Periodic Reporting for period 1 - SPIR (Spasers in the infrared range)
Berichtszeitraum: 2020-09-01 bis 2022-08-31
One of the most important tasks of modern medicine is noninvasive diagnostics. The cruciality of the problem is determined by the search of sparing and reliable techniques for medical analysis when the patient does not feel pain, physical and emotional discomfort. Plasmonic nanolaser also known as SPASER (the acronym from surface plasmon amplification by stimulated emission of radiation) is a quantum generator providing unprecedented efficiency as a versatile tool in nanotechnology or biomedical research and applications. The spasers are able to generate in a single mode with a very high spectral intensity and density. The above makes the spasers, conceivably, the best multifunctional, super-contrast, low-toxic optical probes for biomedical research and applications. It might make it possible to exploit spasers for the treatment of severe diseases for instance cancer. To investigate spaser generation in a living organism it is imperative that their generation line should be located in the transparency window of biological tissues, namely in the near infrared (IR) range of the electromagnetic spectrum. Therefore, the main objectives of SPIR are the development of synthetic approaches for IR-emitting spasers creation in biocompatible aqueous solution as well as the investigation of their optical characteristics. Since the project has a pronounced multidisciplinary character and is at a junction of inorganic, physical, colloidal chemistry, as well as optics and laser physics, the benefits of the project can potentially be taken not only by medicine, but also by other areas. The examples of potential application may include the creation of high-precision sensors, fabrication of ultra-fast photonic nanocircuits, heavy-duty laser creation, etc. The knowledge obtained in the framework of the project has a significantly impact on the nano- and biotechnological industry of the European Union and improve European competitiveness in various industrial areas.
To achieve the project’s goals, plasmonic nanolasers (spasers) were fabricated using wet chemistry methods, and their optical properties were studied. The spaser particles consisted of gold nanorods surrounded with mesoporous silica shell or gold nanorods-based hollow particles (yolk-shell particles) with infiltrated organic dyes molecules. All type of the spasers obtained were investigated by a complex of physicochemical methods, including scanning and transmission electron microscopy to study morphological features; Raman spectroscopy and energy-dispersive analysis for studying the chemical composition; spectroscopy of dynamic light scattering to determine the average particle size, their hydrodynamic and electrokinetic characteristics etc. Spatial, spectral and threshold characteristics of spaser generation were established. The results were published in open access peer-reviewed journals, presented in a number of international conferences, inner workshops, and disseminated over social platforms and the internet.
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.
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.