Synthesis of Cerium Dioxide Nanoparticles by Gas/Liquid Pulsed Discharge Plasma in a Slug Flow Reactor

Abstract

Cerium dioxide (CeO 2 ) nanoparticles have gained immense attention owing to their use in various applications. Current synthesis methods for CeO 2 nanoparticles including hydrothermal and chemical precipitation are time-consuming and require chemical reagents. In order to shorten the reaction time and avoid the use of organic reagents, a new method for CeO 2 nanoparticles synthesis in a slug flow system by atmospheric-pressure pulsed discharge plasma was proposed, which provided an easy, efficient, and continuous reaction at room temperature. Cerium nitrate was used as a feed solution, and starch was added as a stabilizer to separate the nucleation and growth processes of the nanoparticles to prevent their aggregation. The system was powered by a high voltage of 10.0 kV (peak-to-peak) from an ac power supply. The products were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, and UV−vis spectroscopy. The results showed that when a circular capillary glass tube coil was used as the slug flow reactor, the amount of the CeO 2 nanoparticles increased compared to the case when a straight glass tube was used. The size also increased from 3.4 to 6.3 nm. The synthesis mechanism of the CeO 2 nanoparticles by gas/liquid plasma was finally elucidated.

Gas/Liquid Pulsed Discharge Plasma in a Slug Flow Reactor under Pressurized Argon for Dye Decomposition

“…The dye decomposition rates of methylene blue under different pressures are listed in Table from which it can be observed that the rates were low. According to our previous study, the concentration of reactive species generated by plasma increases with an increase in the number of electrodes. Therefore, the number of electrodes was increased to seven, including three ground electrodes and four high-voltage electrodes (Figure b).…”

“…Stable plasma was produced when uniform bubbles flowed through the electrodes at a high voltage. This system provides an easy, continuous, and environmentally friendly process and has been applied successfully for the decomposition of methyl blue and synthesis of silver nanoparticles and cerium dioxide nanoparticles . However, this system has only been applied under atmospheric pressure.…”

PVP/Highly Dispersed AgNPs Nanofibers Using Ultrasonic-Assisted Electrospinning

“…Figure 5 shows the mechanism of synthesizing starch-capped AgNPs using APDP in a slug flow system. When the gas/liquid is discharged in a pulsed plasma, chemically active substances with reducing properties are generated [ 9 ]. High-voltage electrons ionize argon molecules in a local high electric field to form argon radicals.…”

“…No organic solvent was used in the whole APDP synthesis process. Moreover, APDP is a fully controllable reaction, and low-temperature synthesis prevents chemical functional group changes in stabilizers [ 7 , 8 , 9 ]. The AgNPs were fabricated in a slug flow reactor system equipped with a non-equilibrium atmospheric-pressure plasma.…”