Gliding Arc Plasma Synthesis of MnO2 Nanorods for the Plasma-Catalytic Bleaching of Azoïc Amaranth Red Dye

Rapid synthesis of ZnO nanoparticles via gliding arc discharge: unveiling the impact of discharge time on particle properties and photocatalytic performance

Herein, we present a novel approach for the synthesis of ZnO nanoparticles (ZnO NPs) using a non-thermal plasma source generated by the gliding arc discharge-air system. The effect of discharge time on the physical and optical properties, as well as the photocatalytic performance of the as-fabricated ZnO NPs, was investigated. The characterization techniques revealed that the as-synthesized ZnO exhibit hexagonal Wurtzite structure, with a wide energy gap and peak intensities of UV-vis absorption with longer discharge times. A decrease in particle size from 29 to 25 nm was also observed with increasing discharge time, while all samples were thermally stable between 25 and 700 °C. The photocatalytic performance of the ZnO NPs was evaluated by degrading Congo Red (CR) dye with a concentration of 20 ppm under sunlight at a dose of 1 mg/mL. The as-synthesized ZnO NPs revealed exceptional photocatalytic performance by degrading ~ 97% of CR dye after irradiation for 150 min. This work presents an easy and simple method for synthesizing NPs in a short time and pave the way for other potential ideas on the application of plasma gliding arc discharge.

Enhanced polarization from flexible hierarchical MnO2 arrays on cotton cloth with excellent microwave absorption

To develop flexible microwave absorbers with strong attenuation capability has become a formidable challenge for applications of camouflage, stealth, and anti-electromagnetic pollution. Herein, a series of highly uniform cotton cloth@MnO₂ (CC@MnO₂) hierarchical structures with superior absorption performances were fabricated by simultaneously changing their intrinsic (α/δ phase) and extrinsic (2D/1D geometry) characteristics. The distinct absorption capability was dominantly contributed by the vertically grown dielectric MnO₂ 1D nanotube and conductive CC substrate, which could serve as a highly oriented backbone to ensure rapid electron transportation. Therefore, a well-designed CC@MnO₂ sample (α phase instead of the δ phase) exhibits the best absorption performance. The maximum reflection loss (RL) is -53.2 dB at 5.4 GHz and the effective bandwidth is 5.84 GHz for a thickness of only 2 mm. This unique structure exhibits polarization, conduction loss, and strong dissipation capability, which can be attributed to the high density of accumulated charges trapped at the interface, as confirmed by the electron holography analysis. Meanwhile, the MnO₂ coating does not affect the original flexibility of the CC and yields a massive interface and electronic conduction path. It is expected that CC@MnO₂ might shed a new light on the design of microwave absorbers.

Plasma-deposition of α-FeOOH particles on biochar using a gliding arc discharge in humid air: a green and sustainable route for producing oxidation catalysts

Non-thermal atmospheric plasma of the gliding arc type was used as a tool for goethite-on-biochar hybrid material preparation. Biochars were first prepared by carbonizing raffia bamboo (the leafstalk of raffia palm) pith at 300 °C (BC3), 500 °C (BC5) and 700 °C (BC7). A suspension of each biochar in Fe²⁺ aqueous solution was then exposed to a plasma discharge burning in humid air. α-FeOOH particles were thus formed and spontaneously deposited on the biochar surface. In order to investigate the effect of plasma species on the support during goethite deposition, biochars were also treated with plasma in the absence of Fe²⁺ ions and then characterized. Results revealed a substantial hydroxylation and slight N-doping of biochar after plasma treatment. The prepared composite materials were tested in oxidative degradation of nitroresorcinol. The catalytic performances were in the order Fe-BC3 < Fe-BC7 < Fe-BC5 according to the abatement efficiency and half-time values obtained for each catalyst. This study establishes that waste biomass and atmospheric air can be simultaneously valorised for green production of heterogeneous catalysts.

Non-thermal atmospheric plasma of the gliding arc type was used as a tool for goethite-on-biochar hybrid material preparation.