The effect of core@shell nanostructure of Ag@TiO2 on the spectral-luminescence properties of polymethine dye (PD) functionalized with sulfonate group and its photovoltaic properties in the PD dye-sensitized solar cell were investigated. Quenching in the fluorescence intensity of PDs molecule by almost 3 times was observed for the dye-absorbed titanium dioxide porous film. Furthermore, the decreasing effect in fluorescence lifetime was found to be significant for the PD molecules modified with functional groups. In the presence of Ag@TiO2 nanoparticles (NPs), an increase in the luminescence intensity of PD by 60 -90 % was observed. A mechanism of plasmon nanoparticles' effect on the decay of the excited states of dye molecules was proposed. The efficiency of PD-sensitized solar cells was increased by 1.2 times for PD 1 and 2.0 times for PD 2. The enhancement in the efficiency is result from the growth in the spectral sensitivity of solar cell in the region of 400 -450 and 600 -700 nm and a change in the charge-transport parameters of TiO2 films. This increase was supported by a decrease in the resistance at the semiconductor-dye interface by 8.2 times for PD 1 and 22.4 times for PD 2 that leads to the growth in the part of photoelectrons reaching the counter electrode in solar cell with plasmon NPs.
The effect of silver nanoparticles (NPs) on the spectral-luminescence and lasing properties of an ethanolic solution of positive solvatochromic merocyanine dye is studied. Increases in the absorption cross section, intensity, and duration of dye fluorescence are observed upon the addition of NPs to the solution. This leads to a decrease in the merocyanine lasing threshold. As a result, laser generation can be obtained in the presence of silver NPs (С Ag = 10 −12 mol/L) at a dye concentration (10-4 mol/L) at which it cannot be achieved in the absence of NPs. It is noteworthy that the power density of laser pumping in the former case is lower than in the latter case.
The effect of laser radiation on the structural and optical properties of graphene oxide dispersed in water was studied. It was shown that under laser ablation a significant reduction in the size of graphene oxide sheets can be achieved. In this case, the resulting main parts of particles have a size of about 110–120 nm, and are similar to graphene quantum dots. The Raman spectra indicate the reduction of graphene oxide during laser radiation. The thickness of the formed particles practically was not changed, since the ID/IG ratio has close values. The prepared dispersions of graphene oxide exhibit wide luminescence bands in the region of 400–600 nm with a maximum of about 450 nm and a lifetime of 1.6 ns. It was shown that by laser ablation it is possible to achieve a significant increasing in the luminescent ability of graphene oxide in an aqueous solution. In this case, the luminescence intensity increased by almost 2 times, while the optical density of the solution was increased by only 5 % relative to the initial dispersion. The results can be used to create organic luminescent materials, in optical nanotechnology, as well as in photovoltaics, biophysics and bioimaging.
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