In this work, we have, for the first time, experimentally verified the hypothesis of reducing the agglomeration rate of aerosol nanoparticles produced by spark discharge upon decreasing the carrier gas temperature in the range of 24 °C to –183 °C. The synthesis of nanoparticles was implemented as a result of spark ablation of electrodes manufactured from Au with a purity of 99.998% installed in a specially designed gas chamber dipped into liquid nitrogen (−196 °C) to cool down the carrier gas supplied through one of hollow electrodes. It follows from the analysis of transmission electron microscopy images that both the average size of primary nanoparticles and the degree of their sintering become lower if the gas is cooled. For example, in the case of using nitrogen as a carrier gas, the average size of primary nanoparticles decreases from 9.4 nm to 6.6 nm as the gas temperature decreases from 24 °C to –183 °C. This also causes the aggregates to become more branched, manifested by the reduction in their solidity from 92% to 76%. The agglomeration model of Feng based on Smoluchowski theory was employed to calculate particle size distributions that were found to be consistent with the experimental data. The gold nanoparticles synthesized at room and cryogenic temperatures of the carrier gas (N₂, Ar + H₂, He) were used to pattern plasmonic nanostructures on ceramic alumina substrates by using aerosol jet printing technology for the purpose of demonstrating the possibility of their application in surface-enhanced Raman spectroscopy (SERS). The SERS enhancement factor was estimated at 2 × 10⁶ from the analysis of SERS and normal Raman spectra of 1,2-bis(4-pyridyl)ethylene used as an analyte.

This article presents the development of a multielectrode spark discharge generator designed to produce multicomponent nanoparticles with precise control over the elemental ratios. This capability is achieved through the creation of two independent spark discharges positioned extremely close to one another, facilitating improved mixing of materials. Both theoretical and experimental studies demonstrate that this new generator exhibits similarities with its predecessor, which simplifies the integration process. The EDX analysis clearly demonstrated the capability to systematically control the atomic fraction of aluminum in combinations of tungsten, copper, and aluminum. This proportion varied from 22% to 2% in nanoparticles, which had an average mobility diameter of 27 nm. These nanoparticles were composed of atomic clusters of the respective materials with an average size of 2 nm. Also, using two independent discharges the elemental composition of two-component nanoparticles can be precisely adjusted over the entire range by using two electrodes made of the same material. Additionally, HR-TEM coupled with SAED analysis revealed a high degree of amorphousness in the nanoparticles, indicating effective mixing of the components. These findings pave the way for the development of multicomponent nanoparticles with tailored properties, holding significant potential for a wide array of scientific and technological applications.

Aerosol particle charging is widely used in various technical applications. A model of a needle-plate type charger for efficient charging of aerosol nanoparticles in a corona plasma discharge has been developed and investigated. The main difference from analogues is the modernization of the geometry of the hole in the grounded plate and the number of corona needles. This led to a significant increase in the efficiency of the charger by more than 25%. The effect of two types of discharge plates with cylindrical and conical inner holes on the external charging efficiency of aerosol particles is experimentally investigated. Metallic nanoparticles of Ag with sizes of 20–160 nm and number concentration of 10⁶–10⁸ cm⁻³ were used as a test aerosol. It is found that the maximum efficiency of particle charging is achieved by using a plate with a conical hole by reducing electrostatic losses from 37±3% to 20±2%. This is due to the redistribution of the electrostatic field strength lines when changing the cylindrical hole to a conical one. An additional effect of increasing the efficiency of particle charging was also achieved through the use of a multi-pointed needle, which provided lower electrostatic losses compared to a single needle at the same corona discharge current of 20 µA. It has been experimentally shown that the use of a conical hole of the plate and a multi-pointed needle increased the charging efficiency of particles from 47±3% to 59±4% in comparison with the standard design with a cylindrical hole and a single-pointed needle.

A new approach of electrostatically focusing nanoparticles through an electrical tape mask to form narrow <10 μm and conductive microstructures is developed and investigated in this work. The presented approach is similar to deposition of material through a stencil and allows one to obtain lines 15 times smaller than the width of the gap in the mask. It is proposed to use ordinary PVC electrical tape as a mask instead of expensive photo or electronic resists. The work investigated the influence of a mask thickness (height) of 60–180 μm, a gap width of 120–380 μm, a substrate potential of 0.1–5 kV, and a deposition time of 10 and 120 min on the geometry and electrical properties of the lines. The substrate material was Si, and charged Au nanoparticles 60 nm in size synthesized by spark discharge were the building blocks of microstructures. Numerical modeling of the process of focusing nanoparticles in COMSOL qualitatively confirmed the found experimental dependencies. The electrical resistivity of the sintered lines is 6.34 times higher than that of bulk gold. The developed approach makes it possible to obtain high-aspect microstructures, supports operation at atmospheric pressure, and is flexibly controlled in terms of the choice of materials.