Silver Nanoparticle Aggregates as Highly Efficient Plasmonic Antennas for Fluorescence Enhancement

The enhanced local fields around plasmonic structures can lead to enhancement of the excitation and modification of the emission quantum yield of fluorophores. So far, high enhancement of fluorescence intensity from dye molecules was demonstrated using bow-tie gap antenna made by e-beam lithography. However, the high manufacturing cost and the fact that currently there are no effective ways to place fluorophores only at the gap prevent the use of these structures for enhancing fluorescence-based biochemical assays. We report on the simultaneous modification of fluorescence intensity and lifetime of dye-labeled DNA in the presence of aggregated silver nanoparticles. The nanoparticle aggregates act as efficient plasmonic antennas, leading to more than 2 orders of magnitude enhancement of the average fluorescence. This is comparable to the best-reported fluorescence enhancement for a single molecule but here applies to the average signal detected from all fluorophores in the system. This highlights the remarkable efficiency of this system for surface-enhanced fluorescence. Moreover, we show that the fluorescence intensity enhancement varies with the plasmon resonance position and measure a significant reduction (300×) of the fluorescence lifetime. Both observations are shown to be in agreement with the electromagnetic model of surface-enhanced fluorescence

Accurate and convergent T-matrix calculations of light scattering by spheroids

The convergence behavior of the T-matrix method as calculated by the extended boundary condition method (EBCM) is studied, in the case of light scattering by spheroidal particles. By making use of a new formulation of the EBCM integrals specifically designed to avoid numerical cancellations, we are able to obtain accurate matrices up to high multipole order, and study the effect of changing this order on both the individual matrix elements and derived physical observables. Convergence of near- and far-field scattering properties with a relative error of 10−15 is demonstrated over a large parameter space in terms of size, aspect ratio, and particle refractive index. This study demonstrates the capability of the T-matrix/EBCM method for fast, efficient, and numerically stable electromagnetic calculations on spheroidal particles with an accuracy comparable to Mie theory

Prediction of the properties of annealed InAs/GaAs quantum dot samples assuming conservation of Indium atoms

No abstract available

Radiative decay and carrier relaxation in annealed InAs/GaAs self-assembled quantum dots

No abstract available

Time-resolved studies of annealed InAs/GaAs self-assembled quantum dots

We have investigated the carrier dynamics in annealed quantum dots where the energy-level separation of the optical transitions can be tuned between 68 and 19 meV. Photoluminescence transients obtained for different excitation densities for the ground and excited states are well described by a random population model, and values of the exciton lifetimes extracted. The ground-state radiative lifetimes are found to vary from 800 ps in the as-grown sample to 490 ps in the sample annealed at the highest temperature. This is attributed to shifts in the emission energy and changes in the electron and hole wave-function overlap as the dot size increases with annealing. We find no evidence of inhibited relaxation of carriers (phonon bottleneck) when the intersublevel energy-level separation is much less than the LO-phonon energies. The rise times of the transients remain fast at low excitation density, where the probability of Coulomb scattering is expected to be low, meaning that another mechanism, possibly multiphonon scattering, is responsible for the fast relaxation observed in self-assembled quantum dots

Radiative decay and carrier relaxation in annealed InAs/GaAs self-assembled quantum dots

No abstract available

Tuning InAs/GaAs self-assembled quantum dots to investigate relaxation processes

No abstract available

Tuning InAs/GaAs self-assembled quantum dots to investigate relaxation processes

No abstract available