTAB NRs are studied. The effect of plasmonic Au/CTAB NRs on IR trap state luminescence (750 nm) is considered. It has been found that the direct interaction between the components of the plexcitonic nanostructure leads to a significant luminescence quenching of Ag₂S/l-Cys QDs, with the luminescence lifetime being constant. This is the evidence for photoinduced charge transfer. The spatial separation of the components of plexcitonic nanostructures due to the introduction of a polymer – poly(diallyldimethylammonium chloride) (polyDADMAC) provides a means to change their mutual arrangement and achieve an increase in the IR trap state luminescence intensity and a decrease in the luminescence lifetime from 7.2 ns to 4.5 ns. With weak plexcitonic coupling in the nanostructures [Ag₂S QD/l-Cys]/[polyDADMAC]/[Au/CTAB NRs], the possibility of increasing the quantum yield of trap state luminescence for Ag₂S QDs due to the Purcell effect has been demonstrated. In the case of formation [Ag₂S QD/l-Cys]/[polyDADMAC]/[Au/CTAB NRs] a transformation of shallow trap state structure was established using the thermostimulated luminescence method.

A technique of obtaining plexitonic structures based on Ag₂S quantum dots passivated with l-cysteine (Ag₂S/l-Cys QDs) in the presence of Au nanorods passivated with cetyltrimethylammonium bromide molecules (Au/CTAB NRs) with controlled luminescence was developed.

Hybrid cube-in-cup nanoantenna: towards ordered photonics

The most significant goal of nanophotonics is the development of high-speed quantum emitting devices operating at ambient temperature. In this regard, plasmonic nanoparticles-on-mirror are potential candidates for designing high-speed photon sources. We introduce a novel hybrid nanoantenna (HNA) with CdSe/CdS colloidal quantum dots (QDs) based on a silver nanocube in a metal cup that presents a nanoparticle-in-cavity coupled with an emitters system. We use focused ion beam nanolithography to fabricate an ordered array of cups, which were then filled with colloidal nanoparticles using the most simple drop-casting and spin coating methods. The spectral and time-resolved studies of the samples with one or more nanocubes in the cup reveal a significant change in the radiation characteristics of QDs inside the nanoantenna. The Purcell effect causes an increase in the fluorescence decay rate (≥30) and an increase in the fluorescence intensity (≥3) of emitters in the HNA. Using the finite element method simulations, we have discovered that the proximity of the cups wall affects the oscillation modes of the gap plasmon, which, in turn, leads to changes in the electric field enhancement inside the nanoantenna gap. Additionally, substantial variations in the behavior of the gap plasmons at different polarizations of the exciting radiation have been revealed. The proposed nanoantenna can be useful in the development of plasmonic sensors, display pixels, and single-photon sources.

Locating Single-Atom Optical Picocavities Using Wavelength-Multiplexed Raman Scattering

Transient atomic protrusions in plasmonic nanocavities confine optical fields to sub-1-nm³ picocavities, allowing the optical interrogation of single molecules at room temperature. While picocavity formation is linked to both the local chemical environment and optical irradiation, the role of light in localizing the picocavity formation is unclear. Here, we combine information from thousands of picocavity events and simultaneously compare the transient Raman scattering arising from two incident pump wavelengths. Full analysis of the data set suggests that light suppresses the local effective barrier height for adatom formation and that the initial barrier height is decreased by reduced atomic coordination numbers near facet edges. Modeling the system also resolves the frequency-dependent picocavity field enhancements supported by these atomic scale features.