A A Akhmadeev

A new approach of recognition of ellipsoidal micro- and nanoparticles on AFM images and determination of their sizes

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.

Energy shift experiment in photonic crystal medium

We propose experimental confirmation of the new effect of the electron mass changes in photonic crystal medium, which was recently predicted. The method consists in measuring the Lamb shift in hydrogen atoms placed in the medium of photonic crystal. We discuss the experimental scheme based on the Lamb and Retherford experiment as well as the requirements for the samples of photonic crystals.

Coprecipitation Method of Synthesis, Characterization, and Cytotoxicity of Pr3+:LaF3 (CPr = 3, 7, 12, 20, 30%) Nanoparticles

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.

Investigations of properties of opal-like photonic crystals using combined methods

We propose a technique that combines atomic force microscopy, optical spectrophotometry and diffraction method for characterization of photonic crystals. These materials are promising for the creation of various devices, as well as for the observation of new effects due to their unique properties. Photonic crystals were synthesized by self-assembly of colloidal silica particles with low deviation in size. It is shown that the developed technique allows to increase the accuracy of determining the parameters of the photonic crystal.

Surface electric potential of linear periodic charge density

Distribution of the surface electric potential allows visualizing surface plasmons and gives information about parameters of the plasmons. Some plasmonic structures have a periodic structure, for example hybrid self-assembled photonic-plasmonic crystals. Earlier we presented a new method of calculation of the potential for quasiperiodic and periodic structures. In this paper we compare the method with other methods that have different algorithms and formulas.

Periodic potential distribution in linear photonic-plasmonic crystals

Photonic-plasmonic crystals are modern materials for nanotechnology and photonics. They have periodic structure and correspondingly periodic potential distribution. We propose a new method of calculation of potential for periodic structures.

Methods of characterization of synthetic opal films

We developed methods for determination of thickness, number of layers and filling fraction of silica particles for synthetic opals. We show that the filling fraction is considerably less than for ideal close-packed structure, which is important for practical and theoretical applications.

Synthesis optimization of photonic crystals based on silicon and vanadium dioxides

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.