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We have developed an aerosol-based technique for deposition of monodisperse ensembles of spherical SiO2 nanoparticles on the surface of single-crystal silicon substrate (1 cm2) with an average surface particle density of about 2.1±0.4 particles per μm2. The obtained samples of monodisperse ensembles SiO2 nanoparticles was characterized by scanning and transmission electron microscopy. The ensemble of deposited nanoparticles is characterized by a narrow size distribution with a modal size of 26.6 nm and a full width at half maximum of 3.5 nm according to the atomic force microscopy data. We have demonstrated the use of the obtained test structure to determine the effective radius of the tip of an atomic force microscope.

The morphology, crystal structure and size of aerosol nanoparticles generated by erosion of electrodes made of different materials (titanium, copper and aluminum) in a multi-spark discharge generator were investigated. The aerosol nanoparticle synthesis was carried out in air atmosphere at a capacitor stored energy of 6 J, a repetition rate of discharge of 0.5 Hz and a gas flow velocity of 5.4 m/s. The aerosol nanoparticles were generated in the form of oxides and had various morphologies: agglomerates of primary particles of TiO2 and Al2O3 or aggregates of primary particles of Cu2O. The average size of the primary nanoparticles ranged between 6.3 and 7.4 nm for the three substances studied. The average size of the agglomerates and aggregates varied in a wide interval from 24.6 nm for Cu2O to 46.1 nm for Al2O3.

Graphical abstract, A method for measurement of dimensions of platy particles of exfoliating, or delaminating, materials, such as clays, in aqueous suspensions in situ is proposed. Equivalent spherical diameter (esd), measured by many common methods, depends more on the major (lateral) dimension of a particle, while it is less sensitive to changes of the particle thickness. Addition of the second method, results of which are a function of the particle diameter and thickness too, would provide more accurate determination of the particle dimensions. Previously, a combination of low-temperature nitrogen adsorption (BET) and dynamic light scattering (DLS) methods for determination of specific surface area of dry powder of platy particles and their esd in suspension was suggested. While such combination was suitable for measurement of particle size for non-exfoliating materials, it gave incorrect results for exfoliating materials, which dramatically change their surface area when dispersed in liquid. We modify this method by substituting BET method with NMR relaxometry, which allows to measure wetted surface area of the dispersed material directly in suspension. The advantages of this method are:•More accurate determination of diameter and thickness of platy, particularly exfoliating, materials directly in suspension.•Possibility of routine monitoring of particle size changes during the dispersing process.

The method of acoustic spectroscopy is used for the first time for investigating the spectra of ultrasonic attenuation in the range of 3–100 MHz on oriented carbon nanotubes in the stabilized aqueous dispersion. The anisotropy of attenuation of ultrasound manifests itself in a significant distinction between the attenuation spectra for preferential perpendicular and parallel orientation of carbon nanotubes with respect to the wave-propagation direction. A qualitative agreement of the measured-spectra shape with that of the attenuation spectra calculated from the theoretical model is obtained.

Ultrasound attenuates when propagating through aqueous dispersions of carbon nanotubes. We established a significant difference in the ultrasound attenuation frequency spectra for the nanotubes oriented either along or across the ultrasound beam. This effect can be used for calculating geometrical and rheological properties of nanofiber materials dispersed in liquids. Keywords: Ultrasound attenuation, Carbon nanotubes, Nanofibers