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We discuss the scattering properties of the core–shell nanowires containing metallic core with nonlocal effects and radially anisotropic shell based on the nonlocal full-wave theory. The tunable extinction spectrum could be obtained by adjusting the anisotropy parameter and geometric size of the core–shell nanowires. The main peak resulted from transverse mode would be enhanced with the optimal anisotropy parameter. The subsidiary peaks due to the longitudinal mode become dense for the coated nanowires with thin anisotropic shell. Moreover, S-shaped and Z-shaped Fano resonances in the core–shell nanowires are presented under weak dissipation. These results will have potential applications in optical communications and ultra-sensitive detections.

The paper deals with solving the problem of electromagnetic (EM) scattering on a set of small particles using the discrete dipole method and the asymptotic approach. The commonality of approaches makes it possible to study the scattering characteristics in the subterahertz range of waves on metal and dielectric nanoparticles. In both cases, an auxiliary system of linear algebraic equations (SLAE) is solved to determine the electric field vectors, which, in the case of the asymptotic approach, has a slightly smaller dimension. The limits of applying the asymptotic approach, which depends on the norm of the auxiliary SLAE matrix, have been established. Numerical calculations demonstrate the possibility of obtaining broad extinction spectra and narrow radiation patterns (RPs). [ABSTRACT FROM AUTHOR]

The aim of the study is to establish spectral-luminescent interaction effects in mixtures of colloidal Zn0.5Cd0.5S quantum dots passivated with 2-mercaptopropionic acid and Au and Au/SiO2 nanoparticles. The studied samples of Zn0.5Cd0.5S quantum dots, Au and Au/SiO2 nanoparticles and their mixtures were obtained by methods of colloidal synthesis and were characterised using transmission electron microscopy. The absorption, luminescence and time-resolved luminescence spectroscopy were used as the main investigation methods. The measurements were carried out at temperatures of 77 K and 300 K. The spectral-luminescent properties of “free” Zn0.5Cd0.5S quantum dots and those interacting with Au and Au/SiO2 nanoparticles were compared. It was found that the luminescence properties of Zn0.5Cd0.5S quantum dots can be controlled under conditions of changing plasmon-exciton coupling achieved during the formation of a dielectric SiO2 shell on the surface of Au nanoparticles as well as a result of a polymer introduced into the colloidal mixture.

We investigated the application of gold nanoshell particles as optical sensors and contrast agents to study the blood functional parameters. Gold nanoshell particles with a core size of 1 μ m that exhibit two prominent plasmonic peaks at 750 and 830 nm were developed. The peaks correspond to the wavelengths typically used to study the oxygen saturation of the blood. The plasmonic properties of gold nanoshells in media with various refractive indices were studied. Glucose samples with concentrations 0, 15, and 20%w/v in water were used. The 750 and 830 nm plasmonic peaks exhibit peak wavelength shifts of 63.77 ± 49.40 nm and 31.18 ± 20.94 nm per unit refractive index change. The optical properties of blood samples mixed with gold nanoshells were also measured. The optical absorption of blood samples increased by 7% at these wavelengths in the presence of the nanoshells. The plasmonic peaks at 750 and 830 nm showed a 3.57 ± 0.56 and 1.44 ± 0.55 percentage variation in absorbance for a 1% change in hematocrit. The enhanced optical absorption at these wavelengths suggests that these particles are effective optical sensors/contrast agents for multimodal optical and photoacoustic sensing and imaging.

This paper proposes a method for extracting the specific wavelengths of milk fat particles in a liquid absorbing medium by measuring particle size with the method of total light scattering. After considering the absorption of incident light by the liquid medium, this paper conducts simulation analysis of apparent optical parameters. At the same time, this paper simulates the extinction spectrum of common RR distributed visible light using the apparent extinction coefficient and proposes a method for extracting specific wavelengths based on the immune particle swarm optimization algorithm (IA-PSO). According to this method, the wavelength point with the smallest root mean square error between the simulated extinction value and the extinction value is selected as the measuring wavelength, which can effectively eliminate the subjective effect in the process of optimal wavelength selection. To verify the validity of the method proposed by this paper, inversion calculation of the unimodal R-R distributed spectra and the bimodal R-R distributed spectra is performed respectively in the independent mode using the PT algorithm with simulated data. In the non-independent mode, the inversion of particle size distribution is performed based on the genetic optimization algorithm. The simulation experiment results indicate that the proposed method for extracting the specific wavelengths of milk fat particles in the liquid absorbing medium can effectively improve the accuracy and stability of the inversion results and reduce measuring errors. [ABSTRACT FROM AUTHOR]

According to satellite monitoring data (MODIS/Terra), the spatial distribution of the aerosol optical depth (AOD) at a wavelength of 550 nm for the summer smog of 2007 over the North China Plain (NCP) and adjacent areas has been obtained. Areas over which the AOD is higher due to regional anthropogenic contamination sources near Beijing and Shanghai, as well as the smoke haze forming due to agricultural burning (the southwest part of the NCP), have been revealed. The similarity of optical and microphysical characteristics of aerosol in the smoke haze over the NCP and in the Russian territory has been found: (i) the decisive contribution to the optical characteristics of smoke aerosol is made by the fine mode and (ii) the attenuation spectra in the wavelength region 340–1020 nm are approximated (in logarithmic coordinates) by parabolas or fourth degree polynomials. The monitoring data at the AERONET Beijing site show that the single scattering albedo in the summer smog over the NCP is on average less (0.91) than in the smoke haze in the Russian territory (0.95–0.96). The radiative regimes of the atmosphere are significantly different: in the smog, the aerosol radiative forcing efficiency is lower approximately by 30% at the top of the atmosphere and higher by 30% at the bottom of the atmosphere than in the smoke haze. [ABSTRACT FROM AUTHOR]

The extinction characteristics of mixed particles, which are composed of various types of particles, appear to be more complex. To statistically analyze photon destinations and investigate the extinction characteristics of mixed particles by tracing all underlying events in detail, a Monte Carlo method-based extinction model has been developed. Meanwhile, an extinction spectrum measurement system was designed. A series of experiments for both single-type particle and mixed-particle systems were performed. Afterwards, global optimization algorithms are introduced to perform simultaneous inversion of sizes of mixed particles and mixing ratio based on the experimental spectrum. The inversion results show that the error for any single parameter is <2%. Performing a simultaneous inversion for particle sizes and mixing ratios leads to an increase in the relative error, but it does not exceed 9%. It indicates that the model could simultaneously invert the mixing ratio and handle particle systems with two different sizes. [Display omitted] • Establishes an extinction model based on Monte Carlo to analyze mixed particles. • Develops an experimental extinction measurement system to validate the model. • Global optimization algorithms are successfully employed during inversions. • Multi-parameter measurements of mixing ratio and particle size are measured. [ABSTRACT FROM AUTHOR]

• Nonlocal full-wave theory for metallic-core/anisotropic-shell nanowires is proposed. • Maximal extinction efficiency will appear at optimal anisotropy parameter. • The dense subsidiary peaks are observed for the thin-shell nanowires. • The reversion between S-shaped and Z-shaped Fano resonances is obtained. • The numerical results provide the guidance in the design of optical nanodevices. We discuss the scattering properties of the core–shell nanowires containing metallic core with nonlocal effects and radially anisotropic shell based on the nonlocal full-wave theory. The tunable extinction spectrum could be obtained by adjusting the anisotropy parameter and geometric size of the core–shell nanowires. The main peak resulted from transverse mode would be enhanced with the optimal anisotropy parameter. The subsidiary peaks due to the longitudinal mode become dense for the coated nanowires with thin anisotropic shell. Moreover, S-shaped and Z-shaped Fano resonances in the core–shell nanowires are presented under weak dissipation. These results will have potential applications in optical communications and ultra-sensitive detections. [ABSTRACT FROM AUTHOR]

The triangular, circular and hexagonal Au nanoplates(NPLs)were synthesized by seed-mediated growth method. The morphology and extinction spectra of the samples were characterized by SEM and UV-Vis absorption spectrometer. The SEM images show that all of the Au NPLs have regular shape and uniform size. The dipole plasmon peaks of the triangular, circular and hexagonal Au NPLs are located on 1 208,760 and 827 nm. The in-plane hexadecapole plasmon peaks gradually decrease during the shape transformation from the triangular Au NPLs to hexagonal ones.Finite-difference time-domain(FDTD)simulation was adopted to fit the extinction spectra of triangular and hexagonal Au NPLs. The simulated and experimental results of extinction spectra are similar. [ABSTRACT FROM AUTHOR]

Abstract In order to improve the applicability, spheroidal particles are substituted for the spherical particles in the traditional modeling of multi-wavelength light extinction method. The extinction coefficient and extinction spectrum are calculated at different axial ratios under the configuration of the generalized Lorenz-Mie theory. Combining extinction spectrum with regularization inversion algorithm, the influence of particle shape on particle size characterization by multi-wavelength light extinction method is discussed in detail. That is, the arithmetic statistical average and stochastic incidence statistics are employed simultaneously to calculate the extinction spectrum in the visible light range and carry out a validation for submicron particles with a refractive index of 1.33. The corresponding comparison between inversed particle sizes and those of spherical particles yields the resulting inversion deviation within 10% for mono-sized spheroids and 20% for a polydisperse particle system with an axial ratio less than 3, but then the relative deviation may increase significantly with the axial ratio, even up to 50%. It can be seen that for particles of equivalent volume, the spheroidal shape exerts a great influence on particle size characterization, and the assumption of spheroidal particle would become crucial in the cases of axial ratio above 3. [ABSTRACT FROM AUTHOR]