A cost-effective, scalable and versatile method of preparing nano-ink without hazardous chemical precursors is a prerequisite for widespread adoption of printed electronics. Precursor-free synthesis by spark discharge is promising for this purpose. The synthesis of platinum nanoparticles (PtNPs) using a spark discharge under Ar, N2, and air has been investigated to prepare highly conductive nano-ink. The size, chemical composition, and mass production rate of PtNPs significantly depended on the carrier gas. Pure metallic PtNPs with sizes of 5.5 ± 1.8 and 7.1 ± 2.4 nm were formed under Ar and N2, respectively. PtNPs with sizes of 18.2 ± 9.0 nm produced using air consisted of amorphous oxide PtO and metallic Pt. The mass production rates of PtNPs were 53 ± 6, 366 ± 59, and 490 ± 36 mg/h using a spark discharge under Ar, N2, and air, respectively. It was found that the energy dissipated in the spark gap is not a significant parameter that determines the mass production rate. Stable Pt nano-ink (25 wt.%) was prepared only on the basis of PtNPs synthesized under air. Narrow (about 30 μm) and conductive Pt lines were formed by the aerosol jet printing with prepared nano-ink. The resistivity of the Pt lines sintered at 750 °C was (1.2 ± 0.1)·10−7 Ω·m, which is about 1.1 times higher than that of bulk Pt.

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.

Sintering of oxidized copper nanoparticles arrays in the form of lines by the local treatment of laser radiation with wavelengths of 527 nm and 980 nm was studied. To form lines with a width equal to 40–150 μm and a thickness equal to 0.5–4 μm focused aerosol jets with average nanoparticle sizes of 110 and 65 nm were used. The production of semiconductor arrays from oxidized copper nanoparticles with a specific electrical resistance of 2⋅10−3 Ω⋅m using laser radiation with a wavelength of 980 nm was demonstrated.