Effects of Temperature on the Morphology and Optical Properties of Spark Discharge Germanium Nanoparticles

Abstract

We report the spark discharge synthesis of aerosol germanium nanoparticles followed by sintering in a tube furnace at different temperatures varying from 25 to 800 °C. The size, structure, chemical composition and optical properties were studied. We have demonstrated a melting mechanism of nanoparticles agglomerates, the growth of the mean primary particle size from 7 to 51 nm and the reduction of the size of agglomerates with a temperature increase. According to transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) data, primary nanoparticles sintered at temperatures from 25 to 475 °C basically have a structure of Ge crystals embedded in a GeOx amorphous matrix, as well as visible photoluminescence (PL) with the maximum at 550 nm. Pure germanium nanoparticles are prepared at temperatures above 625 °C and distinguished by their absence of visible PL. The shape of the experimental UV-vis-NIR extinction spectra significantly depends on the size distribution of the germanium crystals. This fact was confirmed by simulations according to Mie theory for obtained ensembles of germanium nanoparticles.

Spark Discharge Synthesis and Characterization of Ge/Sn Janus Nanoparticles

“…The morphology of generated agglomerates with subsequent sintering at 325 °C was similar to the initial agglomerates (see Supplementary Figure S1 ), but the average size of the primary nanoparticles increased to 11.3 ± 2.7 nm, which was connected to the partial melting of tiny nanoparticles in the furnace and the beginning of the morphology change process [ 59 , 60 ].…”

“…They were reshaped in liquid form into a well-rounded drop and then further recrystallized into compact spherical crystal nanoparticles. The temperature of the complete reshaping of the agglomerates into spherical particles is a function of the primary particle diameter in the agglomerates and the thermal properties of the material of electrodes, and it is lower than the melting point of the appropriate bulk material, which has been demonstrated earlier in experiments with silver and germanium nanoparticles [ 59 , 66 ]. The TEM images represented in Figure 2 show a morphology change from fractal-like agglomerates to large individual particles with a wide range of diameters varying from 9 to 89 nm for a gap voltage of 1.5 kV and from 12 to 82 nm for 3 kV.…”

“…The temperature of the Sn surface segregation depends on the thickness of the Ge/Sn layer and decreases with increasing Sn content, so the segregation process can partly start at temperatures as low as 275 °C [ 56 ]. At 750 °C, the morphology of Ge/Sn nanoparticles is suggested, converting from agglomerates into individual nanoparticles as the bare germanium agglomerates synthesized in the spark discharge are reshaped into individual nanoparticles at close values of temperature [ 59 ].…”

Impact of Growth Temperature of Lead-Oxide Nanostructures on the Attenuation of Gamma Radiation

“…In addition, the growth rate of NSs can vary significantly with growth temperature. At higher growth temperatures, the growth rate could be increased, leading to more complex NSs; this is because the mobility of atoms and molecules on the surface of the NS can be influenced by the temperature which in turn can affect the shape of the structure and would be a more compact structure …”

Aerosol Dry Printing for SERS and Photoluminescence-Active Gold Nanostructures Preparation for Detection of Traces in Dye Mixtures

“…Aerosol metal nanoparticles produced in a gas discharge generator [ 35 , 36 ] can be used as a source for the formation of nanostructures. The implication of additional in-flow thermal [ 37 ] or the laser treatment [ 38 ] of aerosol nanoparticles leads to varied morphology, as well as optical properties, of nanoparticles which is extremely important for the fabrication of sensitive SERS and luminescence substrates to be applied. Beyond that, after SERS and MEF investigations, the nanostructures based on bare aerosol nanoparticles without any surfactants on their surfaces can be removed from a sample by a pure gas jet (without nanoparticles) passed through the nozzle for aerosol printing without damaging the painted layer.…”