Ultrasonic cavitation of molten gallium: Formation of micro- and nano-spheres

Abstract

Pure gallium has a low melting point (29.8°C) and can be melted in warm water or organic liquids, thus forming two immiscible liquid phases. Irradiation of this system with ultrasonic energy causes cavitation and dispersion of the molten gallium as microscopic spheres. The resultant spheres were found to have radii range of 0.2-5 μm and they do not coalesce upon cessation of irradiation, although the ambient temperature is well above the m.p. of gallium. It was found that the spheres formed in water are covered with crystallites of GaO(OH), whereas those formed in organic liquids (hexane and n-dodecane) are smooth, lacking such crystallites. However, Raman spectroscopy revealed that the spheres formed in organic liquids are coated with a carbon film. The latter may be the factor preventing their coalescence at temperatures above the m.p. of gallium.

Ga@C-dots as an antibacterial agent for the eradication of <em>Pseudomonas aeruginosa</em>

“…[21][22][23][24] After sonication and separation of the precipitates, the fluorescence emitted from Ga@C-dots in the supernatant solution was recorded at different excitation wavelengths (330, 350, 370, 390, 410, 430, 450, 470, and 490 nm). The results that were obtained from Ga@C-dots which were produced in the presence of different amounts of Ga (70, 175, 350, and 700 mg) were identical to those in our previous reports 21 (data not shown).…”

The sonochemical synthesis of Ga@C-dots particles

“…1 inch above the molten gallium, as described previously. [29][30][31] The ultrasonic transducer (model VCX 750, frequency 20 kHz, volt 230 V AC) was obtained from Sonics and Materials Inc., USA. When the gallium was molten, ultrasonic irradiation was applied for 4 different time periods, 30 min, 60 min, 120 and 180 min, causing dispersion of the gallium and the formation of a grey suspension of particles.…”

Morphology evolution of NaTaO3 submicrometer single-crystals: from cubes to quasi-spheres

“…The above growth mechanism for spherical single crystalline nanoparticle helps us to understand and design synthetic strategies for preparing spherical single-crystalline nanoparticles. For examples, microand nano-spheres of some metals with low melting points were successfully synthesized by quenching melted precursors in solvents [30,31], and single-crystalline spheres of some semiconductors with high melting points were also prepared by the way of laser irradiation [32,33]. In these aforementioned cases, the rapid cooling process can make in extremely high supersaturation of crystal growth units and thus spherical single-crystals can be produced due to the similar formation work W hkl of each facet.…”