Dielectric Constant Of Core Research Articles

Tunable properties of localized surface plasmon resonance wavelength of gold nanoshell

The effects of shell thickness, inner core size, and dielectric constants of core and embedding medium on the localized surface plasmon resonance wavelength of gold nanoshell are investigated by Mie theory. The results show that the extinction peak of gold nanoshell is first blue-shifted and then red-shifted with the increase of shell thickness, that the shift shell thickness corresponding to quadrupolar wavelength is greater than that corresponding to dipolar wavelength, and that the ratio of the shift shell thickness to the inner core size decreases with the increase of inner core size, and increases with the increase of dielectric constant of inner core or embedding medium. The resonance peaks in the scattering spectra have similar phenomena to those in extinction spectra as the shell thickness increases. The shift of the spectral peak is ascribed to the plasmon hybridization and phase retardation effect.

Localized surface plasmon resonance propertiesof elliptical gold nanotubes

The effects of ellipse shape, polarization direction of incident light, shell thickness, and dielectric constants of core and embedding medium on the localized surface plasmon resonance (LSPR) of elliptical gold nanotube have been investigated by the Finite Difference Time Domain (FDTD) method. When the semimajor axis is fixed, it is found that with the increase of the semiminor axis of the ellipse the extinction peak of the gold nanotube has a red-shift. With the increase of the angle between the incident polarization and the semimajor axis, the extinction peak has a red-shift. With the shell thickness decreasing, the extinction peak of gold nanotube also has a red-shift. Furthermore, we also find that the increase of the dielectric constant for core or embedding medium will induce a red-shift of LSPR in gold nanotube. The change of the extinction peak is ascribed to the plasmon hybridization and the competition between the variations of conduction and oscillation electrons.

Modeling of light absorption and scattering by metal nanoparticles coated with organic dye J-aggregate

The results of the theoretical study of optical properties of composite nanoparticles consisting of a metal core (Ag, Au, Cu, Al, Ni, Cr) and a J-aggregate shell of organic dye are presented. Light extinction, absorption, and scattering coefficients in colloidal solutions were calculated within the model based on the Mie theory modified taking into account dimensional phenomena and complemented by calculations of complex dielectric functions of the metal core and J-aggregate shell. The model adequately explains the features observed in light absorption and scattering spectra by hybrid nanoparticles, associated with the plasmon resonance in the metal core and with electronic excitation of the J-aggregate. The strong dependence of the results on geometrical parameters of nanoparticles and dielectric constants of core and shell materials was demonstrated. Methods for controlling the effects of the plasmon-exciton interaction in the system and optical properties of composite materials developed based on nanoparticles under study are discussed.

Microwave‐assisted encapsulation of citric acid using hydrocolloids

SummaryThis study elucidates the capability of a novel technique for producing microcapsules at an enormously short time and low cost. This technique is based on the difference between dielectric constants of core and coat materials. Edible citric acid was mixed with various biomacromolecules at ratios of 1:5, 1:10, and 1:100. Each mixture was treated up to 600 s at various powers (120–1200 W) in a microwave oven. Subsequently, the microcapsules were separated by distinct sieves, and their apparent structure and quality were evaluated using binoculars, and photographs were taken for visual comparisons. Our observations showed that only five hydrocolloids were able to produce high‐quality and efficient encapsulation [casein > inulin > carboxymethylcellulose (CMC) > low methoxyl (LM) pectin (9/5%) > sorbitol]. Moreover, the highest coating efficiency was seen at highest intensity (1200 W) at a mixing ratio of 1:10. Furthermore, the optimum treating time periods for those five efficient coating materials were about 400, 75, 400, 100, and 100 s.