Plasmon–exciton coupling is of great importance to many optical devices and applications. One of the coupling manifestations is plasmon-enhanced fluorescence. Although this effect is demonstrated in numerous experimental and theoretical works, there are different particle shapes for which this effect is not fully investigated. In this work electrostatic complexes of gold nanorods and CdSe/CdZnS quantum dots were studied. Double-resonant gold nanorods have an advantage of the simultaneous enhancement of the absorption and emission when the plasmon bands match the excitation and fluorescence wavelengths of an emitter. A relationship between the concentration of quantum dots in the complexes and the enhancement factor was established. It was demonstrated that the enhancement factor is inversely proportional to the concentration of quantum dots. The maximal fluorescence enhancement by 10.8 times was observed in the complex with the smallest relative concentration of 2.5 quantum dots per rod and approximately 5 nm distance between them. Moreover, the influence of quantum dot location on the gold nanorod surface plays an important role. Theoretical study and experimental data indicate that only the position near the nanorod ends provides the enhancement. At the same time, the localization of quantum dots on the sides of the nanorods leads to the fluorescence quenching.

Nanoplasmonics represents one of the most extensive research fields in optics on the nanoscale and has emerging applications in sensors, light-emitting devices, and photovoltaic devices. It offers a number of effects and can be combined with existing technologies by a number of approaches, the colloidal techniques representing the easiest implementation in the existing and emerging photonic components and devices. In this article, plasmonic effects are discussed in terms of three major physical phenomena (incident field enhancement, photon density of states enhancement, and nonradiative decay enhancement) in the context of various photonic processes and devices related to Raman scattering, photo- and electroluminescence, photovoltaics, photochemistry, and photodetectors. A number of instructive examples are given for metal nanospheres and nanorods showing how size, shape, core-shell design, and ambient environment can be used to get maximal use of the favorable factors while keeping unfavorable ones at reasonably safe level. A number of aspects of plasmonically enhanced secondary radiation are emphasized which have not gained close consideration to date. Among them, the following properties are discussed: the decisive role of scattering component of metal-dielectric extinction spectrum overlapping with incident and emitted/scattered light wavelength, valuable contribution to enhancement factors from spacers used to prevent emission quenching but simultaneously affecting the extinction spectrum, a pronounced dependence of enhancement factors on dielectric permittivity of the substrate, dielectric shell, and ambient medium.

Dating back to decades or even centuries ago, colloidal nanophotonics during the last ten years rapidly extends towards light emitting devices, lasers, sensors and photonic circuitry to manifest itself as an emerging technology platform rather than an entirely academic research field.

In the context of using portions of a photosynthetic apparatus of green plants and photosynthesizing bacteria in bioinspired photovoltaic systems, we consider possible control of the chlorophyll excited state decay rate using nanoantennas in the form of a single metal and semiconductor nanoparticle. Since chlorophyll luminescence competes with electron delivery for chemical reactions chain and also to an external circuit, we examine possible excited state decay inhibition contrary to radiative rate enhancement. Both metal and semiconductor nanoparticles enable inhibition of radiative decay rate by one order of the magnitude as compared to that in vacuum, whereas a metal nanosphere cannot perform the overall decay inhibition since slowing down of radiative decay occurs only along with the similar growth of its nonradiative counterpart whereas a semiconductor nanoantenna is lossless. Additionally, at normal orientation of the emitter dipole moment to a nanoparticle surface, a silicon nanoparticle promotes enhancement of radiative decay by one order of the magnitude within the whole visible range. Our results can be used for other photochemical or photovoltaic processes, and strong radiative decay enhancement found for dielectric nanoantennas paves the way to radiative decays and light emitters engineering without non-radiative losses.