The Pr3+:LaF3 (CPr = 3, 7, 12, 20, 30%) nanoparticles were characterized by means of high-resolution transmission electron microscopy, X-ray diffraction, optical spectroscopy, energy dispersive X-ray spectroscopy, dynamic light scattering, and MTT assay. It was revealed that the average diameter of all the NPs is around 14–18 nm. The hydrodynamic radius of the Pr3+:LaF3 (CPr = 7%) nanoparticles strongly depends on the medium. It was revealed that hydrodynamic radii of the Pr3+:LaF3 (CPr = 7%) nanoparticles in water, DMEM, and RPMI-1640 biological mediums were 18 ± 5, 41 ± 6, and 186 ± 8 nm, respectively. The Pr3+:LaF3 (CPr = 7%) nanoparticles were nontoxic at micromolar concentrations toward COLO-320 cell line. The lifetime curves were fitted biexponentially, and for the Pr3+:LaF3 (CPr = 7%) NPs, the luminescence lifetimes of Pr3+ ions were 480 ± 2 and 53 ± 5 nanosec.
In this work we develop an approach of automatic recognition of ellipsoidal particles on the atomic force microscopy (AFM) image and determination of their size, which is based on image segmentation and the surface approximation by ellipsoids. In addition to the comparative simplicity and rapidity of processing, this method allows us to determine the size of particles, the surface of which is not completely visible on the image. The proposed method showed good results on simulated images including noisy ones. Using this algorithm the size distributions of silica particles on experimental AFM images have been determined.
Abstract. The photonic crystal is the material which structure is characterized by periodic distribution of refraction index in the spatial directions, which have the photonic band gaps in a spectrum of own electromagnetic states. There are numerous approaches of the creation of photonic crystals. In the present the optimal conditions of synthesis of photonic crystals based on silicon dioxide as well as the inverse photonic crystals based on vanadium dioxide are investigated. It is known that the synthesis process is influenced by many different factors. We have studied the dependence of the particle size on the concentration of reagents, as well as on the duration of the reaction. These studies are important for the production of samples of photonic crystals with a definite structure. IntroductionOne of the most important areas of modern physics is the study of periodic optical nanostructures, known as photonic crystals (PC) in which the dielectric constant varies periodically in space with period allowing Bragg diffraction of light. It is known that crystals of all types can disperse some radiation, provided that the period of the crystal lattice is of the same order as the wavelength of the radiation. Similarly, photonic crystals do not transmit the light with a wavelength comparable to the period of the photonic crystal structure, at the same time PCs are transparent to a wide range of electromagnetic radiation spectrum. These spectral bands are called "photonic band gap" (PBG) [1]. The works on photonic crystals are motivated by a number of promising applications, such as high-performance light emitting diodes, lowthreshold lasers, optical waveguides with sharp bends and optical microchips. Nowadays there are numerous approaches to the creation of PC by using the lithography [2], interferential holography [3] and self-assembly of colloidal particles [4]. One of the first materials that have been considered as photonic crystals were synthetic opals, consisting of close-packed spherical particles of silica. Self-assembly techniques are very promising, since they are quite simple in terms of hardware design and have no fundamental restrictions both on the sample size and the number of photonic crystals produced in one cycle of synthesis. However, the synthesis process is influenced by the factors like setting of the concentration ratio of the reactants, reaction temperature, sequence of blending and more. So our purpose is to investigate the effect of concentration ratio of reactant and duration of the reaction on the particle size, making possible creation of PC with predetermined characteristics. Our results are relevant for the experimental verification of the effect predicted by the authors in [5].
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