Organic solids can be used as emitters in organic solid-state lasers. As one of the most popular red light-emitting organic laser dyes is DCM that has been widely used in a dye laser. It has been used in solid-state lasers. The active material was host-guest systems where DCM was doped at low concentration due to large intermolecular interactions. We previously developed original glass-forming DCM derivatives were attached bulky triphenyl groups reduced intermolecular interaction thus it was possible to observe amplified spontaneous emission (ASE) in the neat films.
In this work, we are presenting new derivatives with modified electron acceptor and donor groups. The investigated compounds are pyranyliden derivatives with malononitrile and 1H-indene-1,3(2H)-dione as acceptor and bis(5,5,5-triphenylpentyl)amino- and 5,5,5-triphenylpentyl-piperazin-1-yl- as donor. Photoluminescence and ASE were investigated in thin films. All compounds emit light in red spectral regain with the photoluminescence quantum yield of up to 6%. Amplified spontaneous emission excitation threshold energy was about 100 μJ/cm2.
Silver nanoparticles were used to increase the performance of the compounds. Triangular nanoparticles with the surface plasmon resonance (SPR) overlapping the absorption and emission spectra of compounds were used. Metal nanoparticles were dissolved in the organic solution with investigated compounds. The solution was ultrasonicated prior to deposition on a glass substrate by the spin-coating method.
SPR enhance the absorption and emission of the investigated compounds. Accordingly, it was observed as at least two times increase in the PLQY of mixed thin films and more than two times were decreased excitation threshold energy of ASE. More detailed results and metal nanoparticle influence on emission properties of investigated compounds will be discussed.
In this paper, we present a study on nonlinear optical effects in two types of core-shell nanoparticles with different claddings - thiol-termination ligand and sodium citrate/PVP claddings. Nanoparticles were dissolved in Dichloromethane and studied using the Z-scan method. As laser sources we used a tunable laser with 150 fs pulse width and 500 kHz pulse repetition rate. To study what processes lead to refractive index changes we used the polarization-resolved Z-scan method. A strong thermal response was observed for spherical nanoparticles. Both nanoparticles had similar spectral dispersion for Two-photon absorption, but spherical had a much stronger Kerr response.
Metal nanoparticles have been very active research object due to the local surface plasmon resonance effect that can be used in various applications, such as sensors, photovoltaic and Raman spectroscopy. Metallic nanoparticles enhanced fluorescence is an important effect to improve the emission properties of the semiconductor. It offers higher emission efficiency and decreased lifetime via the local electric field enhancement effect of metal nanoparticles induced by its surface plasmon resonance. Initially, inorganic semiconductors were used to show the emission enhancement, but recently more systems consist of organic semiconductors. It is driven by the growing potential of organic materials in the light-emitting diodes, photovoltaics, and solid-state lasers. Synthesis of specific size and shape of nanoparticles is important because it determines the spectrum of surface plasmon resonance which in turn should match the emission spectrum of an organic dye to get the highest enhancement. Silver nanoparticles typically are synthesized in aqueous solution and their transfer to organic solvents is required for application purposes in organic luminophores emission intensity enhancement. We studied prismatic and spherical silver nanoparticles transfer from aqueous to organic media by ultrasonic treatment and shell changing processes. Photoluminescence properties – emission maps, photoluminescence quantum yield and lifetime of obtained nanoparticles solutions mixtures with organic luminophore DWK-1-TB (2-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4-ylidene)malononitrile) were studied. Improvements of photoluminescence properties was observed in nanoparticles based organic luminophore solutions. Presence of nanoparticles increased emission intensity, improved photoluminescence quantum yield and shifted excitation wavelength.
The luminescence of organic semiconductors can be enhanced by surface plasmon resonance on metal nanoparticles, so it can pave the way for the development of light modulators, laboratory chips or sensors based on organic semiconductors. Silver nanoprisms and nanospheres are two-dimensional plasmonic nanostructures that have attracted massive attention due to their strong shape-dependent related applications and optical properties. When the lateral dimension of silver nanoplates is much larger than the thickness, they possess a very great degree of anisotropy, which favors a high tunability of their localized surface plasmon resonance and maximum electromagnetic-field enhancement therefore is generated. Within this work, silver nanoparticles (nanoprisms and nanospheres) of different sizes were obtained in aqueous solution, which were stabilized with sodium citrate and PVP (Polyvinipyrrolidone). Most luminophores are insoluble in water, so nanoparticles had to be transferred to the organic environment. This was achieved using the ultrasonic method. The obtained nanoparticle solutions were added to organic luminophore DWK-1-TB solution. Before nanoparticles were applied to thin films together with organic luminophore (DWK-1-TB), their properties (absorption, quantum yield, excitation, emission) were studied. Thin films were coated from these solutions. Thin films were applied by spin coating and blade casting method. Different concentrations of silver nanoparticles solutions were coated, as well as films of different thickness. PMMA (polymethyl methacrylate) was added because the nanoparticles efficiently transfer into the PMMA solution and its presence at low concentrations improves the homogeneity of the thin film. Quantum yield, change in luminescence depending on the type of nanoparticles, as well as film thickness were studied in the obtained samples.
In this paper, we present a study on thermo-optical effect in core-shell silver/thiol-termination ligand nanoparticles. Nanoparticles were dissolved in Dichloromethane. Experimental measurements were carried out using a Z-scan setup. As laser sources we used two 1064 nm lasers: i) 28 ps pulse width laser with 1000 Hz pulse repetition rate; ii) 8 ns pulse width laser with changeable pulse repetition rate 200 – 40 000 Hz. To study what processes lead to refractive index changes we used the polarization-resolved Z-scan method. Comparing ps and ns results showed that response time of single pulse thermal effects for organic solvents depends on beam size while for nanoparticles it corresponds to nanoparticle size. Measurements with ns laser using different lenses and pulse repetition rate showed that thermal response scales with the ratio of laser pulse repetition rate times beam size squared.
The method of synthesis of photosensitive polyurethanes polymers on glycerine, toluenediisocyanate and Disperse Red 1 base has been described. Two types of polymers with different amount of Disperse Red 1 fragments in macromolecules were compared. Films of the polymers were obtained from solutions in organic solvents on glass substrate. The dry film thickness was in the range of 3,5 - 4.5 μm. The transmission spectrums of the films were studied. Possibility of formation of side product in the process of synthesis was observed. The photobirefringence measurements of polymers films were performed. Surface relief grating (SRG) formation was observed during polarization holographic recording process. A profile of SRG was studied by AFM.
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