In this paper, we propose a facile approach to the management of graphene oxide (GO) chemistry via its synthesis using KMnO₄/K₂Cr₂O₇ oxidizing agents at different ratios. Using Fourier Transformed Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, and X-ray Absorption Spectroscopy, we show that the number of basal-plane and edge-located oxygenic groups can be controllably tuned by altering the KMnO₄/K₂Cr₂O₇ ratio. The linear two-fold reduction in the number of the hydroxyls and epoxides with the simultaneous three-fold rise in the content of carbonyls and carboxyls is indicated upon the transition from KMnO₄ to K₂Cr₂O₇ as a predominant oxidizing agent. The effect of the oxidation mixture’s composition on the structure of the synthesized GOs is also comprehensively studied by means of X-ray diffraction, Raman spectroscopy, transmission electron microscopy, atomic-force microscopy, optical microscopy, and the laser diffraction method. The nanoscale corrugation of the GO platelets with the increase of the K₂Cr₂O₇ content is signified, whereas the 10–100 μm lateral size, lamellar, and defect-free structure is demonstrated for all of the synthesized GOs regardless of the KMnO₄/K₂Cr₂O₇ ratio. The proposed method for the synthesis of GO with the desired chemistry opens up new horizons for the development of graphene-based materials with tunable functional properties.

Indium-antimonide quantum dots are for the first time formed on the surface of an epitaxial In0.25GaAsSb layer isoperiodic to a GaSb(001) substrate by liquid-phase epitaxy in the range of...

The optical properties of metal nanoparticles are significantly influenced by their morphology, and varying of their shape leads to the appearance of a number of interesting properties. The presence of sharp edges and vertices in nanoparticles with non-spherical shapes, such as polyhedral, pentagonal and, in particular, icosahedral, leads to enhanced electric-field confinement. Enhanced optical and electrical properties of nanoparticles and semiconductor films with embedded nanoparticles make them promising for various applications, including photovoltaics, optoelectronics, and light-emitting devices. Since the properties of nanoparticle-based nanocomposites are determined not only by the morphology of nanoparticles, but also by their distribution in the film volume, it is necessary to develop methods for producing nanoparticles with the possibility of controlling and varying their morphology, as well as their introduction into semiconductor films to obtain uniform arrays. This article gives a review of relevant studies, the main focus is on chemical synthesis, as one of the most common methods for producing metal nanoparticles.

Polarization of femtosecond laser radiation influence on the windings of ellipsoidal silver nanoparticles and their orientation in zinc oxide sol-gel films was studied, which caused the appearance of dichroism in the films of the irradiation field. Unlike silver-containing glasses, where this mechanism was discovered, it has hardly been studied in thin sol-gel films before. Femtosecond laser pulses with a high degree of repetition and linear polarization controlled the shape, size and orientation of silver nanoparticles which was oriented horizontally along and across the direction. For dichroism to occur, it is necessary to ensure high-quality separation of laser transducers by Ag nanoparticles and the absence of differences in the zinc oxide matrix. Dichroism in such ZnO:Ag films was investigated by optical microscopy and spectrophotometry away from light. Analysis of the size, content, shape and location of nanoparticles in the film was conducted taking into account electron microscopy. It has been shown that the relationship between dichroism as a result of exposure of the film to laser radiation with energy density ranging from 43 to 99 mJ/cm2 per pulse and flow velocity of 1 mm/s. It was investigated that at given fluence, the interruption of ellipsoidal nanoparticles, most of which are simply oriented along the polarization line of the femtosecond transformation, occurs depending on the direction of the transformation. As a result of laser treatment, modified areas of the film acquired dichroism. When the polarization axis of the incident light was parallel to the direction of linear polarization of the femtosecond radiation with which the regions were recorded, the plasmon resonance peak shifted to the long-wavelength deflection region. When the changed zones were rotated by 90°, the peak of the plasmon resonance shifted to a shorter wavelength region relative to. At fluence above 99 mJ/cm2, dichroism remained, but it decreased sharply, the size of nanoparticles decreased and began to gradually destroy the film matrix with the formation of nanoscale pores and cracks. Obtained results can be used to register polarization-sensitive elements of small sizes, the spectral transmission of which will depend on the orientation of the linear polarization vector of the light incident on them. The proposed method allows adjustment of plasmon resonance peak position in the spectral range from 450 to 650 nm, which can also be used to increase the sensitivity of photodetectors in the specified spectral range.

GaAs photovoltaic converters containing quantum well-dot (QWD) heterostructures are studied. The QWD properties are intermediate between those of quantum wells (QWs) and quantum dots. The...

The paper presents the results of the microstructure and morphology study of two-dimensional Ge QD arrays in a Si/Al2O3 matrix formed by annealing multilayer periodic structures with Ge nanolayers in a Si/Al2O3 matrix. The distinctive features of samples in the series are the location and thickness of the Si barrier layers between Ge and aluminium oxide matrix. X-ray reflectometry and diffractometry and transmission electron microscopy studies have shown that large Al₆Ge₅ crystallites are formed and the multilayer structure is destroyed after annealing of the multilayer sample Al₂O₃/Ge without Si. It was found that the presence of Si barrier layers in multilayer Al₂O₃/Si/Ge structures reduces the interdiffusion of Al and Ge, but Ge_1-xSi_x nanocrystallites are formed as a result of Si and Ge interdiffusion. Thus, the introduction of Si barrier layer into the Al₂O₃/Ge structure allowed obtaining of two-dimensional arrays of Ge_1-xSi_x nanocrystallites with the penetration of Si up to 0.64.