Jamal Qernas M. Almarashi

In this article, we investigated the impact of a two electrodes argon atmospheric pressure plasma jet with a second grounded electrode (SGE) on the basil (Ocimum basilicum) seeds germination rate. The SGE enhanced the axial electric field in the direction of the treated sample. The plasma operated with two current pulses per each halve a cycle of an applied voltage. The second plasma jet current pulsed increased from 0.7 mA to 3.6 mA and the emission of the O (777.2 nm) increased 3.85 times when the jet operated with the SGE compared to that operated without SGE. The germination rate increased by eight times at 5 min of exposure using the SGE. The SEM images proved a clear etching of the basil (O. basilicum) seed surface by plasma jet with more pronounced etching and cracks by using SGE specially at higher exposure times.

Branched microfibers of sodium dodecyl sulfate/Ag nanoparticles were synthesized using a nanosecond laser at a wavelength of 532 nm. The synthesis process was investigated at three laser intensities (0.38, 0.76, and 1.53 MW/cm²) and five exposure times (5, 15, 30, 45, and 60 min). At intensities of 0.38 and 0.76 MW/cm², with increasing the exposure time, the number of nanoparticles increases until an exposure time of 30 min. Above this, exposure saturation of the number of Ag nanoparticles takes place. A similar effect was detected for the size of nanoparticles at these laser intensities. The saturation effect begins at 5 min of exposure for a laser intensity of 1.53 MW/cm². The estimated nanoparticle size ranges from 116 to 120 nm based on the exposure time for a laser intensity of 0.38 and 0.76 MW/cm², respectively. Scanning electron microscopy images at low magnification show the branched microfiber structure, while at higher magnifications, nanoparticles of Ag covering these microfibers appear. Electron dispersion x-ray spectroscopy confirmed the presence of Ag. X-ray diffraction results for the particles deposited on a fluorine-doped tin oxide-coated glass substrate were discussed.

Simple argon atmospheric pressure cold plasma jet has been designed and characterized. The spectral and electrical characteristics of the generated plasma jet were investigated. The effects of applied voltage and flow rate on plasma jet length were studied. A sinusoidal high voltage waveform was applied to ignite the plasma jet. Two current pulses were generated per each half cycle of the positive applied voltage while one current pulse was generated in the negative halves of the voltage waveforms. The time interval between the two positive current pulses decreased with increasing the applied voltage. The emission spectra of the plasma specified that the plasma included active species of O^• and OH^•. In addition, the estimated gas temperature of the generated plasma jet was in the range of 330 K, which nominated this jet to be used to treat heat sensitive materials. The obtained results showed that the length of the plasma jet increased by increasing any of the applied voltage or the flow rate at low values, whereas the length approached steady-state values at higher applied voltages and transient from laminar to turbulent flow mode at higher flow rates. This work is highly useful for applications of the required exposure to active species, charged ions, and UV photons at low operating temperatures and applied voltages.

In this paper, the emission spectra from plasma jet-water interaction is investigated. The plasma system consists of a quartz tube which is surrounded by two copper strips separated by 14 mm, the upper stripe is connected to AC high voltage power supply and the lower is grounded. A quartz-cuvette containing the water sample is placed at 13 mm down to the tube nozzle. Emission spectra from three regions; the distance between the two electrodes (A), the distance between the grounded electrode and the sample surface (B), and through the sample (C), are investigated. The results show clear differences between the spectra emitted from the three regions. Region A emits the highest intensities for the line spectra and argon 763 nm was the maximum. As well as, O radical emission spectra were detected with the highest intensities in region B. However, new bands and lines appear in the spectra from region C, due to interaction of the jet with water, depending on the water conditions and plasma operating parameters. These results declare that plasma jet interaction with water can be used as indicator for water quality and a detector for which species play the rule in plasma sterilization too.

Summary form only given. Atmospheric pressure plasma gained a great interest from researches due to its large number of biomedical applications. The chemical active species such as O, OH and NO are considered to be the main agent in that applications. Enhancing the plasma reactive species is an essential [1]. Therefore, an investigation the effect of mixing oxygen to cold atmospheric pressure plasma jet (CAPPJ) in air is presented in this work. The CAPPJ is generated by applying AC voltage 14 kV (peak-to-peak), with frequency of 29 kHz to alumina (Al₂O₃) tube. The tube has 150 mm length with a 4 and 6 mm inner and outer diameter, respectively. Argon flow rate of 4.5 SLM is blown through the alumina tube with small value of oxygen percentage from 0 to 1.2% to form the plasma jet. The addition of oxygen to argon as operating gases enhances the generation of O-radicals and reduces production of the OH-radicals. The electric and spectroscopic characteristics of the generated plasma jet are investigated. The generated plasma jet length and mode of operation varied as a function of oxygen flow rate percentage. The plasma jet length is decreased as the oxygen mixture increases and the plasma mode transmitted from filamentary to diffused mode. As anti-microbial activity, the data indicate an optimum condition of E. coli sterilization at 0.2% of oxygen.