One notable outcome, published in an open access peer-reviewed article, describes a facile method to obtain gold nanorod-containing yolk-shell nanoparticles by the formation of a polystyrene sulphonate shell with simultaneous hydrolysis of a previously grown sacrificial silica template in an aqueous medium. The resulting particles are extraordinarily stable in both polar and nonpolar solvents and exhibit a high loading capacity for organic dyes and can be used for spaser applications.
Also, in an attempt to shift the generation peak of the spasers emitting in the visible to the near IR range, a three-dimensional silica-based photonic crystal (PhC) film was infiltrated with spasers, composed of spherical gold cores, surrounded by silica shells with dye molecules. Our experiments show that such a structure, consisting of a photonic crystal, which acts as an external distributed feedback resonator, and spasers, can serve as a coherent source of electromagnetic radiation. Spasers were locked in phase by the common radiation causing a phenomenon called the lasing spaser: the emission of spatially and temporarily coherent light normal to the surface of the PhC film. The far-field radiation patterns appeared in the shape of the Star-of-David, which is due to the dispersion along the Brillouin zone boundary. The infiltration of the spasers into the PhC led to drastic narrowing of the emission peak and an 80-fold decrease in the spaser generation threshold with respect to the same spasers in a suspension at room temperature. Moreover, the optical properties of gold nanorods-based particles infiltrated with a number of organic dyes were investigated. The impact of the dye nature, its concentration, shell thickness, pumping power, and other parameters on generation characteristics (threshold values, gain factors, peak width, etc.) were studied. The SPIR project has made a significant contribution to the development and experimental implementation of plasmonic nanolasers, with potential applications in biomedicine and other areas.