Sуnthesis and Study of the Properties of New Hybrid Photochromic Chromenes with Reversible Modulation of Fluorescence

Russian Journal of General Chemistry - The reaction between phenalenon derivatives containing hydroxy group in peri-position to carbonyl and propynol was studied. A new hybrid compound was...     

Dispersion relations of vector and scalar bosons in material media

Bulletin of the Lebedev Physics Institute - The dispersion relations of vector, scalar, and pseudo-scalar bosons of a dielectric medium are determined taking into account their resonant interaction...     

Raman Scattering of Carbon Nanotubes Implanted with Nitrogen

Crystallography Reports - The Raman spectra of multiwall (bamboo-type) carbon nanotubes implanted with nitrogen have been investigated under excitation by different lasers with wavelengths...     

Raman Scattering in Langasite-Family Crystals

Crystallography Reports - Raman scattering spectra have been investigated in La3Ga5SiO14 langasite crystals with Cr and Fe impurities and La3Ga5.25Ta0.25Si0.5O14 crystalline solid solution. It is...     

Overtone Raman Scattering in Lithium Tantalate Single Crystals

Optics and Spectroscopy - Overtone bands in the spectral range of 1300−1920 cm–1 have been found in Raman scattering spectrum of lithium tantalate single crystals. The Raman spectra...     

Brodie's or Hummers’ Method: Oxidation Conditions Determine the Structure of Graphene Oxide

Synthesis and studies of graphite oxide started more than 150 years ago and turned into a boom by the measurements of the outstanding physical properties of graphene. A series of preparation protocols emanated trying to optimize the synthesis of graphene oxide in order to obtain a less defective material, as source for graphene. However, over-oxidation of the carbon framework hampered establishing structure-property relationships. Here, the fact that two different synthetic methods for graphene oxide preparation lead to very similar types of graphene oxide with a preserved graphene lattice is demonstrated. Either sodium chlorate in nitric acid (similar to Brodie's method) or potassium permanganate in sulfuric acid (similar to Hummers’ method) treatment are possible; however, reaction conditions must be controlled. With a preserved carbon lattice analytical differences between the samples relate to the altered on-plane functionality. Consequently, terming preparation protocols “according to Brodie's/Hummers’ method” is not sufficient.     

Probe Raman spectroscopy of sodium uranyl-acetate microcrystals

The technique for recording Raman spectra in uranium compounds using a probe minispectrometer with a multielement radiation detector has been developed. A selective filter, which reflects exciting laser radiation and transmits Raman signals, has been used to suppress the exciting radiation. It is shown that the technique developed makes it possible to record Raman spectra from a small amount (~10^–5 g) of sodium uranyl-acetate polycrystals in a wide spectral range for several seconds.     

Spectroscopy of stop bands in artificial opals filled with an alcohol solution of potassium iodide

The spectral position of the stop bands in photonic crystals based on artificial opals filled with an alcohol solution of potassium iodide is investigated. The energy-band structure of samples with quartz globules 230 nm in diameter is modeled based on the dispersion equation. The spectral position of the stop bands in the [111] direction at different solution concentrations is determined. The conditions for forbidden-band ??collapse?? are established. The possibility of applying artificial opals in optical cavities of lasers of different types is analyzed.     

Generation of terahertz radiation in cubic non-centrosymmetric crystals

The conditions of parametric radiation generation on polaritons in cubic noncentrosymmetric crystals are studied. The possibility of such generation is theoretically justified. The polariton radiation frequencies are calculated for GaP, ZnSe, ZnTe, and GaAs crystals. The obtained generation frequencies are compared to the experimental results on Raman scattering on polaritons. The block diagram of the terahertz radiation generator operation using a GaP crystal and a pulsed laser with high peak power at low energy of laser pump pulses is presented. The lasing frequency shift is analyzed depending on the scattering geometry. The coefficient of exciting radiation conversion to the terahertz range is determined.     

Temperature dependence of the parameters of stop bands of globular photonic crystals

The results of the experimental study of the characteristics of stop bands of globular photonic crystals are presented depending of the globule diameter, temperature, and the presence of a dielectric medium in pores between globules. The reflectance spectra of the (111) surface of a globular photonic crystal are analyzed using a fiber-optic technique. As the sample temperature is lowered, the reflectance maximum shifts to the long-wavelength spectral region. The spectral characteristics of stop bands are compared with calculations based on the Wolf-Bragg formula.