Recent advances in nanotechnology and optics have paved the way for new plasmonic devices. One of them are nanopatch antennas that are simple and, at the same time, effective devices for localizing the electromagnetic field on a scale of less than 10 nm and can be used in photonic integrated circuits as effective sources of photons, including single-photon sources. In the present study, we investigate the radiative characteristics of a submonolayer of colloidal CdSe/CdS quantum dots that form island structures in a resonator: a cubic silver nanoparticle on an aluminum mirror. For detecting plasmonic nanoparticles on glass or metal surfaces, we propose a new technique involving a tunable laser and a confocal microscope. We provide a comparative study of the luminescence enhancement factors for QDs in the NPAs upon off-resonance excitation and at a wavelength close to the resonance; a significant difference in the luminescence enhancement factors (by order of magnitude) is demonstrated. A 60-fold reduction in the spontaneous emission time, as well as an increase in the radiation intensity by a factor of 330, has been obtained in the experiments. The increase in the spontaneous emission rate demonstrated for the quantum dots is explained by the Purcell effect. Full-wave simulations of electromagnetic fields were carried out for the model of the developed nanopatch antenna; luminescence enhancement factors and radiative efficiencies were calculated as well.
An amorphous carbon film with embedded detonation nanodiamond (DND) particles (a-C:ND) was produced by magnetron sputtering of nanodiamond powder. An Ag film was deposited on the carbon structure by radiofrequency magnetron sputtering. The silver film was irradiated with a 150 eV Ar+ to form plasmonic-active nanoparticles (NP) on the surface of the a-C:ND. The structure of the obtained a-C:ND and a-C:ND/Ag structures were studied by scanning and transmission electron microscopy, electron energy-loss spectroscopy, UV–Visible absorption spectroscopy, Raman spectroscopy, and fluorescence lifetime imaging at two-photon excitation. The analysis revealed 76% of sp3-carbon and a good dispersion of diamond nanoparticles in the a-C. Surface-enhanced Raman scattering (SERS) was applied to investigate the a-C:ND/Ag structure, allowing for the observation of SERS from the sp2-carbon species and the absence of significant a-C:ND damage after Ar+ irradiation of the Ag overlayer. A plasmonic-metal-enhanced luminescence was observed at one- and two-photon excitations, revealing a two- to five-fold intensity increase. The activity of the used DNDs was tested using the agar diffusion method and observed against the bacteria of Bacillus subtilis, Staphylococcus aureus, and Escherichia coli and the fungi of Aspergillus niger, Aspergillus fumigatus, and the yeast of Candida albicans, showing DND activity against all the test strains of fungi.
Ensembles of silver nanoparticles (NPs) with size ~45 nm formed from the silver film using an ion beam modification are studied. The optical spectroscopy demonstrated that the fabricated ensembles of silver NPs keep stable their plasmonic properties in an ambient atmosphere for at least 39 days due to their monocrystalline nature. We use the scanning Raman microscope to map the SERS from Crystal Violet homogeneously adsorbed on these ensembles. It was found that the manufactured ensembles have a strong amplification factor, and this factor is preserved for these ensembles even after more than one month of storage in the surrounding atmosphere. Hereby, by ion beam modification of silver film, it is possible to fabricate the NPs with stable plasmonic properties and form nanostructured surfaces to be applied in sensor technologies and SERS.
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