Different methods have been proposed for the incorporation of a dye, vanadyl tetra-5,14,23,32-phenyl-2,3-naphthalocyanine, into the shells of polyelectrolyte capsules. Capsule preparation conditions have been selected to provide efficient incorporation of the dye and stability of capsules to aggregation. A suspension of the capsules has been irradiated with lasers operating at wavelengths belonging to the near-infrared spectral region. It has been found that the capsules can be disrupted under the irradiation. Continuous and pulsed laser radiations have been shown to have different effects on the capsules.
Polyelectrolyte capsules containing rhodamine 6G and fluorescein isothiocyanate in their shells are obtained by successive adsorption on spherical microscopic CaCO 3 particles followed by the dissolution of the latter. Suspensions of the capsules are irradiated with a laser operating at a wavelength corresponding to the absorption bands of the dyes, and it is shown that shell modification with the selected dyes promotes photosensitized disruption of these structures. The mechanism proposed for this disruption is realized via energy transfer from photoexcited dye molecules to the polymer matrix. Therewith, the dye-modified capsules are disrupted due to their nonuniform local heating.
Reduced graphene oxide (RGO) particles were obtained from natural and artificial graphite using chemical reduction. The particles were placed on an aqueous subphase surface in a Langmuir trough from suspensions in carbon tetrachloride. Compression isotherms of layers of RGO particles were obtained for different amounts of the substance deposited on the subphase. Layers on the aqueous subphase surface were studied using a Brewster microscope and measurements of the surface potential. Comparison of the obtained data made it possible to determine the stage of the formation of a continuous RGO layer.
Polyelectrolyte capsules with molecules of fluorescein isotiocyanate included in the shell have been obtained. The inclusion of dye molecules in the shell of the capsule allows the photosensibilized destruction of its structure. The measurements of the fluorescence intensity of a dye that was present in the shell revealed effective dissipation of the energy of photoexcited molecules by the surrounding organic matrix. The capsule suspension was irradiated by a laser in the absorption band of fluorescein isotiocyanate molecules. By measuring the size distribution of the capsules before and after irradiation with a laser it was shown that the capsules are destroyed under the effect of laser radiation.
Polyelectrolyte capsules with Rhodamine 6G molecules included into the shell are obtained in this work. The inclusion of dye molecules into the shell can provide the destruction of capsules by photosensitization. Measurements of the dye fluorescence intensity in the shell show that the energy of photoexcited molecules is effectively dissipated by the surrounding organic matrix. The capsule suspension is laser irradiated in the absorption band of Rhodamine 6G molecules. Measurements of the size distribution of capsules before and after laser irradiation reveal that the capsules are destroyed by laser illumination.
Polyelectrolyte capsules were modified by different types of fluorescent dyes and their optical properties were investigated. Three methods of encapsulation were used: dye adsorption onto the porous core, change of the solvent and embedding into the polyelectrolyte shell. Suspension of capsules with Rhodamine 6G molecules in the shell was irradiated by laser beam with wavelength corresponded with the absorption band for the dye molecule. Measurements of the capsules size distribution before and after laser irradiation showed that the capsules were destroyed by laser radiation.
The examples of phase transitions in Langmuir-Blodgett films of polyvinylidene fluoride (PVDF) and in the surface layer of polystyrene were chosen to demonstrate the great potential of using luminescent molecular probes for studying the heterogeneity of the surfaces of solids and thin films, as well as structural transformations and phase transitions in systems of different natures. The method provides unique information on the local properties of surfaces and thin films when used in combination with other techniques.
Polyelectrolyte capsules with silver and gold nanoparticles in the shell composition have been obtained using calcium carbonate and polystyrene microparticles as cores. Capsules were modified with silver nanoparticles using silver mirror reaction. Gold nanoparticles were embedded in capsule shells via their adsorption from previously obtained sol. A significant difference in the structure of capsules obtained on cores of different types has been shown by atomic-force and transmission electron microscopy.
A hierarchy of formed Ge surface relief nanostructures, including a disordered nanocluster structure, a two-dimensional lattice, and a one-dimensional lattice, is observed as the laser irradiation dose is increased. It is described in the framework of the defect deformation mechanism.
A defect-deformational (DD) mechanism is proposed for the self-organization of laser-induced point defects (vacancies and interstitials) under low-threshold (far from the melting point) local (10–100 μm) light-induced heating with the scanning periodic pulsed laser irradiation of a semiconductor resulting in an inelastic deformation of micron-sized regions of Ge. A linear theory of DD instability is developed within the model of a biaxially stressed defective film. This model describes the main experimental data on the formation of two-and one-dimensional periodic nanostructures on a semiconductor surface relief.
Atomic-force microscopy and analysis of both photothermal (quasi-static) strains of surfaces and the kinetics of intensity of specularly reflected light were used to study special features of defect production in GaAs in relation to the number N of focused laser pulses incident on the surface. Irradiation of the semiconductor was accompanied by its electronic excitation, local heating, and deformation of surface layers. It is shown for the first time that the genesis of surface defects and damage in semiconductors (within the laser spot with a micrometer diameter) has a multistage character in the vicinity of the plasticity threshold. The defect-induced and plastic nanometer-scale surface displacements ΔU z increase with increasing N only if the shearing surface strains ϕ exceed the previously determined values 10−5<ϕ0<10−4 for deformation-related elasticity (quasi-elasticity) limits in GaAs. The origination of nanoscale defects and their self-organization at the early stages of photostrains in the semiconductor is discussed. The possible relation between the defects observed and the subsequent catastrophic damage to micrometer-sized regions of GaAs at large values of N is considered.