Coherent acoustic vibration of metal nanoshells

Using time-resolved pump-probe spectroscopy we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger and the period is longer than in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.Comment: 5 pages, 3 figure

GEO-ECOLOGICAL STUDY OF CENTRAL PIPELINE CORRIDORS IN GEORGIA

At present, the main pipelines represent the most profitable economic means in terms of transportation, supply and exploitation of energy resources. Since their laying is associated with a change in the natural environment, the ecological study of these corridors is a prerequisite. Geo-ecological study of the main pipelines is divided into three stages. This is the study of the pipeline route, to establish the existing background before the work begins. The second stage is the establishment of environmental impact during the laying of the pipeline. The third step is to monitor the environmental problems encountered during exploitation.The presented article gives a geo-ecological study of the corridors of gas pipelines in the section 1200, 1000 and 700 mm on the Kazbegi-Red Bridge (North-South) section. Carried out works represents the first stage of the study, and we have identified the physical and biological characteristics of the pipeline corridors. It was determined the purity of air, noise, chemical composition of soil, water and vegetation cover, as well as engineering and geological conditions of gas pipeline corridors. The results obtained do not exceed the values of the maximum permissible concentrations adopted in Georgia and in European countries, although Pl, Co, Ni and Cd show increased values directly near the gas pipeline.At present, the main pipelines represent the most profitable economic means in terms of transportation, supply and exploitation of energy resources. Since their laying is associated with a change in the natural environment, the ecological study of these corridors is a prerequisite. Geo-ecological study of the main pipelines is divided into three stages. This is the study of the pipeline route, to establish the existing background before the work begins. The second stage is the establishment of environmental impact during the laying of the pipeline. The third step is to monitor the environmental problems encountered during exploitation.The presented article gives a geo-ecological study of the corridors of gas pipelines in the section 1200, 1000 and 700 mm on the Kazbegi-Red Bridge (North-South) section. Carried out works represents the first stage of the study, and we have identified the physical and biological characteristics of the pipeline corridors. It was determined the purity of air, noise, chemical composition of soil, water and vegetation cover, as well as engineering and geological conditions of gas pipeline corridors. The results obtained do not exceed the values of the maximum permissible concentrations adopted in Georgia and in European countries, although Pl, Co, Ni and Cd show increased values directly near the gas pipeline

Surface plasmon lifetime in metal nanoshells

The lifetime of localized surface plasmon plays an important role in many aspects of plasmonics and its applications. In small metal nanostructures, the dominant mechanism restricting plasmon lifetime is size-dependent Landau damping. We performed quantum-mechanical calculations of Landau damping for the bright surface plasmon mode in a metal nanoshell. In contrast to the conventional model based on the electron surface scattering, we found that the damping rate decreases as the nanoshell thickness is reduced. The origin of this behavior is traced to the spatial distribution of plasmon local field inside the metal shell. We also found that, due to interference of electron scattering amplitudes from nanoshell's two metal surfaces, the damping rate exhibits pronounced quantum beats with changing shell thickness.Comment: 9 pages, 4 Figure

Essential L-Amino Acid-Functionalized Graphene Oxide for Liquid Crystalline Phase Formation

The colloidal 2D materials based on graphene and its modifications are of great interest when it comes to forming LC phases. These LC phases allow controlling the orientational order of colloidal particles, paving the way for the efficient processing of modified graphene with anisotropic properties. Here, we present the peculiarities of AA functionalization of GO, along with the formation of its LC phase and orientational behavior in an external magnetic field. We discuss the influence of pH on the GOLC, ultimately showing its pH-dependent behavior for GO-AA complexes. In addition, we observe different GO morphology changes due to the presence of AA functional groups, namely L-cysteine dimerization on the GO platform. The pH dependency of AA-functionalized LC phase of GO is examined for the first time. We believe that our studies will open new possibilities for applications in bionanotechnologies due to self-assembling properties of LCs and magnificent properties of GO.Comment: 10 pages, 16 figure

Linear and nonlinear optical absorption coefficients in GaAs/Ga1−xAlxAs concentric double quantum rings : Effects of hydrostatic pressure and aluminum concentration

ABSTRACT: The linear and nonlinear intra-band optical absorption coefficients in GaAs/Ga1−xAlxAs two-dimensional concentric double quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and aluminum concentration the energies of the ground and the first excited state have been found using the effective mass approximation and the transfer matrix formalism. The energies of these states and the corresponding threshold energy of the intra-band optical transitions are examined as a function of hydrostatic pressure and aluminum concentration for different sizes of the structure. We also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as functions of the incident photon energy for different values of hydrostatic pressure, aluminum concentration, sizes of the structure, and incident optical intensity. Its is found that the effects of the hydrostatic pressure and the aluminum concentration lead to a shifting of the resonant peaks of the intra-band optical spectrum